A National Science Foundation artist's drawing shows the inner four planets orbiting Gliese 581, a red dwarf star just 20 light-years from Earth. The newly discovered planet, in the foreground, has a 37-day orbit and, like Earth, is distant enough from the star for liquid water to exist. Lynette Cook hide caption

itoggle caption Lynette Cook

A slice of Hurricane Karl was captured by NASA's CloudSat satellite. The clouds were just over 8 miles high. hide caption

itoggle caption

A male Florida panther walks down Jane's Scenic Drive in Fakahatchee Strand Preserve State Park. Before scientists bred the Florida panthers with cats from Texas, they lacked vitality and were near extinction. Science/AAAS hide caption

itoggle caption Science/AAAS

Albert Einstein's theory of relativity challenges how we perceive time in our everyday lives. Now, researchers have a device precise and accurate enough to measure its effects in the laboratory. Keystone/Hulton Archive/Getty Images hide caption

itoggle caption Keystone/Hulton Archive/Getty Images