Measuring the Speed of Light ... In Granite?

This morning, I read in the Telegraph that neutrinos appear to have travelled faster than the speed of light.

I don't tend to opine on matters scientific, so take the following with a hefty pinch of salt, but...

Some background: light travels at different speeds through different substances. The classic "186,000 miles a second" is the speed through a vacuum. But the speed of light through air and glass and water and diamond are all different: the difference between air and glass is why prisms and spectacles work; the difference between air and water is why an oar appears to bend at the surface of the water; the difference in speed between space and air is why the daylight sky is blue.

The experiment in question involves sending neutrinos 750 miles 732km or so between source and detector. Since the neutrinos travel in a straight line, that requires passage through the earth. So what this experiment appears to do (to me) is merely prove that the "speed of light" through rock differs from our initial expectation.

I could, of course, be wrong. Or worse, I could be unoriginal, but I'll back relativity over previous estimates of the speed of light through rock.

Update 2011-09-25: Corrected the distance involved.


  1. actually my good sir, the muon neutrino's had traveled faster then light speed in a vacuum, not light speed through a bunch of rocks.

  2. @Kirk

    Welcome, and thanks for commenting. I made the initial post assuming that the neutrino path had to be "through the Earth".

    Do you have a cite for the fact that it's through a vacuum? I made an effort to check this morning, but the preprint pdf from Arxiv won't display on my PC.

    The project web page tells me the neutrino path is 732km through the Earth, with a maximum depth of 11.4km. I think my assumption that neither budget nor engineering allow a straight-line tunnel of this kind is reasonable. However, it is an unfounded assumption, and I would welcome correction.