Too soon to say modern physics turned on its head
Einstein's special theory of relativity, a central pillar of modern physics, has come under serious challenge, with far-reaching implications for everyone on the planet - and possibly beyond it.
It says nothing in the universe can go faster than the speed of light. But now, at least two experiments at the European Organisation for Nuclear Research (Cern) have found that subatomic particles called neutrinos may do so.
The second experiment was conducted to correct a potential error, and it confirmed the validity of the first. In both cases, the particles were sent 730 kilometres through a tunnel from the Cern laboratory in Geneva to the Gran Sasso laboratory in Italy. They arrived 60 billionths of a second faster than the speed of light.
Since the speed of light is 299,792,458 metres per second, the neutrinos were travelling at 299,798,454 metres per second - 5,996 metres per second faster than the speed of light. In the first experiment, at 10.5 microseconds (millionths of a second), the proton pulses used to generate the neutrino pulses were relatively long. Scientists could not know for sure whether individual neutrinos received at Gran Sasso corresponded to protons early or late in the proton pulse, creating uncertainty around their travel time.
In the second experiment, shorter proton pulses - lasting just 3 nanoseconds (billionths of a second), less than one-three-thousandth the length of the earlier test - were generated. A similar level of statistical significance to the first experiment was achieved.
Special theory is founded on the principle that the speed of light is the upper limit of how fast anything can travel. Einstein's celebrated equation E=mc2 states that energy (E) and mass (m) are equivalent, and can be converted from one to the other by the ratio 'c-squared', where 'c' represents the constant speed of light. The status of the speed of light as the ultimate cosmic speed limit is the reason that it's present in the seminal formula. But if 'c' is not the fastest possible speed and things can go faster, life would be very different.
Theoretically, if something can travel faster than light it can travel backwards in time.
An 'effect' could travel back to a point before its 'cause' had occurred - for instance, a golf ball flying off before it was hit. This would violate the fundamental law of causality: cause precedes effect.
If neutrinos do go faster than the speed of light, imagine yourself riding on one that is rocketing off into the universe. Everything that has happened on earth since the beginning of time is like a movie that is continuously being broadcast into the universe at the speed of light. Going faster than the speed of light, you on the neutrino will be able to catch up on this unfolding history and witness events that happened way before your own current existence and running backwards in time ... perhaps an actual battle in the opium wars, or your father's first date with your mother. Back to the future will not be just a movie title. The implications of the Cern finding, if correct, will turn modern physics on its head. Even the scientists there have conceded that the experiment has to be replicated in many laboratories all over the world before the result can be accepted.
So what are some plausible explanations for this earth-shaking result? The most obvious one is that there were flaws in the experiment. Physicists can claim success in an experiment if the chances of their result being a fluke of statistics are greater than five standard deviations, or a chance of less than one in a few million. In the initial experiment, the Gran Sasso team's result is six standard deviations. Although a second experiment confirmed the result of the first, questions continue to be raised.
In fact, another team at Gran Sasso now claims that their measurements of the neutrinos' energy on arrival contradict the faster-than-speed-of-light finding. They argue that the neutrinos pumped down from Cern should have lost most of their energy if they had travelled at even a tiny fraction faster than light. But in fact the neutrino beam as tested in their equipment registered an energy spectrum fully corresponding with what it should be for particles travelling at the speed of light and no more. Laboratories around the world will be conducting experiments to validate the result for a long time before a definitive conclusion can be made.
A possible explanation is that the ability to travel faster than the speed of light is unique to neutrinos. First postulated by Wolfgang Pauli in 1930, a neutrino's properties are still not completely understood. In 1985, Alan Kostelecky, a theoretical physicist at Indiana University, predicted that neutrinos could travel faster than light by interacting with an unknown force field. In the 1960s, some physicists theorised that particles that can travel faster than light, dubbed tachyons, may exist. But many physicists did not take tachyons too seriously since these particles have never actually been detected and may violate the rule of causality.
The Cern experiment may show that violating causality could be permissible for a certain class of subatomic particles. Another possibility is that, as the science historian Thomas Kuhn has noted, progress in science is a process of discrete paradigm shifts. As new theories such as Einstein's theory of relativity and quantum mechanics are discovered, they explain a larger class of events that cannot be explained by Newtonian physics.
In the physics of subatomic particles, a paradigm shift is occurring in the investigation of their behaviour that cannot be explained by the previous approach. String theory and Stephen Hawking's M theory of everything postulate that in addition to the four dimensions of space plus time, there are seven more dimensions that are hidden from the universe we experience. Neutrinos and some yet-to-be-discovered subatomic particles, under special circumstances, may be able to tunnel from one point to another via some of the other seven spaces, a cosmic short-cut in some hidden dimension, resulting in their travelling faster than light.
So before Einstein rolls over, much work needs to be done.
Tom Yam, a Hong Kong-based management consultant, holds a doctorate in electrical engineering