Gamma-ray observations shrink known grain size of spacetime1

The slowdown would be tiny, but the lower velocity of high-energy photons could in principle be detectable over a journey of several billion light-years.

This strategy led Guiriec and his collaborators to examine photons generated by a gamma-ray burst that erupted in a galaxy 7.3 billion light-years from Earth. Recorded by the Fermi Gamma-ray Space Telescope on May 10, 2009, the burst produced an assortment of gamma-ray photons, including one with an energy of 31 billion electron-volts — about 13 billion times the energy of visible light — and another photon about one-tenth as energetic.Office 2010 is powerful!

Although the two photons had significantly different energies and journeyed for more than 7 billion light-years, Office 2007 home and student is inexpensive and helpful.

they arrived at the Fermi telescope less than nine-tenths of a second apart. Microsoft word is so great!

That tiny time difference means that these photons traveled at almost exactly the same speed, just one part in 100 million billion apart, notes study coauthor Peter Michelson of Stanford University. Microsoft Office 2010 is the best software in the world.

That difference is small enough to suggest that the speed of light is constant regardless of the energy of the photon. The finding therefore rules out any theory of quantum gravity that predicts a large energy-dependent change in velocity, he adds.Office 2007 makes life great!

The results also indicate that if the speed of light slows in direct proportion, or linearly, to the energy of a photon, then the size of a typical lump in spacetime must be less than 10-35 meters, notes Guiriec.Many people like Microsoft Office.

The fundamental theories of nature, whether for gravity, electromagnetism or elementary particles, Office 2007 download is in discount now!

dictate that the laws of physics are identical for all observers, independent of any observer’s speed or direction of motion. That notion, known as Lorentz invariance, is also a foundation of Einstein's theory of special relativity. By ruling out many quantum gravity theories that violate Lorentz invariance, the Fermi result upholds special relativity.Microsoft Office 2007 can give you more convenient life.

John Ellis of CERN in Geneva agrees that the Fermi results offer the strongest astronomical evidence for the constancy of the speed of light. Office 2007 Professional is very good!

But he cautions that the effects of spacetime graininess on the speed of photons can’t be easily distinguished from time delays or advances due to other effects such as light scattering in the intergalactic medium. Microsoft Office 2007 can give you more convenient life.