Gravity and Makeup of Dark Matter

by Jeanette Cain

More articles in Stars

What is out there? The planets, stars, gas clouds, and galaxies. But, is there more? Those make up only a small portion of the total matter in the universe. Invisible material, dark matter, is 30 times greater than what you can see. The gravity of dark matter tugs on the stars, galaxies and light rays crossing the universe. Scientists believe there are several types, possibly from small stars to subatomic particles. Neutrinos were a result of the Big Bang, according to theory. At first scientists did not think of neutrinos as having mass, but new experiments suggest a neutrino has a mass 1/100,000 that of an electron.

Theories suggest that 20% of the universe's mass is with large objects. Three percent shine as stars and 80% is made of neutrinos and WIMP's. WIMP's are a leftover from the Big Bang, according to theory, and stands for "weakly interacting massive particles of subatomic size." It is heavier than hydrogen, and under normal conditions will speed straight through normal matter. It is thought that if WIMP's make up the majority of dark matter, possibly thousands may be going through your body at this very moment. Physicists are currently trying to prove the existence of the reality or myth of WIMP's.

Machos are ordinary matter that have been squeezed together so tightly that they are small, invisible objects, much like brown dwarfs, or black holes. A brown dwarf is a star that has failed. Theory says that these objects are thought to be in the halos surrounding the galaxies and have been named MACHOS. MACHOS stands for "massive compact halo objects." Their presence was detected by astronomers spotting the effect of their gravity on the light from stars in the galaxy next door-the Large Magellanic Cloud.

MACHO bright? When A MACHO moves in the front of a distant star, its gravity will focus and brighten the light of the star. Once again, astronomers discovered stars in the Large Magellanic Cloud. This lensing works from Einstein's theory of general relativity, which states that gravity can bend light. When the light of far away galaxies pass through a cluster of galaxies on its way to Earth, the cluster's gravity may bend and focus it. When the far away galaxy lies precisely behind the center of the cluster, it becomes a distorted circle, or an Einstein ring. For the most part, the distant galaxy is off center, which results in only parts of the ring being seen, such as, circular arcs.

Is there more? Try speeding and rotating galaxies. A rotating galaxy is surrounded by halos of dark matter. This is detected from the rapid spinning of spiral galaxies. If the gravity of the dark matter were not present, the galaxy's outer parts would be flung out into space. The first possible proof of dark matter came from galaxy clusters. Fritz Zwicky, in 1930, found the galaxies inside moved so fast, that, theoretically, they should break up, but they didn't. This suggests that some unseen matter must be holding the galaxies back. In later years, it was discovered that clusters also had hot gas that was trapped by the strong gravity.

So far, dark matter has not been seen, but there had been suggestions for future research and experiments with different light rays. It is estimated that 90% of a cluster's mass lives inside the unseeable dark matter.

Further Study:
Beginning of Time, Space, and Matter: The Big Bang

About 13 billion years ago, a fireball of matter and anti-matter were created, bringing into existence time, space and the building blocks of the universe.

Alpher, Ralph Asher: 1921-

Physics professor at Union College, Eagle Scout, mathematician and provider of the model for the Big Bang theory.


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3. Editors. Secrets of the Universe. International Master Publishing: US. 1999