The scientific world has been shaken by developments in the OPERA (Oscillation Project with Emulsion-tracking Apparatus) collaboration. Researchers from over 48 different institutions across the world have recorded neutrinos travelling 60 nanoseconds faster than the speed of light in a vacuum between a source and a detector.
This finding could overturn one of the most fundamental laws in modern physics - that nothing travels faster than the speed of light.
Neutrinos are fundamental particles with a very small mass, and are electrically neutral, meaning they rarely interact with other matter. Billions of neutrinos pass through the Earth every second. The majority of neutrinos that pass through the Earth are generated in the sun, but they can also form from the decay of radioactive elements such as U-238, found in nuclear reactors, supernovas, and, as happened in the OPERA experiment, particle accelerators.
Using a detector situated 1400m underground in the Gran Sasso National Laboratory in Italy, the OPERA experiment was designed to study a beam of neutrinos produced 731km away at CERN (the European Organisation for Nuclear Research) in Switzerland. The results appear to be accurate. Neutrinos travelling faster than the speed of light have been recorded for more than 16,000 events in the last two years. The OPERA collaboration seem confident in their results thanks, in part, to new methods using Global Positioning System (GPS) technology to synchronise the clocks at CERN and Gran Sasso, and also by using GPS to get an accurate measurement for the distance between the source of the neutrinos and the detector.
Previous experiments which have attempted to find particles travelling faster than the speed of light have come away empty-handed. A pulse of neutrinos generated in a nearby supernova (exploding star), and the flash of light seen from the supernova, for example, arrived within hours of each other. If all neutrinos can achieve faster than light speeds then the neutrino pulse should have arrived years before the flash of light. Since the results were announced in September many have sought to explain the observations or find fault with the method used by the OPERA group. Whether the clocks at the source and the detector have been synchronised correctly is a key issue. One suggestion is that gravitational pull at CERN is stronger than at Gran Sasso, meaning, according to Einstein's general theory of relativity, clocks at CERN would run slower than in Italy.
Many more ideas are likely to surface in the coming months. The law that nothing travels faster than the speed of light, the cornerstone of Einstein's theory of relativity, is crucial for most physics developed since 1905. If it is found that neutrinos can travel faster than the speed of light, this would force us to rethink many areas of science. Changes in science, both in what we know, and in how science is done, occur for three main reasons. One is changes to the technology available to investigate problems. The OPERA experiment used more accurate methods of measuring time and distance than have been available in the past, so it may mean that this is the first opportunity we have had to measure neutrinos travelling faster than the speed of light.
Secondly, who controls technology is important - both in how it gets used and whether it gets developed in the first place. The potential for a new technology to improve the world, for example renewable energy, doesn't necessarily mean that it is developed, if, for instance, it isn't in the interests of capital to do so.
Finally, the drive to gain a better understanding of the world can also bring about changes to science. This means going beyond the dominant ideas at the time, and coming up with new theories that may not immediately be apparent. To explain the observations seen in the OPERA experiment may mean rethinking what we currently understand. And new theories may have to be developed if what we thought to be the laws that govern the way the universe works are found to be broken on some occasions.
Whether this latest result will lead to a rewriting of physics or is just due to an overlooked factor is currently unknown. It does, however, give us a useful reminder that our understanding of the physical world is not complete and that we should not be afraid of new discoveries which may completely overturn what we currently know.