WASHINGTON, Oct. 28 (UPI) -- NASA says its Fermi Gamma Ray Space Telescope ended its first year of operation by obtaining a measurement that is evidence of the structure of space-time.
During its initial year, Fermi mapped the extreme sky with unprecedented resolution and sensitivity, NASA said, capturing more than 1,000 discrete sources of gamma rays -- the highest energy form of light.
But capping those achievements is a measurement that provides rare experimental evidence about the very structure of space and time, unified as space-time in the theories of the late theoretical physicist Albert Einstein.
On May 10, Fermi and other satellites detected a short gamma ray burst that scientists think occurs when neutron stars collide, NASA said. Of the many gamma ray photons Fermi detected from the 2.1-second burst, two possessed energies differing by a million times. Yet, scientists said, after traveling some 7 billion years, the pair arrived just nine-tenths of a second apart.
"This measurement eliminates any approach to a new theory of gravity that predicts a strong energy dependent change in the speed of light," said Peter Michelson, Fermi's principal investigator at Stanford University. "To one part in 100 million billion, these two photons traveled at the same speed. Einstein still rules."