Valentine’s day, 2015: According to legend, the three saddest mathematical love stories concerned the tangent lines who had just one chance to meet, and then parted forever; the asymptotes who became ever closer but could never get together; and the parallel lines who never got a chance to meet at all.

I first heard that one at a mathematics congress, many years ago, and was reminded of it just recently. It got me thinking about the rather different way that some mathematicians think, even about love. Could you, I wondered, express love in an equation?

Then I remembered. In the days when I had achieved some notoriety (and an IgNobel Prize) for using physics to work out the best way to dunk a biscuit, I was asked to express the results in the form of an equation ( After that, publicists kept approaching me to produce yet more equations – for the best way to park a car, the best shape for a breakfast cereal bowl, even the best shopping day before Christmas. The pick of the bunch, though, was an email from a card company asking me to produce an equation for love to use on their Valentine’s day cards (see for my attack on these reprehensible imitators).

I refused this invitation, as I did most others, on the grounds that it trivialized science and mathematics. But recently I found something that might have fitted the bill. Here it is (at the head of this post), just in time for Valentine’s Day.

What do you think?

ADDENDUM (AUGUST 4th, 2015) Since I wrote this piece, I have discovered a beautiful paper by Steve Strogatz of Harvard University in which he describes the love between Romeo and Juliet in terms of a pair of differential equations. Here it is

Strogatz Love affairs and differential equations

As Steve points out, ‘the term “many-body problem” takes on new meaning in this context’.


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