Why the early universe didn't collapse into a black hole?

In summary: One more question, the ideas discussed here, like "there was relatively little gravity", are there mathematical proves behind it? It's just that I get convinced when I know there's some math behind it! :)Yes, the idea of relatively little gravity in the early universe is supported by the mathematical models and observations of cosmic microwave background (CMB) radiation. The CMB temperature fluctuations provide evidence for the uniformity and isotropy of the early universe, which in turn supports the idea of a lack of significant gravitational fields. It is also supported by the equations of general relativity, which describe the behavior of gravity in the universe.
  • #1
shazdeh
3
1
So, if our observable universe was less than a centimeter across, why didn't it collapse into a super black hole? The gravitational field of all that matter... inflation seems weird when you think that it could become into a big black hole (and it didn't; right?)
 
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  • #2
Welcome to PF shazdeh. Your question is addressed in the Cosmology Forum FAQ:

https://www.physicsforums.com/showthread.php?t=506992" [Broken]
 
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  • #3
It did not collapse because the spatial condensation expansion rate was so great in the production of the supporting 4-D ball.
 
  • #4
It did not collapse into a black hole for reasons clearly outlined in the above referenced FAQ.
 
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  • #5
Thank you for the answer!
I read it again, and again, and again, and I didn't get it! :)

there is no location that would be the place where we would expect a black hole's singularity to form.
I'm missing some points in here; there was space in singularity, wasn't it? Quoting SciAm June 2008, page 53, "at the time of inflation, our observable universe was less than a centimeter across." That's space, no?
 
  • #6
Gravity was ineffective for a brief time after the BB.
 
  • #7
shazdeh said:
I'm missing some points in here; there was space in singularity, wasn't it? Quoting SciAm June 2008, page 53, "at the time of inflation, our observable universe was less than a centimeter across." That's space, no?
Yes, that's the size of the observable universe -- the patch of spacetime within which all events are causally related. However, the actual universe is a patchwork of these causal regions. The big bang was not a localized event -- it happened everywhere at once. Keep in mind, that the big bang model does not address the initial singularity -- it is believed that the singularity is signalling a breakdown of the mathematical theory at this time, rather than representing something physical. So the big bang is the cosmological model that describes how the early universe expanded from a hot, dense phase into a cooler, less dense phase. This expansion, by all accounts, has been uniform and isotropic because the energy density is uniform and isotropic. An energy density of this form does not give rise to a gravitational field, and therefore does not yield black hole solutions.
 
  • #8
Shazdeh: Welcome to Physicsforums...

try reading the FAQ several more times..slowly..maybe over a few days...understanding the terminology and the concepts is not easy...especially when you are getting started...for example "tidal forces" is NOT an obvious concept..Wikipedia for one explains it...

from the FAQ:
"...In a homogeneous cosmology, symmetry guarantees that tidal forces vanish everywhere, and that any observer at rest relative to the average motion of matter will measure zero gravitational field..."

So despite what might be commonly thought, there was relatively little gravity...a rough analogy might be falling through to the center of the earth...the further you fall from the surface the more gravity pulls you out as well as in...at the exact center you are pulled equally in all directions...

Another analogy: in outer space, you virtually "float" because you are pulled weakly but about equally in all directions by gravity...


So the big bang is the cosmological model that describes how the early universe expanded from a hot, dense phase into a cooler, less dense phase.

yes...there was enough energy to cause incredibly rapid expansion...but no one knows just what caused the big bang itself...what was the nature of the initial instability...
 
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  • #9
Naty1 said:
yes...there was enough energy to cause incredibly rapid expansion...but no one knows just what caused the big bang itself...what was the nature of the initial instability...
Indeed, but I think it's important not to put too much focus on the amount of energy, or the rapidity of the expansion, or the strength of gravity. It's really a matter of symmetry -- a uniform spacetime of critical density will expand (or contract) -- it will not form a black hole.
 
  • #10
Thanks for your help! Those analogies were awesome!
To wrap my head around it, here's a question: if we could by any mean open a well deep to the heart of the earth, and if I'd jump into it, would I reach the center of the earth? Because, "the further you fall from the surface the more gravity pulls you out as well as in", does this mean in a point along my trip the gravity pull from above and below would become equal and I'd stop? Sorry if it sounds a silly question, but I'm new to these! :)

One more question, the ideas discussed here, like "there was relatively little gravity", are there mathematical proves behind it? It's just that I get convinced when I know there's some math behind it! :)
 
  • #11
shazdeh said:
if we could by any mean open a well deep to the heart of the earth, and if I'd jump into it, would I reach the center of the earth? Because, "the further you fall from the surface the more gravity pulls you out as well as in", does this mean in a point along my trip the gravity pull from above and below would become equal and I'd stop?
There will always be more mass "below" you than "above" you as fall towards the center of the earth. As Naty1 says, only at the very center will the net gravitational force be zero.
 
  • #12
bapowell said:
There will always be more mass "below" you than "above" you as fall towards the center of the earth. As Naty1 says, only at the very center will the net gravitational force be zero.
If the hole is completely straight through the Earth, inertia would tend to carry a body on past the center where the gravitational force is zero.and into an oscillation mode through the center. But the rotation of the Earth would keep the body scraping the side of the hole which would eventually bring the remains to rest at the bottom.
 
  • #13
Assuming, of course, that you did not enter a tunnel along the axis of rotation.
 
  • #14
Not against either outward jet of mass in opposite directions when those tunnels open!
 
  • #15
Your reply "Unless the hole is on the axis of rotation of the Earth", is right on the mark.
 
  • #16
CBLeffert said:
... the rotation of the Earth would keep the body scraping the side of the hole which would eventually bring the remains to rest at the bottom.

(my bold) :biggrin:
 
  • #17
Because maybe the big bang came from a ginormous black hole, a singularity that became so unstable that it burped out the entire universe :)
 
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  • #18
From what I've heard,my understanding of the early universe (big bang) is that matter and anti-matter was popping into existence then instantly anihilating producing energy.But once in a bllion times they didn't anihalate and a particle of matter was left over.thus there is enough energy to force the matter to expand away from the singularity,creating space and time.question was all the matter produced in an instant or did an expanding shock wave tear matter and anti-matter apart as it expanded?
Is my understanding wrong?
 
  • #19
derek101 said:
But once in a bllion times they didn't anihalate and a particle of matter was left over.

Something like this?

2M + 2A --> E + M

M = Matter
A = Anti-matter
E = Energy
 

1. Why didn't the early universe collapse into a black hole immediately?

The early universe was extremely hot and dense, with matter and energy distributed almost evenly throughout. This dense distribution of matter and energy prevented the formation of a black hole, as the intense gravitational pull would have been counteracted by the strong repulsive forces between particles. Additionally, the universe was expanding rapidly, causing the matter and energy to spread out even further and preventing collapse into a single point.

2. How did matter and energy become more spread out in the early universe?

The rapid expansion of the universe, known as inflation, caused the universe to grow exponentially within a fraction of a second after the Big Bang. This expansion caused the matter and energy to become more evenly distributed, preventing the formation of a black hole.

3. What role did dark matter and dark energy play in preventing the collapse of the early universe?

Dark matter and dark energy are both hypothetical substances that are thought to make up a large portion of the universe. Dark matter is believed to have a gravitational effect on visible matter, helping to keep it spread out and preventing collapse into a black hole. Dark energy is thought to be responsible for the accelerating expansion of the universe, which also plays a role in preventing collapse.

4. Could the early universe have collapsed into a black hole if conditions were different?

It is possible that under different conditions, the early universe could have collapsed into a black hole. For example, if the universe had not undergone rapid inflation or if the amount of dark matter and energy were different, the collapse may have occurred. However, the exact conditions that prevented collapse are still not fully understood.

5. Is it possible for the current universe to collapse into a black hole?

It is highly unlikely that the current universe will collapse into a black hole. The expansion of the universe continues to accelerate, and the distribution of matter and energy remains relatively even. Additionally, the current understanding of the laws of physics does not suggest that such a collapse is possible. However, the fate of the universe is still a topic of ongoing research and debate among scientists.

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