NASA's Voyager 1 spacecraft has met two criteria indicating it has left the solar system, the first manmade object to do so.

A daredevil will skydive to Earth from 23 miles up on Oct. 8, achieving supersonic speeds during his freefall. Experts explain the physics of this unprecedented act.

On the decks of the Curiosity rover, some of the most advanced equipment ever developed by humans is being held together by some of the oldest forms of human technology: intricate knots.

A trio of photons emitted seven billion years ago from a gamma ray burst threaten to scrap decades of research by theoretical physicists.

Armstrong always insisted his famous moon quote was a misquote.

Two weeks in, NASA's Curiosity rover has already caught several alleged UFOs and other anomalies on camera, according to the fringe sector of the Internet.

Scientists have long debated whether the universe is a fractal.

Physicists say the Big Bang was a phase change, like water freezing into ice, rather than an explosion. The theory could have big implications.

We know that iron oxide makes Mars appear red, but we don't know exactly how so much of the compound got there.

Astronomers have figured out how four previously unexplained "monster stars" could have formed.

NASA's Curiosity rover will look for complex organic molecules on Mars that would be telltale signs of ancient Martian life. What will happen if it finds some?

The Web has come alive with chatter about a UFO hovering over the opening ceremony of the Olympics. But it sure looks a lot like a blimp.

There has never been an openly gay or lesbian astronaut at NASA. Sally Ride's legacy could change that.

Astronauts say space has an extremely distinctive, and not unpleasant, smell.

Considering all the mysteries that remain, Pluto's newfound moon almost definitely won't be the last of its surprises.

A fifth moon has been spotted orbiting the dwarf planet Pluto. What will this

The famous "Wow! signal," a possible alien message, will soon receive a reply from humanity. You can contribute a message via Twitter tonight (June 29).

The famous "Wow! signal," a radio transmission that may or may not have been beamed toward Earth by aliens, will soon receive a reply from humanity.

Investigators have addressed many of the most famous UFO and alien claims in history. Did they uncover any evidence?

A new film depicts the range of human reactions in the run-up to an Earth-shattering asteroid collision. Is Hollywood's version of events realistic?

On board China's upcoming mission will be the country's first female astronaut. Who is the Chinese Sally Ride, and how was she chosen?

The hip-hop artist GZA has an album in the works about the magnificence of the cosmos.

An astronomer has proposed the existence of an unseen planet in the distant outskirts of the solar system. It would explain the peculiar motions of Kuiper belt objects.

There are a couple of theories floating around about why the moon looks larger near the horizon. Either way, be sure to check out the effect during the "supermoon" on Saturday.