I’ve always wondered how astronomers can actually observe galaxies that are millions or even billions of light-years away. What exactly are we seeing when we look at them?
And when scientists say there are hundreds of billions, or possibly trillions, of galaxies in the observable universe, how do they know that if we obviously haven’t seen and counted every single one?
By pointing a telescope at them and looking. You can see some of the larger ones through a cheap home telescope for a couple hundred dollars.