On 6/17/2018 12:05 AM, Bruce Kellett wrote:
From: *Lawrence Crowell* <[email protected]
<mailto:[email protected]>>
On Friday, June 15, 2018 at 11:55:17 PM UTC-5, Brent wrote:
On 6/15/2018 6:46 AM, Lawrence Crowell wrote:
I might be wrong here, but my point is that energy occurs in
discrete eigenvalues and we never measure energy in between.
With spin for instance it occurs in any direction and is
determined by the orientation of a magnetic field I set. I do
not tune some variable to get the energy spectrum of an atom.
There is something odd about energy in both quantum mechanics
and relativity.
But the energy of photons is a continuum.
Brent
I am not sure that changes the argument. Photons are often emitted
by systems with discrete energy levels or resonance scattering peaks.
Of course it makes a difference! I am amazed at the depth of the
confusion that seems to surround something as fundamental as
einselection of a preferred basis.
The fact that energy spectra of atoms and the like are discrete does
not change the fact that energy eigenvalues are a continuous set of
delta functions on the real line. And generally, when one is measuring
atomic spectra one determines energies by the deviation occasioned by
a prism or diffraction grating. In other words, one actually measures
a position on a screen, or a wavelength, which is also a position
measurement.
Yes, it's interesting to consider what measurements are /not/ position
measurements. We can distinguish colors, so is that a direct energy
measurment. And we have calorimeters. Is there a direct measurement of
momentum?
Brent
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