Did the Big Bang happen?

[JairCrawford]

Doesn’t getting something from nothing go against the whole “matter cannot be created or destroyed; only changed from one form or the other” though?

And how can anything even “happen” “before time”?

Those concepts are tripping me up.

It is likely that the amount of matter and kinetic energy is exactly balanced by the amount of negative gravitational potential energy.  That is, they add to zero.

So in essence everything is nothing and nothing is everything. Is this at all related to the whole matter/anti-matter thing?

[HappySkeptic]

It is likely that the amount of matter and kinetic energy is exactly balanced by the amount of negative gravitational potential energy.  That is, they add to zero.

So in essence everything is nothing and nothing is everything. Is this at all related to the whole matter/anti-matter thing?

No, it is not related to antimatter.  Both an matter and antimatter have mass, and are therefore mass-energy.  If they annihilate, they create energy (not nothing).

The fact that the early universe produced more matter than antimatter is a mystery.  There must be some breaking of symmetry that caused this.  If it weren't for symmetry breaking, literally nothing interesting would exist.  Symmetry breaking is seen a number of places in physics.

[zebo-the-fat]

It all boils down to "we don't know" as far as we can tell by "running the clock backwards" the big bang seems to fit the observed universe, but the physics go a bit wonky when you get back to a tiny fraction of a second after the bang.

[Nay_Sayer]

I feel you likely don't care about the answer.

But yes it did. Caused by the pretime workings of FSM

[JairCrawford]

I feel you likely don't care about the answer.

But yes it did. Caused by the pretime workings of FSM

Why wouldn’t I care? Cosmology is absolutely fascinating to me. The universe is fascinating.

[Nay_Sayer]

I feel you likely don't care about the answer.

But yes it did. Caused by the pretime workings of FSM

Why wouldn’t I care? Cosmology is absolutely fascinating to me. The universe is fascinating.

Depends are you asking questions for the sake of learning or to reaffirm what you already believe?

[JairCrawford]

Why wouldn’t I care? Cosmology is absolutely fascinating to me. The universe is fascinating.

Depends are you asking questions for the sake of learning or to reaffirm what you already believe?

No. I abandoned YEC over a decade ago. I’m really just curious about the science. Any answers wouldn’t have any bearing on my faith on way or the other.

[polymath257]

There are a lot of issues here that overlap and need to be clarified.

1. Standard cosmology is based on General Relativity for the background spacetime geometry (expansion of space).

2. The notion of a singularity is a tricky one: a singularity is NOT an object. it is more a description of something going wrong in our model. For example, the north and south poles are 'coordinate singularities' in the coordinate system using latitude and longitude. The reason is that both the north and south poles don't really have a longitude. That is something going wrong with our mathematical description, but not with the underlying geometry. it is also possible to have singularities in the geometry itself (cusps or 'holes'). The singularity at the beginning of the Big Bang in standard cosmology is closer to a 'hole', an absence, an inability to go further back in time.

3. The term 'Big Bang' can refer to either the singularity or the fact that the universe was hot and dense in the past. Usually, cosmologists mean the latter, not the former.

So, for most cosmologists, there was a Big Bang: the universe was once very hot and dense and expanded to become what we see today. Whether or not there was a singularity, this much happened.

4. As we go back in time, the temperature and pressure of the universe get very large (hot and dense). When the temperatures and pressures are high enough, there can be no molecules, no atoms, etc. So, in a sense, things get very simple at that point. So, during the time of nucleosynthesis, the whole universe was as hot as the core of a star and the pressures were enough for fusion reactions to happen everywhere. This leads to testable predictions about what can be observed now, so there is high confidence that this stage actually existed.

5. Once we get back to a certain point, though, our understanding of high energy particle physics breaks down (this is why we built the LHC). Beyond this point (and that includes the 'inflationary scenario, where the universe expanded exponentially fast) everything is pretty much speculation.

In particular, we don't know why there is more matter than anti-matter in the universe. We have guesses, but nothing concrete has been tested and verified.

6. General Relativity inevitably predicts singularities. At one time, it was hoped that they are just a part of certain symmetrical solutions to the equations, but Hawking showed that thi sis not the case: geometric singularities are inevitable in standard cosmology.

BUT, and this is big, General Relativity does not consider the quantum mechanical aspects of gravity. While we can do quantum theory with general relativity as a background, that doesn't include the quantum aspects of gravity itself. But we also know that quantum gravity effects will become relevant at some point. So GR alone simply won't be enough. The standard model will fail to describe reality at some point.

7. There is no tested quantum theory of gravity. We have a number of proposed ways of dealing with this, but none have been tested: The energies required are simply too large for us to work with at this point.

The theories we do have for quantum gravity suggest that the singularity may be a fault of general relativity, and that it might be 'smoothed out' by quantum effects.if that is the case, time could go back prior to the 'hot dense' stage. There are several different proposals of what happened, including a multiverse which has 'universes' (hot dense pieces) bud off occasionally to a single 'previous universe that contracted to get hot and dense, leading to the current expansion, and a host of other possibilities, depending on the specifics of the theory of quantum gravity being used.

My Opinion: My bet is that bringing in quantum mechanics eliminates the singularity and allows for time to go back infinitely. Whether there is a multiverse or not is very unclear. How to test that possibility is yet to be worked out. In any case, whenever there was time, there was also space, matter, and energy.

[polymath257]

So, what I’m wondering is… Is it possible that there was no Big Bang and that the universe simply always existed?

Then you would need a real good argument as of why the cosmic background is so incredibly uniform. Places, in all directions, currently so far away that they can not possibly have interacted with each other if they were always so far apart, and yet....the temperature is the same down to a few micro-degrees.

That can be explained by a period of inflation, whether or not there is a singularity before that.

[Jehanne]

It is likely that the amount of matter and kinetic energy is exactly balanced by the amount of negative gravitational potential energy.  That is, they add to zero.

So in essence everything is nothing and nothing is everything. Is this at all related to the whole matter/anti-matter thing?

In his undergraduate textbook, Modern Physics (4th edition), Professor Kenneth S. Krane discusses cosmology in his last chapter. In it, he states that the Universe is either finite or infinite in spatial extent. Do you agree? He also states that General Relativity can handle both scenarios, a finite Universe or an infinite one. In either scenario, our Universe is expanding. Of course, if our Universe is infinite, then, it is certainly conceivable that there are events that occurred in our infinite past or will occur in our infinite future, given that the speed of light, the rate of information transfer, is finite.

Now, if our Universe is finite, it is expanding, not only into its future, but in all three spatial directions, hence, its overall volume is increasing over time. What, exactly, do you think, in this scenario, the Universe is expanding "into"?