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Rewriting general relativity? Putting a new model of quantum gravity under the microscope
Posted by wideant in Quantum Physics on March 1, 2010
Does an exciting but controversial new model of quantum gravity reproduce Einstein’s theory of general relativity? Scientists at Texas A&M University in the US explore this question in a paper appearing in Physical Review Letters and highlighted with a Viewpoint in the August 24th issue of Physics.
“If it ain’t broke, don’t fix it,” sums up fairly well how many scientists have viewed Einstein’s theory of general relativity. The theory, which Einstein developed in the early 20th century, says that matter curves spacetime, and it is this curvature which deflects massive bodies – an effect that we interpret as the influence of gravity. The theory has been tested to extremely high accuracy and without it, our satellite global positioning system would be off by about 10 km per day. Read the rest of this entry »
MU fitness expert creates MyActivity Pyramid to help adults exercise
The MyActivity Pyramid, a new fitness guide developed by a University of Missouri Extension fitness specialist, provides physical activity recommendations for adults in a fun and easy-to-understand format.
“The MyActivity Pyramid offers a visual representation of the new physical activity guidelines from the U.S. Department of Health and Human Services (HHS) on the recommended amounts and type of activities for improved health and fitness,” said Steve Ball, associate professor of exercise physiology in the College of Human Environmental Sciences. “The pyramid offers a variety of ways that adults can achieve these recommendations to improve their health and quality of life.” Read the rest of this entry »
Flipping a photonic shock wave
Posted by wideant in Optics & Photonics on February 28, 2010
A team of physicists has directly observed a reverse shock wave of light in a specially tailored structure known as a left-handed metamaterial. Although it was first predicted over forty years ago, this is the first unambiguous experimental demonstration of the effect. The research is reported in Physical Review Letters and highlighted with a Viewpoint in the November 2 issue of Physics.
Light moving in a vacuum sets the ultimate speed limit, but light travels more slowly through materials like glass and air. Speedy electrons or other charged particles can briefly outrun light in matter, producing a shock wave in the form of a cone of light known as Cerenkov radiation. The eerie blue glow in the cooling water of nuclear reactors is result of particles moving faster than the speed of light in water. In normal substances, the radiation is emitted in a forward cone. Left-handed metamaterials, however, have unusual effects on light that should reverse the cone’s direction. Read the rest of this entry »