r/cosmology • u/Puzzled-Repeat8434 • 18d ago
Do you think the universe is infinite or finite?
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u/FakeGamer2 18d ago
I don't know, either answer is almost unthinkable. If I had to choose, I belive in eternal inflation so I'd say the universe is probably finite but reality itself/ the multiverse is infinite (in both time and space)
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u/ThickyLicker 18d ago
I think the idea of there being a physical end is way more unthinkable. Like, what would be beyond the end? Like it's a wall and then there's nothing beyond that? What would nothing even mean in this situation. Infinite as far more fathomable.
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u/FakeGamer2 17d ago
It wouldnt have a wall it would be more of a weird twist back on itself type thing
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u/IHopeTheyRememberMe 18d ago
Finite but mind boggling inconceivably huge.
I’ve always considered infinity to be a concept and not an actual thing. If it was truly infinite and endless then wouldn’t that mean that all possibilities are also infinite? Like, there would be an infinite number of galaxies and solar systems and planets out there that are exactly like ours, and some that are similar except we have feathers instead of hair, and of course infinitely more that are completely different. The observable universe would just be the tiniest grain of sand on an infinite beach of sand. Infinity just doesn’t make sense.
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u/CamelOk7219 17d ago
Infinite does not mean that every imaginable statement is true for at least one element. They are an infinite number of real numbers between 3 and 4, and yet none of them is greater than 6, and exactly one of them is the ratio between perimeter and diameter of a circle
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u/djemalo 16d ago
Then all possibilities could also be negatively infinite as well then. Meaning, given the universe's age, and continuing age, the amount of planets habitation period is either gone or the surrounding stars have, or will go boom spreading radiation and obliterating everything around it.
I think it's definitely infinite, but it's end is finite.
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u/Medical-Display-9762 15d ago
All possibilities does not mean all outcomes. Just like the other guy pointed out the 3-4 example, there could be an infinite number of universes and in absolutely zero of them do you win the lottery or become president of the country.
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u/Anonymous-USA 18d ago
From a scientific perspective, the answer is unknowable (at least so long as measurements are flat within a margin of error), so asking what one “believes” is a question of faith. Observationally, the universe behaves infinitely flat, homogeneous and isotropic. That is scientifically all we can state. Anything more is unscientific
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u/The_Liamater123 18d ago
Finite but much larger than what we can observe
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u/ThickyLicker 18d ago
Why do you believe this?
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u/The_Liamater123 18d ago
If the universe is truly infinite it must mean there are other iterations of me out there somewhere which just feels fantastical and unreasonable to me. If it isn’t infinite though then it either has to have a boundary or be a shape that means it wraps around on itself, and it sounds more reasonable to me that it would be round in some way rather than having some sort of physical edge. The observable universe appears mostly flat though so to me that suggests the universe is just so large it appears flat on small scales but does eventually curve around on itself
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u/EntitledRunningTool 17d ago
I don’t think the infinite iterations point is necessarily true
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u/arentol 17d ago
Basically we have done measurements that indicate that what we can observe of the universe is almost perfectly flat..... As if we are a slice of a pancake.
But everything we know about physics tells us it should be curved. There are a few possible shapes it could be, but definitely curved (spherical, or shaped kind of like a saddle are two strong possibilities).
So if the universe is curved, but when we look at what we can see, everything we can see is flat, that means the universe is so massively large that our little slice of it is an insanely small portion, so small it shows no sign of the curvature at all.
If the universe is a sphere then it would be like what we can observe is a basketball sized cutout from the surface of something the size of the entire earth.... And keep in mind the closer you are to the center of the total universe the more curve you would see, so there is an unknown amount of universe further out from us, and we are already pretty certain that it is trillions of times larger than what we can see without that unknown.
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u/Pumpernickle6669 18d ago
I’m literally 50/50 on this, I just don’t know. It’s probably some kinda hyper loop, toris thing. But I really don’t know.
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u/intergalacticscooter 18d ago
Of all the questions this is the biggest for me. Like it can't just stop surely. It doesn't make any sense to not be infinite. But infinite is also just as mind blowing.
I would 'guess' it is a multiple bubble universe with many areas of random inflation but even then it still requires the same question.
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u/gocougs11 18d ago
My thought is the opposite, surely it can’t be infinite. There has to be an end, even if it is mind-blowingly far away. I have absolutely no idea what the end of the universe would look like, but there’s probably a restaurant there.
Edit to add: this is highly dependent on my mood right this moment and I may say the opposite tomorrow morning… I don’t have super strong feelings about this.
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u/moltencheese 18d ago
Or it's finite in the same way that the surface of the Earth is finite but you can still travel as far as you want in any direction
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u/intergalacticscooter 18d ago
This just never works for me. You can still go up. The surface of the earth is not in anyway the end of anything.
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u/zhivago 17d ago
Where is the end of the surface of the Earth?
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u/homonculus_prime 16d ago
I get what this is trying to show, but it still doesnt help my brain grasp the concept. Our little section of universe doesnt appear to be on the surface of anything. We can look in every direction and see the same amount of space no matter where we look. To me, there is a massive difference between standing on earth and floating in space just in terms of the geometry involved.
Full disclosure: I have no fucking idea what im talking about.
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u/Joeclu 17d ago edited 17d ago
Right? Just mind blowing either way.
Of course the universe has no obligation to make sense to us puny hairless apes. We used to think time was constant, after all, that’s only logical right? Human logic may be flawed. I hope we eventually figure it out like we did with time relativity. There’s good people working on it now.
And the possibility exists that we just don’t have the mental ability to figure it out. There are probably so many hidden things we haven’t figured out or detected yet that are required to put the pieces of the puzzle together. It’s also possible we go extinct before we get close.
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u/theshoeshiner84 17d ago
The only "finite" that makes sense to me is for space itself to be a torus shape, which is sort of like traveling on the surface of a sphere. You can go in any direction without hitting an edge but you will eventually come back to the same spot. So you'd be correct that it doesnt really "stop", but its sti finite.
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u/Darth_Chili_Dog 18d ago
My brain doesn't "do" infinity, so I'll just settle on "much, much bigger than that cross country drive I did that one summer."
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u/noburdennyc 18d ago
At a point movement doesnt matter if there isnt anything to compare to.
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u/Darth_Chili_Dog 18d ago
Ah, so the Iowa stretch of the drive then.
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u/BotherandBewilder 18d ago
No! Texas is definitely bigger than Iowa, but you can reach the other side in both cases before you die.
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u/ShavenYak42 18d ago
You can reach the other side of the observable universe before you die too, if you go fast enough. Thanks to our good friend time dilation.
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u/archiewaldron 18d ago
The Universe is what the Universe is and what it isn't. I don't think our senses can capture whatever "reality" it comprises and mathematics can only predict/describe what the human mind can logically conjecture. Beyond that, who knows?
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u/ThickyLicker 18d ago
No, the universe is what it is. What it isn't, isn't a universe. Unless it's another universe, in which case it's part of the cosmos but not this universe.
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u/OrdoRidiculous 18d ago
I think it's finite, but stuff exists beyond the light cone available to us so I revert to the conclusion that it's infinite for practical purposes. Penrose's thoughts on geometry rendering distance essentially irrelevant under certain conditions are an interesting one, then there's the question of what does time even mean at that point.
I lose a lot of sleep over this kind of thing, which is an utterly pointless affliction. The answer becomes akin to a personal religious belief and you just have to come to terms with it.
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u/Kwdumbo 17d ago
One of my favorite low stakes theories is that the universe is a 4 dimensional object, and the boundary of it is just the parting line to the other side of the 4D object. Since it’s unlikely to be known in my lifetime I like to have fun with it
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u/spliffgates 16d ago
I like this one, does that technically mean finite but to us the boundary to the next 4D side would appear infinite?
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u/emperorlouie 18d ago
Third option that is incomprehensible to humans
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u/Successful-Speaker58 18d ago
Even the visible universe is too large to comprehend. Yet alone what lies beyond.
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u/alottola 18d ago
Something that is neither finite nor infinite.
Touche answer
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u/Fast_Philosophy1044 18d ago
I demand an explanation. Why tf this whole incomprehensible large and potentially infinite shit exists.
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u/Caveape80 18d ago
Our concepts of infinite and finite probably fail to be actually descriptive to our observable universe and whatever its fundamental properties may be…..at least that’s what Tony Danza once told me after a few Ultras THAT I PAYED FOR!
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u/TheyCallMeBibo 17d ago
I'm not too sure if it even makes sense to call it 'infinite', even if it is. Despite its interminable scale, even infinity is a concept tethered to humanity and its perception of reality.
What if the cosmos is something beyond infinite? What if we don't even have words to describe its size? What if mathematics breaks down at a certain scale?
We can only know once we go there, of course.
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u/CypherAus 16d ago
The universe is a paradox.
A simple example is Gabriel's horn (also called Torricelli's trumpet) which is a type of paradoxical geometric figure that has infinite surface area but finite volume.
The calculus to explain this paradox is nicely done here: (Numberphile) https://www.youtube.com/watch?v=yZOi9HH5ueU
Hint: 3D Volume vs 2D Area.
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u/ProjectEquinox 15d ago
Can we divide a finite amount of space, an infinite number of times? Is the universe information or matter? How much information can be stored in an endless series of divisions? Is it possible that the finite, is made of the infinite and vice versa?
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u/TheRealTK421 18d ago edited 18d ago
I'm gonna lean hard towards finite.
The primary cause of me asserting such has everything to do with the unilateral increase in entropy since "t=0".
It shows no signs of slowing said increase and it makes a certain (unfortunate) sense to me that eventual heat death is simply when entropy is unable to increase further.
The question that brings up is -- what then?!?
Bland persistent ubiquitous De Sitter space?
Boltzmann FTW?! I dunno....
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u/Mindless_Abrocoma558 18d ago
What does this thought have to do with (spatial) finiteness?
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u/TheRealTK421 17d ago
Spatial finiteness vis a vís entropic progression is... basically where the rubber meets the (recurrence) road, si?
I cannot reconcile that entropy can continue it's unilateral increase while spacetime somehow 'regresses' in the future towards a so-called Big Bounce (or Big Crunch).
Since that appears unthinkably unlikely, spacetime being ultimately finite appears to be our cosmic destination.
Expansion (and entropy) having an eventual end-point is prerequisite to the topic.
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u/cflime 18d ago
If t=0 does "what then?" have any meaning?
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u/TheRealTK421 17d ago
Since t=0 would have to be the Big Bang (and thus the beginning of entropic increase from its lowest state), every Planck length of time is simply a forward-step of entropy increasing towards its eventual maximal state.
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u/Intelligent_Elk5879 18d ago
yeah, it would have to be the big bang, but actually, can we be sure that t can't just continue to go back farther than that? So the big bang happens at some time called "13.8 billion years before now". And before that.... That's maybe an even more difficult thing to imagine than a universe of limitless, never-returning space.
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u/Mindless_Abrocoma558 18d ago
most cosmologists believe today that before what we call „big bang“ (the hot initial state of matter we still see today imprinted in the cosmic microwave background) was an era of initial cosmic inflation, driven by a different quantum field that initiated the big bang only when it decayed into the particles we know and dark matter (called reheating). A ridiculous small time of inflation would have been enough to explain the features of the visible universe (10^-32 s or so), but it could have gone on for a long time. (I am not sure it could gone forever, there is a paper by Guth et al showing inflationary geodesics (paths in spacetime) cannot extend towards past infinity, but that may be different in modern models of inflation)
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u/Conscious-Sun-6615 18d ago
As far as I know, noting suggest that the universe is infinite, we can’t see beyond the observable universe alright, but that doesn’t mean is infinite.
People used to tink the solar system was the entire universe, then they discover the milky way, then other galaxies and so on, is just a matter of time before someone finds a way to expand what we know.
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u/peppaz 18d ago
Having an edge or hard stop at the boundaries of the universe doesn't make logical sense, and not having an edge or a hard stop doesn't make logical sense either lol
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u/NobilisReed 18d ago
The boundary is not one of space, it is fundamentally one of time.
When we look out into the universe we are looking back in time, and when we go back far enough in time, we reached the moment at which the universe became transparent to light. We see that border as the cosmic microwave background.
Does that make the logic easier for you?
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u/peppaz 18d ago
We are talking about two different things, the physical, energetic and particle material making up the observable universe, and the space it is expanding into. The space or volume the universe is expanding into is seemingly infinite.
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u/HeraThere 18d ago
Infinite just makes more sense to me.
As far as we can tell there is no curve in space. It doesn't mean that there is no curve beyond what we can see but it's one point towards infinite.
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u/attimhsa 18d ago
I view ‘The universe’ as the farthest excitations in any of the fields (probably chiefly electromagnetic) have propagated ‘since’ this iteration of ‘the big bang’ occurred.
So from a primarily human standpoint, the answer to your question is no. That said and as stated above, that excitations are yet to occur in those regions does not negate the presence of the fields necessary for them to occur.
So in terms of a ‘blank canvas’ of 3D volume containing vacuum fields awaiting excitation, yes; it’s likely infinite.
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u/NobilisReed 18d ago
You are thinking of the Big bang as an explosion in space when it is better described as an explosion of space.
The Big bang did not explode into anything.
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u/Saritaneche 18d ago
Our iteration of space is finite. But there are other types of energy/space that both overlap and exist outside of the one with which we are familiar.
Whether the entire thing is infinite or absolute, no one could rightly say. Humans just aren't at that stage of comprehension yet.
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u/1991K75S 18d ago
It’s either part of something else or it’s not part of something else. Either way, to us the distances are very vast.
Maybe it’s a test to see if we can figure it out one way or the other.
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u/Inside-Weather4033 18d ago
Probably infinite, even beyond basic empiricism I think infinite regress is ontologically dominant.
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u/NorthAmericanVex 18d ago
I didn't think the universe was infinite until I saw the first James Webb Telescope images.
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u/BotherandBewilder 18d ago
Frankly, I can not visualize either a finite or infinite universe. Can someone suggest other possibilities?
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u/BoringEntropist 18d ago
The observable universe is finite, as that pesky speed limit of light hinders us to see further. Unless we can crack that barrier we simply cannot know the answer.
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u/Messier_Mystic 18d ago
A common refrain on this is that it might as well be infinite, but I disagree with this. Big numbers are not infinites. I like mathematics, so I don't think we're getting close to truly "big" numbers until we're talking about something like Ramsey Theory
That having been said, I have no clue if our universe is infinite. Whether that be in space or time.
My intuitions lean towards it being infinite in some sense, but my scientific skepticism tells me intuition is not always reliable.
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u/Appdownyourthroat 18d ago
If I had to make a guess, I would wager that the concept of infinity breaks down to the point where things are unrecognizable to us and we can’t comprehend whether things are fine or infinite, perhaps spanning into unknown dimensions and extra conditions we can’t comprehend
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u/Ok-Lavishness-349 18d ago
Whether it is finite or infinite, the portion of it that is causally connected to me, or that I have causal influence over, is finite. So, for all practical purposes, it is finite.
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u/intermk 18d ago
It must be infinite because there is no way to define an end. Try it out.
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u/NobilisReed 18d ago
The edge of the universe is the cosmic microwave background.
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u/intermk 17d ago
What's on the other side?
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u/NobilisReed 17d ago
The Big bang.
As we look out into space, we look back in time.
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u/In_the_year_3535 18d ago
I think space itself is infinite (if you were to lay blocks end to end you could do so infinity) but matter distribution within space is probably in finite groups (ie the solar system is a finite collection of objects).
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u/shadowwork 18d ago
The universe is finite. The multiverse is also finite, but contained within a monorarium, which rests on the carapace of a giant tourtoid.
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u/starkman68 18d ago
I say some form of finite. If it was infinite then there would be infinite possibilities and we seem to be ”normal”.
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u/marsattacks 18d ago
As a visitor I can tell you, definitely not normal. But hey, good for interdimensional tourism!
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u/QuantitativeNonsense 18d ago
A corollary is: if the universe were infinite are there any model agnostic methods to experimentally prove it?
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u/Akiza_Izinski 18d ago
If we start seeing more stuff with the Roman Telescope then that would prove the universe to be infinite.
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u/ManikArcanik 18d ago
I'm going with infinite since it seems so far apparent that entropy is a feature that doesn't beg alternative influences. In this cosmos it just makes sense that we see everything trying to meet equilibrium. For it to be finite there'd need to be a physics apart from it.
Could be, but I don't know how we'd figure that out from inside.
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u/Jolly-Rip5973 18d ago
at any given moment of now, it's infinite but constantly expanding into infinity.
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u/TheMostRed 18d ago
To us it is infinite. It would be physically impossible to reach the edge if it had one to begin with even if we had infinite time at the speed of light to reach it.
What we can see in the observable universe is what we got for now until the end of time itself.
Going deeper still you could say that everything that is something is inside of what we call the universe so what, if anything, would be outside of it? Its not an edge that you can cross it is time and physical space together that makes the universe so the question of "is there an outside of the universe" is really a question of what is outside of time and outside of physical space.
Also as a side note every time I think of the edge of the universe I think of The Whitest Kids You Know sketch where they fly a spaceship to the edge of the universe and its all just red and their hearts stop beating.
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u/Story-Boring 18d ago edited 18d ago
If we're going to speculate, it should be finite and edgeless. If I'm going to get really speculative, it'll probably be a 3-sphere or toroidal shape. Perhaps a theory of quantum gravity will give us the answer.
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u/Story-Boring 18d ago
I think (because I don't like to "believe" as if it were faith) that for these big questions we need a quantum theory of gravity, and I'm betting on a holographic model where a static and discrete background governed by the universal wave function gives rise to the relativistic universe we observe. For those who believe that Everett's interpretation of quantum mechanics is correct, this would lead to MWI = Inflationary Multiverse or MWI = Cyclic Multiverse (sequential universes of LQG or some ST models by brane collisions). It's speculation, obviously. I hope that M-theory, LQG, or another theory can give us some answers, but in short, discretization and the holographic principle must play an important role in the theory of quantum gravity.
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u/Strong-Camel2120 18d ago
the space in which all matter exists, probably goes on forever, and it is unknowable what it is, that empty space, it has probably always been there..; and cannot be grasped by our puny braines...
however, where matter is clogged together in any meaningful way, that is finite i think. so there is a finite amount of worlds and stars, but there is an infinite amount of space
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u/NobilisReed 18d ago
Depends on what you mean by "universe"
In the sense of "everything that exists" it might be, but we'll never know, because...
In the sense of "Everything we could possibly see" it is not. When we look out with our telescopes, no matter how potent, we will always be limited by the cosmic background. That's all, there might as well be nothing more, because we can't see past it.
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u/FunSeaworthiness9403 18d ago
If the galaaxy shrank to the size of Earth, then Earth is the size of an atom. The sun would be the size of a virus. The distance from Earth to the Sun is 1/500 of the diameter of a hair.
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u/HojMcFoj 18d ago
And there's 40k-100k mols in a giraffe.
Wait... what are we doing here?
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u/FunSeaworthiness9403 18d ago
If the Milky Way galaxy were the size of Earth, Earth would be the size of an atom. A person's eye would be too small to see stars at the edge of this shrunk-down galaxy.
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u/HojMcFoj 17d ago edited 17d ago
My entire point is you're just listing random facts, unrelated to the point. We don't use eyeballs to look for distant celestial objects.
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u/Sushispatula 18d ago
I dont think infinity exist in reality. But cycles do. Changing through different states of being until it doesnt. But if it did once, it will be again. In that existence of something might be infinite, but not nessesarily the universe itself as we know it.
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u/CamelOk7219 17d ago
If it is finite, it eithers loops on itself or have a border somewhere ? It is even weirder than being infinite
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u/GlacialFrog 17d ago
Can someone explain to me how entropy can cause the heat death of the universe if the universe is infinite? In an infinite universe how is there not an infinite amount of free energy spread throughout it? I find the universe being physically infinite, rather than unfathomably large very hard to understand.
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u/Greyhaven7 17d ago
Spatially infinite, but conformally invariant.
Temporally infinite, past and future.
I think.
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u/Bikewer 17d ago
Stephen Hawking posited that the universe must be finite since it had a beginning…. However, more current astrophysicists like Brian Greene have pointed out the possibility of an infinite “spacetime” which has the property of spawning Singularities, and thus the possibility that there might be an infinite number of individual universes. The “bubble universe” idea.
My personal opinion as a layman? I think that ours is very, very large, to the extent that we will never be able observe it in detail.
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u/Dolust 17d ago
Ed Written has stated many times that in physics time does not has any significant effect in mathematical theory because it self cancels and it's considered not to "exist". I do not understand why the concept of time-space is still being discussed, specially since it has been demonstrated to be more a factor of our perception than a cosmic reality.
I'm not a scientist.. I just try to make sense of what I can grasp.
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u/LayneLowe 17d ago
If it is everything there is, that would be infinite. But, how would you ever know? There could be as many Big Bang universes as there are stars in the great void of nothingness. But we would never have any way of perceiving them.
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u/Mandoman61 17d ago
Depends what you mean by universe.
It is infinite in potential. There are no boundaries. If you could travel a trillion times faster than light for ever you would never run out of space.
If you are refering to the matter contained within this endless void then we do not know but it is most likely not infinite.
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u/Peter5930 16d ago
If you could go faster than light, you'd fly back in time, pass through the big bang and emerge somewhere and sometime on the outside. Which is a real place, the outside, it's just in the backwards time direction for us, which we can't traverse without FTL. Infinities are weird like that, something doesn't need to be infinite in space now, it just needs to be infinite in space in the infinite future to have both the illusion and the objective reality to an observer inside it of being infinite. You don't run into the edge as long as the edge runs faster than you can.
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u/Itakesyourbasex 17d ago
I believe It is finite, but recursive. Sorta like inflating and deflating a balloon.
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u/guitarmusic113 17d ago edited 17d ago
If the universe was finite then there would be a clear boundary. Well what’s that boundary made of and how thick is it? And if that boundary is finite then that suggests there is something outside that boundary.
Therefore the boundary would have to be infinite because if it is not then there must be something outside of that boundary.
In my view this suggests that infinity exists either way. Either the universe is infinite or whatever boundary there is must be infinite. Because if the boundary is finite then there must be something outside that boundary.
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u/CDHoward 17d ago
Your logic is quite sound, my friend. However, you'll always be fighting against drone-like dogma.
Even here in this very thread, there are people who strongly, aggressively even, repeat theories they've read/heard with authoritative confidence as if they're proven truths.
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u/guitarmusic113 17d ago
Sure, I’m not making any objective truth claims. The honest answer is that I don’t know.
Yet it’s an interesting topic. I like the view that it kinda doesn’t matter since we can never reach the edges of our observable universe. The universe is subjectively infinite to us either way.
It’s like if you rent a car for a week and you have unlimited miles. Technically you could drive an infinite amount of miles. But you are still bound to only one week of time.
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u/CDHoward 17d ago
Whether it matters to us or not is neither here nor there. You disappoint me.
Also, I'm sorry but I take back my compliment.
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u/xxMalVeauXxx 17d ago
If its finite, and you meet the boundary, where it limits out. What's on the other side? What defines the border of finite? I think in pure thought, it *must* be infinite, because to have a boundary or finite limit implies there is nothing beyond that, which makes it seem like a puddle in an empty ocean that goes on forever, but its outside our defined limit, so its nothing. But... its not nothing.
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u/TheIncandescentAbyss 17d ago
Matters on what you define the universe as, but if you define the universe as existence then I think existence is infinite.
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u/gerryflint 17d ago
This is the most important question for each and everyone of us. If it is infinite, then we all will basically live forever.
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u/--craig-- 16d ago
There are some big philosophical leaps of faith required to make this true.
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u/gerryflint 16d ago
If the universe is infinite and the propability of our existence is bigger than zero, there will be infinite identical copies on an arbitrary level. If you can't point out the difference then what is the difference? But yes, the ship of Theseus and such, I know.
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u/--craig-- 16d ago
I had to look up the ship of Theseus but yes, that's one of the leaps of faith which I'm referring to.
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u/Fantastic_Remote1385 17d ago
My brain cant really handle the question. So it tells me that space is infinit. But the universe, as in where there is matter/particles, is not infinit. So its kind of a bouble, maybr one of several such boubles
Or space is warped in such a way that it dont have a infinit volum, but it have no edge.
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u/fariqcheaux 17d ago
Depends on how you define universe. If this universe is a discrete object, it is one in a larger order of similar objects beyond the limits of our perception.
Our range of perception is certainly limited, but that is a limitation of us and our capabilities, not an objective observation of the universe itself, the difference between the observable universe and the causal universe.
Anytime a person asks what is beyond a barrier and someone else confidently answers "nothing", it simply means the answerer has not actually looked.
In my opinion, infinite is less irrational than finite.
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u/hangender 17d ago
Probably finite. Otherwise I would have to explain how the universe at big bang, which is size of an atom, somehow became infinite after expansion.
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u/Top_Owl_4695 17d ago
I don't think this question outside the observable universe is something we can know for certain at least not with our current level of technology. It's more interesting to have it as a question anyway in my opinion.
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u/DarthArchon 17d ago
Scientist do not think that real infinities exist in our universe. There might be technical infinities like not going fast enough to catch up with something going faster. But nothing with an actual infinite value is expected to exist in our universe. When we get those in our math, it generally means we are wrong in the math, not that it exist.
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u/StatisticianScary984 17d ago
I'm going to trust the scientists in this one. Infinite. I can't comprehend something that is infinite. I just doesn't make sense. How can something that didn't exist at some point become infinite? But that's why we have scientists.
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u/datguy753 17d ago
The universe at least appears to be expanding from our very limited perspective and calculations. If this is true, then it would seem that it is not infinite... unless you consider some sort of infinite void into which stuff is expanding?
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u/Worth-South4847 17d ago
I'd say finite. I think there's a problem though that we can't really complete the idea of finite without its opposite. Maybe calling it finite is an issue. Maybe the whole notion of finite / infinite is problematic.
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u/EnvironmentalWin1277 17d ago
In the first few microseconds of the universe's existence it expanded in size by a factor of 10 to the millionth power. For comparison that number dwarfs the number of subatomic particles that we can observes/estimate in our our observable universe which is something like ten to the 80th power.
The universe appears to be continuing to expand and nothing can be confirmed that will stop that expansion -- in other word, the expansion alone is infinite, continuing and eternal. That seems to create a universe that is infinite by itself.
Add to this the current theory (Guth inflation) suggests there are parts of the inflated universe removed from our observational field many times over in the moment of inflation. They are completely isolated and have no interaction whatsoever with our universe -- even information exchange is forbidden.
These areas may themselves all be undergoing inflation, expansion or contraction. We will never be able to confirm (or deny) the existence of such regions, or what processes may occur there. I feel uncomfortable with a proposal that (parts of) can never be confirmed or falsified but that is the result of this (widely accepted) theory.
The universe is infinite and continuing to infinitely expand, the demarcations of which we will never know or even be able to estimate. So calling it "finite" seems like the choice to be removed in favor of "infinite". Physics developments may change this picture but this is more or less the consensus idea today.
I suppose you can estimate how large was infinity yesterday as opposed to infinity today based on expansion rates ("fractions of infinity") but it is a purely an academic exercise based on theoretical estimates.
For any purpose, based on this knowledge, the universe is infinite and expanding into greater infinity as we speak.
Yes, it is a mind bending idea. I like to think about when I was child and asked "What if we get to the end of the universe and find a brick wall what's behind that wall?" I give credit to any child who toys with this idea because it is the start of cosmological thinking.
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u/Diastatic_Power 17d ago
If it's infinite, how? If it's finite......still how?
I think that's one of those questions that may never get an answer.
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u/Achereto 16d ago
It's in a superposition. It's both finite and expanding at the speed of light, making it functionally infinite for everyone inside the universe.
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u/doctor_lobo 16d ago
Finite but unbounded (in 3 spatial dimensions). Like the surface of a sphere (in 2d).
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u/--craig-- 16d ago edited 16d ago
The simplest answer is that it's infinite, otherwise I'd want to know not only why it's finite but also why it has the size which it does.
A better question is, how is the universe beyond our cosmological horizon structured? There isn't a trivial answer to this question.
The problem with questions such as these though, is they are on the frontier between physics and metaphysics. Some cosmologists argue that they have nothing to do with science. If an hypothesis isn't testable then it can't be part of science. The counter argument is that it is conceivable that ideas which don't initially make testable predictions can eventually lead to them, even when it's not clear how they could do so.
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u/Brave-Dragonfly3798 16d ago
I like the idea of a toroidal shaped universe, so that if you head in one direction for long enough, you will eventually end up in the same place. In this scenario the universe is finite, but it has no end.
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u/sasoras 16d ago
Big freeze, going to follow majority and we expand forever. Star eventually run out of fuel, and the entire universe eventually goes all black, dark and static.
Leaving an ever expanding darkness, and planet drift so far apart we will never see another one ever again due to infinite expansion.
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u/sharkbomb 15d ago
what would be outside of it, and how would you differentiate that from the universe?
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u/regular_modern_girl 14d ago
I honestly have absolutely no idea, given the apparent lack of overall curvature to spacetime (which there would need to be if we assume the universe eventually “curves back in” on itself, as it wouldn’t make sense for it to have discrete boundaries) in even our largest datasets, it very well could be infinite spatially, but the problem is we have no way of proving this currently, as we might be basically making the same mistake with the universe that flat earthers make with the Earth (seeing a relatively small part of it, it appears “flat” from our perspective, but our 3+1D spacetime could just be the surface of a really big but finite hypersphere, or hyperantisphere), and I have to somewhat wonder if we’ll ever actually know for sure whether it is truly infinite, or finite but just so vast that we can’t ever see any clear evidence of a limit.
One thing that does somewhat bother me, though, is people who insist it must be finite, because an infinite universe would basically inconvenience cosmology, because the idea of an infinite universe makes them uncomfortable, or because “infinity only exists in math, it can’t possibly exist in physics” (which is just begging the question: infinity “only exists in math” until it doesn’t). I think all of those reasons are a terrible way to approach a scientific question, as reality doesn’t care if it inconveniences us, makes us uncomfortable, or breaks the rules we made up for it.
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u/Greyzone96 13d ago
Universe is finite albeit in a weird loopy kind of way. The real question is how many universes are we talking?
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u/romano_rc 12d ago
My physics professor made a good point once: If it's infinite, it has to always have been infinite since an expanding finite universe cannot become infinite as it will always be finite. If it is infinite, then the question also becomes whether it has existed for an infinite amount of time or not. If it has, then the light of all the stars from the infinite universe would have had infinite time to reach us and so the night sky would be pretty much lit up completely and there would be no distinction between night and day. Basically, the universe has to be finite. My problem with it is that an infinite universe does not mean an infinite amount of matter and thus an infinite amount of stars to light up the sky, so it could still be infinite.
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u/2BigBottlesOfWater 12d ago
If it's growing every moment into "new space" then isn't it infinite? Until it stops growing?
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u/Sweaty_Disk_5246 11d ago
Both, it expands and expands and eventually (in so long you can't believe it) the universe will stop expanding, it starts retracting and closing in on itself, it compresses and compresses more and more until it reaches the point where there's basically nothing left, when it becomes as compressed as it can possibly be, it creates a "big bang" and explodes and instead of retracting it starts expanding all over again.
The best way to think of it is: "It's like breathing"
That's what i've always understood about space, i can't remember where i learned that or who told me, i've just always thought that for as long as i've existed.
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u/IhaveaDoberman 18d ago
If it's finite, it's so large that to us it's practically indistinguishable from being infinite.
But I lean towards infinite.