Faster-Than-Light Neutrinos? Physics Luminaries Voice
Doubts

     We asked a number of physicists for their reaction
     to the announcement of neutrinos breaking the
     cosmic speed limit

By John Matson  |
September 26, 2011
http://www.scientificamerican.com/article.cfm?id=ftl-neutrinos

A few dozen nanoseconds, an imperceptibly slim interval
in everyday life, can make all the difference in
experimental physics. A European physics collaboration
made a stunning announcement September 23, after having
clocked elementary particles called neutrinos making the
underground journey from a lab in Switzerland to one in
Italy. The neutrinos made the trip 60 nanoseconds faster
than they would have traveling at light speed, the
researchers found. Faster, that is, than the rules of
physics as we understand them would allow.

If confirmed, the results from the OPERA (Oscillation
Project with Emulsion-tRacking Apparatus) collaboration
would be huge, a once-in-a-lifetime revolution in how we
understand the universe. But there are plenty of reasons
to believe that Albert Einstein's long-reigning theory
of relativity will survive this challenge, as it has
withstood so many in the past. (Read more about
challenges to relativity in this article.)

That is the opinion of a number of physicists we
contacted, many of them on Scientific American's board
of advisers. Their reactions to the OPERA announcement
appear below.


Astrophysicist and cosmologist Martin Rees of the
University of Cambridge

     Extraordinary claims require extraordinary
     evidence. I think it will be perceived in
     retrospect as an embarrassment that this claim
     received so much publicity-the inevitable
     consequence of posting a preprint on the Web.
     Neutrinos were observed from SN 1987A more or less
     coincidentally with the explosion-not four years
     earlier, as would have been the case if the
     velocity difference had been the same as is now
     claimed (though, of course, the energies of the
     supernova neutrinos are much lower).

Theoretical physicist Steven Weinberg of the University
of Texas at Austin, winner of the 1979 Nobel Prize in
Physics

     The report of this experiment is pretty impressive,
     but it bothers me that there is plenty of evidence
     that all sorts of other particles never travel
     faster than light, while observations of neutrinos
     are exceptionally difficult. It is as if someone
     said that there are fairies in the bottom of their
     garden, but they can only be seen on dark, foggy
     nights.

Theoretical physicist Lawrence Krauss of Arizona State
University

     It is an embarrassment as far as I am concerned. It
     was not unreasonable for the experimentalists to
     submit a paper with an unexplained result. But a
     press conference on a result, which is extremely
     unlikely to be correct, before the paper has been
     refereed, is very unfortunate-for CERN and for
     science. Once it is shown to be wrong, everyone
     loses credibility. Neutrino experiments are hard,
     and systematic errors at the limit of resolution
     can be significant. Moreover, because the
     experiment appears to violate Lorentz invariance,
     which is at the heart of so much known physics, one
     should be skeptical. One should be additionally
     skeptical because observations of SN 1987A showed,
     as I wrote in 1998, that neutrinos and photons
     travel at the same speed to one part in a billion,
     several orders of magnitude below the claimed
     effect. Now, the only way out of that is to have
     some energy-dependent effect, but all the ones that
     make sense don't wash here.


Physicist and MINOS (Main Injector Neutrino Oscillation
Search) experiment co-spokesperson Jenny Thomas of
University College London

     There must be a more mundane explanation for the
     results. Let's hope we can find it.

Neutrino physicist Karsten Heeger of the University of
Wisconsin-Madison

     I think it is fair to say that many of us are
     stunned. This is an extraordinary result and we
     cannot even perceive all the implications if this
     result were true. All of modern physics as we know
     and teach is based on Einstein's special and
     general theories of relativity. If this effect were
     shown to be true, I would consider this the physics
     revolution of the century.

     As an experimentalist, we are all very cautious of
     such extraordinary results. I watched the Webcast
     from CERN ... and was impressed by the detailed and
     careful work presented by the OPERA collaboration
     in their talk. However, even for a neutrino expert
     it is difficult to follow and understand all the
     technical details that enter this measurement.
     There could be systematic effects that have not
     been accounted for. Independent experimental tests
     are needed.

Theoretical physicist Alexander Kusenko of the
University of California, Los Angeles

     While this experimental group is very good and
     competent, neutrino experiments are notoriously
     difficult to perform. This experiment is
     particularly ambitious. One has to wait for a
     confirmation.

     Neutrinos are fast, but science news travel faster!

Theoretical physicist Heinrich P„s of the Technical
University Dortmund in Germany

     It seems that the experimentalists were very
     careful, but this is really BIG news....

     There are certain misunderstandings with people who
     are very cynical now: Even if true, this result
     neither proves Einstein wrong nor implies that
     causality has to be violated and time travel is
     possible. Things can move faster than the speed of
     light without violating Einstein if either the
     speed of light is not the limiting velocity as one
     can observe it for light propagation in media such
     as, for example, water. This can be modeled with
     background fields in the vacuum as has been
     proposed by [Indiana University physicist] Alan
     Kostelecky.

     Or spacetime could be warped in a way so that
     neutrinos can take a shortcut without really being
     faster than the speed of light. As our three space
     plus one time dimensions look pretty flat, this
     would require an extra dimension (as proposed by
     [University of Hawaii at Manoa physicist] Sandip
     Pakvasa, [Vanderbilt University physicist] Tom
     Weiler and myself).

     On the other hand, if something moves faster than
     the speed of light, causality violations-aka time
     travel-may be a possibility (for example, in models
     with two warped extra dimensions as proposed by
     [Vanderbilt physicist] James Dent, Pakvasa, Weiler
     and myself). And that, of course, would have really
     crazy and mind-boggling consequences, but even
     there can [there] be scenarios which are
     contradictory.

     So, in short, this is really exciting. But since it
     is so exciting, I'm not sure whether one should be
     too optimistic that it will survive the tests of
     other experiments.

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