Ponca City, We love you writes: "The NY Times reports that after a journey of 7.3 billion light-years, a race between gamma rays ranging from 31 billion electron volts to 10,000 electron volts, a factor of more than a million, in a burst from an exploding star have arrived within nine-tenths of a second of each other in a detector on NASA’s Fermi Gamma-Ray Space Telescope confirming Einstein’s proclamation in his 1905 theory of relativity that the speed of light is constant and independent of its color, energy, direction or how you yourself are moving. Some theorists had suggested that space on very small scales has a granular structure that would speed some light waves faster than others — in short, that relativity could break down on the smallest scales. Until now such quantum gravity theories have been untestable because ordinarily you would have to see details as small as the so-called Planck length, which is vastly smaller than an atom — to test these theories in order to discern the bumpiness of space. The spread in travel time of 0.9 second, if attributed to quantum effects rather than the dynamics of the explosion itself, suggested that any quantum effects in which the slowing of light is proportional to its energy do not show up until you get down to sizes about eight-tenths of the Planck length. "This measurement eliminates any approach to a new theory of gravity that predicts a strong energy dependent change in the speed of light," says Peter Michelson of Stanford. “"To one part in 100 million billion, these two photons traveled at the same speed. Einstein still rules.""
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