The interstellar object appeared by the sun a year ago, and disappeared from view in January. At first scientists assumed it was a comet, then an asteroid, before acknowledging that it was unlike ...

For more than a century, popular culture has trained us to picture extraterrestrials as bug-eyed, bipedal “little green men” ...

Lush leaves, verdant fields, and dense forests. When we think of life on Earth, the color green is often the first to come to mind. Plants appear green because of a pigment called chlorophyll. For ...

To observers from outer space, Earth's vast oceans and verdant landmasses make it appear as a blue world punctuated by green ecosystems. It's the only habitable world we humans have ever known, so of ...