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Supernova 1987a, light, neutrinos, VSL claims

  1. Sep 13, 2006 #1
    I'd like to examine the experimental side for a moment, not the theoretical. Would the non-differential (after very long distances and time, and taking into account the different production mechanisms) in the arrival of light and neutrinos from supernova 1987a constitute strong experimental evidence of the de facto constancy of the speed of light, and that Dirac particle pairs offer no impediment whatsoever to the propagation of light?

    In other words, since light and neutrinos have different interactions (EM and weak force), it would be strange that light would be impeded/slowed down by any purported changes in free-space energy in exact lock-step with particles slowed by another force.

    Any comments?
     
  2. jcsd
  3. Sep 13, 2006 #2

    Garth

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    Agreed.

    Also the fact that the neutrinos arrived a little after the light confirms the measurement that neutrinos have a small mass and are not massless.

    Garth
     
  4. Sep 13, 2006 #3
    I'm glad to have a response, because I've Googled for discussion in science circles, and brought the matter up elsewhere, and no-one seems to have noticed the implications, or answered me. After almost 20 years, you'd think someone would say 'heeeyyyyyy...??!!'.
     
  5. Sep 13, 2006 #4

    SpaceTiger

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    Do you have a reference for this? I was under the impression the neutrinos came several hours before the light.
     
  6. Sep 13, 2006 #5

    Labguy

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    They (neutrinos) did arrive first. 18 hours before the first optical sighting, but that doesn't necessarily mean there was a full 18 hour difference. Who knows if the first SN light was spotted as it just arrived?

    Regardless, neutrinos arrived first.
    http://hyperphysics.phy-astr.gsu.edu/hbase/astro/sn87a.html
    Mass implications there too.
     
  7. Sep 13, 2006 #6

    The earliest spotted light was three hours after the neutrino detection. Photos weren't developed until the day after though, so no one noticed the light for 18 hours.
     
  8. Sep 13, 2006 #7

    selfAdjoint

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    Dearly Missed


    According to the SM models, the neutrinos came out (due to their low interaction with the dense supernova material) before the actual explosion from which the light emanated.
     
  9. Sep 13, 2006 #8

    SpaceTiger

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    In fact, one need not even trust the models, there was a confirmed lack of optical emission approximately two hours after the neutrino events:

    SN 1987A: A Progress Report

    Even before 1987A, neutrinos were expected to be the first sign of a supernova.
     
    Last edited: Sep 13, 2006
  10. Sep 13, 2006 #9

    Garth

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    Yes you are correct. I was allowing for the time taken for the shock of the core collapse to reach the surface and affect the brightness of the star.

    Garth
     
  11. Sep 13, 2006 #10

    SpaceTiger

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    And how were you doing that? I don't see how the time it took the shock to propagate through star could have been known to very high precision, nor is there any mention of it in the papers I've seen. Again, I would ask for a reference.
     
  12. Sep 14, 2006 #11

    Garth

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    Not conclusive, as you imply, core-collapse models are speculative but try:

    Limits on the muon and tau neutrino masses from SN1987A

    Neutrinos from SN 1987A - Implications for cooling of the nascent neutron star and the mass of the electron antineutrino
    Garth
     
  13. Sep 14, 2006 #12

    SpaceTiger

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    Neither of those articles is actually accessible to me, but all are upper limits and I suspect that these limits were obtained by looking at the time width of the neutrino pulse, not the delay of the neutrinos relative to the light. The former was the standard method of obtaining a limit on the neutrino mass from SN1987A.
     
  14. Sep 14, 2006 #13

    Garth

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    At the time, I remember, we felt 1987A did give a lower limit to neutrino mass, although not a firm one; it was believed from the timing of the neutrino events that there were grounds that the neutrino mass was non-zero and therefore it might be a possible candidate for DM. Consequently the upper limit was also important, to establish whether the cosmic neutrino density could be sufficient to explain all of DM; of course this proved not to be the case.

    For an example of a lower limit, try the best fit Monte Carlo simulation of the February 1988 paper: Neutrino mass, luminosity variation, and spectrum of SN 1987A, which you can download free.
    Subsequently, the Super-Kamiokande (neutrino oscillations) observations suggested the mass of the heaviest neutrino was much less than this estimation, probably about 0.05 electron volts.

    However, their estimate of the mass of the progenitor to SN 1987A was accurate and is now thought to be 18 MSolar.

    Garth
     
    Last edited: Sep 14, 2006
  15. Sep 14, 2006 #14

    SpaceTiger

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    Garth, this is a good example of a paper that uses the relative arrival times of the neutrino events to constrain neutrino mass. There is no use of the light from SN1987A, as best I can tell. Even further, their results are very hand-wavy and rest on questionable assumptions of the simultaneity of various "groupings" of neutrinos. Not surprisingly, they turned out to be wrong and I'm pretty sure this is not viewed as evidence for the neutrino having finite mass. Also, their estimate of the mass of the star is not being used to correlate the light and neutrino signals, it is just based on the energy distribution of neutrino events.
     
  16. Sep 14, 2006 #15

    Labguy

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    I can't tell, but are you saying that these sites only are not evidence for neutrino mass, or that there is no evidence for neutrino finite mass?
     
  17. Sep 14, 2006 #16

    SpaceTiger

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    I'm saying I don't think SN1987A was used as evidence for a finite neutrino mass. This stuff all predates the discovery of neutrino oscillations.
     
  18. Sep 14, 2006 #17

    Labguy

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    Ok, now that makes sense.
     
  19. Sep 15, 2006 #18
    There is a better use of 1987A for validating the speed of light, though this may have already arisen in another thread.
     
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