Dark matter and dark energy


Visible matter makes up just 4 percent of the contents of the universe; the remaining 96 percent is made of dark matter and dark energy. Scientists discovered both by observing their cosmic effects but have yet to directly detect either. Fermilab experiments seek to uncover the mysteries of the dark universe.

Scientists discovered dark matter by studying the behavior of neighboring galaxies and galaxy clusters. They could not explain the way the galaxies moved based solely on the amount of visible matter within them; something else needed to be adding to their mass and exerting a gravitational pull. They named that something dark matter.

Dark energy is similar to dark matter, in that it is a concept created to answer a question. The universe began expanding after the big bang. The force of gravity from all of the matter inside the universe by now should have begun to put the brakes on that expansion. However, scientists have discovered that the universe actually is expanding at an increasing rate. A force seems to successfully have overpowered gravity; scientists call it "dark energy."

In the early 1980s, Fermilab scientists were some of the first to bring together the worlds of astrophysics and particle physics, creating the home of the study of dark matter and dark energy, particle astrophysics. In 1983, Fermilab began putting together a team of physicists, postdocs and students for its first Theoretical Astrophysics Group. By the end of the decade, Fermilab got involved in testing astrophysics theories by joining projects such as the Sloan Digital Sky Survey, the Cryogenic Dark Matter Search experiment, and the Pierre Auger Observatory.

Fermilab scientists continue to explore this cosmic frontier through a number of experiments.

Dark Energy Survey


The Dark Energy Survey uses a camera mounted on the Blanco telescope in Chile to survey the southern sky to investigate the effects of dark energy.



The Cryogenic Dark Matter Search is a supercooled, underground experiment searching for dark matter particles.



The Chicagoland Observatory for Underground Particle Physics uses bubble chambers to search for dark matter particles.

Pierre Auger


Pierre Auger is a cosmic-ray observatory whose detectors cover 3,000 square kilometers of the pampas of western Argentina. The observatory studies the debris from fast-moving particles that strike Earth's atmosphere, some at higher energies than could ever be achieved using a manmade particle accelerator.



The Sloan Digital Sky Survey used a camera mounted on a telescope in New Mexico to survey more than a quarter of the sky. Data collected by SDSS has given astrophysicists insights into the nature of dark matter and dark energy.