A natural satellite is simply a celestial object that orbits a planet or a smaller body. Unlike the ones we build and send up ...

When Earth is opposite Mars from the sun, it will appear full because you’re looking directly on the daylit side. But ...

We all need some space sometimes—but it's harder to find than you might think. How far into our universe do we have to go to ...

Just as passengers don’t feel the plane’s speed while smoothly cruising, we don’t feel Earth’s movement because we’re ...

Another, even rarer view is to see our planet from the surface of another world—something, in fact, that first occurred only in 2004, when NASA’s Spirit rover on Mars snapped an image of Earth in that ...