How much is the Cosmic Microwave Background Radiation redshifted?

Question

z=3

z=137

z=1100

z=4400

Answer 1

Using the best fit to all data, WMAP indicates that the redshift of decoupling occured at z=1089.

"Decoupling" is the term for the moment when the CMB as we know it was produced.

Answer 2

About z = 1089, based on WMAP measurements.

Answer 3

They are more nearer to the earth.

Using Doppler Shift Equation

Answer 4

I think the redshift can't be actually measured directly, since there are no emission lines in the spectrum, it's almost pure black body radiation. but fitting WMAP CMB data to cosmological models gives roughly z=1100.

Answer 5

Let's do a rough estimate:

The "effective temperature" of the CMB can be determined by looking at the entire spectrum (even if there are no lines in it) and finding the peak frequency -- which is in the microwave region of the spectrum (hence the name).

Using Wein's law, the effective temperature of the CMB can be found.  It is around 2.73 K

We know that it was emitted when the universe was around 3000 K  (which would correspond to a different peak frequency).

The shift would correspond to the ratio of the peak frequency then to the peak frequency now.  But we also know (from Wein's law) that the peak frequency and the temperature are linearly proportional.  Therefore, we can take the ratio of temperatures:

3000/2.73 = around 1100

Given the choices, I'd say we are close enough.