For decades, scientists have searched the skies for signs of extraterrestrial technology. A study from EPFL asks a sharp question: if alien signals have already reached Earth without us noticing, what should we realistically expect to detect today?

Thousands of alien species could invade the Arctic, warns a new study. Warmer temperatures and more tourists make it easier for non-native plants and animals to get a foothold in far northerly outposts, say scientists. Species that are not native to an area can displace ones that already live there.

In 2010, a famed ecologist, Robert May, asked a hypothetical question to the scientific community. If an alien spaceship landed on Earth, one of the first questions they would likely ask would be, how many distinct life forms? How many species live on your ...