Ian Crofton

WHERE DOES THE ENERGY COME FROM?

next big leap came 1.8 billion years ago, when larger, more complex cells appeared. These so-called eukaryotic cells contain the DNA within a central structure, the nucleus. There are also a number of other specialist structures with particular functions. These are called organelles. The fact that some of them have their own

chink in this theory came in the 1920s when the American astronomer Edwin Hubble observed that the further away a galaxy is from us, the faster it is receding. He concluded that the universe is expanding, and that this expansion started in a single great explosion, which became known as ‘the Big Bang’.

Our Sun lies on one of the spiral arms of our galaxy, about 30,000 light years from the centre. The nearest star to the Sun is Proxima Centauri, just 4.24 light years away.