Home
People
CDMS at Syracuse
DEAP/CLEAN at Syracuse
Facilities
About Dark Matter
Main CDMS Page
Main DEAP/CLEAN Page
Internal Pages
Seventy years ago, astronomers noticed a discrepancy between what the laws of gravitation predict and the actual behavior of celestial matter. The discrepancy lies in the data points: not only do stars rotate around their galaxy's center more quickly than they ought to, but their velocities also do not fall off after the radius of the galaxy, but remain relatively constant. This is known as the galaxy rotation problem. There is simply not enough known matter to provide enough gravitational pull to hold galaxies together!
This missing matter also reveals itself in an effect called gravitational lensing. Massive objects, like a galaxy, between distant galaxies and earth gravitationally bend the light making the galaxies appear "lensed" when observed from earth. Studies have shown that the amount of known matter is not enough to account for these observations.
In the subjects of astrophysics and cosmology, dark matter is a hypothetical form of matter of unknown composition that does not emit and reflect enough electromagnetic radiation to be observed directly, but whose presence can be inferred from gravitational effects on visible matter.
According to present observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter accounts for the vast majority of mass in the observable universe. The observed phenomena consistent with dark matter observations include the rotational speeds of galaxies, orbital velocities of galaxies in clusters, gravitational lensing of background objects by galaxy clusters such as the Bullet cluster (consists of two colliding clusters of galaxies), and the temperature distribution of hot gas in galaxies and clusters of galaxies.
Dark matter also plays a central role in structure formation, galaxy evolution, and has measurable effects on the anisotropy of the cosmic microwave background. All these lines of evidence suggest that galaxies, clusters of galaxies, and the universe as a whole contains far more matter than that which interacts with electromagnetic radiation: the remainder is called the "dark matter component".
The CDMS experiment aims to detect one dark matter candidate, called a WIMP: Weakly Interacting Massive Particle. These theoretical particles are thought to have a mass between 50 and 1000 GeV. They and are present at all places in the universe, and as cold dark matter, travel at speeds about 100 times slower than the speed of light. Because they are dark matter, the particles respond to neither the electromagnetic nor the strong nuclear force; they are weakly interacting and only react with baryonic matter through gravity and direct nuclear collisions. This means that these interactions are few and far between: a WIMP may pass through half a mile of solid rock without incident. This is why CDMS II is able to take place deep underground: the rock shielding has little to no effect on the WIMPs the experiment is trying to detect.
