Alice has a pot at Jim Al-Khalili’s rash promise…..
So neutrinos might – just might – go faster than light. Maybe some neutrinos go faster than some light – maybe. Let’s face it, we don’t really understand neutrinos as much as light. There’s an awful lot of them, and they might – just might – have a little bit of mass – or at least some of them might.
Say the neutrino field (in all of its varieties) has zero mass, so it propagates at the speed of light. But what is that? The speed of light depends on its frequency, through the refractive index of the medium. Do you retort there is no medium – that the aether went out a hundred years ago? Well there is hardly empty space between Geneva and Gran Sasso.
Also, the full understanding (if that is what we have) of light propagation requires us to distinguish between ray optics and wave optics, even in “empty” space. To a very good approximation we work out how light paths are bent by the Sun’s gravity by applying Fermat’s Principle (ray optics) to the path length. One way of describing this latter calculation (see The Theory of Gravity by A. A. Logunov, 2001) is that the Riemann forward light cone is contained within the Minkowski causality cone. But there is a region of space-time between the two cones, and that region is where there is scope for different frequencies to behave differently.
Now throw in the new varieties of speed-of-light objects and, without needing to wander into any exotic new dimensions, you have some new physics. While holding firm to causality, I would not be sure that Jim Al-Khalili will not have to “eat his boxer shorts on live TV”.