If the universe is infinite, does that mean that everything exists somewhere?

In summary, the conversation discusses the concept of infinity and whether it means that all possibilities exist in the universe. While the universe may be infinite, it does not necessarily mean that all possibilities are realized. However, some theories, such as quantum mechanics, suggest that all possibilities must be realized. The conversation also touches on the idea of parallel universes and the existence of anti-particles. Overall, there is no consensus on the nature of the universe and its boundaries.
  • #1
Richard87
31
0
If the universe is infinite, does that mean that everything exists somewhere, besides obviously impossible things like a star that contains oxygen but doesn't contain oxygen or a 4-sided triangle?
 
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  • #2
It would if it was but it isn't
 
  • #3
Richard87 said:
If the universe is infinite, does that mean that everything exists somewhere, besides obviously impossible things like a star that contains oxygen but doesn't contain oxygen or a 4-sided triangle?
Well, consider this by way of analogy.

The set of all even numbers is infinite. I can go on counting even numbers for ever and ever and never reach an end.

But clearly the set of all even numbers does not include all possible numbers. It doesn't include, for instance, the number pi.

So even if the universe is infinite (we don't know whether or not it is), then that doesn't necessarily mean that all possibilities are realized.

However, there may be other reasons to believe that all possibilities are realized, mainly stemming from quantum mechanics, where we find, for instance, that if there is the possibility of matter inhabiting a region of space, then particles of that sort of matter will necessarily pop in and out of the vacuum. Another way of saying this is that in quantum mechanics, there mere possibility of existence forces existence. So it is not unreasonable to suspect that perhaps all possibilities must actually be realized.

This doesn't mean that anything and everything we can imagine occurs, of course. We can imagine quite a lot of impossible things, as you mention above. But we can also imagine a great many things that are not obviously impossible, and yet may turn out to be upon deeper inspection.
 
  • #4
Well so far we think that the Universe is finite, but with no boundaries. I really hate the word infinity >.< It's so unbelievably unfathomable, and people just toss it around as if it's just a large number. Good thoughts on the subject though.
 
  • #5
Entropee said:
Well so far we think that the Universe is finite, but with no boundaries.
I don't know who this "we" is, but so far as I am aware there is no consensus on this. Currently there just is insufficient evidence to say anything more than, "the universe is very, very big."
 
  • #6
So there might not be another Earth where I'm dating Jennifer Aniston? Dang.
 
  • #7
JnWaco said:
So there might not be another Earth where I'm dating Jennifer Aniston? Dang.
Well, just because you can imagine it doesn't mean it's possible. Consider, for a moment, how many opportunities you have had to get to know a beautiful actress. Probably not very many.

If, in this parallel world, you were the sort of person that had a life where you were in at least occasional contact with beautiful actresses, would your life be so different that that person even count as being you in the first place?
 
  • #8
Chalnoth said:
I don't know who this "we" is, but so far as I am aware there is no consensus on this. Currently there just is insufficient evidence to say anything more than, "the universe is very, very big."

Okay okay.. by "we" I mean Stephen Hawking haha

And if our anti particles formed anti people on an anti Earth we could have identical twins down to the last particle...maybe... ;P
 
  • #9
Entropee said:
Okay okay.. by "we" I mean Stephen Hawking haha
I'm pretty sure if you asked him straight up he'd say basically the same thing I just did. He did, of course, present the no boundary proposal (where the universe has no boundary either in time or in space), but that doesn't mean he would go so far as to claim that he knows it's true. He may think it likely (it's his idea, after all), but I doubt he'd go that far.

Entropee said:
And if our anti particles formed anti people on an anti Earth we could have identical twins down to the last particle...maybe... ;P
Well, we don't have anti-particles. That's one of the requirements of our cosmological observations: that early-on, there was a very small breaking of the symmetry between matter and antimatter.
 
  • #10
Well yes I agree with you that's why i said its what he "thinks" not knows, and would YOU go so far as to say that you "know" we don't have anti-particles? There may not be symmetry between matter and antimatter but It's still somewhere.
 
  • #11
Entropee said:
Well yes I agree with you that's why i said its what he "thinks" not knows, and would YOU go so far as to say that you "know" we don't have anti-particles? There may not be symmetry between matter and antimatter but It's still somewhere.
Yes, because we've actually looked for them. They're not out there. Basically, if the matter and anti-matter were physically separated, then you'd occasionally get clumps of matter running into clumps of anti-matter, causing rather large explosions. We don't see any of that.

Furthermore there's the problem that around the time of the emission of the CMB, our universe was extremely uniform, so that there was no way that normal matter and anti-matter could have been out of contact with one another.
 
  • #12
Thats true, but why then was the early universe so hot?

Also an unrelated question maybe you can answer for me, if most of the universe is hydrogen, why didnt all the hydrogen undergo nuclear fusion when the universe was as big as a baseball? Was it because the particles were different at the time?
 
  • #13
Entropee said:
Thats true, but why then was the early universe so hot?
It appears to be a result of the end of inflation. Basically, whatever it was that drove inflation had to have a whole lot of energy. When it decayed, it reheated our universe to a tremendous temperature.

Entropee said:
Also an unrelated question maybe you can answer for me, if most of the universe is hydrogen, why didnt all the hydrogen undergo nuclear fusion when the universe was as big as a baseball? Was it because the particles were different at the time?
Right, if the expansion rate would have been slower then, it would have. It would have progressed all the way to producing iron and that'd be the most common element.

But this takes time. First the protons and neutrons condense out of the quark-gluon plasma, so you have hydrogen right away. Then you start to make helium from the hydrogen. Then you start to make heavier and heavier elements.

As it turns out, the expansion rate was such that the universe cooled to where the nuclear fusion basically stopped by the time there was only around 25% helium sitting around, and long before more than trace amounts of anything else formed. Incidentally, this is even faster than it sounds, because much of the helium stemmed from the neutrons that were around early-on (when you have nothing but protons around, fusion takes a heck of a lot of energy, as you have to convert protons to neutrons, and because they repel one another, but when you have lots of neutrons sitting around it's much easier).
 
  • #14
o_O I thought we didnt have protons and neutrons in the early universe, wasn't there lots of particle decay so they would be different now?
 
  • #15
Entropee said:
o_O I thought we didnt have protons and neutrons in the early universe, wasn't there lots of particle decay so they would be different now?
Oh, well, in the very early universe there weren't any. But when the quark-gluon plasma cooled, well, protons and neutrons were the particles they condensed into: they're the lightest baryons. Heavier baryons are unstable and would have quickly decayed into protons and neutrons.
 
  • #16
About how long did it take for the quark-gluon plasma to cool?
 
  • #17
Entropee said:
About how long did it take for the quark-gluon plasma to cool?
Well, either way I don't know off the top of my head and you might be able to find it yourself as quickly as I could off of Google, but what specifically do you mean by this?

That is, are you asking how long the process of nucleosynthesis took, from the time the protons/neutrons condensed out of the plasma to the time that fusion stopped? Or are you asking how long after the end of inflation that this occurred?
 
  • #18
How long after the end of inflation is more what i meant. But yeah i could google it lol.
 
  • #19
Entropee said:
How long after the end of inflation is more what i meant. But yeah i could google it lol.
Hehe :) Yeah, I actually looked it up to. It's about three minutes ;)
 
  • #20
Wow nice haha, did you see my post on your profile?
 
  • #21
Chalnoth said:
Well, just because you can imagine it doesn't mean it's possible. Consider, for a moment, how many opportunities you have had to get to know a beautiful actress. Probably not very many.

If, in this parallel world, you were the sort of person that had a life where you were in at least occasional contact with beautiful actresses, would your life be so different that that person even count as being you in the first place?

lol, you sure know how to pour water on a nice thought!

just kidding
 
  • #22
JnWaco said:
lol, you sure know how to pour water on a nice thought!

just kidding
Haha, well, I think that it still can be extremely interesting.

Imagine, for a moment, just walking down the street. If we just take the part of your wave function that you know about today, and imagine all of the future parts (using the many worlds interpretation, of course), then those future parts will likely follow nearly the same but slightly different trajectories, for a while. I imagine it like a blurring of myself, some parts slightly ahead, some slightly behind. Some slightly to the left, some slightly to the right, etc. So the different parts of my wave function are slowly, very slowly dispersing. It might take many trips outside the house before anything interesting happens.

But then something interesting does happen: a car, going too fast, almost hits me. Well, it almost hits the "me" that I see, but there are other me's that were in slightly different places: some of them were just a little bit too close to the car, and got smacked. Suddenly, what were once very similar worlds become very different.

In another situation, something very similar is happening, but the event that causes the divergence is, say, I'm not paying attention to where I'm going, and I almost run into a pretty girl. I manage to apologize for the incident, strike up a conversation, and we start dating. Of course, that's just the "me" that I observe: some of the me's in other worlds either are far enough away that they don't almost run into her, or are close enough that they actually run into her and just end up pissing her off. In some others, the conversation takes a slightly different turn and we never see each other again. Etc. etc.

So there might well be people out there who, when I was a child, were still part of my wave function, the part that I remember, but who today have extremely different lives.
 
  • #23
Richard87 said:
If the universe is infinite, does that mean that everything exists somewhere, besides obviously impossible things like a star that contains oxygen but doesn't contain oxygen or a 4-sided triangle?


You must define the word 'infinite' before you can validly ask this question, and before anyone can validly answer it.

Does that make sense?

And if you're able to define it to your satisfaction, then you'll have answered your own question, I believe. :)
 
  • #24
Axuality said:
You must define the word 'infinite' before you can validly ask this question, and before anyone can validly answer it.
That's easy: if the universe is infinite in space, then even if one could travel much faster than the speed of light, one could travel forever without ever crossing one's path.

Another way of saying it is that if you could write down coordinates for the entire universe, then you'd never reach a number in those coordinates that was "beyond" the universe.
 
  • #25
Chalnoth said:
Haha, well, I think that it still can be extremely interesting.

Imagine, for a moment, just walking down the street. If we just take the part of your wave function that you know about today, and imagine all of the future parts (using the many worlds interpretation, of course), then those future parts will likely follow nearly the same but slightly different trajectories, for a while. I imagine it like a blurring of myself, some parts slightly ahead, some slightly behind. Some slightly to the left, some slightly to the right, etc. So the different parts of my wave function are slowly, very slowly dispersing. It might take many trips outside the house before anything interesting happens.

But then something interesting does happen: a car, going too fast, almost hits me. Well, it almost hits the "me" that I see, but there are other me's that were in slightly different places: some of them were just a little bit too close to the car, and got smacked. Suddenly, what were once very similar worlds become very different.

In another situation, something very similar is happening, but the event that causes the divergence is, say, I'm not paying attention to where I'm going, and I almost run into a pretty girl. I manage to apologize for the incident, strike up a conversation, and we start dating. Of course, that's just the "me" that I observe: some of the me's in other worlds either are far enough away that they don't almost run into her, or are close enough that they actually run into her and just end up pissing her off. In some others, the conversation takes a slightly different turn and we never see each other again. Etc. etc.

So there might well be people out there who, when I was a child, were still part of my wave function, the part that I remember, but who today have extremely different lives.


I'm a layman, just getting into physics, but that makes sense. So are there infinite universes, or just one universe that is infinite. I saw a special on the Discovery channel where they said there were an infinite number of universes in the "multiverse".

How was that proven (or derived)?
 
  • #26
Chalnoth said:
That's easy: if the universe is infinite in space, then even if one could travel much faster than the speed of light, one could travel forever without ever crossing one's path.

Another way of saying it is that if you could write down coordinates for the entire universe, then you'd never reach a number in those coordinates that was "beyond" the universe.

You're a smart guy/girl obviously, and thanks for your post.

But he didn't SAY 'infinite in space', like you did. He said just 'infinite'.

But despite that, no matter how fast you travel, you would never cross your own path in a FINITE universe, if the universe was constantly creating itself faster than you could get there.

And as to your second definition, you can't write down the coordinates for an entire infinite universe. And even if you tried, you might never reach a number outside the universe because the universe may be growing faster than you can chart it...- while still remaining currently finite.

So again, like the original poster, you can't really use the word infinite even in a phrase such as 'infinite in space', until you define the word infinite. As soon as you do, then you'll realize that infinite has but one definitive meaning. All others are derived for context.

Not to mention after all, that you gave descriptions of 'infinite in space', not a definition of 'infinite in space'.

So my proposal remains- You must define 'infinite' before you use the term.
 
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  • #27
Richard87 said:
If the universe is infinite, does that mean that everything exists somewhere, besides obviously impossible things like a star that contains oxygen but doesn't contain oxygen or a 4-sided triangle?

Yes Richard87, if the universe is TRULY infinite, it means that it contains all things real.

And if you're wondering if you're dating Jennifer Aniston somewhere, I can tell you 'yes, you are', and tell you how to find that "part" of the universe, but don't ask please. :)
 
  • #28
Axuality said:
You're a smart guy/girl obviously, and thanks for your post.
Guy, actually :)

Axuality said:
But he didn't SAY 'infinite in space', like you did. He said just 'infinite'.

But despite that, no matter how fast you travel, you would never cross your own path in a FINITE universe, if the universe was constantly creating itself faster than you could get there.
True, but that's usually what people mean. And that's why I said, "even if you could move at arbitrary speed" :) Perhaps a better way of stating it is that if you could freeze the expansion, then you could travel forever without crossing your own path in an infinite universe.

Axuality said:
And as to your second definition, you can't write down the coordinates for an entire infinite universe. And even if you tried, you might never reach a number outside the universe because the universe may be growing faster than you can chart it...- while still remaining currently finite.
Well, in general this is true, you can't. But in special cases it's entirely possible (because the real numbers are also infinite). A flat, uniformly-expanding universe would be one example, where simple co-moving coordinates work just fine. The infinite extent actually doesn't affect this.

Mathematically, infinity is quite well-defined. See the extended real number line here.
 
  • #29
I was reading about infinity - and aren't there differing orders of infinity, and even sets of infinite numbers that still exclude other numbers?

Like the set of all even numbers is infinite. But it does not include the number 1, 3, 5, 7, etc. So even if the universe was infinite, there could still be an "everthing" that doesn't exist?

Perhaps this is more of a philosophical question.
 
  • #30
JnWaco said:
I was reading about infinity - and aren't there differing orders of infinity, and even sets of infinite numbers that still exclude other numbers?

Like the set of all even numbers is infinite. But it does not include the number 1, 3, 5, 7, etc. So even if the universe was infinite, there could still be an "everthing" that doesn't exist?

Perhaps this is more of a philosophical question.
Well, there could be an infinite number of possible things that still don't exist. However, I don't think that would count as "everything".
 
  • #31
Chalnoth said:
Well, there could be an infinite number of possible things that still don't exist. However, I don't think that would count as "everything".

Well, I was referring to the original poster's question - poor choice of words on my part- I just meant that an infinite universe could still not have everything exist, and in fact there could be an infinite number of things that wouldn't exist.
 
  • #32
Chalnoth said:
However, there may be other reasons to believe that all possibilities are realized, mainly stemming from quantum mechanics, where we find, for instance, that if there is the possibility of matter inhabiting a region of space, then particles of that sort of matter will necessarily pop in and out of the vacuum. Another way of saying this is that in quantum mechanics, there mere possibility of existence forces existence. So it is not unreasonable to suspect that perhaps all possibilities must actually be realized.

This has been my increasing feeling as well; that is, that there is no actual difference between possibility and actuality. It even negates the necessity for "meaning" or an "origin" -- things are simply because they can be. To my knowledge, however, it's still not the mainstream interpretation of quantum mechanics in the physics community (still Copenhagen?), though it's not clear how useful a "mainstream" stance on philosophy is.

Anyway, so that I don't venture too far off-topic, to address the original question... we still can't say whether the universe is infinite or finite and it's possible we'll never know. If the universe is finite, it's likely that our particle horizon back to inflation (the largest comoving distance we can possibly observe) is a good deal smaller than the full extent of the universe. If inflationary theory is correct, the rapid expansion of the scale factor in the early universe would have caused our effective horizon to contract from its pre-inflation size and render much of the universe unobservable.
 
  • #33
SpaceTiger said:
This has been my increasing feeling as well; that is, that there is no actual difference between possibility and actuality. It even negates the necessity for "meaning" or an "origin" -- things are simply because they can be. To my knowledge, however, it's still not the mainstream interpretation of quantum mechanics in the physics community (still Copenhagen?), though it's not clear how useful a "mainstream" stance on philosophy is.
So far as I am aware, among people that have actually thought about this in depth, the many-worlds interpretation is predominant. I think the Copenhagen interpretation is just a result of the "shut up and calculate" school of thought, where a large number of physicists just don't want to bother with these sorts of details, and would rather just get to work learning other things.

More recently, however, quantum computing research has forced many physicists to look in more detail at the specific nature of collapse, and so I expect that the "shut up and calculate" school won't last very long, as the Copenhagen interpretation doesn't actually say what happens at the boundary of collapse. It doesn't say when collapse happens, or how it happens.

There are also a few other schools of thought, but as far as I know they are strong minority views.

Anyway, if you're interested in reading a bit more on the "anything that can happen does happen" possibility, you may be interested in this paper by Max Tegmark:
http://arxiv.org/pdf/0704.0646

It's highly speculative, and would be extremely difficult to find any evidence in favor of it, but I find it quite the intriguing idea.
 
  • #34
Chalnoth said:
Anyway, if you're interested in reading a bit more on the "anything that can happen does happen" possibility, you may be interested in this paper by Max Tegmark:
http://arxiv.org/pdf/0704.0646

Thanks for the link. I knew that Max was vocal on these issues, but hadn't seen his paper.
 
  • #35
Richard87 said:
If the universe is infinite, does that mean that everything exists somewhere

No, of course not.

Some infinities are bigger than others, and the infinity of distinguishable configurations of things is a factorial kind of infinity that is always much, much bigger than the infinity of the number of things.

Think of building a universe as a collection of things, starting with a just a few. As your universe grows the number of ways the things can be arranged differently grows very much faster than their number. So all possible configurations (everything) is something that can never be realized. You needn't even struggle with the impossibility of imagining infinity. And that old idea of monkeys typing Hamlet, given enough time, is nonsense for much the same kind of reason.
 
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<h2>1. What is the concept of an infinite universe?</h2><p>An infinite universe is a theoretical concept in which the universe has no boundaries or limits. It suggests that the universe is constantly expanding and has no definite end or edge.</p><h2>2. Does an infinite universe imply the existence of multiple copies of ourselves?</h2><p>The concept of an infinite universe does not necessarily mean that there are multiple copies of ourselves. While it is possible that there could be other versions of ourselves in different parts of the universe, there is no scientific evidence to support this idea.</p><h2>3. If the universe is infinite, does that mean there are an infinite number of planets and galaxies?</h2><p>Yes, if the universe is truly infinite, then there would be an infinite number of planets and galaxies. However, it is important to note that the observable universe, which is the part of the universe that we can see and study, is not infinite.</p><h2>4. Is it possible for there to be an infinite number of universes?</h2><p>While there are theories that suggest the existence of multiple universes, known as the multiverse theory, there is currently no scientific evidence to support the idea of an infinite number of universes.</p><h2>5. How does the concept of an infinite universe affect our understanding of time and space?</h2><p>An infinite universe challenges our traditional understanding of time and space. It suggests that the universe has always existed and will continue to exist forever, making the concept of a beginning or end of the universe irrelevant. It also raises questions about the shape and structure of the universe, as well as the possibility of parallel universes.</p>

1. What is the concept of an infinite universe?

An infinite universe is a theoretical concept in which the universe has no boundaries or limits. It suggests that the universe is constantly expanding and has no definite end or edge.

2. Does an infinite universe imply the existence of multiple copies of ourselves?

The concept of an infinite universe does not necessarily mean that there are multiple copies of ourselves. While it is possible that there could be other versions of ourselves in different parts of the universe, there is no scientific evidence to support this idea.

3. If the universe is infinite, does that mean there are an infinite number of planets and galaxies?

Yes, if the universe is truly infinite, then there would be an infinite number of planets and galaxies. However, it is important to note that the observable universe, which is the part of the universe that we can see and study, is not infinite.

4. Is it possible for there to be an infinite number of universes?

While there are theories that suggest the existence of multiple universes, known as the multiverse theory, there is currently no scientific evidence to support the idea of an infinite number of universes.

5. How does the concept of an infinite universe affect our understanding of time and space?

An infinite universe challenges our traditional understanding of time and space. It suggests that the universe has always existed and will continue to exist forever, making the concept of a beginning or end of the universe irrelevant. It also raises questions about the shape and structure of the universe, as well as the possibility of parallel universes.

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