Question about the big bang singularity

In summary, the conversation discusses the concept of the Big Bang theory and the singularity from which our universe is believed to have originated. It is clarified that a singularity is not a single point, but rather a breakdown in the mathematics. The question arises about the possibility of the universe beginning as energy in an uneven shape rather than a single point, and whether this could be detected in the current state of the universe. It is stated that the initial conditions of the Big Bang needed to be very uniform in order to explain the uniformity of the universe today. The possibility of quantum mechanics causing the tiny differentiations seen in the formation of galaxies is also discussed. However, it is noted that there is currently no need to propose another mechanism and any
  • #1
JuneSpring25
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TL;DR Summary
A question about the beginning of the universe and the original singularity
In big bang theories where our universe begins from a singularity (ignoring other theories just now), what would happen if the universe didn't begin as a single point but rather began as energy in an uneven shape? Would we be able to tell from the way the universe is now? Do we know that if the universe began in a big bang, it had to start as a single point? If so, why?

Thanks for any answers! I'm super aware of how clumsy my layman's questions are but any attempted answers appreciated.
 
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  • #2
JuneSpring25 said:
In big bang theories where our universe begins from a singularity
A singularity is a breakdown in the mathematics, not a single point.
JuneSpring25 said:
Do we know that if the universe began in a big bang, it had to start as a single point? If so, why?
It didn't. Your question is based on a misunderstanding.
 
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  • #3
JuneSpring25 said:
TL;DR Summary: A question about the beginning of the universe and the original singularity

Do we know that if the universe began in a big bang, it had to start as a single point?

You may like this Insights article, which contains some useful info about the Big Bang (scroll down about half-way through the article): https://www.physicsforums.com/insights/big-bang-infinities/#-About-the-Big-Bang
 
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  • #4
JuneSpring25 said:
TL;DR Summary: A question about the beginning of the universe and the original singularity

In big bang theories where our universe begins from a singularity (ignoring other theories just now), what would happen if the universe didn't begin as a single point but rather began as energy in an uneven shape? Would we be able to tell from the way the universe is now? Do we know that if the universe began in a big bang, it had to start as a single point? If so, why?

Thanks for any answers! I'm super aware of how clumsy my layman's questions are but any attempted answers appreciated.
PeroK said:
A singularity is a breakdown in the mathematics, not a single point.

It didn't. Your question is based on a misunderstanding.
Oh thank you. Does the energy need to be uniform at the start of the big bang? Could it be in some way unevenly distributed?
 
  • #5
JuneSpring25 said:
Could it be
Maybe it could be, but it isn't. It is very, very uniform.
 
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  • #6
JuneSpring25 said:
Oh thank you. Does the energy need to be uniform at the start of the big bang? Could it be in some way unevenly distributed?
In order to get the universe we see today the initial conditions have to have been uniform, so uniform that we had to develop new models of the early universe to explain how that could even happen. There were only tiny and very small-scale deviations from perfect uniformity, which eventually grew into the stars and galaxies we see.
 
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  • #7
Ibix said:
In order to get the universe we see today the initial conditions have to have been uniform, so uniform that we had to develop new models of the early universe to explain how that could even happen. There were only tiny and very small-scale deviations from perfect uniformity, which eventually grew into the stars and galaxies we see.
Thank you for the answers.

Do we know that the tiny differentiations we see that create galaxies etc, are caused by quantum mechanics?

Could there have been a small amount of unevenness in the original energy state that created differences in in the way the universe 'unfolded' or did the early states have to be uniform?
 
  • #8
JuneSpring25 said:
Do we know that the tiny differentiations we see that create galaxies etc, are caused by quantum mechanics?
I don't think "know" is the right word. It's more that a naive model shouldn't make such a uniform space as we see - it's very very surprising that the CMB has such an even temperature. So we develop inflation theory to explain the large-scale uniformity, and QM uncertainty naturally provides small fluctuations and GR says the fluctuations grow after inflation ends. So given that we've got a mechanism that forces uniformity and another that breaks that uniformity, why would you need to propose another mechanism? And why wouldn't it get steam-rollered by inflation anyway?

So it's not that the fluctuations must be quantum mechanical in origin. It's that there's no need to propose anything else, and you'd have to figure out how any such mechanism worked alongside inflation.

JuneSpring25 said:
Could there have been a small amount of unevenness in the original energy state that created differences in in the way the universe 'unfolded' or did the early states have to be uniform?
If you mean, can you describe a universe where that is so, sure. But if you want to talk about our universe, no, not unless there's physics going on that we haven't got a sniff of yet.
 
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  • #9
Ibix said:
In order to get the universe we see today the initial conditions have to have been uniform, so uniform that we had to develop new models of the early universe to explain how that could even happen. There were only tiny and very small-scale deviations from perfect uniformity, which eventually grew into the stars and galaxies we see.

I believe, but I could be wrong, that it had to have apparently been so uniform that such conditions only had a 1 over [insert big number here, like in the trillions] possibility of happening. Does that sound right? Could be confusing things. Thanks.
 
  • #10
Not really. It is believed that the patch of the universe which represents the universe as we see it today has been in thermal equilibrium (means homogeneous) in the very beginning. And that this patch has been blown up tremendously (search "horizon problem" and "inflation" for details) such that we see the microwave background almost homogeneous.
 
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  • #11
JuneSpring25 said:
TL;DR Summary: A question about the beginning of the universe and the original singularity

In big bang theories where our universe begins from a singularity (ignoring other theories just now), what would happen if the universe didn't begin as a single point but rather began as energy in an uneven shape? Would we be able to tell from the way the universe is now? Do we know that if the universe began in a big bang, it had to start as a single point? If so, why?

Thanks for any answers! I'm super aware of how clumsy my layman's questions are but any attempted answers appreciated.
I assume because of conservation of energy and to balance the equation at t=0 and infinity? But it depends your perspective, maybe it's okay if it's uneven like you're saying and black holes act as something like a pressure release valve that balances the overall equation at any particular moment.
 
  • #12
BIGphysician said:
I assume because of conservation of energy and to balance the equation at t=0 and infinity?
Energy is not conserved in FLRW spacetimes.
BIGphysician said:
But it depends your perspective, maybe it's okay if it's uneven like you're saying and black holes act as something like a pressure release valve that balances the overall equation at any particular moment.
Do you have a reference for this, or is it something you came up with?
 
  • #13
BIGphysician said:
I assume because of conservation of energy and to balance the equation at t=0 and infinity?
There is no "t=0" in the Big Bang Theory, which describes the evolution of the universe AFTER the period of inflation** and is silent on any creation event prior to that.

** the Inflation Period, posited by Alan Guth when he was a young physicist at Cornel, is not itself proven, but is fairly widely assumed correct (but not by all physicists) because of the problems it solves (the Flatness Problem, the Horizon Problem, and the Monopole Problem).
 
  • #14
phinds said:
There is no "t=0" in the Big Bang Theory, which describes the evolution of the universe AFTER the period of inflation** and is silent on any creation event prior to that.

** the Inflation Period, posited by Alan Guth when he was a young physicist at Cornel, is not itself proven, but is fairly widely assumed correct (but not by all physicists) because of the problems it solves (the Flatness Problem, the Horizon Problem, and the Monopole Problem).
I have always found Alan Guth's publications readable and instructive. This linked PDF may help basic understanding,

Guth, Alan (Fall 2002). "Inflation and the New Era of High-Precision Cosmology" (PDF). physics@mit. MIT Department of Physics.
 

FAQ: Question about the big bang singularity

1. What is the big bang singularity?

The big bang singularity is a theoretical point in time and space where the universe is thought to have originated from a single, infinitely dense and hot point. It is the starting point of the expansion of the universe and the beginning of time.

2. How was the big bang singularity discovered?

The big bang singularity was first theorized by Belgian priest and astronomer Georges Lemaître in the 1920s. It was later supported by the observation of the cosmic microwave background radiation in the 1960s, which is considered to be the residual heat from the big bang.

3. What evidence supports the existence of the big bang singularity?

Aside from the observation of the cosmic microwave background radiation, there are several pieces of evidence that support the existence of the big bang singularity. These include the expansion of the universe, the abundance of light elements, and the large-scale structure of the universe.

4. Is the big bang singularity the beginning of everything?

The big bang singularity is the beginning of the universe as we know it, but it does not necessarily mean the beginning of everything. The concept of time and space as we understand it may not apply to the singularity, so it is difficult to determine what came before it.

5. Could the big bang singularity happen again?

The big bang singularity is a one-time event that marked the beginning of the universe. It is not expected to happen again, as the universe is constantly expanding and cooling down. However, there are theories that suggest the possibility of cyclical universes, where a big bang singularity could occur again in the distant future.

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