A race between gamma rays across 7.3 billion years of time and space has resulted in a virtual tie, confirming Einstein’s theory of relativity once again.

The race was between gamma rays of differing energies and wavelengths spit in a burst from an exploding star when the universe was half its present age. After a journey of 7.3 billion light-years, they all arrived within nine-tenths of a second of one another in a detector on NASA’s Fermi Gamma-Ray Space Telescope, at 8:22 p.m., Eastern time, on May 9.

Astronomers said the gamma-ray race was one of the most stringent tests yet of a bedrock principle of modern physics: Einstein’s proclamation in his 1905 theory of relativity that the speed of light is constant and independent of its color, or energy; its direction; or how you yourself are moving.