Red-shift help

Red shift is where light waves coming from distant galaxies are shifted to the red end of the spectrum, so if you compared the absorption spectra (black lines) of a near galaxy and far galaxy the far galaxy's black lines would be far more shifted to the red end and closer galaxies will have the black line closer to the absorption spectra of our galaxy.

This is because further away galaxies are moving at higher speeds than ones closer to us. Further to the red side of the spectrum the faster it is moving away from us. So by this you are able to tell that the universe is always expanding.

I hope this helped!

Thank you! What exactly is meant by asorption spectra?

So when you shine line through a disc with a slit it diffracts into a spectrum (similar to a prism), and this can be used in telescopes so when you point it at a Sun the spectrum will have black lines on. The black lines are basically what the Sun is absorbing in its atmosphere. By this you can tell what a Sun is made out of (absorption spectra).

This is due to spectroscopy when you heat a material it gives of a specific light (if you do edexcel this is in c2). And then that light on the spectrum codes for a specific element