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XanPaul
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What was the force holding the matter together before the Big Bang?
Gravity, electromagnetic forces, or something completely different?
Gravity, electromagnetic forces, or something completely different?
XanPaul said:What was the force holding the matter together before the Big Bang?
Gravity, electromagnetic forces, or something completely different?
Dmitry67 said:Marcus, I remember I red when I was young (in 80x :) ) that as(if) entropy is preserved during the bounce, then the entropy after the Big Bang should be ery high, and it is not cosistent with the obserations. So, what is different now?
marcus said:The main line of research that is currently dealing with conditions before and at the BB time is called Loop Quantum Cosmology.
The top 20 papers are almost all about explaining the Big Bang as a bounce, or rebound from a prior collapse. A mechanism has been conjectured that makes this happen and there has been a surge of interest in studying this.
Dmitry67 said:For example, I can critisize your "Who is going to build a perpetual machine to extract illegal work and violate the law?" by saying that in your case we can't talk about the entropy during the inflation era and soon after that, because there could not be any observers and machines, in principle (empty space or too hot)
Why is that a relevant question, Apeiron? LQC does not predict a recollapse. It describes a prior collapse, which could depending on which model, be a unique one-time event. There are some interesting questions connected with collapse in the case of positive cosmological constant and Ashtekar has a paper in preparation about this, co-authored with Tomasz Pawlowski. It has been cited in something I saw but I haven't seen the paper yet. I hope if you are interested that we can discuss it when it comes out.apeiron said:If there is an acceleration (as observation suggests) then how does gravity achieve the recollapse?
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Dmitry67 said:Yes, an yet another thing: fine tuning that our universe is almost flat. And that fine tuning had to be extremely precise!
Dmitry67 said:Or even a stranger solution where before the rebounce there was a contraction from t= - infinity?
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Dmitry67 said:... You know, there is time to post in the forum and time to read longer articles, when nobody interrupts...
Thank you for so many links...What is the best to begin with?
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marcus said:Why is that a relevant question, Apeiron? LQC does not predict a recollapse. It describes a prior collapse, which could depending on which model, be a unique one-time event. There are some interesting questions connected with collapse in the case of positive cosmological constant and Ashtekar has a paper in preparation about this, co-authored with Tomasz Pawlowski. It has been cited in something I saw but I haven't seen the paper yet. I hope if you are interested that we can discuss it when it comes out.
apeiron said:If the dark energy is positive, then it would seem there could be no crunch. ...
But perhaps you can unravel the argument being sketched here...http://arxiv.org/abs/0812.4703
• The case of a positive cosmological constant is more subtle [33]...
marcus said:Hi Apeiron,
(BTW since apeiron was the favorite idea of Anaximander of Miletus, you might be interested to know that Carlo Rovelli has competed a book about Anaximander---Rovelli has history of science as a sideline. A link to the draft copy is at http://www.cpt.univ-mrs.fr/~rovelli/ )
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marcus said:I don't need to have all the questions I can think of answered immediately. Like, were there a lot of prior bounces, or just one? That's speculative and aesthetic, not practical.
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apeiron said:. I've of course studied Anaximander intensively and he is a remarkably misunderstood and underappreciated philosopher.
...If Rovelli is into Anaximander, perhaps he too has this thought in mind?
apeiron said:Personally, I see the story as the universe dissolving to a "quantum foam" rather than arriving at a singularity. So quantum gravity approaches are a good avenue in that regard. But it seems "obvious" to me that a quantum foam is now a vague state, an apeiron indeed, and not a crisp state. Therefore if you can indeed project the correct calculations beyond the Planckscale first moment, you would have to get "something even foamier" rather than instead the foam for some reason turning crisply into a mirror universe the other side.
aristurtle said:...
BTW, does LQG bounce gives the correct CMB power spectrum?And acoustic peaks?thank you.
c12_z said:It seems to me the the "singularity" is just a concise version of "there be dragons". It is the most efficient manner of referring to that which we simply cannot, as yet, explain...
XanPaul said:What was the force holding the matter together before the Big Bang?
Gravity, electromagnetic forces, or something completely different?
Chronos said:Even logic fails prior to the big bang. Until we have observational evidence affirming or denying the propositions, such discussions are philosophy, not science. Not that I object, just wish to keep it in perspective.
Redbelly98 said:This points to my question: in any theory that addresses the universe before the Big Bang, are there any tests or observations being proposed that would either refute or confirm the theory. Or put another way, what (if any) information from that time would survive in some fashion afterwards?
Redbelly98 said:... I skimmed through the abstracts you quoted...
marcus said:I guess the general lesson is that when you test an early universe model you test the model against what we can see in the present.
This is apt to be of stuff like the CMB.
You don't test the idea of a bounce. You test a model of how the universe works, and if it has a bounce...well, then it has a bounce.
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At some level it doesn't matter very much whether it is a HoravaLifgarbagez model or a Loop Cosmology model. The important thing is to have some signature in the CMB that the Planck spacecraft can look for. Or else say how much finer resolution than Planck's you want to get.
Planck is supposed to launch May 6. Just a couple of weeks!
http://www.esa.int/SPECIALS/Operations/SEM45HZTIVE_0.html
http://www.esa.int/esaSC/120398_index_0_m.html
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This is a question that has puzzled scientists for decades. The truth is, we don't know for sure what existed before the Big Bang. Some theories suggest that there was a singularity, a point of infinite density and temperature, while others propose the existence of a multiverse. Ultimately, the answer is still a mystery.
Time as we know it is a product of the Big Bang. This means that there was no time before the Big Bang. The concept of time only came into existence after the expansion of the universe began. However, some theories suggest that time may have existed in a different form before the Big Bang.
This is a question that scientists are still trying to answer. The Big Bang theory suggests that the universe began as a singularity, a point of infinite density and temperature, and expanded rapidly. However, the cause of this initial singularity is still unknown. Some theories propose the existence of a multiverse or a collision between two branes in a higher-dimensional space.
During the Big Bang, the universe rapidly expanded and cooled, allowing for the formation of matter and energy. This process is known as cosmic inflation. As the universe continued to expand, matter and energy clumped together to form galaxies, stars, and planets. This process is still ongoing today.
As of now, we do not have the technology or understanding to fully comprehend what happened before the Big Bang. However, scientists continue to study the early stages of the universe and try to piece together the events that led to the Big Bang. With advancements in technology and new theories, we may one day have a better understanding of what occurred before the Big Bang.