Your Burning Questions About the Olympic Torch, Answered
After 101 days of traveling by plane, train, automobile, Korean warship, zipline and even robot, the Olympic torch will finally reach the site of the Winter Games in PyeongChang, South Korea. This Friday, a lucky honoree will use it to light the Olympic cauldron in a grand, symbolic start to the games.
While the blaze looks like any other, its origins are special: It was lit not with matches or a Zippo lighter, but with a parabolic mirror, echoing rituals from Ancient Greece.
To brush up on algebra, a parabola is a particular type of arc that is defined by the exact curvature of its sides. Mathematically, these symmetrical curves all take some form of the equation, Y = X^2. Revolve a parabola around its axis, and you have the shape of a parabolic mirror.
Unlike most curves, which scatter incoming light in many directions, the reflected beams bounce from a parabola and all concentrate to one point, the focus. These reflective surfaces are used in a number of devices to concentrate not only reflected light, but also sound or radio waves. Satellite dishes, some types of microphones, reflecting telescopes and even car headlights benefit from the reflective properties of parabolic dishes.
In the case of the Olympics, when the sun shines on a parabolic dish, known to the ancient Greeks as a Skaphia or crucible, the rays all bounce off its sides and collect at one blazing hot point. Put a piece of paper—or a gas torch—in that focal point, and you get fire.
A lone parabolic dish does a decent job heating things up, achieving temperatures of at least hundreds of degrees. “That’s really very easy to reach,” says Jeffrey Gordon, professor of physics at Ben-Gurion University of the Negev in Israel. Some may even be able to reach temperatures in the thousands of degrees, says Jonathan Hare, a British physicist and science communicator. Hare has witnessed parabolic mirrors vaporize carbon, something that only happens at temps over 2,000 degrees Celsius (around 3,600 degrees Fahrenheit).