Faster than the speed of light?

Major news channels such as the BBC are reporting a seemingly incredible result from the Large Hadron Collider (LHC) - in case you have been living at the bottom of a coal mine for the last few years and haven't heard of this amazing machine it is the largest particle accelerator ever built by mankind. 

One of the huge detectors at the LHC - notice the person standing lower center     (Image credit CERN)

It consists of a circular underground tunnel, 17 miles in circumference, which contains an evacuated (i.e. has no air in it) tube, around which sub-atomic particles such as protons can be fired.

As they whizz their way round and round the tube they are steadily accelerated by huge superconducting magnets (magnets operating at temperatures so low that they have virtually no electrical resistance and can therefore sustain huge magnetic fields). This allows the particles to be taken up to speeds very very close to the speed of light (no particle with mass can ever reach or exceed the speed of light - well, that's what Einstein told us and we have always believed him, until now at any rate, but more of that later). 
There are actually two bunches of these particles, each bunch travels in opposite directions around the LHC, a bit like two trains going round and round in circles but each on slightly different tracks. Once the scientists are ready for their experiment to actually begin they cause the two particle groups to collide - it is as if someone switched a signal on the train tracks and caused the mother of all head on collisions.

The first recorded neutrino collision

This collision causes the particles to crash head on into each other and annihilate in a huge (by sub-atomic standards anyway) flash of energy. As dear old Albert told us, E=mc^2 - that is to say the energy which a particle (be it a proton or a porpoise) has by virtue of its mass is equal to the mass of the object times the square of the speed of light. Now the speed of light is by itself a pretty large number (around 300 million meters per second or about 671 million miles per hour!) so you can imagine that squaring this number (multiplying it by itself) gives an utterly humungous figure for E. This large value of E is the reason that atomic bombs produce such massive amounts of energy, the conversion of even a tiny amount of matter directly into energy gives a huge net energy output.
So, back in the LHC this collision produces energy and a shower of particle fragments flying every which way. Some of this energy can turn directly back into matter, but often matter of a totally different nature to the protons we started with.

Albert Einstein before he became rich, famous and crazy!

This is ultimately the whole point of the LHC (and other similar, albeit smaller colliders the world over). It is like taking two pieces of rock and banging them together to see what is inside, it is only by smashing stuff up at this level that we can find out what the Universe is actually made of. 
The analogy with rocks is flawed in that rocks don't spontaneously change into bananas when they are broken apart by collision with each other, but the sub-atomic (or 'quantum') world  is so strange by everyday standards that analogies seldom tell the full story. You just have to accept the word of a lot of people much much smarter than you and I who have been doing this stuff for a long time.
One of the side experiments which they have been running at the LHC for the past couple of years involves sending a beam of neutrinos (very light, very fast sub-atomic particles) from one place to another. The original point of this was to investigate the way these neutrinos can spontaneously change from one type to another along the way (told you the quantum world was weird). As a by product of this experiment, by very carefully measuring the time taken to travel from one place to another, and by very accurately measuring the distance between the two locations, physicists are able to measure the speed of the neutrinos. They were therefore more than a little shocked to find out that it appears as though the neutrinos are travelling ever so slightly faster than the speed of light.
One of the cornerstones of modern physics is the assertion, first made by Einstein, that nothing with any mass can travel at or above the speed of light, no way, not ever. This 'cosmic speed limit' has become utterly entrenched in modern physics, in fact most of reality as we know it depends on this fact being true. If it were not, you would theoretically be able to see events before they had actually taken place - is your head hurting yet?
So there are four possibilities here: 

• Albert had it wrong all those years ago
• The piece of string the physicists used to measure the length of their experiment was a bit shorter than they thought
• The physicists should not have bought their stopwatch at Wal-mart
• Albert was mostly right but the neutrinos are doing some new and funky stuff that we have never seen before

Personally my money is on the last possibility, but only time will tell. The scientists have published their findings because despite having checked and rechecked their results until their brains are ready to explode (and that takes some doing for physicists) they can't find any error in their analysis. They are hoping that releasing this information to the larger scientific world may let someone else come up with a reasonable explanation i.e. they cocked up their calculations and we can all breathe a sigh of relief because Einstein is still the biggest smartass who ever lived.
Alternatively they have discovered something new and utterly amazing, in which case everything we thought we knew about everything is utter codswallop and we need to go back and start all over.
Only time will tell, keep reading this blog to find out...


Dave


LHC breaks lightspeed barrier?