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In a much lower energy range, a limit of |''v'' − ''c''|/''c'' < 2{{E|-9}} was set by the observation of 10-MeV anti-neutrinos detected in connection with the [[SN 1987A]] supernova.<ref name="OPERA_20110922"/> Had neutrinos emitted by SN 1987A been travelling with a speed corresponding to the speed reported by the OPERA experiment, the particles would have arrived at Earth almost four years before light from the event, while light from the supernova was in fact detected at roughly the same time as the neutrinos, consistent with the neutrinos travelling at the same speed as light.<ref>{{cite web|url=http://blogs.discovermagazine.com/badastronomy/2011/09/22/faster-than-light-travel-discovered-slow-down-folks/ |title=Faster-than-light travel discovered? Slow down, folks | Bad Astronomy | Discover Magazine |publisher=Blogs.discovermagazine.com |accessdate=25 September 2011}}</ref> The measurement from SN 1987A cannot immediately be seen as contradicting the measurement from the OPERA experiment, as it is not currently known how neutrino velocity may depend on particle energy, distance traveled, or other factors.<ref>{{cite web|url=http://news.discovery.com/space/reality-check-what-are-those-naughty-neutrinos-really-up-to-110924.html |title=Naughty 'Faster Than Light' Neutrinos a Reality? |publisher=Discovery News|accessdate=25 September 2011}}</ref><ref name=sciam_luminarydoubt />
Physicists affiliated with the experiment have been generally skeptical of their own result, stating in their paper: {{quote|Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly. We deliberately do not attempt any theoretical or phenomenological interpretation of the results.}} OtherNotable physicists unaffiliated with the experiment, such as [[George Smoot]],<ref>http://news.xinhuanet.com/english2010/sci/2011-09/27/c_131161271.htm</ref> [[Steven Weinberg]],<ref name="sciam_luminarydoubt"/> [[Martin Rees]],<ref name="sciam_luminarydoubt">http://www.scientificamerican.com/article.cfm?id=ftl-neutrinos</ref> [[Lawrence Krauss]],<ref name="sciam_luminarydoubt"/> [[Brian Greene]], and [[Michio Kaku]]<ref name=Challenge>{{cite web|title=Challenging Einstein is usually a losing venture|url=http://news.yahoo.com/challenging-einstein-usually-losing-venture-214054440.html|publisher=AP/Yahoo News|accessdate=26 September 2011|author=Jordans, Frank; Borenstein, Seth|date=24 September 2011}}</ref> arehave alsobeen skeptical of the result's accuracy, with some, such as [[Sheldon Lee Glashow|Sheldon Glashow]], offering refutations of the result in peer reviewed sources. <ref> A. G. Cohen and S. L. Glashow, ''New Constraints on Neutrino Velocities'', [http://arxiv.org/abs/1109.6562 preprint]</ref><ref>http://arxiv.org/abs/1109.6160</ref><ref name="arxiv opera link" /> Others have been more receptive, and some papers have been published discussing the result's possible validity, and the implications thereof.<ref name="arxiv opera link">{{cite web|title=Papers discussing OPERA's result at arxiv.org|url=<ref>http://arxiv.org/find/all/1/all:+Opera/0/1/0/all/0/1</ref>|accessdate=2 October 2011}}</ref> Physicists affiliated with OPERA have remained skeptical, however, stating in their paper: {{quote|Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly. We deliberately do not attempt any theoretical or phenomenological interpretation of the results.{{citation needed}}}}
SpokespeopleFollowing OPERA and CERN's request for confirmation, spokespeople for both Fermilab and the [[T2K experiment]] have confirmed their intentions to test the OPERA result in coming months.<ref name="LA Times" /> Fermilab noted in reaction to the OPERA announcement that the detectors for the MINOS project are being upgraded, and new results are not expected until at least 2012.<ref name=fermilab> ▼According to a paper by Andrew G. Cohen and [[Sheldon Glashow]], superluminal neutrinos of 17 GeV produced at CERN at the claimed speed should have arrived at LNGS with a terminal energy approaching 12.5 GeV.<ref> A. G. Cohen and S. L. Glashow, ''New Constraints on Neutrino Velocities'', [http://arxiv.org/abs/1109.6562 preprint]</ref> The energy loss is due to the process <math>\nu_{\mu}\rightarrow \nu_{\mu} + e^{+} + e^{-}</math>, an analogue of [[Cherenkov radiation]] which is kinematicaly{{clarify|date=October 2011}} allowed for superluminal neutrinos in vacuum.
According to a paper by Carlo Contaldi, the OPERA experiment neglected to take into account a convention for clock synchronization in non-inertial frames (as the Earth is rotating), which produced an inaccurate result.<ref>http://arxiv.org/abs/1109.6160</ref> But the opera experiment does not depend on synchronized clocks; they derive accuracy in the nanoseconds by using the [http://tf.nist.gov/general/pdf/192.pdf common-view GPS] approach, which compares time at the two locations from GPS signals from satellites visible at both places. To quote:
{{quote|Thus, in 2008, two identical systems, composed of a GPS receiver for time-transfer applications Septentrio PolaRx2e [16] operating in “common-view” mode [17] and a Cs atomic clock Symmetricom Cs4000 [18], were installed at CERN and LNGS (see Figs. 3, 5 and 6).}}
▲Spokespeople for both Fermilab and the [[T2K experiment]] confirmed their intentions to test the OPERA result in coming months.<ref name="LA Times" /> Fermilab noted in reaction to the OPERA announcement that the detectors for the MINOS project are being upgraded, and new results are not expected until at least 2012.<ref name=fermilab>
{{cite web
|title=OPERA experiment reports anomaly in flight time of neutrinos
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