
How the Neutrino’s Tiny Mass Could Help Solve Big Mysteries - theafh
https://www.quantamagazine.org/how-the-neutrinos-tiny-mass-could-help-solve-big-mysteries-20191015/
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shifto
Not really related but I like how they are trying to detect neutrinos to
discover a supernova before it happens [1]. As the neutrinos leave the star
hours before they collapse (because the neutrinos can easily escape the star
due to it's low mass).

[1]
[https://en.wikipedia.org/wiki/SuperNova_Early_Warning_System](https://en.wikipedia.org/wiki/SuperNova_Early_Warning_System)

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particleguy
A small correction- it’s not the small mass of the neutrino that allows it to
escape quickly, but the fact that they are electrically neutral, and also do
not interact with the strong force and do not get caught by the nucleus of
atoms. Photons have no mass, but they arrive after the neutrinos because they
are slowed down by being constantly absorbed and remitted by the atoms of the
star through the electromagnetic force.

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atlasland
Do you think neutrinos could be used to produce electricity?

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AnimalMuppet
Because they are electrically neutral, and do not interact with
electromagnetic fields, it would be quite hard.

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Koshkin
Well, generally speaking, in the world of elementary particles there may be
other kinds of interactions (and decay paths) as well as the good old
mechanical energy - all waiting to be converted into the electromotive force.

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atlasland
Are there new types of interactions underway that may make neutrinos
interaction feasible?

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millstone
A hypothetical idea is to direct a neutrino beam at the core of a pulsating
star, which modulates its frequency and allows for efficient interstellar
communication.

[https://www.economist.com/science-and-
technology/2011/04/07/...](https://www.economist.com/science-and-
technology/2011/04/07/talking-to-the-neighbours)

[https://arxiv.org/pdf/0809.0339.pdf](https://arxiv.org/pdf/0809.0339.pdf) is
the paper

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Majromax
> While neutrino oscillation experiments have measured the differences between
> the mass states, experiments like KATRIN home in on a kind of average of the
> three. Combining the two types of measurements can reveal the value of each
> mass state, favoring certain theories of neutrino mass over others.

Since the universe's cruel trick seems to be that the Standard Model -- in all
its ugly glory -- refuses to be falisified, what is the least surprising
outcome for this experiment? Is there a set of neutrino masses that is
minimally-illuminating of physics beyond the standard model?

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Herrin
There are a few interesting things that we could get from looking at neutrino
masses.

The first has to do more with the nature of the mass than the mass itself. In
the standard model, electrons, muons, and taus get their mass from the Higgs
field. There's a way for neutrinos to get their mass in other ways, but it
requires them to be their own antiparticles. And this gives a satisfactory
answer as to why their masses are so tiny, and suggests some new particles
(although at electroweak unification scale, so not anything we're going to
achieve with a collider any time soon). There are a number of double-beta
decay experiments trying to measure the Majorana mass of neutrinos.

The other would be if the neutrino hierarchy is "inverted". The tau is heavier
than the muon is heavier than the electron. Right now, with neutrinos, we can
only measure the difference in masses. And so it's not clear if the neutrino
with the most election portion[1] is the lightest or if the neutrino with the
most tau portion is. The latter would be "inverted" from what we expect, and
trying to figure out why might be interesting, though I don't know that it
immediately implies new physics.

There're also other things related to masses that are interesting. Neutrino
oscillations are determined by the differences in mass. Looking at these, we
might be able to discover more generations of neutrino (beyond electron, mu,
and tau), which would be new physics.

[1] the mass eigenstates of the neutrino (that is, the things with well-
defined masses) are not weak force eigenstates, so they contain mixtures of
the electron, mu, and tau neutrinos

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graycat
Q. So, an atom decays and gives off some particles including a neutrino. So,
we look at the mass-energy arithmetic before and after the decay and see that
it all adds up but does need the tiny mass-energy of a neutrino.

That fact, that small difference, seems curious, maybe toward _new physics_?
That is, somehow maybe the mass-energy amounts are, once again in science,
whole number multiples of something small. If so, then we can look for how the
other particles are whole number multiples??

I have to expect that 99+% of physics students have already thought of this.

Is there anything curious about that tiny bit of mass, e.g., why it has to be
there at all?

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at_a_remove
It's a bit different than that. The decay of a neutron into a proton and an
electron conserved charge, mass-energy (to an expected degree), and momentum.
However, spin was not conserved. The neutrino was dreamed up as kind of a
placeholder for the spin. However, it turned out that it was a real thing!

The mass-energy arithmetic should not be the thing you look at for a couple of
reasons. First, it's quite difficult to measure with exactitude. Second, the
binding energy for particles and their constituents plays a part that is
easily within error bounds.

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graycat
Thanks.

> First, it's quite difficult to measure with exactitude.

I wondered about something like that -- the mechanism really is exact to tiny
accuracy, no fuzz, but it's super tough actually to measure that accurately,
or some such. If my startup works, I'll return to physics!!! I promise!!
Thanks.

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blackflame
The Neutrino has always fascinated me since I first learned about particles.
It's almost not of this realm with the way it interacts with matter compared
to everything else.

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atlasland
I'm curious if there's new physics underway that may make neutrino
interactions at a large scale feasible. Experiments that I know usually detect
one to five neutrinos a year and I'm wondering if we could ever come up with
method that can capture orders of magnitude more than that

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peteradio
Would need to make ultra dense materials which would require subatomic
engineering.

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blackflame
Would such a thing even be attainable on earth without the tremendous forces
that collapse atoms into neutrons? Does matter in a neutron density state
convert back to atomic density state in the absence of such forces?

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peteradio
I think it would be unstable in general but perhaps some shielding could be
created to help but even so it seems like strong forces would need to be used
to hold the ultradense target together.

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JamesCoyne
Dupe:
[https://news.ycombinator.com/item?id=21268086](https://news.ycombinator.com/item?id=21268086)

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dang
Merged thither. Thanks!

Edit: oops, this one was posted earlier and that was the dupe. Fixed now.

