# Mathematicians who changed the world: Rene Descartes (1596-1650)

Rene Descartes was a French mathematician who transformed the way we look at the world – through maps! His most famous contribution was the ‘Cartesian Coordinate System’, which is named after him. Descartes didn’t come up with this idea on his own though – he had help from a fly!

When he was lying on his bed one day, Descartes watched a fly buzzing about in his room. He realised he could describe the fly’s position with just three numbers (because the room was 3D). These numbers were the fly’s position in relation to the two walls and its height.

When we use this system for a graph, we describe points in relation to a point called the ‘origin’, which is like the corner of a room. The two walls coming away from the corner are the x and y axes. The x axis runs along the bottom and the y axis goes up. If we wanted to tell someone where the fly was, we’d give the x number (or ‘co-ordinate’) first, then the y co-ordinate, and then the z co-ordinate (if there is one).

It’s important we always use the same order, so we know we are all communicating in the same way. There are lots of places you might have seen this system in use already, like on a map or in a game of battleships!

Discover more mathematicians who changed the world:

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