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Ghost Particle, The

Program Overview  Print this Teacher's Guide (PDF, 6 pages)

NOVA explores the 70-year struggle so far to understand the most elusive of all the elementary particles, the neutrino.

The program:

• relates how the neutrino first came to be theorized by physicist Wolfgang Pauli in 1930.

• notes the challenge of studying a particle with no electric charge.

• describes the first experiment that confirmed the existence of the neutrino in 1956.

• recounts how scientists came to believe that neutrinos—which are produced during radioactive decay—would also be involved in nuclear fusion, a process suspected as the fuel source for the sun.

• tells how theoretician John Bahcall and chemist Ray Davis began studying neutrinos to better understand how stars shine—Bahcall created the first mathematical model predicting the sun's solar neutrino production and Davis designed an experiment to measure solar neutrinos.

• details how Davis discovered only one-third of the neutrinos predicted and how those results prompted scientists to wonder over the years whether something was wrong with Davis' experiment, whether Bahcall's calculations were incorrect, or whether the sun was operating differently than first believed.

• notes how scientists later began to rethink their ideas about what a neutrino is and to wonder whether the different types of neutrino—electron, muon, and tau—could be the key to the problem.

• explains that while neutrinos can change from one type to another, the Standard Model predicted a massless neutrino that traveled at the speed of light and, therefore, could not experience time and would be unable to change.

• reports on a Japanese detector experiment that indicated that neutrinos do experience time, and therefore have mass and can change.

• describes how the first detector designed to detect all three types of neutrinos confirmed Bahcall's predicted number of neutrinos and verified that neutrinos do change as they travel from the sun to Earth.

• relates how future experiments are investigating the neutrino's properties and exploring whether the neutrino may have played a role in the creation of matter.

Taping Rights: Can be used up to one year after the program is taped off the air.