The story goes that, while watching a fly buzzing round the room (or crawling over the ceiling, depending on which version you prefer), the idea occurred to René Descartes that its position in space could be precisely defined by specifying just three mutually orthogonal measurements made from a fixed point. Thanks to that fly, we now have “Cartesian coordinates”.
René Descartes was really quite smart.
When he noticed a fly, René said:
“Mon Dieu! Its position
Is described with precision
By coordinates: x, y and z*”.
*For American readers: the letter z is pronounced ‘zed’ in Britain.
(There may be an alternative explanation: see “Helpful Helena“)
In 2023, Peter Wooding, a college friend from the 1960s, who had obviously taken more notice of the subtleties of the maths aspects than I had, emailed ideas for another verse. It was triggered by the well-known fact that, when chased, flies ‘go to ground’; perhaps they disappear into an ‘imaginary’ space, beloved of mathematicians, defined by three more Cartesian ‘unit vectors’?
(I forgot to make mention of another convention
Where directional vectors hold sway:
To establish a base
In this virtual space,
They’ll also need ‘i’, ‘j’ and ‘k’.)