If you’ve ever played with a magnifying glass, you’re probably well aware of the incredible energy contained in a focused beam of sunlight. When you scale up a light collector to about 10 times the size of a humble handheld lens, you can create a beam hot enough to sterilize water in 15 minutes – or, as a Californian science instructor learned the hard way, melt the interior of your car.
As reported by Gizmodo, Marc “Zeke” Kossover, a teacher in residence at the San Francisco Exploratorium, brought a 1-meter (3.3-foot) diameter parabolic mirror with him to work recently, then made the mistake of leaving it in the back of his Subaru.
“Let's say you were into making solar ovens. Let's say that you decided a few years ago to make the best solar oven ever,” Kossover wrote in a post on The Blog Of Phys describing the incident. Kossover then explained how he spotted a discarded satellite TV dish on the side of the road, and realizing its immense potential as a DIY reflector, picked it up and rushed off to the plastics store for reflective mylar coating.
Once assembled, his sunlight concentrator proved to be quite potent. Though it did not focus light very tightly, the spot it generated was impressively hot.
Parabolic reflectors can gather and concentrate both electromagnetic energy – like light and radio waves – and sound waves. Mirrored reflectors are used for a variety of optical applications, such as telescopes, flashlights, and searchlights.
Flash forward to earlier this month, when Kossover decided to bring his mirror in to work at the science museum. He stashed it face-up in the back of his car, planning on carrying it into the building alongside other equipment. But he couldn’t manage all the stuff on one trip, so he left it behind with the intention of returning for it soon after.
But instead, he forgot all about his powerful creation, and it sat in his Outback for the next several hours, on one of those elusive bright, sunny Bay Area summer days
“Coming back in the afternoon, I sat in the driver seat and looked into the rear view mirror,” Kossover wrote about discovering the subsequent oozing plastic car panels. “I think I was lucky that my car didn't catch on fire.”
Obviously, Kossover has a good sense of humor about the incident, and like any good science communicator, chose to turn it into a teachable moment. His post ends with a link to “excellent instructions” for building your own parabolic mirror.