The iconic film 'Alien' came out 40 years ago. A scientist explains why Hollywood depictions of extraterrestrials have changed since then.

· The horror flick "Alien" hit the screen 40 years ago, in the summer of 1979. The film is one of Hollywood's best known sci-fi blockbusters.
· In the decades since "Alien" came out, depictions of aliens in movies have changed dramatically.
· Instead of showing extraterrestrial life as humanoid, directors have instead...