> The neutrinos (almost) don't interact with matter. Perhaps their
> speed in any media is the same

Don't forget that a vacuum isn't empty. It's full of particles that may
or may not and do and do not exist. Light photons might be disturbed
and slowed by gravitons, Higgs bosons, 4th dimension voids, and
who-knows-what-else, things that do not trouble neutrinos
--=20
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