Dark Energy

Four possible fates of the universe, depending upon its density. From left to right: An overdense universe collapses upon itself; a critical density universe stays largely the same after inflation; an underdense universe keeps expanding at a steady rate; and finally, at far right, is the universe we apparently live in, which is undergoing an accelerating expansion due to a mysterious force called dark energy. (Image Credit: NASA)

Dark energy is a baffling and pervasive force accelerating the expansion of the universe. Observations originally in 1929 of distant galaxies moving away from us revealed that the cosmos is expanding. Because of the gravitational attraction between matter, however, researchers expected to find that this expansion has slowed over the universe's history. Instead, surprising observations first made in 1998 demonstrated that the universe previously grew at a slower pace. Subsequent data has shown that dark energy should comprise about 68 percent of the universe, with dark matter accounting for another 27 percent and the normal matter visible to us only five percent. Some theories for dark energy suggest it is a property of space itself, a sort of "vacuum energy," wherein space is not truly empty, but is instead a fizzing sea of energy. As the universe expands, more space is created and thus additional dark energy, leading to the observed accelerating expansion. Other theories point to new forces of nature or suggest that the best current explanation for gravity, Albert Einstein's general theory of relativity, is fundamentally wrong. Astrophysicists are making detailed maps of the cosmos' changes over time to attempt to learn more about dark energy's properties.

A Roundtable Discussion with the Kavli Institute for the Physics and Mathematics of the Universe

Feb 03, 2012
Hitoshi Murayama

At the newest Kavli Institute, solving the biggest mysteries of the cosmos is a "multilingual" enterprise where the research in mathematics, physics and astronomy combine to create a more complete understanding of the universe. A roundtable discussion with the Kavli IPMU's director and deputy directors.

Risa Wechsler: Shedding Light on the Dark Side

Apr 09, 2010
Ruth Weschler

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.

Eyeing Dark Energy

Feb 29, 2008
South Pole Telescope

Frigid and bone-dry, with six straight months of night each year, the South Pole is a forbidding place to live or work. However, it’s one of the best spots on the planet for surveying the faint cosmic microwave background (CMB) radiation left over from the Big Bang. 

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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