Space

It's a question scientists have been asking for more than 400 years.

Galileo Before The Papal Tribunal by Robert Henry. Hulton Archive, Getty Images

The letter may solve a centuries-long mystery.

Happy first day of fall! The season of colorful foliage, frosty mornings, and pumpkin-spice everything is upon us, thanks to the autumn or fall equinox.

Joe Barnard is the Elon Musk of model rockets.

In the 1980s and well into the 1990s, everything associated with Arnold Schwarzenegger was big. Big biceps (22 inches during his bodybuilding heyday).

NASA's Perserverance rover takes a photo of Mars.

Few celestial objects have fascinated humankind throughout history more than the Red Planet. Here's what you need to know about Mars.

The hapless dwarf planet got demoted in 2006, but some stubborn scientists are still lobbying for reinstatement.

ESA/Hubble, NASA, A. Simon (GSFC) and the OPAL Team, J. DePasquale (STScI), L. Lamy (Observatoire de Paris)

The phenomenon is not limited to our planet.

Plastic is surprisingly hard to preserve.

The spacecraft will use a robotic arm to scoop up a sample of Bennu and then return it to Earth.

Huge news for future Moon explorers.

Earth as captured from near the lunar horizon by the Lunar Reconnaissance Orbiter in 2015.

Let's review why and how we've known for at least 2300 years that the Earth is round.

Vice President Spiro Agnew and former President Lyndon Johnson view the liftoff of Apollo 11

Apollo 11 launched on July 16, 1969, on its way to the moon.

One technological breakthrough left the common pencil in the dust.

Not everyone agrees.

The baby planet is a few times bigger than Jupiter.

You won't notice it, though.

Their theories are based on the idea that a "universal grammar" might hold true for both aliens and humans.

From left: Wally Schirra, Deke Slayton, Gus Grissom, Christopher Craft of the Mercury Operations Division, Gordon Cooper, Scott Carpenter, John Glenn, and Alan Shepard.

Would you have been qualified to be an astronaut back in 1958?

At the heart of this nebula lies a star that's larger and brighter than our Sun.

The planet's putrid atmosphere is a clue to where it first formed.

You can even see equipment left by Apollo 17 astronauts.

Yes, they talked about sandwiches.

Have you ever seen a flash of bright light streaking through the night sky? People around the world have different ways of explaining these so-called shooting stars.

Why Is It So Dark in Outer Space?

Newly Uncovered Galileo Letter Details How He Tried to Avoid the Inquisition

Autumn Equinox: The Science Behind the First Day of Fall

This Amateur Rocketeer Builds Functioning, Miniature Replicas of SpaceX Rockets

Ad Astra: The Time Earth Almost Got a Space Billboard

11 Riveting Facts About Mars

Is Pluto a Planet After All? A New Argument Emerges

Here's What the Northern Lights Look Like on Saturn

Scientists Are Racing to Save Neil Armstrong's Deteriorating Spacesuit

5 Goals of the OSIRIS-REx Mission to the Asteroid 'Bennu'

NASA Found 'Definitive Evidence' That There's Water Ice on the Moon

The Science Behind Why the Earth Isn't Flat

Watch Apollo 11 Launch

Why Do Astronauts Use Space Pens Instead of Pencils?

New Study Says We Could Be Alone in the Universe

Here's the First Confirmed Image of a Planet Being Born

The Moon Is Making the Days on Earth Longer

Linguists Say We Might Be Able to Communicate With Aliens If We Ever Encounter Them

Were You Meant to Be an Astronaut? Try Passing NASA's Project Mercury Intelligence Test

NASA's Hubble Telescope Captures the Lagoon Nebula's Explosive Core

It's Official: Uranus Smells Like Farts

Take an Ultra-Detailed Tour of the Moon With This NASA Video

Every Conversation That Happened During the First Moon Landing, Visualized

Why Are There Shooting Stars?