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'Before' the Big Bang





Bikerman
The recent Horizon program is recommended watching for those interested in Cosmology - particularly the Big bang theory:
http://www.bbc.co.uk/iplayer/episode/b00vdkmj/Horizon_20102011_What_Happened_Before_the_Big_Bang/

(I will try to download the programme and make it available to non-UK viewers later).
Ankhanu
Thanks. I look forward to the upload.

Before the Big Bang is such an interesting topic; I was listening to a radio program on our national public broadcaster (CBC) in the summer that was talking about the difficulty of the topic, fascinating stuff. I'm not a physicist, but I still enjoy it Wink
Bikerman
I'm currently writing a piece on the subject for another forum. I'll post a link to it when I've finished.
I should have the download of the Horizon program finished later tonight and I'll post it up when complete (my broadband is playing silly buggers at the moment).

In the meantime you might find the following lecture by Roger Penrose interesting. It isn't simple and you do need a bit of basic physics to follow the details:
http://www.newton.ac.uk/webseminars/pg+ws/2005/gmr/gmrw04/1107/penrose/
Ankhanu
Thank ya. I'll take a listen on Thursday or Friday... I'm using cellular for my connection right now, it's slightly slow and I don't have a tonne of bandwidth until my account ticks over in a couple days.

I do have a light physics background, but the nature of the Big Bang and quantum mechanics weren't really part of what I did; relativity was about as far as I got Smile All the same, interesting stuff.
Bikerman
Horizon Program on 'Before the BB'
HERE
Alerrandre
it is amazing,before the big bang was DARK...
hillio
It still amazes me how anyone with any type of education at all, can believe the big bang theory. I would be quicker to believe that our universe was created by little green men from another, different universe than the nonsense set forth in the bb theory.
ocalhoun
hillio wrote:
It still amazes me how anyone with any type of education at all, can believe the big bang theory.


Because it explains a lot of the evidence we see, and often does so when no other theory can.
Bikerman
hillio wrote:
It still amazes me how anyone with any type of education at all, can believe the big bang theory. I would be quicker to believe that our universe was created by little green men from another, different universe than the nonsense set forth in the bb theory.

And I suppose you consider yourself educated? Perhaps you could favour us with your 'educated' explanation of just which parts of the theory are nonsense, and why?
Alerrandre
Crazy,everything was dark,and than comes the explosion,shit....


Who will belive in that %$#@!
ham65
Everything dark,and after the dark and after the explosion everything was brighter,it is the most stupid ideia i have seen.

LOL
Ankhanu
My cellular connection has been running faster than it was when this thread was created, and I've just gotten around to watching this. What a great program! Thanks for the mirror, bikerman, I thoroughly enjoyed it.

The idea around the 38min mark of the death of the universe birthing universes as scale and time become meaningless is utterly brilliant! it absolutely stirs the imagination.

Dr. Kaku's defining of nothing holds interest as well. I have some mixed feelings about Kaku based on other programming I've seen with him. He's definitely an interesting person with interesting ideas, but I'm not always convinced of their validity. He definitely challenges standard ideas though.

Black holes birthing evolving universes? I'm pretty sure I've come across this idea a few times in the past. It has certain merits, but, in my mind, implies diminishing, finite energetics in each offspring universe, with perhaps reduced energy within the parent universe. It leads to some pretty heavy questions and revisions of thermodynamics.
Bannik
what people fail too realise is how little we know of the world, remember the world also works on quantum level - for all we know the universe has always existed in a small quantum level and the big bang is simply an event on that level that made the universe - just my opinion and it sort off worthless cause I am stupid
Crying or Very sad
timetorock
watch "Curiosity" on Discovery channel every Mondays . That might give you some idea regarding your query. More specifically watch its 1st episode "Did God Create the Universe"? It might just clarify you with what you wanted.
Ankhanu
timetorock wrote:
watch "Curiosity" on Discovery channel every Mondays . That might give you some idea regarding your query. More specifically watch its 1st episode "Did God Create the Universe"? It might just clarify you with what you wanted.


Wanna give us a synopsis of the show??
therimalaya
Is Big Bang really occurred??Or is there any other starting? If it has occurred from where that heavily dense tiny particle came from? These all are mess...
Bikerman
If you have a serious question then fine.
This question - where did the 'first' thing come from - is frequently cited by religious folk as evidence for God. They exclude God, of course, on the spurious grounds that God wasn't created and therefore needs no creator - a piece of circularity that would be funny were they not serious.
The simple fact is that it is an appeal to ignorance.
You make the 'common sense' assumption that matter and energy are conserved - because in our 'common experience' they are. At t=0 the theory of General Relativity goes quack quack and collapses into an infinitely sad heap. There are many interpretations (aside from the one that tells us that GR is almost certainly incomplete). I won't bore by repeating them, but to summarise:
it is possible (and it happens all the time) for 'nothing' to produce 'somthing'.
Take the emptiest space you can. Make sure there is no molecule or atom left. You still have 'something'. Virtual particles popping in and out of existence whilst nature has her back turned. Nature does like energy and mass to balance, but she isn't quick enough to spot the fast dealing. A bit not nothing suddenly sprouts a plus 1 and a minus 1 (a positron and an electron, for example), which then smash together and annihilate, balancing the books before mother nature looks. So out of nothing you get something, as long as the somthing adds up to nothing in the end. 0 = -1 +1
So now imagine that mass and energy are the +1 - where is the -1? Well, that would be gravity.......

Anyway - this is just a simple outline of one possible theory...there are many others.
loremar
That's a good explanation Bikerman. I didn't knew it has anything to do with antimatter. I just knew that in Quantum Mechanics it's possible that a particle can pop out into existence, so why not a whole universe, and also the possibility of several universes popping out.
_AVG_
I think that the core issue I have with the big bang theory is the 'something from nothing' phenomenon. I know there are many ways that something can come from nothing, and for one of the most elegant ones, I recommend the youtube video "A Universe from Nothing". Nevertheless, there are some interesting philosophical arguments against this (forget conservation of matter or energy, just look at reason):

Suppose something is brought into existence from nonexistence. If nonexistence is defined as an absolute void, then creation could not exist either so something ought to have brought creation into existence and then that something ought to have been brought into existence. And so on ad infinitum.

Although I like this argument, like any philosophical argument, there will be problems associated with it - I think that the main problems one could find here are with the definitions of existence, nonexistence and creation. (And not to mention the paradox of an absolute void: if nothing exists, then even nothing is nonexistent)

Anyway, I am still not completely against the big bang theory, because it could very well be adjusted so as to solve the 'something from nothing' problem: that the universe has existed forever and the big bang was just a MAJOR alteration in its state, and that this alteration was such that it doesn't matter what the state of the universe was before it.
Ankhanu
_AVG_ wrote:
I think that the core issue I have with the big bang theory is the 'something from nothing' phenomenon. I know there are many ways that something can come from nothing, and for one of the most elegant ones, I recommend the youtube video "A Universe from Nothing". Nevertheless, there are some interesting philosophical arguments against this (forget conservation of matter or energy, just look at reason):

Suppose something is brought into existence from nonexistence. If nonexistence is defined as an absolute void, then creation could not exist either so something ought to have brought creation into existence and then that something ought to have been brought into existence. And so on ad infinitum.

Although I like this argument, like any philosophical argument, there will be problems associated with it - I think that the main problems one could find here are with the definitions of existence, nonexistence and creation. (And not to mention the paradox of an absolute void: if nothing exists, then even nothing is nonexistent)

Anyway, I am still not completely against the big bang theory, because it could very well be adjusted so as to solve the 'something from nothing' problem: that the universe has existed forever and the big bang was just a MAJOR alteration in its state, and that this alteration was such that it doesn't matter what the state of the universe was before it.


The thing is, Big Bang doesn't state "something from nothing"; it freely admits "Something from... I don't yet." It doesn't address what was or wasn't there, it operates from "ignition" onward. It explains the origin point and expansion.
The way you're looking at it is akin to saying "I don't believe in evolution theory because it doesn't say how life began." Like Big Bang, evolution theory only addresses an understanding of processes that occur after a particular point; in this case, once we have life, evolution explains the diversification of life. In Big Bang, we see how our universe came to exist in the state it is now, with the understanding that there is an "origin" point. Neither theory addresses the formation of those initial conditions or what might have existed before hand. These explorations may become part of the theory at a later date, as more knowledge is gleaned, or they may be their own theories linked to the existing theories... we can't properly know until we expand our understanding of, well, reality.

Accepting or rejecting theory on the basis of whether or not it can address questions it doesn't address is kind of silly. Let them stand on their ability to explain and predict what is within their scope.
Bikerman
Look at it another way.
The Big Bang could be simply a quantum fluctuation (Heisenberg on a universal scale).
Now this doesn't involve 'something for nothing'. Even if we admit the physical existence of 'nothing' - and most people don't really understand that this is not at all the same concept as empty space (which is clearly 'something' since it can be measured, and is, in any case, teeming with energy), then we can explain the universe without 'violating' conservation law - even the half-assed version of it usually cited in these cases.
In QM energy can be 'borrowed' for a tiny period, so long as it is 'paid back' promptly. Imagine Mother Nature standing guard over empirical reality, rolling-pin in hand. Now, Billy-Whizz, having fallen on hard times since losing his job at the Beano, has turned criminal. He is the fastest thief ever. He zooms up to Mother Nature and nicks her purse, and does it faster than she can see - say a 50th of a second. In that instance he has her 'energy' (ie her dosh) and can do what he likes with it. Trouble is, he must return the dosh within the next 50th of a second, or she will clonk him with the rolling pin.
That is a bit like virtual-pair producton in quantum physics. You have 'nothing' - but only as the aggregate state. If you really dig-down then what you find is particles and anti-particles popping in and out of existence continually. The energy needed is 'borrowed' for the tiny period they exist, before the two particles collide and mutually annihilate - at the same time 'paying back' the original energy.

Now, let's apply that to the universe. We have an aggregate zero - nothing. For a tiny period of time (and the lifetime of our universe might easily be such a tiny period, measured on a different clock) a 'virtual pair' appears. In our case the pair consists of energy/matter for one (call it positive) particle and gravity for the anti-particle. For a brief span they exist together, before they eventually annihilate each other, returning the aggregate energy to zero.
Tuvitor
Great posts Bikerman...

I read in a recent(ish) Pop Sci magazine that perhaps our universe exists in another universe's black hole, and that the black holes in our universe may house whole other universes. What are your thoughts about that idea?
Bikerman
Tuvitor wrote:
Great posts Bikerman...

I read in a recent(ish) Pop Sci magazine that perhaps our universe exists in another universe's black hole, and that the black holes in our universe may house whole other universes. What are your thoughts about that idea?
I quite like Lee Smolin's version of that. His basic hypothesis is that Black Holes are 'selected for' in Universe production because they are, in fact, gateways to other universes where the physical constants may or may not be the same. This means, of course, that Universes in which the physical constants are just right for the production of black holes will proliferate. As a byeproduct, the conditions necessary for black holes just happen to be those which are also required (as far as we know) for life.

There is a pleasing symmetry to this hypothesis, since it takes evolutionary theory are REALLY runs with it Smile
ocalhoun
Bikerman wrote:
As a byeproduct, the conditions necessary for black holes just happen to be those which are also required (as far as we know) for life.

Uh... wouldn't selecting for black holes (mainly) just maximize the gravitational constant?

...Don't see how that's particularly beneficial for life...
Sure, life needs some gravity so that supernovas occur to spread the heavy elements, and so that planets can form... but too much gravity seems like it would be harmful for life.
Bikerman
No. The schwartzchild radius is defined as rs = 2GM/c2
Increasing G would increase the radius correspondingly.

Besides, BHs are formed from matter. If you diddle around with the constants then matter has to be able to form in order to produce black holes....
Black holes require:
  • Rapid enough expansion after the Big Bang to allow for a transparent universe with stable atoms.
  • Stable enough subatomic particles to allow for stable atoms.
  • Subatomic forces that are neither so strong they do not allow nuclei to split, nor so weak they do not hold nuclei together.
  • A gravitational force that is neither so strong that it halts the Big Bang or attracts all matter into a lump, not so weak that it can hardly hold any matter together.


http://arxiv.org/abs/gr-qc/9505022
http://arxiv.org/pdf/gr-qc/0306095.pdf
ocalhoun
Bikerman wrote:
A gravitational force that is neither so strong that it halts the Big Bang or attracts all matter into a lump, not so weak that it can hardly hold any matter together.

Still, within that range, it would tend toward the strongest possible gravitational force, no?
(ie, say the scale of all possible values was from -100 to 100, with 100 being the strongest attraction and -100 being equally strong repulsive force. And then suppose that black holes could only form under values between 30 and 70. Wouldn't the universes then tend towards having it be 70?)


Or really, never mind... there's another issue that supersedes that... They could only be 'selected for' if the child universes inherit (at least some of) the properties of the parent universe.
...But (unless you have a large initial number of universes), it also doesn't work if child universes inherit the exact same parameters of the parent universe either. In that case, it wouldn't trend toward anything, just an endless regression of identical universes... assuming the first one produced at least one black hole.

So, by what mechanism does a child universe inherit some -- but not all -- the properties of the parent?
What determines which properties are inherited, and to what degree they differ?
Bikerman
No it wouldn't. In fact Smolin shows that our universe is just about optimum. Increase G by very little and no Black holes.

Smolin proposes that the fundamental physical constants are the inhernited traits and that they vary naturally (owing to quantum events in the singularity), thus providing the necessary imperfect but hi-fidelity copies needed for any evolution.
D'Artagnan
how can something happen before time?
ocalhoun
D'Artagnan wrote:
how can something happen before time?

I'm not sure causal relationships are dependent upon time.
(Looking at quantum physics, we can find a few examples of cause/effect relationships where the cause and effect seem to happen at exactly the same time... and even instances where the effect is (slightly) earlier in time than the cause.)

It would be meaningless to look before (timewise) time began... But perhaps meaningful to look at a chain of cause-effect relationships that might extend beyond the beginning of time.

(ie, while it may be meaningless to ask what happened before the big bang... it might be more meaningful to ask what caused the big bang... and what caused that, and so on.)
_AVG_
ocalhoun wrote:
D'Artagnan wrote:
how can something happen before time?

I'm not sure causal relationships are dependent upon time.
(Looking at quantum physics, we can find a few examples of cause/effect relationships where the cause and effect seem to happen at exactly the same time... and even instances where the effect is (slightly) earlier in time than the cause.)

It would be meaningless to look before (timewise) time began... But perhaps meaningful to look at a chain of cause-effect relationships that might extend beyond the beginning of time.

(ie, while it may be meaningless to ask what happened before the big bang... it might be more meaningful to ask what caused the big bang... and what caused that, and so on.)


I've recently developed an interest in this kind of "violations" of our intuition about causality. Are there any other instances of such "violations" which you know of? I've recently read about advanced potentials in electromagnetism as well, according to which the future state of the potential affects its present state. I'm interested in any other instances in which the so called "effect" precedes the cause. I'm not sure if this occurs in Relativity as well.

Guys, please help me in this matter if you know anything at all about this. Any reply will be appreciated.
kelseymh
_AVG_ wrote:
ocalhoun wrote:
D'Artagnan wrote:
how can something happen before time?

I'm not sure causal relationships are dependent upon time. [...]


I've recently developed an interest in this kind of "violations" of our intuition about causality. Are there any other instances of such "violations" which you know of? I've recently read about advanced potentials in electromagnetism as well, according to which the future state of the potential affects its present state.


You should be carefully about attributing physical reality to Green's function calculational tricks Smile The use of advanced and retarted potentials is a terrific way to make otherwise complicated and ugly computations tractable.

For time-varying charge distributions, the retarded potential (which takes into account the propagation of a charge movement to a distant point) is causally correct and necessary. In a many-body system, where the movement of charges affects the overall field, which itself affects the movement of the charges, a way to simplify the iterations is to compute both retarded and advanced potentials, then take an average of the two (e.g., Wheeler-Feynman absorbers).

Quote:
I'm interested in any other instances in which the so called "effect" precedes the cause. I'm not sure if this occurs in Relativity as well.


You can certainly do non-causal calculations in relativity, but they don't have physical reality. Specifically, any superluminal "influence" is non-causal because you can find a reference frame in which the temporal relationship is reversed.[/quote]
Ankhanu
I just watched this video about vacuum and quantum activity that's somewhat accessible and interesting, that could help people understand some of the ideas in the video that started the thread.
nevelis
It looks like that before the big bang the universe shrank into a point - a pulse, a cycle of the infinity. The most interesting moments for physics are the last and the first moments of the cycle.
zhybsc
thinks , it is very interesting.
Radar
What comes before the Big Bang? My response to that is that your'e kind of asking the wrong question. The Big Bang was the beginning of time, as I appreciate it. Yes, I'm here not subscribing the idea of a previous Big Crunch.

I've heard an explanation for how, in terms of physics, you can have an empty vacuum, and then random... events, I'm not sure what the best word is, can cause things to come into being, and then potentially the primordial atom, and so on.

I'm not a fan of that idea, but I have a bigger problem with it philosophically. Where did the vacuum come from? If you have nothing - no, not a vacuum, but actually nothing - then you get more nothing. You can't get something from nothing. As a Christian, I believe that God was there, and God created everything. How did God exist? God is self-existent. He just is. Hard to wrap your mind around maybe, but I think in any chain of logic, you have to say that something started it all, and God sounds like a far more satisfying answer to me, than a quantum vacuum.
loremar
Radar wrote:
I'm not a fan of that idea, but I have a bigger problem with it philosophically. Where did the vacuum come from? If you have nothing - no, not a vacuum, but actually nothing - then you get more nothing. You can't get something from nothing. As a Christian, I believe that God was there, and God created everything. How did God exist? God is self-existent. He just is. Hard to wrap your mind around maybe, but I think in any chain of logic, you have to say that something started it all, and God sounds like a far more satisfying answer to me, than a quantum vacuum.

That sounds like a good topic in Philosophy & Religion section.
xikaouj
浑沌(hun dun) ,we chinese call the universe before the big bang.
Ankhanu
xikaouj wrote:
浑沌(hun dun) ,we chinese call the universe before the big bang.

Can you explain the Hun Dun idea, and what evidence there is for it?
vaishnavsm
I think that before the big bang, there was a different universe, which, after the big crunch there, contracted both space and time to an "infinitely" small point.

This *is* possible, because all the mass would have been converted into energy and energy doesn't occupy space.

Of course, this is my theory, and I'm only 14... so that could be wrong Very Happy .[/b]
Bikerman
It isn't a bad theory (especially for a 14yr old Wink but it has some problems.

Firstly I don't see how energy could exist independent of space for it to exist in. Secondly if we posit that the 'pre-big bang- state was a big crunch then the obvious question is - why is it different this time? If we are the result of a previous universe which 'crunched' then why do we observe that our universe is flying apart rather than also 'crunching'?
vaishnavsm
Quote:
Firstly I don't see how energy could exist independent of space for it to exist in


Energy doesn't require its own space.. I can overlap other kinds energy and exist in harmony
EDIT: It does require space.. but that 'space' can be 'infinitely' small..

Quote:
Secondly if we posit that the 'pre-big bang- state was a big crunch then the obvious question is - why is it different this time? If we are the result of a previous universe which 'crunched' then why do we observe that our universe is flying apart rather than also 'crunching'?


That's easy..
Either:
A universe is dynamic. It can produce different things every big bang. So there may have been more anti-matter this time, so that the mass of the universe is less..

OR:

Wait for it..... Wat for it... Wait for it...
It's not time for the destruction of the universe yet Razz

Quote:
It isn't a bad theory (especially for a 14yr old Wink but it has some problems.

Thanks Very Happy
Bikerman
Energy has wavelength...yes? So how do you get energy of wavelength L into a space with dimensions < L ?

On the second issue - clearly the total mass-energy in our universe would have to be the same as the total mass-energy before the crunch, yes? Producing more antimatter would simply change the balance - more energy less matter but the same overall total, yes? Given that gravity operates on the total mass/energy then how could this universe differ, in terms of expansion, from the pre-crunch universe?
vaishnavsm
Quote:
Energy has wavelength...yes? So how do you get energy of wavelength L into a space with dimensions < L ?


First, not all energy has wavelengths, only electromagnetic waves. i.e light, visible or not..

Second, The energy of wavelength L cannot fit into a space < L... but the space still exists. When a part of the space-time fabric, say a, and area of the grids of a, say b, gets compressed, so does everything in it..

ie,
Take |L| as magnitude of the wavelength and |Z| as the 'area' of space time.
Then, in
|Z| = |L|*x
x can change, but,
|L| : |Z|
Does not. Very Happy

Quote:
On the second issue - clearly the total mass-energy in our universe would have to be the same as the total mass-energy before the crunch, yes? Producing more antimatter would simply change the balance - more energy less matter but the same overall total, yes? Given that gravity operates on the total mass/energy then how could this universe differ, in terms of expansion, from the pre-crunch universe?


Simple, Gravity does effect the total mass-energy, but energy is affected comparatively less.
For example, think that in the previous universe, there was *NO* energy. Then the big crunch would occur faster..

The universe is just ~ 14 billion years old.. let it live Razz

Now comes the real question... where did the universe come from?
Did it just exist?
or maybe not...

Oh god... why are there soo many 'infinities' it the universe?
Bikerman
Can you tell me what other types of energy you would expect to find after a BB?

I think volume might be better than area here. As spacetime expands or contracts then yes, I agree, the contents would go with it.

Energy is affected less? Really? I thought Einstein had shown that energy and mass are simply two ways of looking at the same thing - interchangeable by multiplying/dividing by c^2?
Are you saying that the effect of gravity on 1 gramme of matter is more than on 1/1000*c^2 joules of energy?
vaishnavsm
Quote:
Can you tell me what other types of energy you would expect to find after a BB?


I'm not really sure... maybe quantum particles of some kind.

Quote:
I think volume might be better than area here. As spacetime expands or contracts then yes, I agree, the contents would go with it.


The space-time fabric is shown mostly as a 2d surface.. but we know the universe is 3d. If we take space-time to be a '3d surface', then we also take it that the universe is in fact 4 dimensional..

So, I used area.

Quote:
Energy is affected less? Really? I thought Einstein had shown that energy and mass are simply two ways of looking at the same thing - interchangeable by multiplying/dividing by c^2?
Are you saying that the effect of gravity on 1 gramme of matter is more than on 1/1000*c^2 joules of energy?


I agree.. But energy is less concentrated than matter. Gravity works better on more dense things. Less dense things tend to float away.

Very Happy
vaishnavsm
Now for answers to earlier posts, according to me.

Quote:
I'm not a fan of that idea, but I have a bigger problem with it philosophically. Where did the vacuum come from? If you have nothing - no, not a vacuum, but actually nothing - then you get more nothing. You can't get something from nothing. As a Christian, I believe that God was there, and God created everything. How did God exist? God is self-existent. He just is. Hard to wrap your mind around maybe, but I think in any chain of logic, you have to say that something started it all, and God sounds like a far more satisfying answer to me, than a quantum vacuum.


Hmmm... That's not the subject here. If god exists or not, the universe was never 'nothing'.
There was always energy, matter or both existent in the universe. Also, vacuum doesn't "come from" anywhere. This is just a name given to a place devoid of stable matter (By stable, I mean matter which isn't a quantum mixture, or things composed of electrons, protons, neutrons, etc). Actually, vacuum does have quantum particles all over. They appear and disappear in instants.

Check this: http://phys.org/news/2012-04-fastest-random-silence.html
Its a random number generator that works on this.
Bikerman
I think I'm seeing some fundamental misconceptions here. I'm trying to tease out what you think rather than just go into diactic mode in order to see if your view seems consistent to me. It is almost so, but here are the problems I see.
Does density REALL mean that gravity will work 'more'? No. It means that local reoions of high gravity will form but that over the whole piece gravity obviously stays the same. Local regions would have to be unimaginably massive to affect universal expansion - in fact I don't think that idea flies at all.

To use an analogy which I think might appear favourable to you.....if we have a million gallons of light stuff or a gallon of stuff a million times denser, will both necessarily 'gather' via the action of gravity (in the absence of other forces). Answer - yes. So if there ARE other forces - lets take expansion to be a property of space - the cosmological constant solution - then would a small dense universe be more likely to be gravity bound that an energetically identical universe composed of more, lighter, components?

It is an interesting thought experiment, but I'm seeing a 'NO' as the answer and I'll leave space for YES before taking it further.
Bikerman
I'd also like to reiterate the point that we are NOT doing theology here and I won't allow any such discussion, since it would be in the wrong place. Christian or not has no relevance and is probably better left out entirely. Science please, not faith, lack of it, or discussion thereof. Save that for P&R in which forum it is always welcome.
kelseymh
vaishnavsm wrote:
Quote:
(From Bikerman:) Can you tell me what other types of energy you would expect to find after a BB?


I'm not really sure... maybe quantum particles of some kind.


So, what do you think you mean by this? All particles are "quantum", and all of them obey the same physical laws we all understand, including special and general relativity, including mass-energy equivalence.

Quote:
Quote:
(From Bikerman:) I think volume might be better than area here. As spacetime expands or contracts then yes, I agree, the contents would go with it.


The space-time fabric is shown mostly as a 2d surface..


You seem to be confusing didactic presentations -- constructed in order to illuminate some specific point, or simplified in order to be understandable to the viewer -- with actual reality. Of course we show cartoons of spacetime as a 2D surface, because otherwise we wouldn't be able to easily make a cartoon of it at all.

Quote:
but we know the universe is 3d. If we take space-time to be a '3d surface', then we also take it that the universe is in fact 4 dimensional..

So, I used area.


And Bikerman properly corrected your misconception.

Quote:
Energy is affected less? Really? I thought Einstein had shown that energy and mass are simply two ways of looking at the same thing - interchangeable by multiplying/dividing by c^2?
Are you saying that the effect of gravity on 1 gramme of matter is more than on 1/1000*c^2 joules of energy?


I agree.. But energy is less concentrated than matter.[/quote]

Under what conditions? Energy may be more or less "concentrated" (by which I guess that you mean density) than matter. Where I work (the SLAC National Accelerator Laboratory), collisions of electrons and positrons produce momentary energy densities comparable to that of nuclear matter. At the RHIC accelerator at Brookhaven or at the LHC, collisions of protons or heavy nuclei produce energy densities far in excess of those found in neutron stars.

Quote:
Gravity works better on more dense things. Less dense things tend to float away.


Not even close. Gravity works equally well on everything. "Less dense" is a obviously relative term, and things only "float away" when they are immersed in a substance more dense than themselves. Helium "floats away" when it is surrounded by air or water. You would float very nicely if immersed in mercury.
vaishnavsm
Well, I guess I have alot more to learn... Embarassed Sad

Quote:

So, what do you think you mean by this? All particles are "quantum", and all of them obey the same physical laws we all understand, including special and general relativity, including mass-energy equivalence.


by quantum particles, I meant free floating Quanta. No protons, no electrons, no neutrons, heck not even quarks.


Quote:

You seem to be confusing didactic presentations -- constructed in order to illuminate some specific point, or simplified in order to be understandable to the viewer -- with actual reality. Of course we show cartoons of spacetime as a 2D surface, because otherwise we wouldn't be able to easily make a cartoon of it at all.


I have doubt here...
If space-time is like a 'liquid' that bends away if there are heavy objects near it,
and given that black holes make the space-time around them a singularity (extend to infinity)
What about the space-time in the other directions?
Then, will a black hole, no, any singularity will be 'Separated' from space-time?
Bikerman
According to Hawking (I think, from memory) a naked singularity can never be 'exposed'.

Don't you mean 'bends towards' for your liquid analogy. I'm fairly sure that Spacetime geodesics bend towards mass (thus producing the 'attraction' of classical physics).
I don't think the second 'grant' is going to be granted either. It doesn't have to stretch to infinity to produce a gravity-well from which light cannot escape, if I remember correctly. I'm pretty sure you can construct such a gravity-well without dickering much with spacetime at all (this notion of stretching it troubles me as an image because that's how the expansion is best pictured. I picture spacetime around a blackhole moving faster and faster as you approach, rather than stretching.
Michael will be more help than I Can be here - I'm only an amateur interested autodidact, not a physicist.
As for 'other directions', well spacetime in relativity has no other directions - 3 dimensions of space, one of time. If you mean string theory, m theory or super symmetry theories in general then the question would be what happens to the Calabi-Yau manifold I presume - the bit where the extra 6 dimensions are twisted up at the infinitesimal end of the scale (but even that is saying possibly something without meaning since I've been ploughing through a text which shows how scale itself - big and small - begin to lose meaning in some string scenarios). String theory is still too messy for any amateur of my abilities to get much purchase on - largely because the physicists haven't really got a great grip either - the maths is fiendish and a lot of work in the field seems (to me as ignorant onlooker) mostly concerned with mathematically eliminating possibilities to try and narrow down what they can predict with any hope of being right...
I've read Greene - and enjoyed him, but all his enthusiasm hasn't yet fired me on the theory - maybe I'm just a cynic Smile

In general I stick with the 'mass distorts spacetime' model, so 'infinite' mass causes a big distortion which we normally picture as the indents in the rubber sheet. A black hole doesn't, I believe, require an infinitely 'deep' hole, just one with sides sufficiently curved to keep geodesic for light from escaping. That is not to say it doesn't actually 'stretch' spacetime to breaking. Smolin has theories on that sort of line with his 'universe spawning' model.
Bottom line is like most of modern physics you can only analogise or draw metaphors to a point. Ultimately spacetime isn't a liquid, or a solid, or anything material, so any analogy breaks at the point to which you are trying to deploy it here and you need the maths. I have taught myself enough to do the basic GR stuff (slowly, and not always without error) and I've concluded that the only way to really 'understand' in any kind of way in which that word makes sense to me, is mathematically. It means there's lots I'll never have a real grip of - my maths has expanded, but it us being retarded by the gravity of age and time to an almost Hoylesian 'steady state'.
kelseymh
vaishnavsm wrote:
Well, I guess I have alot more to learn... Embarassed Sad

Quote:

So, what do you think you mean by this? All particles are "quantum", and all of them obey the same physical laws we all understand, including special and general relativity, including mass-energy equivalence.


by quantum particles, I meant free floating Quanta. No protons, no electrons, no neutrons, heck not even quarks.


Can you please provide a citation for that term? I'm a professional particle physicist, and I have never heard of it before, and have no idea what you mean by it. An electron is a "free floating quantum", so is a proton, so is a photon.

Quote:
You seem to be confusing didactic presentations -- constructed in order to illuminate some specific point, or simplified in order to be understandable to the viewer -- with actual reality. Of course we show cartoons of spacetime as a 2D surface, because otherwise we wouldn't be able to easily make a cartoon of it at all.


I have doubt here...
If space-time is like a 'liquid' that bends away if there are heavy objects near it,
and given that black holes make the space-time around them a singularity (extend to infinity)
What about the space-time in the other directions?
Then, will a black hole, no, any singularity will be 'Separated' from space-time?[/quote]

What do you mean by "in the other directions"? When the flat Minkowski spacetime is distorting by mass/energy (what we call gravity), that distortion is in all directions. The primary component is radial, and the distortion decreases with distance from the source (just as Newton discovered). But there are still distortions from flatness in the azimuthal and polar directions.

For masses you're familiar with, like the Earth, those components are extremely hard to detect (look up "Gravity Probe B" or "LAGEOS" for details). For a black hole, the other distortions get large as you get very close to the event horizon. At the event horizon, the metric "flips," such that the time component corresponds to what you would call "radial" in Newtonian mechanics, which leads to some weird physical effects, and some complicated mathematics. Look up "Schwarzchild metric" for details.
diwasblack
what was happening before big bang.................................................................................................


frankly nothing..... universe was at singularity the time had not stared and moreover the universe was just the ball of heavily compacted area of pure energy...............well that what the scientists say well since noone really knows what actually happened.... but looking at the present condition of today's universe we can assume it...
Bikerman
If you really want to boil your noggin - and possibly learn something - then try Penrose at the link below.
http://www.newton.ac.uk/webseminars/pg+ws/2005/gmr/gmrw04/1107/penrose/frames.html

It is speculative, but Penrose is never boring and, IMHO, never stupidly wrong about the science....
kelseymh
diwasblack wrote:
what was happening before big bang.................................................................................................

frankly nothing.....


How do you know? Or is that your own assumption? You may wish to look up (e.g., in Wikipedia) terms like "eternal inflation", "bubble universe", and "multiverse." There are scientifically valid cosmological models which contradict your assumption.

Quote:
moreover the universe was just the ball of heavily compacted area of pure energy


That's a popular misconception, made popular by poor explanations of cosmology Sad The Universe at the "time" of the Big Bang was just as "big" as it is now, in the sense that the cosmological coordinates ran to infinity just as they do now. The difference is that at that time the scale factor a(t) was extremely small. As a consequence the energy density, and therefore temperature, of the Universe was extremely high.

Quote:
well that what the scientists say well since no one really knows what actually happened.... but looking at the present condition of today's universe we can assume it...


Looking at the present and past conditions of the Universe we can infer the early state. Inference and assumption are not equivalent. An assumption is something you believe without evidence (either religiously, or to give you a starting point for deduction).

An inference is a conclusion you draw from evidence and observation -- if I ask you to pick a card from a deck, then go through the deck to find which card is missing, I can infer that you are holding the missing card, even though I have not seen it in your hand.

We (cosmologists) can infer the initial conditions of the Universe by observing the current distribution of matter, by observing the cosmic microwave background (including the detailed correlations of the CMB at different points in the sky), by measuring the relative abundances of light elements, by measuring the decay properties of subatomic particles, and so on.

The consensus model of the Universe, called "Lambda CDM" is based on inference from dozens of different lines of evidence, all of which are mutually consistent with each other. The model makes specific and detailed predictions for what we should observe at different times in the Universe's history (different redshifts), predictions which have so far been correct.
Josso
Before the planck epoch depends on our conceptualization of before and after.
mazito
Bikerman wrote:
If you really want to boil your noggin - and possibly learn something - then try Penrose at the link below.
http://www.newton.ac.uk/webseminars/pg+ws/2005/gmr/gmrw04/1107/penrose/frames.html

It is speculative, but Penrose is never boring and, IMHO, never stupidly wrong about the science....


besides my poor english i enjoy it so much
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