Date: Tue, 2 Nov 2004 14:12:36 -0500 From: Marc Ramirez <marc.ramirez@bluecirclesoft.com> To: Mark Murray <mark@grondar.org> Cc: freebsd-chat@freebsd.org Subject: Re: Speed of light? [was Re: GPL vs BSD Licence] Message-ID: <200411021412.44009.marc.ramirez@bluecirclesoft.com> In-Reply-To: <200411021821.iA2ILI3N092806@grovel.grondar.org> References: <200411021821.iA2ILI3N092806@grovel.grondar.org>
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On Tuesday 02 November 2004 01:21 pm, Mark Murray wrote:
> Marc Ramirez writes:
> > > IANAPhysicist but, isn't the speed of light in a vacuum constant? Wel=
l,
> > > 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.
Again, I will preface by saying I am a professional doofus and amateur=20
windbag.
> 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.
True. More precisely, the slowing of light within materials can be derived=
=20
from first principles by assuming a fixed SoL, c, and factoring in the time=
=20
involved in absorption/re-emission of photons by the molecules.
> 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.
All true.
> Gravity may bend light beams.
More precisely, gravity is what we call the curvature of spacetime. Light=
=20
always heads in the straighest possible line, but in a curved spacetime... =
=20
Also, if light is emitted in an area of lower potential and is absorbed in =
an=20
area of higher potential (e.g., from Sun to Earth) it will be redshifted.=20
Other way around, it will be blueshifted. If you are using the frequency of=
=20
light as a clock (and you basically have no other choice), you will notice=
=20
this effect as "time moving more slowly around massive bodies."
Marc.
=2D-=20
Marc Ramirez
Blue Circle Software Corporation
513-688-1070 (main)
513-382-1270 (direct)
http://www.bluecirclesoft.com
http://www.mrami.com (personal)
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