Physicists have measured the speed of light at the highest energies and found that it is still constant, everywhere in the universe, even in gamma rays emitted by sources such as exploding stars.
This means that even at the highest energies we can detect, one of the pillars of Albert Einstein's theory of special relativity still remains unshakable.
“The way light behaves at very high energies has real implications for the world around us,” said astrophysicist Pat Harding of Los Alamos National Laboratory in New Mexico.
Lorentz invariance is a fundamental principle of special relativity. It expresses the fact that no matter where you are in the universe, the laws of physics – including the speed of light – remain the same.
However, there are theories suggesting that Lorentz invariance can be violated at very high energies. If confirmed, we will need new laws of physics to explain this. But we must also discover this.
If Lorentz invariance breaks down at high energies, then high-energy phenomena must exhibit unexpected behavior, incompatible with the theory of relativity; light, for example, could travel at different speeds.
The HAWC Observatory recently detected a number of gamma rays with energies above 100 TeV. This fact alone imposes restrictions on the violation of Lorentz invariance – this means that photons do not move faster than the speed of light in vacuum.
This does not mean that the Lorentz invariance cannot be violated even at higher energies, but it does mean that it remains true within our detectable limits. And this is really great.
The study was published in Physical Review Letters.
Sources: Photo: Crab Nebula, gamma ray source. (NASA / ESA / J. Hester / A. Loll / Arizona State University)
