Albert Einstein's theory of relativity explains how space and time are linked.
Gravitational waves are ripples in space-time created by the interaction of massive objects in space, such as black holes and neutron stars.
The International Space Station is a $100 billion research outpost in low-Earth orbit. See the latest news, photos and videos from ISS missions here.
Rocket launches used to be the realm of national governments, but with the rise of private spaceflight companies more rockets are launching into space than ever before.
NASA's Jupiter-bound Juno probe will study the gas giant's atmosphere, magnetosphere and gravitational field. Juno will orbit Jupiter for about a year.
The aurora borealis, also known as the northern lights, is the rippling night-sky light display found at the northernmost reaches of the Earth.
Roughly 80 percent of the mass of the universe appears to be dark matter: a material that seems to interact with ordinary matter only through gravity, without emitting light or energy.
Learn more about SpaceX's Falcon Heavy rocket, the world's most powerful booster, which made its debut flight on Feb. 6, 2018.
"We Don't Planet" is a new series of short explainer videos covering the most interesting objects and topics in the universe. Watch each new video, and learn about its subject matter, here.