# Why Are Faster-than-Light Neutrinos Such a Big Deal?

Nothing can go faster than the speed of light! This has been a mantra of physics for the past century. The central pillar of Einstein's famous theory of relativity, this core experimental truth in physics is now facing a slightly greater challenge.

Neutrinos are created and fly out of the enormous particle collider (LHC) at CERN on the Swiss-French border. Physicists sitting nearly 500 miles away in Italy have been clocking them. Several times now, their speed has appeared to be about three thousandths of a percent higher than the speed of light.

Why would confirmation of this result be such enormous news?

The principle driving relativity theory is a simple one. All objects move through spacetime at a constant speed. That is, they move about in space and forward in time in such a way that the speed in space and the speed in time add up to be a certain total (actually the speed of light) that never changes.

A football sitting still on the ground is traveling at the speed of light through time. Say you pick the football up and throw it. If you add together the speed it is going up into the air, the speed it is going to the left or right, and the speed it is going away from you, you have its speed through space. The speed that the ball travels through time is then the constant total speed minus this speed through space:

Speed in time = Constant total spacetime speed - space speed.

This has the fascinating consequence that the faster you move, the slower you age (move through time) relative to someone sitting still! Imagine that you can climb into a spaceship and pilot it at 95% of the speed of light for one year on your watch before coming back to Earth. When you get home, your family will all be more than three years older!

There is another enormous consequence. If something were to go faster than the speed of light, it would travel backwards (negative speed) through time. Faster than light particles would be time-traveling!

Before this startling result is accepted, several possible mistakes need to be checked for. Chief among these is the synchronization of several clocks: at the source of neutrinos, at the place where they are measured and a GPS satellite in space will all have to be checked. Then, other independent experiments will have to confirm the same finding. It could be that the rate it is moving (since faster moving things keep slower time) is throwing one clock out of time. Finally, there is the test of convincing scientists that a fundamental idea that they have cherished for a century is wrong!