From: utzoo!decvax!harpo!seismo!hao!hplabs!sri-unix!larson
Newsgroups: net.space
Title: Re: Einstein's Universe?! - (nf)
Article-I.D.: sri-unix.5343
Posted: Wed Mar  9 07:26:30 1983
Received: Fri Mar 11 21:02:59 1983

#R:ihldt:-131300:sri-unix:13400003:000:1196
sri-unix!larson    Mar  7 00:25:00 1983

  From "Physics" by Resnick & Halliday, section 20-7:

  There are differences, however, in the Doppler effect formula for light
and for sound.  In sound is is not just the relative motion of source and
observer that determines the frequency change.  In fact, as we have seen,
even when the relative motion is the same, we otain different quantative
results, depending on whether the source of the observer is moving.  This
difference occurs because Vo and Vs are measured relative to the medium
in which the sound wav is propagated and because this medium determines
the wave speed.  Light, however, does not require a material medium for
its transmission, and the speed of light relative to the source or the
observer is always the same value c, regardless of the motion of those
bodies relative to each other.  This is a basic postulate of the special
theory of relativity.  Hence, for light only the relative motion of the
source and observer can lead to physical changes, there being no material
medium to use as a reference frame.

  I cannot think of any way to make it more clear without including
the formulas given in the section, and they are just more than I wanted
to type in.
	Alan