How Does Looking into the Past with Telescopes Work?

You can look into the past using telescopes because light takes time to travel, just like it takes time for your friend to run from one end of the playground to the other.

Light is like a message sent from far away, and when you use a telescope, you're catching that message long after it was sent.

Imagine your friend is holding a flashlight at the top of a really tall slide. When they turn it on, the light starts traveling down the slide to reach you at the bottom. It doesn’t get there instantly, it takes a little time to travel all that way.

Stars are like friends who are super far away, and telescopes help us catch the light they send. The farther the star is, the longer its message (or light) takes to reach us.

If a star is 100 light-years away, it means the light we see now started traveling 100 years ago. So when you look at that star through a telescope, you're seeing what it looked like 100 years ago, like watching a movie from long ago.

It’s like your friend sending you a message on a really long slide, the farther away they are, the longer it takes for their message to reach you.