Posted: Dec 15, 2011 9:33 pm
by andrewk
My initial response to the OP is that, from a quantum mechanical perspective, the question dissolves into meaninglessness once we are talking about small enough measures. What, for instance, can be meant by "nothing physical would be able to fit inside of [the smallest volume]", when anything that small can only be described in terms of a wave function that, in the absence of infinite potential barriers (which we don't believe exist), extends throughout all of space. Indeed, even for macro objects like a pea inside a sealed tin can, there is a non-zero probability that the pea may be anywhere else in the universe, outside the tin can, so we could say the pea doesn't "fit in the can" because its wave function is not confined to the can, in the same way as we would for the infinitesimally small volume being considered.

I've never read any loop quantum gravity, but Smolin is a reputable physicist, so I can only assume that the reason he writes about the possible existence of a minimum volume is that perhaps loop quantum gravity overrides quantum mechanics under some circumstances. My understanding is that loop quantum gravity is a highly speculative and entirely hypothetical field at present, whereas QM is one of the most highly experimentally verified theories around. That is not to say that LQG may not be right, just that it's speculative.