“What’s really lacking,” Michelson said, “is a laboratory experiment that tells us anything. So we have to use cosmology: We use the universe as the lab.”
The photons from GRB 090510, detected on May 9, ranged from 10,000 electron volts — the energy unit of choice in physics — to 31 billion electron volts, a factor of more than 1 million, in seven brief bursts over about two seconds.
The spread in travel time of 0.9 second between the highest and lowest-energy gamma rays, 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, said the Nature paper, whose lead author was Sylvain Guiriec of the University of Alabama.
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