One of the awkward aspects of modern physics is that its two most successful fields, relativity and quantum mechanics, are fundamentally incompatible, as things happen in the quantum world that relativity says should not be possible. That's left physicists looking for a way to harmonize the two, with two primary contenders: string theories, and quantum gravity theories. Testing either of them has been a bit challenging, but researchers have now managed to use a single, intensely powerful photon detected by the Fermi Telescope to significantly limit the number of viable quantum gravity theories.

The Fermi Gamma-ray Space Telescope has only been operational for about a year, but results from its observation have already been appearing in a number of significant publications. The observatory is designed to detect the highest energy radiation, which is only produced by the most energetic events in the universe, such as supernovae. In this case, the key observation was of a single photon produced by the gamma-r