Why didn’t the Universe become a black hole?

https://medium.com/starts-with-a-bang/ask-ethan-50-why-didnt-the-universe-become-a-black-hole-f4da68466e21

by lelf • 12 years ago

58 39 12 years ago

trhway2• 12 years 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• 12 years ago

The universe's end game is to expand forever until it's eventual heat-death.

As far as science is aware, anyhow.

millstone• 12 years 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• 12 years 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• 12 years 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• 12 years 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.

trhway2• 12 years 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• 12 years 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.

coldtea• 12 years ago

First of all Science and Religion are not competing for adherents.

Well, in abstract no. But then again, they are the result of people practicing them (science or religion), and those do compete for adherents.

whyever• 12 years ago

Even for moving mass the density was enough to make a black hole.

You are making an assumption here that is debatable. We understand very little of the physics close to the Big Bang. Those scales in energy, time and space are so extreme that quantum effects are expected to be dominant. However, all theory about black holes uses general relativity, which does not account for such scales. It is still an open problem to unite quantum physics and general relativity (i.e. this is basically what string theory hopes to achieve).

And I'm sorry, but this explains NOTHING.

I think the point is that the assumption made to derive the theory about black holes from general relativity are just not met. The Schwarzschild radius is not defined for non-static spacetime, so it does not apply here.

It is true that it explains nothing, but it also means that you cannot use the Schwarzschild radius in your argumentation.

calinet65• 12 years ago

It's actually not that at all.

This image tells it all: https://d262ilb51hltx0.cloudfront.net/max/953/1*QXypiHUwjJZr...

What he was saying is, if there was just 1 gram per cubic cm less mass in the original universe, then it would expand too quickly to form any complex structures and the universe as we know it would not exist. And if it was just a few grams per cubic cm more massive, then it would collapse immediately as in the original question.

The reason our universe did not immediately collapse is not a mystery. It was a tiny amount less massive than would be required for such a collapse.

The reason it was perfectly on the line is no mystery whatsoever: if it were one gram over, it would collapse, and we would not exist, and thus we would not be asking the question. Same if it were one gram less; the universe would be too sparse for life to organize.

This is not a miracle or a mystery, it's simply fact. Billions or trillions of universes might have sprung into existence over billions or trillions or perhaps even infinite aeons of time, each with different masses and parameters of physics.

The one that produced an observer was observed. That's us, and that's it. No miracle, no mystery.

It's like someone winning a lottery. The chances of a specific individual winning are next to nothing, but the chances of anyone winning are 100%. If a news crew then goes and finds the winner, they will surely find an astounded, surprised, and very lucky feeling person. But the news crew will not be surprised, since their observation is entirely expected and even guaranteed.

Humanity is both the winner and the news crew in this situation, by the simple property of our ability to observe our own existence.

This is called the anthropic principle. It also applies with zero modification to the question of why Earth appears to be such a perfect planet to support human life, especially as we begin to discover that there are literally trillions of planets in our universe. We should not be surprised that we observe the one that happened to have the conditions conducive to the evolution of a sentient observer. But you could be forgiven for feeling very lucky that you're one of them.

jaekwon• 12 years ago

I like this sentence...

The one that produced an observer was observed.

I wonder if it applies in other contexts, specifically, er, quantum decoherence?

nerfhammer• 12 years ago

Doesn't this assume that "we" had multiple chances to exist? That if a universe existed that collapsed "we" would just move on to the next universe until we settled on one that we could exist in? This almost sounds like we were rejecting universes.

marcosdumay• 12 years ago

That summary is not entirely correct. It's not because everything was moving, but because space was getting bigger. A very different phenomenon.

Why should he say that he does not know when the best accepted theory fits reality almost perfectly on that case? The correct thing to say is that he knows.

Also, if you look carefully enough, we know of no matter that escaped the Universe, as far as we know, it fits exactly the property of the Schwarzschild's black holes.

wyager2• 12 years ago

First of all Science and Religion are not competing for adherents.

In practice, how are they not? There are at least 3 major classes of popular religions that claim that the earth is only 6000 years old, among a smattering of other objectively false claims. One cannot correctly claim these facts are or might be true and also observe the scientific method.

Yes, a hypothetical religion that posits nothing more than "there is a god" would not technically directly contradict the known body of scientific knowledge, but it would still contravene the scientific method.

vacri• 12 years ago

Most Christians don't claim the earth is only 6000 years old - that's only a particular brand of fundamentalist. There are plenty of religious people in science, even prominent in science - they are just mostly moderates, and learn to not publicise their religion to avoid conflict.

The thing is that while the root of Christianity and science aren't compatible, the everyday practice of Christianity has little to do with that root. It's just some initial justificiation that doesn't really touch the everyday. The congregation are generally not so interested in the philosophical underpinnings than the daily practice. Praying to a saint that can't be proven, lighting a votive candle, or dropping money in the poor box does not compete with investigating atoms.

neduma• 12 years ago

eridius• 12 years 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• 12 years 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• 12 years 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• 12 years ago

I'm not sure a 'bowl of electrons' would be that great an example either ;) (density, etc)...

Just being pedantic!

higherpurpose• 12 years 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• 12 years 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• 12 years 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• 12 years 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• 12 years 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.

graycat2• 12 years 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• 12 years 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?

graycat2• 12 years 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• 12 years 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• 12 years ago

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

gonvaled• 12 years 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 ...

Why didn’t the Universe become a black hole?

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