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(To the moderators, I had problems replying to original post and hence
am starting a new thread) Helbig---remove CLOTHES to reply) wrote: In article , Jonathan Thornburg writes: apparent aging rate consistent with the 1/(1+z) factor (where z is the redshift) expected in a homogeneous, isotropic, expanding universe. These measurements thus confirm the expansion hypothesis, I'd just like to point out that the 1/(1+z) factor would also be expected at least in some inhomogeneous anisotropic universes. In a universe like ours, which is almost homogeneous and isotropic, the expectation is certainly very close to 1/(1+z), certainly any discrepancy would be much less than the observational error. In other words, an observation of this factor is a robust result indicating that it arises from the expansion. This factor and the redshift are really the same thing. One can think of the frequency of electromagnetic radiation as a standard clock. Thus the original wavelength is 1/(1+z) as long as the observed wavelength by the same argument which applies to the supernovae. This is just the normal redshift. The interesting thing is that alternative theories which have some other mechanism for the normal redshift ("tired light" etc) usually don't predict time dilation in other clocks like a supernova light curve, whereas in the expanding-universe paradigm, one implies the other since they are really the same effect. It is also good to keep in mind that 1/(1+z) tells us the ratio of the size of the universe at the time the light was emitted to the size of the universe when the light was detected and the redshift measured. A clarification. Shouldn't the cosmological time dilation scale as (1+z) instead of 1/(1+z)? At least that's how I interpret the curve in : http://www.astro.ucla.edu/~wright/tiredlit.htm Larger the redshift, larger the time-dilation or width/length of the curve. Or am I misinterpreting this plot? Or is this new measurement not a direct measurement of width of curve and something else? Thanks |
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