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Old Sep 20th 2013, 12:56 PM   #1
MBW
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Does Infinity Belong in Reality?

While infinity is a valid (if mind bending) mathematical concept, there are many who argue it cannot exist in reality.

While I find myself leaning toward that view on purely gut feeling, it is difficult to put forward a clear reason why infinity should be rejected.

I think my best attempt is to question if there could possibly be an infinite number of ways to organise existence.

I have seen the idea proposed that in an infinite existence there will be another universe just like this one.
But if both universes are identical, then I don't see how it can be determined that they are not actually the same!
Then if existence is repeating itself, is it really infinite?

There are also infinities involved in black holes, re-normalisation, and other esoteric areas of physics,
but I regard these as problems in the theory that need addressing rather than genuine instances where infinity enters reality.
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Old Sep 20th 2013, 03:14 PM   #2
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Originally Posted by MBW View Post
While infinity is a valid (if mind bending) mathematical concept, there are many who argue it cannot exist in reality.

While I find myself leaning toward that view on purely gut feeling, it is difficult to put forward a clear reason why infinity should be rejected.

I think my best attempt is to question if there could possibly be an infinite number of ways to organise existence.

I have seen the idea proposed that in an infinite existence there will be another universe just like this one.
But if both universes are identical, then I don't see how it can be determined that they are not actually the same!
Then if existence is repeating itself, is it really infinite?

There are also infinities involved in black holes, re-normalisation, and other esoteric areas of physics,
but I regard these as problems in the theory that need addressing rather than genuine instances where infinity enters reality.
In the early days of QFT there were a large number of calculations that went to infinity. Some of those calculations have now been fixed, but many still remain. It became obvious that these infinities were due to improper theoretical knowledge of how to deal with them. Because of this there was a 10 - 15 year long assumption that any calculation that resulted in an infinite answer could simply be dropped out of the calculation. Essentially infinity = 0!

I'm not heavily on the side of infinity not existing. Both Physicists and Mathematicians have theoretically used the idea to great success. But I will say that I doubt any of these infinities have any real basis in Nature. But that is more of an opinion rather than a logical argument. I've just seen too many theoretical infinities turning out to be "mere" large numbers when you add things in like friction, viscosity, and hummus.

-Dan
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Old Sep 23rd 2013, 10:01 AM   #3
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What's the point?

I think my emotional reasons for rejecting infinity can be expressed thus:
If the universe is infinite, then anything and everthing is possible,
In fact anything and everything is inevitable.

In which case, the study of (meta)physics becomes rather pointless since the answer is simply that things are the way they are at this point in existence, but there is no reason to believe that this implies anything about anything else.
We could be in a purely random piece of existence where (briefly) a set of rules (which we call physics) seem to hold.
But there is no guarantee that they will continue to hold.

I feel that there must be some limits on what can and can't exist.
If infinity can be logically excluded, this imeadiately sets boundaries to what can and can't be.
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Old Sep 23rd 2013, 10:47 AM   #4
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Originally Posted by MBW View Post
I think my emotional reasons for rejecting infinity can be expressed thus:
If the universe is infinite, then anything and everthing is possible,
In fact anything and everything is inevitable.
I don't think this flows logically. There is nothing about an infinite universe that says the laws of physics everywhere aren't the same - for example an infinite universe does not mean that the 2nd Law of Thermodynamics doesn't apply everywhere. However, putting such restrictions on how things behave does imply that in an infinite universe there must be an infinite number of copies of everything that can physcally exist. Thus the complex arrangement of atoms and molecules that make up "me" must exist elsewhere - and elsewhen - in an infinite number of places and times. Now that's a scary thought! So I come down on the side of the universe not being infinite, and hence there really is no infinity in nature.
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Old Oct 9th 2013, 06:50 PM   #5
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I don't like the idea of infinity because if you put infinity in something like mass, etc - any property - it's just weird. But then if you apply it to, say, spacetime, or the size of the universe... something is meaningless without nothing, no? But if the universe is infinite... where's the nothing? It can't be outside the universe, the universe is infinite!
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Old Nov 27th 2013, 06:12 AM   #6
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I have found infinity easier to work with if you consider it as the ultimate whole. any subset of infinity can be considered as dimensionless or with relative dimension. We normally use the relative approach to problems, however I have found that taking a look at problems from the former can give insight into the latter. My favorite example of this is looking at a parabola. If we look at it relative to some limit it is a curve, however if we look at it as a subset of infinity it is not as esoteric as one might first conclude, it is a simple right angle. likewise our observable universe would resolve to a single point, a 2 dimensional disk, or a torus. depending on what criteria you use to define the limits of the observable universe. A simple statement of this is that no matter what your frame of reference is, infinity is always an additional reference(and a very useful one!).
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Old Nov 27th 2013, 06:22 AM   #7
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Originally Posted by ChipB View Post
I don't think this flows logically. There is nothing about an infinite universe that says the laws of physics everywhere aren't the same - for example an infinite universe does not mean that the 2nd Law of Thermodynamics doesn't apply everywhere. However, putting such restrictions on how things behave does imply that in an infinite universe there must be an infinite number of copies of everything that can physcally exist. Thus the complex arrangement of atoms and molecules that make up "me" must exist elsewhere - and elsewhen - in an infinite number of places and times. Now that's a scary thought! So I come down on the side of the universe not being infinite, and hence there really is no infinity in nature.
I have considered this idea for quite sometime, and it would seem that if time/space is infinite it must be a fractal. I have a thought that should take some of the fear out of multiples of yourself... You might exist in many fractal levels of yourself with one consciousness!
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