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 motivates non calling it light like. That is, a zero vector is zero in any basis and retains this property on any parallel transport.
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 any sequence of parallel transports, it remains nonzero. This precludes the possibility mentioned in the OP.
Ah yes, bananas are highly radioactive compared to batteries. Granite counter tops can dwarf any possible exposure near nuclear reactors - enough to at least give me pause (from accumulated radon in a tightly sealed house).
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 differences in relativity (special or general) are differences between clocks, neither of which is considered wrong. Consider, for comparison, odometers on a...
There is a term in relativity for the notion of change of distance per some inertial frame divided by proper time per some observer (timelike world line). It is called celerity, and it has no upper bound in special relativity (it can be arbitrarily superliminal). It is a completely different...
Bing is a search engine. It finds nonsense just as easily as good science. Actually, it is skewed towards bad science, since there is more of this on the internet, so its weighting ends up favoring bad science.
The above statements are a mixture of just wrong and totally meaningless.
Just to clarify relations between homogeneity and isotropy:
- isotropy about a point obviously does not imply homogeneity
- isotropy everywhere (about all point) implies homogeneity
- homogeneity does not imply isotropy (there can be the 'same' preferred direction at every point...
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).
Note, this is exactly what @Bandersnatch explained in post: post #5
Yes, but I was thinking of spin angular momentum rather than orbital. The latter is frame dependent, the former is not ( in magnitude - it is in direction, obviously). Cosmic rays being primarily fermions would have intrinsic angular momentum. A spinning pulsar with huge peculiar velocity would...
We don't seem to be communicating. Assuming a stationary system with vaccuum beyond some surface, the way you measure effective mass is to look at behavior of test bodies at a large distance. What determines the motion of these test bodies is Weyl curvature (since that's all there is in a...
It is still a measure of curvature. The Weyl curvature at large distance from the system, normalized by the distance, measures its Komar mass. I am assuming the system is isolated in empty space.