## Plus Advent Calendar Door #18: Joy to despair

Submitted by Rachel on December 18, 2014
If you're feeling a bit weary in the run up to Christmas (I know we are!) we thought you might like to put your feet up and have a cup of tea instead of whatever it is you are working on. You can relax because every thing you've ever produced or will produce is already encoded in a number known as *Champernowne's constant*, consisting of every positive whole number listed after the decimal point:

0.1234567891011121314151617….

This is because this number is *normal*, which implies it contains a copy of every finite string of numbers in its infinite decimal expansion. This includes every article we have ever written or will write, every song anyone's composed, every film shot, every report written and every spreadsheet created, translated into numerical form (as it would be when stored on a computer). Lots of more famous numbers, such as , *e* and are also thought to be normal. In fact although mathematicians know almost every number is normal, they have only been able to prove this is true for a handful.

Unfortunately for you, and for us as we try to finish a few more articles before Christmas, even though all the work we will ever write is already present in the digits of Champernowne's number, we aren't going to be able to head to the pub just yet. Our articles and everyone else's work are swamped by every other possible string of numbers and we're going to have to produce them the hard way after all.

The idea is beautifully explored by the Argentine author Jorge Luis Borges in his short story "The Library of Babel" (published in the anthology *Fiocciones*). His library contains every book that is possible to write in a given alphabet, shelved in a seemingly endless complex of connected identical rooms (it looks a bit like the strange book filled place Matthew McConaughey found himself in towards the end of the Interstellar). The librarians were initially overjoyed to discover that the library contained every possible book. But their joy soon turned to despair when they realised that virtually all the books in the library would be nonsensical, the pages randomly filled with letters. They would spend their lives journeying through the endless identical rooms in a quest to find meaning among the books, knowing they were almost certain never to find it.

Borges' writings are full of such inventive and poetic explorations of philosophical and moral ideas. We came across this beautiful story when writing about normality and randomness for our book *Numericon*, and ended up devouring the rest of *Fiocciones* and have since gone on to read many others. You can also read more about the maths behind this story in The amazing librarian on *Plus*.

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