Speed of light? [was Re: GPL vs BSD Licence]

[Mark Murray]

Marc Ramirez writes:
> > IANAPhysicist but, isn't the speed of light in a vacuum constant? Well, it
> > may be being actively debated by cosmologists attempting to explain the
> > origins of the universe; but, VSL aside... the speed of light is
> > 2.998something x10^8 m/s in vacuum.
> >
> > Sorry, but this is chat, and I figured I ask.
> 
> Yes, it is a fixed speed in a vacuum; it gets redshifted in a graviational field.

Not quite. The Speed Of Light in a Vacuum Constant is constant in all inertial 
frames of reference, and is exactly 299792458 m/s. In other media (air, water 
etc, it may be slower than this. It is never faster.

If the originator of the light is moving away from you, atomic spectra in the 
light are shifted towards the red end of the spectrum ("redshift"). If the 
originator of the light is moving towards you, atomic spectra are blueshifted.
This is called the Doppler shift.

Gravity may bend light beams.

M
--
Mark Murray
iumop ap!sdn w,I idlaH