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Is There Such a Thing As Absolute Hot?
AlpineR writes "Is there an opposite to absolute zero? An article from PBS's NOVA online explains several theories of the maximum possible temperature. Maybe it's the Planck temperature, 10^32 K, beyond which the known laws of physics break down. Or maybe just 10^30 K, the limit of some versions of string theory. If space is actually 11-dimensional then the maximum temperature could even be as low as 10^17 K, attainable by the Large Hadron Collider. Or maybe infinite temperature wraps around to negative temperature and absolute hot is the same as absolute cold."
While it may well be that there is a maximum "energy density" for a particular space, it would not really be a true opposite to absolute zero. Absolute zero represents complete cessation of motion... a true opposite would be infinite motion (obviously not infinite velocity). Also, it seems quite possible that whatever upper limit exists at one particular time in one particular space may differ from another... either varying as the universe ages, with whatever gravitational field may exist locally, or at the very least in different universes that may exist. As such, while absolute zero is just that... absolute (in that no heat is no heat under all conceivable reference points), "absolute heat" almost certainly does not uniformly exist. I suppose another way to say is that if you plug absolute zero in as the value in a mathematical calculation, you will always get the same result, but there is no one value "absolute heat" corresponding, which can closely approach actually existing in our universe.
>All this, of course, is purely theoretical and can never be accomplished because it's hard to accelerate any particle infinitely. But according to relativistic physics, an infinite temperature can exist.
No, relativity requires the application of infinite energy to reach the infinite temperature, just like classic mechanics. For this very reason it's impossible to reach it - you don't have the source of infinite energy in our Universe (probably).
However, quantum mechanics has _another_ theoretical limit. I don't really know its precise reason, but this 'handwaving' argument holds: imagine that you have a particle with VERY large speed. The mass of this particle can be large enough to create a black hole. And it will immediately start to lose mass due to Hawking radiation, which will be directed along the path of the black hole (due to relativistic focusing) in the opposite direction (it'll look like black hole with retrorockets).
So it's not possible to reach the infinite speed because our Universe seems to have the _maximum_ allowed finite speed.