The age of the universe is how long it has been in existence. Scientists estimate that the universe is around 13.8 billion years old, which means it was created a very long time ago. This is hard to imagine because it's so far away in time - it's much older than any of us can remember! Scientists learned this age by studying the distant stars to figure out how far away they are and how long they've been traveling through space. They also looked at other signs in the universe like radiation from space to gain more evidence. It's an amazing thing to think about how the universe has been around for such a long time!