Okay kiddo, so Alexander Friedmann was a very smart man who lived a long time ago, in the early 1900s. He was a scientist who studied how the universe worked, and he came up with some really cool ideas that helped us understand more about space and time.
One of the things Friedmann discovered was that the universe is expanding. Imagine you had a balloon that you blew up really big, and then imagine all the stars and galaxies in the universe were on the surface of that balloon. As you blew it up, all the stars and galaxies would move away from each other, just like how the universe is expanding.
Friedmann also came up with some equations that showed how the universe was formed and how it has changed over time. He believed that at one time, all the matter in the universe was packed into a tiny ball that was smaller than a dot. This ball was really hot and really dense, and it eventually exploded and started expanding, which is what we call the Big Bang.
Friedmann's work helped us understand more about the history and future of the universe, and it paved the way for other scientists to make even more discoveries. So now we can look up at the stars and galaxies and know a little bit more about how they got there and what might happen in the future. Cool, huh?