What is red shift? What is the difference between cosmic background radiation and red shift?

Cosmic background radiation is stuff left over from the Big Bang just generating a bunch of white noise out in space.

Red shift has to do with the Dopplar effect. You know when an ambulance is driving past and your ears pick up a shift in tone? As it's moving toward you, the sound waves are getting more compressed which is why they sound like they're getting louder, and and it's moving away the sound gets quieter because the sound waves are getting stretched out.

The same thing happens to light. When an object is moving towards you, the light waves get more compressed so the light shifts towards the blue end of the spectrum, and when it's moving away the light waves get stretched out and they shift towards the red end of the spectrum.

Redshift is the change in wavelength of radiation caused by the expansion of the Universe.

Redshift can be any number between 0 and infinite.

The cosmic background radiation is actual photon radiation that fills all of space. Currently, it is at radio wavelengths. It is the most highly redshifted photons than can be observed, with a redshift around 1000. So originally, the cosmic background radiation had a wavelenth was 1000 times smaller, which is to say, visible light.

'Red shift' is the apparent change in wavelength of light coming from a star (or other object) which is receding from the observer. It's 'kinda like' the Doppler shift that happens as an automobile that's blowing it's horn passes by you. The frequency appears higher as it approaches and drops as it recedes. (And yes, there is also a 'Blue Shift' that is seen in objects that are headed towards us ☺)

Cosmic background is believed to be the remnant 'echo' of the Big Bang.

HTH,

Doug