Neutrinos, the most ghostly particles we know of, are hitting far above their weight class. Recent evidence from the European physics mecca known as CERN, and an affiliated group in Lyon, suggests that neutrinos, tiny subatomic particles with almost no mass, travel slightly faster than the speed of light. If this evidence is replicated by other teams it will definitively up-end one of the pillars of modern physics: Einstein’s theory of special relativity.
Special relativity is a theory about the nature of space and time and is today widely considered to have replaced earlier more naïve notions of space and time advocated by Newton and many others.
Explaining special relativity is generally viewed as a very difficult task. The essentials can, however, be explained rather simply. A basic assumption that Einstein used in crafting his theory was that the speed of light, apparently the fastest speed possible in our universe, is constant for all observers. This assumption was based on experimental evidence from the 1887 Michelson-Morley experiment, and other sources, that the speed of light seemed to be constant no matter how fast or in what direction the observer was moving.
This is a highly counter-intuitive notion because in our regular life all things seem to change speed as the observer’s speed changes. For example, a train passing by as I sit at a station has a certain speed in relation to me, let’s say 100 miles an hour. But if I am in a car next to the train driving at 60 miles an hour in the same direction as the train, the train is now traveling at 40 miles an hour in relation to me in the car. Speeds are generally entirely relative.
The speed of light was, for Einstein, different than all other speeds. It was absolute and constant no matter how fast the observer was moving. Speeds are by definition measured in units of distance divided by time – such as miles an hour or kilometers per second. If we accept that the speed of light (186,000 miles per second) is constant, we see quickly that space and time must become malleable and not constant. That is, the “miles” or “seconds” in the speed of light must change if the figure of 186,000 is to remain constant for different observers, as Einstein postulated. This is the essence of the theory of special relativity: Space and time are malleable but the speed of light is absolute and constant.
Let’s take an example. If I were to measure the speed of light in a lab, with very accurate equipment, I would get the answer of 186,000 miles per second. And if I measure the speed of light from nearby stars from the point of view of our planet as it moves in orbit around the Sun toward those nearby stars, I will get the same answer. What happened? Why isn’t the speed faster because we are, with our entire planet, moving toward the source of light?
Well, according to special relativity, time and space shifted such that the speed of light remained constant. More specifically, the faster objects travel, the slower time proceeds from the perspective of an observer in that reference frame, a phenomenon known as “time dilation.” And as objects travel faster they become shorter in the direction of motion as space itself contracts (“length contraction”). These are necessary consequences of the assumption that the speed of light is constant for all observers: Time and space become malleable.
Relativity theory does not, then, hold that all things are relative. Whereas previous theories like Newton’s subscribed to notions of absolute space and absolute time, Einstein flipped orthodoxy on its head and suggested instead, based on the best empirical evidence at the time, that the speed of light is in fact absolute and everything else is relative.
A slow revolution is underway, however, that may demonstrate Einstein’s assumptions, and thus his theories, to be wrong – or at least incomplete.
Alain Aspect and his colleagues in France showed, starting in the 1980s, that “entangled” quantum particles can communicate either instantaneously or near instantaneously. This now well-established experimental phenomenon – known as “non-locality” or “entanglement” – showed that Einstein’s assumption that the speed of light is constant for all observers and is a cosmic speed limit is wrong in at least some circumstances. The phenomenon is called non-locality because it seems to violate the even more well-established principle that every action must have some proximate cause, not a distant cause without any apparent mechanism
Since the original Aspect experiments, many other experiments have been conducted, with increasing rigor and accuracy. In 2008, a Swiss team led by physicist Daniel Salart, confirmed entanglement and faster-than-light effects over a distance of 18 kilometers, in an experimental setup that makes alternative interpretations difficult. Salart calculates that the apparent information transfer between entangled particles is at least 10,000 times the speed of light.
Even if we can’t ever use entanglement, and the apparent faster-than-light information transfer, to influence distant events (through “signals” in the technical sense), the Aspect and Salart experiments seem to have already up-ended Einstein’s interpretation of relativity theory by demonstrating that the universe itself does allow causal influence to travel faster than the speed of light.
At the least, it is clear the speed of light limitation that forms one of two key assumptions in special relativity has been falsified. And without the relativity of simultaneity or the faster-than-light prohibition, there is no Einstein/Minkowski interpretation of the theory of relativity. Rather, we have substantial evidence for an earlier version of relativity advocated by one of Einstein’s mentors, the Dutch Nobelist Hendrik Lorentz.
This conclusion is far from the mainstream at this time, however, in part because the Aspect and Salart experiments themselves are still being debated in terms of their correct interpretation, and because of the many decades of entrenched acceptance of the validity of Einstein’s theories of relativity. The new neutrino evidence will surely add much heat to this fire.
Given the Aspect and Salart experiments, the more recent neutrino evidence (which may turn out to be inaccurate), and the very basic philosophical problems with relativity theory, it seems to me that we are in the middle of a slow shift away from the Einstein/Minkowski interpretation of relativity and the consensus will eventually shift back toward a Lorentzian approach. Arrhenius, the Swedish physicist who wrote the Nobel Prize award letter given to Einstein in 1922, may have been correct when he stated in that letter that relativity theory “pertains essentially to epistemology.”
While still very much a minority position, we find some support for this view in the writings of physicists and philosophers of physics. Lee Smolin, a well-known physicist at the Perimeter Institute in Canada, stated in an email to me in 2009: “I would say that this point of view [the Lorentzian interpretation] is taken as a logical possibility by a number of thoughtful theorists, although the number who advocate it is fewer.” Smolin is not himself an advocate of the Lorentzian view.
J. S. Bell, the colorful Irish physicist who formulated the Bell inequalities, which formed the theoretical basis for Aspect’s non-locality experiments, was a supporter of the Lorentzian view. He stated in a 1986 interview with physicist Paul Davies:
“[T]he pre-Einstein position of Lorentz and Poincare, Larmor and Fitzgerald was perfectly coherent, and is not inconsistent with relativity theory. The idea that there is an aether … is a perfectly coherent point of view. The reason I want to go back to the idea of an aether here is because … the suggestion that [in nonlocality experiments] behind the scenes something is going faster than light. Now if all Lorentz frames are equivalent, that also means that things can go backward in time … [This] introduces great problems, paradoxes of causality, and so on. And so it is precisely to avoid these that I want to say there is a real causal sequence which is defined in the aether. ”
Yuri Balashov, a philosopher at the University of Georgia, stated in a 2000 paper in the Journal of Philosophy:
“[T]he idea of restoring absolute simultaneity [the basis for the Lorentzian interpretation of relativity theory] no longer has a distinctively pseudo-scientific flavor it has had until very recently. It is a well-known fact that one could accept all the empirical consequences of SR (including length contraction, time dilation, and so on) and yet insist that there is a privileged inertial reference frame, in which meter sticks really have the length they have and time intervals between events refer to the real time.”
A last point I’ll mention is that the holy grail of modern physics, the unification of relativity theory (the physics of the large-scale) and quantum mechanics (the physics of the small-scale), may be much easier if we recognize that Einstein’s relativity theories are lacking. David Bohm, an American physicist who made contributions in many areas of physics, including quantum theory, stated with respect to unification in his book, Wholeness and the Implicate Order:
“[R]elativity theory requires continuity, strict causality (or determinism) and locality. On the other hand, quantum theory requires non-continuity, non-causality and non-locality. So the basic concepts of relativity and quantum theory directly contradict each other. It is therefore hardly surprising that these two theories have never been unified in a consistent way. Rather, it seems mostly likely that such a unification is not actually possible. What is very probably needed instead is a qualitatively new theory, from which both relativity and quantum theory are to be derived as abstractions, approximations and limiting cases.”
Einstein/Minkowski relativity will always remain an interesting and very useful theory advocating a particular epistemological point of view. But it will, under the view I’m promoting here, not be our best theory of space and time.
I won’t, however, be at all surprised if the recent neutrino evidence will be found to be inaccurate. But even if this data is invalidated, we already have enough data from numerous entanglement experiments to state that special relativity has been falsified. This truth simply hasn’t sunk in to the physics community yet, for a variety of reasons that seem to relate more to sociology, psychology, and politics than science as it is ideally practiced.
(For brevity and simplicity I have kept the discussion to special relativity and not touched on general relativity, which is an extension of special relativity to all frames of reference regardless of motion. When it comes to unification, however, the discussion must focus on general relativity because this is our current theory of gravity, as opposed to special relativity, which does not incorporate gravity.)