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centuries in a coach seat. And keep in mind that this is the nearest other star. To reach any stellar system with life might require a trip ten times longer or more. Could we beat this rap One possibility would be simply to accept that going to other suns is like Bolero—slow and soporific—and we’ll have to put the crew into suspended animation until shortly before arrival. The evident problem with this idea is that we don’t know how to successfully suspend the animation of anyone, despite what you see in the movies. A second possibility is to somehow construct a spacecraft that could cruise near the speed of light. This would greatly reduce the perceived travel time for the crew, thanks to special relativity. However, this approach runs afoul of some simple physics. Consider revving up a rocket—no bigger than the Saturn V that took men to the Moon—to 90 percent the speed of light. The energy required is greater than the United States has consumed since its birth in 1776. That’s a lot of fuel. In addition, barreling through space at such a velocity would turn grains of interstellar dust into deadly missiles. These otherwise innocuous bits of carbon would knife the length of the spacecraft in less than a millionth of a second, slicing and dicing the passengers en route. It seems that rocketing to the stars might be less than gratifying. But surely there’s warp drive in our future After all, conventional rockets are so twentieth century. Well, it’s true that several inventive schemes have been proposed to bend space in such a way that our craft could take a shortcut from one part of the cosmos to the other, reaching distant destinations in no time flat. These distortions of space and time are commonly called wormholes. But while wormholes described on blackboards often look promising, it’s unclear they will ever work in real life. The bottom line is simple: interstellar rocketry, while an established trope of science fiction, may be as much a pipe dream as fat-free doughnuts or 34 world peace. So what does this mean Will our ken ever extend beyond our cosmic front porch Is it hopeless to think that we might someday commune with other inhabitants of the galaxy, assuming such beings exist Some scientists think there’s hope aplenty. It takes the form of a straightforward experiment called SETI, the Search for Extraterrestrial Intelligence. The idea is to aim large radio antennas at nearby star systems, and pick up broadcasts from other worlds. Detecting a signal beamed from space would be compelling evidence that somebody’s out there, and allow us to learn about extraterrestrial sentients without fretting about either highspeed rockets or wormholes. SETI is well known to many, being the subject of the popular movie Contact (based on the 1983 Carl Sagan novel of the same name). In the film, Jodie Foster—commanding an array of large antennas—dons a pair of headphones, tunes her receiver, and soon picks up an alien radio signal. Unfortunately, real-life SETI has failed to duplicate Foster’s success, despite 50 years of listening. Indeed, given the length of time SETI researchers have been probing the skies, some people question whether this effort is worth the candle. After all, in a lifetime of surveillance, this project has yet to uncover a single peep from the cosmos. Could it be that there simply aren’t any aliens The universe, which astronomers know is desperately sparse, bitterly cold, and implacably hostile, might also be sterile—or at least bereft of the sort of selfaware biology that would amuse us in conversation. If we concluding that Homo sapiens is creation’s brightest bulb, this too would be ungratifying, unwarranted, and a bit self-serving. Despite the length of SETI’s search, its breadth has been shallow. This is a simple consequence of the lack of resources. A substantial NASA effort to make a systematic search, an enterprise that cost American taxpayers less than a nickel a year, was killed by Congress in the early 1990s, just as the NASA equipment was warming up. Since then, SETI has been a Lakes of natural gas pool on Saturn’s moon Titan. Could there be slow-moving, organic life in these bodies of liquid Image courtesy Cassini Radar Mapper/JPL/ESA/NASA.
part-time activity mostly carried out on someone else’s antennas—a small-scale project by a handful of people, funded by private donations. The upshot is that the number of star systems carefully examined for radio signals is less than a thousand—a trifling tally in comparison to the total stellar complement of our galaxy. Indeed, SETI’s reconnaissance to date is analogous to an imaginary expedition to Africa in search of elephants. Suppose you examined one city block’s worth of real estate, and found it pachyderm-free. Would you conclude that the continent is devoid of elephants Given the limitations of the experiment, it’s hardly surprising that evidence for extraterrestrial life has eluded our grasp. But how many star systems do we have to examine in order to find a signal A conservative estimate is one million. The trouble is, at the rate SETI has searched in the past, surveying a million star systems will take another 50,000 years. That’s not much inducement to sign on to SETI’s ship of discovery. Fortunately, there’s a truism for this experiment that’s important and largely unknown: the search is becoming faster. Indeed, it’s becoming exponentially faster, increasing in speed by 50 percent every year. This is a consequence of the rapid development of digital electronics. With more processing power, SETI experiments can examine star systems in batches, rather than one at a time. They can also more quickly check out a wide range of radio frequencies. Consequently, lack of success shouldn’t be confounded with lack of progress, and it’s possible the scientists will find a signal in the next two dozen years, assuming that the monies can be found to execute the search. In other words, in this generation we might be able to accomplish what keeps Captain Kirk busy in the twenty-third century: finding cosmic company among the stars. And we could do it without confronting the daunting difficulties of interstellar travel. So what Let’s say it happens. Let’s imagine that researchers succeed in pulling a signal from the dark voids of space. What happens next A common view is that the discovery would be kept under wraps, most likely by bureaucrats fearful of civil unrest. A SETI detection would be hushed up. While appealing to those who like to imagine that governments indulge in conspiracies, this is nonetheless a remarkable contention, given the widespread belief that at least some of the thousands of unidentified lights seen each year in the night sky—so-called UFOs—are extraterrestrial craft. According to recent polls, approximately one-third of the populace is convinced that alien beings are visiting Earth, not to mention occasionally interfering in our personal lives. But if this supposed invasion hasn’t inspired the citizenry to grab their pitchforks and lanterns, then why do we expect that the announcement of a radio signal, coming from hundreds of trillions of kilometers away, would provoke panic A cover-up is neither plausible nor necessary. In addition, there’s no inclination for secrecy among the SETI researchers themselves, so the detection of any extraterrestrial broadcast would soon be widely known. It’s far more likely that discovery of other thoughtful inhabitants of the galaxy would be received not with panic but with interest. We would want to know more: the nature of their biology, their planet, and their culture. Unfortunately, the technical limitations of most SETI experiments preclude picking up any message attached to their signals. We would only know that they were “on the air.” But that discovery would surely be an incentive to build far larger instruments to capture the message, followed by a massive attempt to decode and understand it. Imagine, then, downloading a torrent of information from a society that is literally and figuratively alien. The eventual fallout might be profound, with sequelae now only dimly foreseen. After all, Spanish royalty could hardly have imagined what the longterm impact of Columbus’ voyages would be. But one consequence is easy to predict and certain to be true: we would have proof that the long chain of biological development that began on this planet nearly 4 billion years ago was neither a miracle nor a fluke. And, as remarkable as we are, we’re not unique. Among the many discoveries by our species, that might be the greatest of all. b i o g r a p h y Seth Shostak, senior astronomer at the SETI Institute in Mountain View, CA, is the author of the recently released Confessions of An Alien Hunter: A Scientist’s Search for Extraterrestrial Intelligence, published by National Geographic Books. the explorers journal
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