The Expansion of the Universe

Edwin Hubble
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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.

Although everything is moving away, it's down to the fact that the entire Universe is expanding. Thus, if we lived in a different galaxy, our own Milky Way would also look like it was doing a runner.

You can get an idea of how this works by imagining that the Universe is a giant balloon with 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 motion was the astronomer 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.