On Mon, 12 Apr 2010 17:44:52 EDT, [email protected]
(Phillip Helbig---undress to reply) wrote:

In article <[email protected]>, [email protected] (Eric
Flesch) writes:

On Fri, 09 Apr 2010 10:53:41 EDT, [email protected] (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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On Sat, 05 Jul 2025 21:14:40 PDT, [email protected] (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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