[ExI] Faster than light??
anders at aleph.se
Wed Sep 28 09:45:20 UTC 2011
Stefano Vaj wrote:
> 2011/9/27 Tomaz Kristan <protokol2020 at gmail.com>:
>> B - c is a little higher and photons are a bit slower than c. Neutrinos
>> travel with a velocity between those two. Minor revisions, something like
>> Anders seems to think.
> I am confused here. Particles with a mass travelling faster than
> electromagnetic or gravitational waves?
Actually, this ought to be observationally ruled out for all *charged*
faster-than-photon particles, because of Cherenkov radiation. The
Frank-Tamm formula produces a divergent result since in vaccum the speed
will be greater than the speed of light for the medium for all
velocities. So presumably you cannot accelerate a charged particle
beyond photon speed because of energy losses. Cute.
Neutrinos are fine, of course.
A universe with a vacuum index of refraction slightly above 1 is not
really problematic for SR, it would just look odd (there is an exercise
in Rindler's "Essential Relativity" about this).
However, if you could move particles with mass faster than gravity waves
then you would presumably get an analogous divergence of gravitational
Cherenkov radiation ("gravity shockwaves"). This likely precludes
neutrinos from going faster than the speed of gravity waves, given that
they have been observed to have mass.
Future of Humanity Institute
James Martin 21st Century School
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