The Expanding Universe

Edwin Hubble

Image courtesy of the Mt. Wilson Archive

When we look at distance galaxies, we find that they all seem to be moving away from us. The further away they are the faster they seem to be moving.

This may make it look like everything is running away from us, but don't worry! In fact, this is because the entire Universe is expanding.

So, if we lived in a different galaxy, our own Milky Way would look like it was running away as well.

You can get an idea of how this works by imagining that the Universe is a giant balloon with the galaxies stuck on to it like this experiment. No matter which galaxy you live in, all the others will get further away as the balloon is blown up.

One of the first astronomers to measure this was Edwin Hubble in 1929. It is now called Hubble's Law.

The expansion of the Universe is one of the main reasons why astronomers think that the Universe started with a Big Bang.