[ExI] More on Neutrinos

Alfio Puglisi alfio.puglisi at gmail.com
Fri Sep 30 18:28:55 UTC 2011

On Fri, Sep 30, 2011 at 7:43 PM, Dan <dan_ust at yahoo.com> wrote:

> On Friday, September 30, 2011 12:31 PM john clark jonkc at bellsouth.netwrote:
> > "Good argument that neutrinos travels at speed of light is that while
> supernova
> > they are observed simultaneously with photons."
> >
> > With the exception of photons particles travel at various speeds
> depending on
> > conditions, I don't know of any reason why all neutrinos should move at
> the exact
> > same speed all the time, but hell I don't even know why neutrinos move at
> all, nor
> > at this point do I think anybody else does either. Physicists will just
> have to
> > continue their experiments and see what happens and wait for a
> theoretician to
> > have a bright idea. If the bright idea turns out that the experiment is
> just wrong I
> > confess I will be a little disappointed.
> >
> > " remain possibility that neutrinos can be accelerated to larger
> velocities, but
> > EM field quickly decelerates them to speed of EM field propagation
> (through
> > kind of Cherenkov radiation?)"
> >
> > Cherenkov radiation contains energy, so unless the conservation of energy
> is
> > the next thing to go the neutrino the radiates it will contain less
> energy, but if it
> > has less energy it should be moving faster not slower.
> A little context here for the ignorant: how well measured have these
> quantities been for supernovae in general? How many data points are there?
> Just want to see how likely this one might be an outlier or observational
> error -- or even just something mundane missing from the model of
> surpernovae events.

Just one event, the 1987A supernova in the Large Magellanic Cloud, about
170,000 light years away. A total of ~20 neutrinos were detected a few hours
before the event was seen in visible light, in neutrino detectors that were
built to observe the Sun. The detection was unexpected and, since it was a
rather large flux, the physicists involved took a while to convince
themselves that the data was correct, and learnt about the supernova only
some days later.
Copious (enormous, in fact) neutrino production was expected by supernova
simulations, and the delay between the neutrino burst and the observation of
the supernova was attributed to the travel time of the bow shock inside the
star's body, which indeed should take a few hours according to models of the
star interior. At the time, no one theorized that the neutrinos were
superluminal, and three hours over 170,000 years is a rather small error

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