Question about theory of expanding universe

[CuriousBobby]

New to cosmology, please go easy on me. ;)

1. REFRACTIVE INDEX

"It is generally accepted that the speed of light in a vacuum is not dependent on its frequency (color)."

http://accessscience.com/studycenter.aspx?main=17&questionID=3781

2. IS SPACE A VACUUM?

"Outer space (often simply called space) is the void that exists beyond any celestial body including the Earth. It is not completely empty (i.e. a perfect vacuum), but contains a low density of particles, predominantly hydrogen plasma, as well as electromagnetic radiation, magnetic fields, and neutrinos. Theoretically, it also contains dark matter and dark energy."

http://en.wikipedia.org/wiki/Outer_space

3. THE COLOUR OF STARS

"The colour of a star is primarily a function of its effective temperature."

http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html

4. REDSHIFT: THE THEORY OF AN EXPANDING UNIVERSE

"The light from most objects in the Universe is redshifted as seen from the Earth. Only a few objects, mainly local objects like planets and some nearby stars, are blueshifted. This is because our Universe is expanding."

http://coolcosmos.ipac.caltech.edu/cosmic_classroom/cosmic_reference/redshift.html

MY QUESTION

Could redshift be explained as low-burn stars (stars with a lower temporature which are red in colour) whose light is traveling at a different speed to light from neighbouring high-burn stars, rather than indicative of an expanding universe?

 

[bapowell]

The speed of light is independent of its frequency. This is the core of Einstein's Special Theory of Relativity.

 

[Nabeshin]

The reason the speed of light is lower in a medium is because it interacts with the medium, i.e. light traveling through a glass window interacts with the glass molecules.

For interstellar space, the medium is so dilute that there cannot be any significant interaction, i.e significant slowing of the light.

So no, you cannot explain the redshift like this.

(Note even if the above were false and there was a significant effect due to the ISM, it would not fit observations of redshift.)

 

[Drakkith]

The key to the redshift, is that the further away the object, the MORE it is redshifted compared to similar objects that are closer. IE if you look at similar galaxies, one that is 5 billion LY away is less redshifted than one that is 10 billion LY away. The furthest galaxies we have been able to see so far, are redshifted almost out of the visible spectrum. (According to my new book on space, which circles a galaxy in the Hubble ultra deep field that is very very red and says that it is partly in the infrared range.)

 

[Chalnoth]

Could redshift be explained as low-burn stars (stars with a lower temporature which are red in colour) whose light is traveling at a different speed to light from neighbouring high-burn stars, rather than indicative of an expanding universe?

Well, the thing here is that redshift (which can be thought of as measuring how fast things are moving away from us) is tightly correlated with distance (typically measured by either how bright it looks compared to how bright the object is at the source, or how big it looks compared to how big it is).

So any alternative explanation for redshift besides it being related to the expansion of the universe (which we see as an increasing recession velocity with distance) will have to also explain why things which are further away are, on average, more redshifted.

I'd also like to mention that we usually measure the redshift not by looking at the overall redenning of the light, but instead by looking at the redenning of specific, bright emission lines.

 

[CuriousBobby]

Thank you all very much for taking the time to respond.