The universe has a very special feature which is a great advantage to astronomers, and which lets them do something many other scientists can’t: it lets them look back in time.
The feature I’m talking about is the finite speed of light. Everyone knows that light has a speed and that it’s very fast (close to 300,000,000 m/s!), but there are implications to that which it’s easy to miss if you spend most of your life living on a ball a few thousand miles across. Since most signals we get from distant objects are in the form of light rays of some sort - and no signal can travel faster than light anyway - we can’t get information on them instantaneously. When you look into the sky during the day, the sunlight you can see has been traveling from the Sun for over eight minutes. That means that if the Sun were to suddenly explode or disappear (or rather more likely, experience an event like a solar prominence or flare) it would take eight minutes before we had any way of telling.
The fact that the fastest thing in the universe takes eight minutes to cross the distance from here to the Sun highlights just how enormous it is, but eight minutes isn’t really that long in other respects. The Sun looks pretty much the same now as it did eight minutes ago, after all. But the other stars in our galaxy are between 4 and 80,000 light-years away (a light-year being the distance light travels in a year) so the delay is much greater.
