Texas State U. Students Trace Caesar's Conquest

There's been an ongoing debate among scholars as to exactly when and where Julius Caesar first crossed the English Channel and entered Britain -- one of the furthest outposts that he conquered.

Okay, that debate was news to me. But it turns out a team from Texas State University, including two undergraduate honors students, have now settled the controversy once and for all -- by analyzing how the moon affected the tides that Caesar and some of his troops described.

Solving the puzzle involved an ingenious mix of scholarly research -- both on the Roman texts and doing the calculations of the moon's position during the dates in question -- and hands-on research at the locations involved, which included sailing a small boat along the shoreline to figure out whether Caesar turned left or right along the coast from the point he first reached land (the text, apparently, just says he turned, but doesn't say which way).

And in an especially nice touch, it also involved throwing some apples into the water off a pier, to provide a highly visible (and presumably highly biodegradable) indicator of which way the currents were flowing -- at exactly the right time.

Kellie N. Beicker and Amanda F. Gregory, the two honors students, traveled to England last summer with professors Don Olson and Russell Doescher to recreate the scene of the invasion. August 25-26 of 2007, it turns out, just happened to be exactly the right time to replicate exactly the timing of the moon's cycle with the time of the year as it was in 55 BC, the year of the invasion. The last such perfect match was in 1901, so it was important to seize the occasion this time around -- the next match isn't until 2140.

Olsen has been doing this kind of thing -- a specialty he calls "forensic astronomy" -- for many years now. It's a key feature of his highly popular astronomy class, called "Astronomy in Art, History, and Literature."

Very often, as in this case, it leads to new findings that are described in articles for Sky & Telescope magazine (this one's in their August issue, just out). In the past, the classes have pinpointed the timing of a crossing of Boston Harbor before Paul Revere's famous ride, traveled around France to identify the exact dates and places that Van Gogh depicted in several of his paintings, and dated a famous photograph by Ansel Adams. They've also studied an amazing array of very sophisticated astronomical references in Shakespeare's Hamlet, and identified pivotal World War 2 landing conditions. Almost always, a few lucky undergrads get to go along, and often, as this time, they get to share the credit with the two profs when the results get written up for Sky & Telescope. And they also learn some very creative thinking.

You can read more about some of these projects here in stories I wrote for the Boston Globe science section, about trips investigating  Columbus'  use of astronomical knowledge, the timing of the Boston Massacre, and investigating Van Gogh's paintings. There are also interesting pieces here and here.

Roger Sinnott, an editor at Sky & Telescope who has been working with Olson on these articles for many years, got to go along on this trip with the Texas team, and he's blogged about the experience. He has nice photos of the White Cliffs of Dover where Caesar originally arrived. It's all very scenic I'm very envious.

And my fellow Discovery blogger Jennifer Ouelette has a very good entry about it on Twisted Physics, going into much more detail about what they actually determined, and how they did it.

Photos - top: courtesy of Don Olson; bottom: courtesy of Sky & Telescope