Searching for Trouble?
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thesis Searching for trouble? The search for signs of intelligent life of — here on Earth — carries a strong elsewhere in the Universe has been We have almost theme of violent conflict, perpetual battle underway since the pioneering efforts for resources and the oppression of weaker of Frank Drake in the 1960s. Most zero idea of whether groups by stronger ones. Yet, as Gertz points prominently, the privately funded SETI out, many METI enthusiasts follow a naive Institute has scrutinized radio signals for aliens are likely to faith that any advanced alien civilization will three decades and found nothing, despite be dangerous. also be morally advanced and will aim to widespread belief that the Universe must interact with us peacefully. be teeming with other civilizations. Fermi’s In fact, one idea favoured by METI-ists paradox — the conspicuous lack of any recent paper published on the arXiv is a version of the so-called zoo hypothesis signs of other intelligences, despite belief (https://arxiv.org/abs/1605.05663), put forward as one possible solution of the that they must exist — lives on. John Gertz of the Foundation for Fermi paradox. This idea holds that we’ve Of course, the SETI search has only Investing in Research on SETI Science and never seen aliens, despite their presence looked at about one in 50 million stars in the Technology has tried to raise awareness throughout the Universe, because the Milky Way, and may have simply looked at of the issue — and to make the case for aliens have decided to leave us alone. As the wrong ones, or at signals in the wrong continuing with the more conservative a result of their moral advancement, alien frequencies. The programme has also passive approach. civilizations view lesser-developed parts limited itself to a passive search, scanning You might think that active signalling of the Universe — those with still young the sky with increasingly sensitive devices isn’t really risky because the radio waves we civilizations — as wilderness areas or and processing the resulting volumes of use for communications have already been nature preserves to be protected and left data. Active efforts to make contact with leaving Earth and travelling out into space undisturbed, at least until the intelligences extraterrestrials by signal transmission since the 1930s. As of now, as Gertz points within them reach out with signals showing have been far less common. Drake himself out, such signals have swept over the nearest their desire to make contact. Having made sent out a weak message in 1974, and later 7,000 stars. However, this leakage is quite this assumption, METI-ists then assert that (reportedly) regretted the act. A few other weak; a telescope of Arecibo’s sensitivity on it’s time for us to do so. amateurs have sent out signals, but as yet a planet in any of those 7,000 star systems Gertz is right that this is nothing humanity has not undertaken any serious would not be able to detect it, although more than a grand and very dangerous programme of transmitting strong signals a more sensitive one, of course, might. If assumption with absolutely no backing. towards specific targets in the hope that aliens’ telescopes are like ours, then the And this is among the reasons that many someone, or something, might detect them chance of our leakage being detected could scientists have strongly criticized the METI and infer our presence. well dwindle over time as ever more of our proposals, which have, so far, been roundly Such an approach does seem inherently communications take place through cables, rejected. It seems far wiser to wait, and risky, given our complete lack of information or over directed satellite links, rather than continue the developing passive search about the kinds of civilizations that through simple atmospheric transmission. programme already established by the SETI may be out there, and the attitude they Hence, we may be at the end of a Institute, which is due to accelerate in the may take towards us. Yet not everyone window of time during which our normal near future. Just last year, businessman shares this view, and there’s been a recent communications technology has emitted Yuri Milner donated US$100 million over movement to initiate a technologically a significant detectable signal. Not so ten years to help boost the project. One day advanced effort to send out signals using, if we begin broadcasting a signal from it may even get public funding. for example, the 305 metre radio telescope Arecibo, as proposed by METI supporters We have no understanding of how close at Arecibo, Puerto Rico. The scientists Douglas Vakoch and Seth Shostak. Such passive SETI search may be to discovery. behind the movement — they call it a signal would be some 100,000 times It could come with the next advance in METI, for Messaging to Extra-Terrestrial stronger than the leakage signal of previous sensitivity, as happened with the search for Intelligence — argue that this is the logical decades. It’s true, as some METI advocates gravitational waves. Meanwhile, technology next step now that a passive search has failed argue, that Arecibo in its operation as an is driving rapid progress in computing to find anything for so long. asteroid-tracking radar has already sent resources, in the knowledge of the locations The idea is controversial, and rightly out such signals. Yet these tracking signals of exoplanets that are likely to be suited so. With access to the right transmitting wander over the sky, making them very to life and in astronomical technique devices, even one person could unilaterally much unlike a beam that would be focused in general. take a momentous step affecting the over significant periods of time on a single Patience must be among the qualities any future of all humanity, without any star system. mature and advanced civilization should broad global discussion or agreement. It’s hard not to see this as gratuitously possess. We would do well to exercise At worst, the consequences could be risky, especially as it would be undertaken such patience, while ensuring that the catastrophic, as any civilization detecting for no other reason than to satisfy our least patient among us cannot access the our presence is likely to be technologically deep intellectual curiosity. We have almost technology that would let them take matters very advanced, and may not be disposed zero idea of whether aliens are likely to into their own hands. ❐ to treat us nicely. At the very least, the be dangerous, although the single history idea seems morally questionable. In a of evolving biological life that we know MARK BUCHANAN 720 NATURE PHYSICS | VOL 12 | AUGUST 2016 | www.nature.com/naturephysics ©2016 Mac millan Publishers Li mited, part of Spri nger Nature. All ri ghts reserved. .