Is Redshift an Accurate Indicator of the Universe's Expansion Rate?

[_Mayday_]

Hey!

I have a few questions regarding redshift. Firstly are there example of a shift in frequency of light other than the one seen in redshift or blueshift. I mean are there experiments that have been conducted that prove that this noted shift to the red end of the spectrum mean that something is moving away relative to an observer?

Secondly, would I be correct in saying that the noted redshift now is actually, and indication of the rate of expansion quite a while back, taking into account the speed that the light takes to reach the observer. How do we know that the rate of expansion has decreased or infact it has start to contract again? There must be a way to calculate the rate of expansion now.

Thanks for any help!

_Mayday_

 

[Kittel Knight]

Maybe this can help:

http://archive.ncsa.uiuc.edu/Cyberia/Bima/doppler.html"
http://en.wikipedia.org/wiki/Redshift"
https://www.physicsforums.com/showthread.php?t=78645"
https://www.physicsforums.com/showthread.php?p=1748768"

 

[sir-pinski]

Hey there

To answer your first question, yes, there are other examples of frequency shifts in light besides redshift and blueshift. One example is gravitational redshift, which occurs when light is emitted from a strong gravitational field, such as near a black hole. The light's frequency appears to decrease as it struggles to escape the gravitational pull. Another example is the Doppler effect, which causes a shift in frequency as a result of the relative motion between the source of light and the observer. This is the same principle behind redshift and blueshift, but in the case of the Doppler effect, the motion is not necessarily due to the expansion of the universe.

As for your second question, you are correct in saying that the redshift we observe now is an indication of the rate of expansion in the past. This is because light takes time to travel through space, so the light we see from distant galaxies is actually from the past. By studying the redshift of light from different galaxies, we can estimate the rate of expansion at different points in time. As for how we know if the rate of expansion has changed or if the universe will eventually contract, this is an ongoing area of research in cosmology. Scientists use various methods, such as measuring the brightness and distance of supernovae, to estimate the current rate of expansion and how it may change in the future. However, the exact nature of the universe's expansion and potential contraction is still a subject of debate and further study.

I hope this helps answer your questions!