Hollywood has always loved invading aliens - but now we're invading them, in a spate of recent flicks ranging from Avatar to Friday's just-opened Prometheus.
Astronomers have discovered more than 700 worlds orbiting nearby stars in the last two decades, and the moviegoing public is just getting the message about the new planets, say astronomers such as Seth Shostak of the SETI Institute. So, in a way, pop culture is reflecting science, including efforts such as NASA's Kepler space telescope, which is looking to find more planets in their stars' "habitable zone," warm enough for liquid oceans like Earth's that may be able to support life forms.
"I think the public has grasped the fact that planets out there are as common as cheap motels," Shostak says, noting that our Milky Way galaxy alone might contains 300 billion stars, including ones with multiple planets. "If only 1 in 1,000 is in the habitable zone, that is still about a billion habitable planets in our galaxy," he says.
Planetary scientist Kevin Hand of NASA's Jet Propulsion Laboratory in Pasadena, Calif., was a science adviser to Prometheus, and also offered advice to Avatar's team. He says top filmmakers, such as James Cameron and Ridley Scott, are paying increasing attention to the plausibility of the alien worlds they create. Movie makers have long imagined alien worlds, for example the double-sunned Tatooine of Star Wars fame, but the latest ones, "really listen to where science is headed today," Hand says.
Through the U.S. National Academy of Sciences' "Science & Entertainment Exchange" program, which unites movie-makers with scientists, Hand was involved in technical discussions with the Prometheus team. "We needed a world to explore that would be habitable, but with a somewhat toxic atmosphere, which was an interesting exercise," Hand says.
The result was a world called LV-223, which has an ocean, but with air too poisoned to easily breathe. That's easy to imagine, because some stars with planets have trace metals indicating their chemistry might differ from ours, along with signs of water in the dust disks around the stars that might be a source for water on the planets. LV-223 is the moon of a giant planet, one resembling the easier-to-detect ones most often discovered by astronomers so far. The movie's background materials call it a "cold and implacable environment (which) is more like hell than heaven."
Without spoiling the movie for those who haven't seen it, one idea central to the movie was the notion of aliens "seeding" life on Earth. "We talked about that a lot," including the idea of "conducting experiments with microbes on other worlds and what happens when experiments go 'wrong,' " Hand says. For similar reasons, NASA and Russia's space agencies have carefully sterilized past missions to Mars, fearing just this kind of contamination.
Although the filmmakers based their concept for the spaceship, called the Prometheus, on NASA and European Space Agency designs, space travel sending humans in hibernation across light years to visit an alien world seems unlikely by 2089, the time-frame for the film, Shostak says. Instead of the four years envisioned in the film, travel times to nearby stars for people would still span centuries because of the speed limit set by light, which tops out at 5.9 trillion miles in a year. That's something the movie evades with invented human hibernation couches. The Defense Advanced Research Projects Agency's "100 Year Starship Initiative," however, is investigating technologies needed for interstellar travel.
Alien biology remains a little shaky in films, Hand cautions. "Any species that has to reproduce by traveling 50 light years to invade the chest cavity of another alien species looks a little dicey from an evolutionary-survival standpoint," he says.
On the other hand, "I was inspired to go into science by some really bad science-fiction films from the 1950s," Shostak says. "It can't hurt to have some real science in the movies."