Narrator: This is Science Today. The Solar Neutrino Problem, a physics puzzle that has stymied scientists for decades, has been solved. Physicist Kevin Lesko of the Lawrence Berkeley National Laboratory helped figure it out. He says the problem had to do with measuring these subatomic particles called neutrinos.

Lesko: When we've measured neutrinos on Earth for the previous forty years we've always detected fewer neutrinos coming from the sun than should be there based on our knowledge of how the sun works and this has been called the Solar Neutrino Problem.

Narrator: The difficulty was that neutrinos come in three types, and previous tests could only detect the electron-type neutrinos. The latest experiment found all the neutrinos and solved the problem.

Lesko: About one-third of the neutrinos coming from the sun are electron type, and two-thirds are muon and tau. And muon and tau type neutrinos would not have been made in the sun by the nuclear physics that goes on in the center so two-thirds of the neutrinos have transformed or have oscillated from electron type into muon or tau type in the process of coming to the earth.

Narrator: For Science Today, I'm Larissa Branin.