.comment-link {margin-left:.6em;}

2Physics Quote:
"Stars with a mass of more than about 8 times the solar mass usually end in a supernova explosion. Before and during this explosion new elements, stable and radioactive, are formed by nuclear reactions and a large fraction of their mass is ejected with high velocities into the surrounding space. Most of the new elements are in the mass range until Fe, because there the nuclear binding energies are the largest. If such an explosion happens close to the sun it can be expected that part of the debris might enter the solar system and therefore should leave a signature on the planets and their moons." -- Thomas Faestermann, Gunther Korschinek (Read Full Article: "Recent Supernova Debris on the Moon" )

Sunday, January 08, 2006

Einstein Is Precisely Right

Precise tests of the predictions of Einstein's Theory of Relativity are important because special relativity is a central principle of modern physics and the basis for many scientific experiments as well as useful instruments like the global positioning system (GPS).

The December 21st issue of Nature carries an article describing an experiment that performed the most precise direct test ever of what is perhaps the most famous formula in science: E=mc^2, or that the energy (E) equals mass (m) times the square of the speed of light (c^2), a direct outcome of Einstein’s theory of special relativity.

The experiment was performed by 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) .

According to the basic laws of physics, every wavelength of electromagnetic radiation corresponds to a specific amount of energy. The NIST/ILL team of scientists determined the value for energy in the Einstein equation by carefully measuring the wavelength of gamma rays emitted by silicon and sulfur atoms. Then comparing these numbers 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. This result is “consistent with equality” and is 55 times more accurate than the previous best direct test of Einstein’s formula.

Congratulations, Mr. Einstein! It was a good way to end the Year of Physics.



Post a Comment

Links to this post:

Create a Link