Over an illustrious 50-year history, Star Trek TV shows and movies have introduced audiences to some of the most famous fictional aliens. Be they Klingons, Cardassians, Vulcans, or tribbles, the Trek universe abounds with distinct and diverse extraterrestrials.

For now, such exotic civilizations remain in the realm of science fiction. But scientists have plenty of ideas about what real alien life might be like, and what our chances are of ever discovering whether we are alone in the universe.

In the past few decades, scientists have developed exquisitely sensitive equipment to search for other habitable worlds and to hunt for greetings from across the cosmos. To date, astronomers have found more than 3,500 planets beyond our solar system, and they calculate