After two years of work, with a purpose-built steel machine wired up to high-speed cameras, microphones and electronic sensors, a team of Japanese researchers has finally proved that a hard-boiled egg can jump. All it takes, according to Yutaka Shimomura and colleagues of Keio University, is a good spin. A spinning egg will spontaneously rise up from lying on its side to standing on its end. Shimomura, along with physicists at the University of Cambridge, had previously worked out why this is so, and predicted that the forces involved could also make an egg leap a tiny bit into the air2. You wouldn't be able to see it leaping in your kitchen, though; the jumps are expected to be less than a tenth of a millimetre high and last for only a few thousandths of a second.But does it really happen? To check, Shimomura's team had to make a device capable of spinning an egg perfectly, so they could be sure that the effect wasn't due to an upwards motion introduced by a spin done by hand. They also had to hit a spin rate of 1,800 revolutions per minute. So as not to be too messy and to ensure easy measurements, they used an ovoid-shaped metal egg in the experiments.The team placed their egg horizontally on a slab of polished copper, started it spinning, and filmed it. Three different methods of detection all showed that the egg made tiny jumps before rising to a fully upright position.A little bit of light was spotted shining through between the egg and the plate. More persuasively, microphones picked up the quiet cracking sounds of the metal egg hitting the plate in a series of impacts less than a second after the spin's initiation. And a break in physical contact between the two bits of metal caused a change in the electrical capacitance of the copper plate.
View: Full Article | Source: Nature.com
