The life of Sir Isaac Newton, the details of his experiment to split light, and why he believed there were seven colours.

Life

Isaac Newton was born in Woolsthorpe on January 4th 1642. His father, Isaac senior, passed away three months prior to the birth and his mother, Hannah Ayscough, married Barnabas Smith in 1646, but he too passed away seven years later.

From the age of twelve to seventeen, Newton went to the King’s School in Grantham, but his mother pulled him out, determined to make Isaac into a farmer (even though he loathed agriculture). Eventually, one of the school masters persuaded her to let him return. Later, he moved to Trinity College to study the laws of motion. Over the years he became a member of the Royal Society and was elected Lucasian Professor of Mathematics. He passed away on March 31st 1727.

Experiments

Isaac Newton is most famous for his Three Laws of Motion which he wrote after an apple dropped on his head in the orchard next to his house. But he also managed to discover how light works.

Light Experiment

Newton drilled a tiny hole in the shutters of his bedroom window, allowing a thin but strong beam of light to shine through onto a table, where he had placed a glass prism. The prism projected the sunlight onto the wall, where it appeared as a rainbow-like pattern. His hypothesis was that white light was a concoction of different colours and that when they entered the prism, they all refracted by different amounts, causing the white light to split into seven colours: red, orange, yellow, green, blue, indigo and violet.

Debate

The final two colours in the spectrum, Indigo and Violet, are two shades of Purple. This caused a debate over whether or not they should be counted as two separate colours.

The human eye is rather insensitive to differences between Blue and Indigo, so the two appear very similar. Also, Indigo and Violet are usually seen as mere shades of purple, thus modern scientists believe that there are only six colours of the spectrum. In reality, Isaac identified seven colours of the spectrum so he could match them to the seven notes of a western major scale (he thought sound and light were closely linked) as well as the planets in the solar system (Neptune and Pluto had not yet been discovered) and the seven days of the week.