The first thing to know about potential alien invaders is that they are no longer classified by the U.S. Government as unidentified flying objects. That sounds too scary. They are classified as ...

Earth is dotted with humongous, human-made structures that, to an alien eye, may be tell-tale signs of intelligent goings-on.

Solar winds and coronal mass ejections may scatter narrow signals, making them harder for Earth-based telescopes to detect. The SETI Institute uses radio telescopes to search for signs of intelligent ...

Europe is quietly positioning itself to attempt one of the most audacious missions in planetary exploration: a dedicated landing on Enceladus to look directly for signs of alien biology. Instead of ...