Dark Matter

Dark matter illustrated as a darkly colored substance strung throughout a large, sample expanse in the universe, with heavier concentrations colored black and thinner concentration rendered in light gray. Normal, luminous matter appears clustered into glowing galaxies and galaxy clusters found along the filaments of the dark matter cosmic web. (Image Credit: AMNH/KIPAC/SLAClab/Stanford)

Dark matter is a theoretical type of matter thought to comprise about 80 percent of all matter in the universe. Unlike the "normal" matter that makes up stars, the Earth and everything recognizable in daily life, dark matter is completely invisible. The only way dark matter is known to interact with normal matter is through the force of gravity. One way astrophysicists originally inferred dark matter's existence decades ago was by measuring the rotation rates of galaxies, finding that the gravity generated by available visible matter is insufficient to keep galaxies from flying apart. Further evidence for dark matter comes from "gravitational lensing," wherein unseen dark matter in clusters of galaxies gravitationally warps the fabric of space, causing light from background objects to bend and magnify. Leading models of cosmology indicate dark matter has played a key role in building up the weblike structure of galaxies throughout the universe. Scientists have proposed several hypothetical particles that could compose dark matter and that might fit into the framework of particle physics, called the Standard Model. The hunt for signs of the dark matter particles is taking place in special detectors deep underground, particle accelerators, and radiation beaming from space.

The Hunt for Dark Matter in the Universe

Juan Collar
Jun 02, 2011

A dark matter detector about 700 meters below the ground in a Minnesota mine has recorded a seasonal modulation in staggeringly faint electrical pulses – the possible result of dark matter particles called WIMPs that envelope the Milky Way galaxy and collide with atoms in the detector’s germanium crystal. The head of the research team, KICP's Juan Collar, discusses the meaning of the results.

Risa Wechsler: Shedding Light on the Dark Side

Ruth Weschler
Apr 09, 2010

Risa Wechsler, a member of the Kavli Institute for Particle Physics and Cosmology (KIPAC) at Stanford University, has a career path that has led to three Kavli institutes and one program, giving her particularly extensive roots in the Kavli community.

Blowing in the Wind

Sep 29, 2008

The next time you walk outside on a calm summer night and look up at the constellation Cygnus, also known as the Northern Cross, consider what is coming at you. 

On the GLAST Track

Gamma Ray Large Area Space Telescope
Aug 01, 2007

There’s far more to the universe than meets the eye. Astronomers have long known this, and much of their big-budget work for the past several decades, from radio telescopes to orbiting observatories, has the goal of “seeing” the cosmos on wavelengths that are inaccessible to human sight.

Frontiers in Astrophysics

Jun 25, 2007

How did the universe begin? When—or for that matter will—it end? Answering questions about our very existence is often at the heart of astrophysics.


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