Search NOVA Teachers

Back to Teachers Home

NOVA scienceNOW: Dark Matter

Program Overview

This segment describes how scientists are trying to detect dark matter, a mysterious form of matter that exerts a gravitational force and seems to hold different bodies in the universe together.

This NOVA scienceNOW segment:

  • explains why physicists think dark matter exists—stars within galaxies and galaxies within galaxy clusters move faster than expected and, rather than flying apart, they stay in orbit together. However, there is not enough visible matter present to account for the gravitational pull required to hold these units together. Hence, if the laws of gravity are right, there must be an elusive substance (i.e., dark matter) responsible for the necessary gravitational force.

  • describes dark matter by what it is not, rather than what it is—it's invisible; doesn't glow; isn't composed of atoms; and doesn't create electric or magnetic fields.

  • suggests that dark matter may be made of a yet-to-be-identified particle, and that where there is ordinary matter, there is dark matter.

  • theorizes that after the Big Bang, dark matter acted like glue, pulling stars together to form galaxies, and that, without dark matter, galaxies would probably not have formed.

  • reports that dark matter maps reveal that galaxies are enveloped by giant clouds of dark matter.

  • describes a super-sensitive detector designed to "catch" dark matter particles. It is made of germanium, a superconducting crystal, that is kept at 50 thousandths of a degree above absolute zero (460 degrees below zero Fahrenheit).

  • explains that if dark matter strikes a super-cooled germanium crystal, the collision produces a minute amount of heat, which can be detected.

  • notes that because the detector is so sensitive, many things can set it off. Therefore it is located in an abandoned mine one-half mile underground.

Taping Rights: Can be used up to one year after the program is taped off the air.

Teacher's Guide
NOVA scienceNOW: Dark Matter