I promise I didn’t know this story that I discovered a few days ago while listening to one of my favorite radio programs: No es un Día Cualquiera, by RNE. Jesús Marchamalo, a journalist and writer, narrated to Pepa Fernández the unknown and suggestive story of the letter X. It caught my attention a lot and I decided to write this post.
After the letters “K” and “W”, the letter “X” is the least used in Spanish. First surprise, right?. However, it is the letter we use to fill out pools, answer multiple-choice questionnaires, and many other everyday things.
I love the symmetry of the letter “X”, because symmetry provides harmony and solidity. In mathematics, “X” represents unknowns, unknown quantities. Although the reason for this function is unknown, there are different theories. The theories can be reliable or unreliable, but what I’m not going to deny is that this one we are going to tell is very curious.
‘X,’ a printing problem?
In geometry, the iconic René Descartes’ work ‘La Géométrie’ introduced algebraic notation. It is what we use today, based on the final letters of the alphabet (which are X, Y, and Z) for the unknowns and the first ones (which are A, B, and C) for the constants.
Some hypotheses suggest that Descartes’ printer requested something curious from the philosopher. Specifically, that to name an unknown, he should use the letters of the alphabet that appeared least frequently in a written text. This way, he wouldn’t waste those more commonly used and scarce ones. X was repeated often in his mathematical texts. In printing, a different stamp was needed for each letter, which caused scarcity.
Other theories about the letter X
There are more theories and legends. For example, the Italian mathematician Pietro Cataldi represented the unknown in the 16th century as a crossed out 1. Later, this evolved into an X. Others consider Descartes’ inspiration to be a symbol used by German mathematicians to represent the unknown.
This resembled our letter X. Perhaps the most surprising one is the one I leave in this TED Talks video, in which Terry Moore tells us, ‘Why is “X” the unknown?’ Don’t miss it!”
And, one last thought. Why did Elon Musk choose to change Twitter’s name to X?
Video credit: TED
