Friday the 13th: The Universe Has a Sense of Humour.

Today is Friday the 13th, a date on which otherwise sensible human beings become suspicious of ladders, black cats and perfectly innocent mirrors.

Nobody is entirely sure why. The superstition appears to have developed from two older fears: the number 13 and Friday. The earliest clear written references to their unfortunate combination have been traced to France in 1834.

Things really took off in 1907, when American author T. W. Lawson published Friday, the Thirteenth, a novel about a stockbroker exploiting the date to cause financial chaos. Apparently, even back then, people were quite happy to lose money over something entirely imaginary.

There are several theories about the origins.

One involves the Last Supper, where Jesus dined with his twelve disciples. Thirteen people were present, including Judas, who rather spoiled the occasion. Jesus was subsequently crucified on a Friday, although the supper itself took place on Thursday. Clearly, the calendar department had some explaining to do.

Another theory involves Loki, the Norse trickster god, supposedly gatecrashing a dinner of twelve gods in Valhalla and causing the death of Balder. It's a wonderful story, although the original Norse sources don't actually describe this thirteen-person dinner party. Folklore, it seems, occasionally enjoys embellishing the guest list.

Then there's Friday 13 October 1307, when King Philip IV of France ordered the arrest of the Knights Templar. A genuinely unpleasant episode in history, but despite its excellent horror-film credentials, historians have found no convincing evidence that it inspired the superstition.

So there we have it. Centuries of mythology, religion, historical coincidence and literary embellishment have combined to make one particular date rather unpopular.

Meanwhile, the universe is approximately 13.8 billion years old, contains hundreds of billions of galaxies and operates according to physical laws we barely understand.

And humanity is worried about a Friday.

Friday 13th – still beats a Monday.