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Infinite Universe = Impossible


worir4

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I think that an infinite universe is impossible.

Every event has a chance of happening. An example is that there is that you could turn into a whale right as you read this. This is possible because of atoms teleporting.

The chance that all of your atoms will swap places with a whale's is really really small and yet it is still possible. For this thread let's take the chance of it happening to be 1 in 5 billion.

In an infinite universe this has had an infinite number of chances to happen, so it would be 1 in 5 billion multiplied by infinity which = infinity which means it has already happened and infinite number of times.

Following this principle that every event has a chance of happening and that the universe is infinite, everything has happened already an infinite number of times. This can't be true because if the universe is infinite, at the first instance of time every thing would have happened. This includes an event that would have destroyed the Universe.

This event would have meant that the infinite universe would cease to exist. I do not know what this event would be, but if ever event is possible then this would have already happened in an infinite universe. Because this hasn't happened (We are still here) that means that the universe is not infinite because that event has not had and infinite amount of chances to happen.

Does this prove that the universe is not infinite?

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No.

Damn too short =)

The univers is not infinit but closed in it self, so there is no visible border for us, like there is no vissible border for some 2 dimensional lifeform living on the surface of a sphere.

Greetings

Ben

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I realize this might be a very stupid question, but it's really bugging me. How can we say the universe might be infinite if it is expanding? I mean, in order to expand itself it must be expanding into something, which in turn means it has a border, which in turn means it's not infinite?

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To answer the OP without resorting to reality, you're forgetting that there may be no way for the universe to end. Then, with your logic, the infinite universe's very existence proves the fact that nothing can happen to end that existence.

In reality though, we don't really have any reason to think it's infinite, and we might (I don't know a whole lot on the topic) have good reason not to (big bang model seems to imply that it was limited at some point).

I realize this might be a very stupid question, but it's really bugging me. How can we say the universe might be infinite if it is expanding? I mean, in order to expand itself it must be expanding into something, which in turn means it has a border, which in turn means it's not infinite?

I'm pretty sure that it's mathematically possible to have infinities of different sizes, so the universe's size could just be infinity +1 over and over, if that makes any sense. When things get this abstract, we don't really have to assume that it's expanding into anything, it could be expanding into complete nothingness. There's really no way to know what's outside though, so it's all guesswork.

Also, if there's a 1 in 5 billion chance for someone to turn into a whale, even if it's over the course of a lifetime, there would be about 1.5 people swapped with whales on the planet right now. Teehee.

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The universe can't have a border (for the space) anyway; what'd happen if you lived near that border ? Inhomogeneity (like, not so many matter near the border) ? Anisotropy (the border must have a preferred (like, nearer) side) ? What if there's a star very near to it ? Where would the light go ?

If there's any border for the Universe, it'd be time; the space might be infinite, least are for a "flat" universe (like, else it wont be isotropic as there'd be borders). Hence why, if the Universe is finite but unbounded (no border), you only have an answer : it's not flat, it's positively curved (ie. closed).

Now, how to get the radius of curvature...

EDIT : I don't say that having an infinite universe isn't possible anyway. Probably once every billions of millennia, a mote of dust vanish away...

Edited by YNM
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I realize this might be a very stupid question, but it's really bugging me. How can we say the universe might be infinite if it is expanding? I mean, in order to expand itself it must be expanding into something, which in turn means it has a border, which in turn means it's not infinite?

I'm not an expert on the subject by ANY means, but I wanted to say this:

The key thing here, is that you are assuming there has to be a "something" for our universe to "expand into". Where, as far as I know, space does not require space to expand. There doesn't need to be something to expand into, it is just expansion. It's an interesting thing to think about. I believe there is a Through the Wormhole episode which covers these very ideas. If I'm not mistaken it is in season 4, or 5.

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There were some folks saying a few years ago that since it appears space is flat, that must mean the universe is infinite and that somewhere out there is an exact copy of Earth, on which lives an exact copy of you. Given infinite star formation events, after all, there should be an exact copy of Earth, and even the entire Milky Way galaxy out there.

I too find this absurd. Here I thought that the leading theory for the formation of the universe was that everything began in a Big Bang, and the the universe initially was an extremely small (atomic scale) closed sphere of space-time with incredibly high energy density, and that inflation blew it out to macroscopic proportions. Where did I go wrong with that? Because if that's true, then an infinite universe with infinite matter is impossible, because the universe started out with a finite size and finite energy density. The only way around that is if there were there regions casually disconnected from us by the expansion of space where new matter was created. How does that work?! Expanding faster than the speed of light allows a finite universe to become infinite?!!?

The only way in which I understand the universe being infinite is if you were to try to transverse it. The farthest regions are expanding away from us faster than the speed of light, so we cannot reach them. If you were to travel across the universe in a spaceship going 99.99999% of c, what you would observe is a universe that appears to be spatially infinite. You could travel forever in any direction and never return to where you came from. However, while you would observe that the universe appears to be infinite it its spatial dimensions, you would not observe it to be infinite in its quantity of matter, because as your voyage progressed, you'd observe the density of matter decrease with time as the universe expanded.

Edited by |Velocity|
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There were some folks saying a few years ago that since it appears space is flat, that must mean the universe is infinite and that somewhere out there is an exact copy of Earth, on which lives an exact copy of you. Given infinite star formation events, after all, there should be an exact copy of Earth, and even the entire Milky Way galaxy out there.

I too find this absurd. Here I thought that the leading theory for the formation of the universe was that everything began in a Big Bang, and the the universe initially was an extremely small (atomic scale) closed sphere of space-time with incredibly high energy density, and that inflation blew it out to macroscopic proportions. Where did I go wrong with that? Because if that's true, then an infinite universe with infinite matter is impossible, because the universe started out with a finite size and finite energy density.

The only way in which I understand the universe being infinite is if you were to try to transverse it. The farthest regions are expanding away from us faster than the speed of light, so we cannot reach them. If you were to travel across the universe in a spaceship going 99.99999% of c, what you would observe is a universe that appears to be spatially infinite. You could travel forever in any direction and never return to where you came from. However, while you would observe that the universe appears to be infinite it its spatial dimensions, you would not observe it to be infinite in its quantity of matter, because as your voyage progressed, you'd observe the density of matter decrease with time as the universe expanded.

Just a semantic nitpick - but no one human will understand anything being infinite. By definition it is beyond comprehension. So when you talk about personal understanding of a finite or infinite universe - we are talking things which you can't physically understand by default. What you say does seem to make sense logically, though. Its just a shame in the world of quantum physics, logic tends to lead you in the wrong direction.

A not-as-popular theory I thought was fairly clever is that our universe is a finite "sheet" set beside other finite "sheets" in sort of super-universe. It also explains (well, gives an unproven explanation for) why our cosmic microwave background has cold and hot spots (where our "sheet" is close to another)

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Just a semantic nitpick - but no one human will understand anything being infinite. By definition it is beyond comprehension. So when you talk about personal understanding of a finite or infinite universe - we are talking things which you can't physically understand by default. What you say does seem to make sense logically, though. Its just a shame in the world of quantum physics, logic tends to lead you in the wrong direction.

A not-as-popular theory I thought was fairly clever is that our universe is a finite "sheet" set beside other finite "sheets" in sort of super-universe. It also explains (well, gives an unproven explanation for) why our cosmic microwave background has cold and hot spots (where our "sheet" is close to another)

No, I don't think that infinite is impossible to understand. Everything in the universe follows rules, and those rules are possible to understand. Nothing that derives from those rules are impossible to understand, you just have to find the right way of htinking about it.

For example, quantum mechanics starts to make a lot more sense if you just drop the silly notion that particles are actually particles. :)

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There were some folks saying a few years ago that since it appears space is flat, that must mean the universe is infinite and that somewhere out there is an exact copy of Earth, on which lives an exact copy of you. Given infinite star formation events, after all, there should be an exact copy of Earth, and even the entire Milky Way galaxy out there.

And that universe doesn't need to be infinite. If the number of atoms in an universe exceed a Googleplex (10^10^100, 10 to the power of a Google), every single molecular arrangements will be made, and so the structures will start repeating themselves, thus creating theoretically exact copies of things, so maybe our solar system, the Earth, and us. If there were that many atoms in the universe, then there would probably be an exact copy of you, elsewhere in the universe.

Now in our universe there are approx. 10^80 atoms, so there's no cloning to be worried about.

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No, I don't think that infinite is impossible to understand. Everything in the universe follows rules, and those rules are possible to understand. Nothing that derives from those rules are impossible to understand, you just have to find the right way of htinking about it.

For example, quantum mechanics starts to make a lot more sense if you just drop the silly notion that particles are actually particles. :)

Definitely an interesting take on it but my opinion (again, Im not a scientist of any sort so I concede I may be wrong) is as follows:

If you personally are able to understand infinity, then by golly you deserve a medal of some sort. (Or I should be in the dumb-house)

Yes, of course we know the definition of inifinity, and we can use infinity in mathematics... But that != comprehension of what infinity is. You have no way to picture, or imagine an infinity. Not to mention, there are infinities larger (and smaller) than other infinities. And this is getting on the more philosohpical side of things, but you cannot place infinity under a ruleset because if there is an infinity, there is an infinite amount of rulesets, and an infinity of possibilities in each infinite ruleset, blah blah blah you see what Im trying to say. It's too big for our tiny brains to compute.

TLDR: You can make use of infinity, but you cannot comprehend what infinity is

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No, I don't think that infinite is impossible to understand.

1 + 2 + 3 + ... (to infinity) = -1/12

While the proof is easy to understand, infinity itself is difficult to understand. For example is ∞ < ∞ + 1?

The answer seems easy: The comparision is true.

But infinity also means it that for every number there is also a number + 1. This changes the comparision to ∞ < ∞. Wait! What!?

The best way to get around that insanity is to see infinity as a concept instead of a number with neverending digits. A quite difficult to grasp concept though, eg. there are two different infinitys which you can convert into each other.

Edited by *Aqua*
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As far as I had read, thus far our observations of the universe have been unable to detect any curvature, and so the current assumption is that either the universe beyond the visible is incomprehensibly huge so as to make the curvature undetectable, or simply infinite. An infinite universe does not conflict with the concept of the big bang, however, as an infinite universe that was infinitely shrunk down to infinite density, could still be infinitely sized, simply less infinitely. Infinite universe does not mean things like infinite resources, as it has been pointed out that as you travel through time, the universe will expand and there is a finite limit thusly set on how much can be encountered, even travelling at c.

An infinite universe also does not mean every single possibility has to exist. Hitchhiker's Guide to the Galaxy uses such a concept to claim that the existence of a planet of living mattresses is reasonable, and rather than manufacturing they're simply grown in farms and culled. This, however, ignores that at most, an infinite universe can only contain possible things - a living mattress is not one of them. Similarly, while some identical clone of earth infinitely far away in this infinite universe would be possible, spontaneously becoming a whale would not be. While particles can tunnel to arbitrary configurations, they use their energy to do so, and the particles in your body and around you would not contain enough energy to reach that configuration. A whale might occasionally form inside a star for a few very bizarre instants, but an infinite universe with infinite possibilities, does not mean ALL things are possible.

To describe similar numerically, consider the infinite decimal 0.101100111000..., that continually increases the number of digits in each section. This number is infinite, and contains infinite variations on data, yet it never contains a 2, and it contains "101" only once. Infinity does not necessitate encompassing all - that concept falls to numbers being transcendental, which we have yet to prove any number is, but we believe pi may be such. Pi is one of very few infinite decimals truly believed to contain all possible combinations - including, theoretically, its own digit sequence within itself. But because it's infinite, it can be an infinite length before beginning that, and so even though that suggests pi is a repeating decimal, it is not a decimal that can be repeated.

Infinities are weird, and based on that small sample of pi's weirdness, it's very unlikely that anything that physically exists, including an infinite universe, or even an infinite multiverse of infinite universes, could be transcendental on any level.

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No. Whether or not the universe is infinite in space, we know its finite in time, so there's a finite volume of spacetime within our past light cone and only events within that cone can affect us.

This is how I observe it to be so too. The same description, but from looking in the opposite direction (forwards), is that space expands in front of us (I guess, no idea how accurate a statement that is :P ).

Or as you say, it is limited to within our light cone for the past events that effect us (at 13 or so billion light years across).

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It is not know whether the universe is infinite or not, and you're right that the chances of turning you into a whale are not zero. Still, you're forgetting the time.

The universe had its beginning around 13 billion years ago and it will probably end some day. So, if the concequences for turning you into a whale are right once in a 'brazillion' years then it might still not happenned since very little time has past since the Universe came into existence. And when the time comes for its thermal death there still might be not the right moment :)

Edited by cicatrix
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Space isn't infinite. For space to exist there must be energy and the amount of energy in the universe is limited. Therefore space must be limited too.

Some scientist believe the universe warps around itself. If you "pass" the border on one end you just appear at the other end again making it "infinite". But a clock hand also believes its 2D world is infinite.

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Penny for your thoughts:

Even if it isn't infinite, does it matter? At the current rate of technological advances, we'll probably wipe ourselves out before we have the chance to prove it's not, and even so, since the universe expands(or did) faster than the speed of light, we'll need something along the lines of an Alcubierre drive to even think of reaching it's edge, and that's when it's had several billion years of a headstart on us. The way I see it, it's better to delude yourself with the infinite probability theory than to think we could reach the edge of the universe. Speaking of which, what're the chances do you think there is another me writing up another post just like this on a forum about sending little green men to space in ridiculous contraptions of rockets?

That's not even tackling the problem of dark energy/matter, which would make things a lot more confusing when talking about the size of malleable material in the universe with which probability could go hogwild.

Cheers,

Caveman

Edited by CavemanNinja
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Even if it isn't infinite, does it matter?

It's fundamental for our understanding of the universe. You just can't exclude that.

Speaking of which, what're the chances do you think there is another me writing up another post just like this on a forum about sending little green men to space in ridiculous contraptions of rockets?

Unknown but the probability is greater than 0.

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