Exciting news broke earlier this week, at least for fans of Discovery Channel's Mythbusters (and oh yes, Jen-Luc Piquant is a mega-fan!). President Obama will make a special appearance on the December 8 episode of the series -- part of ongoing efforts of the administration to promote science, technology and engineering (STEM) education, starting with the Educate to Innovate campaign launched in 2009. In fact, he made the announcement during the first ever White House Science Fair. We are currently taking bets on how quickly Faux News and its noisy acolytes will start braying about how all this "promoting science to a broader audience" is really just a commie/Socialist plot to forcibly redistribute the wealth knowledge to the undeserving Ignorant. Or Muslims.
No doubt adding fuel to the fire, the episode in question will revisit the "myth" of the Archimedes "death ray." For those who don't recall the story, the brilliant Greek mathematician, Archimedes of Syracuse, was also known for building ingenious weapons of war to defend Syracuse from the invading Roman army. There was, for instance, a giant crane capable of capsizing ships, known as the Claw of Archimedes. Another such invention, legend has it, was a large curved parabola-shaped array of mirrors capable of collecting and focusing the sun's rays onto the Roman ships moored in the harbor, laying siege to the city. The heat caused the ships to catch fire and burn, and Syracuse was saved -- for awhile, at least. (Eventually the Romans overcame the city's defenses, and Archimedes was killed in the ensuing chaos. Set mathematics in Western Europe back a good 700 years, at least.)
Long before the Mythbusters appeared on TV, folks were trying to ascertain the validity of that legend. Skulls in the Stars has a classic post detailing the history of such attempts to test similar devices, usually with mixed results. Back in the 18th century, the noted naturalist, he Comte de Buffon (who also devised the "Buffon's Needle" puzzle) assembled an array of ordinary mirrors (40 in all) and managed to set a log pf tarred beechwood on fire from a distance of 66 feet. The more mirrors he used, the more effective the technique was at setting fires from a distance. With 128, he could set fire to a plank of tarred fir from a distance of 150 feet.
Thre was also an article by one John Scott in the late 19th century assessing the evidence for and against the effecitveness of an Archimedes "death ray." It appeared in the Proceedings of the Royal Society of Edinburgh. Scott was more skeptical than Buffon, noting that historical accounts closer to the time of Archimedes say nothing of burning mirrors, Livy and Plutarch among them. But it's a fun story, and I used it to talk about parabolas and finding the area under a curve in the first chapter of The Calculus Diaries. Some legends are worth repeating, whether or not they turn out to be true.
The Mythbusters have already tackled this challenge twice already: once on their own, and the second time with the help of team of scientists from MIT. Conclusion: it's most likely a myth, although in principle it's feasible. The MIT experiment managed to start a small fire on a wooden ship, although it quickly burned out. Considering the time it would take to set fire to a ship using such a technique -- think of how long it took when you, as a kid, tried to set a piece of paper on fire with a magnifying glass on a hot summer day -- flaming arrows would probably be more efficient. But I guess President Obama asked them to revisit the challenge. Why? Who knows? Maybe he's keen on getting a nifty death ray for the White House. (Cue mass hysteria from the paranoid fringe!)
Personally, I'd like to see the Mythbusters tackle a related challenge: the purported "death ray" that strikes poolside at the newly built Vdara Hotel in Las Vegas. It's part of the City Center complex, and the building has a distinctive parabola-like shape. Therein lies the problem. According to recent news reports, a vacationing lawyer was relaxing poolside at the Vdara, when he started to feel very warm, and then smelled something burning. It was... his HAIR! HIS HAIR WAS SMOKING! He jumped up from his seat and doused his head in the pool, then repaired to the bar for a stiff drink. The bartender nodded knowingly when he descibed his plight: "Yeah, we call that the Death Ray." The Las Vegas Review Journal published this helpful schematic to illustrate the principles at work:
I guess there was a reason no one was sitting in what would otherwise be a prime poolside seat. When the lawyer went back to retrieve his newspaper, he found the plastic in which it was wrapped had melted.
But I'm just a tad bit skeptical. I mean, check out this photo of the alleged newspaper:
It clearly spells out the word "VDARA." I smell a hoax. How did the sun's rays manage to carve out just those letters? Was there a "stencil effect" at work, i.e., over one of the curved windows? Inquiring minds need to know! And the Mythbusters are known for their inquiring minds and ingenious experiments. We eagerly await their findings.
UPDATE: Several commenters -- thanks, guys! Knew I could count on you! -- pointed out that the plastic bag itself was stenciled with black letters,the black absorbs the sun's heat faster, and hence the bag melted in just that pattern. Science! Also? We have been called "fluffy" in the comments section. We consider this a compliment. Jen-Luc Piquant humbly suggests that if you're looking for a detailed explication of this effect, with fancy diagrams and equations and all, a blog that proudly calls itself Cocktail Party Physics probaby isn't your best bet. Do that sort of thing at a cocktail party and you'll soon find yourself alone in a corner, doodling on a napkin and talking to the catering staff (who are paid to be there and already bored), while the other guests avoid you like the plague. Just sayin'. (Except if it's a cocktail party with physicists, in which case it's good form to provide a white board.) However, you can find just that sort of thing over at the most excellent blog, Dot Physics (formerly of SEED Science Blogs, now housed at Wired), and we thank said commenter for the link. Check it out!