Date: 02 Nov 2004 19:20:45 -0500 From: Mike Jeays <Mike.Jeays@rogers.com> To: Marc Ramirez <marc.ramirez@bluecirclesoft.com> Cc: Mark Murray <mark@grondar.org> Subject: Re: Speed of light? [was Re: GPL vs BSD Licence] Message-ID: <1099441245.761.6.camel@chaucer.jeays.ca> In-Reply-To: <200411021412.44009.marc.ramirez@bluecirclesoft.com> References: <200411021821.iA2ILI3N092806@grovel.grondar.org> <200411021412.44009.marc.ramirez@bluecirclesoft.com>
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On Tue, 2004-11-02 at 14:12, Marc Ramirez wrote:
> 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? 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.
>
> Again, I will preface by saying I am a professional doofus and amateur
> 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
> from first principles by assuming a fixed SoL, c, and factoring in the time
> 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
> always heads in the straighest possible line, but in a curved spacetime...
> Also, if light is emitted in an area of lower potential and is absorbed in an
> area of higher potential (e.g., from Sun to Earth) it will be redshifted.
> Other way around, it will be blueshifted. If you are using the frequency of
> light as a clock (and you basically have no other choice), you will notice
> this effect as "time moving more slowly around massive bodies."
>
> Marc.
Doesn't this equate to defining the speed of light as constant, and then
adjusting the metre and second appropriately? I thought the constancy
of the speed of light was a basic assumption taken by Einstein; the
slowing of time and reduction of lengths of moving objects, or those in
a gravitational field are a consequence.
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