5 Minute Tute – The CERN discovery

What experiment has been conducted at CERN, and what are the findings?

In an experiment called OPERA, a beam of neutrinos was sent from CERN, near Geneva, 730km through the Earth’s crust to Gran Sasso, Italy. An important stage in the analysis of this data is to measure the arrival time of the neutrinos, which seems to be 60 billionths of a second earlier than if they were travelling at the speed of light.

So what?

According to Einstein’s Special Relativity, as a particle is accelerated towards the speed of light, some energy goes into its mass. This makes it increasingly difficult to push to faster velocities and impossible to go faster than light. Additionally, events can only communicate with each other if they are linked by the speed of light. Both of these laws would be violated, by neutrinos at least, if the findings are accurate.

What exactly does it mean to say that the neutrinos may have passed through another dimension?

We experience daily life in three spatial dimensions and one temporal dimension. It is, however, possible to add extra spatial dimensions when making models in theoretical physics. Think of this in terms of looking at a lamppost from far off.  At first it appears to be just a line, but as one gets closer the width can be seen and then finally the third dimension can be seen in the curvature of the surface. It could be that more dimensions exist but we just haven’t looked close enough. Extra dimensions could give the neutrinos a way of taking a short cut between two points in our three spatial dimension world. This would look like the neutrinos have travelled faster than the speed of light.

How could these results change our understanding of cause and effect, or make time travel feasible?

The difficulty with developing direct practical applications from neutrinos stems from their weak interaction with matter. Take the OPERA experiment itself, where a beam of particles was able to travel through 730km of rock. So we’re not going to be going on any new types of journey through space and time just yet! However, if we could develop a neutrino communication device, it could be possible to send messages such that they appear to the receiver to have arrived before they were sent.

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If no one can falsify CERN’s results, what next for physics?

Despite this being a ground-breaking observation I don’t think it would be the case of throwing every undergraduate physics textbook out of the window! Physics is a science of approximations. For instance, it is possible to calculate the trajectory of a projectile on the Earth’s surface using Newton’s Law of Gravity – but move close to a black hole and we have to use Einstein’s Equation of General Relativity. With this in mind, any new theory that explains OPERA’s result must also account for the wealth of high precision measurements that agree well with our current theory.

Dan Short is a 4th year DPhil student in Particle Physics working on the ATLAS experiment at CERN (one of the experiments on the Large Hadron Collider)