I’ve recently been fascinated about the neutrino that was said to go faster than light between the CERN accelerator and a lab in Italy. My initial reaction was that there must be an error in the scientist’s calculations. However, I must confess that I have been fixated on the news and blogging on the subject. It turns out that the error that the scientists made could easily have been pointed out by any sharp minded physics undergraduate. It was a mix-up of reference frames. The timing was done by GPS satellites that are whizzing past at 9000 miles per hour through space. The distance measurement was done here on the ground. The satellites are moving fast enough through space relative to the surface of the Earth that there is a relativistic “shortening” of the distance between the the points from the reference frame of the GPS satellite. Yes that’s right. Relativity can shorten distances. To gain clarity, allow me to expand to a much greater scale. The galactic central point is some 30K light years away. If you were to build a spaceship that could travel very nearly as fast as light, then it would take it about 30K light years for it to get there from our perspective here on earth. Now imagine that you had over 60K earth years to conduct such an experiment using an unmanned ship that could report it’s clock time upon reaching the center of the galaxy. From your perspective it would take over 60K years before you received a message from the spaceship indicating that it had reached galactic center point and the amount of time that had passed during the voyage. Thanks to the mind-boggling implications of relativity, that ship would report that the entire voyage took just 2 years! Now you may erroneously conclude that the ship was travelling 15K times faster than light. However, it was most certainly not. From the spaceship's reference frame, relativity had greatly shortened the distance between our solar system and the galactic center point. Crazy stuff, but true. Now back to the experiment here on Earth. Replace thousands of years with nanoseconds, bizzilions of miles with several hundreds of kilometres, near light speed travel with just pretty fast GPS satellites and voila - mass confusion. In the CERN experiment, the relative speed of the satellite to the surface, even tho only a tiny fraction of the speed of light, has very slightly shortened the distance that the neutrino had to travel. Since the distance was shorter from the satellites reference frame and since the clock was in the satellite’s reference frame, therefore the time taken for the neutrino to travel from point A to point B seems nonsensical to us on Earth (faster than light). We see the distance from point A to point B being longer than it is from the satellite’s reference frame. Hence: confusion. In short, the scientists forgot to take into account the relativistic effects of the rotation of the Earth. And ironically, proved yet again, the strange effects of relativity. |