Look into the night sky and you gaze into eternity. Beyond the few thousand stars your eye can see lie the hundred billion suns of our own galaxy; and beyond the Milky Way, galaxies by the billion glimmer across an immensity the human mind can scarcely grasp. Will we ever understand the Universe? We can but try.

The Solar System
We live on a planet – one of nine that we know of – that orbits a star we call the Sun. This is our Solar System and by ordinary standards it is vast: travelling by car at a steady 112km/h (70 mph), it would take around 6,500 years to reach the outermost planet, Pluto.

The Galaxy
As stars go, there is nothing very special about our Sun or its Solar System. In fact, the Sun is one of around 100 billion other stars that revolve together in a spiral-shaped cluster known as a galaxy. We call this galaxy the Milky Way. Until the 1920s, it was thought that the Milky Way was the Universe.

The Universe
In fact, the Milky Way is only one of at least 100 billion galaxies. These galaxies are moving away from each other, which means that the Universe is getting bigger by the day. It also means that space expands as time passes – and that the Universe started out very, very small.