How does the Hubble Telescope see back in time?
It has to do with how fast the light travels from those stars and other things. Since those things are extremely far away from the telescope the light that’s being emitted from those things has to travel from there to the telescope. That can take many years for the light to reach the telescope and in those years things in that object can change a lot. So when you look into the sky next you’re looking into the past and most of those stars that you see are gone by now. That’s the same for the telescope