Re: Rayleigh light scatter - application to extra-galactic red shifts?
- From: "Doug" <docorey47@xxxxxxxxx>
- Date: 29 Sep 2005 06:50:26 -0700
To both reply #2&3, within the article referenced by reply #3 - "This
is most correctly called the Tyndall effect, but it is more commonly
known to physicists as Rayleigh scattering--after Lord Rayleigh, who
studied it in more detail a few years later. He showed that the amount
of light scattered is inversely proportional to the fourth power of
wavelength for sufficiently small particles. It follows that blue light
is scattered more than red light by a factor of (700/400)4 ~= 10.
Tyndall and Rayleigh thought that the blue colour of the sky must be
due to small particles of dust and droplets of water vapour in the
atmosphere. Even today, people sometimes incorrectly say that this is
the case. Later scientists realised that if this were true, there would
be more variation of sky colour with humidity or haze conditions than
was actually observed, so they supposed correctly that the molecules of
oxygen and nitrogen in the air are sufficient to account for the
scattering. The case was finally settled by Einstein in 1911, who
calculated the detailed formula for the scattering of light from
molecules; and this was found to be in agreement with experiment. He
was even able to use the calculation as a further verification of
Avogadro's number when compared with observation. The molecules are
able to scatter light because the electromagnetic field of the light
waves induces electric dipole moments in the molecules."
z = H * r / c where z is the redshift, H is the so-called Hubble
constant; r is the distance to the galaxy and c is the speed of light.
z = (Observed wavelength - Rest wavelength) / (Rest wavelength)
z-Total = z-Doppler + z-Gravity + z-Hubble_constant
The observer sees a redshift if z is positive, a blueshift if z is
negative.
Current thinking favors the Doppler explanation.
Since inception, controversy has existed about the origin of the
cosmological redshift - if due to Doppler, gravitational or other
unknown effects.
For example NASA in 1999 commented about the accelerating universe
expansion - "This measurement was made by looking at distant
supernovae. If distant supernovae are different in brightness than
nearby supernovae (eg if there is more dust dimming the light than we
think) then the measurement could be wrong. However, most astronomers
think that the measurements are strong."
According to Lineweaver and Davis in Scientific American 2005 March -
"Astronomers have observed about 1,000 galaxies with redshifts larger
than 1.5 ... receding from us faster than the speed of light" which
they explain as "Instead the space between the galaxies and us is
expanding."
In the local galactic cluster with so many blue shifted objects does
this mean that the space between galaxies is shrinking?
Should the interpretation of the red shift be reevaluated?
.
- References:
- Re: Rayleigh light scatter - application to extra-galactic red shifts?
- From: Ben Rudiak-Gould
- Re: Rayleigh light scatter - application to extra-galactic red shifts?
- Prev by Date: Space is clearly something not nothing
- Next by Date: Re: Another Red Shift Question
- Previous by thread: Re: Rayleigh light scatter - application to extra-galactic red shifts?
- Next by thread: Acceleration of the Universe as Acceleration of Probable Influence 11: Mean-Shifting
- Index(es):
Relevant Pages
|
