5 ms·

Why didn’t the Universe become a black hole?

58 points by lelf 12y ago

trhway 12y ago
simpler question - the Universe's end game - given currently observed dynamics does it lead to one gigantic black hole inside very thinly expanded very cold vacuum (with CMB temperature practically 0 instead of 2.7 degrees K today) or to many of such black holes and what would be their distribution?
- MAGZine 12y ago
  The universe's end game is to expand forever until it's eventual heat-death. As far as science is aware, anyhow.
- millstone 12y ago
  Black holes eventually evaporate due to Hawking radiation. The current thinking for the very-long-term fate of the universe is the "Dark Era:" nothing except photons, neutrinos, and the occasional electron or positron.
aikah 12y ago
So basically,is he saying that the universe we are in is an "unlikely outcome" of a phenomenon? So basically the universe was created "by chance"?
- darkmighty 12y ago
  I think it's not a probabilistic matter, but more a way of framing Occam's razor. If you allow enough "tunable" variables with just the right values you can easily make a theory fit any observation. For this reason theories including variables requiring a lot of precision to generate our universe are looked with distrust by physicists, I believe.
ars 12y ago
Summary: Because the energy of the Big Bang was moving, and the Schwarzschild radius is for stationary mass. And I'm sorry, but this explains NOTHING. Even for moving mass the density was enough to make a black hole. So presumably the density never actually got that high, or there is some other explanation we are not aware of. He should have just said: We don't really know. Because we don't. Why is there this requirement that science be able to explain everything? Is it because it's held up as an alternative to religion so people are petrified that if there are any holes people will say "sciences knows nothing, back to religion"? (Now that I've setup my strawman I'm going to knock it down.) First of all Science and Religion are not competing for adherents. You can believe that God created the universe and still want to investigate how he did it, and what the details are. Even if you believe the Big Bang never actually happened (i.e. it's an off-camera backstory), you can still be interested in investigating it because if God made it look like that then it's important. Second the whole point of science is saying "I don't know", otherwise it's a religion, not science.
- trhway 12y ago
  >So presumably the density never actually got that high, or there is some other explanation we are not aware of. density don't need to be high to get a black hole - the more the mass the less its minimal density has to be when black hole can be formed - the Schwarzschild radius of our Universe (which is mostly space with the specks of matter) is on the scale of 10B+ light years for example. So depending on how it is calculated and a lot of other stuff - we still can be inside expanding black hole :)
  - AnimalMuppet 12y ago
    Disclaimer: I'm speculating further than my knowledge of physics. But if you add dark matter, could that push the Schwarzchild radius of the universe to 13B light years? That is, to the (observable) radius of the universe? If so, then is it possible that the red shift of distant objects is a black hole effect (remember that in this scenario, we're inside the event horizon), rather than due to the expansion of the universe? Would this also explain dark energy? It would require that red-shifts in a black hole be non-linear in distance, which I think is plausible, and that they be non-linear in the right direction, which I don't know enough to say anything whatsoever about.
neduma 12y ago
Related video: https://www.youtube.com/watch?v=2XkV6IpV2Y0&list=PLFs4vir_WsTwwb2zqmtE2WTEFdc7AQHnc https://www.youtube.com/watch?v=2XkV6IpV2Y0&list=PLFs4vir_Ws...
eridius 12y ago
Superficially interesting article, but it didn't actually answer the question very well. As near as I can tell from this article, the answer is basically "because it was expanding". It then went into a discussion about the possible behaviors of the universe over time, i.e. expanding indefinitely, having its expansion rate become static, or collapsing. But this discussion is tangential to the question. I also don't like how the discussion at the end was phrased. It started talking about fine tuning and making a mathematical argument as to the chances that our universe would have exactly the amount of mass it does (which I believe makes the assumption that the mass in our universe is random, though it was never stated). The problem with this is it's basically the argument that our universe must have been made by some external entity (i.e. "God"), without actually saying as much. I say this because there's no other good reason to try and make claims about the statistical likelihood of our universe having the initial conditions it did. And of course, it completely failed to mention that of course the universe's conditions are just right for it to have produced stars and planets and eventually life, because otherwise we couldn't be talking about it. There's a pithy name for this, but I forget what it's called. It also failed to mention the trivial solution to getting a universe that's fine-tuned just right, assuming random initial conditions, that doesn't require invoking any kind of supernatural being: infinite universes.
ssivark 12y ago
IMHO, that was a very long-winded non-explanation. Basically the "answer" comes down to this: 1. We really don't know. We don't understand the rules of physics well enough to model the behaviour of stuff in such "extreme" situations. 2. If you still insist on asking that question, I could give you a plausible explanation of why the question is not really the right thing to ask: "small" black holes tend to evaporate very quickly through the process of Hawking radiation -- in effect producing photons, matter, and every possible kind of "stuff". So even if there was something akin to a black hole, early in the universe, (and if we could apply our rudimentary understanding of gravity and quantum mechanics to even talk about black holes and Hawking radiation) it wouldn't trap the stuff for long... in fact it would be spewing out stuff in copious amounts, and very quickly at that.
idlewords 12y ago
"one part in 10^24, which is kind of like taking two human beings, counting the number of electrons in them, and finding that they’re identical to within one electron" I hate to be pedantic... wait, I LOVE to be pedantic. If you consider a human being to be a 50kg bag of water, that's 2750 moles of water, or ~1.7 * 10^27 molecules. Each molecule has ten electrons, so this factoid is off by about four orders of magnitude. More if the person had a big bowl of electrons for breakfast that day.
- sarreph 12y ago
  I'm not sure a 'bowl of electrons' would be that great an example either ;) (density, etc)... Just being pedantic!
higherpurpose 12y ago
> What’s remarkable is that the amount of fine-tuning that needed to occur so that the Universe’s expansion rate and matter-and-energy density matched so well so that we didn’t either recollapse immediately or fail to form even the basic building-blocks of matter" Or perhaps there is an infinite number of Universes and big bangs out there, and ours was just one of the possibilities, while billion other big bangs "failed" in recreating our conditions.
- mamcx 12y ago
  A question: So how far more complex, and fine tunned must be the outer universe so it could fork inner universes? Because then the outer universe purpose is build universes. And must be solid enough to not be corrupted by the inner universes badly laws. So, a operating system?. This make the answer far more complex, just to try to avoid the fine tunned of the universe, methinks.
chrischen 12y ago
"Because while the laws of physics set the rules for how a system evolves over time, it still needs a set of initial conditions to get started. " I thought it wouldn't evolve deterministically? So what is he talking about here?
houseofshards 12y ago
Doesn't this question have something to do with uniform distribution of matter and energy in the early universe ? The details elude me right now, but I heard a talk/panel discussion about this - basically the hypothesis presented was that in the early universe, matter had a very uniform distribution as it was confined to a very tony space. This means a black hole could not have formed since there was no point whose gravitational force was greater than any other point.
ck2 12y ago
Maybe there are millions of other fecund universes where their big bangs did fail for lack of enough mass or enough energy to move fast enough or too fast to form atomic bonds. So just like life in our galaxy may be a one in million chance, our universe it itself may be a one in a million chance.
graycat 12y ago
Maybe the OP is saying that at the big bang, there was our present universe, and it was small, maybe the size of our solar system, maybe a baseball, maybe smaller. But, whatever, it was small, and, most important, that's all there was. There was nothing more. It was not a very dense, very hot chunk of matter-energy, whatever, inside some larger space. Instead, that's all the space there was. Then the OP is saying that in that context, where the whole universe was just that ball, the old arguments on forming a black hole don't hold. Instead, what happened was, space itself, that is the whole universe itself, explosively expanded. And it's still expanding. So, what was that universe 'inside' and what has it been expanding 'into'? Either these are poorly posed questions, or we don't know, or, for the question in the OP, it doesn't matter. Maybe that's what was going on in the OP. Maybe.
- nextw33k 12y ago
  That then begs the question, could you destroy a black hole? If we had the ability to alter the fabric of spacetime, could we shrink that fabric so that the black hole either imploded or exploded?
  - graycat 12y ago
    I thought that the question was, why didn't the universe collapse into one black hole right at the beginning? With the argument I tried to outline, there was no black hole. The reason is, in short, the situation was not like where black holes are formed since then. The big difference is that, (1), now, the matter-energy for a black hole is in some region of space in our universe where that region is surrounded by the rest of the universe, and (2), then, the matter-energy filled the entire universe that there was, even if it was only the size of a baseball. Then, that matter-energy filled the whole thing. For that whole thing to have created some small black holes, the thing would have had to have partitioned into separate chunks. But apparently what happened is that the space expanded explosively, really before anything could collapse. Or, maybe the expansion was so fast that quarks, as close together as in protons now, soon were being separated faster than the speed of light and, thus, had no choice but to generate more quarks and, thus, more matter. We're talking really explosively rapid expansion. Or maybe the gravitational field of some matter-energy wanted to propagate at the speed of light, reach out, and connect with more matter-energy, but before that gravitational field had moved even 1 mm, space had expanded so much that the other matter-energy to be reached had already move to a few light years away. We're talking explosive, so fast that speed of light is so slow as to be nearly standing still and irrelevant. At least that is my intuitive understanding.
barrystaes 12y ago
If our universe was inside a "black hole" seen from the outside, how would we ever know? For al we know the percieved timescale of the big bang and the time since it is just timedialation, and that black hole might even exists in more than 3D.
jsonmez 12y ago
Pretending like we even have a clue of what happened at the beginning of the universe... blah...
gonvaled 12y ago
What if the universe is a black hole, with a very big (and growing?) Schwarzschild radius? That nothing can escape a black hole does not mean nothing can't exist within a black hole ...

58 points by lelf 12y ago

simpler question - the Universe's end game - given currently observed dynamics does it lead to one gigantic black hole inside very thinly expanded very cold vacuum (with CMB temperature practically 0 instead of 2.7 degrees K today) or to many of such black holes and what would be their distribution?

MAGZine 12y ago
The universe's end game is to expand forever until it's eventual heat-death. As far as science is aware, anyhow.
millstone 12y ago
Black holes eventually evaporate due to Hawking radiation. The current thinking for the very-long-term fate of the universe is the "Dark Era:" nothing except photons, neutrinos, and the occasional electron or positron.

aikah 12y ago

So basically,is he saying that the universe we are in is an "unlikely outcome" of a phenomenon? So basically the universe was created "by chance"?

darkmighty 12y ago
I think it's not a probabilistic matter, but more a way of framing Occam's razor. If you allow enough "tunable" variables with just the right values you can easily make a theory fit any observation. For this reason theories including variables requiring a lot of precision to generate our universe are looked with distrust by physicists, I believe.

ars 12y ago

Summary: Because the energy of the Big Bang was moving, and the Schwarzschild radius is for stationary mass. And I'm sorry, but this explains NOTHING. Even for moving mass the density was enough to make a black hole. So presumably the density never actually got that high, or there is some other explanation we are not aware of. He should have just said: We don't really know. Because we don't. Why is there this requirement that science be able to explain everything? Is it because it's held up as an alternative to religion so people are petrified that if there are any holes people will say "sciences knows nothing, back to religion"? (Now that I've setup my strawman I'm going to knock it down.) First of all Science and Religion are not competing for adherents. You can believe that God created the universe and still want to investigate how he did it, and what the details are. Even if you believe the Big Bang never actually happened (i.e. it's an off-camera backstory), you can still be interested in investigating it because if God made it look like that then it's important. Second the whole point of science is saying "I don't know", otherwise it's a religion, not science.

trhway 12y ago
>So presumably the density never actually got that high, or there is some other explanation we are not aware of. density don't need to be high to get a black hole - the more the mass the less its minimal density has to be when black hole can be formed - the Schwarzschild radius of our Universe (which is mostly space with the specks of matter) is on the scale of 10B+ light years for example. So depending on how it is calculated and a lot of other stuff - we still can be inside expanding black hole :)
- AnimalMuppet 12y ago
  Disclaimer: I'm speculating further than my knowledge of physics. But if you add dark matter, could that push the Schwarzchild radius of the universe to 13B light years? That is, to the (observable) radius of the universe? If so, then is it possible that the red shift of distant objects is a black hole effect (remember that in this scenario, we're inside the event horizon), rather than due to the expansion of the universe? Would this also explain dark energy? It would require that red-shifts in a black hole be non-linear in distance, which I think is plausible, and that they be non-linear in the right direction, which I don't know enough to say anything whatsoever about.

neduma 12y ago

Related video: https://www.youtube.com/watch?v=2XkV6IpV2Y0&list=PLFs4vir_WsTwwb2zqmtE2WTEFdc7AQHnc https://www.youtube.com/watch?v=2XkV6IpV2Y0&list=PLFs4vir_Ws...

eridius 12y ago

Superficially interesting article, but it didn't actually answer the question very well. As near as I can tell from this article, the answer is basically "because it was expanding". It then went into a discussion about the possible behaviors of the universe over time, i.e. expanding indefinitely, having its expansion rate become static, or collapsing. But this discussion is tangential to the question. I also don't like how the discussion at the end was phrased. It started talking about fine tuning and making a mathematical argument as to the chances that our universe would have exactly the amount of mass it does (which I believe makes the assumption that the mass in our universe is random, though it was never stated). The problem with this is it's basically the argument that our universe must have been made by some external entity (i.e. "God"), without actually saying as much. I say this because there's no other good reason to try and make claims about the statistical likelihood of our universe having the initial conditions it did. And of course, it completely failed to mention that of course the universe's conditions are just right for it to have produced stars and planets and eventually life, because otherwise we couldn't be talking about it. There's a pithy name for this, but I forget what it's called. It also failed to mention the trivial solution to getting a universe that's fine-tuned just right, assuming random initial conditions, that doesn't require invoking any kind of supernatural being: infinite universes.

ssivark 12y ago

IMHO, that was a very long-winded non-explanation. Basically the "answer" comes down to this: 1. We really don't know. We don't understand the rules of physics well enough to model the behaviour of stuff in such "extreme" situations. 2. If you still insist on asking that question, I could give you a plausible explanation of why the question is not really the right thing to ask: "small" black holes tend to evaporate very quickly through the process of Hawking radiation -- in effect producing photons, matter, and every possible kind of "stuff". So even if there was something akin to a black hole, early in the universe, (and if we could apply our rudimentary understanding of gravity and quantum mechanics to even talk about black holes and Hawking radiation) it wouldn't trap the stuff for long... in fact it would be spewing out stuff in copious amounts, and very quickly at that.

idlewords 12y ago

"one part in 10^24, which is kind of like taking two human beings, counting the number of electrons in them, and finding that they’re identical to within one electron" I hate to be pedantic... wait, I LOVE to be pedantic. If you consider a human being to be a 50kg bag of water, that's 2750 moles of water, or ~1.7 * 10^27 molecules. Each molecule has ten electrons, so this factoid is off by about four orders of magnitude. More if the person had a big bowl of electrons for breakfast that day.

sarreph 12y ago
I'm not sure a 'bowl of electrons' would be that great an example either ;) (density, etc)... Just being pedantic!

higherpurpose 12y ago

> What’s remarkable is that the amount of fine-tuning that needed to occur so that the Universe’s expansion rate and matter-and-energy density matched so well so that we didn’t either recollapse immediately or fail to form even the basic building-blocks of matter" Or perhaps there is an infinite number of Universes and big bangs out there, and ours was just one of the possibilities, while billion other big bangs "failed" in recreating our conditions.

mamcx 12y ago
A question: So how far more complex, and fine tunned must be the outer universe so it could fork inner universes? Because then the outer universe purpose is build universes. And must be solid enough to not be corrupted by the inner universes badly laws. So, a operating system?. This make the answer far more complex, just to try to avoid the fine tunned of the universe, methinks.

chrischen 12y ago

"Because while the laws of physics set the rules for how a system evolves over time, it still needs a set of initial conditions to get started. " I thought it wouldn't evolve deterministically? So what is he talking about here?

houseofshards 12y ago

Doesn't this question have something to do with uniform distribution of matter and energy in the early universe ? The details elude me right now, but I heard a talk/panel discussion about this - basically the hypothesis presented was that in the early universe, matter had a very uniform distribution as it was confined to a very tony space. This means a black hole could not have formed since there was no point whose gravitational force was greater than any other point.

ck2 12y ago

Maybe there are millions of other fecund universes where their big bangs did fail for lack of enough mass or enough energy to move fast enough or too fast to form atomic bonds. So just like life in our galaxy may be a one in million chance, our universe it itself may be a one in a million chance.

graycat 12y ago

Maybe the OP is saying that at the big bang, there was our present universe, and it was small, maybe the size of our solar system, maybe a baseball, maybe smaller. But, whatever, it was small, and, most important, that's all there was. There was nothing more. It was not a very dense, very hot chunk of matter-energy, whatever, inside some larger space. Instead, that's all the space there was. Then the OP is saying that in that context, where the whole universe was just that ball, the old arguments on forming a black hole don't hold. Instead, what happened was, space itself, that is the whole universe itself, explosively expanded. And it's still expanding. So, what was that universe 'inside' and what has it been expanding 'into'? Either these are poorly posed questions, or we don't know, or, for the question in the OP, it doesn't matter. Maybe that's what was going on in the OP. Maybe.

nextw33k 12y ago
That then begs the question, could you destroy a black hole? If we had the ability to alter the fabric of spacetime, could we shrink that fabric so that the black hole either imploded or exploded?
- graycat 12y ago
  I thought that the question was, why didn't the universe collapse into one black hole right at the beginning? With the argument I tried to outline, there was no black hole. The reason is, in short, the situation was not like where black holes are formed since then. The big difference is that, (1), now, the matter-energy for a black hole is in some region of space in our universe where that region is surrounded by the rest of the universe, and (2), then, the matter-energy filled the entire universe that there was, even if it was only the size of a baseball. Then, that matter-energy filled the whole thing. For that whole thing to have created some small black holes, the thing would have had to have partitioned into separate chunks. But apparently what happened is that the space expanded explosively, really before anything could collapse. Or, maybe the expansion was so fast that quarks, as close together as in protons now, soon were being separated faster than the speed of light and, thus, had no choice but to generate more quarks and, thus, more matter. We're talking really explosively rapid expansion. Or maybe the gravitational field of some matter-energy wanted to propagate at the speed of light, reach out, and connect with more matter-energy, but before that gravitational field had moved even 1 mm, space had expanded so much that the other matter-energy to be reached had already move to a few light years away. We're talking explosive, so fast that speed of light is so slow as to be nearly standing still and irrelevant. At least that is my intuitive understanding.

barrystaes 12y ago

If our universe was inside a "black hole" seen from the outside, how would we ever know? For al we know the percieved timescale of the big bang and the time since it is just timedialation, and that black hole might even exists in more than 3D.

jsonmez 12y ago

Pretending like we even have a clue of what happened at the beginning of the universe... blah...

gonvaled 12y ago

What if the universe is a black hole, with a very big (and growing?) Schwarzschild radius? That nothing can escape a black hole does not mean nothing can't exist within a black hole ...