Most scientists accept that the Universe began with a Big Bang. But how do we know about something that happened so long ago? The Universe is expanding When we look at the night sky, the stars we can see are within our own galaxy. But there are also some fuzzy patches which we need a telescope to see clearly. These are other galaxies like our own - but they are much, much further away than the stars. If we look closely at these galaxies, we'd expect that some would be moving towards us and some would be moving away, But in fact, almost all galaxies are moving away from us - some at very high speeds indeed. We know the galaxies are moving away because of an effect called red-shift -...
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