The Universe
_______________________________________________________________________________________________________________________________________________________________________________________________________________________

7. Looking back in time

Figure 10.3
The Whirpool Galaxy
When we look at stars and galaxies, we are seeing over great distances.


More importantly, we are also seeing back in time.

When we see a distant galaxy, we are actually seeing how the galaxy used to look.

For example, the image on the right shows the Whirlpool Galaxy, that is about 23 million light-years from Earth. When you see an image of the galaxy, what are you looking at?

You are looking at the galaxy as it was 23 million years ago!

Since scientists can look back in time, they can better understand the Universe's history.

Some devices have helped experts look into our galaxy and beyond.

One of the first tools for space exploration was the telescope. It gave scientists their first look at what exists beyond Earth’s atmosphere.

Telescopes use lenses and mirrors to see beyond Earth’s borders.

A

L

N

C