Quiz Question

One of a continuing series


Readers aren’t allowed to dive into text books and Internet sources. You have to come up with the answer from your own knowledge base. That doesn’t mean I have to rely solely on my knowledge base to draft these questions. I need to make sure I spell everything correctly.

This is about solar neutrinos. There are three kinds of neutrinos:

  • electron neutrinos
  • muon neutrinos
  • tau neutrinos

Electron neutrinos are produced in the core of the sun. This we know from our knowledge of the sun’s energy-production process. However, when we measured solar neutrinos starting about 50 years ago, the number was too small. Was our knowledge of the sun wrong? Was our understanding about neutrinos wrong? The question could be resolved if we knew whether neutrinos have mass.


What difference would it make whether neutrinos have mass? That’s the quiz question.

As an aside: This question came up at a creationist meeting nearly 25 years ago. It affected my decision to get a degree in physics.

Another aside: Vic Stenger, a physicist and noted skeptic who once came to give a talk for the North Texas Skeptics, was one of the scientists on the team that resolved the issue.

Post your answer in the comments section below. I will provide the answer by this weekend. It’s likely somebody already knows the answer and will post it by the end of today.


It has been suggested (by me) that additional explanation would be helpful. Here it is:

Physicists conjectured that electron neutrinos were converting to muon or tau neutrinos on the way to Earth. We were seeing fewer electron neutrinos because by the time they got to Earth they had converted. What does neutrinos having mass have to do with this?


And here it is. To answer this it would have been helpful to be acquainted with basic principles of physics. Here are a few:

  • Objects with non-zero rest mass are constrained to travel less than the speed of light.
  • Objects with zero rest mass must travel at the speed of light.

That leaves this: If neutrinos have zero mass (zero rest mess) then they will travel at the speed of light. When something travels at the speed of light, time stands still for that something. If neutrinos have zero rest mass, then they will travel at the speed of light, and they cannot transform, because time stands still for them.

What Vic Stenger and a large team working in Japan determined is that neutrinos have rest mass. Muon neutrinos produced by cosmic rays were changing to tau neutrinos. Additional observations made in Canada determined that electron neutrinos from the sun were changing to muon and tau neutrinos.

4 thoughts on “Quiz Question

  1. If neutrinos have a mass (component) then most of the ones generated by the sun would be “captured” by the sun itself; very few would escape the immense gravitational pull of the sun.

    If they didn’t have mass then we would see a lot more from the sun. We see only a percentage because they do have a mass. We only see the ones which did escape.

    As an aside, if photons had a mass the sun would be lot dimmer.

  2. I cannot quite recollect why. I would take a guess though.

    The half-life of electron neutrinos with mass may be in the order of seconds or a fraction of a second. That would account for the low counts in our earth orbit.

  3. Pingback: Quiz Question | Skeptical Analysis

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