The Particle That (Kind of) Broke Physics

Written by Emily Mazo

In late September, the OPERA experiment based in Italy’s Gran Sasso Laboratory, which observes a neutrino beam from CERN in Geneva, Switzerland, released observations of neutrinos traveling at 20 parts per million above, just slightly faster than, the speed of light. This announcement seemed to fly in the face of one of the 20th century’s greatest scientific feats, Albert Einstein’s theory
of special relativity. Special relativity is based on two postulates, that the laws of physics are the same for all who observe them and are in uniform motion relative to each other, and that the speed of light in a vacuum is the same for all who observe it, regardless of their motion or the motion of the source of light. From these postulates, it is concluded that the speed of light is the maximum speed; because photons, light particles, have no mass, and no object with a mass can travel faster than photons.

The neutrinos traveling from CERN traveled 732 km straight through the earth, at a maximum depth of 11.4 km below the earth’s surface. Neutrinos can pass through matter such as the earth’s crust without being absorbed. Neutrinos have close to zero mass, but they still have some, and therefore OPERA’s observation of neutrinos traveling at faster than the speed of light might have a huge impact on physics.

We have to say, “might” because of the uncertainty of the experiment’s observations. Although the scientists at CERN and Gran Sasso have measured the distance between the two laboratories precise to 20cm, and were equally precise about all other measurements that may have had an impact on their data, they are still searching for an explanation for their observations that does not rest on “we broke special relativity”.

However, lets assume that some of the most precise instruments in the world did not make a mistake. Would this discovery affect our physics classes? What would this discovery mean for physics at the high school level?

Probably nothing. Keep in mind; even if certain objects can move faster than the speed of light, the speed of light will not change. High school level physics classes do not deal with special relativity beyond knowing that c is equal to the speed of light, and that the speed of light in a vacuum is always the same.

But does this observation actually affect Einstein’s theory of special relativity?
The Economist suggests, “The neutrinos are (likely) taking a short-cut through one of the extra dimensions which string theory postulates are hidden among the familiar four of length, breadth, height and time.”

For example, the superstring theory suggests 10 or 11 dimensions. Special relativity is relevant in the four dimensions we observe, but if the neutrinos observed in the OPERA experiment were making use of other dimensions, it may not have an impact on the understanding of special relativity. However, it could still have a large impact on theoretical physics.

String theory consistently combines the ideas of general relativity and quantum field theory, and agrees with concepts created in the field of quantum gravity. It claims that the particles that make up matter are not zero-dimensional, point-like, in that they have no size or shape, but are one-dimensional strings that oscillate.

Superstring theory proposes that there are two types of such particles, bosons, two of which can occupy the same state at the same time, and which transmit forces, and fermions, two of which cannot inhabit the same state at one time, and which make up all matter.

The Pauli exclusion principle describes why we cannot put our hands through walls without breaking them, because two fermions, matter, cannot occupy the same space the way bosons, forces, can. We learn about this in chemistry when we use it describe why no two electrons of a given atom can have the same four quantum numbers, because they can not occupy the same quantum state.

Now remember that we said neutrinos could pass through the earth’s crust. This does not mean that they are bosons and can occupy the same quantum state as another particle.

Neutrinos are fermions, but have no electric charge, and are therefore not affected by the electromagnetic forces that act on electrons. However, string theory would require several extra dimensions, other than the four we observe.
It is possible that subatomic particles such as neutrinos can be making use of these extra dimensions in their motion. This may explain the observed motion of neutrinos between CERN and Gran Sasso. If neutrinos really can move at a speed faster than that of photons, evidence may be lent to string theory and possibly lead the way to the discovery of a Theory of Everything, something that would make Einstein salivate.

Accepting that the neutrinos have not in fact broken special relativity, and have actually given proof to a concept of string theory would be huge. Stephen Hawking has said that M-theory, which is an extension of string theory “is the only candidate for a complete theory of the universe.”

A Theory of Everything would completely describe forces and matter mathematically. Such a theory is the holy grail of physics.

The media was very quick to accept the findings of the OPERA experiment. Many scientists however are dismissing them as systematic error. Although this observation of neutrinos acting funny could lead to discoveries or proof of super symmetry or, in fact, a unified theory of everything, scientists are showing a healthy amount of skepticism.

Even the OPERA paper presenting its findings states that the researchers will continue to “investigate possible still unknown systematic effects that could explain the observed anomaly.”

This could be because no one wants to get caught with egg on their face if or when the findings of OPERA are found to be due to error, or perhaps because no one wants to get their hopes dashed after dreaming about the implications of such a finding.