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Richard87
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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.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?
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."Entropee said:Well so far we think that the Universe is finite, but with no boundaries.
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.JnWaco said:So there might not be another Earth where I'm dating Jennifer Aniston? Dang.
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."
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:Okay okay.. by "we" I mean Stephen Hawking haha
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.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
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.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.
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:Thats true, but why then was the early universe so hot?
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.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?
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.Entropee said: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?
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?Entropee said:About how long did it take for the quark-gluon plasma to cool?
Hehe :) Yeah, I actually looked it up to. It's about three minutes ;)Entropee said:How long after the end of inflation is more what i meant. But yeah i could google it lol.
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?
Haha, well, I think that it still can be extremely interesting.JnWaco said:lol, you sure know how to pour water on a nice thought!
just kidding
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?
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.Axuality said:You must define the word 'infinite' before you can validly ask this question, and before anyone can validly answer it.
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.
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.
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?
Guy, actually :)Axuality said:You're a smart guy/girl obviously, and thanks for your post.
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: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.
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.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, there could be an infinite number of possible things that still don't exist. However, I don't think that would count as "everything".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.
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".
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.
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.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.
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
Richard87 said:If the universe is infinite, does that mean that everything exists somewhere