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PAllen's latest activity
P
PAllen
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Can the expansion of the Universe reduce the energy of a photon to 0?
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But then you would have light that had no energy or momentum ever ( at any event on its world line , or any basis choice). I guess that...
Today, 11:24 AM
P
PAllen
replied to the thread
I
Can the expansion of the Universe reduce the energy of a photon to 0?
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Ok, but the statement remains that if a null vector is not a zero vector per some basis at some event, then for any choice of basis, and...
Today, 10:59 AM
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PAllen
replied to the thread
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Do Magnets Emit Harmful Radiation?
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Ah yes, bananas are highly radioactive compared to batteries. Granite counter tops can dwarf any possible exposure near nuclear reactors...
Apr 15, 2024
P
PAllen
replied to the thread
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Battery life on VERY fast moving object
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Nothing at all ever impacts the time a clock keeps (if it is an "ideal clock"). This is referred to as the clock hypothesis. All clock...
Apr 12, 2024
P
PAllen
replied to the thread
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Battery life on VERY fast moving object
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There is a term in relativity for the notion of change of distance per some inertial frame divided by proper time per some observer...
Apr 12, 2024
P
PAllen
replied to the thread
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Movement vs expansion in space
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Yes, this is homogeneous but nowhere isotropic.
Apr 6, 2024
P
PAllen
replied to the thread
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Battery life on VERY fast moving object
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Bing is a search engine. It finds nonsense just as easily as good science. Actually, it is skewed towards bad science, since there is...
Apr 5, 2024
P
PAllen
replied to the thread
A
Movement vs expansion in space
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Just to clarify relations between homogeneity and isotropy: - isotropy about a point obviously does not imply homogeneity -...
Apr 5, 2024
P
PAllen
replied to the thread
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Battery life on VERY fast moving object
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My last math course was in 1973 and I am a couple of decades older than you.
Apr 5, 2024
P
PAllen
replied to the thread
I
Is there an equivalent "redshift" for cosmic rays due to expansion?
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Yes, when it reached us it would have much lower peculiar velocity than it had when it was ejected somehow from a galaxy (for example)...
Apr 5, 2024
P
PAllen
replied to the thread
I
Is there an equivalent "redshift" for cosmic rays due to expansion?
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This would be a highly bound system, so expansion would be irrelevant.
Apr 5, 2024
P
PAllen
replied to the thread
I
Is there an equivalent "redshift" for cosmic rays due to expansion?
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Yes, but I was thinking of spin angular momentum rather than orbital. The latter is frame dependent, the former is not ( in magnitude -...
Apr 5, 2024
P
PAllen
replied to the thread
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Is there an equivalent "redshift" for cosmic rays due to expansion?
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The magnitude of angular momentum is invariant like mass of a particle. Neither gets red shifted.
Apr 4, 2024
P
PAllen
replied to the thread
I
Does potential energy curve spacetime?
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We don't seem to be communicating. Assuming a stationary system with vaccuum beyond some surface, the way you measure effective mass is...
Apr 4, 2024
P
PAllen
replied to the thread
I
Does potential energy curve spacetime?
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It is still a measure of curvature. The Weyl curvature at large distance from the system, normalized by the distance, measures its Komar...
Apr 3, 2024
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