The Age of the Universe

The Universe is expanding. Whichever way we look, stars and galaxies are moving away from us.

The speed with which stars and galaxies are moving away from us is proportional to their distance from us, so that if a galaxies is travelling twice as fast, it is twice as far. It really does seem as though all the stars and galaxies which make up the Universe were all in the same place at the same time.

The relationship between the distance of a galaxy away from us and the speed of the galaxyis given by Hubble's Law:

Usingand assuming the speed of recession has been constant since the big bang, or 14 billion years. In fact the Universe will be younger than this because it was expanding more rapidly in the past – gravity has slowed down the expansion of the Universe to it's present sedate rate.