Part of the show Stars, Cosmology and the Beginning of the Universe
Sarah in Hardwick asked:
How far is the nearest galaxy?
The nearest galaxy to our galaxy, the Milky Way, is called Andromeda. It's about 2 million light years away, and we think it looks very similar to our own galaxy. It's difficult to know what our own galaxy looks like because we're in it, but calculations show that it's a flat spiral disc shape. For a long time, people thought that our galaxy was the only galaxy, and that any smudges they saw in the sky were nebulae, which are clouds of gas that form new stars. It was only after some more looking and calculations that people realised that these smudges were too far away to be in our own galaxy. Even Einstein fell foul of misconceptions of that sort. When he was developing his theory of relativity, he had to put in a term that made the universe nice and stable. He thought it consisted of these fixed stars.