WASHINGTON — Using data from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP), scientists have identified an unexpected motion in distant galaxy clusters. The cause, they suggest, is the ...

Explore 25 universe mysteries scientists are still scratching their heads over, from dark matter to the Big Bang's secrets.

"Although there have been multiple efforts to understand the nature of dark energy, its composition, and its manifestation in the universe," one expert says, "we know embarrassingly little about it." ...

We have not been able to detect dark matter yet, even though there are many aspects of the universe that suggest the existence of invisible matter. In one new theory, it is possible that dark matter ...

Dark energy, a mysterious force that scientists believe is behind the accelerated expansion of the universe, is weakening — which could result in the universe over the course of billions of years ...

The universe is approaching the midpoint of its 33-billion-year lifespan, a Cornell physicist calculates with new data from dark-energy observatories. After expanding to its peak size about 11 billion ...