From: *Brent Meeker* <meeke...@verizon.net <mailto:meeke...@verizon.net>>
On 6/17/2018 12:05 AM, Bruce Kellett wrote:
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?
It has been suggested that all measurements ultimately boil down to
position measurements. Colour vision is the result of distinct
receptors in the retina that are at different positions, and the light
from distant objects is focused at different positions by the lens in
the eye. I don't know enough about the physics of calorimeters as used
in HEP to comment here. But if temperature changes are measured by
bimetals or strain gauges, position comes into it in an essential way. I
don't know of any direct, non-position-dependent, measure of momentum.
It is an interesting question, but somewhat beside the point of
determining why our current classical perceptions of position correspond
to the stable quantum eigenvalues -- an evolutionary explanation might
explain the correspondence, but not why classical position is the way it is.
Bruce
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