In the 1950s, two physicists decided that they would find the elusive “neutrino” they’d heard so much about. They did find it — just not the way they first thought they would. And since they thought they would find it by exploding a nuclear bomb, that’s a good thing.
Clyde Cowan and Frederick Reines were the perfect team to find the neutrino. Reines was fascinated with neutrinos, and had even asked Enrico Fermi about his special pet theory on how they might be harvested. Cowan was mechanically gifted and could come up with brilliant experimental set-ups.
Except Reines’ pet theory on how to spot neutrinos was to get up close to a nuclear bomb, and Cowan was brash enough to think that was a good idea. They planned to make a detector out of a liquid which would light up when hit by particles — not neutrinos themselves but the positrons emitted when a neutrino hits a proton — and vacuum tubes which would increase the intensity of the flashes of light. They planned to stick that detector down a mine shaft. And they planned to blow up a 20-kiloton nuclear bomb on top of that mine shaft. They figured that the detector would feel the shock wave from the bomb, but they’d allow it to fall onto foam rubber and feathers, so it would probably be fine.
Believe it or not, the experiment was approved. It was only when a skeptical colleague asked them how they would separate the flashes caused by positrons from the flashes that were caused by other particles that they stopped for a bit and thought. They realized that, when a proton got hit by a neutrino, turned into a neutron, and emitted the positron, both the neutron and the positron would go on to interact with the world. What’s more, they would most likely interact with the world in a set amount of time. By looking for the timing of the flashes, not the flashes themselves, the two could find evidence of the neutrino. This experiment required nothing more than a nuclear reactor, so no one had to explode a nuclear bomb after all.
Oh, how the two laughed at their Nobel Prize acceptance speech!
Top Image: National Nuclear Security Administration
[Source: Neutrino Hunters.]