----- Original Message ----- From: "Warren Ockrassa" <[EMAIL PROTECTED]> To: "Killer Bs Discussion" <brin-l@mccmedia.com> Sent: Thursday, March 03, 2005 11:25 PM Subject: Re: quantum darwin?
> > > Also, its > > worth noting, that there have been experimental confirmation of > > macroscopic > > quantum states....not just macroscopic effects. > > Do you mean the electron-slit thing, or are you referring to something > else here? > Definitely something else. The two slit experiments were, goodness, 80 years ago. A great deal has been done since then. I was specifically thinking about Bose-Einstein condensates. An article on this is given at: http://www.strangehorizons.com/2001/20011210/bose-einstein.shtml The essay is a bit pop-scienceish, so some of the stuff shouldn't be taken literally....but it's better than most, the discussion of intrinsic spin, for example, is a pretty good layman's description. Anyways, a relevant quote, referring to my point is: <quote> One of the problems physicists run into when teaching quantum mechanics is that the principles are just counter-intuitive. They're hard to visualize. But videos of BEC blobs several millimeters across show wave-particle duality at a level we can comprehend easily. We can watch something that acts like an atom, at a size we could hold in our hands. MIT researchers have produced visible interference fringe patterns from sodium BECs, demonstrating quantum mechanics effects on the macroscale. That alone is worth notice. <end quote> The important thing to take away from this quote is the size of the BEC, several millimeters. That is definitely macroscopic, it's a size that you see on a grade student's ruler. The most important work on the foundations of QM, until perhaps the most recent work on a QM theory of QM measurement, has been Bell-Wigner. Einstein, Podansky, and Rosen showed in the '30s that QM predicted the existence of space-like correlations. In the '60s, Bell and Wigner showed that these correlations could not be the result of local hidden variables. The only way for these correlations to be supported by a more deterministic set of variables is if these variables either went faster than light in some ultimate fixed reference frame (which we might as well call the aether), or if they went backwards in time. It was always possible, of course, that these spacelike correlations did not occur. We could see QM break down in that regime....no one thought it likely, but it was possible. In the last 20 years or so, a number of experiments have been done with spacelike correlations. I've not kept up with the latest experiments, but I have read papers detailing spacelike correlations over 10 miles, spacelike correlations without inequalities, and spacelike correlations of molecules. This aspect of QM has been rigorously verified. Looking at the web, experiments are now ongoing to have superpositions of macroscopic currents, using a Josephine junction. It is always possible that QM will break down at this point, and that there is exciting new physics somewhere around mesoscopic physics. I would rate it as improbable, because one would have thought that the BEC work would not have followed theoretical expectations if some a macroscopic effect existed. Yet, as an experimentalist, I strongly support pushing things as far as we can go in hopes of finding new physics. Finally, I'll address in another post a common fallacy concerning the ways that old theories are supplanted by newer theories (i.e. Classical Electrodynamics being replaced by QED). I've seen that misconception lead to a lot of difficulties for "alternate thinkers" on sci.physics, alt.sci.physics, etc. Dan M. Dan M. _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
