
Why didn’t the Universe become a black hole? - lelf
https://medium.com/starts-with-a-bang/ask-ethan-50-why-didnt-the-universe-become-a-black-hole-f4da68466e21
======
ars
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.

~~~
calinet6
It's actually not that at all.

This image tells it all:
[https://d262ilb51hltx0.cloudfront.net/max/953/1*QXypiHUwjJZr...](https://d262ilb51hltx0.cloudfront.net/max/953/1*QXypiHUwjJZrMtdhAQcpZA.png)

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
I like this sentence...

> The one that produced an observer was observed.

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

~~~
HanyouHottie
You need to be careful with this line of reasoning if you mean what I think
you mean.

I've found that when speaking with laypeople about quantum decoherence, a very
common misconception comes from the use of the word 'observer' (see:
[http://www.imdb.com/title/tt0399877/](http://www.imdb.com/title/tt0399877/)
). If you say "A quantum system can be in a superposition until its wave
function is collapsed when it's observed.", a layperson can easily interpret
that to mean that a sentient being needs to look at and take note of the
system for it to count as being observed, when in fact all that is required is
that an external particle interact with the system and carry away some
information (energy).

There's nothing special about humans (and their ability to observe) in this
context.

~~~
calinet6
Yes. Observer in my post above specifically refers to a sentient being;
observer in quantum computing specifically does not. However given the
context, the two are (very) roughly similar. One could (again, very roughly)
think of the universe as a giant quantum computer solving for the variables
that lead to sentience. The observers are inside the system in that case, but
it's the same idea: create every possible state and select for the solution
that solves the problem.

Only an analogy, of course.

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

Just being pedantic!

------
eridius
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.

------
higherpurpose
> _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
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.

------
ssivark
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.

------
houseofshards
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.

------
graycat
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
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
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
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.

------
gonvaled
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 ...

------
ck2
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.

------
chrischen
"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?

------
neduma
Related video:

[https://www.youtube.com/watch?v=2XkV6IpV2Y0&list=PLFs4vir_Ws...](https://www.youtube.com/watch?v=2XkV6IpV2Y0&list=PLFs4vir_WsTwwb2zqmtE2WTEFdc7AQHnc)

------
aikah
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
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.

------
trhway
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?

~~~
millstone
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.

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

