Most critics of the Search for Extraterrestrial Intelligence (SETI) suggest merely that it is a well-intentioned but foolish waste of money, chasing after radio signals sent by “little green men” while substantive research projects with tangible results go unfunded. However, some, like well-known Cambridge physicist Stephen Hawking, go further: not only is SETI expensive, if done right, but it’s also a bad idea because we really don’t know who (if anyone) is listening. Usually, it is assumed that the worst-case scenario for SETI is that the money and time invested simply goes to waste. Not so, says Hawking: how are we sure that the aliens are really people we’d want to meet?
Until this year, Hawking was best known for his work in cosmology (the origins of the universe) and black holes, and for his popular scientific book, A Brief History of Time. However, in 2010 he produced a television documentary, Into the Universe, which advanced a startling claim: “If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans.” The likelihood that intelligent life exists among the stars is overwhelming, Hawking believes. However, there is also a high likelihood that there are at least some life forms which are both far more sophisticated than ourselves, and also on the lookout for resource-rich worlds to exploit. Hawking uses the example of 15th-century Latin America, but James Cameron’s recent blockbuster, Avatar, might be just as pertinent (though in that case, the predatory interstellar scavengers were human beings, and the victims were aliens).
In Hawking’s version of this theory, the aliens in question have already depleted their own world’s resources, leading to the sort of resource-poor future which many on Earth already fear for our own species. To escape the deprivation, the alien civilization in question took to the stars as scavengers, hunting out other resource-rich planets to exploit. Such a species might actually be looking for messages from civilizations like ours, in the knowledge that only a resource-rich world would be likely to give rise to an intelligent, message-sending civilization.
Hawking is not the first person to raise such fears. Indeed, his sort of scenario is the most common one among serious SETI skeptics, aside from those fringe groups who apparently believe that aliens’ chief interest in Earth is conducting bizarre scientific experiments on humans and livestock. If it sounds incredibly unlikely that alien scavengers might one day descend on Earth to pillage our resources, such critics freely admit that it is. However, they counter, one has to balance these unlikely risks against the equally unlikely benefits of SETI successfully identifying an intelligent alien communications source.
In truth, Hawking’s fears actually have less to do with what we conventionally understand as SETI – listening for alien radio signals – than with what is known as “active” SETI, sending out signals in the hope that they will one day be received and properly interpreted by an alien civilization. Troublingly, we already send out a large number of strong signals simply by accident, like television carrier waves, which means that the aliens Hawking fears could easily learn of our existence with or without SETI. The only comfort, in that case, is that the signals will take decades, centuries, or even millennia to reach alien listeners – and, presumably, about as much time for them to trace the signal back to its source.
However, there are also reasons to believe that Hawking’s pessimism is misplaced. A highly advanced spacefaring civilization might well have enough planets within reach that it sees no reason to “hunt” for primitive species like ours in order to find more. Indeed, given the level of excitement about future mining of asteroids and the Moon, it may even be the case that the presence of intelligent species really isn’t a very good marker for interstellar resource hunters anyways. Nevertheless, when a scientist as prominent as Hawking raises concerns about a matter like SETI, they are certainly worth considering carefully.
