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.
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
^^^^ 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? 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.
| _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. | 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.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.
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.
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. |
| _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 
| 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.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
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.
To me, it seems noteworthy that we percieve time progressing in the direction of increased entropy.
| 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?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?
| 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?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.
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.... 
Is there any vehicle or weapon that can achieve the speed of light?
| _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.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!
| 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.There is a material/object now that can make whatever is inside invisible to certain microwave wavelengths, I think.
| 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/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?
| 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)Wasn't the chronotron invented by star trek?
Chronotron are fictional particles used in science fiction, it has no basis in real physics
What about another theory?
If you make the Earth rotate backwards somehow, time can go backwards?
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
| 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. | 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. | 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.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)
| 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. | 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 ? | 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.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.
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 | 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.htmthe 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. | 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.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. | 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 ? | 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. | 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. | 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.. | 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 | 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. | 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 | 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.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.
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.
| 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. | 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 ? | 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'.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.
| 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 | 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]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.
| 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 wasand 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
| 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. | 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. | 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)
Last edited by Bikerman on Mon Apr 23, 2007 6:59 pm; edited 1 time in totalOops, I didn't mean to steal your thunder | 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:-)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
| 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.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.
| 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? | 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.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.
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)
time travel...i think it should be impossible
it only show in comics or a faction thing
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!
| 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.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?
| 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. | 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 ? | _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. | 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. | 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. | 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... |
| 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?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...
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.
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.
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)
| 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. | 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.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, h