Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2015 December 6

A Force from Empty Space: The Casimir Effect
Image Credit & Copyright: Umar Mohideen (U. California at Riverside)

Explanation: This tiny ball provides evidence that the universe will expand forever. Measuring slightly over one tenth of a millimeter, the ball moves toward a smooth plate in response to energyfluctuations in the vacuum of empty space. The attraction is known as the Casimir Effect, named for its discoverer, who, 55 years ago, was trying to understand why fluids like mayonnaise move so slowly. Today, evidence indicates that most of the energy density in the universe is in an unknown form dubbed dark energy. The form and genesis of dark energy is almost completely unknown, but postulated as related to vacuum fluctuations similar to the Casimir Effect but generated somehow by space itself. This vast and mysterious dark energy appears to gravitationally repel all matter and hence will likely cause the universe to expand forever. Understanding vacuum energy is on the forefront of research not only to better understand our universe but also for stopping micro-mechanical machine parts from sticking together.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply. NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC & Michigan Tech. U.