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army1987 comments on Welcome to Less Wrong! (2010-2011) - Less Wrong
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It could be like that something moving at 3/4 c will have, on each Planck time, a 3/4 chance of moving of one Planck length, and a 1/4 chance of not moving at all. But that's how I understand it from a computer scientist point of view, it may not be how physicists really see it.
But I think the core reason is that since no signal can spread faster than c, no signal can cross more than one Planck length over a Planck time, so a difference of less than a Planck time can never be detected. Since it cannot be detected, since there is no experimental setting that would differ if something happened a fraction of Planck time earlier, the question has no meaning.
If time really is discreet or continuous doesn't have any meaning, if no possible experiments can tell the two apart.
Of course, given any experiment, spacetime being discrete on a sufficiently small scale couldn't be detected, but given any scale, a sufficiently precise experiment could tell if spacetime is discrete at that scale. And there's evidence that spacetime is likely not discrete at Planck scale (otherwise sufficiently-high-energy gamma rays would have a nontrivial dependency of speed on energy, which is not what we see in gamma-ray bursts). See http://www.nature.com/nature/journal/v462/n7271/edsumm/e091119-06.html
Thanks for the post and for the very helpful link.