One way is to take the measurements in a binary system. From the spectral type
of the component stars, an estimate of their distance, and their orbital period,
all measurable through telescopes and some inferring, you can get the pairs
motion around each other and through space, at least in the line of sight. From
this you can eliminate causes of red shift due to motion, eliminate them, and
uncover other red shift effects.
This was, in fact, how gravitationally induced red shift was measured for the
first time, using the white dwarf companion of Sirius, I believe, if not the one
around Procyon, but I believe it was Sirius. The period, mass, and the pair's
mutual motion through space are measurable or can be calculated from the
observed. From this, all red shifts due to motion can be eliminated. Then
because the companion has a high surface gravity, it can produce a gravitational
red shift, which was what was left when the other causes were eliminated, and it
matched what Einstein predicted for the mass of the companion.
--
Sincerely,
--- Dave
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It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington
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"md" not given to avoid spam wrote in message
...
"Sam Wormley" wrote in message
news:exPPd.66163$EG1.51167@attbi_s53...
md wrote:
relativity predicts a red-shift for light traveling "up" in a gravity
field.
Doppler predicts a red-shift for light emitted from an object moving away
from us.
How can we distinguish the two? When we measure the red-shift of a distant
object, how can
we
conclude that it moves away from us? It might also be that it is not moving
away, but it is
very heavy instead?
Relativistic Redshift
http://scienceworld.wolfram.com/phys...cRedshift.html
Gravitational Redshift
http://scienceworld.wolfram.com/phys...lRedshift.html
Doppler Effect
http://scienceworld.wolfram.com/phys...lerEffect.html
thanks for the formulae, but they did not really answer my question.
These three sources of redshift can usually be sorted by the context
of other data made in the measurement process.
how?
--
md
10" LX200GPS-SMT
ETX105
www.xs4all.nl/~martlian