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  • Re: Accelerated expansion of the Universe - revisited

    From Eric Flesch@21:1/5 to Phillip Helbig---undress to reply on Sat Jul 5 21:14:40 2025
    On Mon, 12 Apr 2010 17:44:52 EDT, helbig@astro.multiCLOTHESvax.de
    (Phillip Helbig---undress to reply) wrote:
    In article <4bc01a7c.30721792@nntp.aioe.org>, eric@flesch.org (Eric
    Flesch) writes:
    On Fri, 09 Apr 2010 10:53:41 EDT, eric@flesch.org (Eric Flesch) wrote:
    this means only that the neutrino is below delta, for any delta.
    Ignore the weasel behind the curtain.

    [[Mod. note -- There is quite solid evidence... that at least 1
    neutrino species have nonzero mass. -- jt]]

    Thus my point about the weasel. Nonzero is operationally the same as
    zero if a minimum value can't be found. KATRIN will attempt to
    establish a minimum mass -- I predict it will fail.

    The chain of reasoning is that neutrino oscillations have been observed
    and these imply mass, even if a concrete value for that mass is not
    observed.

    OK, it's 15 years later, and the latest from KATRIN is https://www.kit.edu/kit/english/pi_2025_029_astroparticle-physics-neutrinos-weigh-less-than-0-45-electronvolts.php

    As I expected, KATRIN could not find a minimum neutrino mass.
    Instead, they are reduced to finding ever-smaller upper limits to the
    neutrino mass, that upper limit now being 0.45 eV.

    Physicists must decide whether a mass arbitrarily close to zero, i.e.,
    always measured as less than any tested-for quantity, is equal to
    zero, or if there is a grey "virtual" zone between mass and massless
    which has a physical meaning distinct from either. Or, as
    mathematicians might say, is there an excluded middle or not.

    Eric

    [[Mod. note -- The word "always" is doing some heavy lifting there.
    All we really know is the outcome of (publicly-known) measurement
    *to date*.

    By virtue of various solar neutrino experiments, together with
    nuclear-reactor and particle-beam experiments, we have some (partial)
    knowledge of the differences between the squares of the masses of the
    various neutrino flavors. Since the experimental bounds on these
    differences exclude zero, we know that at least some neutrino masses
    are nonzero, but we're not sure which ones. See https://en.wikipedia.org/wiki/Neutrino_oscillation#Observed_values_of_oscillation_parameters
    for a nice summary of what we know at the moment.
    -- jt]]

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  • From Eric Flesch@21:1/5 to Eric Flesch on Mon Jul 7 10:52:15 2025
    On Sat, 05 Jul 2025 21:14:40 PDT, eric@flesch.org (Eric Flesch) wrote: >Physicists must decide whether a mass arbitrarily close to zero, i.e.,
    always measured as less than any tested-for quantity, is equal to
    zero, or if there is a grey "virtual" zone between mass and massless
    which has a physical meaning distinct from either. Or, as
    mathematicians might say, is there an excluded middle or not.

    [[Mod. note -- ...
    By virtue of various solar neutrino experiments, together with >nuclear-reactor and particle-beam experiments, we have some (partial) >knowledge of the differences between the squares of the masses of the
    various neutrino flavors. Since the experimental bounds on these
    differences exclude zero, we know that at least some neutrino masses
    are nonzero, but we're not sure which ones. See >https://en.wikipedia.org/wiki/Neutrino_oscillation#Observed_values_of_oscillation_parameters
    for a nice summary of what we know at the moment.

    Thanks for the interesting article which I have pondered over. My
    worldview is that *momentum* is the fundamental unit, with mass/energy
    and vectors derived from that. Given that, I'd model that neutrinos
    travel with a constant momentum, usually at the speed of c, but that
    an oscillation is like a phase change, and where mass is involved then
    the speed is sub-c throughout the oscillation, resuming c afterwards.
    Momentum is conserved throughout. Sort of like light, but with
    self-checks along the way.

    I'm not conversant with leading-edge neutrino research, but I'm always
    on the lookout for the key simplifications that fit the data. Being
    wrong is a natural hazard. Thanks for the reply.

    [[Mod. note --
    This web page
    https://en.wikipedia.org/wiki/Neutrino_oscillation
    explains a bit more about neutrino oscillations, and how different
    measurements let us put constraints on the various parameters in the
    theory. Also, the MSW effect (a resonance while neutrinos are passing
    through the outer layers of the Sun) is important:
    https://en.wikipedia.org/wiki/Mikheyev%E2%80%93Smirnov%E2%80%93Wolfenstein_effect
    -- jt]]

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