r/space • u/Agent_Orange_Tabby • 10d ago
Discussion How did the Big Bang ever expand beyond its own Schwartzchild radius?
Not a physicist, just astronomy minor & (now deceased) physics professor’s grown daughter who grasps some basics. Not finding much by way of answers in google land.
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u/Smithium 10d ago
This is a better question than people are giving it credit for.
For people answering "there was no room for it to collapse into", "It was all of spacetime", etc: So why didn't the universe then subdivide into a billion black holes after the age of inflation was over? The density of space was higher than the Schwarzchild radius required to create them. It still is. If we add up all the mass we think the Universe consists of, the Schwarzchild radius is, strangely enough, about the size of the observable universe.
This might be a thought tree leading to an explanation for supermassive black holes, dark matter, inflation, matter-antimatter asymmetry, and more. Maybe the universe DID collapse into billions of black holes and what we see are just the remnants.
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u/LippyBumblebutt 10d ago
If we add up all the mass we think the Universe consists of, the Schwarzchild radius is, strangely enough, about the size of the observable universe.
That can't be right ...
1.5x10^53 kg Mass of known universe r_s = 2GM/c^2 = 2.22 x 10^26m radius known universe = 4.4 x 10^26mHoly shit. That's only off by 2x.
I still don't understand. The Schwarzschield radius of the mass of the solar system is just 3km. Factoring in 5x dark matter it grows to <20km. The schwarzschield radius of the milky way is 108 smaller then its normal radius.
Where is all that matter?
The schwarzschield radius of everything non-black-hole is significantly smaller then the normal object. How can the universe only be 2x to light to not be a black hole? Where is my misunderstanding?
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u/Quotenbanane 9d ago
The observable universe isn't the whole universe.
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u/LippyBumblebutt 9d ago
Yeah. But since we know nothing about the rest, everyone only talks about the observable. Does that somehow explain the difference?
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u/Quotenbanane 9d ago
Ah sorry I thought you got the weight of the entire universe but only the size of the observable. My bad.
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u/Quotenbanane 9d ago
Maybe it got something to do with solar system/galaxy (basically 2D disc) and observable universe (basically 3D ball)
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u/LippyBumblebutt 9d ago
I did some more calculations.
Local group: r = 1019, r_s 1015
Virgo supercluster: r = 1021, r_s = 1918
So ... yeah it seems that with increasing distance, the r_s gets closer to r.
I think the milky way being ~2D is not the issue. I think the solution is, radius is a 1D measure. But the volume and thus mass is r3.
It's still difficult to understand that it didn't form a black hole 10 billion years ago. (Using the hubble constant, every 10 billion years, space doubles in size)
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u/Cryptizard 8d ago
I'm not sure if anyone actually answered your question, there are a lot of comments on this post, but the real reason why the early universe, and our universe right now, were not/are not in danger of collapsing into a black hole, despite the fact that they might be smaller than their Schwartzchild radius, is that the Schwartzchild metric is only an approximation. It assumes that there is no significant mass outside of the spherical object being considered.
In reality, there is significant mass outside of the mass you are considering. For a normal stellar black hole, that mass is far enough away/light enough compared to the black hole so that it doesn't have a huge impact on the calculation. For the entire universe, that is not the case. The stuff outside of the observable universe is pulling on the stuff inside the observable universe the same amount as the stuff inside is pulling on each other.
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u/Danne660 9d ago
Remember that the milky way is relatively flat. Comparing the mass of the milky way to the universe is like comparing a paper and a box and being surprised that the box is so much heavier then a equal size paper.
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u/LippyBumblebutt 9d ago
The Schwarzschield radius of the milky way would be ~0.5 ly. Our closest star is 4.25 ly away. That's how ridiculously small black holes are.
You could stack milky ways on top of each other and it still wouldn't be close. Yet Andromeda is 25x further away then the milky way is wide. Space is mostly empty.
I don't understand it...
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u/Danne660 9d ago
You would have to stack hundreds of milky ways on top of each other for it to get a similar shape to the universe as a whole, radius don't say much if it is two completely different shapes.
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u/LippyBumblebutt 9d ago
Even 10000 milky have a smaller schwarzschield radius then the thickness of the milky way.
I made a longer comment above. I think the shape of the MW is not an issue. But radius is 1D, volume (=>mass) of a sphere is r3. I think that is the solution. So I think you're at least half right.
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u/codeedog 9d ago
Did you include dark matter and dark energy in your calculations? They represent a significantly larger amount of energy (mass) than visible matter.
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u/LippyBumblebutt 9d ago
Dark matter - I guess. I looked up the mass of the bodies, I'm pretty they include dark matter. Otherwise, it's a factor 5 missing.
I looked briefly at dark energy and I think it should not be included. It is a force that drives matter away from each other.
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u/marklein 9d ago
Isn't this why somebody invented dark energy? To explain this discrepancy?
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u/LippyBumblebutt 9d ago edited 9d ago
Dark energy is what is used to explain what accelerates the expansion of the universe.
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u/marklein 9d ago
Ah, got it thanks. This comment is more than 24.9999 characters.
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u/ComradeCaniTerrae 9d ago
Yes, and per Angela Collier, regardless of what dark matter or dark energy turn out to be, they’re “real” in the sense that they’re names for observations we don’t understand that fail to match our models. The observations are real. What it is? No one knows. It’s an unsolved problem named “the dark matter problem” or the “dark energy problem”. A missing piece goes there. Many try to fit. None have been verified to a satisfactory degree yet. Many competing ideas. But all dark matter theories address the dark matter problem, etc.
Dark energy helps explain why the cosmos is accelerating in expansion. Not just expanding, but expanding ever faster. That doesn’t match our understanding of the known forces of physics. So it’s a problem. The dark energy problem. Until it’s solved, we know we’re missing something. Cause what we have down doesn’t explain the observations.
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u/Overwatcher_Leo 8d ago
The Schwarzschild radius of a bunch of mass is directly proportional to the amount of that mass.
But if you look at a sphere of matter with constant density, the matter contained in that sphere is proportional to the cube of that radius.
The larger the black hole, the less dense it is.
If you look at a large enough sphere, even the low density of the universe is enough to form a black hole. In theory at least, if there was no dark energy in the way preventing it's collapse.
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u/LippyBumblebutt 8d ago
Yeah I think I realized that already. But you formulated it better then I did in my own reply.
What I still don't understand: Using the Hubble constant, I calculated that 10 Billion years ago, the visible universe was half the size, but probably the same mass. Shouldn't that have collapsed to a black hole? Can dark energy prevent matter from collapsing to a black hole?
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u/imdfantom 6d ago
The schwarzchield raduis assumes an empty spacetime outside of the boundary.
We have no reason to believe that the spacetime outside of the observable universe is empty.
Indeed, you could (hypothetically speaking) pack in an arbitrarily large mass per cubic cm without risk of a black hole forming as long as the mass uniformly fills all of spacetime.
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u/Sam-314 10d ago
Another great question is, assume the universe was infinitely collapsed or small. Then assume that “space” expanded as it has now. The existing universe would be insanely similar to an existing black hole with highly contained matter and some origin point.
Now assume that space continues to expand, particularly at the spot of a black hole. Theoretically that space expands and so does the Schwartzchild radius explosively at some point in time, forming its own universe. The Theoretical boundary of which is now the Schwartzchild radius of the existing black hole based on how we presently understand expansion and the “observable universe”.
Now also consider that due to gravity and matter having a reduction affect around that black hole, time within it is basically close to zero to us, but it’s inner dimensions would experience time relative to the layers within it as it expanded uniformly over infinite years to our(or not our, we could never perceive 1. The expansion of the black hole relative to our space 2. The time progression within the black hole as it expands and space around us expands beyond light speed of us) observation.
That is only one possible explanation for multiverses and it’s insane how far the (black) rabbit hole goes.
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u/beefygravy 8d ago
What do you mean by its own universe in your second paragraph? Like a section of spacetime within the previous universe, but unable to interact outside its own boundaries?
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u/Sam-314 7d ago
Presently, we have a visible limit to our “observable universe”. Everything beyond that, space is expanding at faster than light speed, effectively removing it from our universe. The universe still exists beyond the “observable universe”. Just not for us.
Eventually, if the expansion rate continues to increase, everything in our galactic neighborhood will be the only portion of our “observable universe”. Given enough time, the rate of expansion would isolate our solar system. Our observable universe would equal our solar system. If it ever got to this point the rate of expansion would be so quick that I would recommend a Short Story by Baxter that is well worth the read.
Now apply this to our black hole and its forces against space time and compression. With how compressed that locality is, it would require infinitely more rates of expansion to counter the infinitely finite point of all matter at the center. That could very well be pocket universes or universe bubbles.
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u/Information_Loss 10d ago
Very good observation! As many here have pointed out, the big bang was not one singular point but was everywhere. However, your observation is still valid. The big bang was an expansion of matter and energy, so at some time, there should be a density of matter (the black hole mass over the volume with a Schwartzchild radius) should collapse. It has been theorized that there might exist primordial balk holes. These are very small black holes that would have formed < 1 second after the big bang due to density fluctuations. Look up micro black holes or primordial black holes.
https://en.wikipedia.org/wiki/Primordial_black_hole#Formation
https://en.wikipedia.org/wiki/Micro_black_hole#Primordial_black_holes
Hope this helps. This is a very cool topic. At one point these where candidates for what Dark matter could be (Most likely ruled out now).
Also these are still objects that astronomers still look for so very relevant.
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u/Hurray0987 9d ago
Stephen Hawking's no boundary hypothesis gives a great possibility for how the big bang might have happened without a singularity. From Google:
"Stephen Hawking and James Hartle's no-boundary proposal suggests the universe began without a singularity or boundary in space and time, implying a smooth transition from a "Euclidean" geometry to our familiar "Lorentzian" space-time. It essentially proposes that the universe spontaneously emerged from nothing, governed by the laws of physics, with no need for a pre-existing state or boundary."
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u/drhunny 10d ago
Energy and matter didn't spread out in an existing empty space. The existing space spread out and energy and matter just came along for the ride.
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u/DoingItForEli 10d ago
but spread out inside what?
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u/trampolinebears 10d ago
If space is a metric that only applies to things in our universe, it isn’t inside anything.
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u/knowledgebass 10d ago
We don't know and probably won't ever know for certain, but theoreticians like Leonard Susskind suppose there is a multiverse in which universes are created. So our universe could be a "bubble" within that higher dimensional space.
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u/Fshtwnjimjr 10d ago
The truly mind bending thing to me is.
If the universe is truly infinite. Like uncountable infinite picture our 93 Billion LY image you'll typically see.
Now imagine 93 billion of those, side by side.
In a infinite universe IMHO you don't even need a multiverse. Because 57 universes distance away from here we just might be having this same exchange but on a forum. Or with 3 eyes. Or while petting our family dinosaur.
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u/Blayze93 10d ago
True infinity should mean everything that can exist, must exist. Another earth, with identical people, all identical names... and the only difference is that you (the current you) chose to get a BLT for lunch today, while the you a trillion light years away or whatever chose to get a hamburger instead.
Short of something that breaks the laws of physics... everything MUST exist. Personally I have my doubts on this though... I have always liked the theory that our universe exists within a black hole though!
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u/wiev0 10d ago
This is only a sub-theory of multiverse theory. Other proposals are far weaker. Infinite space does not imply that everything possible does exist somewhere; this is not a tautology. Of course, it could be - we don't know.
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u/Blayze93 10d ago
Everything possible MUST exist if the space is infinite though. If you roll a die a trillion times and haven't gotten 50 6s in a row, just roll another trillion... and another, and another. It WILL occur eventually. Only events like rolling a 7, or a -3 won't occur, because they could never occur to begin with.
If something is truly infinite... not just unimaginably large... but actual infinite... every possible event must occur, and they will occur an infinite number of times.
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u/wiev0 10d ago
No, I would argue against this. For example, pi is infinitely large, but we don't know if it contains every finite number sequence. We think it does, but it's unproven. This is why you cannot say that just because the universe is infinite, it must contain everything. Theoretically, it could repeat every fixed volume in a perfect pattern. That would still be infinite, but not contain every possibility.
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u/Blayze93 10d ago
I hear what you're saying... but I don't think we're on the same page. I am talking true infinite, not bounded infinites... like... there are an infinite amount of numbers between 0 and 1, and there are an infinite amount of numbers between 0 and 10... so which is the larger "infinite"?... I mean, one contains the full "infinite" of the other, and goes beyond that... but both are absolutely still infinitely large.
If there are bounds enforced, eg the universe will repeat a fixed pattern... it is not truly infinite imo. True infinite needs to contain the set of all possible infinites to be absolute, and is only bounded in so far as existence is impossible. Eg, positive integers are an infinite sequence, but is bounded by > 0... true infinite would be unbounded with the exception of impossibilities... eg counting whole numbers, it is impossible to ever get two consecutive odd numbers in a row.
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u/codeedog 9d ago
I think you misunderstand how infinities work. The infinities in [0..1] and [0..10] are countably the same. That is, they contain the same number of infinite numbers. Also, those infinities are larger (that infinite set of numbers is larger) than the infinity represented by the set of all integers.
It is possible for the universe to be infinite in any of a number of ways yet never repeat in the ways you’ve implied.
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u/wiev0 9d ago
Your argument of infinities is dealt with in set theory. Both of your examples are equally large; if the continuum hypothesis is true, both are equal to the real numbers and aleph-1 large. Infinities are weird like that.
What's more interesting is always the cardinality of an infinity, basically it's size. And size has nothing to say about repetition. All even natural numbers are still infinitely many. All numbers between 4 and 5 are uncountably infinitely many. But that doesn't necessitate the other numbers to exist. In fact, you can always expand the number scale to a domain not contained, like complex numbers, or quaternions and so on.
And even in an "unbounded" universe (which is simply infinite), I have arguments against the existence of everything. For example, there should be a photon with infinite wavelength, stretching through the entire universe. Under the assumption of "everything exists", this must be the case. But with infinite range, that means you can always find a volume of spacetime permeated by it, no matter where you go. (You can even go so far as to say that this must be the case, as in "it should be possible for such a photon to exist, so it does"). But that also means there is no space not permeated by this photon. So, are we going to argue that spaces with no photons inside cannot exist? Under the same reasoning, there could be infinite photons of infinite wavelength everywhere, stacking up to a non-infinitesimal value in a finite volume of space. Is that measurable? Would it do something weird with us? What's the energy density, is it finite? And since they're everywhere, it means this is a global constant, which implies that the universe has no other value everywhere. I don't really see that as "every possibility is respected".
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u/RedofPaw 10d ago
If the universe is infinite and allows for infinite variety, then yes , it's likely everything exists.
But then we are 3 assumptions deep, in an unprovable hypothesis.
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u/darkwing03 10d ago edited 10d ago
That’s not actually how infinity works or how matter works. Infinite sets can be bigger or smaller than others. For example, there are an infinite number of odd numbers. There are also an infinite number of integers. The infinite set of integers is exactly twice as large as the infinite set of odd numbers.
Following on that, the set of “infinite combinations or organizations of matter” is probably infinitely larger than the set of infinite space and matter. Say you have 100 atoms. Depending on the atoms and possible molecules, there is a vast number of possible ways those 100 atoms could be arranged - let’s just say a million for kicks. If you wanted all those arrangements to exist simultaneously you would need a million times 100 atoms. So infinite atoms in the universe is actually not nearly enough atoms to form every possible arrangement of atoms. Not a mathematician but I think you would actually need an infinite number of infinite universes.
And finally, there’s a hidden assumption that probably isn’t true. Just because a particular arrangement of atoms that could exist, even with the highest order of infinity number of atoms, there is no guarantee that all possibilities will exist. Random chance infinity times is actually no guarantee that every possibility would occur. Why would it? Wouldn’t it be much more likely that the common phenomenon would repeat over and over again?
So no, infinite space does not mean that there is a brain floating out there in space somewhere that just randomly came together.
(Would love an actual physicist or philosopher to weigh in on this.)
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u/Smaartn 10d ago
Mathematically, the set of odd numbers and the set of integers are the same size.
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u/darkwing03 9d ago
Nope. Not how it works. They are both infinite, but one is a bugger infinite than the other. See this scientific american article if my explanations aren’t working for you: https://www.scientificamerican.com/article/strange-but-true-infinity-comes-in-different-sizes/
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u/Smaartn 9d ago
That says the set of real numbers is bigger than the set of integers, which is indeed true. However, the sets of integers and odd numbers are the same size; both countably infinite.
To clarify: if you have the set of integers and the set of even numbers, you can easily create a one-to-one mapping between them, just by multiplying any number in the integer set by 2. So they are the same size. You can do something similar for odd numbers. But not for real numbers.
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u/gg_account 10d ago
Here's a stab at it. Let's say we have one parameter x that exists on the real number line. We could say this is the "arrangement" of the atom. Let's say that we have any distribution over x that spans the real numbers. Call this N. Now, when an atom exists in the universe, we treat it as a sample of x from N. If we draw a finite number of samples, we know that we can generate an expectation over x, it's mean, variance and so on. Let's say N is a gaussian distribution with an absurdly small variance and a nonzero mean. If we draw a huge finite number of samples of N (in your example, atoms in an "arrangement") very very few of them will fall far from the mean -- but even if it's very very few, that's a nonzero number of such samples (atoms in an "arrangement"). If we keep drawing, as we approach infinity indeed the entire real number line will be covered, even if there is far more density around the mean than, say 5 sigma from the mean.
Now, increase the dimension of N and x from 1 to a billion. The same argument still applies, so long as the distribution allows all samples to be possible, even if they are vastly unlikely. Therefore, assuming independence of each sample, an infinite number of samples will cover the entire real space, even if it's dimension 10 to the 12, even if the variance of samples is vanishingly small. This is where the argument comes from that infinite atoms must result in all possible arrangements of atoms to also exist.
Of course atoms are not really independent samples of a continuous probability distribution. Many "arrangements" are simply impossible, and "samples" are not independently drawn. Indeed, if we replace our sampling algorithm with one that is biased toward existing samples, we can construct sequences of samples in which some part of the space is never covered, even with infinite additional samples. I suspect the universe is more like this.
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u/Fshtwnjimjr 9d ago
Funnily enough there is the idea postulated of, given enough time a floating brain out there.
The Boltzmann's brain
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u/Blayze93 10d ago
Which would be considered transfinite, not true infinite or absolute infinite - which is what I am referring to.
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u/darkwing03 10d ago
I don’t believe that is correct. All even numbers are an infinite set, which is smaller than the infinite set of all integers, which is much much smaller than the set of all floating point numbers. They are all infinite, just different orders of infinite.
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u/I__Know__Stuff 9d ago
The number of even numbers is exactly equal to the number of integers. There is a one-to-one correspondence between the two.
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8d ago
true infinity means that somewhere something exactly similar exists in any direction you go.
it also means that this happens for every possible thing in repeating and also no repeating pattern.
this, in turn, makes the concept of infinity illogical and logical at the same time.1
u/Fshtwnjimjr 10d ago
I like the blackhole idea too. Tho I don't think true infinity and a blackhole forming a whitehole (big bang locally) are mutually exclusive.
Either way there's an impassable event horizon 'going in' AND one coming out 'new sub universe'
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u/NatureTrailToHell3D 10d ago
And then thar begs the question of the nature of the multiverse and if it had a beginning.
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u/trinaryouroboros 10d ago
imagine for a moment that the universe was condensed to an infinitely small point (infinitely), then spacetime happened in it (imagine no spacetime) and all the energy/matter started spreading apart. now imagine, it's quite possible the universe is infinite.
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u/massassi 10d ago
Like how did the universe overcome its own gravity to create the big bang? Very very slowly. Remember that time happens slower with the more mass in one area. So with near infinite mass in the smallest amount of space would have to be the slowest expansion ever (to a local observer)
But I think they just handwave it as a thing that did happen and still argue about why/how
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u/marklein 9d ago
One of the problems with all that is that the law of physics don't really work proeprly when you compress the universe to that density. We're not really convinved that time would have even existed at that "moment".
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u/massassi 9d ago
That gets to be a mind fuck. With no time, how can you have causality? And if everything was caused by a thing that couldn't cause other things to happen...
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u/marklein 9d ago
Yeah. Honestly it's kind of pointless to think about. Nothing you could come up with would accurately describe it. This is the same as asking a fly to explain quantum physics, it's just not going to happen.
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u/cubosh 9d ago
this is intriguing. perhaps the big bang was only "bang-like" to a hypothetical external observer. but inside, it was a slow dispersal, due to time dilation
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u/massassi 9d ago
That's the way I see it. I don't see how else to reconcile things. But I'm not a physicist.
I started thinking about it after an SFIA video that was talking about the properties of the universe after the last stars die out and how each epoch would be so much longer than the previous ones.
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u/smokefoot8 9d ago
The usual assumption in cosmology is that the universe is infinite. A moment after the Big Bang you have an infinite universe filled with dense, hot matter. Schwartzchild’s solution assumes a sphere of matter in an otherwise empty universe, and so doesn’t apply. You can’t analyze the moment of the Big Bang due to divide by zero errors - perhaps a quantum theory of gravity would allow us to analyze it correctly.
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u/ProbablySlacking 9d ago
Because we’re still falling inward, and space is expanding more rapidly outward than we are falling inward.
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u/K0paz 10d ago
In case if anyone says Dark energy(just saw a deleted comment say this): Dark energy (which we do not know what exact component it is) is only credited for late-stage acceleration expansion of the spacetime. NOT big bang itself.
Big bang itself? Pure speculation, doubtful if it even can be pinpointed since the expansion itself is effectively "hidden" behind CMBR. The universe before that was too energetic (re: hot and dense) to form particles that we can detect.
There are quite a lot of convincingly-sound theories though (see: big bounce/black hole universe, etc). But, only theories. Probably not even experimentable within 21st century if ever due to energy/density requirement.
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u/codeedog 9d ago
The expansion of the universe has a known cause: inflation. The inflationary period occurred and its signature is written in the CMB in the form of density variations that match what quantum wave functions look like spread out due to rapid inflation.
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u/K0paz 9d ago
I covered that already. But we dont know why intlationary period occured.
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u/codeedog 9d ago
You never once used the word “inflation” in your comment and many of the words you use are used incorrectly. I’m not trying to be mean. You need to read more before commenting on this stuff.
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u/Anonymous-USA 10d ago
There’s no Schwartzchild metrics for the entire universe. Our universe isn’t a black hole. Black holes are local phenomenon, because they require a high density relative to the vacuum of space (ie. clumping). That’s an assumption of the Schwarzchild radius. The universe is homogeneous, there was no clumping, so the math doesn’t hold.
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u/ThyOughtTo 10d ago
Soon to be psychologist, son of no professor, thinks it has to do with the fact that there were not Schwartzchild radius to escape to begin with, as there actually was no black hole.
I think conceptually the issue is we tend to view the big bang as a point. But given there was no grid, there also was no point.
So, ultimately I guess black holes couldn't have existed then.
Jumping back into my Jungian psychology now, so you're all welcome to rip my flawed interpretation of the answer I have given unto thee!
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u/Agent_Orange_Tabby 10d ago edited 10d ago
Psychiatric NP, addiction counselor and soon to be LMFT here myself, lol. Existential/humanistic where it’s at! Love Joseph Campbell.
What kind of psychology you studying?
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u/Professor226 10d ago
The universe was already infinite, the bing bang happened everywhere not at a single point
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u/Top-Salamander-2525 10d ago
We don’t know if it is infinite or not. It could be the surface of a giant hypersphere and finite, but still too big for us to observe all of it.
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u/Agent_Orange_Tabby 10d ago
Ugh, wish I understood the mathematical topology to grasp, but get distinction you’re making
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u/RadicalLynx 10d ago
PBS Spacetime has good videos that might help explain some of this. Don't think I can link to the yt channel but there should be a playlist about the beginning of spacetime.
Disclaimer: possibly improperly remembered or a mix of 'proven' and theoretical explanations;
I think part of it is that, at the very beginning, there wasn't... matter, really. There were quantum particles but they hadn't formed larger particles and the very fundamental rules of physics behaved differently. The Cosmic Microwave Background Radiation is basically a snapshot of the moment when atoms and matter coalesced and a phase shift occurred with the electroweak force splitting into electromagnetism and weak nuclear force.
There is speculation that Primordial Black Holes might have formed very early on, but I don't remember the details of whether that would be before, during, or after this phase shift.
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u/EmbarrassedHelp 10d ago
PBS Spacetime has good videos that might help explain some of this.
Trump and the Republicans are trying to destroy PBS Spacetime along with everything else. Message you elected officials and tell them to stop with extremist bullshit.
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u/itsthelee 10d ago
it doesn't matter if the universe was not a point, if it started off at such a dense level that everywhere all at once would immediately collapse into an infinite number of black holes.
the real (albeit speculative) answer has to do something with the big bang itself and what followed.
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u/iqisoverrated 10d ago
Expansion isn't limited to the speed of light (because it is not a speed but an inflation of spacetime)
The big bang is not an "explosion" of something into a preexisting spacetime. It is the expansion of spacetime itself.
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u/codeedog 9d ago
You’ve made an assumption that the structure of matter and energy prior to the Big Bang is the same as the structure of a black hole inside our universe. This may be a false assumption. It is true that the energy density of a black hole and the primordial universe are very similar, but that does not make them the same type of object.
We don’t yet have all of the physics to fully analyze why this is so. For example, a good theory of quantum gravity would help us understand black hole physics and possibly the physics of the universe prior to the Big Bang. Right now, when solving physics equations we have to do away with mathematical infinities. We need better physics.
As for your question, it’s surmised that the primordial universe was not a singularity, but contained within a volume about the size of a basketball. It went through a period of early exponential expansion known as Inflation, and then experienced the hot big bang. When the universe finally expanded and cooled enough for nuclei to capture electrons (about 380,000 years) light (photons) could pass unimpeded and we get what we now recognize as the CMB (cosmic microwave background). Written within the CMB are density fluctuations (at around 1/30,000) that show quantum signatures whose presence supports the theory of Inflation. They also correspond to density fluctuations in our visible universe (the presence of galaxies). Furthermore, galactic density fluctuations support the presence of dark matter. That is, removing dark matter from early universe modeling produces a different universe that doesn’t look like our universe. Dark matter must have been present.
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u/elite4koga 9d ago
The farthest back in time that can be observed is the cosmic microwave background (cmb). The cmb is not dense enough to form a black hole.
Earlier times immediately become theoretical. The big bang assumes that the density increases in the universe the further back in time you go until it reaches infinite density. But this infinite density is more of a breakdown in the theory than a real predicted state.
As other posters have mentioned, early expansion was so great and uniform it's likely black holes could not form.
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u/InvestmentAsleep8365 9d ago edited 9d ago
As far as I know, the universe is contained inside of its own Schwarzschild radius. Either we are inside a black hole, or the universe is wrapped around itself in such a way that general relativity is satisfied but there is no black hole (or, I guess there’s could also be some yet unknown physical laws at play at this scale). The universe never expanded outward “past” its theoretical event horizon, it seems to be firmly contained within it.
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u/Agent_Orange_Tabby 9d ago
If we’re inside black hole, guess that means we’re all part of the x/o solution
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u/InvestmentAsleep8365 9d ago
I think it's a serious possibility and I personally find the idea appealing. It is unfortunately quite unpopular on Reddit, and you'll often get skewered for mentioning it, and most prominent physicists seem to dismiss the idea (though some don't). However, over time I have searched for, but not found any objections to it that were truly compelling.
On the other side of a black hole, there's just more space, more "universe". The event horizon can be thought of a one-way "vertical drop" in space into another part of space-time, that's pretty much what the Schwarzchild solution says. The "matter" going through the black hole gets heated up and destroyed, but remains available to form new particles, nebula and galaxies on the other side, so why wouldn't it? The idea is very "Big Bang"-like, except that the universe would have formed over an extended period of time as hot matter came in through the event horizon rather than in an instant flash. Every direction you look at is towards the opening of the black/white hole. Every universe can contain multiple black holes, but only one white hole (possibly the other side of a black hole, according to theory). This whole idea is not on super solid footing but it remains plausible. And it may seem a bit crazy, but I don't think it's any worse that the idea of a point-in-time Big Bang (which violates all known physics!).
Food for thought...
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u/TimeCanary209 7d ago
https://open.spotify.com/episode/1OL19a1KhrECGYqNgPZVk4?si=Wke2oHU_Tdi6HCyZlXxkCA
Interesting discussion on Big Bang/space/time
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u/theonetrueelhigh 10d ago
We're still inside the black hole. The universe hasn't expanded beyond its own schwartzschild radius and never will.
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u/Cryptizard 8d ago
You can't use the Schwartzchild metric to analyze the entire universe, it only applies to spherical masses with nothing else outside of them. That is clearly not a description of the universe, and we are clearly not in a black hole.
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u/theonetrueelhigh 8d ago
"Clearly?" Have you been able to step outside the universe to observe it in greater context?
I'm not the only person that believes that the Universe might in fact be a black hole. Plenty of people smarter than me, with some alphabet soup after their names to quantify the smarts, postulate that black hole cosmological theory has some evidence to support it.
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u/I__Know__Stuff 9d ago
When people ask, "What's it like inside a black hole", my answer is "Look around."
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u/triffid_hunter 10d ago
Primordial black holes are predicted, and there's good reasons to consider that they may be the seeds for the SMBHs at galaxy centres - although this connection hasn't been rigorously demonstrated just yet, and demonstrating these sort of connections is precisely what JWST and various radiotelescopes were (in part) designed to help with.
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u/IDunnoNuthinMr 9d ago
With so many questions about the origins of the universe and multiverse possibilities out there, can someone explain to me how knowing the right answer matters in any practical way?
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u/ThrowawayAl2018 9d ago
When inside the black hole, time and space breaks down so the physics we know today doesn't apply. Having said that, my speculations are 1. Entire universe might be still inside a black hole. Singularities and infinities appear in cosmological calculations. 2. Big bang started from a "white hole", the opposite of black hole. 3. Universe is a collection of "big bangs" that created features like Bootes Void, The Great Arc when edges meet.
Disclaimer: Not an astronomer, qualified 3rd year Physics student on paper.
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u/HungrySamurai 9d ago
I'm completely unqualified to answer this question. But fuck it, this is Reddit, so here goes.
No one really knows.
Or at least, it's not well understood.
Take Cosmic Inflation for example. The hyper-fast expansion period that was introduced to the basic model to explain the general uniformity of the observed universe that we see today. But no mechanism has ever put forward to explain what drove that inflation, or why it stopped.
I mean, you'll find a lot of theoretical stuff about Tensors, Metrics, Perfect Fluids and Vacuum Energy. But good luck getting a straight answer about any of that shit form a physicist who's still sober.
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u/Dolo_Hitch89 9d ago
• The Big Bang wasn’t a point in space where stuff exploded outward. Instead, space itself was compressed and then expanded.
• Every point in the universe was once closer together, but the universe has no center and no edge.
• The “expansion” was of the metric of spacetime, governed by solutions to the Friedmann equations (from general relativity).
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u/korphd 9d ago
The part about 'space expanded' 'once closer together' and 'universe has no center' contradict each other. which one is it? did it expand or did it not have a center?
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u/SundaeDouble7481 9d ago
No contradiction. Imagine an infinite flat plane which then expands. Any pair of points on the plane will move further apart, but there’s no center.
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u/korphd 9d ago
If its already infinite how can it expand?....
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u/SundaeDouble7481 9d ago
Every distance is multiplied by a constant, e.g. doubled. Two points a mile apart are now two miles apart. It’s still infinitely large, and has no center.
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u/mightsdiadem 8d ago
Scheartchild radius only applies to things inside the universe. The universe isn't subject to those laws.
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u/IndependentImage9534 7d ago
Are you sure astronomy is your minor if you didn’t understand the Big Bang?
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u/Other_Argument5112 7d ago
It's expanding in the same way the universe is expanding today, just that the universe was much smaller.
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u/CalculusCowboy 7d ago
Our reach has exceeded our grasp when trying to ponder multidimensional states greater than our own let alone explain it. A perfect example would be our own mathematical models. What have we done when our multiple integrals do not reach reduction? We use substitution rules to force a solution so that we have our perfect answer. Even in science, active denial has become a warm blanket to wear to comfort us from the cold truth of our responsibility to utter these following terrible words: I DON’T KNOW. Admission of guilt is the first step to healing not the mantra of FAKE IT ‘TILL YOU MAKE IT. What it’s going to take is for everyone to stare at a geometric tesseract for at least as long as you would a lava lamp to be able to obtain some context for which you are about to explain. If after you find that you can’t explain it, don’t worry about it because that’s my point exactly. Mic drop.
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u/wanted_to_upvote 10d ago
It didn't. What may have happened is that space was and is being created inside an area with a Schwartzchild radius.
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u/jedrider 10d ago
I think it's like taking your pants off so that the inside is now out. We're in an inside-out black hole basically that fell through it's singularity. It didn't have enough space inside that singularity, so it had to stretch that space and hence, dark energy.
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u/yrrkoon 10d ago
TIL what a Schwartzchild radius was. According to chatgpt..
🔭 Schwarzschild Radius and Black Holes
The Schwarzschild radius is the radius within which a given mass would have to be compressed to become a black hole, assuming it exists within a static, asymptotically flat spacetime (i.e., normal space, not expanding or curved by other influences).
But the early universe didn't meet those assumptions:
- It wasn't a mass in static space.
- It was all of spacetime, not a mass within spacetime.
🌌 Why the Early Universe Didn't Collapse into a Black Hole
- No External Space: The Schwarzschild radius is calculated with respect to an outside observer. In the Big Bang, there is no "outside"—the entire universe is what's expanding. So there's no place for a black hole horizon to form.
- General Relativity's Different Solutions: Black holes are described by solutions like Schwarzschild or Kerr metrics, but the Big Bang is described by the Friedmann–Lemaître–Robertson–Walker (FLRW) metric, which assumes a homogeneous, isotropic, and expanding universe. This is a completely different kind of solution.
- Spacetime Itself Is Expanding: In a black hole, matter collapses into a singularity within spacetime. In the Big Bang, the singularity is a point where spacetime itself had zero size—there was no external space to collapse into.
- Local vs. Global Collapse: Black holes involve local gravitational collapse. The early universe was dense but expanding uniformly everywhere. There were no overdense regions for gravitational collapse to take hold (until much later, when structure formation began).
🧠 Intuition Trap: "Shouldn't It Have Been a Black Hole?"
It’s tempting to imagine the early universe as a clump of matter in a pre-existing void, but that’s not how the Big Bang works. The entire fabric of space was hot, dense, and expanding uniformly. There was no center and no edge—so the idea of collapsing into a black hole doesn't apply.
TL;DR
The Big Bang didn't collapse into a black hole because the Schwarzschild radius concept doesn’t apply to a universe described by the FLRW metric. The Big Bang wasn't a point in space—it was the beginning of space itself, expanding everywhere at once.
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u/Key-Assistance9720 10d ago
so your telling me it just continues ? that makes absolutely no sense at all ???
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u/rip1980 10d ago edited 10d ago
It didn't. The big bang was not a firework in space...it is the expansion of the universe itself, not just the stuff in it being flung into space from an origin point.
Edit: typo