Question

For many years, scientists were puzzled that the Sun seemed to produce only about a third as many neutrinos as predicted. How was this puzzle resolved?

A) Neutrinos were found to change flavor en route from the Sun to the Earth.
B) The Sun's core was discovered to be cooler than previously thought.
C) Neutrinos were found to be absorbed by interstellar dust.
D) The Sun's fusion rate was found to be much lower than previously estimated.

Answer 1

The Sun neutrino puzzle was resolved through the realization of neutrino oscillations, with the Sudbury Neutrino Observatory confirming that two-thirds of solar neutrinos change flavor before reaching Earth, aligning the total observed neutrinos with solar models.

Step-by-step explanation:

The puzzle of why scientists observed only about a third as many neutrinos from the Sun as predicted was resolved by the discovery of neutrino oscillations. This phenomenon means that the electron neutrinos (νuε), produced in huge numbers by nuclear fusion in the Sun's core, can change into muon neutrinos (νμ) or tau neutrinos (ντ) during their journey to Earth. The initial experiments were only sensitive to electron neutrinos, thus missing the others that were formed by this transformation.

To clarify, the Sudbury Neutrino Observatory experiment was crucial in resolving this mystery. It revealed that the actual total number of neutrinos reaching Earth matched the solar models' predictions, but only about one-third of these detected neutrinos were electron neutrinos, as two-thirds had changed flavor by the time they reached the detectors.

This process, called neutrino oscillation, explains the apparent discrepancy and aligns with our understanding of solar fusion. Ongoing research further investigates the properties of neutrinos, which are elusive due to their incredibly weak interaction with matter and tiny mass.