Is the Big Bang Theory a Foolhardy Extrapolation?

[OOO]

However, if particle inertial masses suddenly increased then that would speed up the rate of atomic clocks, so reversing the process might well map the instant of the BB back to t = - \infty!

As far as I can tell from your words, this is exactly the kind of phenomena I was thinking of. (Oops, I've broken my vow of silence again this is quickly getting out of control)

 

[Chris Hillman]

A Good Book

OOO, if I interpret you right, you are saying something like you find it strange to say that the universe is 13,7 billion years old when we don't know what laws of physics to use above 100 GeV?
In that case I am willing to agree with you.

I think it is crucially important to stress that what cosmologists really believe is not quite "the universe began 13.7 billion years ago" but rather "we can begin to describe the evolution of the universe beginning 13.7 billion years ago, when it was much hotter and denser and...".

To repeat, I'm finding it odd that the universe should have begun at a singular instant in time with a huge amount of energy coming from nothing.
...
My own (diffusely expressed) conjecture that the universe could probably be somehow eternal so that what we extrapolate as 13 billion years is actually negative temporal infinity, was just a dumb example of an explanation that calls for less trouble, in my opinion.

I have no theory fragment that expresses this view, so I have nothing to share in this respect. However it seems natural to me, that combining a theory like general relativity (in which you could well choose a coordinate system where t=-13000000000yr is mapped to t=-infinity) with the standard model (where there are natural timescales because there are fixed masses and couplings) could easily lead to such conclusions as the apparent Big Bang.

Hawking and Ellis, The Large Scale Structure of Spacetime, Cambridge University Press, 1973.

IMO as a past or future physicist with an interest in cosmology, you really ought to read it. This would clear up some rather serious misconceptions which IMO are evident several of your comments above.

OK, I'll bow out here since I find I am repeating myself

OOO, I have put you in my ignore list and suggest that you put me in

Yours

 

[OOO]

Hawking and Ellis, The Large Scale Structure of Spacetime, Cambridge University Press, 1973.

IMO as a past or future physicist with an interest in cosmology, you really ought to read it. This would clear up some rather serious misconceptions.

OK, I'll bow out here since I find I am repeating myself

Perhaps we have just no common mode of communication. You think you have to teach me the basics of differential geometry and I am asking myself what you are insisting on that isn't apparent from your speech.

 

[OOO]

Ok, I think I'm getting closer to get what you mean.
You are saying something like the universe at some point, say X billion years ago, was in a state (however it got there) which, using the physical laws as we know them, looked exactly like it was originating from a big bang, right? (This corresponds to your balloon before it bursts.)
First of all, this could actually be more of a philosophical question. How do you know the universe didn't come into existence just a second ago, with all memories planted in your brain, and everything looking just like it was created 13,7 billion years ago just because it was finely tune to look like that? These kind of claims are of course not scientifically testable.

This is what I wanted to say all the time since my first post. Take a bucket of white wall paint, put in some red paint, stir heavily, and what you finally get is a bucket full of light pink wall paint. No information about how it began. You could well have gone into the store and have bought that bucket of light pink paint from the shelf.

But if you have a theory that describes very accurately what you observe (in our case: you see the dirty wall and remember that you wanted to give it a new paint), you might be able to conclude that most probably you mixed the paint yourself, although you can't deduce this from the present state of the paint alone.

Remember also that the Big Bang theory predicts a number of observations which are set up from physical processes before "your balloon bursted". In the Big Bang model the CMB originates from (13700000000 - 300000) years ago, while the hydrogen/helium abundances were synthesised (13700000000 - 0.000003) years ago. The alternative model of course also needs to reproduce the prediction of a CMB and the same relative abundances of light elements.

I can't see why this should rule out every other possibility. Once again think of particle masses being variable under extreme conditions. Who can say that the above figures wouldn't get a different meaning when judged with a different theory. Of course, pervect is right as he remarked about the question, whether there is evidence for that at all.

Thus I remind you once again, that I have no theory. I just say that terrestrial physics could lead to new theories that, if interpreted consequently, unequivocally lead to a different interpretation of what we now conceive as the Big Bang. I guess this is a rather weak statement, so I don't understand why saying this upsets some people that much.

I just hate NoGo theorems and NoGo-like thinking. NoGo's are rather stupid robots. Send them to tidy the room and they kill your mother.

 

[EL]

I think it is crucially important to stress that what cosmologists really believe is not quite "the universe began 13.7 billion years ago" but rather "we can begin to describe the evolution of the universe beginning 13.7 billion years ago, when it was much hotter and denser and...".

Exactly, that is my point.
I advocate to define t=0 (i.e. "when the big bang took place") right at the end of inflation. After all, the reheating at the end of the inflationary period "created" all the particles, just like the common notion of "the big bang creating everything". In this way we can say "inflation ended 13,7 billion years ago" instead of refereing to the age of the universe. Alternatively we can define our universe just as the one which came into existence after inflation.

 

[EL]

I can't see why this should rule out every other possibility.

Well, it doesn't.

Who can say that the above figures wouldn't get a different meaning when judged with a different theory.

Sure, but the different theory still needs to reproduce what we observe today (the CMB and the hydrogen/helium abundancies). Of course the origin of the CMB and light element abundancies need not be the same.

Thus I remind you once again, that I have no theory.

I know, that's why I wrote "your" theory within quotation marks.

I just say that terrestrial physics could lead to new theories that, if interpreted consequently, unequivocally lead to a different interpretation of what we now conceive as the Big Bang.

Well, sure it "could" happen, who knows? On the other hand I think we have a rather good understanding of the physical laws up to say 100 GeV. But it seems you do not agree with this, or?

 

[OOO]

On the other hand I think we have a rather good understanding of the physical laws up to say 100 GeV. But it seems you do not agree with this, or?

If you refer to the Big Bang: since you already know that I'm no cosmologist, you can't expect that I agree with something, I have almost no knowledge about. But it's safe to say, that I trust these many people who have combined the presently known physics in a reasonable way to get a reasonable theory of the Big Bang.

If you refer to the Standard Model: yes, it's experimentally quite well-tested. But the essential information has to be put in by hand, which seems to be unsatisfactory in the light of the alleged "rather good understanding". Moreover the attempt to get predictions in the non-perturbative regime leads to very hard calculations, either analytically or on the lattice. Thus the formation of bound states of quarks isn't nearly as well-understood as many people would hope.

 

[EL]

If you refer to the Standard Model: yes, it's experimentally quite well-tested. But the essential information has to be put in by hand, which seems to be unsatisfactory. Moreover the attempt to get predictions in the non-perturbative regime leads to very hard calculations, either analytically or on the lattice. The explanation of bound states of quarks isn't as well-understood as many people would hope.

I am mainly referring to GR, thermodynamics, statistical physics, atomic physics, nuclear physics and the Standard Model!
We don't have to "explain" all experimental results in order to use them empirically.

 

[OOO]

I am mainly referring to GR, thermodynamics, statistical physics, atomic physics, nuclear physics and the Standard Model!
We don't have to "explain" all experimental results in order to use them empirically.

In this respect I admit that I am a bit theoretically biased.