As I drive along, I like to watch for palindromes – on license plates or signs or other man-made objects.
A palindrome is a word, phrase, number, or other sequence of units that can be read the same way in either direction. On MD license plates, what I call a P3 is a sequence of 3 characters like 1M1 or 282. These are trivial. The longest would be a P7 like 123M321 found on an earlier series of minivan plates. In the series of a million plates from 000M000 to 999M999 (themselves palindromes) only a thousand – or 1 in a thousand – would be palindromes, which makes them relatively rare.
In phone numbers, a number like 301 844-8103 would be a P10. (The number is bogus. I checked it out.) The longest I’ve seen was a sequence of 21 tiles (that is, a P21) in the floor of a rest room in a place where I worked.
Many, many palindromes have been coined in the English language. A well-known example is “Able was I ere I saw Elba” (Author unknown), which is also palindromic with respect to spacing.
The earliest datable example is the Latin “SATOR AREPO TENET OPERA ROTAS” (The farmer/sower, Arepo, sows the seeds), which can be dated to at least 79 AD. (The city of Herculaneum, you will recall, was buried in ash in an eruption of Mt. Vesuvius in 79 AD.) When arranged one above the other, the words form a word square that reads the same not only front to back but also up and down as well.
Palindromes can be found all over: in other languages, in prime number sequences, and in gene sequences. You can go looking for them, but most of the time they just pop out of a sequence of characters.
Palindromes are one example of the fun-with-words things I enjoy. If you’re interested, look it up.