Was Einstein Wrong? That’s the Wrong Question

This week, the 2011 Nobel Prizes will be announced. Like many scientists, I have mixed feelings about the Nobels: they often do acknowledge important research, but the selection process is not transparent and the decisions can often seem arbitrary when so much excellent work is being done. (I’m focusing on the science prizes; the literature and peace prizes are a different animal, and I haven’t really pondered them as much.) If the Thomson Reuters prediction for the physics prize is correct, I’ll definitely have something to say about it on Wednesday — quantum entanglement is a topic I’ve intended to write about for some time, and I do hope the experimenters who have done great work in that field get the honor. Update: the Nobel Prize obviously wasn’t on entanglement, but something closer to my own heart.

On the other hand, the Nobel Prizes do help perpetuate the idea that there are a few Great Scientists worthy of honor, and while the awards are intended to support people actively doing work, the prizes select those who have already established themselves. The problem is that science is complex, and it may be many years before the full significance of a particular piece of research can be recognized — by which time the researcher may be dead (Nobels are generally not given out posthumously, though there are exceptions) or moved on to other projects. (An odd example of this is Brian Josephson, who predicted the superconducting junctions that now bear his name; by the time he received his Nobel Prize, he was devoting his life to pseudoscientific research on parapsychology, telepathy, and the like.) I guess I would prefer to see more prestigious prizes given out to younger researchers in their early careers, but the Nobels are what they are. Funny how nobody consults me on these matters.

The emergence of importance in scientific research brings us back to the possibly faster-than-light neutrino results from OPERA. As more and more scientists weigh in on the possibilities, the idea that the neutrinos are actually moving faster than light seems less plausible. Andrew Cohen and Sheldon Glashow (the latter a Nobel Laureate) pointed out that neutrinos moving faster than the speed of light in a material would produce radiation; the energy of the radiation has to come from the kinetic energy of the neutrinos, so they slow down. For charged particles such as electrons, a similar phenomenon is known as Čerenkov (pronounced “chairENkoff”) radiation, but the lack of electromagnetic interaction in neutrinos in some ways makes the effect simpler.

According to quantum field theory, the vacuum is full of possible particles; for neutrinos, traveling through a medium like the crust of the Earth (as in the OPERA experiment) doesn’t actually change the situation much because the neutrinos interact so weakly with matter. Under ordinary circumstances, these virtual particles don’t ever become more than possibilities, but when something moving faster than the speed of light in that medium passes through, the shock wave is enough to make them real. The most interesting possibility discussed by Cohen and Glashow is pair-production: an electron-positron pair.

Production of an electron-positron pair by a neutrino moving faster than the speed of light. Note the relative length of the arrow representing the neutrino's velocity before and after the pair production. (The electron is e-, the positron is e+, and νμ indicates a mu neutrino like the ones in the OPERA experiment.)

A mu neutrino moving faster than light creates shock waves in the quantum vacuum; these shock waves are above the threshold energy to make an electron and a positron, via Einstein’s famous equation E = m c2. You can’t just make an electron or a positron in isolation, since you need to conserve a number of physical quantities, including electric charge and spin, so the energies involved have to be very large. (Neutrino-antineutrino pairs have a lower energy threshold, but since the neutrino flavors are expected to move at more-or-less the same velocity, it’s not an important process for the discussion at hand.) Transferring that much energy from the neutrino to the electron-positron pair slows it down a lot, so even if the neutrino initially had that much velocity, it would quickly drop below light speed.

As I mentioned in the earlier post, neutrinos aren’t tachyons (hypothetical particles that always move faster than light): that seems evident from Supernova 1987a and other observations. The Cohen-Glashow calculation I think shows pretty clearly why neutrinos aren’t slower-than-light particles that occasionally violate the speed limit set by special relativity. (If that ever occurs, it would be a Lorentz violation, and very few reputable theories allow for this kind of behavior. The name is from physicist Hendrik Lorentz worked out a lot of the math behind relativity before Einstein’s final version came out in 1905.) That leaves two possibilities still: new physics that leaves special relativity in place for nearly every phenomenon we know of, or there is something wrong with the OPERA analysis.

Note that Einstein’s name popped up a couple of times, but it was almost incidental. I think it’s pretty clear from history that relativity would have existed without Einstein, and certainly he didn’t work out all the implications of his own theories. In other words, it’s a big mistake to think of experiments such as this as being a battle with the old guy. So many headlines over the last 10 days have framed the whole issue as “Einstein vs. OPERA”, asking “Was Einstein Wrong?”, but that’s completely the wrong question to ask. Einstein was wrong about many things, and “right” about others, for a certain value of “right”. Over a period of centuries, we’re all going to turn out to be wrong about most of what we think. Newton was wrong in many ways: absolute nature of time and space, the need to “rewind” the mechanism of the Solar System, etc., and that doesn’t even get into his alchemy and numerology. Yet, much of Newtonian physics is useful, and essential for handling everyday problems.

The right question is whether the OPERA results are consistent with what our theories predict, and if not, why not. Relativity has held up under every test so far, so any exception we find is going to be on the hairy edge of what we can do experimentally. It’s not an all-or-nothing proposition, as the analyses I’ve written about and linked to show. Maybe there are exceptions to Einstein’s theories; maybe there aren’t (though that seems unlikely based on history). Whatever the ultimate outcome to the OPERA neutrino experiment turns out to be, it’s a good illustration of how science actually works: scientists eliminating options, figuring out others, testing propositions, and coming out with a clearer picture of our wonderful universe.

25 Responses to “Was Einstein Wrong? That’s the Wrong Question”

  1. 1 William Tatum (@Orwelian84) October 3, 2011 at 14:56

    This may be a stupid question, I freely admit I am just a layperson.

    Is it possible that neutrinos are larger particles in some other dimension close to ours and what we perceive as straight line movement is not straight from the particles frame of reference, and therefore not traveling faster than the speed of light? E.g we perceive a stair-step like pattern where the neutrino appears follows the plane of the each of the steps, e.g a 2d straight line, but its actually moving in a slope tangent to each vertice?

    • 2 Matthew R. Francis October 3, 2011 at 15:43

      Neutrinos being able to move into (hypothetical) extra dimensions is one possible resolution to the problem. Neutrinos are not any bigger (size is a weird concept in quantum physics anyway), but under certain conditions can take a “shortcut” through dimensions not ordinarily accessible to particles. So, in that scheme, they would always move slower than the speed of light (therefore obeying relativity), but they would be following a path not directly accessible to our experiments.

      Which of course is a problem in a way: for an idea to be testable, we need to access that extra dimension somehow. I’d like to see specific calculations done; every argument I’ve seen is somewhat on the hand-waving side of things.

  2. 4 Don Wells October 3, 2011 at 15:47

    On pp.85-86 of the October 1st (current) issue of The Economist, there is an article titled “So long, and thanks for all the quarks”, whose primary subject is the final power-down of the Tevatron at Fermilab three days ago. But the discussion transitions into Fermilab’s likely role in the future of neutrino research, and the obvious relation to the OPERA superluminal neutrino report. After discussing the international politics of proposed big-physics projects, the last words of the article, on p.86, are this fascinating comment:

    “..in their heart of hearts, even the skeptics who say that they think the result from OPERA must be a mistake hope that it is not.”

    My guess is that the anonymous Economist reporter is quoting some physicist’s remark in that sentence.

    • 5 Matthew R. Francis October 3, 2011 at 17:00

      I will quibble with the writer’s assertion that I “hope this is not a mistake”: I still think this will turn out to be an error. However, the principle is still sound: I do want to see new physics cropping up. I admit anything that blacks the eyes of people who believe in superstrings or supersymmetry makes me happy, but that may be my personal perversity.

  3. 6 Albert Zweistein October 3, 2011 at 17:38

    It is true that the ideas underlying Special Relativity were “in the air” in the early 1900s. Lorentz figured out the needed transformations and Poincare toyed with the idea of relativity, but did not develop it into a mature conceptual framework. Einstein did that. Perhaps someone else would have figured it out if AE had not.

    This is NOT the case with General Relativity!

    When Einstein told Planck about the new theory for gravitation he was working on, Planck said he was almost certainly wrong, and even if he were right, no one would believe him because Newtonian gravitation was virtually sacrosanct.

    Once Einstein showed them the way, Hilbert and others were able get there too. But without Einstein there would have been no path to General Relativity in the 20th century. GR was AE all the way, with help from several others on the math.

    • 7 Matthew R. Francis October 4, 2011 at 08:27

      Einstein was decidedly ahead of the curve on general relativity, but to say he’s the only one who ever could have done it? I’m not so sure. Weyl, Klein, and others were thinking geometrically, and even Clifford and Riemann had the beginnings of that idea in the 19th century. We’re constrained by how things turned out, so it’s hard know how things might have been. However, I don’t believe in the idea of the Unique Genius. History is contingent; no doubt general relativity would have looked different, and may have taken longer, but eventually someone would have worked out the framework.

      I don’t say this to impugn Einstein, of course! As you point out, Poincare didn’t go as far as Einstein with special relativity (and a lot of the implications of Poincare’s work have taken a century to sort out, especially with regard to chaos theory), and general relativity stands as his greatest scientific achievement. I say this as someone whose research involves relativity. It was a towering accomplishment.

  4. 8 mahesh khati October 17, 2011 at 14:39

    Before 23 years, I had already proved that relative velocity may be more than light. This is experimentally proved by faster than light neutrinos in CERN. That paper “what is matter & dark matter made up of?” is already on my web site http://www.maheshkhati.com. Please read it. That also salve the misty of dark matter & true relativity.

  5. 9 vaggelis talios October 20, 2011 at 18:48

    Einstein’s theories of relativity was never right.

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