#233 The Triumph of Lorentz

Dr. craig’s response

I hadn’t planned on doing back to back questions on time, but so many people asked about this potentially important development that it is irresistible. I actually did an audio-blog on this exciting news, but our sound equipment failed and so, for better or worse, I’ll address it here.

This is a very welcome development, confirmatory of the position I defended concerning the proper physical interpretation of the Special Theory of Relativity (STR) in my books Time and the Metaphysics of Special Relativity (Kluwer, 2001) and Einstein, Relativity, and Absolute Simultaneity (co-edited with Quentin Smith) (Routledge, 2007). It is a dramatic empirical confirmation of the physical interpretation of the mathematical equations of STR by the great Dutch physicist Hendrik Antoon Lorentz.

You see, a physical theory comprises a mathematical core and a physical interpretation of those core equations. The mathematical core of STR is the Lorentz transformation equations, which tell you how to calculate the spatio-temporal co-ordinates of an object relative to different frames of reference. But there are at least three different physical interpretations of those equations:

1. The original Einsteinian interpretation, which denied the existence of absolute space and time and envisioned physical deformations of 3-dimensional, physical objects enduring through time.

2. The Minkowskian interpretation, which denied the existence of 3-dimensional, physical objects enduring through time in favor of 4-dimensional objects existing tenselessly in spacetime. Once Minkowski proposed his spacetime interpretation in 1908, Einstein immediately abandoned his original interpretation for Minkowski’s, which has since become the standard textbook version of STR.

3. The Lorentzian interpretation, which like the original Einsteinian interpretation, affirmed the existence of 3-dimensional objects enduring through time but which, unlike the Einsteinian view, affirmed the existence of absolute space and absolute simultaneity, even if we cannot detect them empirically. Clocks and measuring rods in motion relative to the absolute reference frame (the “aether”) run slowly and shrink up as Einstein suggested.

These three interpretations have been until recently empirically equivalent, so that it has been impossible scientifically to choose between them. During the heyday of positivism, theories which were empirically equivalent tended to be regarded as just the same theory, despite the vastly different views of space and time they might involve, because there was no way to verify the differing interpretations. With the collapse of verificationism, philosophers of science are once more appreciative of the vast differences ontologically between the interpretations of Einstein, Minkowski, and Lorentz, differences that cannot be glossed over.

In recent years experimental results concerning the predictions of a quantum mechanical theorem called Bell’s Theorem have made the Lorentzian interpretation, so long ignored by the positivists, once more a serious option. John Bell himself, who formulated the theorem, advocated going back to Lorentz’s view, since the experimental results seemed to indicate the objective reality of relations of absolute simultaneity in the universe.

These most recent results at CERN continue this pattern. Let me explain.

STR does not really prohibit the existence of particles traveling at superluminal velocities. What it prohibits is the acceleration of a particle from subluminal velocity to superluminal velocity. But it doesn’t rule out particles which always travel at superluminal speeds. Indeed, there has been much discussion of such theoretical particles, which are called “tachyons” (from the Greek word for swift), even though none has yet been found. If these new results hold up, then these neutrinos are, in fact, tachyons, and somebody is probably in line for a Nobel Prize!

Now if tachyons are compatible with STR, then, you may ask, what’s the fuss all about? Just this: in the vocabulary of the Einsteinian interpretation of STR, simultaneity of distant events is relative to reference frames, which are the inertial frames of observers in relative motion. To determine the simultaneity of two spatially separated events, you send a light signal to a distant observer, who reflects it back to you. Assuming light’s velocity is the same both going and returning, you figure that the event simultaneous with the distant reflection event is the event at your location which is halfway between the time you sent the signal and the time you got it back. So you can draw a line of simultaneity, as it were, between those two events, and use that as the basis for figuring which other events in the two locations are simultaneous. This sounds fine; but it has the consequence that simultaneity becomes relative. For which event is halfway between the time you sent the signal and the time you received it back depends on the relative motion of the two observers. Observers at those same locations who have different reference frames will determine different events to be simultaneous. There is no absolute (i.e., frame independent) simultaneity.

But if tachyons exist, then you can send signals between the two observers faster than the speed of light. But then here’s the rub: that implies that relative to some reference frames, the tachyons will be going backward in time! For if there is no absolute simultaneity, some observers will draw the line of simultaneity between the two distant events in such a way that the tachyon is reflected back before it is even sent! Such behavior is pathological. This is what is in mind when it is said that faster than light particles would violate causality: an effect could occur (like the reception of a signal) before it is caused (the signal is sent).

The easiest and most natural way to avoid such pathological behavior is to say that the line of simultaneity drawn by the relatively moving observers is just wrong. The use of light signals to calculate simultaneity works only in the fundamental reference frame but not between relatively moving frames. In other words, Lorentz was right all along! If there do exist relations of absolute simultaneity, then there’s just no problem with faster than light signals. Indeed, if we had infinite velocity tachyons, we could use them to measure absolute simultaneity. The reason for the panic you sense in the press releases on the CERN results is that the scientists interviewed implicitly assume either an Einsteinian or Minkowskian interpretation of STR. But Lorentz would be rejoicing.

In fact, Lorentz himself predicted that something like this might happen. In 1913 he wrote,

According to Einstein it has no meaning to speak of motion relative to the aether. He likewise denies the existence of absolute simultaneity.

It is certainly remarkable that these relativity concepts, also those concerning time, have found such a rapid acceptance.

The acceptance of these concepts belongs mainly to epistemology . . . It is certain, however, that it depends to a large extent on the way one is accustomed to think whether one is attracted to one or another interpretation. As far as this lecturer is concerned, he finds a certain satisfaction in the older interpretations, according to which the aether possesses at least some substantiality, space and time can be sharply separated, and simultaneity without further specification can be spoken of. In regard to this last point, one may perhaps appeal to our ability of imagining arbitrarily large velocities. In that way, one comes very close to the concept of absolute simultaneity.

Finally, it should be noted that the daring assertion that one can never observe velocities larger than the velocity of light contains a hypothetical restriction of what is accessible to us, [a restriction] which cannot be accepted without some reservation.1

Here Lorentz clearly discerns the crucial role played by Einstein's verificationist theory of meaning and rejects it. In defense of absolute simultaneity, he appeals to the use of arbitrarily fast signals, even though they were not presently observable. He quite rightly expresses caution about our never being able to detect empirically such superluminal velocities.

Lorentz’s interpretation, like the original Einsteinian interpretation, presupposes an A-Theory of time. But it enjoys the advantage over Einstein’s interpretation in making the physical deformations suffered by objects in motion relative to the fundamental frame intelligible.

I hope you’ll forgive the triumphalism of my title for this Question of the Week. Lorentz is one of my scientific heroes. The results obtained at CERN may not hold up. But I sure hope that they do.