Why the Universe Didn't Become a Black Hole 109
StartsWithABang writes: With some 10^90 particles in the observable Universe, even stretched across 92 billion light-years today, the Universe is precariously close to recollapsing. How, then, is it possible that back in the early stages after the Big Bang, when all this matter-and-energy was concentrated within a region of space no bigger than our current Solar System, the Universe didn't collapse down to a black hole? Not only do we have the explanation, but we learn that even if the Universe did recollapse, we wouldn't get a black hole at all!
Thats a no brainer! (Score:1)
I mean the universe collapses in the beginning ... then it is a 'black hole' ...
But you can only see form the outside that there is a black hole! As there is mo outside of the universe you can not observe it, hence you don't notice the black hole, hence it is not there.
QED
Oh! That was simple!
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The Hitchhiker's Guide to the Galaxy, "Universe":
1. Area: Infinite. Bigger than the biggest thing ever and then some. Much bigger than that in fact, really amazingly immense, a totally stunning size, real "wow, that's big," time. Infinity is just so big that, by comparison, bigness itself looks really titchy. Gigantic multiplied by colossal multiplied by staggeringly huge is the sort of concept we're trying to get across here.
2. Imports: None. It is impossible to import things into an infinite area, there b
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The universe seems to be expanding faster and faster. Dark Energy is coming from nowhere to do that work.
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Well, it violates the weak energy condition, although it does satisfy (just) the strong energy condition. The weak energy condition says that density + three times pressure is greater than zero, and that's pretty easy to violate if you've got a scalar field. The strong energy condition says that density + pressure is greater than zero, which is far harder to violate; dark energy is right on the border of it, and a cosmological constant *is* the border (pressure = - density).
Of course, you're totally right -
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Dark "energy" is probably a false description, or a misleading one. Dark energy is thought by many to simply be a property of space-time itself. It isn't being added, it is just what happens to space-time in this configuration or density.
Much like a rubber band will be elastic up to a certain point, and then full stop, the universe could also hit such a point with no warning (because that point has never been reached before) and then change its acceleration again, or even suddenly boomerang back. Until w
Because of the expansion (Score:5, Interesting)
You can't use the Schwarzschild radius calculation for expanding space. The only kind of new part was the bit about not becoming a black hole if it should re-collapse.
Re:Because of the expansion (Score:5, Insightful)
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A survey of what's on TV will confirm that.
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The only kind of new part was the bit about not becoming a black hole if it should re-collapse.
Which he stated, but did not attempt to explain.
I always wondered why collapsing matter would drag space with it. After reading the link, I still do.
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As far as I understood the physics, it was because "space" doesn't have a set of well-defined borders with customs etc. but is a curved area, where the curve is defined by the energy available inside the universe (energy == mass). Once the whole thing collapses it should curve the area much steeper, "contracting" the universe.
But I may be totally off base here, I'm not a physicist.
Because of the expansion (Score:1)
Yes you can use the Schwarzschild argument. Expanding space is only a handwaving rationalization, a coordinate-dependent way of thinking that is not compatible with the principle of general covariance.
If the gravitational source density was ever more than zero, then it follows that the contents of the universe were less massive in the past. In an inertial set of coordinates, not the screwy Freidmann coordinates, it can be understood that the shards of the Big Bang, flying apart at next to lightspeed, still
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Yes you can use the Schwarzschild argument. Expanding space is only a handwaving rationalization, a coordinate-dependent way of thinking that is not compatible with the principle of general covariance.
I've never heard anything about that, care to explain? It also seems contrary to what I know, see below.
A less-known fact about black holes is that the bigger they are, the lower the density. If you use the Schwarzschild radius, for an arbitrarily large mass, the radius gets arbitrarily large, and the density gets arbitrarily close to zero. If this applied to expanding space, then it wouldn't be an open question as to whether the universe was infinite or not, as if it were we would be guaranteed to be in a
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Actually, because of the principle of general covariance, it is necessary for academics to show that their cosmological calculations work in different coordinates. Thinking that is bound to special coordinates such as the Freidmann coordinates will only be confused by the fictitious forces exhibited therein. The standard mathematical precautions taken against this sort of problem have failed in this case.
Relativity itself disallows the necessity of thinking that space inherently expands or contracts. The pr
Business relationship (Score:5, Interesting)
So does ./ have some kind of promotional relationship with startswithabang? If so you should disclose it.
The blog does have interesting material, and its appropriate for /., so its not like its bad that every article on there is making the /. front page. But its kind of odd that every article on there is making the ./ front page.
Summary (Score:1)
So to extrapolate from the TFA: The laws of physics do not exist in a vacuum...
Someone give this guy an xkcd award, then punch him in the face.
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Does it matter which brand of vacuum? Or which style?
Re:Summary (Score:4, Interesting)
So to extrapolate from the TFA: The laws of physics do not exist in a vacuum...
There's a difference between 'a vacuum' and 'nothing'.
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So to extrapolate from the TFA: The laws of physics do not exist in a vacuum...
There's a difference between 'a vacuum' and 'nothing'.
\ Nothing is emptier than a vacuum!
Early universe (Score:2)
Hadn't they proved (mathematically) that just after the big bang there was a time (inflation) when it was expanding faster than light. If you are going faster than light then you can escape from a black hole.
Re:Early universe (Score:4, Interesting)
If you are going faster than light then you can escape from a black hole.
There is no part of physics that says speed has anything to do with escaping a black hole. If you could produce enough thrust to travel at just one meter per billion years, you could escape a black hole ... assuming you could keep that speed while inside the event horizon of the black hole. Unfortunately, from a mathematical perspective this appears to be impossible.
After a certain point (the event horizon) light simply bends two quickly back on itself to escape a black hole and stays inside the radius of the event horizon. It doesn't slow down, it changes directions, because space is all sorts of fubar inside the event horizon of a black hole.
What they've proved mathematically as that at the event horizon of a black hole the math fails. It falls apart and no longer makes any sense because the numbers get too large on one side of the equation.
In reality, this doesn't mean 'nothing can escape a black hole'. It means 'nothing we've observed can escape a black hole'. Well, except it can. Hawking radiation escapes a black hole as it evaporates, but all the explanations for why are just silly as they are pretty arbitrary compared to 'light' not escaping.
Another obvious but often overlooked theory is that our universe IS a black hole inside a larger universe. It explains a great many aspects that don't make sense ... but then it also introduces a whole bunch of aspects that don't make sense without making a bunch of assumptions about what is outside our universe, and these assumptions are so absurd from our view point that we just assume they are false.
The truth of the matter is ... science knows a lot less than they claim to about black holes, the big bang, and the nature of the universe. Many scientist treat theories with holes the size of the planet in them as obvious fact when they are no such thing. They have no fucking clue why the universe exists in the state it exists today, but many of them refuse to acknowledge that FACT to anyone. The good ones do. Einstein as an example, had no problem admitting his theories were nothing more than theories and that they were often wrong because they were simply based on the little bits of the universe we can observe.
Re:Early universe (Score:5, Interesting)
"What they've proved mathematically as that at the event horizon of a black hole the math fails. It falls apart and no longer makes any sense because the numbers get too large on one side of the equation."
Not so. The maths dies at the singularity at the centre of the hole, but it doesn't at the event horizon except in a badly-chosen coordinate system. Alas, the usual coordinate system we'd present the Schwarzschild solution in is indeed badly-chosen and has an apparent singularity at the horizon, but this is not an actual singularity, as can be seen quickly by calculating a scalar curvature invariant - the Ricci scalar is the immediate choice, it's basically a 4d generalisation of the more-familiar Gaussian curvature - and seeing that it's entirely well-behaved except at the centre of the hole. So we look for a coordinate system well-behaved at the horizon and quickly come across Painleve-Gullstrand coordinates, in which spacetime is locally flat and perfectly behaved at the horizon. The implication is the poor sod wouldn't be able to tell that he'd got to the horizon, except through tidal forces (which depend on the size of the hole), and then he'd struggle to navigate before slamming into a singularity.
Even more confusingly, for a *realistic* hole, the insides are rather different. A Schwarzschild hole has a singularity inevitably in the future - all future-directed paths one can travel on, or light can travel on, end at the singularity. That's a bit of a bummer if you happen to be in a Schwarzschild hole. But a Schwarzschild hole is not physical; it is a non-rotating, uncharged hole, and that's not a realistic setup. In a charged (Reisser-Noerdstrom) or a rotating (Kerr) or, come to that, a charged rotating (Kerr-Newman) hole the singularity is "spacelike" -- there exist paths on which we could, in principle, travel, that avoid the singularity. In the case of a Kerr(-Newman) hole it's even smeared out into the edge of a disc. In reality, good luck navigating in there, but the singularity is not inevitably in the future in there.
A bit closer to the point, you're right that speed doesn't really have anything to do with it. Instead it's the type of path you can travel on, and where *they* go. An event horizon can be defined as the surface on which "null" geodesics, on which light travels, remain equidistant from the hole. If you travel, as massive particles do, on a "timelike" geodesic then you're fucked; you're never going to be able to accelerate enough that you even travel on a null geodesic, let alone a "spacelike" geodesic along which you can basically access anywhere. On a spacelike geodesic you could get out of a hole no problem. You could also travel in time, and you could break causality fifteen times before breakfast. I'd like to travel on a spacelike geodesic - it would be fun. Though managing to get back to a timelike geodesic might be significantly less so.
"Another obvious but often overlooked theory is that our universe IS a black hole inside a larger universe."
That's an extraordinarily strong statement. Our universe might be indistinguishable from a black hole from the outside, yes, but there's a big "might" in there, and an "outside" that doesn't necessarily make much sense either. It all depends on the setup you're assuming. Sure, we could end up finding that the universe is "inside" a black hole for a given definition of "universe", "inside" and "black hole", or we might find that that statement does not make any extent. I wouldn't want to say anything stronger than that, frankly, not least as I'm aware of models of cosmology that are observationally indistinguishable from a standard, infinitely-extended, flat universe, which are also flat, but which have finite extent. One way to do so is to simply put the universe into a toroidal topology. Since GR is a local theory it says nothing about topology, and it would be hard to argue that a universe extended on a torus would look like a black hole from the "outside", since that would be the entire extent of spacetime.
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But do note that you're talking about the velocity at which space is expanding. (Yeah, I know you know that, but I still find it confusing.) This doesn't imply anything about how objects located within space can accelerate. And since in order to get that 5x c velocity you need to be an immense number of light-years away, even contemplating talking about their relative velocities gives me a headache. I mean, if it currently looks to us as if they are moving apart at 5x c, how fast would they be moving ap
Short version (Score:5, Informative)
If at some point in the past the mass of the universe was in a volume wholly contained within its own Schwarzschild radius, why did the universe not become (or, more accurately, remain) a black hole?
"...Schwarzschild’s solution is a static one, meaning that the metric of space does not evolve as time progresses. But there are plenty of other solutions—de Sitter space, for one, and the Friedmann-Lemaître-Robertson-Walker metric, for another—that describe spacetimes that either expand or contract."
Literally everything else in the article was off-topic, and I can't help but feel this highly evasive 'answer' might have been "Ask Ethan" admitting he just didn't know.
Which is a pity because it is a fascinating question.
If we're poking holes in the accepted dogma... (Score:2)
...then how about this one? [wikipedia.org]
One mystery which has not been solved as of 2009 is the absence of red dwarfs with no metals. (In astronomy, a metal is any element heavier than hydrogen or helium.) The Big Bang model predicts the first generation of stars should have only hydrogen, helium, and trace amounts of lithium. If such stars included red dwarfs, they should still be observable today, but none have yet been identified. The preferred explanation is that without heavy elements only large and not yet observ
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This is all hogwash.
At least that much of your theory is correct.
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Any material from an Earth-Theia collision would settle into predictable orbits shortly (in geologic time) after the collision. Presumably, this is well understood by scientists and they would pick material that is not from that predictable band.
Understand that space, despite the gigatons and gigatons of material out there, is not an unpredictable or chaotic place. It isn't just ping-ponging all over the place, messing people up. If you obtain material from a comet, asteroid, or even a particular type of
entropy (Score:3)
Wasn't there some conjecture some time ago that entropy decreased inside a black hole, and that our universe corresponded to a time-reversed version of a star collapsing into a black hole? Which of course would be interesting because the "arrow of time" would point two opposite ways in the "meta-universe".
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because the "arrow of time" would point two opposite ways in the "meta-universe".
This is a seriously silly question, but has any serious physicist conjectured that the "arrow of time" could have more than two directions? I mean, like going sideways or something? And what would be the bizarre implications of that?
terrible article (Score:4, Informative)
Stop posting links to medium.com... the worst Science site I've ever seen short of timecube... wait, actually timecubes at least entertaining.
All of their articles boil down to:
Subject "Could *insert some inane scifi topic* really be??"
10 pages of images scraped from geocities homepages, font type and spacing worthy of a freshman English paper and then...
No, not really, but thanks for reading!
You want real science news? Here you go: http://phys.org/physics-news/ [phys.org]
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It has a psychological effect because ignorant economists use limited knowledge about the universe to justify austerity policies. Friedman using TANSTAAFL, for example. Except now Dark Energy violates TANSTAAFL, and it didn't hold in General Relativity anyway. So we suffer from an artificially imposed scarcity of money because economists suffer from a lack of knowledge about the universe.
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It has a psychological effect because ignorant economists use limited knowledge about the universe to justify austerity policies. Friedman using TANSTAAFL, for example. Except now Dark Energy violates TANSTAAFL, and it didn't hold in General Relativity anyway. So we suffer from an artificially imposed scarcity of money because economists suffer from a lack of knowledge about the universe.
That's not rigorous enough for physics, but I do believe it meets the standards for good economics.
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The speed of light is a limit on how fast you can accelerate something *in* space, but it's not a limit on how fast space can expand.
In fact you can't even state the rate of expansion of space as a velocity, because the velocity apparent as the speed of recession depends on how far away you're looking.
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Actually, the claimed superluminal expansion is a coordinate artifact. Convert to a different set of coordinates and the expansion is understood as lightspeed at a maximum.
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I don't buy 92 billion light years.
You don't get (understand) 92 billion light years.
The observable universe is that big because, in the 13-14 billion years that light has been travelling from "out there" to here, space has been expanding. That means that the most distant objects we can see are now 90+ billion light years away. They weren't that far away when the light left.
Explain it like I'm not an astrophysicist (Score:1)
Because I'm not. But, where does the 92 billion light year thing come from? I would think what, 28 billion across if it's 14 billion years old?
Marty, you're not thinking 4th-dimensionally! (Score:2)
Perhaps the answer doesn't lie in the 3rd dimension.
One of the possible consequences of the curvature of 4th-dimensional space-time is that our universe may be a 3-dimensional surface of a 4th-dimensional hypersphere [goodreads.com]. And if the 4-dimensional universe is expanding, the 3-dimensional universe would expand too.
This model of the universe was also used in a famous sci-fi novel [goodreads.com].
Stable universe? (Score:2)
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It would certainly change the stability analysis, yes, but the universe does not have a significant angular momentum. That would leave a characteristic signature on the CMB, a preferred direction, and it's been hunted, with each new and improved dataset, and we still don't have it. The hunt has turned up other interesting anomalies such as the appallingly-named "axis of evil", but those signatures are also (probably) not due to an intrinsic net angular momentum. That doesn't say there isn't one, just that i
beware! (Score:1)
I was under the impression that it *IS* one... (Score:2)
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Hmm, in a black hole a theoretical photon trying to escape is sucked back in because of gravity. But what will happen when a photon hits the hypothetical edge of the universe? Bounce back? I haven't heard of anyone theorising that.
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Creator vs accident (Score:1)
One part in 10^24 is why having a Creator makes a difference. One part in 10^24 is no accident. And some people still don't what to admit what created the Big Bang but there is no other answer. How much faith does it take to believe all this was an accident?
What about the "some 92 billion light-years worth of space contained in a volume of space no bigger than our own Solar System"? That was a miracle. Accidents don't "give rise to all the wondrous diversity of nuclear, atomic, molecular, cellular, geologic
Or are we inside this black hole? (Score:2)
I wonder why nobody pointed out the real possibility of our 3D universe being inside a black hole.
I could even imagine temporal displacement causing us to see the bigbang as a instant event, while on the outside its just near ethernity.
I've often wondered about this, only to end up with the question how many black holes deep we are..
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From TFA, "As it turns out, we live almost in the Goldilocks case, with just a tiny bit of dark energy thrown in the mix ... 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 if not religion in disguise, you can call it religion in searching at least. From Acts 17:27, "God did this so that they would seek him and pe
Re:Big Bang is RELIGION (Score:4, Funny)
In related news, ants develop a religion around the question of why they have not been stepped on by an elephant.
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Sure, in an imaginary world where the graceful and faithful elephant works freakishly hard to make the ants live happy lives even though the ants are so tiny to imagine what this great elephant looks like or means to them. The ants who hate the elephant drown themselves in puddles of water, and we the outsider look at these drowning ants in this imaginary world and think "these ungratefully stupid ants deserve to be eliminated by natural selection." And the elephant looks at us and say "if we can save one more ant from drowning, then why don't we?"
Well, that is a good question. What can't we? Also another good question is: How do we know we aren't already inside a black hole? No one has ever been to one or seen its inside so all we have is good guesses.
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I just learned on Facebook that cats have a religion, and it is 'catolisch' ... to understand this you need to be german or have a similar language like dutch or perhaps a scandinavian one ... but its funny!
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I think we can use the English equivalent: Cat-holic :)
Cat addiction (Score:2)
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Hehe, funny :D
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From TFA, "As it turns out, we live almost in the Goldilocks case, with just a tiny bit of dark energy thrown in the mix ...
Umm...70+% of the universe [howstuffworks.com] is "just a tiny bit" [chartsbin.com]?
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In case you're feeling a bit dense today, I believe the author meant tiny bit by volume, not mass, since the expansion of the Universe concerns volume.
You are very welcome.
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In case you're feeling a bit dense today, I believe the author meant tiny bit by volume, not mass, since the expansion of the Universe concerns volume.
You are very welcome.
Not feeling particularly dense at the moment, but thanks for asking! Your point did get to me read TFA, though.
Since IANAP, perhaps I'm a bit confused, but as I understand it, dark energy "can have such a profound effect on the universe, making up 68% of universal density, only because it uniformly fills otherwise empty space." [wikipedia.org]
What is more, volume "is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance (solid, liquid, gas, or plasma) or shape o [wikipedia.org]
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It's kind of useless arguing with me since I shouldn't be putting words in the mouth of Ethan Siegel, and arguing on whether it is appropriate to call dark matter tiny really has no bearing on what I'm telling you about God and the Universe. But just in case you find it a pleasure to discuss these fine points with me, the very notion of mass distributed over volume involves statistics, and as you know, you can make statistics tell any story.
Consider this figure [frontiersin.org] that I just randomly found so I don't have to
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Can't you folks see it is just religion disguised as science, how it implies a divine hand?
No, you're thinking about the Divine Monkeyspank hypothesis, which is indeed religion, but not disguised as science.
p.s. - Your troll score is: 0
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No point splitting hairs over what qualifies as "religion," but if this is the case, then there's more evidence for the Big Bang than for any other religion ever devised in the history of humanity, and that's saying something.
The evidence (which is nothing new, BTW) is amazing though. If the density of the universe were too low, or too high, we wouldn't have a universe to live in today. OK, that's not too odd - big crunch one way, big rip the other. What's astonishing is that the required density in the 1 ns universe to allow our universe to reach its current age must be correct to 24 significant digits.
Talk about fine tuning! One part in 10^24 higher or lower, and no universe today. That's about as anti-Copernican as you c
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Either we accept the "hand of god" in tuning the universe so precisely, or (far stupider IMO), we believe some silly anthropomorphic principle, or we simply accept that the physics is incomplete.
While I agree the last explanation is probably the most likely one (a dampening effect that occurs at a certain point could be a plausible explanation), don't discount nr. 2: we just don't know (and we cannot know) how many universes are generated at any given point in time. Perhaps quantum fluctuations generate 1 billion "universe seeds" per cubic centimeter at any given second, and since they are random, most don't lead to another universe. Some do, and the ones that are "exactly right" give rise to unive
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There's nothing wrong with the anthropic principle, it just can't be used as the explanation of what is happening. It is not a physical theory.
It simply states that, "the existence of the human inhabitable universe proves only that the existence of such a universe must be possible, because we are here to observe it." It's almost tautological.
It doesn't prove nor disprove deities, or the scientific method, or any theories derived therein. It is only useful for logically refuting the unproven assumption th
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There's a quite important principle in science, generalized from the Copernican principle, that theories that require a lot of "fine tuning" of constants in order to work are bad. The big problem with the anthropic principle is that it's too often used as an excuse to ignore the glaring weaknesses in some areas of science. We shouldn't be comfortable with such things (and for the most part, of course, scientists aren't). It's not that the anthropic principle is some overt fallacy, but it really makes me
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Re:because... GOD! (Score:4, Funny)
God is the fundamental reason for why the universe didn't became a black hole in the early stages after the Big Bang
I can stated with equal evidence and authority that the stray cat I almost ran over yesterday is the fundamental reason for why the universe didn't become a black hole in the early stages after the Big Bang.
Be glad I missed him.
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God is the fundamental reason for why the universe didn't became a black hole in the early stages after the Big Bang
I can stated with equal evidence and authority that the stray cat I almost ran over yesterday is the fundamental reason for why the universe didn't become a black hole in the early stages after the Big Bang.
Be glad I missed him.
Ok, let's hear it.
[clears throat] "the stray cat I almost ran over yesterday is the fundamental reason for why the universe didn't become a black hole in the early stages after the Big Bang."
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No, my life would have been changed (i.e., ended in the cosmic collapse) if I *had* hit him.
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A change to the density of the universe is likely what triggered a phase change in space-time to bring us to a now-accelerating expansion of the universe. Movement of the mass of that cat away from a storage facility with a number of tons of heavy metals could well have prevented the density figure in this part of the universe from reaching a critical point which causes another phase change.
Of course, the problem with that is that the change would then have happened about an hour later when came over to in
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Where do I mail my Thank You gift to?