Re:Why scientists are redefining the kilogram
by nonbel on Thursday October 26, 2017 @09:02AM
(#15558393)
>"we can view the past for many of these constants (gravity, for example) by looking in telescopes to places many millions or billions of light years away- and what we see reflects gravity and the speed of light being the same as it was then."
Isn't this circular? The concept of a light year (and the determination of how far you are looking into the past, etc) assumes a constant speed of light.
Re:Why scientists are redefining the kilogram
by shagie on Thursday October 26, 2017 @10:28AM
(#15559077)
There are also phenomena such as the natural fission reactor at Oklo that demonstrates that the fine structure constant hasn’t changed over the past 2b years.
Part of the definition of this constant is c and pi. It is very hard to alter one constant without altering another.
https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...
Re:Why scientists are redefining the kilogram
by fixermark on Thursday October 26, 2017 @10:37AM
(#15559168)
It's circular-ish, but we also see alignment in observable cosmic phenomena that strongly suggest the constants hold (such as the periodicity of pulsars being related to how fast they are moving relative to us, which we can measure via redshift).
Also, we can view the past for many of these constants (gravity, for example) by looking in telescopes to places many millions or billions of light years away- and what we see reflects gravity and the speed of light being the same as it was then. Why would it change now? Occam's Razor applies.