Dark matter is matter that cannot be detected by electromagnetic radiation, hence dark.

Dark matter are divided into three different types (HDM, WDM, CDM) :

* Hot dark matter - nonbaryonic particles that move ultrarelativistically
* Warm dark matter - nonbaryonic particles that move relativistically
* Cold dark matter - nonbaryonic particles that move non-relativistically

[ Reference - Wiki ]

There are many assumptions, and nobody really knows much about what is Dark Matter is.

Dark matter is matter that cannot be detected by electromagnetic radiation, hence dark. In physics and cosmology, dark matter is hypothetical matter that does not interact with the electromagnetic force

According to present observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter and dark energy account for the vast majority of the mass in the observable universe.

While examining the Coma galaxy cluster in 1933, Swiss astrophysicist Fritz Zwicky, of the California Institute of Technology was the first to use the virial theorem to infer the existence of unseen matter, what is now called dark matter.

Currently research by scientists attempting to discover exactly what this dark matter is with the world’s biggest atom smasher in Switzerland.

How much dark matter there is, and what effect it may have on the future of the Universe as a whole, scientists are hoping to make with the Large Hadron Collider (LHC) underground near Geneva.

There is a new warning about the health dangers of cell phone use. The director of the University of Pittsburgh Cancer Institute and UPMC Cancer Centers has issued the new advisory.

Other countries have recommended limits on exposure, and that in Canada, public health officials in Toronto have advised young people to limit cell phone use.

“Recently I have become aware of the growing body of literature linking long-term cell phone use to possible adverse health effects including cancer,” Dr. Ronald Herberman said in the memorandum.

The advisory suggests certain measures to limit exposure to electromagnetic radiation emitted by the devices, such as shortening the length of conversations or keeping the phones away from the head by text messaging or using headsets or speaker phone options. It also recommends that children not use cell phones except in emergencies.

A child’s developing organs “are the most likely to be sensitive to any possible effects of exposure,” according to the document.

[ Cancer chief sees cell phone risks ]