Magazine article USA TODAY

Where Dark Energy Might Be Found

Magazine article USA TODAY

Where Dark Energy Might Be Found

Article excerpt

It is one of the biggest mysteries in cosmology: Why is the universe's expansion accelerating? Just two decades ago, scientists realized the universe was growing faster over time rather than at a constant rate. The force assumed to be behind that expansion is called dark energy The realization that dark energy is responsible for the universe's growth came from astronomical observations, but more information is needed to understand what dark energy is.

Spyridon Argyropoulos, a postdoctoral researcher in the Department of Physics and Astronomy at the University of Iowa, Ames, showed that scientists can search tor dark energy using particle detectors at Switzerland's Large Hadron Collider (LHC). Working with the ATLAS detector collaboration in collision experiments at LHC, Argyropoulos has established some boundaries, or constraints, for how physicists might find dark energy.

The idea of a constant energy permeating the universe has held sway since observations by Edwin Hubble in 1929 upended Albert Einstein's theory that the cosmos was static and unchanging, but those observations supposed the universe is expanding at a constant rate.

In 1998, however, astronomers observed distant supernovae--exploding stars in their death throes--and determined the supernovae were farther away than expected. That meant a force must be counteracting the gravitational pull exerted by planets, stars, and other bodies and forcing the universe outward. …

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