This morning has me packing and preparing for a trip to England, to take part in the annual editorial board meeting of the New Journal of Physics and then to spend a few days visiting my family. A additional bonus is that a good friend of mine, a historian, will be in London at the same time, and I’m looking forward to getting well and truly screwed by the exchange rate when we sample some of London’s culinary delights. I expect that, as usual, our conversation will turn to some of the comparisons and contrasts between our fields.

So it was fun to see that Sky & Telescope is reporting on work by Don Olson and collaborators at Texas State University, in which they claim to have laid to rest the historical question of precisely when Julius Caesar landed in Britain. The Roman invasion has had open questions associated with it because although Caesar approached the white cliffs of Dover, Celtic warriors armed with spears (no doubt chanting “Romanes Eunt Domus“) deterred him from landing. The choice of an alternate site was guided by the tides, and it is this that has apparently opened the door to astronomers.

Olson calculated that the complex tidal patterns in August 2007 would mimic extremely closely those in August of 55BC, and performed several experiments in the English Channel during that month. He was fortunate to have at his disposal modern astronomical technology, the use of which was pioneered by Newton, and which has been perfected more recently by G. Smith – the so-called apple. Dropping this “apple” into the ocean from the pier at Deal (where Caesar is thought to have landed), Olson and team were able to understand the dates on which it would have been reasonable for the tides to bring the Romans from Dover to Deal. The answer appears to be August 22-23. As the BBC reports

This is the beach preferred by most historians but rejected by tide experts in the past. A modified reading of Caesar’s reference to the “night of a full Moon” also leads to the August 22-23 date, Dr Olson claimed.

“The scientists were right about the tidal streams and so were the historians about the landing site,” he explained.

So there’s a bit of something here for both my historian friend and me.