If the universe was static Red shifts? The temperature of cosmic background radiatio

[JoeMK]

Imagine that the universe is static and not expanding.

Predict the observations that would be made in regards to:

a. Red shifts in glaxy spectra

b. The temperture of cosmic backgorund radiation

[swansont]

Imagine that the universe is static and not expanding.

Predict the observations that would be made in regards to:

a. Red shifts in glaxy spectra

b. The temperture of cosmic backgorund radiation

 

What are your thoughts?

 

Don't expect someone here to do your homework for you.

[JoeMK]

I know that the stars release large amounts of heat as they burn, but the temperature of the universe does not increase, as it is constantly expanding.

If the universe was static, then it'll obviously be much hotter, and most probably we wouldn't be alive.

I need help with the prediction, and as well as to connecting it with the idea of "Red Shifts" and "Cosmic Background Radiation"

 

Thanks

[swansont]

The CBR is ~2.7K, and that's because the universe is expanding - the expansion has shifted the wavelength. This is the leftover not-quite-uniform background leftover from the big bang, not from stars dumping energy into the universe. Galaxies also have redshifts because of the expansion - they are receding from us.

[ybk]

*ahm*

 

anyone?

[swansont]

*ahm*

 

anyone?

 

Anyone, what? It's homework, and the original poster has to put forth some effort.

 

If you have a specific conceptual question, ask away.

[ybk]

Anyone' date=' what? It's homework, and the original poster has to put forth some effort.

 

If you have a specific conceptual question, ask away.[/quote']

 

yup, agreed!

 

Well, I actually do I have a question.

 

Assuming the universe is static; wouldn't the actual temperature released reach a limit? Can something remain getting infinetly hot?

[swansont]

yup' date=' agreed!

 

Well, I actually do I have a question.

 

Assuming the universe is static; wouldn't the actual temperature released reach a limit? Can something remain getting infinetly hot?[/quote']

 

You're mixing up heat and temperature.

 

If you had a static volume, it would tend to equilibrate to a fixed temperature, if there's no place for energy to go. Then you have the question of what happens at the edge, unless it was closed in on itself.

[JoeMK]

A static universe' date=' one that is not expanding, cannot dispose of stellar energy. This kind of universe heats up over time [/quote']

 

so what would be ur prediction, if the universe was static would humans die in the near future, or it won't appreciably affect our lives on earth? What about the fate of the universe

[MetaFrizzics]

No, according to the theory of Conservation of Energy/momentum, one can expect energy to change form, and even become unavailable for useful work, or converted to mass, but not that temperature (or heat) could reach infinity. Temperature becomes a useful concept when the energy becomes almost uniformly distributed in space and also in form(! note this aspect), whereas heat is just EM energy in transit.

[JoeMK]

i really don't know how to connect red shifts and cosmicbackradiation with any predictions of a static universe

[tholan]

In a static, spatially infinite and eternal universe with an homogeneous distribution of eternal stars (or a constant homogeneous stellar population) the sum of the flux (the amount of energy that reaches a surface) of all stars at each point of the universe would be infinite. This is known as Olbers’ paradox. Note that stars (or the stellar population) are not eternal since the universe was not eternal in past. This fact suffices to solve Olbers’ paradox.

 

There is, however, another way to solve this paradox without the need of a temporally finite universe (or a finite lifetime of the homogeneous stellar population). If one considers a spatially infinite and eternal universe in which space expands (a de-Sitter model, with constant Hubble parameter leading to a strongly accelerated expansion), Olbers’ paradox is also solved. Any kind of radiation background due to the electromagnetic emission of stars (or whatever; CMB, etc.) would loss enough energy due to the strong redshift. In such a model the integral (sum of the flux due to all stars) would be finite, although there would be an contribution from an infinite number of stars!

 

In other expanding models this is not true. First, they are not eternal (the de-Sitter model is the only one without initial singularity). But, besides of this, one could consider a situation in a very far future in which a (non de-Sitter) universe is very old and the flux of lots of stars is reaching each point (assuming again a constant stellar population). In such a case, expansion is actually reshifting the radiation background, but this is not enough to “dilute” the total flux of energy, which would be increasing with time. This is because the Hubble parameter decreases with time in every model which is not de-Sitter.

[positron]

I found out that the red shift is a product of the doppler effect.

is CBR the result of the same phenomenon?

 

btw. i found the last post a bit difficult to interpret. could u explain it a bit plainer plz.

[JoeMK]

i found the last post a bit difficult to interpret. could u explain it a bit plainer plz.

 

co-sign!!

LOL

[W32.Blaster]

Retrograde motion?