----- Original Message ----- From: "Kevin Street" <[EMAIL PROTECTED]> To: "'Killer Bs Discussion'" <[email protected]> Sent: Friday, August 12, 2005 5:49 PM Subject: RE: Physics question
> A very good point, but I think The Fool is talking about the velocity (or > maybe more interestingly, the momentum) with regard to the reference frame > of the place from which it was launched. i.e.: most likely Earth. By > reducing the momentum to zero, you know exactly how much momentum the craft > has, which then introduces the uncertainty in the spacecraft's position. Well, our instruments are in an accelerating reference frame, so it is not clear that something thats, say, 200,000 miles away as it approaches zero velocity with respect to the earth's center of mass can have it's velocity measured all that easy. If you think of any measurement technique, you quickly intereact with the spacecraft enough to ensure that dpdx is greater than h-bar. > But I think there's one major problem here, beside the definitional problem > Warren mentioned: > > The thing is, Heisenberg's Uncertainty Principles are really meant to > describe quantum mechanical or microscopic phenomena. Look at the equation: > > [(Uncertainty in momentum) times (uncertainty in position)] is greater than > or equal to [(Planck's Constant) divided by (two times Pi)] > > (dp X dX) >= (h/2Pi) > > Planck's Constant is incredibly tiny, so the delta x of any macroscopic > object would also be very small. > > And if delta p was zero, you'd end up with a singularity on the right hand > side of the equation when trying to determine delta x, which is impossible. Actually, it means that as dp-> 0, dx-> infinity...which is what the Fool is thinking about. The real thing we can look at is the magnitude of dp and dx that we are talking about. h-bar is, roughly, 10^-34 J-s or 10^-34 kg m^2/s. Let's assume we have a 100 kg spacecraft. That gives us, dv*dx = 10^-36 m*(m/s). For the indeterminacy in the position to be 1 km, then the velocity would have to be restricted to within 10^-37 m/s. Just thinking about the quantum variation in all the electrons, we can eliminate this possibility. IMHO, the Fool's idea is a good example of the problem of trying to force a QM peg into a classical hole. Dan M. _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
