Scientists announced this week that they have created the most advanced clock in the world.
The clock, described this week in the journal Nature, is so precise that it would neither lose nor gain one second in about 5 billion years of continuous operation. That's pretty good, considering that the Earth itself is only around 4.5 billion years old.
There are more than a thousand species of sharks and rays in the world, and nearly a quarter of them are threatened with extinction, according to a new study. That means these ancient types of fish are among the most endangered animals in the world.
An aurora as seen over the Poker Flat Research Range north of Fairbanks, Alaska.
Skies across Colorado will offer a rare opportunity for seeing the Northern Lights — typically seen in places like Canada and Alaska. The impetus for this natural phenomenon comes from a powerful geomagnetic storm caused by an eruption from the sun.
For the scientists who have emotionally traveled with NASA's Voyager mission for decades, 2013 will be remembered as the year they knew Voyager 1 had finally become the first explorer from Earth to enter the mysterious realm of interstellar space.
Voyager 1 and its twin, Voyager 2, both blasted off in 1977, more than 35 years ago. Voyager 1 flew by Jupiter, then Saturn — and then on toward the unknown region that lies between stars.