The Big Bang: Explaining the Unfathomable

[Zantra]

Ok apparently I just don't get it, so perhaps someone can explain this to me.

Why do we assume that nothing existed before the big bang? Why do we assume that time began with the big bang? DO we have evidence or logic to support this theory? Forgive me if these things are elemetary, but if someone could explain them to me, I would appreciate it.

 

[LURCH]

If the BB model is correct, then the universe began with the BB. Time is a function of this universe, so if the universe began with the BB, then Time began with the BB. So there are two reasons why things could not have existed before the BB:

1) The BB was the beginning of all "things", so things could not exist until it occured

2) The BB was the beginning of time, so "before" can't even exist before it.

If either of these statements is incorrect, then so is the BB Model.

 

[Zantra]

Ok then my initial assumption that existence of a prior sate to the BB is a possibility is correct, provided one or both of your points are incorrect. So it IS possible. See the PHYSICS forum for the ongoing debate on this issue.

thanks lurch

 

[megashawn]

One thing that bugs me, is that if the big bang created "all things" then would not all things had to of existed in some compressed form in order for them to bang, so to speak?

Would this not point to a larger reality then we encorporate? Like a big bang breeding ground or something?

 

[Chen]

Originally posted by megashawn
One thing that bugs me, is that if the big bang created "all things" then would not all things had to of existed in some compressed form in order for them to bang, so to speak?

Would this not point to a larger reality then we encorporate? Like
a big bang breeding ground or something?

As far as I understand it, at the very beginning the whole universe was consolidated into one point, from which it "banged" and since then expands. What really puzzles cosmologists is what happened at this very beginning, Planck time.
http://www.physlink.com/Education/AskExperts/ae281.cfm

 

[Bunting]

dont people say ...

"if you travel faster than light, then you can get back to where you are before you even set out".

if the big band was a kickass ***** ass SOB ball of energy, then couldn't it have enough energy to go back and start before there was no time (or something), and thus allowing something to start, then time starts, and after that its all rice cakes and explsions :)

just a thought :)

 

[Cyberice]

If the BB model is correct, then the universe began with the BB. Time is a function of this universe, so if the universe began with the BB, then Time began with the BB. So there are two reasons why things could not have existed before the BB:

Um, if nothing was there before the BB then what was there to "bang"? A valid argument I think. I don't think anyone can prove how it 'started'.

 

[Tail]

Perhaps nothing was happening before the Big Bang? After all, time is how fast things happen...

 

[kishtik]

A scientific approach,
We don't know anything before a (very very little) fraction of second after big bang.

 

[tee]

If we all agree that time began with the big bang, then I like to point out that it is incorrect to ask "what happened before the big bang?"

This question has no meaning at all as time only came into existence after the big bang, therefore we cannot use the word, 'before'.

 

[Phobos]

The universe is expanding. So, in the past, it was less expanded (points were closer together). Keep going back in time and the whole universe was a point. What was this point like? Where did it come from? Why did it 'Bang'? That remains a big unknown and a big area of ongoing research. Sufficed to say, we have no way to test anything 'outside of' or 'before' this universe...or, I should say, the visible universe (that which we have the capacity to see, based on the finite speed of light and the age of the universe).

Was there something 'before'? Is there something 'outside'? Possibly. But we have no evidence for it. If there was, we may need to redefine our concept of the universe.

 

[russ_watters]

No one has addressed Zantra's questions.

Why do we assume that nothing existed before the big bang?

We don't. Since the universe began with the big bang, we can't even THEORIZE, much less assume anything at all about "before" the big bang. In fact, since time started at the big bang, "before" doesn't really have any meaning anyway.

Why do we assume that time began with the big bang?

It had to. Time as we know it cannot exist inside a black hole. This is a consequence of relativity.

DO we have evidence or logic to support this theory?

The big bang itself? Irrefutable evidence. The Hubble Constant and the cosmological background radiation can mean nothing else that the laws of physics would accept. The best alternative (seriously) is that God created the universe 4000 years ago and made it LOOK like it was 15 billion years old. There is no scientific theory to compete with the big bang.

I covered it with the first question, but I must reiterate: The most often misunderstood thing about the big bang is its scope. The big bang theory actually starts an instant AFTER the big bang. So discussion of what happened BEFORE the big bang including the whole "something from nothing" idea is irrelevant to a discussion of the big bang itself. This is very similar to the usual misunderstanding of evolution - that evolution predicts life started from nothing. It does not.

 

[Max]

Time and space are connected and the 2nd Law of Thermodynamics implies that the Universe was "wound up" as it were or had at some point a beginning. Since everything is in constant entropy.

Therefore before the BB, there was nothing. No space...and no time.

 

[The Hinge]

I myself find it difficult to concieve of timelessness.
Time after all is change, and change is movement of particles, moving particles can be described as heat. Then maybe after all Time=Heat.

Then I think to myself, if the universe is flat and we are headed to a big freeze...a big freeze is basically the end to time. And when there is no time...basically we are at the beginning again, a still and inconcievable universe.

[?] I think I could make an argument about dark matter some how.
Something about frozen universes. hmmm.

 

[marcus]

Originally posted by Zantra

Why do we assume that nothing existed before the big bang? Why do we assume that time began with the big bang? DO we have evidence or logic to support this theory?

There are fashions in science and the fashions change. The bigbang BEGINNING notion is largely an artificial consequence of the breakdown of the equations that served as model.
For 80 years or so cosmologists have used the Friedmann equations (simplified versions of the 1915 Einstein GR equation) and when these equations are fitted to present data and extended backwards in time they break down at time zero and fail to compute.

However this bad behavior of the Friedmann equations has been fixed by a growing number of people all more or less in the same way (Martin Bojowald was the first, in 2001, but since then a lot have done it). The model is fixed by a standard quantization proceedure so you now have the "quantum Friedmann equation"
which doesn't break down at time zero.

So a person has no good reason to believe that time or anything else began at time zero. (unless the idea of time beginning thrills them or something). the idea of a Beginning is a "made up" idea. I am skeptical of unnecessary imagination. Why not say we don't yet know very much about the very early universe but some models don't break down so let's not start pretending we know weird stuff like "nothing existed before time zero" which we don't really know. I favor waiting patiently (suspending judgement) and as the model is improved and studied more we will gradually learn more about early events.

Why do we assume that nothing existed before the big bang?

We should not assume that. It is an unscientific assumption for which there is no evidence. Indeed some models calcuate stuff for before.

Originally posted by Zantra

Why do we assume that time began with the big bang?

That is another case of sheer speculation. Sure it could be true or it could be false. We don't know. There is research in progress about this. There is no reason to suppose that time began then so it is scientifically unwarranted to assume it.

Also it gets you embroiled in unnecessary philosophical contemplations about what does it mean for time to begin at some moment.

Originally posted by Zantra

DO we have evidence or logic to support this theory?

The bigbang beginning is a superstition caused by uncritical acceptance of 1915 GR as the final word.
If it weren't possible to quantize GR and fix the time zero glitch.
If we stuck for all eternity with a set of 1915 equations that broke down and stopped working at a very high density state called time zero, then there would be some reasoning or logic to support the idea that the universe began then

In June of this year there was a conference at U. Marseille called
"Where Cosmology and Fundamental Physics Meet" and this was one of the invited papers at that conference.

http://arxiv.org/astro-ph/0309478

It has a lot of references to other papers about the same stuff, also online. The paper is 6 pages and not all that hard to read so if you want a taste of this particular line of research you could try it. Or ask here at PF if you want to know more about it, several people have been following this.

 

[Mentat]

I think a point that has not really been made directly is this: The term "Universe" means "everything". If there was a beginning to the Universe, then there was nothing before it. However, it is just as possible that the Universe still existed, just not in it's current form, before the Big Bang (such as M-Theory and, I think, certain takes on LQG postulate).

If, however, nothing existed before the Big Bang, then there are explanations (mostly just quantum weirdness) as to how "something" came from "nothing".

 

[marcus]

Originally posted by Mentat
...and, I think, certain takes on LQG postulate).

Mentat I believe you think right about that. In fact it can
be put more forcefully.

LQG is an approach to quantizing classical GR keeping as much of the old structure and introducing as little newly made-up stuff as possble. Applied to cosmology (where the model is the Friedmann equations) it has the right limits and provides a usable quantization of the Friedmann equations which now a handful of people have explored.

In every study of loop quantized cosmology that I have seen, by whoever the investigators, the big bang turns out NOT to be the beginning.

In every LQC paper I've read, the singularity in the old GR theory is removed. So I would not say "certain" loop quantum cosmology viewpoints, but actually every treatment I've seen

If anybody has seen a paper which actually shows the universe "beginning" at bigbang time-----I mean a LQC paper----I would love to see it as it would be very curious and unexpected.

If anyone has a loop-quantized GR paper where there is "nothing" before the current expansion phase, please post the link!

What the LQC papers all get is one form or another of a kind of bounce----there is a contracting phase which reaches a kind of quantum limit of density and can't contract anymore and the equations modeling it have it start expanding

if you are curious have a look at equation (4) of
astro-ph/0309048
which is the "basic evolution equation" or quantized Friedmann model.
it is a difference equation because things get discrete around Planck scale and near time zero, but behaves as expected at later times, far enough removed from the classical singularity.

It looks to me as if relativists (people whose specialty is General Relativity) are moving over to using quantized GR for cosmology
in part because quantizing removes the classical singularity and as increasing numbers do research in LQC. Intereresting development to watch!

 

[Mentat]

Originally posted by marcus
Mentat I believe you think right about that. In fact it can
be put more forcefully.

LQG is an approach to quantizing classical GR keeping as much of the old structure and introducing as little newly made-up stuff as possble. Applied to cosmology (where the model is the Friedmann equations) it has the right limits and provides a usable quantization of the Friedmann equations which now a handful of people have explored.

In every study of loop quantized cosmology that I have seen, by whoever the investigators, the big bang turns out NOT to be the beginning.

In every LQC paper I've read, the singularity in the old GR theory is removed. So I would not say "certain" loop quantum cosmology viewpoints, but actually every treatment I've seen

If anybody has seen a paper which actually shows the universe "beginning" at bigbang time-----I mean a LQC paper----I would love to see it as it would be very curious and unexpected.

If anyone has a loop-quantized GR paper where there is "nothing" before the current expansion phase, please post the link!

What the LQC papers all get is one form or another of a kind of bounce----there is a contracting phase which reaches a kind of quantum limit of density and can't contract anymore and the equations modeling it have it start expanding

if you are curious have a look at equation (4) of
astro-ph/0309048
which is the "basic evolution equation" or quantized Friedmann model.
it is a difference equation because things get discrete around Planck scale and near time zero, but behaves as expected at later times, far enough removed from the classical singularity.

It looks to me as if relativists (people whose specialty is General Relativity) are moving over to using quantized GR for cosmology
in part because quantizing removes the classical singularity and as increasing numbers do research in LQC. Intereresting development to watch!

No doubt!

BTW, I only pur it forth meekly because I haven't read enough on LQG to speak as an authority, but all of what I have read indicates that the BB was not the beginning.