It puts into perspective just how much our understanding of the universe has grown in the last 100 years. Of course, this is true for all kinds of sciences, but

It puts into perspective just how much our understanding of the universe has grown in the last 100 years. Of course, this is true for all kinds of sciences, but still, this concrete example gives me goosebumps. Just 100 years ago, almost within one lifetime, top scientists were not sure whether there were galaxies other than Milkyway. And today, we are observing quasars from the beginning of the universe and gravity waves from colliding black holes.