What does the theory of the big bang say about this

In summary, this conversation discusses the theory of the Big Bang and its various models. The main focus is on the concept of a "bounce" or a prior collapse stage that achieves a high density, followed by re-expansion. There is a debate about the size of the universe at the time of the bounce, with some estimates saying the size of an atom and others saying the size of a grapefruit. The density at the bounce is extremely high, and it is unknown what the universe looked like at that point. The models also raise questions about the fabric of space and the concept of time, with some models saying that gravity becomes repellent at that density and others using a clock variable to track time. There is a lack of accurate popular
  • #1
Mozart
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I don't understand the theory as much as I would like to. Please pardon my non technical vocabulary and lack of thorough insight on the topic at hand.

So...geez how do I put this into words...So everything imaginable in this universe was compressed, (superimposed?), into what is popularly said to be the size of an atom? Does that mean that all the energy, mass, etc was all compacted into this dense region?

My main question here is does this include the fabric of space?? Or does the theory say that the material/energy expanded into pre-existing space that was already around the baby universe? Or was there a non existence of anything including physical dimensions beyond this compressed universe?

Also, I read a few times where the author writes "..and after the universe was 30 seconds old" That bothers me how can you possibly have some stable experience of time when the physical universe is changing so drastically?

AGAIN I am not a physicist so pardon my ignorance on the topic.
 
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  • #2
Mozart said:
...So everything imaginable in this universe was compressed, (superimposed?), into what is popularly said to be the size of an atom?

I'm skeptical of the size estimate. Quite a lot of recent work models the big bang as a bounce----a prior collapse stage that achieves a high density, followed by re-expansion.
I've seen estimates like the size of a grapefruit, but not an atom. But we don't know the size of the universe now! So we can't seriously estimate the size at the time of bounce.

The models only give you a handle on the density at the moment the bounce occurs. Very roughly 1090 water.
How big it would be would depend on how much universe there is to compress down to that density, would it not?

There are a bunch of competing models. A book is scheduled to come out on all these approaches, written by the various proponents, in spring 2009. And the models need to be tested. It's a wait-and-see thing at the moment.



Does that mean that all the energy, mass, etc was all compacted into this dense region?

YES, if the universe is finite then it would be a dense finite region.

My main question here is does this include the fabric of space??

YES CERTAINLY, at least in the bounce models there is no surrounding space---so whatever the fabric of space means, it was definitely in there with the matter. I doubt that matter would be distinguishable from geometry at that density. Let's not talk about space (geometry) and matter as if they were separate things, let's just say "existence". We really don't know what it looks like at that high a degree of compression. the quantum gravity models say that gravity actually becomes repellent at that density, instead of attractive.


Also, I read a few times where the author writes "..and after the universe was 30 seconds old" That bothers me how can you possibly have some stable experience of time when the physical universe is changing so drastically?

I think that is a good question and you are right to be skeptical. Maybe after 30 seconds conditions could have been such that one might imagine some kind of clock, or an observer with a standardized sense of time. But if you push back closer to the bounce, or to whatever the start of expansion was, it becomes hard to define time.

In the bounce quantum gravity models they often pick one of the physical variables to keep track of time. If you are watching, say, three variables then you sacrifice one of them and make it the clock---and study how the other two change in relation to the one that is the clock. I know :smile: it sounds unsatisfactory.

But there is a serious question of what time means and how you can run a dynamical model---when you get into these extreme situations.

there are also discrete models that operate stepwise. you can't say what tiny fraction of a second each step takes---time as a continuum has been lost and all that remains is sequence---stages first of contraction and then of expansion happening in order.
 
  • #3
what I get from your post above all is incredulity, Mozart. You suggest that the story---especially what comes up in bad popularized accounts, is mindbogglers.

I think that is basically right. The popularized story is pretty hard to swallow. And it is misleading. there has been a lot of change in the field since 2001, even since 2005. I don't know of any accurate up to date popularization. If you are going to be boggled, it is better to be boggled by the concepts that real scientists are currently using and investigating.

the key field is quantum cosmology. A leading expert in QC is named Ashtekar. He often is the invited speaker on quantum cosmology at international conferences. He and his co-workers (postdocs, grad students, co-authors) are influential in current research on events around the big bang. He doesn't do popularizations, but some of his stuff is written for a wider audience than just specialists. You could sample it, read the summary at the beginning. I don't know what else to suggest.

Here is the most introductory thing Ashtekar has written recently
http://arxiv.org/abs/gr-qc/0702030
An Introduction to Loop Quantum Gravity Through Cosmology
it is free for download, just click on PDF.

Here are a bunch of quantum cosmology links---resulting from a keyword search
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=DK+quantum+cosmology+and+date+%3E+2005&FORMAT=WWW&SEQUENCE=citecount%28d%29

Even though it is technical, professional journal style, it is always possible to scan introductory paragraphs, conclusion paragraphs, and see if you can get anything out.
I don't know anything to recommend that is really ideal.

Maybe after Rudy Vaas book "Beyond the Big Bang" comes out next spring someone will do a popularization for general audience on this.

Here is the Amazon page on Vaas book , but it is still way too technical, and costs too much
https://www.amazon.com/dp/3540714227/?tag=pfamazon01-20
 
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1. What is the theory of the big bang?

The theory of the big bang is a scientific explanation for the origin and development of the universe. It suggests that the universe began as a single, extremely dense and hot point called a singularity, and has been expanding and cooling ever since.

2. How does the theory of the big bang explain the formation of the universe?

The theory of the big bang explains that the universe began with a rapid expansion known as inflation, which caused matter and energy to spread out and form galaxies and stars. As the universe continued to expand, it cooled and formed the elements necessary for the existence of planets and life.

3. What evidence supports the theory of the big bang?

There are several pieces of evidence that support the theory of the big bang, including the cosmic microwave background radiation, the abundance of light elements, and the observed expansion of the universe. Additionally, the theory is consistent with other scientific principles and observations.

4. Does the theory of the big bang conflict with any religious beliefs?

The theory of the big bang is a scientific explanation for the origin and development of the universe, and it does not necessarily conflict with religious beliefs. Many religious teachings and beliefs can be interpreted to align with the scientific understanding of the big bang.

5. Are there any alternative theories to the big bang?

There are several alternative theories to the big bang, such as the steady-state theory and the cyclic model. However, the big bang theory remains the most widely accepted and supported explanation for the origin of the universe among the scientific community.

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