It's called Greek fire. Invented around AD 670, it was one of the first flamethrowers, involving a pressurized siphon to shoot a stream of liquid flame at enemies. The Byzantine Empire used this incendiary weapon to defend against fleets of Arab ships in the first and second sieges of Constantinople in 674–678 and 717–718. "It was a very fearsome naval weapon at the time," says Tom Harris, who was one of the 232 students awarded bachelor's degrees from Caltech last week.
But historical details of the weapon—how it was invented and how it worked—are murky. That mystery made Greek fire a perfect thesis topic for Harris, who graduated with a double major in history and mechanical engineering. Working with Warren Brown, a professor of history at Caltech, Harris spent much of his senior year studying Greek fire and analyzing how it worked based on original historical documents and our modern-day understanding of fluid mechanics. He also consulted with Joe Shepherd, the C. L. Kelly Johnson Professor of Aeronautics and professor of mechanical engineering, and Tim Colonius, a professor of mechanical engineering.
His conclusions? "Greek fire was an impressive weapon, but it wasn't that effective in the naval warfare that was practiced at the time," Harris says. Although he points out that his analysis is far from definitive, he made some calculations using a simple model of how Greek fire might have worked, and found that the weapon could shoot fire as far as about 50 meters—which is not enough distance to devastate a foe in a naval battle. "A lot of people in the past have hypothesized that this device did not have a very long range, and that's why it wasn't really effective," Harris explains. "My analysis seems to corroborate that."
Harris came to Caltech with an undeclared major, thinking he would study computer science. But, having been an avid Lego builder as a kid, he was drawn to mechanical engineering. He also has an interest in medieval history, which similarly dates back to his childhood—he loved pirates and knights, and both his parents were history majors—and after he took Brown's medieval history class, his impression of the study of history changed. Instead of reading textbooks and analysis from other historians, Harris and his dozen or so classmates read and analyzed original documents.
After his sophomore year, Harris spent a month in Rome learning about structural engineering as part of a UC Davis program. He took advantage of his time in Europe by pursuing yet another childhood passion: swords. After the program ended, he stayed in Italy for another week, taking blacksmithing lessons in Le Marche, and he then went to England for another week of lessons. He made various pieces, including metal leaves, a fire poker, and scrollwork similar to the old metal handrails you can see around Caltech's campus. In England, he forged a short sword called a seax.
The following spring break, Harris once again traveled to England, to learn swordmaking. During his free time, he spent hours at the British Museum looking at swords and other medieval weaponry.
Returning to campus, Harris discovered that other Techers were interested in blacksmithing, and so—with the help of the George W. Housner Student Discovery Fund—he led an effort to get a blacksmithing forge for the student shop on campus. The forge hasn't arrived yet, but when it does, Ben Abbott, an electrical engineer with the LIGO project and a blacksmith with more than two decades' worth of experience, has volunteered to teach students the art and craft of blacksmithing.
For Harris, blacksmithing—and Caltech—allowed him to rekindle many of his childhood passions. "You could say this experience was about rediscovering my inner child and finding a more mature way of exploring these interests," he says.
Now that he's graduated, Harris will work as a quality engineer at Covidien, a company that specializes in biomedical devices, such as stents used to unblock arteries. Although he has no experience in biomedicine, he's looking forward to learning new things—something he's gotten used to at Caltech.
"Caltech has been a place where I could feed my desire to learn," Harris says. "I'm glad for the experience I've had here."