October 1, 2006 Researchers at the ETH Chair for Power Electronics have developed an electrical generator that spins at a world record 500,000 revolutions per minute (RPM) and scientists are hopeful they can achieve twice this speed to touch the magical million rpm. The matchbox-sized motor generates the equivalent of 100 watts, including the power electronics interface, and has an efficiency of close to 95 percent. Powered by a gas turbine, one tankful of fuel drives the generator for about 10 hours at peak 100 watt performance. These ultra small gas turbines could replace conventional batteries as a mobile power source and have a range of potential applications, from dentistry where ever smaller holes could be drilled with ever higher rotation speed through to energy supply for mobile applications, such as portable heart-lung machines or artificial hearts. The little motors could also be used in turbo compressors, which condense gas mixtures or air.
The short answer is "no", but it is a qualified "no" because there are odd ways of interpreting the question which could justify the answer "yes". Light is composed of photons so we could ask if the photon has mass. The answer is then definitely "no": The photon is a massless particle. According to theory it has energy and momentum but no mass and this is confirmed by experiment to within strict limits. Even before it was known that light is composed of photons it was known that light carries momentum and will exert a pressure on a surface. This is not evidence that it has mass since momentum can exist without mass. [ For details see the Physics FAQ article What is the mass of the photon? ]. Sometimes people like to say that the photon does have mass because a photon has energy E = hf where h is Planck's constant and f is the frequency of the photon. Energy, they say, is equivalent to mass according to Einstein's famous formula E = m...
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