The Dark Side of The Universe

Until recently the nature of the universe seemed pretty clear cut. There were galaxies, which contained stars, planets, other types of objects such as black holes and comets, and a lot of gas and dust. Everything else was simply nothingness. The whole shebang was expanding due to "The Big Bang" which created all that stuff. Oh, there were mysteries, such as what is gravity, what happens to stuff that falls into a black hole and what caused the Big Bang to happen. But as careful measurements were made by astronomers, the numbers did not come out right. Astronomers first talk about the existence of dark matter in the 1930s. Observations showed that it outweighed ordinary matter by factor of six to one.

Galaxies are embedded in great halos of dark matter. But what was this stuff that had such a great gravitational affect but was undetectable otherwise? Astronomers think that it must consist of particles that hardly interact with ordinary matter at all. Because of this, its exact nature is unknown.With the advent of the science of particle physics, some clues have been found by particle physicists. While investigating what causes radioactive decay, a new force called the "weak nuclear force" was discovered. The hypothetical particles that carry this weak nuclear force should have properties that hint at dark matter. I want to quote a paragraph from the article in Scientific American written by Jonathon Feng and Mark Trodden. 

"These hypothetical particles include some collectively known as weakly interacting massive particles. The name arises because the particles interact only by means of the weak nuclear force. Being immune to electromagnetic and magnetic forces that dominate the everyday world, they are totally invisible and have scarcely any direct affect on normal particles. Therefore, the make the perfect candidate for cosmic dark matter." The article goes on to catalog the types of experiments that are being done to prove or disprove this theory. We shall see whether the real nature of dark matter is discovered in the next few years. It appears that physicists and astronomers are working at the problem from many different angles.