Isaac, the consensus buster

7 Jul 2013

For centuries, a consensus theory ruled the roost, as science (a generalisation) had known that a piece of glass could be made to produce a spectrum of colours when sunlight was poured through it. From Aristotle onwards it was considered that this took place because pure celestial light (or white light) was changed by contact with a terrestrial substance. At the age of 24, Isaac Newtone set about debunking this consensus chestnut (as they say). Using a pair of glass prisms he used the first one to produce the familiar colours (of the rainbow) and used the second prism to pick up the coloured light exiting the first prism, recombining into white light. Newton then passed rays of each individual colour of light, red to blue, through a pinhole in a piece of card and then through a second prism. He showed the colour exiting from the second prism without breaking down further. It always stayed the same. From the experiments he established that white light was a combination of a set of primary colours, Allan Chapman, Gods in the Sky p13