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# Time Travel: Is it Possible?

_AVG_
They say that Time Travel can be possible. But how?

I feel that the idea of Cosmic Strings, Black Holes and Galaxies out there can lead to Time Travel. What do you think?

Another reason why it seems that Time Travel is impossible is because if it were possible in the future, tourists would be visiting us here.
dule
hm

I don't think time travel into the past is possible. It simply isn't. There are way too much paradoxes about that.

But into the future, one BIG yes. I belive it is somehow possible to isolate one small area (system), in which time would go slower, which means that the time outside the system would go faster, ergo u would be travelling into the future.

the similar case when your speed is close to c (3x10^8m/s) (the condition is that u can stay alive at that speed), where time in your system moving at that speed is 7 times slower then the outside system.

sry for bad english lol
dray101
^^^^ I totally agree, traveling in to the past IS IMPOSSIBLE

This is because the second you did, you would change the past and therefore it would change the future. Therefore you would not be the same person you were and you would not have traveled into the past (in exactly the same time and way). It's complex and confusing but simply impossible.
The simple presence of some matter (eg. a human) changes the future by simple fact that atom's and wind etc. bounce of that matter (and other factors like heat given off) and that slight change in, lets say wind, could mean that a apple (for example) wasn't dropped of a tree and then a dog didn't eat it so the dog died from hunger etc. etc. etc.

I also agree with the time slowing but it's not really TRAVELING into the future is it?
_AVG_
What about the concept of dimensions?

In another dimension, time is 3 seconds slower, etc.

Please don't be mad at me if what I said was wrong, it's what I've heard about.
dule
 _AVG_ wrote: What about the concept of dimensions? In another dimension, time is 3 seconds slower, etc. Please don't be mad at me if what I said was wrong, it's what I've heard about.

the existance of additional dimensions as we think of it is questionable imo.

I think there are many things about this world that we cannot understand yet with the current knowledge of science and the capabilities of the human brain.

so we are only guessing here.
dray101
 dule wrote: the existance of additional dimensions as we think of it is questionable imo.

I agree, I don't believe in 'other dimensions'

 dule wrote: I think there are many things about this world that we cannot understand yet with the current knowledge of science and the capabilities of the human brain.

However, I also agree with this. But in saying that there have been many people in the past who have been able to see things that no one else could, and things that you wouldn't expect them to understand. Stuff that Albert Einstein theorized is still being marveled at today.
NAJohnson
I am a firm believer in determinism, (The philosophical doctrine that every state of affairs, including every human event, act, and decision is the inevitable consequence of antecedent states of affairs,) And so I say that IF time travel into the past were possible, anything you do in the past will have already been done in the future you , reading this post, know as "NOW".
In other words, history is unchangeable, if you go into the past and do something, that will become a part of history, and since it has "already' happened, you would be powerless to stop yourself from doing whatever it was that you did. Not powerless in the sense of "Oh, why can't I stop myself from pulling the trigger!" but powerless in the sense that you will not try to stop yourself from doing it.
It will never even be a possibility for you to succeed in doing something in your past that destroys your future, and it is also not a possibility that you will not obey yourself, therefore, You are not going to try and destroy your future. You won't even want to want to want to want to want to want to want to want to want to want to want to want to want to want to want to want to want to want to.
Bikerman
Other dimensions
This largely depends on how you define the dimensions we already know. There are 3 spatial dimensions (length, width, breadth) plus 1 temporal dimension (time). So we are already sure there are 4 dimensions.

Time travel
The paradox referred to (normally expressed as going back in time and killing your own grandfather - therefore never born - therefore cannot have time travelled) is overcome if a multiverse if hypothesised where the universe splits off when time travelling so that a completely new universe is formed in which changes are permitted.

Determinism
It's a perfectly valid and logically solid position to hold. It does not rule out time travel, though, since a multiverse can still be deterministic.
jesse
I think Time Travel is impossible. My reason is very simple. If we can go to the past, then we can change anything that had happened. This situation will break the whole logic system.
In my opinion, the similiar situation which like Time Travel is that we do not realy go to the past of the future but we have gone to another universe which is parallel to the one we stay in at present. You still can not change anything that had happened. I do not know if I have make my opinion clear.

 _AVG_ wrote: They say that Time Travel can be possible. But how? I feel that the idea of Cosmic Strings, Black Holes and Galaxies out there can lead to Time Travel. What do you think? Another reason why it seems that Time Travel is impossible is because if it were possible in the future, tourists would be visiting us here.
Osmodius
 _AVG_ wrote: Another reason why it seems that Time Travel is impossible is because if it were possible in the future, tourists would be visiting us here.

Keep in mind that if time travel were made possible in the future, the largest world superpower at the time would heavily police its usage. The public would most likely never know about it, and the time paradox caused by a tourist travelling back in time would surely be forseen
Indi
Osmodius wrote:
 _AVG_ wrote: Another reason why it seems that Time Travel is impossible is because if it were possible in the future, tourists would be visiting us here.

Keep in mind that if time travel were made possible in the future, the largest world superpower at the time would heavily police its usage. The public would most likely never know about it, and the time paradox caused by a tourist travelling back in time would surely be forseen

That does fly.

Suppose time travel was invented (and it is possible to travel back in time). Suppose that you're right, and it is heavily monitored and policed so that no tourists could come back.

How long could that last? 50 years? 100? 10,000?

You would be claiming that for the rest of time - the remainder of the existence of the universe - even though the technology exists and is known - no one is ever able to travel back? Even if humanity is extinguished (and how could that happen if someone could travel to the future, fund out about it, then go back and prevent it?), no alien researchers who wanted to find out about the civilization that was beaming all that crap out into space would go back to see?

Seems a little far-fetched to me.
greatfire
It is in theory, possible to travel through time. However, there is no possible way to go to the past. because as soon as you went back you would be altering the course of time. while you exist in that section of time, however minute, you would change something. This doesnt mean that you didn't travel through time, but no one would know it, not even you. This brings up the argument of higher dimensions.e.g. multiple timelines etc etc
Bikerman
The whole idea of time travel begs a deeper question.
Why does time travel in one direction only? Arthur Eddington (British Physicist) coined the phrase 'The Arrow of Time' to describe this phenomenon.
Nothing that I know of in the fundamental laws of physics treats time as asymmetrical (ie as only flowing in one direction). We are used to time flowing in one direction only - an egg, once broken, does not suddenly 'unbreak' - but explaining why this should be so is a very deep problem in physics.
Gagnar The Unruly
To me, it seems noteworthy that we percieve time progressing in the direction of increased entropy.
Bikerman
 Gagnar The Unruly wrote: To me, it seems noteworthy that we percieve time progressing in the direction of increased entropy.

Indeed. But this itself is problematic is it not? Theory tells us that after the BB occurred the universe was in a a state of thermal equilibrium - which, put another way, means maximum entropy. This gives us a paradox since the universe immediately after the BB was in a state of maximum entropy, so how can entropy increase over time?
Gagnar The Unruly
It seems to me that a state of maximum order would also have thermal equilibrium, because the state of every point in space is exactly the same. Wouldn't the near-infinite density of the starting universe also have near-perfect order?
Bikerman
 Gagnar The Unruly wrote: It seems to me that a state of maximum order would also have thermal equilibrium, because the state of every point in space is exactly the same. Wouldn't the near-infinite density of the starting universe also have near-perfect order?

But immediately post BB the universe consisted of a uniform mass of hot energy which eventually condensed into matter. At this point entropy would be at a maximum wouldn't it?
Indi
Entropy ≠ disorder.

i know everyone has been told for years that entropy is a measure of disorder, but it is not. In most thermodynamic systems, entropy can be modelled approximately as molecular disorder, but not all. Sometimes highly "ordered" systems have lower entropy. Consider the (physically impossible, given quantum mechanical zero-point energy) case of a gas at absolute zero, where all molecule motion has stopped, and there is no inter-molecular bond energy (the chemical potential is zero) except for one molecule that is moving near c. The structure is almost perfectly "ordered", but the entropy is near zero.

Entropy is theoretically just a measure of the number of microstates in a system. Not disorder. A larger entropy means a larger number of possible microstates (although it is a statistical measure - at any given moment of time there may only be a single microstate). As a side effect, entropy measures energy dispersal (although again, this is just a statistical average). For the totally frozen gas example above, over time the energy of that one particle will be dispersed among all the other particles (increaseing the number of potential states from 2 to many, many). When it does that, the entropy will increase as more states become available and as a byproduct the energy is more dispersed.

In the case of the universe itself, it's hard to be sure whether applying our "simple" thermodynamic models is a good idea - most especially at the extremes, like right after the big bang.
Dean_The_Great
Nope. It's not possible. Unless, of course, you consider "time-dialation" a form of time travel. But even then you'd have to speed up a huge amount (at least close to the speed of light)...

But hey, that's only if you believe Einstein....
_AVG_
Is there any vehicle or weapon that can achieve the speed of light?
Bikerman
 _AVG_ wrote: Is there any vehicle or weapon that can achieve the speed of light?

Nothing with mass can achieve the speed of light. Laser weapons would, of course, be capable of achieving the speed of light (c) since they 'fire' a beam of light, but otherwise, no.
rshanthakumar
time travel is imaginary. You may not be able to land up in different era and start altering it.

But you can 'see' it if you can catch up with the light and you are able to amplify the light rays you caught. Might become a possibility after a century or so.

today we have the technology to become invisible though the military is not releasing it out. Same way, travelling faster than light could become a possibility and you might be able to see the light ray that left earth 10 million years back! Yipppy!
Bikerman
 rshanthakumar wrote: time travel is imaginary. You may not be able to land up in different era and start altering it. But you can 'see' it if you can catch up with the light and you are able to amplify the light rays you caught. Might become a possibility after a century or so. today we have the technology to become invisible though the military is not releasing it out. Same way, travelling faster than light could become a possibility and you might be able to see the light ray that left earth 10 million years back! Yipppy!

I'm not sure what you are talking about here....Time travel is, as we have pointed out, misleading because it implies that there is a commonly agreed time in which to travel - there isn't. If you mean travelling in time with respect to earth, then this is covered in previous postings quite thoroughly.
'Catching up' with light would imply travelling faster than the light which, as has been pointed out, is not possible according to relativity.
I am not aware of any technology which makes things or people invisible and I am pretty sure that the military have no such technology - this sounds like the product of one of the more outlandish conspiracy theory websites.
Gagnar The Unruly
There is a material/object now that can make whatever is inside invisible to certain microwave wavelengths, I think.
Bikerman
 Gagnar The Unruly wrote: There is a material/object now that can make whatever is inside invisible to certain microwave wavelengths, I think.

Yes indeed, but that is hardly the same
BTW - I'm not saying that it is impossible, simply that it isn't currently out there.

http://www.rsc.org/chemistryworld/News/2006/October/19100602.asp
http://www.technologyreview.com/Nanotech/18292/
jharsika
Time travel, for observational purposes, while seeming very cool just makes absolutely no sense. There are way to many things that could go wrong, way to many paradoxes, way to many things that wouldn't work!

Someone I know though, disagrees. They have a theory that every atom has another particle which he calls a chronotron(or kronotron)[you may know this from that Futurama episode....], which has stages depending on the age of the cell. If we were able to find a way to age, or de-age this particle (reverse or move forward it's stages like fast forward and rewind), AND have a way of either cloning or completely removing whatever you are making go through time ( so that it is not in two places at once, or so that the place it is taken away from is replaced by it's clone) This is just a very basic explanation of his theory.

I'd also like to add that I hate how in time-travel stories the character goes back in time to change the past, thereby making the future 'right', thereby preventing himself from ever travelling to the past, thereby making the whole thing 'neutralized'!

Edit: Does anyone know about Stephen Hawkings theory on time-travel?
Bikerman
 jharsika wrote: Someone I know though, disagrees. They have a theory that every atom has another particle which he calls a chronotron(or kronotron)[you may know this from that Futurama episode....], which has stages depending on the age of the cell. If we were able to find a way to age, or de-age this particle (reverse or move forward it's stages like fast forward and rewind), AND have a way of either cloning or completely removing whatever you are making go through time ( so that it is not in two places at once, or so that the place it is taken away from is replaced by it's clone) This is just a very basic explanation of his theory.
LOL...I think 'theory' is not quite the right word. Fantasy, dream or hallucination perhaps?
 Quote: Edit: Does anyone know about Stephen Hawkings theory on time-travel?

Hawking doesn't have a particular theory on time travel. In fact he argues against it on the grounds (in his words) :
 Hawking wrote: “Time travel is not theoretically possible, for if it was they’d already be here telling us about it!”

Here's some links to general discussions on the issue:

Hawking Lecture on Time Travel - text lecture notes
Several discussions by physicists on the issue (video)
The Conspirator
Wasn't the chronotron invented by star trek?
Chronotron are fictional particles used in science fiction, it has no basis in real physics
_AVG_
What about another theory?

If you make the Earth rotate backwards somehow, time can go backwards?
Tumbleweed
Maybe we could create a bubble of photons that mask the fact that theres is a object with mass inside, then propel the bubble using lasers
Bikerman
 Tumbleweed wrote: Maybe we could create a bubble of photons that mask the fact that theres is a object with mass inside, then propel the bubble using lasers

No..won't work..the laser will pop the bubble and the relativity police will spot it.
rshanthakumar
Bikerman wrote:
 rshanthakumar wrote: time travel is imaginary. You may not be able to land up in different era and start altering it. But you can 'see' it if you can catch up with the light and you are able to amplify the light rays you caught. Might become a possibility after a century or so. today we have the technology to become invisible though the military is not releasing it out. Same way, travelling faster than light could become a possibility and you might be able to see the light ray that left earth 10 million years back! Yipppy!

I'm not sure what you are talking about here....Time travel is, as we have pointed out, misleading because it implies that there is a commonly agreed time in which to travel - there isn't. If you mean travelling in time with respect to earth, then this is covered in previous postings quite thoroughly.
'Catching up' with light would imply travelling faster than the light which, as has been pointed out, is not possible according to relativity.
I am not aware of any technology which makes things or people invisible and I am pretty sure that the military have no such technology - this sounds like the product of one of the more outlandish conspiracy theory websites.

Who knows, the 'theory' of relativity itself could be questioned over a period of time. Don't think it will not be. If that is not done, then travelling faster than light might be out of question. There is the gravity travel; theories do say they travel at speeds of light only. But there is more to be unravelled.

As to invisibility, it will be a surprise if the army does not have it. Today it doesn't seem to be a very difficult technology.
Bikerman
 rshanthakumar wrote: Who knows, the 'theory' of relativity itself could be questioned over a period of time. Don't think it will not be. If that is not done, then travelling faster than light might be out of question. There is the gravity travel; theories do say they travel at speeds of light only. But there is more to be unravelled. As to invisibility, it will be a surprise if the army does not have it. Today it doesn't seem to be a very difficult technology.

You are obviously way too advanced for my level - I thought invisibility seemed to be a very difficult technology; and you seem to have some inside track on relativity that I'm unaware of.
Teal'c36
its not really that timetravel into the past is impossible it is probably more likely that large masses cannot travel back in time.

I read somewhere that someone was creating a light tunnel that could send radio waves back in time. Of course they could only travel back as far as when the machine was first turned on but if left on for 100 years you could get signals from 100 years from now when it is turned on.

as for altering the time line if you were to travel back in time this wouldn't happen instead you would create a split at the point you travel too. IE an alternate universe.

IE it may be possible that in our future we travel back in time but our time line doesn't contain anyone who did (or if someone did travel to our time line we called them insane and sent them into an asylum) So if we ever travel back in time we will visit a SIMILAR but alternate universe. (thereby avoiding a paradox by both events happening you travel back in time and you never travel back in time)
Indi
 Teal'c36 wrote: its not really that timetravel into the past is impossible it is probably more likely that large masses cannot travel back in time. I read somewhere that someone was creating a light tunnel that could send radio waves back in time. Of course they could only travel back as far as when the machine was first turned on but if left on for 100 years you could get signals from 100 years from now when it is turned on.

Not quite, shol'va! (heh, sorry - i couldn't help myself)

There is a theorem in quantum mechanics called the "no-communication theorem" that disallows what you suggest with respect to sending information into the past (massless information, of course).

So no, if quantum mechanics is "right", there can be no radio to the past.
Tumbleweed
Bikerman wrote:
 Tumbleweed wrote: Maybe we could create a bubble of photons that mask the fact that theres is a object with mass inside, then propel the bubble using lasers

No..won't work..the laser will pop the bubble and the relativity police will spot it.

Rather than shoot lasers at the bubble I was thinking more on the lines of using light to change the frequency of light and riding a nice exotic type of electromagnetic energy, but maybe that popping is indeed an energy that could be used.
Do the relativity police believe in a doughnut shop shaped universe ?
Bikerman
 Tumbleweed wrote: Rather than shoot lasers at the bubble I was thinking more on the lines of using light to change the frequency of light and riding a nice exotic type of electromagnetic energy, but maybe that popping is indeed an energy that could be used. Do the relativity police believe in a doughnut shop shaped universe ?

Nononono....the relativity police are not based in the US, they are based at the centre of the Universe - England. They know that the universe is shaped like a cup of tea.
Bikerman
To get back to the subject in hand, though, I think one point that needs clarifying is the nature of time since the whole notion of time travel in this thread seems based on an assumption that time 'flows'.

According to relativity this is not so. If you think about things from the point of view of special relativity then time, being relative, does not flow. There is no 'objective' time. The only thing that exists in reality is spacetime. That means that whatever you were doing in, say, 1999 at a particular moment still exists as a point in spacetime. More confusingly, whatever you will be doing in, say, 2010, also exists as a point in spacetime.

Relativity imposes the limit that no information can travel faster than light, so there is no way to connect the 2010 point in spacetime directly to the present point in spacetime, but both exist as separate points in the totality of spacetime and the notion that time 'flows' in a stream is an illusion.
Teal'c36
nice point of course i need to show you that things can travel faster then light (it was an interesting article but i'm not entirely sure it was true)

according to the article a scientist sped up light so it reached its destination before it left. It was also interesting because the light the flowed back down the wire. So it may be possible to send things back in time by exceeding the speed of light but doing that would require a large amount of energy for a human(when i say large imagine all the energy in the sun and you have about how much it would take).

Unique link about sound exceeding the speed of light

http://www.livescience.com/technology/070112_ftl_sound.html

and the article about light exceeding its own speed.
http://www.cbc.ca/health/story/2000/07/20/speedlight000720.html
Bikerman
 Teal'c36 wrote: nice point of course i need to show you that things can travel faster then light (it was an interesting article but i'm not entirely sure it was true).according to the article a scientist sped up light so it reached its destination before it left.

This has been dealt with comprehensively in other threads. The light did not reach it's destination before it left...you need to read the article more carefully. Neither is this an example of faster than light travel - again you need to read the article. This phenomena uses 'group' velocity or, in other cases, phase velocity as a measure. The following animation demonstrates the difference between phase velocity and particle velocity.

Note that the 'wave' appears to travel faster than the particle.
 Quote: It was also interesting because the light the flowed back down the wire. So it may be possible to send things back in time by exceeding the speed of light but doing that would require a large amount of energy for a human(when i say large imagine all the energy in the sun and you have about how much it would take).

And just how do you arrive at that conclusion? Photons are massless, humans are not. What calculation do you use to state that the energy required would be equal to that 'in the sun'?

http://en.wikipedia.org/wiki/Speed_of_light
http://www.mathpages.com/home/kmath210/kmath210.htm
Teal'c36
the energy required was a guess (i'll admit a bad one)

 Quote: It raced so fast the pulse exited a specially-prepared chamber before it even finished entering it.

the idea that time travel occured with the light is confirmed in the article with the quote above.
Indi
Bikerman wrote:
 Teal'c36 wrote: nice point of course i need to show you that things can travel faster then light (it was an interesting article but i'm not entirely sure it was true).according to the article a scientist sped up light so it reached its destination before it left.

This has been dealt with comprehensively in other threads. The light did not reach it's destination before it left...you need to read the article more carefully. Neither is this an example of faster than light travel - again you need to read the article. This phenomena uses 'group' velocity or, in other cases, phase velocity as a measure. The following animation demonstrates the difference between phase velocity and particle velocity.

Note that the 'wave' appears to travel faster than the particle.

Actually, in this case i'd say it's not actually Teal'c's fault. When i read those articles when they were originally posted, they confused me. i knew they were wrong, but i couldn't figure out how. i even talked to a full professor at my university that teaches quantum mechanics and nanotech classes, and he was scratching his head. it wasn't until we actually went back to the original published articles - the peer-reviewed articles published by the scientists (specifically Haché and Poirier), not the versions floating around Reuters or whatever written by science reporters - that we figured out what was going on.

 Teal'c36 wrote: the idea that time travel occured with the light is confirmed in the article with the quote above.

i'm afraid you have been misled by a poorly written article. Nothing in the article is technically wrong, it's just that they don't add all the right details for it to make sense.

Sometimes they specifically - and correctly - identify the "speed of light" as either group velocity or phase velocity... but most of the time they don't. They just say "speed of light". Sometimes the "speed of light" they're talking about is the group velocity, sometimes it's the phase velocity and sometimes it's even the signal velocity (the speed at which information can be transmitted). The problem is that you can't tell when they mean each one! You have to go back to the original scholarly papers to untangle it... but of course, that's not exactly light reading.

Once you do figure it out, though, what those experiments have shown (and there are a couple of them), is that we can deform photon packets almost at will. Something similar happens when you get a get a photon to "quantum tunnel" through a potential barrier. Depending on which "speed of light" you're talking about, yes, you can get "speeds" of well over c. i've heard measurements of up to 3c. But that is the group velocity, not the signal velocity. No matter what form the wave packet takes - which may be severely distorted by resonance, and may have a group velocity well above c (phase velocities are usually above c) - the signal velocity will never be greater than c.

So no, those articles do not confirm any FTL or time travelling. They only sound like it because they're not written precisely enough. The original papers written by the scientists make no bones about the fact that no FTL or causality violation occurs, and general relativity holds.
Teal'c36
oppss i guess it is my mistake. Kinda hard to read the orignal articles tho when sites that post about it don't link to the original articles (and im lazy so i don't feel like searching for something i think i already understand)

oh well. I wonder if i can find the light tunnel for time travel... that would be an interesting one to get comments on.

http://www.youtube.com/watch?v=EWnoMaSgYPY

the best link i could find the original video was removed from Google.
Tumbleweed
Bikerman wrote:
 Tumbleweed wrote: Rather than shoot lasers at the bubble I was thinking more on the lines of using light to change the frequency of light and riding a nice exotic type of electromagnetic energy, but maybe that popping is indeed an energy that could be used. Do the relativity police believe in a doughnut shop shaped universe ?

Nononono....the relativity police are not based in the US, they are based at the centre of the Universe - England. They know that the universe is shaped like a cup of tea.

.... cup of tea ... *goes off and makes one*

Maybe I am reading your back to the point post wrong , but it sounds a bit like your saying the universe has a predefined path
 Bikerman wrote: To get back to the subject in hand, though, I think one point that needs clarifying is the nature of time since the whole notion of time travel in this thread seems based on an assumption that time 'flows'. According to relativity this is not so. If you think about things from the point of view of special relativity then time, being relative, does not flow. There is no 'objective' time. The only thing that exists in reality is spacetime. That means that whatever you were doing in, say, 1999 at a particular moment still exists as a point in spacetime. More confusingly, whatever you will be doing in, say, 2010, also exists as a point in spacetime. Relativity imposes the limit that no information can travel faster than light, so there is no way to connect the 2010 point in spacetime directly to the present point in spacetime, but both exist as separate points in the totality of spacetime and the notion that time 'flows' in a stream is an illusion.

Somewhere theres an ifinate number of points of time past and future and I exist there ?
Indi
 Teal'c36 wrote: oppss i guess it is my mistake. Kinda hard to read the orignal articles tho when sites that post about it don't link to the original articles (and im lazy so i don't feel like searching for something i think i already understand)

Nope, actually, it's not your mistake. And if it is, well it fooled the hell out of just about everyone else i know - including fully-tenured particle physics professors - so you're in good company (one guy wondered if it was a really clever April Fools day joke or something of the sort). It really is a case of the article being so poorly written that it can be interpreted several different ways - depending on how you interpret "speed of light" in each instance it appears.

To be honest, i'm not even sure if you can read the actual source material. The reason i could is because i knew someone that has a subcription that allowed them access. The article i read is here, and in the brief abstract it doesn't say anything revealing:
 Quote: We study the propagation of brief electric pulses along a coaxial line having a spatially periodic impedance. The periodicity causes anomalous dispersion and the appearance of a stop band in transmission near 10 MHz. Group velocities of up to three times the speed of light are observed in that spectral region, in accordance with calculations based on an effective index theory.
But i can tell you this, if it so happened that someone mannaged superluminal communication (or laid a practical ground work for it), the abstract would say a whole hell of a lot more than "Group velocities of up to three times the speed of light are observed..., in accordance with... theory."

Other than that, i can't really offer any proof to back up my claims that this does not constitute FTL transmission, sorry.
Bikerman
 Tumbleweed wrote: Maybe I am reading your back to the point post wrong , but it sounds a bit like your saying the universe has a predefined path

Predefined is too strong a word. I'll explain at the end.
 Quote: Somewhere theres an ifinate number of points of time past and future and I exist there ?

Sort of.
Let me try to explain with an example.
Imagine I was on a planet several billion light years away from Earth.
Your concept of 'now' would include everything you can see around you and that would include me on my planet. However, if you then move towards my planet (even at a relatively small velocity - say in a car) then the effects of special relativity mean that your 'now' would include events way into my future since time dilation would be 'magnified' by the distance between us.
(The formula would be v*x/c^2 (v would be your velocity, c the speed of light and x the distance between us). Therefore the events way into my future must already exist in spacetime from your perspective.
That does NOT mean, however, that the events are 'predetermined' in any sense that is meaningful since relativity also imposes the limit that no information can travel faster than light. In fact the light would take several billion years to reach you from my planet.
The idea of points already existing in spacetime is valid only from an imaginary point of view outside spacetime but the example serves to show that in any real sense time cannot be said to flow.
Bikerman
 Indi wrote: Nope, actually, it's not your mistake. And if it is, well it fooled the hell out of just about everyone else i know - including fully-tenured particle physics professors - so you're in good company (one guy wondered if it was a really clever April Fools day joke or something of the sort). It really is a case of the article being so poorly written that it can be interpreted several different ways - depending on how you interpret "speed of light" in each instance it appears.

Just to back up what Indi is saying here.....having read the article more carefully they did indeed use the words 'group velocity' which would imply superluminal transmission. I have to agree that this was not your fault and that you didn't misread the article.

I also agree with Indi, however, that if they *had* achieved superluminal transmission then we would be hearing a lot more about it.
 Quote: It raced so fast the pulse exited a specially-prepared chamber before it even finished entering it.

All this says is that the pulse was deformed so that the beginning of the wave was reflected back before the end of the wave had entered...not the same as FTL..
Tumbleweed
Bikerman wrote:
 Tumbleweed wrote: Maybe I am reading your back to the point post wrong , but it sounds a bit like your saying the universe has a predefined path

Predefined is too strong a word. I'll explain at the end.
 Quote: Somewhere theres an ifinate number of points of time past and future and I exist there ?

Sort of.
Let me try to explain with an example.
Imagine I was on a planet several billion light years away from Earth.
Your concept of 'now' would include everything you can see around you and that would include me on my planet. However, if you then move towards my planet (even at a relatively small velocity - say in a car) then the effects of special relativity mean that your 'now' would include events way into my future since time dilation would be 'magnified' by the distance between us.
(The formula would be v*x/c^2 (v would be your velocity, c the speed of light and x the distance between us). Therefore the events way into my future must already exist in spacetime from your perspective.
That does NOT mean, however, that the events are 'predetermined' in any sense that is meaningful since relativity also imposes the limit that no information can travel faster than light. In fact the light would take several billion years to reach you from my planet.
The idea of points already existing in spacetime is valid only from an imaginary point of view outside spacetime but the example serves to show that in any real sense time cannot be said to flow.

My initial thought was on .....

 Bikerman wrote: That means that whatever you were doing in, say, 1999 at a particular moment still exists as a point in spacetime. More confusingly, whatever you will be doing in, say, 2010, also exists as a point in spacetime.

I am not sure using the perspective of a far distant someone helps explain what happens to a single person .... not that it dos'nt , just it dos'nt to me
Bikerman
 Tumbleweed wrote: I am not sure using the perspective of a far distant someone helps explain what happens to a single person .... not that it dos'nt , just it dos'nt to me

Fair enough....try another way of looking at it.
What is 'now'? For you, now is what you see around you. That includes the sun, stars, next door house, etc. All of these are in different spacetime frames in reality. The moon Sun is as it was over a minute ago, the moon over a second and next door a minute fraction of a second. All of this is 'now' to you.
Now imagine moving fast....a good percentage of c. Suddenly your 'now' is different. Which 'now' is the real 'now'?
Answer? There is no 'real' now.
Tumbleweed
Bikerman wrote:
 Tumbleweed wrote: I am not sure using the perspective of a far distant someone helps explain what happens to a single person .... not that it dos'nt , just it dos'nt to me

Fair enough....try another way of looking at it.
What is 'now'? For you, now is what you see around you. That includes the sun, stars, next door house, etc. All of these are in different spacetime frames in reality. The moon Sun is as it was over a minute ago, the moon over a second and next door a minute fraction of a second. All of this is 'now' to you.
Now imagine moving fast....a good percentage of c. Suddenly your 'now' is different. Which 'now' is the real 'now'?
Answer? There is no 'real' now.

We can view the past as explained above, and we exist in the present even if it is subjective , none of this explains how I exist now and in the future at the same time unless we want to include a reflection/echo as the real thing, saying light takes time to travel so all things are essentially in the past is different from saying you exist in the past, present and future at the same time
Bikerman
 Tumbleweed wrote: We can view the past as explained above, and we exist in the present even if it is subjective , none of this explains how I exist now and in the future at the same time unless we want to include a reflection/echo as the real thing, saying light takes time to travel so all things are essentially in the past is different from saying you exist in the past, present and future at the same time

No, not at the same time, but as points in spacetime. My point is that there is no 'flow' of time.
If you accept that reality is what you perceive at a particular moment and you also accept that your 'now' is no more valid than the 'now' of someone at a great distance or travelling at a great speed, then it follows that reality must consist of all events in all of spacetime.
soulman
everything is possible, years ago people think flying is ridiculous, maybe now we think time traveling look like a fiction, but I think one day we will do that.
leirbag
In situations like this there is only one thing to fall back on.... Stick to what your religion or faith says about it that way u dont err spirituallyand question ur faith.
Bikerman
 leirbag wrote: In situations like this there is only one thing to fall back on.... Stick to what your religion or faith says about it that way u dont err spirituallyand question ur faith.

In situations like this you should 'fall back' on what the science says. 'Erring spiritually' is not a consideration, unless you are a fundamentalist and, in any case, such discussion belongs elsewhere.
Tumbleweed
Bikerman wrote:
 Tumbleweed wrote: We can view the past as explained above, and we exist in the present even if it is subjective , none of this explains how I exist now and in the future at the same time unless we want to include a reflection/echo as the real thing, saying light takes time to travel so all things are essentially in the past is different from saying you exist in the past, present and future at the same time

No, not at the same time, but as points in spacetime. My point is that there is no 'flow' of time.
If you accept that reality is what you perceive at a particular moment and you also accept that your 'now' is no more valid than the 'now' of someone at a great distance or travelling at a great speed, then it follows that reality must consist of all events in all of spacetime.

If the future exists in such a sense as a point in timespace ,thats is in essence eternal , as we are 'sort of' not there then can we assume that nothing is 'sort of' not there , you dont need a lot of spacetime to hold nothing , the point in spacetime should be said to be an empty vessel rather than all possible outcomes, one empty vessel can hold any event is much more simple that all events are there allready and actions choose one
If time does not flow ... do we flow through time ? if we do then would there be a real difference in the effect time has on us ?
Bikerman
 Tumbleweed wrote: If the future exists in such a sense as a point in timespace ,thats is in essence eternal , as we are 'sort of' not there then can we assume that nothing is 'sort of' not there , you dont need a lot of spacetime to hold nothing , the point in spacetime should be said to be an empty vessel rather than all possible outcomes, one empty vessel can hold any event is much more simple that all events are there allready and actions choose one If time does not flow ... do we flow through time ? if we do then would there be a real difference in the effect time has on us ?

This is where it gets interesting and complex. My understanding is that spacetime events simply 'are' (in the sense that they are not empty, and neither do they hold all possible outcomes). Now obviously this immediately implies pre-determinism or predestination since I am saying that all future events a fixed realities as well as past events, but I am anxious to avoid that debate here, because it implies consequences which i think are beyond the scope of science.

The question of whether we flow through time or time flows around us is, again, a difficult one. My answer, based on my understanding of relativity, would be neither. Our consciousness makes it appear that time progresses in a flow from past, through present and towards future. There is, however, nothing that I can find in physics that would support this view. The 'flow' seems to arise from our own consciousness of changes in our thoughts and perceptions rather than from any physical 'law'.
JIM2003
I saw a show on tv that said that its IMPOSSIBLE to go forward into time, but possible to back into time, as far back as when the first time machine was created. So if anyone does ever create a time machine, we would know immediately because somethine or someone would appear out of thin air.
Bikerman
 JIM2003 wrote: I saw a show on tv that said that its IMPOSSIBLE to go forward into time, but possible to back into time, as far back as when the first time machine was created. So if anyone does ever create a time machine, we would know immediately because somethine or someone would appear out of thin air.

Don't believe everything you see on TV
Bikerman
 Indi wrote: In the case of the universe itself, it's hard to be sure whether applying our "simple" thermodynamic models is a good idea - most especially at the extremes, like right after the big bang.

I've been reading and pondering on this and would like to return to it.
We know from the models that soon after the BB (minutes) there was a very uniform distribution of 'primordial plasma' consisting mainly of hydrogen ions (protons) and helium nuclei in a sea of photons.

I previously assumed that this represented a state of high entropy but I now realise where my mistake was - I forgot gravity. Gravity would naturally tend to pull the early universe into 'clumps'. This means that the actual entropy of the early universe must have been very low since it stayed relatively evenly diffused, when the probability was for it to clump together via gravitational attraction.
This explains things - I was having real difficulty working out how entropy could have started so high and then decreased massively before rising again. Mathematically there doesn't seem to be any reason that I can find to rule out entropy increasing both into the future and into the past; but obviously this would seem to contradict both 2nd law and everyday experience. Smashed eggs don't normally un-smash, for example.
I think I can now see how it fits together.....[/i]
Gagnar The Unruly
Sometimes I wonder if the whole "direction of time" thing isn't quite as cosmic as we tend to believe. It seems sort of ridiculous to say that the universe "percieves" time as going in a certain direction.

Maybe the way we percieve time has more to do with the way we are made as humans. Our neurons can only fire in one direction. We accumulate information based on our interactions with the environment, which stimulate neural transmissions that reach our brain and get sorted into experiences and memories for recall at a later date. It's hard for me to imagine an organism that started off knowing everything, and then subsequently lost all it's knowledge as events spontaneously sucked it's memories away. Maybe human awareness exists as a tape in spacetime, but our biology makes it such that the universe only makes sense when you play the tape one direction.

People look funny when you play them backwards on video, but maybe the processes that form our consciousness wouldn't make sense at all if we were played backwards. I think our consciousness and perception of time may be an emergent property of the way our brains work. Obviously, thermodynamics play a role in thought processes, hence our perception of time lines up with an increase in entropy.
Tumbleweed
Bikerman wrote:
 Tumbleweed wrote: If the future exists in such a sense as a point in timespace ,thats is in essence eternal , as we are 'sort of' not there then can we assume that nothing is 'sort of' not there , you dont need a lot of spacetime to hold nothing , the point in spacetime should be said to be an empty vessel rather than all possible outcomes, one empty vessel can hold any event is much more simple that all events are there allready and actions choose one

If time does not flow ... do we flow through time ? if we do then would there be a real difference in the effect time has on us ?

 Bikerman wrote: This is where it gets interesting and complex. My understanding is that spacetime events simply 'are' (in the sense that they are not empty, and neither do they hold all possible outcomes). Now obviously this immediately implies pre-determinism or predestination since I am saying that all future events a fixed realities as well as past events, but I am anxious to avoid that debate here, because it implies consequences which i think are beyond the scope of science.

I dont think anything physical or spiritual is beyond science given....Erm....time , but will agree that some things are as of yet beyond our collective perceptions

 Bikerman wrote: The question of whether we flow through time or time flows around us is, again, a difficult one. My answer, based on my understanding of relativity, would be neither. Our consciousness makes it appear that time progresses in a flow from past, through present and towards future. There is, however, nothing that I can find in physics that would support this view. The 'flow' seems to arise from our own consciousness of changes in our thoughts and perceptions rather than from any physical 'law'.

You now have me thinking the universe is onion shaped ,maybe with the core on the outerside and wondering how bright the BB actually was
starfish2007
and who's to say that people havenot allready travaled back in time what are all these ufo siteings about? I meempeople have bin saying its aliens for years but whatif its reallypeople from the future? its thenaliens more klikelly that then aliens. I meenif the aliens were out there and that avenced what would they want witha planiet so out dated by there standereds but a hummen for our same planniet would bemore intrested in travaling back in time
Bikerman
 starfish2007 wrote: and who's to say that people havenot allready travaled back in time what are all these ufo siteings about? I meempeople have bin saying its aliens for years but whatif its reallypeople from the future? its thenaliens more klikelly that then aliens. I meenif the aliens were out there and that avenced what would they want witha planiet so out dated by there standereds but a hummen for our same planniet would bemore intrested in travaling back in time

Why would people from the future choose to come here in 'flying saucers'. Surely they wouldn't need to come in some spaceship if they travelling in time but not in space?
Or is there a more scientific point being made here?
Are you suggesting that time travel would be to the same point occupied in space at the point of departure? This would, as is obvious, be a different point in space to the destination - therefore anyone travelling from a future earth in time, but not in space, would appear (most likely) in outer space. If that is the point then it is an interesting one.
Gagnar The Unruly
 Bikerman wrote: Are you suggesting that time travel would be to the same point occupied in space at the point of departure? This would, as is obvious, be a different point in space to the destination - therefore anyone travelling from a future earth in time, but not in space, would appear (most likely) in outer space. If that is the point then it is an interesting one.

But since inertial coordinate systems are relative, what does it mean to say that a time-jumper stays in the "same" spot. That spot is different according to different inertial reference frames.
Bikerman
Gagnar The Unruly wrote:
 Bikerman wrote: Are you suggesting that time travel would be to the same point occupied in space at the point of departure? This would, as is obvious, be a different point in space to the destination - therefore anyone travelling from a future earth in time, but not in space, would appear (most likely) in outer space. If that is the point then it is an interesting one.

But since inertial coordinate systems are relative, what does it mean to say that a time-jumper stays in the "same" spot. That spot is different according to different inertial reference frames.

I agree, but I was trying to put the best interpretation I could on the post which I otherwise found vacuous. I thought that raising GR at that point may have been too confusing to the poster and wanted to give them chance to come back first. That said, your point is, as I understand things, valid and the correct answer to the extended point.

(post edited to correct spelling mistake)
Gagnar The Unruly
Oops, I didn't mean to steal your thunder
Bikerman
 Gagnar The Unruly wrote: Oops, I didn't mean to steal your thunder

Not a problem - I only cast thunderbolts when someone steals my hammer:-)
rshanthakumar
This may be really lunatic any way read on please.

1. time travel is fiction. let us get it straight because time is like your attitude. It is never the same again.

2. Even if repeated time can never be repeated. Therefore, what occurs as time once is done and past. It will never ever reappear again.

3. Time is a dimension that is independent of all the other three dimensions that we know of and so comfortable with. As a matter of fact, the relationship between them is non existent.

4. Time does not stay still even in a black hole (?) Does it? the spatial dimensions might
Bikerman
 rshanthakumar wrote: This may be really lunatic any way read on please. 3. Time is a dimension that is independent of all the other three dimensions that we know of and so comfortable with. As a matter of fact, the relationship between them is non existent.

No...time and space are intertwined into a single whole which we call spacetime.
 Quote: 4. Time does not stay still even in a black hole (?) Does it? the spatial dimensions might

Actually it does. Time is relative so you can only talk about it from the point of view (POV) of an observer. Something disappearing into a black hole would appear to an observer to stop due to the effects of time dilation.
rshanthakumar
There are too many factors that make up time.

You cannot possibly travel down in any axis up to the point zero and then travel beyond zero into the negative. If you assume the zero at position one, then you might do it in case of spatial dimensions. But might not be possible in the case of time.

The factors that affect an instant of time are innumerable. It is not just x, y and z. There are other dimensions to it which need to also roll back in time. It is not a question of just moving. It is a question of pulling to gether material of various combinations, gravitational, EM rays and many others have to roll back.

At any given point in time (every microsecond) millions of millions of N of energy is being sent out by stars and how do you roll them back. And this energy gets converted into various forms too. Roll back is a myth. Roll forward is also a myth because of the same reason.
rshanthakumar
Bikerman wrote:
 rshanthakumar wrote: This may be really lunatic any way read on please. 3. Time is a dimension that is independent of all the other three dimensions that we know of and so comfortable with. As a matter of fact, the relationship between them is non existent.

No...time and space are intertwined into a single whole which we call spacetime.
 Quote: 4. Time does not stay still even in a black hole (?) Does it? the spatial dimensions might

Actually it does. Time is relative so you can only talk about it from the point of view (POV) of an observer. Something disappearing into a black hole would appear to an observer to stop due to the effects of time dilation.

I think you have hit the bull's eye! It 'appears' to stay still. But it doesn't. Time keeps moving whether you are on a space ship moving at the speed of light or not. Time is moving. When you say you are speeding at the speed of light, the speed is a measure of time, isn't it?

Isn't space-time continuum independent of observer, by the by?
Bikerman
 rshanthakumar wrote: I think you have hit the bull's eye! It 'appears' to stay still. But it doesn't. Time keeps moving whether you are on a space ship moving at the speed of light or not. Time is moving. When you say you are speeding at the speed of light, the speed is a measure of time, isn't it?

No...it's a bit more complicated than that. Everyone has their own time. The faster you move the slower your time appears to someone moving slower. Something travelling at the speed of light has no time.
 Quote: Isn't space-time continuum independent of observer, by the by?

To a certain extent yes but any observer will alter spacetime just by being there since they have mass which distorts local spacetime.
heridlia
Maybe time travel is impossible.

If 'time travel' available, of course that there is humans from the future is travelling to our time!

But, in fact any human like this?

None.

Thanks a lot.
Teal'c36
You claim that if time travel were possible we would be seeing people from the future not true.

If i sit here and burn my house down do you know i did? of course not unless you see it on the news or via another source of information.

If i were to claim i was from the future would you believe me? of course not since we believe time travel to be impossible if not consciously then subconsciously(most of us anyway). So you would call me crazy and throw me in the asylum and put me on a bunch a meds.

As for knowing of anyone like this it has been said that a man has travel from the year 2025 (i think) of course it was an internet thing and the people he talked to had never met him and never saw him again (he isn't making posts anymore either). Do we believe his story? no why? because it seems like a joke and if we mark this as a joke then we can just as easily call the next one a joke even if the next one is the real thing. (kinda why you shouldn't cry wolf if there isn't one)
boristse
time travel...i think it should be impossible
it only show in comics or a faction thing
cornga56
Could anyone agree with me that whatever truths we've found so far could be radically changed with the next discovery?

If you can agree with that, then could you agree that most of what we know about quantum physics/mechanics and particle theory is flawed?

Now I'll delve a tiny bit into philosophy, just bear with me.

What's first ten digits of pi? If the answer given contains all the right numbers correctly except for the last 3, is the answer not wrong? Another random question, if I ask for someone to recall the events of let's say the War of 1812, and they recap some of the events correctly but not all of them, could you say that the answer is wrong? My point is the answers are not wrong but they're not right.

So I think the same could be applied here to Time travel and questions of physics.

I think it's important for everyone to remember that nothing we know is solid, so no one should say one theory is wrong over another, especially your own.

No one is right here cuz we have part of the answer, but not the whole answer, so obviously certain aspects or theories won't fit in with the bigger picture, ESPECIALLY if we don't even know how big the picture is or what the dimensions are. I'm just trying to moderate a little cuz I always see people on here bashing other people's opinions, but seriously no matter how much you surf the net and do research you're not going to be completely right and you should be accepting of other's theories especially if they don't fit in with yours because yours may definitely be wrong.

Time travel is a touchy subject in the physics community.

Generally you're either part of the community that believes that time travel is possible or you're part of the community that believe it isn't possible.

From there you can create countless subdivisions based on theories, so remember what side you're on and that you're all fighting for the same thing no matter what side you're on. Keep working together, that's the only way we'll find the complete answer!
Bikerman
 cornga56 wrote: Could anyone agree with me that whatever truths we've found so far could be radically changed with the next discovery?
Yes
 Quote: If you can agree with that, then could you agree that most of what we know about quantum physics/mechanics and particle theory is flawed?
No
 Quote: Now I'll delve a tiny bit into philosophy, just bear with me.
OK
 Quote: What's first ten digits of pi?
3.141592653
 Quote: If the answer given contains all the right numbers correctly except for the last 3, is the answer not wrong?
Yes because the question asked for the first 10 digits and the answer did not supply them correctly
 Quote: Another random question, if I ask for someone to recall the events of let's say the War of 1812, and they recap some of the events correctly but not all of them, could you say that the answer is wrong? My point is the answers are not wrong but they're not right.
The point is that the answers are not complete, not that they are right or wrong.
 Quote: So I think the same could be applied here to Time travel and questions of physics. I think it's important for everyone to remember that nothing we know is solid, so no one should say one theory is wrong over another, especially your own.
Yes they should. I suggest you do some reading on science. If you have a theory that says pi = 4 then I say you are wrong.
 Quote: No one is right here cuz we have part of the answer, but not the whole answer, so obviously certain aspects or theories won't fit in with the bigger picture, ESPECIALLY if we don't even know how big the picture is or what the dimensions are. I'm just trying to moderate a little cuz I always see people on here bashing other people's opinions, but seriously no matter how much you surf the net and do research you're not going to be completely right and you should be accepting of other's theories especially if they don't fit in with yours because yours may definitely be wrong.
Science takes as a given the fact that theory may be shown wrong. That does not mean that all theories are equally valid.
 Quote: Time travel is a touchy subject in the physics community.
Is it? I thought it was freely discussed.
 Quote: Generally you're either part of the community that believes that time travel is possible or you're part of the community that believe it isn't possible.
The majority of scientists are part of a different community - the one that doesn't know if it is or is not possible.
xanarulz
I don't believe time travel is possible, if this was so, people would be traveling to our time! In addition you would have to be traveling faster than light, and according to Einstein, the closer you get to the speed of light time goes slower around you. Ex. If you were traveling the Speed of Light, a few days could be 50 years or so in "Real Time". But this opens up the theory that it is possible to travel into the future, but not in the past?
Bikerman
 xanarulz wrote: I don't believe time travel is possible, if this was so, people would be traveling to our time! In addition you would have to be traveling faster than light, and according to Einstein, the closer you get to the speed of light time goes slower around you. Ex. If you were traveling the Speed of Light, a few days could be 50 years or so in "Real Time". But this opens up the theory that it is possible to travel into the future, but not in the past?

Close but not quite. According to relativity (Einstein) there is NO real time. Everyone has their own time and nobodies time is better or more important than anyone else's time. There is no central 'clock' by which we can all agree what time it is.
You are right about time slowing down (as observed by someone not travelling as fast). If I were moving close to the speed of light (c) relative to you, then you would see your watch ticking normally and (if you could) you would see my watch ticking very slowly. I would see my watch ticking normally and would see your watch moving very slowly. At the speed of light time would stop.
Tumbleweed
Bikerman wrote:
 xanarulz wrote: I don't believe time travel is possible, if this was so, people would be traveling to our time! In addition you would have to be traveling faster than light, and according to Einstein, the closer you get to the speed of light time goes slower around you. Ex. If you were traveling the Speed of Light, a few days could be 50 years or so in "Real Time". But this opens up the theory that it is possible to travel into the future, but not in the past?

Close but not quite. According to relativity (Einstein) there is NO real time. Everyone has their own time and nobodies time is better or more important than anyone else's time. There is no central 'clock' by which we can all agree what time it is.
You are right about time slowing down (as observed by someone not travelling as fast). If I were moving close to the speed of light (c) relative to you, then you would see your watch ticking normally and (if you could) you would see my watch ticking very slowly. I would see my watch ticking normally and would see your watch moving very slowly. At the speed of light time would stop.

There must be one real time .... your own ..... or do you mean theres no 'objective' time ?
dwinton
 _AVG_ wrote: They say that Time Travel can be possible. But how? I feel that the idea of Cosmic Strings, Black Holes and Galaxies out there can lead to Time Travel. What do you think? Another reason why it seems that Time Travel is impossible is because if it were possible in the future, tourists would be visiting us here.

You are mistaken. Suppose for example people in the future can travel back in time, but inaccurately. What if, in traveling back in time they create another universe to resolve the causality problem that would otherwise arise?

Another assumption is that time travel means sending a person through time. Perhaps under those restrictions it is impossible. However, consider a particle of light. Apparently there is a way you shoot a photon through something and it comes out the other end before it enters.

Light is very weird in many ways. I guess it is weird because it is a virtual particle. If you have no mass why should the laws of physics apply to you? But that is something else I have always wondered about: if E=mc2 and a photon has energy then you can solve for mass. If you take mass to be 0 then what makes the light move? I could understand not needing energy while light is traveling through a vacuum, but light particles can give atoms energy or they can be released by powered up atoms. For them to give energy they must have some (conservation of energy) and to be shot out of the atom, they must be acted upon by some force.
Bikerman
 Tumbleweed wrote: There must be one real time .... your own ..... or do you mean theres no 'objective' time ?

There is no 'real' time in the sense of a reference time (or, yes, objective time). We generally avoid words like real so I was sloppy in using it there, but one must be careful not to assume anything special about one's own time...it is only 'real' to that person, as everyone's time is real to them. Time is relative is the normal way of expressing it. Previously Newtonian physics held that time was absolute but speed was relative. Special Relativity made time relative as well as speed.
Bikerman
 dwinton wrote: You are mistaken. Suppose for example people in the future can travel back in time, but inaccurately. What if, in traveling back in time they create another universe to resolve the causality problem that would otherwise arise?
Why inaccurately?
 Quote: Another assumption is that time travel means sending a person through time. Perhaps under those restrictions it is impossible. However, consider a particle of light. Apparently there is a way you shoot a photon through something and it comes out the other end before it enters.
Ahh....this again.

 Quote: The absorption or gain (green), index of refraction (blue) and time delay (red) for optical propagation, all as a function of optical frequency (x-axis). In (a) there are two frequencies at which absorption occurs. Although the index of refraction is close to 1 everywhere, it varies rapidly near these absorption regions. For this reason, light travels increasingly slowly as its frequency approaches the frequency of either of the absorption lines ("normal dispersion"). Directly on top of either absorption line so-called "anomalous dispersion" may lead to group velocities that are faster than light, or even negative. However, this only happens at frequencies where there is strong absorption and pulse distortion. In (b) the two absorption peaks are replaced by two gain (amplification) peaks. This swaps the role of normal and anomalous dispersion, so that light at the gain frequency travels very slowly, while light at other frequencies (where the medium is essentially transparent) travels faster than the speed of light or at negative speeds.

http://plus.maths.org/issue12/news/fasterThanLight/
http://physicsweb.org/articles/world/13/9/3/1#pw-13-09-03fig2
Note that this does NOT mean that anything is moving faster than c. The link above gives this analogy:
 Quote: Suppose a lighthouse illuminates a distant shore. The rotating lamp moves quite slowly, but the spot on the opposite shore travels at a far greater velocity. If the shore were far enough away, the spot could even move faster than light. However, this moving spot is not a single "thing". Each point along the coastline receives its own spot of light from the lighthouse, and any information travels from the lighthouse at c, rather than along the path of the moving spot. Such phenomena are described as the "motion of effects", and are not forbidden by relativity.

 dwinton wrote: Light is very weird in many ways. I guess it is weird because it is a virtual particle. If you have no mass why should the laws of physics apply to you? But that is something else I have always wondered about: if E=mc2 and a photon has energy then you can solve for mass. If you take mass to be 0 then what makes the light move? I could understand not needing energy while light is traveling through a vacuum, but light particles can give atoms energy or they can be released by powered up atoms. For them to give energy they must have some (conservation of energy) and to be shot out of the atom, they must be acted upon by some force.

OK...there are two measures of mass - invariant, rest or intrinsic mass is one. Relativistic or apparent mass is the other. The invariant mass is what we are used to and does not change. Light, by this measure has no mass. The relativistic mass is mass which results from applying Special Relativity to calculate the effect of speed. By this measure light does have mass. The mass depends on velocity.
Using e=hf (energy = Plancks constant * frequency)
and e = mc^2
We can substitute and get
mc^2 = hf
m = hf/c^2
So we could say that light has a mass of hf/c^2. This is not technically correct in physics today, however, and we should instead say the photon has no mass because invariant mass is the preferred measure.
vlad02
 Please Use Quote Tags When Copying And Pasting wrote: I don't think it is possible to travel through time. Ome theories, most notably special and general relativity, suggest that suitable geometries of spacetime, or specific types of motion in space, may allow time travel into the past and future if these geometries or motions are possible.[3] In technical papers physicists generally avoid the commonplace language of "moving" or "traveling" through time ('movement' normally refers only to a change in spatial position as the time coordinate is varied), and instead discuss the possibility of closed timelike curves, which are worldlines that form closed loops in spacetime, allowing objects to return to their own past. There are known to be solutions to the equations of general relativity that describe spacetimes which contain closed timelike curves, but the physical plausibility of these solutions is uncertain. But, maybe in the future, will go and fight with Caesar with bazookas...
Bikerman
 vlad02 wrote: I don't think it is possible to travel through time. Ome theories, most notably special and general relativity, suggest that suitable geometries of spacetime, or specific types of motion in space, may allow time travel into the past and future if these geometries or motions are possible.[3] In technical papers physicists generally avoid the commonplace language of "moving" or "traveling" through time ('movement' normally refers only to a change in spatial position as the time coordinate is varied), and instead discuss the possibility of closed timelike curves, which are worldlines that form closed loops in spacetime, allowing objects to return to their own past. There are known to be solutions to the equations of general relativity that describe spacetimes which contain closed timelike curves, but the physical plausibility of these solutions is uncertain. But, maybe in the future, will go and fight with Caesar with bazookas...

Well that's what Wikki says, but how about you?
spam
why do people even find time travel interesting? We are here, now, this is where we belong, this is where our culture is - we would just be lost in another time...
Teal'c36
Why do we find time travel interesting? we all make mistakes we want to fix. We would also love to know how Egyptians built pyramids what Stonehenge was used for and if evolution is correct.

How sure are you that we belong here? How do you know we aren't the result of a single occurrence at random or if we are part of millions of planets with life.
Indi
Yes, the argument that we "belong" where we because that is where we happen to start out is really kind of silly. By that logic, we "belong" in caves, and should never have ventured out in ships, planes and spacecraft.

Why do people find any kind of travel, temporal or not, interesting? Because we are a curious people. We want to see what's over that next hump, even if that hump happens to be yesterday.
zichlone
i dont think that time travel to the future would be possible, because if you belive that then yo belive in fate because everything is fated to happen the way it is no matter what you do but i belive maybe just maybe you might be able to time travel (well not us if time travel could be achieved by a black whole we would die anyways)
Osmodius
 Indi wrote: You would be claiming that for the rest of time - the remainder of the existence of the universe - even though the technology exists and is known - no one is ever able to travel back?

I said it would be heavily-policed and only used by the government(s) who knew about it when absolutely necessary -- not locked in a dusty storage room fifty floors below ground at Area 51 for the rest of time.
Bikerman
Osmodius wrote:
 Indi wrote: You would be claiming that for the rest of time - the remainder of the existence of the universe - even though the technology exists and is known - no one is ever able to travel back?

I said it would be heavily-policed and only used by the government(s) who knew about it when absolutely necessary -- not locked in a dusty storage room fifty floors below ground at Area 51 for the rest of time.

Quite right, you did say that. The problem is that this assumes that all future existence has governments which are prepared and willing to go along with this deception, and of such skill, power (or luck?) that they manage to keep it secret. On both cases that would seem fairly unlikely.
Jamie Summersett
On the topic of extra dimensions...It is said there are many flavors of neutrinos. Some passing through matter and slightly interacting, and others never at all. Try to imagin a environment where your normal matter was this neutrino and all this matter around that you can't see or feel, or interact with. Matter as we know it would be the neutrino. I believe that there is the example of other dimensions. It is like wavelengths of light and energy. Also there is wavelengths of matter. If we were to imagine an environment were what we call energy was the matter, how would we experience matter as we know it. Maybe we would be the super dense matter. Our matter may be limited by the speed of our electron flow. But there may be other types of energy in sections on the other side of the universe where electron flow is slower or faster, Life for that type of environment would be faster or slower, all the way down to the molecules themselves. We can not use matter to detect non enteracting energys on defferent wavlengths. We would have to infer a reaction from various exotic waveforms that extend into the range of thease types of energys. As far as time travel goes logic rules first, then other multiverses, then extra dimensions. I think light is not a limit to speed. And in no way is our veiw of matter or energy complete. We should not base our complete ideas or limit them to the best ideas of the day. More insightfull ones will come and replace them or add to them. Just as people once thought the world was flat, and earth was the center of the solar system, so new ideas will come to replace the old. By not being stiff minded like to people of the day new ideas came to define our world as we see it. So will new ideas need to come from not excepting the common theorys of the day.
Bikerman
 Jamie Summersett wrote: On the topic of extra dimensions...It is said there are many flavors of neutrinos. Some passing through matter and slightly interacting, and others never at all. Try to imagin a environment where your normal matter was this neutrino and all this matter around that you can't see or feel, or interact with.

That is surely not possible to imagine. The neutrino is essentially a massless 'particle'.
 Quote: Matter as we know it would be the neutrino. I believe that there is the example of other dimensions. It is like wavelengths of light and energy. Also there is wavelengths of matter. If we were to imagine an environment were what we call energy was the matter, how would we experience matter as we know it. Maybe we would be the super dense matter. Our matter may be limited by the speed of our electron flow. But there may be other types of energy in sections on the other side of the universe where electron flow is slower or faster, Life for that type of environment would be faster or slower, all the way down to the molecules themselves.
I don't understand this. I cannot imagine matter made from neurinos and I don't understand how matter could then have a wavelength.
There is no evidence to support the notion that the rules of physics are different in different parts of the universe - in fact one of the important underlying assumptions of relativity is that the rules apply everywhere.
 Quote: We can not use matter to detect non enteracting energys on defferent wavlengths. We would have to infer a reaction from various exotic waveforms that extend into the range of thease types of energys.

By definition you cannot interact with non interacting entities. Neutrinos are not, however, completely non interacting. They can interact in two ways - via either neutral or charged current. There are, in fact, many attempts to detect neutrinos going on at the moment.
 Quote: As far as time travel goes logic rules first, then other multiverses, then extra dimensions. I think light is not a limit to speed.
OK, since you agree that logic comes first then please explain why you believe that Special Relativity is wrong? What logic leads you to suppose that light is not a limit?
 Quote: And in no way is our veiw of matter or energy complete. We should not base our complete ideas or limit them to the best ideas of the day. More insightfull ones will come and replace them or add to them. Just as people once thought the world was flat, and earth was the center of the solar system, so new ideas will come to replace the old. By not being stiff minded like to people of the day new ideas came to define our world as we see it. So will new ideas need to come from not excepting the common theorys of the day.

No...that is not how science generally works. You do not start by dismissing current theory just for the sake of it. You start by observing something which current theory cannot explain and then you are justified in saying that theory must be wrong.
Einstein did not start by dismissing Newtonian physics. He started by trying to explain how Maxwell's equations could be explained in terms of Newtonian physics. He found that they couldn't and only then went on to consider a new theory which could. Why would you want to ditch current theory just for the sake of it? Remember that any current theory in science has experimental and observational support and is not just a whim. You ditch a theory once it has been refuted, not simply on a whim. So far you have presented no reasons why we should do so and no observation that contradicts current theory.
You seem to be starting from the view that time travel is possible and, because of this, current theory must be wrong. That is not a sensible way to proceed.
chris20
Ive read that it is possible if you use the event horizon of a black hole, so you can go into the future. But i also saw a video explaining the 10 dimensional theory, and according to that, which was based on a book, time travel into the past is possible if you can create a fold in the 5th dimension i think. thats all for now.
Teal'c36
of couse all of this is based on a guess. And of couse just because we know how doesn't mean we can or its possible. Imagine the energy requirements to bend the 4th (or fifth) dimension).

Think how hard it is to create extreme speed in the third dimension. If we wish to travel through time we would need to create an extremely large/powerful power source.
Ennex
It is possible according to Star Trek XD

But i'm not a scientist but from what i know, according to Einsteins theory of relativity it is possible....but the power and speed required to achieve it is so great that nothing we have at this present state of age can get near the minimum requirements for it.

Several ways...one of the main theorys (regardless of ST IV) is slingshot around a sun...the gravitational pull can send you backwards or forewards through time

Ennex
Teal'c36
haven't heard the slingshot method. Don't think it would work tho. The method i heard (similar) would involve a black hole but at that point it is unknown if you would survive the trip or if your atoms would separate and they end up as individual atoms and sent back to an earlier time (most likely the formation of the black hole)
newolder
 Teal'c36 wrote: haven't heard the slingshot method. Don't think it would work tho. The method i heard (similar) would involve a black hole but at that point it is unknown if you would survive the trip or if your atoms would separate and they end up as individual atoms and sent back to an earlier time (most likely the formation of the black hole)

Both methods are purely fictional though: what time-asymmetry exists in a relativistic slingshot, please? and, the spaghettification of atomic material happens a long way from where time's imaginary component (Hawking, 1974) has notable effect in the near vicinity of gravitational black hole singularities.

There's a pod-cast hosted at universetoday.com on Dark Energy stars that may be of general interest...

Here's the url :: http://www.universetoday.com/audio/UT041405darkenergy.mp3

ed.
Teal'c36
I believe the premise behind the theories was that gravity can affect time and the more mass something has the more its affect on time. There is also the fact that light has an amazing ability to do this to. (which is the premise behind another theory i have a youtube video posted previous on)
Bikerman
 Teal'c36 wrote: I believe the premise behind the theories was that gravity can affect time and the more mass something has the more its affect on time. There is also the fact that light has an amazing ability to do this to. (which is the premise behind another theory i have a youtube video posted previous on)

This is Gravitational Time Dilation - as described by GR. Gravitational slingshots, however, are normally used by science-fiction to explain time travel as a result of the increased velocity that the object acquires rather than the gravitational time dilation....
dwinton
 Ennex wrote: But i'm not a scientist but from what i know, according to Einsteins theory of relativity it is possible....but the power and speed required to achieve it is so great that nothing we have at this present state of age can get near the minimum requirements for it. Ennex

Do you remember basic physics? Bear in mind F=ma, M=M(0)/sqrt(1-v^2/c^2)

As you get closer to the speed of light, your mass approaches infinity. By getting more massive, in addition to increasing your gravitational pull (which would probably make you implode into a black hole) you also require a greater force to continue accelerating. Accelerating to the speed of light is, therefore, impossible for any object with mass.

However, I have several theories on this topic. You accelerate in certain frames of reference but not others. What if you could move at half the speed of light and you somehow moved the universe around you at more than half the speed of light you could go faster than light without the heavies. Also, if there were some way you could convert your mass into energy in the shape of focused photons and then somehow convert it back to mass when you reach your destination you would be set
Bikerman
dwinton wrote:
 Ennex wrote: But i'm not a scientist but from what i know, according to Einsteins theory of relativity it is possible....but the power and speed required to achieve it is so great that nothing we have at this present state of age can get near the minimum requirements for it. Ennex

Do you remember basic physics? Bear in mind F=ma, M=M(0)/sqrt(1-v^2/c^2)

As you get closer to the speed of light, your mass approaches infinity. By getting more massive, in addition to increasing your gravitational pull (which would probably make you implode into a black hole) you also require a greater force to continue accelerating. Accelerating to the speed of light is, therefore, impossible for any object with mass.

However, I have several theories on this topic. You accelerate in certain frames of reference but not others. What if you could move at half the speed of light and you somehow moved the universe around you at more than half the speed of light you could go faster than light without the heavies. Also, if there were some way you could convert your mass into energy in the shape of focused photons and then somehow convert it back to mass when you reach your destination you would be set

What do you mean by this (ie 'You accelerate in certain frames of reference but not others')? Surely acceleration is represented by a non-geodesic line through spacetime and free-fall is represented by a geodesic. There is no transformation that I know that can convert one to the other, and no point of view which would allow such a transformation. That would seem to mean that there must be an absolute difference between accelerated and non accelerated motion - regardless of whether we are considering acceleration due to gravity or due to some other force.
Teal'c36
i think the motion idea he had was like this. I'm not moving in my location on earth. However the earth is movie so my location in the solar system is changing. His proposed idea would involve you moving slightly slower then the speed of light in one direction and making the universe move in the oposing direction so the difference between the two speeds is more then the speed of light.
Indi
 Bikerman wrote: What do you mean by this (ie 'You accelerate in certain frames of reference but not others')? Surely acceleration is represented by a non-geodesic line through spacetime and free-fall is represented by a geodesic. There is no transformation that I know that can convert one to the other, and no point of view which would allow such a transformation. That would seem to mean that there must be an absolute difference between accelerated and non accelerated motion - regardless of whether we are considering acceleration due to gravity or due to some other force.

Perhaps he did not only mean inertial frames of reference.

 Teal'c36 wrote: i think the motion idea he had was like this. I'm not moving in my location on earth. However the earth is movie so my location in the solar system is changing. His proposed idea would involve you moving slightly slower then the speed of light in one direction and making the universe move in the oposing direction so the difference between the two speeds is more then the speed of light.

i don't see any logic that would allow such an effort to violate relativity. It sounds to me like the old problem - a space ship is moving at .75c, and on that space ship i run from the aft to the fore at .75c... so to an outside observer i should appear to be moving at 1.5c, right?

Wrong, as you know. So what changes when it's not a space ship that's moving, but the universe?
chasbeen
It might be possible to view the past. When you look at a star you are looking at the light from the past.

If you magnified the view then you could "see the past" but not interact with it.

Interacting with the past as if you are there would be too paradoxical.

No it's not possible.
Teal'c36
But the paradox had been covered and the way to solve for it would be to let it happen and have an alternate universe. The idea that anything that could happen will and has. At the beginning of the universe Scientists have claimed that the laws of physics break down and nothing follows any known order. It is possible when can recreate that if we tap into the right energy and that would allow time travel.
newolder
Teal'c36>...At the beginning of the universe Scientists have claimed that the laws of physics break down and nothing follows any known order...

It doesn't take a scientist to realise that a 1/r^2 dependency (e.g. in gravitational or electrostatic force exchange) -> infinity as r -> 0 (i.e. the 'old laws' of physics do indeed break down at the classical limits of their applicability). That's how quantum theory was discovered and the Uncertainty Principle (dE dt, dx dp >= h-bar) helps 'smear out' the universe on small scales.

The number of ways this allows one to 'order' the universe correctly depends upon the number of objects in the universe. For example, if the universe were empty, there'd be nothing to explain: if it contained 1 object, there'd be no frame of reference to show it spinning in any way (Mach): if there are two objects e.g. a hydrogen atom of 1 proton and 1 electron, we need consider all the interactions possible and Feynman diagrams get most of the way there: only the Higgs field remains to be observed in that 'standard model' to bring completeness. Finally, if there are three (or more) objects e.g. the 'system' of Sol, Earth and its moon, then gravity must be incorporated in the model. The 'best' theory of gravity we have, so far, is due to Einstein/Minkowski and tests are underway to check its predictions daily (e.g. Gravity Probe 'B').

The 'order' we observe may be new and/or unexpected but, there you go. Deal with it. ed.
Bikerman
 newolder wrote: The number of ways this allows one to 'order' the universe correctly depends upon the number of objects in the universe. For example, if the universe were empty, there'd be nothing to explain: if it contained 1 object, there'd be no frame of reference to show it spinning in any way (Mach): if there are two objects e.g. a hydrogen atom of 1 proton and 1 electron, we need consider all the interactions possible and Feynman diagrams get most of the way there: only the Higgs field remains to be observed in that 'standard model' to bring completeness. Finally, if there are three (or more) objects e.g. the 'system' of Sol, Earth and its moon, then gravity must be incorporated in the model. The 'best' theory of gravity we have, so far, is due to Einstein/Minkowski and tests are underway to check its predictions daily (e.g. Gravity Probe 'B'). The 'order' we observe may be new and/or unexpected but, there you go. Deal with it. ed.

Can I respectfully assume the role of inquisitor here to push this a bit further Ed, by asking some questions which seem to follow on and which I think many people might ask?
• a)Is an empty universe the same as 'nothing' - by which I mean the absence of spatial and temporal dimensions - no space and no time?
• b)
• i. Is spacetime itself not 'something' with which a single object in a universe would spin relative to - a classical interpretation of Relativity? Thus a spinning object would display inertial effects even in the absence of other bodies as reference points.
• ii. Alternatively was Mach correct is his posit that without reference points the question is meaningless and there would be no 'spinning' and therefore no intertial effects?
• c)Is what we would call empty space really just a Higgs field which particles move through and which accounts for what we perceive as mass?
newolder
 Bikerman wrote: ... Can I respectfully assume the role of inquisitor here to push this a bit further Ed, by asking some questions which seem to follow on and which I think many people might ask? a)Is an empty universe the same as 'nothing' - by which I mean the absence of spatial and temporal dimensions - no space and no time?b)i. Is spacetime itself not 'something' with which a single object in a universe would spin relative to - a classical interpretation of Relativity? Thus a spinning object would display inertial effects even in the absence of other bodies as reference points.ii. Alternatively was Mach correct is his posit that without reference points the question is meaningless and there would be no 'spinning' and therefore no intertial effects?c)Is what we would call empty space really just a Higgs field which particles move through and which accounts for what we perceive as mass?

Erm. You can ask anything you like.

Nothing = Null = Void = timeless expanse of nowt = Empty

Mach is correct.

Objects have the property 'mass = true' if they exchange energy/momentum via a spin 2, massless, neutral(?) boson that's probably in the image library at Fermilab but will, no doubt(?), show up at LHC/CERN soon enough.

I hope it's resolved before the shock from eta Car. passes by...

http://newolder.netfirms.com/Red%20Square%20and%20Rectangle%20nebulae.htm

So it goes. ed.
benjmd
Here is a timeline:

(1) You decide to travel through time.
(2) You engage in an act that causes you to travel through time.
(3) You arrive at your destination.

We measure time by seconds, minutes, etc based on decay of particles, blah blah blah. We measure time by events.

Time travel is an action and actions are events. The action is proceeded by the decision to carry out the action, which is also an event. The action is followed by the condition in which the action has occurred, which is another event. These three events must happen in that order by the very way in which they exist at all.

The consequence? Time travel would simply be an action within the greater series of events in the Universe and you would therefore not actually change your position among the events. You can always recreate the configurations of previous events but their recreation does not obviate their previous existence.

No time travel, sorry.
Mr_CEO
Suppose time travel was invented (and it is possible to travel back in time). Suppose that you're right, and it is heavily monitored and policed so that no tourists could come back.

How long could that last? 50 years? 100? 10,000?

You would be claiming that for the rest of time - the remainder of the existence of the universe - even though the technology exists and is known - no one is ever able to travel back? Even if humanity is extinguished (and how could that happen if someone could travel to the future, fund out about it, then go back and prevent it?), no alien researchers who wanted to find out about the civilization that was beaming all that crap out into space would go back to see?

Seems a little far-fetched to me.
Teal'c36
Benjmd the problem with your logic is you assume that there is a definite now and that you can't change passesnt events with future decissions. Then waht about this.

What if i decide to listen to a machine (refering to my movie post) and it sends me a message telling me to do something. I don't listen and move on and i get in a car crash and am crippled for the rest of my life. Now at the present i find that same machine and discover i can send a message to myself in the past. Since i know the message i heard before wont work i say something else and this averts the car crash. Would my actions of change the past and inevitably the course of my life?
DanielXP
I heard that a plane broke the speed of light/sound (Can't remember which one)

And each second was longer than like a second..

Its not like time travel as you might think but its still some thing

Well.. slowing down time.
Bikerman
 DanielXP wrote: I heard that a plane broke the speed of light/sound (Can't remember which one) And each second was longer than like a second.. Its not like time travel as you might think but its still some thing Well.. slowing down time.

Err...I think you might want to check your sources, get the full story and then, perhaps, not post it anyway.
Teal'c36
Scientists have proven time is relative. We knew that but this topic is about turning time backwards not slowing it down or speeding it up.
Edas
Who knows, the 'theory' of relativity itself could be questioned over a period of time. Don't think it will not be. If that is not done, then travelling faster than light might be out of question. There is the gravity travel; theories do say they travel at speeds of light only. But there is more to be unravelled.
As to invisibility, it will be a surprise if the army does not have it. Today it doesn't seem to be a very difficult technology.
EanofAthenasPrime
 _AVG_ wrote: They say that Time Travel can be possible. But how? I feel that the idea of Cosmic Strings, Black Holes and Galaxies out there can lead to Time Travel. What do you think? Another reason why it seems that Time Travel is impossible is because if it were possible in the future, tourists would be visiting us here.

you know what is so amazing you will be like "WOA!"

I know how to time travel to the future. YEsir, I certainly do know how. Are you ready?

...WOA! We just time traveled to the future!

isnt that just amazing.

As to invisibility, it will be a surprise if the army does not have it. Today it doesn't seem to be a very difficult technology.

ACTIVE CAMOFLAGE. just put some already invented "cloth screens", have a micro camera and micro PC get the screen's image and transform it to the cloth screens, and YOU could be just like those Covenant Zealots AS SEEN ON TV!
EanofAthenasPrime
 Mr_CEO wrote: Suppose time travel was invented (and it is possible to travel back in time). Suppose that you're right, and it is heavily monitored and policed so that no tourists could come back. How long could that last? 50 years? 100? 10,000? You would be claiming that for the rest of time - the remainder of the existence of the universe - even though the technology exists and is known - no one is ever able to travel back? Even if humanity is extinguished (and how could that happen if someone could travel to the future, fund out about it, then go back and prevent it?), no alien researchers who wanted to find out about the civilization that was beaming all that crap out into space would go back to see? Seems a little far-fetched to me.

I am suprised that noone hear has mentioned that if you went back in the past IT WOULD BE A DIFFERENT UNIVERSE! USE WIKIPEDIA KIDS! YOU CANT GO BACK IN TIME AND KILL YOURSELF! IF YOU DID THAT WOULD DESTROY THE UNIVERSE! IF YOU WENT BACK IN TIME IT WOULD CREATE A DUPLICATE UNIVERSE WHERE YOU COULD KILL "YOURSELF" AS MUCH AS YOU FELT LIKE! YOU CANNOT GO BACK IN TIME INTO A UNIVERSE THAT YOU DEFINED WITH YOUR ACTIONS
EanofAthenasPrime
 Jamie Summersett wrote: On the topic of extra dimensions...It is said there are many flavors of neutrinos. Some passing through matter and slightly interacting, and others never at all. Try to imagin a environment where your normal matter was this neutrino and all this matter around that you can't see or feel, or interact with. Matter as we know it would be the neutrino. I believe that there is the example of other dimensions. It is like wavelengths of light and energy. Also there is wavelengths of matter. If we were to imagine an environment were what we call energy was the matter, how would we experience matter as we know it. Maybe we would be the super dense matter. Our matter may be limited by the speed of our electron flow. But there may be other types of energy in sections on the other side of the universe where electron flow is slower or faster, Life for that type of environment would be faster or slower, all the way down to the molecules themselves. We can not use matter to detect non enteracting energys on defferent wavlengths. We would have to infer a reaction from various exotic waveforms that extend into the range of thease types of energys. As far as time travel goes logic rules first, then other multiverses, then extra dimensions. I think light is not a limit to speed. And in no way is our veiw of matter or energy complete. We should not base our complete ideas or limit them to the best ideas of the day. More insightfull ones will come and replace them or add to them. Just as people once thought the world was flat, and earth was the center of the solar system, so new ideas will come to replace the old. By not being stiff minded like to people of the day new ideas came to define our world as we see it. So will new ideas need to come from not excepting the common theorys of the day.

tell me about it...I was banned from an "official science forum" simply because I refuted newton's view of gravity.
Bikerman
 EanofAthenasPrime wrote: tell me about it...I was banned from an "official science forum" simply because I refuted newton's view of gravity.

Really? Care to share your refutation with us? I'm pretty sure you won't be banned for it.
EanofAthenasPrime
Bikerman wrote:
 EanofAthenasPrime wrote: tell me about it...I was banned from an "official science forum" simply because I refuted newton's view of gravity.

Really? Care to share your refutation with us? I'm pretty sure you won't be banned for it.

Lol, I can't even access my topic because they are cool like that. It was basically how he assumed that K involved mass, and on Earth, his formula could be correct, but since scientists haven't tested his formula in gravitational fields other than Earth's, it might not be correct.
Bikerman
EanofAthenasPrime wrote:
Bikerman wrote:
 EanofAthenasPrime wrote: tell me about it...I was banned from an "official science forum" simply because I refuted newton's view of gravity.

Really? Care to share your refutation with us? I'm pretty sure you won't be banned for it.

Lol, I can't even access my topic because they are cool like that. It was basically how he assumed that K involved mass, and on Earth, his formula could be correct, but since scientists haven't tested his formula in gravitational fields other than Earth's, it might not be correct.

K? What is K? Newton's formula does not only work on Earth and it has been quite thoroughly tested in gravitational fields other than that of Earth - simply astronomy provides ample opportunity to test the basic equation:
F(g) = G(M1.M2)/r^2

Correction made to equation (F(g) -> g)
newolder
Bikerman wrote:
EanofAthenasPrime wrote:
Bikerman wrote:
 EanofAthenasPrime wrote: tell me about it...I was banned from an "official science forum" simply because I refuted newton's view of gravity.

Really? Care to share your refutation with us? I'm pretty sure you won't be banned for it.

Lol, I can't even access my topic because they are cool like that. It was basically how he assumed that K involved mass, and on Earth, his formula could be correct, but since scientists haven't tested his formula in gravitational fields other than Earth's, it might not be correct.

K? What is K? Newton's formula does not only work on Earth and it has been quite thoroughly tested in gravitational fields other than that of Earth - simply astronomy provides ample opportunity to test the basic equation:
g = G(M1.M2)/r^2

Yes, what is K supposed to represent? And, sorry Chris, shouldn't that be F =.... ? Lower-case g is usually reserved for the acceleration due to gravity near the Earth's surface that Newton predicts (via F = d(mv)/dt or, for constant mass, m dv/dt = ma = mg) to be: g = G M(Earth)/r(Earth)^2, in units of ms^-2.

A 'refutation' of these basics would involve changes to observed reality hereabouts. For example, if i were to drop a penny and a pound (coins) simultaneously from the same height, any deviation from Newton would show up in their different travel times to the (ground) surface below. ed.
Bikerman
 newolder wrote: And, sorry Chris, shouldn't that be F =.... ? Lower-case g is usually reserved for the acceleration due to gravity near the Earth's surface that Newton predicts (via F = d(mv)/dt or, for constant mass, m dv/dt = ma = mg) to be: g = G M(Earth)/r(Earth)^2, in units of ms^-2.
Quite Right....typo..
EanofAthenasPrime
Wow. K is from Kepler's orbit equations, and as I said before any tests done in earth gravitational field cannot prove me wrong, as my theory states Newton's laws could be wrong in places other than Earth's.

newolder
 EanofAthenasPrime wrote: Wow. K is from Kepler's orbit equations, and as I said before any tests done in earth gravitational field cannot prove me wrong, as my theory states Newton's laws could be wrong in places other than Earth's.

That's why we use General Relativity theory: Newton isn't 'wrong', simply inapplicable in certain, well-understood circumstances. ed.
Bikerman
 EanofAthenasPrime wrote: Wow. K is from Kepler's orbit equations, and as I said before any tests done in earth gravitational field cannot prove me wrong, as my theory states Newton's laws could be wrong in places other than Earth's.

You still have no said what K is. Kepler's three laws contain no 'K' - what is the quantity being represented by K?
As I said before, atronomy is not done in Earth's gravitational field most of the time. Consider, for example, the orbit or Mars around the Sun.
Postulating that a theory could be wrong in certain conditions does not, itself, form a theory.
EanofAthenasPrime
OMG you guys will NEVER understand.

Kepler's:
K=sqr(v)*r

Newtons:
GM=sqr(v)*r

What I am saying, is that Newton took the liberty of making up GM to replace K, and it is only proven to be true on this planet's gravitational field. Not very scientific to assume something is true with only one experiment is it? The people who banned me from their forum must think so.
newolder
 EanofAthenasPrime wrote: OMG you guys will NEVER understand. ...

That's a testable hypothesis.

Could you please supply the source material or a reference url for those equations? They read like gibberish but the error will be trivial to rectify. ed.
EanofAthenasPrime
I cannot, the forum banned me
newolder
 EanofAthenasPrime wrote: I cannot, the forum banned me

Tough!

One of the things about science is its repeatability. Surely you remember from where you trawled those ridiculous 'equations'? Or did you make them up yourself? I have read some of Newton's work but was only taught what Kepler said or did, however, i don't recall anything like those 'equations'. What are they supposed to represent? And what source did you derive them from? ed.
Bikerman
newolder wrote:
 EanofAthenasPrime wrote: I cannot, the forum banned me

Tough!

One of the things about science is its repeatability. Surely you remember from where you trawled those ridiculous 'equations'? Or did you make them up yourself? I have read some of Newton's work but was only taught what Kepler said or did, however, i don't recall anything like those 'equations'. What are they supposed to represent? And what source did you derive them from? ed.

It appears pretty trivial, so I'll have a bash since my math is probably equally trivial .

Kepler's 3rd law (if I remember correctly) relates the square of orbital velocity to the cube of orbital distance (in the form of the semi-major axis to arrive at a constant (we'll call it k). Thus Kepler's 3rd is normally written as
P1^2/P2^2 = R1^3/R2^3................(1)
(where P is period of revolution and R is length of semi-major axis).

If we simplify the problem to a circular orbit of a planet around the sun then the expression for centripetal force is fairly trivial to derive: -
F(net) = (M(planet) * v^2) / R............(2)

Newton realised that this force is the equivalent of the gravitational force and therefore simply equated terms 1 and 2.

You then get
(M(planet)*v^2) / R=(G*M(planet)*M(Sun) ) / R^2 ...(3)

For an object in circular orbit the velocity can be approximated as :
v=(2*pi*R)/P...................(4a)

Squaring this and substituting back into (3) gives us :
(M(planet)*4*pi^2*R)/P^2 = (G*M(planet)*M(Sun))/R^2...(4b)

Cancel out and we are left with
P^2/R^3=(4*pi^2)/(G*M(Sun))...........(5)

Note that the constant (k, if you like) derived this way is NOT dependant on Earth Gravity. If you plot the relationship for the planets of the Solar System you get :
Planet.................Period (yr)................Ave.Dist.(au).........T^2/R^3 (yr^2/au^3)
Mercury.................0.241.................................0.39..........................0.98
Venus....................0.615.................................0.72..........................1.01
Earth......................1.00..................................1.00..........................1.00
Mars.......................1.88..................................1.52..........................1.01
Jupiter....................11.8..................................5.20..........................0.99
Saturn....................29.5..................................9.54..........................1.00
Uranus...................84.0..................................19.18.........................1.00
Neptune..................165..................................30.06.........................1.00
Pluto.......................248..................................39.44.........................1.00

So you can see that Newton did not base his work soley on terrestrial physics and, indeed, it holds up in all orbital situations in our own Solar System.
EanofAthenasPrime
rofl laughing. You guys still do not understand. You all probably think like the people who banned me. It is so simple too. Until you guys provide a good reason for me to, I will not waste anymore energy trying to explain something with such vibrant simplicity to you.
newolder
 EanofAthenasPrime wrote: rofl laughing. You guys still do not understand. You all probably think like the people who banned me. It is so simple too. Until you guys provide a good reason for me to, I will not waste anymore energy trying to explain something with such vibrant simplicity to you.

Phew! That's a relief.

Thanks for the clarification, Bikerman.

Didn't Euclid know angular velocity (v = rw a plane circle) well before either of Kepler or Newton? Their input here was a) make the best possible observations b) combine them through maths ('the calculus') to make a greater whole...

That the whole is yet greater than these shoulders reveal wasn't known until the late 19th and 20th centuries respectively...

and onwards it roams...
Bikerman
 newolder wrote: Thanks for the clarification, Bikerman. Didn't Euclid know angular velocity (v = rw a plane circle) well before either of Kepler or Newton? Their input here was a) make the best possible observations b) combine them through maths ('the calculus') to make a greater whole...
Yes, I think that would be fair. Kepler, in particular, was not a great mathematician (despite being the royal 'mathematicus'). He stuck at it though and got much better as he got older - he's my role model, being a particular favourite since I read Koestler's 'Sleepwalkers'. His frequent and embarrassing bloopers in basic math don't change my opinion of his overall brilliant contribution to physics.
Newton is a different chappy entirely. Whilst I respect his work and genius, as any science-literate person must - I don't think I would have liked him at all.
I'd love to spend time with Koestler (and maybe even Galileo in small doses) but I feel sure that Newton would be too much effort and unrewarding company. I did once try to plough through the 'Principia' but I never got past book 1 (I remember thin king that it was all geometry and no calculus, but the memory is dim so I can't recall much of what I did read.
I think his debt to Hook, Flamsteed and Wren is rarely given the attention it deserves - Wren, for example, derived the inverse square 'law' at around the same time; Flamsteed seemed to be more aware of the implications of Gravity than Newton did and Hooke certainly had a better grasp of inertia and simple mechanics..correcting Newton on more than one occasion.
 Quote: That the whole is yet greater than these shoulders reveal wasn't known until the late 19th and 20th centuries respectively... and onwards it roams...

Indeed so. I wonder how long the almost exponential increase in human knowledge can/will continue..?
Bikerman
 EanofAthenasPrime wrote: rofl laughing. You guys still do not understand. You all probably think like the people who banned me. It is so simple too. Until you guys provide a good reason for me to, I will not waste anymore energy trying to explain something with such vibrant simplicity to you.

That is, of course, your prerogative. Up to now your refutation of Newton does, I agree, seem very simple. It is so simple (I think both Ed and I agree) that we don't see anything there at all. Perhaps, like the emperors clothes, it is too subtle, wise and beautiful for our course and world-weary senses to appreciate. Neither of us is in the first flush of youth, so maybe it looses something in the translation which is beyond us...it's always possible.

On the other hand, I'm no mathematician, but I'm not a maths dunce either. Ed is at a much higher level than I mathematically so the vibrant simplicity of your refutation of Newton must either be at a level of math far in excess of normal post-graduate stuff, or of such deceptive beauty that it has completely escaped us.
newolder
Chris>Indeed so. I wonder how long the almost exponential increase in human knowledge can/will continue..?

The grb from eta Car. will be sufficient to stop this particular planet's growth for a while (iff i've me sums right)*. If humanity doesn't leave the nest at great speed it'll perish like an unfed fledgling under a grill. The clock is ticking, we've got what? 10 thousand years? Hardly a crow's wing-beat across Sol in comparison...

Physics is solvable: the answer is eta Carinae. So it goes. ed.

* And probably most of planetary 'life' this side of the Milky Way too. I've written the summary as htm but the details would probably need further attention, off-line...
Indi
 newolder wrote: Physics is solvable: the answer is eta Carinae. So it goes. ed.

Heh, nice. ^_^; You should make a signature out of that.
EanofAthenasPrime
Fine....omg last and final explanation.

This book, called final theory, has an equation derived from Kepler called
K=sqr(v)*r . This is the Orbit equation. What I posted (and was banned for) was based on the first (free) chapter of "The Final Theory."

What I said, was that Newton made a wild guess that K=Gravity*Mass. He found that he can be provable, on Earth, if g is at a constant 6.67*10^-11 then GM will work to replace K. However, his "constant", G, maybe very well be different on other gravitational fields. There is no proof except that it is always 6.67 except on Earth.

If you guys cannot understand that, there is no hope.

Also, I think that human intellegience will stagnate for 97% of the populations, and through the 3%, the desire to not be like the 97% will upgrade their intellegience. Also, there will be a great boon when I introduce cyborgs into the population.

Also, what does this have to do with time travel?
newolder
 Indi wrote: ... Heh, nice. ^_^; You should make a signature out of that.

Done! (@sciencefile.org)

Is yours of your own imagination too? ed.
noobcola
I'm going to say that it is impossible.

Said earlier, there are too many paradoxes involved in time travel.

Also, through Einstein's equation of time and relativity, as velocity of an object approaches the speed of light, the time that passes relative to the observer approaches 0. For example, a particle of light that came from the big bang would be just as old today with respect to the observer.

Not only that, but it takes an infinite amount of energy to get near the speed of light.
EanofAthenasPrime
 noobcola wrote: I'm going to say that it is impossible. Said earlier, there are too many paradoxes involved in time travel. Also, through Einstein's equation of time and relativity, as velocity of an object approaches the speed of light, the time that passes relative to the observer approaches 0. For example, a particle of light that came from the big bang would be just as old today with respect to the observer. Not only that, but it takes an infinite amount of energy to get near the speed of light.

But I heard that the speed of light was gradually slowing? This would mean that light really isn't going the original speed of light, which means photons will eventually vanish. Unless photons themselves are the bringers of the time
dilation equation, or they have an infinite lifespan.
Indi
 EanofAthenasPrime wrote: But I heard that the speed of light was gradually slowing? This would mean that light really isn't going the original speed of light, which means photons will eventually vanish.
 EanofAthenasPrime wrote: Unless photons themselves are the bringers of the time dilation equation, or they have an infinite lifespan.

Time is meaningless in the context of photons. If you ask what the lifetime of a photon is, the answer is both "eternity" and "no time at all".
EanofAthenasPrime
Indi wrote:
 EanofAthenasPrime wrote: But I heard that the speed of light was gradually slowing? This would mean that light really isn't going the original speed of light, which means photons will eventually vanish.
 EanofAthenasPrime wrote: Unless photons themselves are the bringers of the time dilation equation, or they have an infinite lifespan.

Time is meaningless in the context of photons. If you ask what the lifetime of a photon is, the answer is both "eternity" and "no time at all".

I have read many times, from modern scientists, that c may very well be gradually slowing down. I have not read that link you made before. Anyway, I am talking about current modern science. And its slowing down rate make snails seem like rail guns.
iJonno
I was watching a show called 'Beyond Tomorrow' and they brought up the same topic. They was a company in a mine, miles under ground. They are building some mechanism and it uses atoms. Something to do with slamming them into each other by using what they have built. Im not to sure if the above information is correct because the show was on last year and I wasn't paying full attention at the time. Maybe if I see their website I might be able to get more information for you. But at the moment thats all I know.

Jonno'
EanofAthenasPrime
 iJonno wrote: I was watching a show called 'Beyond Tomorrow' and they brought up the same topic. They was a company in a mine, miles under ground. They are building some mechanism and it uses atoms. Something to do with slamming them into each other by using what they have built. Im not to sure if the above information is correct because the show was on last year and I wasn't paying full attention at the time. Maybe if I see their website I might be able to get more information for you. But at the moment thats all I know. Jonno'

particle accelerators? seems like old news.
Indi
EanofAthenasPrime wrote:
Indi wrote:
 EanofAthenasPrime wrote: But I heard that the speed of light was gradually slowing? This would mean that light really isn't going the original speed of light, which means photons will eventually vanish.
 EanofAthenasPrime wrote: Unless photons themselves are the bringers of the time dilation equation, or they have an infinite lifespan.

Time is meaningless in the context of photons. If you ask what the lifetime of a photon is, the answer is both "eternity" and "no time at all".

I have read many times, from modern scientists, that c may very well be gradually slowing down. I have not read that link you made before. Anyway, I am talking about current modern science. And its slowing down rate make snails seem like rail guns.

Are you sure? ^_^ You really might want to check your sources.

Remember that c isn't some isolated constant that you can change without any affect on the universe except for... well, slower light. c = 1 ÷ √(ε₀ × μ₀), so if c changes, one or both of those fundamental constants of the universe must be changing, too. Also, c = e² ÷ (2 × ε₀ × ℎ × α), so if you change ε₀ you're going to have tweak more values there. These are things that can be easily tested by looking at the wavelengths of light being emitted from distant stars (the spectrum of the light being emitted by a star has no relationship to the speed of the light - the spectrum isn't affected by blue or red shifting). Read up on experiments being done to determine whether c is changing, and if so what is the rate of change, and see what you find.
EanofAthenasPrime
Many of these findings where from that science forum I was banned from, making it impossible to show you the topics.
Teal'c36
Share the link man I'm sure we wouldn't be banned from this site if we signed up. Plus it lends much more to your credibility if you have some sources to back up statements rather then saying its on a forum you can't access.
Tumbleweed
 iJonno wrote: I was watching a show called 'Beyond Tomorrow' and they brought up the same topic. They was a company in a mine, miles under ground. They are building some mechanism and it uses atoms. Something to do with slamming them into each other by using what they have built. Im not to sure if the above information is correct because the show was on last year and I wasn't paying full attention at the time. Maybe if I see their website I might be able to get more information for you. But at the moment thats all I know. Jonno'

I saw a simular prog about scientists deep deep in a mine, they were catching cosmic rays (or interactions of) though, these travel at nearly the speed of light, It would be interseting to find out if these near the speed of light objects have any mass
Bikerman
 EanofAthenasPrime wrote: Fine....omg last and final explanation. This book, called final theory, has an equation derived from Kepler called K=sqr(v)*r . This is the Orbit equation. What I posted (and was banned for) was based on the first (free) chapter of "The Final Theory."
This explains a lot. The book 'Final Theory' is junk science.
 Quote: What I said, was that Newton made a wild guess that K=Gravity*Mass. He found that he can be provable, on Earth, if g is at a constant 6.67*10^-11 then GM will work to replace K. However, his "constant", G, maybe very well be different on other gravitational fields. There is no proof except that it is always 6.67 except on Earth.
You are quite wrong. Firstly you are describing G - the gravitational constant which appears in Newton's equations as a constant. It follows from the fact that Newton assumed that force was proportional to mass/distance^2. Replace the proportional with a constant and you get the Newtonian equation :
F(g) = G (M(1)*M(2)/r^2). There is no assumption that K=Gravity*Mass.
 Quote: If you guys cannot understand that, there is no hope.
I can understand it, it's just wrong.
EanofAthenasPrime
Bikerman wrote:
 EanofAthenasPrime wrote: Fine....omg last and final explanation. This book, called final theory, has an equation derived from Kepler called K=sqr(v)*r . This is the Orbit equation. What I posted (and was banned for) was based on the first (free) chapter of "The Final Theory."
This explains a lot. The book 'Final Theory' is junk science.
 Quote: What I said, was that Newton made a wild guess that K=Gravity*Mass. He found that he can be provable, on Earth, if g is at a constant 6.67*10^-11 then GM will work to replace K. However, his "constant", G, maybe very well be different on other gravitational fields. There is no proof except that it is always 6.67 except on Earth.
You are quite wrong. Firstly you are describing G - the gravitational constant which appears in Newton's equations as a constant. It follows from the fact that Newton assumed that force was proportional to mass/distance^2. Replace the proportional with a constant and you get the Newtonian equation :
F(g) = G (M(1)*M(2)/r^2). There is no assumption that K=Gravity*Mass.
 Quote: If you guys cannot understand that, there is no hope.
I can understand it, it's just wrong.

Again, you are starting to understand, but still not 100%.
F(g)= G (M(1)*M(2)/r^2) is just a complex adaptation of K. Again, they have only proved "F(g)= G (M(1)*M(2)/r^2)" works on Earth. Regardless of whether or not "Final Theory" is junk science, until they prove that that formula works on mars, or on the sun, Newtonian gravity will not pass by me unquestioned.
newolder
 EanofAthenasPrime wrote: ... until they prove that that formula works on mars, or on the sun, Newtonian gravity will not pass by me unquestioned.

Have you tried www.nasa.gov, www.esa.int or other space-exploration workers' sites? They use Newton all the time and only incorporate/test General Relativity theory at the extremes of the motions they work in.

Newtonian gravity theory is okay for Solar system dynamics and the only problem i've met is related to the Pioneer & Voyager probes as they leave the system. ed.
EanofAthenasPrime
newolder wrote:
 EanofAthenasPrime wrote: ... until they prove that that formula works on mars, or on the sun, Newtonian gravity will not pass by me unquestioned.

Have you tried www.nasa.gov, www.esa.int or other space-exploration workers' sites? They use Newton all the time and only incorporate/test General Relativity theory at the extremes of the motions they work in.

Newtonian gravity theory is okay for Solar system dynamics and the only problem i've met is related to the Pioneer & Voyager probes as they leave the system. ed.

ah...I think you may have proved me right. See, what I'm saying, is not that the Sun has a mass of only 1 gram. What I am saying is that in other gravitational fields, the mass may not always match up with Newtonian physics.
newolder
 EanofAthenasPrime wrote: ... ah...I think you may have proved me right. See, what I'm saying, is not that the Sun has a mass of only 1 gram. What I am saying is that in other gravitational fields, the mass may not always match up with Newtonian physics.

Science works by disproving hypotheses: your own here (that Newtonian gravity only works on Earth) has been successfully disproved by many individuals and teams of others.

If you check your sources you'll find that the Solar mass is given as 1.98892 × 10^30 kilograms

EanofAthenasPrime
They probably based that on newtonian gravity. You cant actually measure the sun. They need a extreme gravity measuring device and place on Mars to defeat my anti-theory, which I don't think has been done yet.
Indi
 EanofAthenasPrime wrote: They probably based that on newtonian gravity. You cant actually measure the sun. They need a extreme gravity measuring device and place on Mars to defeat my anti-theory, which I don't think has been done yet.

Not really. We already have "gravity measuring devices" that have verified the expected gravitational pulls of pretty much all the planets. Probes.

The probes we've launched that have passed by any body in the solar system have reacted in ways consistent with what would be expected from standard physics. Both Spirit and Opportunity have confirmed that Mars' gravitational pull is what we expected. Voyager 1 covered Jupiter and Saturn and Voyager 2 covered Neptune and Uranus. Pluto's the only commonly known body of interest in the solar system that hasn't had a close visit from us, and that ain't a planet no more, so we've covered all the planets. In all cases, theory held.
newolder
Ean...>...You cant actually measure the sun...

I do it daily*, SOHO** has been doing it for years and STEREO*** only improves the view. Incidentally, both probes and myself obey Newton to many decimal places.

There are very many sources that you obviously haven't met with, yet. There's probably still time if you are willing to spend the effort.

* e.g. The image at left was taken as totality approached Turkey in 2006.

** http://sohowww.nascom.nasa.gov/

*** http://stereo.gsfc.nasa.gov/
Bikerman
 EanofAthenasPrime wrote: Again, you are starting to understand, but still not 100%.
Really?
 Quote: F(g)= G (M(1)*M(2)/r^2) is just a complex adaptation of K.
No it isn't. It has nothing to do with K, it is simple algebra. Newton started with the assumption that gravity is proportional to mass and varies proportionally to the reciprocal of the square of the distance. That gives a basic expression F(g) is proportional to M/r^2. In order to turn this into an equation you do what is always done in such cases and replace the 'proportional' by 'equals' and multiply by a constant. This gives F(g) = constant * M/r^2. Newton called the constant G, but it has nothing to do with any assumptions about K - which you define as Gravity*Mass.
 Quote: Again, they have only proved "F(g)= G (M(1)*M(2)/r^2)" works on Earth.
Others have dealt with this so I will just say that you are incorrect here.
 Quote: Regardless of whether or not "Final Theory" is junk science, until they prove that that formula works on mars, or on the sun, Newtonian gravity will not pass by me unquestioned.
Questioning is good but you need to understand the question before the answer will make any sense.
EanofAthenasPrime
Ok...one final question: Have they ACTUALLY weighed the mass of a celestial body made of plasma. I don't mean, did they sit down to eat lunch at NASA and grab a calculator and used Newtonian formulas to. If not, I have not been disproven.
Bikerman
 EanofAthenasPrime wrote: Ok...one final question: Have they ACTUALLY weighed the mass of a celestial body made of plasma. I don't mean, did they sit down to eat lunch at NASA and grab a calculator and used Newtonian formulas to. If not, I have not been disproven.

You are still confused. Weight and mass are two different things. Newton's equation for Gravity makes no mention of weight and weight is not really relevant to this discussion directly since we are talking about gravity, which acts on mass according to the equation already listed earlier in the thread. (I could point out that weight experiments on the moon are entirely consistent with Newtonian physics but that is not the point).
Why should a body made of plasma be different to a body made of other materials?
newolder
Eanof...>If not, I have not been disproven.

Correct. But you must understand that neither has Newton been disproved on this topic.

Since the rest of the universe understands Newton whereas Eanof... doesn't, what view should i, a dispassionate observer, adopt?

Should Eanof... change its view?

Perhaps. ed.
EanofAthenasPrime
 newolder wrote: Eanof...>If not, I have not been disproven. Correct. But you must understand that neither has Newton been disproved on this topic. Since the rest of the universe understands Newton whereas Eanof... doesn't, what view should i, a dispassionate observer, adopt? Should Eanof... change its view? Perhaps. ed.

we'll wait and see.

btw...what does "ed." mean?
EanofAthenasPrime
 newolder wrote: Eanof...>If not, I have not been disproven. Correct. But you must understand that neither has Newton been disproved on this topic. Since the rest of the universe understands Newton whereas Eanof... doesn't, what view should i, a dispassionate observer, adopt? Should Eanof... change its view? Perhaps. ed.

Bikeman-I said "weigh" because I didn't want to say "calculate." I said "weigh" to demonstrate that they would literally have to weigh a star to disprove me, not just calculate its mass. What I mean is, they would litterally have to measure the star's mass. Only then can I be proven right (or wrong.)
Bikerman
 EanofAthenasPrime wrote: Bikeman-I said "weigh" because I didn't want to say "calculate." I said "weigh" to demonstrate that they would literally have to weigh a star to disprove me, not just calculate its mass. What I mean is, they would litterally have to measure the star's mass. Only then can I be proven right (or wrong.)

a) You cannot weigh a star....where would you put the scales?
b) What you said was
 Quote: Newton made a wild guess that K=Gravity*Mass. He found that he can be provable, on Earth, if g is at a constant 6.67*10^-11 then GM will work to replace K. However, his "constant", G, maybe very well be different on other gravitational fields. There is no proof except that it is always 6.67 except on Earth.

He did not make any sort of guess that K=Gravity*Mass. I presume you mean K to indicate weight? (I am confused because you keep using G and g interchangably). Neither did Newton make any assumptions about the value of G - he didn't know the value, he simply wrote it as a constant.
He did estimate it's value, based on a guess about the density of the Earth, but that has no real bearing on his formulation of the universal gravitational law.
newolder
EanofAthenasPrime wrote:
 newolder wrote: Eanof...>If not, I have not been disproven. Correct. But you must understand that neither has Newton been disproved on this topic. Since the rest of the universe understands Newton whereas Eanof... doesn't, what view should i, a dispassionate observer, adopt? Should Eanof... change its view? Perhaps. ed.

we'll wait and see.

btw...what does "ed." mean?

You can do what you like, we (homo sapiens) waited more than 250 years to see Einstein stretch things further (and postulate the constancy of c as a starting-point) and a further 100 years or so to the discovery that special unitary group theory in ten (or is it 11?) dimensions is sufficient to explain the observable universe (and very much more besides)*.

A good thing about internet chat-rooms like this is that the reader is often re-pointed towards the correct road and they find (for themselves) that absurdity isn't a prerequisite for a successful picture to emerge from the fog of their prior delusion.

e.g. "Warped Passages", Lisa Randall. (I don't have a copy, yet, but the writer is a fine physicist and i'm aware of her earlier work.)

Usual sign-off: ed.
EanofAthenasPrime
newolder wrote:
EanofAthenasPrime wrote:
 newolder wrote: Eanof...>If not, I have not been disproven. Correct. But you must understand that neither has Newton been disproved on this topic. Since the rest of the universe understands Newton whereas Eanof... doesn't, what view should i, a dispassionate observer, adopt? Should Eanof... change its view? Perhaps. ed.

we'll wait and see.

btw...what does "ed." mean?

You can do what you like, we (homo sapiens) waited more than 250 years to see Einstein stretch things further (and postulate the constancy of c as a starting-point) and a further 100 years or so to the discovery that special unitary group theory in ten (or is it 11?) dimensions is sufficient to explain the observable universe (and very much more besides)*.

A good thing about internet chat-rooms like this is that the reader is often re-pointed towards the correct road and they find (for themselves) that absurdity isn't a prerequisite for a successful picture to emerge from the fog of their prior delusion.

e.g. "Warped Passages", Lisa Randall. (I don't have a copy, yet, but the writer is a fine physicist and i'm aware of her earlier work.)

Usual sign-off: ed.

What is a "sign-off." And I assume you think I am deluded? For simply disagreeing with Newtonian theory? Get sane.
And I posted nothing about Einstein's theories.

Indi-What you and new older said has no relevance to the conversation. I am not arguing about the strength of gravitational pulls. I am arguing how the mass of celestial bodies may not quite match with Newtonian forumlae. I suspect plasma ones especially.

Bikeman-I'd hoped you could do better. The idea of using scales to weigh a star? Get real. To weigh a star you would have to build an uber durable shuttle to take samples from different layers of the core. And then measure its density.
b. Actually you are wrong. Newton calculated the value of G. And I apologize for not being scientifically/alphabetically consistent with my variable names. However, you are missing the point. When I say "weigh", I mean "to measure." Also, Newton made a critical assumption: (K stands for the equation K=sqr(v)*r derived from Kepler's Geometric Orbit Equation. It is is from this equation I am basing my argument. Newton (intentally or not) plaguarized this equation. He made a copy equation GM=sqr(v)*r. Kepler, being a true scientist, took no liberty of taking away
"K"'s intrinsic simplicity. Newton, however, made a "logical" assumption that K is directly equal to a constant number and mass. It sounds good, but here is the flaw: Newton based his constant, G, on only one experiment: Earth. Newton made a wild hypothesis and then finished it after he had found 6.67*10^-11 to match it up. How do we know that G will still be 6.67*10^-11 after we find the mass of the sun? Our current mass of the sun is based on a guess. )
Here is a crystal, to make this more clear.
Bikerman
 EanofAthenasPrime wrote: Bikeman-I'd hoped you could do better. The idea of using scales to weigh a star? Get real. To weigh a star you would have to build an uber durable shuttle to take samples from different layers of the core. And then measure its density.
And that is getting real?
 Quote: b. Actually you are wrong. Newton calculated the value of G.

I said so (he estimated it, calculation is too strong a word). I also said that he based it on a guess about the density of the earth.
 Quote: And I apologize for not being scientifically/alphabetically consistent with my variable names. However, you are missing the point.
I think not.
 Quote: When I say "weigh", I mean "to measure."
Why not say measure then?
 Quote: Also, Newton made a critical assumption: (K stands for the equation K=sqr(v)*r derived from Kepler's Geometric Orbit Equation.
We've been here already. As I said previously this is incorrect. Kepler's law could be written
T = k*R^3/2 (E1)(where T is the period of orbit, R is the semi-major axis and k is known as the constant of proportionality)
This follows directly from the statement of his 3rd law -
 Kepler wrote: The squares of the periods of the planets are proportional to the cubes of their semi-major axes
.
Can you show how your expression above is derived from this?
 Quote: It is is from this equation I am basing my argument. Newton (intentally or not) plaguarized this equation. He made a copy equation GM=sqr(v)*r. Kepler, being a true scientist, took no liberty of taking away "K"'s intrinsic simplicity. Newton, however, made a "logical" assumption that K is directly equal to a constant number and mass. It sounds good, but here is the flaw: Newton based his constant, G, on only one experiment: Earth.
This is complete baloney.
1) The equation you quote is not Kepler's. That would be k = T^2/R^3 (re-arranging E1 above). Perhaps I am missing something but I can't see how that can lead to k=SQRT(v)*r.
2) Newton's method was to equate centripetal force with gravity as I demonstrated earlier. Perhaps if I go slower?
a) Acceleration of a body in circular orbit is given by a=w^2*r (where w is angular velocity and r is distance [radius for a circular orbit]).
b) Angular velocity (w) is equal to linear velocity/r
c) Therefore we substitute to give a = (v^2/r^2) × r = v^2/r
d) Since Newton already knew that f=ma (force = mass * acceleration) then it follows that the centripetal force for the object (F) is given by m*v^2/r (E2)
e) Newton now DOES make an assumption. Whether or not the 'apple' story is true, he had already reasoned that the force which accelerates objects on earth such as the falling apple is the same force that holds the planets in orbit. It was known at the time that the acceleration of an object on Earth was around 9.8m/s^2 and it was also known that the moon accelerates towards the earth at around 0.00272 m/s^2. Obviously gravity must get weaker with distance but Newton needed an expression for this. Since the acceleration of the moon is 1/3600ths the acceleration of the apple Newton played with various relationships. The key was realising that the distance of the apple to the centre of the earth was 60 times the distance of the moon to the centre of the earth. This immediately suggests an inverse square relationship (ie the force would be 1/60^2 - 1/3600).
f) Newton now has an expression for the force of gravity which states it is proportional to 1/r^2 and also proportional to the mass. Therefore we get F(g) prop Mass/r^2 which is the same as F(g)=constant*Mass/r^2 (E3)
g) Assuming that the centripetal force in E2 is caused by gravity, Newton then equated E2 and E3. I won't go through the working again - I've already done it in a previous posting. It should be obvious, however, that Newtons derivation of the law of Universal Gravitation is NOT based on ANY plagiarising of Kepler's constant of proportionality.
h) In fact Newton now went on to apply HIS law of gravitation to Kepler's third law and modified it as a result so that it now reads:
(m1+m2)*T^2 = (d1+d2)^3 = r^3
(This more accurately allows for the centre of mass of the two bodies which Kepler's original did not.*

*

You might want to do some further reading and forget the Final Reality book.
http://csep10.phys.utk.edu/astr161/lect/history/newtongrav.html
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/circles/u6l3c.html
http://en.wikipedia.org/wiki/Law_of_universal_gravitation
EanofAthenasPrime
Well said, however I still, even with my only basic knowledge of equations I have learned from Final Theory and Wikepedia, am not proven complete wrong. Yes, I finally agree my statements and equations are based off of someone else's incorrect statements and equations. However, ignoring all complex rearrangements of equations and maths we are still left with the 6.67 *10^-11 problem. 6.67 might very well be 5.84, or 10.73 for a celestial body made of plasma. I don't know you could prove me wrong (until you build a shuttle that can withstand temperatures exceeding 15000+, fo real in da hood ,cuzin.)

newolder
 EanofAthenasPrime wrote: ...However, ignoring all complex rearrangements of equations and maths we are still left with the 6.67 *10^-11 problem. 6.67 might very well be 5.84, or 10.73 for a celestial body made of plasma....

The best theories today i.e. SU(10 & 11), work in units where 1/(8 Pi G) (that is equivalent to the Planck Mass squared* of other string theory) = 1

Since we already have h/2 Pi = h-bar = c = 1 from earlier, 20th century study, we have a complete theory of everything: special unitary group theory in 10 or 11 dimensions. Take your pick and place those bets...

Celestial bodies made of plasma include eta Carinae and its (ex-)twin SN2006gy. It's a blast, go figure. ed.

* http://arxiv.org/PS_cache/hep-th/pdf/0609/0609095v2.pdf
Bikerman
 EanofAthenasPrime wrote: Well said, however I still, even with my only basic knowledge of equations I have learned from Final Theory and Wikepedia, am not proven complete wrong. Yes, I finally agree my statements and equations are based off of someone else's incorrect statements and equations. However, ignoring all complex rearrangements of equations and maths we are still left with the 6.67 *10^-11 problem. 6.67 might very well be 5.84, or 10.73 for a celestial body made of plasma. I don't know you could prove me wrong (until you build a shuttle that can withstand temperatures exceeding 15000+, fo real in da hood ,cuzin.)

Since there is absolutely no reason to suspect that G *does* vary and plenty of reason to believe it does not then the problem is artificial. A similar example would be me saying that nobody can prove me wrong when I say that the speed of light is NOT constant and, in fact, c is equal to 4 miles per hour on Jupiter's third satellite every other Friday between 1pm and 1:02pm.
Sure, you can't prove me wrong. It does not mean that my theory is either sensible or even worthy of serious consideration.
Your original point was that Newton plagiarised an expression from Kepler that specified the gravitational constant. He didn't. The gravitational constant follows from the law of universal gravitation, not the other way around.
EanofAthenasPrime
An interesting comparison, but I think my theory is a bit more *solid*...

newolder-I don't mean to be rude but I am only in 11th grade, I have no idea what you are talking about.
newolder
Eanof...>newolder-I don't mean to be rude but I am only in 11th grade, I have no idea what you are talking about.

Which words are causing difficulty?
Bikerman
 EanofAthenasPrime wrote: An interesting comparison, but I think my theory is a bit more *solid*...

Really? Do you? How interesting. Perhaps you need to read a bit more on basic science - particularly what makes a theory and why this is not one.

The fact is that Newton's basic formulation of Gravity makes predictions and can be tested in a variety of ways by experiment and observation. It has been tested repeatedly both here on Earth, in our local solar system, in more distant galactic observations and in observations from deep deep space. So far there is no evidence that G varies at all.

Then we must consider that you have not actually proposed a theory.

A theory is a set of statements or propositions which explain a group of facts or phenomena in a logical manner. What you have proposed is that G is not constant. That is not an explanation of any known facts or observations. Neither is it backed up by any underlying explanation or mechanism of why G should vary - what mechanism would cause it to vary and under what circumstances would we expect to see this.

Finally we have to conclude that not only is this not a theory, it is not science either.

A scientific theory must not only explain, it must also be testable. If a proposal is not testable it cannot be said to be science, and your proposal can never be completely ruled out because you could say that until every entity in the universe has been measured there is still a possibility that G could vary.

So we are left with a non scientific proposal based on no supporting evidence, experiment or observations, which explains nothing, adds nothing new to our knowledge, and cannot be properly tested.

Hardly what I would call 'solid'........
EanofAthenasPrime
You are correct, it is not a theory. But if in a century they have proven that I am right, I will be rewarded. If not, then nothing bad happens to me. I have nothing to lose.
Bikerman
 EanofAthenasPrime wrote: You are correct, it is not a theory. But if in a century they have proven that I am right, I will be rewarded. If not, then nothing bad happens to me. I have nothing to lose.

Prove what right? So far you have expressed a doubt that G is constant. If, in a century, G is proven to be variable then the reward/credit will go to the scientist(s) who do the work which shows it to be so. You have done nothing useful in that regard since your proposition was based on a fallacy to start with and amounts to nothing more than a guess that G might not be constant. It takes a bit more than that to gain the respect and plaudits of the science community I'm afraid.
The way to gain the rewards is straightforward - spend the next decade or so learning enough physics to understand Newtonian mechanics and Relativity reasonably well, then spend the following decade engaged in serious experiment/theorising/research based on a sound theoretical knowledge if what you are proposing. You would possibly then be taken seriously if you posted on a science board expressing the opinion that G is not constant.
hackone
no way, it can not be possible. in every fantasy there must also be at least a drop of reality, in every kind of physics there must a drop of reality also. what has passed, has passed and would be naive to expect that it could happen again.

Imagine such thing: you decide to travel back to the future by 5 seconds with spaceship. then you stay in the place where you have came and after 5 seconds you see yourself coming from future to past again (because you have travelled and after 5 seconds future comes back) and it would happen till it reaches infinity. and infinity does not exist in the world which we realize.

though i do not dare to say that infinity does not exist at all. but just it is too complicated for us.

well, if for some of you it does not seem complicated, then answer this question, please: does universe has the beginning and the end? if yes, then what goes after and before it?
newolder
 hackone wrote: ...then answer this question, please: does universe has the beginning and the end? if yes, then what goes after and before it?

Roger Penrose, 2007 :: http://real.bnl.gov/ramgen/bnl/penrose.rm

(requires RealPlayer)

Discusses this question in fine (and conformal) detail to determine that the "beginning" and "end" times of the universe are indistinguishable states. ed.
Azmo
I doubt that time travel will ever be possible.. it would be to dangerous.. can change the future..
EanofAthenasPrime
 hackone wrote: no way, it can not be possible. in every fantasy there must also be at least a drop of reality, in every kind of physics there must a drop of reality also. what has passed, has passed and would be naive to expect that it could happen again. Imagine such thing: you decide to travel back to the future by 5 seconds with spaceship. then you stay in the place where you have came and after 5 seconds you see yourself coming from future to past again (because you have travelled and after 5 seconds future comes back) and it would happen till it reaches infinity. and infinity does not exist in the world which we realize. though i do not dare to say that infinity does not exist at all. but just it is too complicated for us. well, if for some of you it does not seem complicated, then answer this question, please: does universe has the beginning and the end? if yes, then what goes after and before it?

Lemme reword what you are saying: You go forward in time 5 seconds. Then you go back in time 5 seconds. In that case you would only see yourself once, not infinitely. Maybe I don't understand this puzzle, but that is what I think you are defining.
Bikerman
newolder wrote:
 hackone wrote: ...then answer this question, please: does universe has the beginning and the end? if yes, then what goes after and before it?

Roger Penrose, 2007 :: http://real.bnl.gov/ramgen/bnl/penrose.rm

(requires RealPlayer)

Discusses this question in fine (and conformal) detail to determine that the "beginning" and "end" times of the universe are indistinguishable states. ed.

Nice link. I think it would be fair to say that Penrose's analysis is not (yet?) 'standard' by which I mean that it is not the majority view amongst physicists. Since, however, Penrose is a leading light in this field, his views are always worth listening to and it would be a foolish person who dismissed them at this stage.
Penrose is, of course, a science hero of mine so have to confess an interest
Bikerman
 Bikerman wrote: You would possibly then be taken seriously if you posted on a science board expressing the opinion that G is not constant.

PostScript.
On reading my last reply back I see that it could be construed as implying that you are/will not be taken seriously on THIS board. That was not my intended point, and it would be rude and unwarranted of me to have said such a thing. To avoid confusion I should clarify the point - I meant that this was probably the reason why you were banned from the physics forum you mentioned earlier.
As regards this board, I try to consider all postings seriously and where that is not possible I normally avoid replying. As you can see from the extent of my postings on this thread, I took your point seriously and set about refuting it.*

*I am glad that you don't seem to have taken this the wrong way - many people confuse vigorous debate with personal rudeness/attack. Where I disagree with a point then I normally attack the point with as much rigour as I can, but this is in a true spirit of scientific debate and reflects the way that professional scientists would (and should) act in similar circumstances. Science is often a matter of attempting to refute ideas/proposals and doing so with some vigour - that is how theory is 'proven'. This should never be taken personally and should never stoop to personal comment, let alone personal abuse or criticism (though obviously it has frequently done so over the history of science because scientists are people too).
newolder
The only 'standard' thing i can think of in cosmology is the 'big bang' - a truly hideous usage as it was neither big (~10^-35 metres) nor went bang (for there was only radiation at the time and no medium for sound waves to travel through for some further time to phase-change).

The three ideas Penrose discusses: Loop Quantum Gravity (Lee Smolin), Cyclic Ekpyrosis in an 11-D universe (Steinhardt & Turok) and his own 10-D view each have their associated apparent 'crazinesses': budding universes inside black-hole event horizons, a fourth space dimension and a conformal map to take conditions at t^-infinity to be identical (to Heisenberg uncertainty and matter distribution effects) to those at t^+infinity.

But the observations of Dark Matter's influence*, COBE, WMAP, distant supernovae and hypernovae (SN2006gy, eta Carinae &c) and the seeming absurdities of QED (light travels every conceivable path, weighted by probability) mean that anything with the remotest chance of being correct has to look a bit crazy, at first. (Reminds me of myself! )

Penrose claims that 'the geometry exists' but it sure looks ouroborotic to me, sometimes... ed. (What does Razz mean in a smiley-context, please?)

* e.g. Santa Cruz University:: http://press.ucsc.edu/text.asp?pid=977

and HST's recent 'zoomable' publication:: http://hubblesite.org/newscenter/archive/releases/2007/17/image/a/format/zoom/

Bikerman
 newolder wrote: The only 'standard' thing i can think of in cosmology is the 'big bang' - a truly hideous usage as it was neither big (<<10^-35 metres) nor went bang (for there was only radiation at the time and no medium for sound waves to travel through for some further time to phase-change).
Agreed. It also leads to the analogous picture of an expanding sphere of 'exploda' which inevitably leads to the question of 'what does it expand in to' - a fallacy which took me a while to rid myself of.
 Quote: The three ideas Penrose discusses: Loop Quantum Gravity (Lee Smolin), Cyclic Ekpyrosis in an 11-D universe (Steinhardt & Turok) and his own 10-D view each have their associated apparent 'crazinesses': budding universes inside black-hole event horizons, a fourth space dimension and a conformal map to take conditions at t^-infinity to be identical (to Heisenberg uncertainty and matter distribution effects) to those at t^+infinity.
Nice summary.
 Quote: But the observations of Dark Matter's influence*, COBE, WMAP, distant supernovae and hypernovae (SN2006gy, eta Carinae &c) and the seeming absurdities of QED (light travels every conceivable path, weighted by probability) mean that anything with the remotest chance of being correct has to look a bit crazy, at first. (Reminds me of myself! )
LOL...me too, but if all us science-types are crazy then I demand a recount on the test scores:-)
 Quote: Penrose claims that 'the geometry exists' but it sure looks ouroborotic to me, sometimes... ed.
EXCELLENT word - my vocabulary has today increased by 1
Let me return the favour - Razz, I understand, comes from raspberry as in blowing one....
newolder
Well... Ooops! for the Razz.

P.S. My last "Test score" was ~10 years after our RTA, the Psychiatrist remarked along the lines of, "Well..., these tests aren't really designed for the likes of you." - i mean, what's all that about?

Cheers again, ed.
EanofAthenasPrime
Bikerman wrote:
 Bikerman wrote: You would possibly then be taken seriously if you posted on a science board expressing the opinion that G is not constant.

PostScript.
On reading my last reply back I see that it could be construed as implying that you are/will not be taken seriously on THIS board. That was not my intended point, and it would be rude and unwarranted of me to have said such a thing. To avoid confusion I should clarify the point - I meant that this was probably the reason why you were banned from the physics forum you mentioned earlier.
As regards this board, I try to consider all postings seriously and where that is not possible I normally avoid replying. As you can see from the extent of my postings on this thread, I took your point seriously and set about refuting it.*

*I am glad that you don't seem to have taken this the wrong way - many people confuse vigorous debate with personal rudeness/attack. Where I disagree with a point then I normally attack the point with as much rigour as I can, but this is in a true spirit of scientific debate and reflects the way that professional scientists would (and should) act in similar circumstances. Science is often a matter of attempting to refute ideas/proposals and doing so with some vigour - that is how theory is 'proven'. This should never be taken personally and should never stoop to personal comment, let alone personal abuse or criticism (though obviously it has frequently done so over the history of science because scientists are people too).

thanks man...but if I have learned something from this thread, it is that I am more vague than I originally thought...rofl
Mr_CEO
 Quote: There are too many factors that make up time. You cannot possibly travel down in any axis up to the point zero and then travel beyond zero into the negative. If you assume the zero at position one, then you might do it in case of spatial dimensions. But might not be possible in the case of time. The factors that affect an instant of time are innumerable. It is not just x, y and z. There are other dimensions to it which need to also roll back in time. It is not a question of just moving. It is a question of pulling to gether material of various combinations, gravitational, EM rays and many others have to roll back. At any given point in time (every microsecond) millions of millions of N of energy is being sent out by stars and how do you roll them back. And this energy gets converted into various forms too. Roll back is a myth. Roll forward is also a myth because of the same reason.

I agree. However, we must learn to except the facts of time. One being, Yesterday is no more. That which is past can only be revisited in memory. Second, We can only live in the present because that's all there is. Tomorrow does not exist. There is absolutely no physical proof, anywhere in the universe that shows that there will be a tomorrow. Everyday is only today. The only difference is the name we give today. (i.e. Sunday, Friday, etc.) Simply put, you can’t travel back and there is no future. Therefore, we can only live in the present. I know it sounds strange, but fact is often stranger than fiction. Think about it and you'll understand.

Rvec: Please use the quote tags when quoting
xbcd
I think its possible, you can move it 2d space without the need of the 3d space. so i think you can move in time without the need to move more then XYZ for the first three dimensions and move ur position in time as well without affecting the other upper dimensions. It would simply create an apparent paradox that is solved with the theory that there are multiple realities and that time travel would simply create another alternate reality.
agustin
its possible. I already did it.
DX4Life13
Yes, time travel is very possible IMO. All you really have to do is to find a black hole or just go at the speed of light; go faster and you go back in time. Some might think that going back in time would be the most impossible because of parodoxes. Well, I believe that if you change something in history, when you go back to your time, you reach a parallel universe of what you changed.
Miriah
 Bikerman wrote: The whole idea of time travel begs a deeper question. Why does time travel in one direction only? Arthur Eddington (British Physicist) coined the phrase 'The Arrow of Time' to describe this phenomenon. Nothing that I know of in the fundamental laws of physics treats time as asymmetrical (ie as only flowing in one direction). We are used to time flowing in one direction only - an egg, once broken, does not suddenly 'unbreak' - but explaining why this should be so is a very deep problem in physics.

Does time really flow? What if all time has already happened? It is an uncomfortable thought...but maybe time never really ends as we understand it. Time could go on "forever", and extend back "forever".... Wouldn't we then be able to travel through time at will? This isn't my theory...it is one I read somewhere, but I don't remember where. I probably sound cracked.
Liques
Man may be wonderful trip in the time
busman
Bikerman wrote:
 rshanthakumar wrote: time travel is imaginary. You may not be able to land up in different era and start altering it. But you can 'see' it if you can catch up with the light and you are able to amplify the light rays you caught. Might become a possibility after a century or so. today we have the technology to become invisible though the military is not releasing it out. Same way, travelling faster than light could become a possibility and you might be able to see the light ray that left earth 10 million years back! Yipppy!

I'm not sure what you are talking about here....Time travel is, as we have pointed out, misleading because it implies that there is a commonly agreed time in which to travel - there isn't. If you mean travelling in time with respect to earth, then this is covered in previous postings quite thoroughly.
'Catching up' with light would imply travelling faster than the light which, as has been pointed out, is not possible according to relativity.
I am not aware of any technology which makes things or people invisible and I am pretty sure that the military have no such technology - this sounds like the product of one of the more outlandish conspiracy theory websites.

Have you heard about time-travel through to the future? Like i know haha stupid question what i mean to say is i was watching Sci-Fi Science and one of the physicists was talking about srinking the force of gravity in front of the vehicle and elongating it behind the vehicle. Kinda like a gravitational push-me pull-you haha. In esscence allowing you to move faster than the speed of light once that ratio is high enough.
Bikerman
Yep - there are a few theoretical models which could work.
You don't have to exceed c though..just go really fast.

Example.....if we could travel at 0.99c then we get a time dilation factor (relativity factor, or rf) of (clicks start/run/calc, bungs the figures in and gets) 7.08 to 1.

So if I headed off for, say, 1 year and came back then I would have travelled 12 years into the future here on Earth (2 years for me, 14 years for Earth).

If we could up that a bit - say to 0.9999c then we are up to a rf of 70.
If we could really kick it up - say to 0.99999999c then our rf is 7000 to 1.
busman
 Bikerman wrote: Yep - there are a few theoretical models which could work. You don't have to exceed c though..just go really fast. Example.....if we could travel at 0.99c then we get a time dilation factor (relativity factor, or rf) of (clicks start/run/calc, bungs the figures in and gets) 7.08 to 1. So if I headed off for, say, 1 year and came back then I would have travelled 12 years into the future here on Earth (2 years for me, 14 years for Earth). If we could up that a bit - say to 0.9999c then we are up to a rf of 70. If we could really kick it up - say to 0.99999999c then our rf is 7000 to 1.

Ty for the bottom example i'm not the best with all of the exact mathmatical priciples. Started Triganometry but never got much further haha (Wanting to one day) But the question i kinda ment to say was; say you get over the speed of light with this gravitational warp drive, which in all aspects SHOULD be able to happen, considering you are not actually moving in the traditional sense the way that light moves, wouldn't inherently ,in and of itself, traveling faster than the constant be considered a form of time travel? And if not could you try your best to explain why not (i am awesome at conceptualising just not advanced math and spelling haha)
Bikerman
OK...I'll try.
(I may as well go into full teacher mode and try to go from scratch so don't be patronised if you know most of this already..not my intent)

All these designs (there are a few - links below) rely on moving or distorting spacetime. Einsteins Relativity applies to objects within spacetime but not to spacetime itself. That is why, for example, distant galaxies can recede from us at an apparent velocity much greater than c. What is actually happening is that spacetime is stretching, rather than the galaxies moving. This, incidentally, is why I dislike the image of an explosion to represent the Big Bang - it is completely misleading.
Imagine, instead, a piece of elastic with a pen-mark every 1 cm. Now stretch the elastic and the marks move apart. The marks are not actually moving as such - the elastic between them is stretching. Moreover, each mark will 'see' each other mark recede from it at a velocity which is proportional to distance, just as we see galaxies recede from us according to Hubble's Law.

So we start with ----|----|----|----|----

and at time t(>0) we have ----------|----------|----------|----------|----------|

If you imagine the view from the first mark, then the second mark is receding at velocity x. The third mark is receding at velocity 2x, the fourth at 3x...and so on. The same is true whichever mark you decide to observe from.

OK with that?

Now that is a 2-D model of 4-D spacetime but it illustrates the basic idea.
There is no limit on the 'stretching rate'. In fact we have recently discovered that it is speeding up (accelerating) so things are apparently moving apart quicker and quicker - known as 'expansion'.
The basic model is that our universe IS the Big bang. ie it started at a point and expanded, and is still expanding - like a current bun rising in a hot oven, the currents apparently move apart but actually don't move - the dough (spacetime) stretches giving the appearance of movement.

So the trick for any faster than light (ftl) travel is to play with the dough, rather than move with it. One trick is to curl the dough around, so that you can travel from point A to point B within the dough instantly. The best metaphor i can think of would be 2D rather than the 3D dough. Imagine a flat sheet of paper for spacetime. You want to move from bottom to top (call it 20cm). So the trick is to fold the paper so that the top and bottom come together (simply folding in half will do it, though obviously in 4D this is a tad more complex). Now points A and B are basically in the same place. In Spacetime the same concept is called a wormhole and that would be the first possible method. I don't think it is on, myself, since I believe we are going to find laws which disallow it, but in today's physics it is possible, and I've included a couple of vids on it for more info.

The other method is pushing through the dough. Basically you compress spacetime ahead and expand it behind so that your own spacetime is stationary but it is like a bubble with 'external' spacetime flowing around it. Distant objects now rush towards you as the spacetime (and therefore the space) is compressed and theoretically you could go at any relative velocity - c would not be a limit. This method is correctly called the Allcubierre drive after the guy who dreamed it up.

Now, to answer your question after than massive preamble - yes. It would be time-travel with respect to a stationary reference point, or, in fact ANY reference point within spacetime.

This is obvious if you do a simple thought experiment, though I'll say right now that this is misleading for a deeper understanding, but it is easy to grasp and is therefore useful as a metaphor)

You imagine riding away from earth and looking back at a big clock. If you can go at c then you will always see the clock at fixed time of departure - because you are seeing the photons that bounce off the face of the clock and also travelling at the same speed as those photon. So time is stopped relative to earth. If you could go faster then you would overtake the photons that left before the time of departure...

Now this is wrong in reality and I'll now give a better model for those who want to move on a bit...

The reason the previous model is wrong is because light always travels at the speed of light (bear with me, not as dumb as it sounds) in any frame of reference (that is basically Special Relativity summarised in a single phrase). Since light travels in my frame of reference at c, and we imagine you travelling away from me at, say, half the speed of light, nonetheless my photons must move in your frame at c. The apparent paradox is resolved by varying the relative times of the two frames so that (counter-intuitively) both see the other's clock slow down. To go back to the model above, I see, from my spaceship, the earth clock ticking more slowly, and an earthman with a telescope would see my clock ticking more slowly.
As velocity approaches the speed of light (v->c) the clock ticks slower and slower - as illustrated by the maths earlier - known as the Lorentz factor and quite simply expressed as the square root of (1 minus the velocity squared divided by c squared). DAMN English is so inelegant and imprecise for this stuff.....and the ascii code set is crap for expressions. Hold on whilst I set up an image: OK, here is the Lorentz factor:

Now what happens when v = c? We get 1/0..divide by zero....undefined. Some people simplify that to say that it is zero but what it really means is that you have no frame of reference - you simply cannot construct one, mathematically - and therefore physically, (the maths encompasses many possibility and reality is only one of those possibilities).
See how it is so much easier to talk about in simple maths (nothing complex, not even any calculus) ? There are no words in English or any other natural language - the universe really does speak maths.

Now, to continue, although we cannot form a frame of reference at v=c, now do the maths when v > c.

OK grasshopper, Confuscious he say you are ready to answer own question...the master becomes the pupil and the pupil the master......what happens when the lotus blossom falls faster than the waterfall ?

What happens to the Lorentz factor, and what does that do to the time dilation expression in the last posting) ?

If you want to do some calculations as I used to have to do them when younger, here is a working slide-rule..have fun.

Do you think v>c is possible from the theory (given that the theory is represented in that one equation well enough to decide) ? If not why not and if so what does it require?

This is a very good exemplar of why you cannot really get into physics without maths. Even basic maths will get you some of the way - I can define the Lorentz factor from nothing using nothing more complex than Pythagoras (another posting).
It makes no sense mathematically to talk about a photon having a frame of reference. The deduction from that is that you cannot go from v<c to v=c which is the REAL reason, in this model, that you cannot go at the speed of light. The usually given ones (infinite mass, infinite momentum, infinite length) are not well formed - this is.
Now, your common-sense is going to scream that photons exist therefore they must have a frame of reference. No. This is also a bloody good example of why common-sense must be handed in at the physics reception. There is no requirement for a photonic FOR in physics therefore it is unnecessary for it to have one in order to be 'real' in the ontological sense. I could say imagine a photon, appears at the speed of light (doesn't accelerate TO c) and in no local-subjective time is absorbed. Literally no time. Doesn't matter how far it goes - right round the universe if you like. Zero time. Is it therefore sensible to talk about a frame of reference? Nope. So anyone who tells you that a photon would 'see' this or that is talking bollox because they are stuck with my first model and don't really understand the theory - which final statement is a third lovely example of why lies-to-children teaching (ie using simple metaphors) is a two-edged sword.

(in order of increasing technicality)
http://www.youtube.com/watch?v=hriqvP-RVxc
http://www.youtube.com/watch?v=sxl6TOLxvuI
http://www.youtube.com/watch?v=iJZXDEUOao0
http://en.wikipedia.org/wiki/Alcubierre_drive
http://en.wikipedia.org/wiki/Krasnikov_tube
http://www.nasa.gov/centers/glenn/technology/warp/warp.html
(and just for fun and because I LOVE the drum sound on this)
http://www.youtube.com/watch?v=ZM4R9x6nS_c
busman
No dude you did a good job explainin your first point pretty damn well. Kinda like a tesseract from A wrinkle in Time (and i know thats not what an actual tesseract is, just using it as a point of referance) Its equivelent to having your papers edges brought together as opposed to having to walk the whole way- hence a "wrinkle in time". Ya totally get what your getting at there. The second one got a lil more complicated but i get the general direction of what you're stating and how we'd go about getting there. In all honesty i just don't know what type of material is going provide the power and/or cause that constant wrinkle... Makes me sad becuase as a kid i always wanted to be on the USS Enterprise hahahaha.

And v (velocity i hope haha) can definitly bring itself above the constant in an unlitteral sense (the whole gravity bubble) but idk how it would in the terms of traditional velocity...? Doesn't seem to follow the theorems we have now. Because if v>c, v becomes c thefore making v=c at top speed right?
busman
Hey just for reference i'm working from only a HS Education btw. Not to say that i'm in any way stupid as we could go over drumming and i could name every technique etc but just when it comes to the most advanced area's of other subjects other than the historical sciences or animal sciences it takes me a good bit longer than usual to have to research it on my own and re-learn some of it then try to process it and once again try to understand it. Things like History, the study of the taxa of animals or music can be read upon and intuitively learned where things like even a basic understanding of physics and most sciences' requires a deeper knowledge of the understanding involved in each of their respective fields so sorry if i come across as ignorant, i'm really trying! haha
jackbreat
According to my knowledge it is not possible . Because it speed is to first . We are know that the speed of light , so it can't be possible.
camille054
I think that Time Travel is impossible......

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