|The BrainTime package that I chose was the Physics Adventure. We started with a tour of the Sudbury Neutrino Observatory. This is a major physics facility, a giant ball of water two kilometres underground in Creighton Mine. The lab is buried that deep in order to block out radiation, because they are looking for particles called neutrinos. Neutrinos are tiny particles, very common but very difficult to measure because they hardly ever interact with regular matter. It was originally believed that neutrinos don't have mass because neutrinos pass through everything: me, you, the planet, the other planets, everything. People find this fascinating and infuriating. Neutrino's don't give a fig for the human project, whereas other forms of radiation at least have the courtesy to interact with matter. Anyhow, when they bury the observatory underground the other forms of radiation are blocked out, reducing noise and making the neutrinos easier to observe.
Once in a blue moon a neutrino will actually collide with something else. As SNO physicist Doug Hallman explained, the chance of a neutrino colliding with some matter in your body is about once in a lifetime. At SNO, scientists observe a giant ball of water, waiting for the occasional neutrino to bump into a neutron. They use D20, heavy water, in the ball because the molecule is made with an extra neutron, thereby providing more matter for the neutrino to hit. The outside of the ball is covered with a huge network of radon tubes that are focussed inwards. Each of these tubes is capable of recording one photon, a very tiny flash of light, which is emitted when the neutrino collides with a neutron and knocks off an electron. The event is then translated through software and graphed into data, which the scientists can read. On the basis of this information they can tell all kinds of things about neutrinos.
Getting to the lab was an adventure. We went down the mineshaft in the elevator with the miners. The cage plummeted into the bowels of the earth until we reached the right level. Then the cable was mechanically braked, causing a distinctive bouncing effect.
After this we walked through the mine for about twenty minutes. We could hear the miners in the other part of the mine, and occasionally we would see a vehicle passing with rocks.
Eventually we arrived at the lab where we had to take off all our clothes and have a shower. We then put on hair nets, coveralls, and boots, and proceeded to an air shower. The idea was to eliminate as much dust as possible, since keeping out radiation was the number one priority in ensuring good data collection. For the same reason, the water in the ball is continually cleaned, and most of the space in the lab is devoted to an elaborate filtration system.