The NIST/ILL team determined the value for energy in the Einstein equation, E = mc 2, by carefully measuring the wavelength of gamma rays emitted by silicon and sulfur atoms. Börner and his collaborators were responsible for a highly successful gamma-ray measurement program at the ILL.Īccording to the basic laws of physics, every wavelength of electromagnetic radiation corresponds to a specific amount of energy. Deslattes and his collaborators developed methods for using optical and X-ray interferometry-the study of interference patterns created by electromagnetic waves-to precisely determine the spacing of atoms in a silicon crystal, and for using such calibrated crystals to measure and establish more accurate standards for the very short wavelengths characteristic of highly energetic X-ray and gamma ray radiation. The Nature paper describes two very different precision measurements, one done at MIT by a group led by David Pritchard and another done at the ILL by a NIST/ILL collaboration led by the late physicist Richard Deslattes (NIST) and Hans Börner (ILL). Other researchers have performed more complicated tests of special relativity that imply closer agreement between E and mc 2 than the MIT/NIST/ILL work, but additional assumptions are required to interpret their results, making these previous tests arguably less direct. Such tests are important because special relativity is a central principle of modern physics and the basis for many scientific experiments as well as common instruments like the global positioning system. This result is "consistent with equality" and is 55 times more accurate than the previous best direct test of Einstein's formula, according to the paper. By comparing NIST/ILL measurements of energy emitted by silicon and sulfur atoms and MIT measurements of the mass of the same atoms, the scientists found that E differs from mc 2 by at most 0.0000004, or four-tenths of 1 part in 1 million. Specifically, energy (E) equals mass (m) times the square of the speed of light (c 2), a prediction of Einstein's theory of special relativity. 22, 2005, issue of Nature, the researchers added to a catalog of confirmations that matter and energy are related in a precise way. GAITHERSBURG-Albert Einstein was correct in his prediction that E=mc 2, according to scientists at the Massachusetts Institute of Technology (MIT), the Commerce Department's National Institute of Standards and Technology (NIST), and the Institute Laue Langevin, Genoble, France (ILL) who conducted the most precise direct test ever of what is perhaps the most famous formula in science.
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