I suspect he means that light maybe travels slightly slower than the constant c used in relativity. Maybe photons actually have a really tiny rest-mass. Maybe our measurements of the speed of light are all in non-perfect vacuum which makes it slow down a little bit.
If they had tiny mass, we would observe variance in measured values of c, since less energetic photons would move slower. Measurements of c have relative precision of at least 10^-7 and no dependence on energy has been observed in the vacuum. Therefore the measured speed of light doesn’t differ from the relativistic c more than by 10^-7. The relative difference which is reported in the neutrinost seems to be 10^-5.
I suspect he means that light maybe travels slightly slower than the constant c used in relativity. Maybe photons actually have a really tiny rest-mass. Maybe our measurements of the speed of light are all in non-perfect vacuum which makes it slow down a little bit.
If they had tiny mass, we would observe variance in measured values of c, since less energetic photons would move slower. Measurements of c have relative precision of at least 10^-7 and no dependence on energy has been observed in the vacuum. Therefore the measured speed of light doesn’t differ from the relativistic c more than by 10^-7. The relative difference which is reported in the neutrinost seems to be 10^-5.