(Sorry somehow managed to send this to the old list number. Stupid Apple Mail.)
> On Dec 11, 2016, at 12:48 PM, Benjamin Udell <baud...@gmail.com > <mailto:baud...@gmail.com>> wrote: > > According to Wikipedia, the Planck length is, in principle, within a factor > of 10, the shortest measurable length – and no theoretically known > improvement in measurement instruments could change that. But some physicists > have found that that's not quite as much of a barrier as it may seem to be. It ends up being a bit more complex than that. It really depends upon the system in question and what you are measuring. There’s also the debate about whether this is epistemological or “real” (although when people use that term they mean traditional realism not Peirce’s realism which tends to blur the distinction). BTW - a better discussion of Planck length is probably stack exchange which gets into many of the nuances (both physical and philosophical). It’s almost always a better source than Wikipedia on these topics. http://physics.stackexchange.com/questions/185939/is-the-planck-length-the-smallest-length-that-exists-in-the-universe-or-is-it-th <http://physics.stackexchange.com/questions/185939/is-the-planck-length-the-smallest-length-that-exists-in-the-universe-or-is-it-th> The short answer is that gravitational effects become dominate below the Planck length we assume. Since we don’t have a theory of quantum gravity this region is more or less ‘no man’s land’ unless one tries to apply string theory or the like. Beyond that it’s just a scale factor and we probably shouldn’t say much beyond that. (Again unless one is doing theoretical work in quantum gravity - but that has its own problems) Typically in practical QM problems we assume a classical continuous substantial spacetime and ignore all these issues. In that case we’re just worried about what we can measure in principle about *that* system from the math. A few other useful ones: http://physics.stackexchange.com/questions/9720/does-the-planck-scale-imply-that-spacetime-is-discrete <http://physics.stackexchange.com/questions/9720/does-the-planck-scale-imply-that-spacetime-is-discrete> http://physics.stackexchange.com/questions/28720/how-to-get-planck-length <http://physics.stackexchange.com/questions/28720/how-to-get-planck-length>
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