Dark Matter

Background A seriously misunderstood idea in astronomy is dark matter. It‘s called darkfor two reasons. The more obvious is that it does not directly interact with light andtherefore has no visible color. A less obvious, but more accurate reason, is simplybecause we don’t know what it is. We have a huge body of evidence that says somemass is out there, but exactly what that mass is…well, the answer is dark. Wecannot see or manipulate this mass. Instead, we only know it is there by the way itaffects other things. In this way dark matter is like gravity. We don‘t actually see itor manipulate it, but we are well aware of it when it affects us during a fall to theground. Two potential dark matter particles are WIMPs (weakly interacting massiveparticles) and axions. Both are theoretical and have never been observed. Neitherparticle interacts with regular matter very often. In fact, But when it does, thereshould be a measurable effect. And that’s where a little chemistry may help… The scenario In laboratories buried very deep underground, physicists and chemists havebuilt exquisitely sensitive instruments to try and detect the rare interactions of darkmatter with regular matter. One particular experiment is constructed of anextremely pure crystal of germanium, about the size of a hockey puck (but don’task me what that is exactly..I don‘t follow hockey). The crystal is cooled to about50 mK (roughly 50): colder than outer space). An extremely sensitive coating, onlya few atoms thick, made from tungsten and aluminum metal, measures thetemperature of the crystal. The goal is to detect when a dark matter particle interacts with thegermanium crystal. When the particle comes screaming in from outer space, it willproduce a change in the crystal. The magnitude of the interaction would tell uswhat type of particle (WIMP or axion) caused it. Using your chemical knowledge, explain and/or demonstrate- the thermodynamics involved in this experiment and measurement- how the interaction of dark matter with the crystal would cause atemperature change- why the system must be kept so cold and isolated