Science Frontiers – Dark Matter
music
Piilonen: Weve been led to the belief that the universe is made up of ordinary matter in the form of electrons, protons, neutrons. Everything that we knew about the universe seemed to be made up of this stuff called matter.
Theres more to the universe than meets the eye. Im Jim Metzner and this is the Pulse of the Planet.
Piilonen: About a decade or so ago, cosmologists looking out into the far reaches of the universe discovered through their careful observations, that there was much more to the universe than this ordinary matter.
Leo Piilonen is chairman of the department of physics at Virginia Tech. When I asked him what else is out there besides ordinary matter, he pointed to the behavior of distant galaxies.
Piilonen: Present thought is that ordinary matter makes up less than 5 percent of the content of the known universe. There is five times as much of this mysterious stuff called dark matter, which is only seen by the interactions of galaxies -one galaxy interacting with another. And the way that the stars move around inside of galaxies indicates the presence of this invisible stuff. Thats why we say its dark; this invisible stuff we say is dark matter thats causing stars to rotate around inside a galaxy and causing galaxies to interact one with the other in a way that would not be if the galaxy only contained the ordinary matter that we can see that gives off light.
Apparently you dont have go searching in distant galaxies to find dark matter.
Piilonen: Theres a dark matter halo surrounding just about every galaxy, and that dark matter, then, pervades everywhere within the galaxy, including here in this room. However, we have a hard time detecting its presence directly because it doesnt interact with ordinary matter much, if at all.
Why should we care about dark matter? Well find out in future programs. Pulse of the Planet is made possible in part by the National Science Foundation; I’m Jim Metzner.