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Q & A: neutrino energy

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Most recent answer: 04/20/2020
Q:
After reading that neutrinos were hypothesised to solve the missing/varying energy in beta decay, I�m confused as to how the neutrinos were supposed to use up this energy, as they have no mass. Maybe it�s a silly question but from what I�ve learnt it�s only possible to have kinetic energy if you have mass.
- Keith (age 16)
Bristol
A:

It's not a silly question given what you've been taught, but what you've been taught isn't right.

Particles that have no rest mass nevertheless do have energy. The classical formula for kinetic energy, E=0.5mv2 is wrong, although it's an excellent approximation when |v|< c. 

We discuss some of these issues here:

https://van.physics.illinois.edu/qa/listing.php?id=16351&t=photons,-mass,-gravity,-light,-rest-mass,-invariant-mass,-energy,-momentum

As it turns out, neutrinos do have some rest mass, so they carry away energy due to both that rest mass itself (E=mc2) and due to their kinetic energy. Your question, however, still is important for understanding how people thought this worked back when they thought that neutrinos were massless.

Mike W.


(published on 04/20/2020)

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