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Posted: Sun Sep 18, 2005 8:56 am
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Posted: Sun Sep 18, 2005 10:49 am
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Posted: Sun Sep 18, 2005 10:51 am
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Posted: Tue Oct 18, 2005 12:37 pm
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Posted: Sat Dec 10, 2005 7:40 am
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Posted: Sat Jun 17, 2006 9:20 pm
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Posted: Sun Jun 18, 2006 3:34 pm
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Posted: Mon Jul 24, 2006 7:04 pm
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Posted: Tue Aug 01, 2006 3:58 am
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Posted: Sat Nov 18, 2006 9:19 am
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Posted: Mon Jan 01, 2007 9:53 pm
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Posted: Mon Jan 15, 2007 12:00 am
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Posted: Fri Jan 19, 2007 3:24 pm
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Posted: Thu Feb 01, 2007 3:44 pm
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This question, and a number of the points brought up in the responses, depend really on what we're talking about by 'infinite'.
Infinite can be both a concept or a true number - it can refer to the idea of a process which goes on indefinitely, or it can be a reference to a set of items, things or existences which have no end to them. Numbers can be used to show these two different meanings for 'infinity':
If we were to begin counting, aiming to get to the highest number (which does not exist), then we would undertake an infinite process, with no end. The entire process is something 'infinite'.
However, the 'number infinite' works like this (it's quite a famous example, though I can't recall right now who came up with it. I'm gonna state The Science Of Discworld III as my reference): A man has a hotel with an infinite number of rooms. Each room exists as a finite thing, but is part of an infinite series - just as the days of the week match the series of 'seven', so these rooms match the series of 'infinite'. Each room can only fit one person in, and each room is occupied. So what happens when someone else comes along and wants a room? Simple - you move everyone up into the next room (person from room 1 into room 2, person from room 2 into room 3 etc) and put the newcomer into room 1. Why can you do this? Because there are infinite rooms. No matter how many times someone comes wanting a room, there will be room for them - infinity will in effect become bigger, but remain infinity. Even if an infinite number of people arrived, there would still be room for them, and there would remain an infinite (but a bigger infinite - but don't even try to get your head around that) number of rooms in the hotel.
Which is why there can be such a thing as infinity+1, and then again, there can't be. It depends on which type of infinity you're talking about.
So if we're asking 'Is the universe an infinite process?' then at the moment the good odds are on 'yes.' However, we will probably never know for sure, unless we manage to prove string theory right or wrong.
If we're asking whether it is infinite numerically, and therefore probably in volume, it appears that the answer is no - but on second glance it may be yes.. because infinity can indeed expand, as shown above.
Though here I'm using 'universe' in the modern context, which tends to mean 'The physical spacetime which we humans inhabit, and which obeys the rules of physics that we observe'. However, if we were to use it in the 'everything that exists' definition, then there is an uncertainty about whether or not the first definition is the same as the second definition. The 'multiverse' is a possibility brought onto being by quantum mechanics and string theory. However, it is very much a possibility. The physicists argue that in a universe which is infinite (and string theory implies this), then everything which is possible must therefore exist somewhere/when (spacetime is odd like that). However, not only are we uncertain of the infinite nature of the universe, but we are also unsure of the genuine applicability of this concept. Though the mathematics works well if we use a 'multiple worlds' perspective, there is no reason to assume that this is physically accurate - Newton's gravity works mathematically -up until the subatomic level where quantum takes over. So though we can trust the maths, it is clearly not a valid representation of the real world.
It's a bit of a Schroedinger's cat situation (search wikipedia if you're unfamiliar): though the maths say that the cat in the box is both living and dead, we know that this cannot be the case. What physicists say is that this means that the cat is living in one universe, and living in another - they 'reify' the physical equation used to work out whether the cat is alive or dead. But the evidence that supports the reification of this equation into a real universe model is non-existent. We must always remember that maths is a model, not the real thing.
Now, 'if the universe was infinite, would it repeat itself?' I'll use the first definition of universe to make things more sensible. Not if it were an infinite process: it would simply continue onwards. If it were infinite numerically, then this has very little bearing on whether it would repeat itself or not - it boils down to whether or not the universe will eventually contract after it's expansion.
Oh, and we know that the Earth is round because of the way it acts gravitationally. A curves in spacetime are caused by mass, and the curves create gravity. The only way the Earth could create the illusion of being round whilst being flat would in fact to not be flat, and to be far denser than it actually is. Plus, a flat Earth poses the standard problem - why have the seas not flown over the edge?
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Posted: Wed Apr 11, 2007 11:41 am
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