Are we screwing ourselves by transmitting radio signals into space?George Dvorsky5/07/13 5:02pmFiled to: aliensSETIextraterrestrial intelligenceexistential riskssciencespace14211EditPromoteShare to KinjaToggle Conversation toolsGo to permalinkFor nearly a hundred years, Earth has sent radio signals into space. If anyone nearby is listening, they probably know we’re here. In light of this, a new paper assesses the potential danger presented by such signals, concluding that the benefits outweigh the risks. But how can we really know? AdvertisementTop image: Scene from Battleship (2012), a film in which an alien civilization discovers Earth by detecting its radio emissions. Leaky Earth?We’ve been shouting out into the cosmos for quite some time now. Electromagnetic waves of various intensities and frequencies have been streaming away from Earth for well over a century, the remnants of TV broadcasts, mobile phone conversations, satellite transmissions, and military, civil and astronomical radars.AdvertisementWe’ve even deliberately tried to get ET’s attention — a controversial practice known as METI (Messaging to Extraterrestrial Intelligences). There have been many such attempts, including the 2001 Teen-Age Message to the Stars organized by the Russian cosmologist Alexander Zaitsev. His work, and those of others, have been criticized as being insanely risky given the dearth of information we have about the nature of ETIs. Two years ago, John Billingham and James Benford called for a global moratorium on METI, an initiative similar to the one David Brin and myself worked on last decade.But now, owing to all this human activity, the Earth has a radiosphere that’s inexorably billowing outwards at the speed of light — a clear signal that’s just waiting to be picked up.And indeed, according to the new paper’s authors, Jacob Haqq-Misra, Michael Busch, Sanjoy Som, and Seth Baum, this leakage could in fact be detected by an extraterrestrial intelligence (ETI) armed with the right listening equipment.SponsoredOur signals decrease in intensity as they leak out into the cosmos. But depending on the signal’s strength and frequency, these waves can propagate for cosmologically vast distances and still carry enough information to connote the presence of intelligent life.Arecibo Observatory. Credit: H. Schweiker/WIYN and NOAO/AURA/NSF.AdvertisementThe Arecibo Planetary Radar in Puerto Rico provides a good example. As the researchers note, at a transmitting power of 0.8 MW and a frequency of 2,380 MHz, the APR’s powerful signal could be picked up by a “watcher” with a 1 km2 receiving antenna at distances of up to 200,000 light years!Credit: Haqq-Misra et al.That's a rather extraordinary claim, so I spoke to SETI expert and scifi novelist David Brin about it — and he's not convinced detection is this easy. He told me that, even if an ETI had a one square kilometer array, they would have to point it a at Earth for the duration of an entire year. "Because it would take that long," he told io9. "But why stare if you don't already have a reason to suspect?"AdvertisementLike SETI Institute's Seth Shostak, Brin believes that Earth is not detectable beyond five light years. "With one exception: Narrow-focused, coherent (laser-like) planetary radars that are aimed to briefly scan the surfaces of asteroids and moons," he says, "And not to be confused with military radars that disperse."This new paper, says Brin, is very unconvincing about detectability of leakage.To transmit or not to transmit?Earth's leakiness aside, we also need to know if anyone out there is even listening.AdvertisementAdvertisementAs the authors note, some SETI experts contend that, if an ETI really wanted to know that we’re here, they could locate us without having to listen for our radio waves. For example, they could figure out that life is here by analyzing the spectrum of reflected ultraviolet, optical, and near-infrared sunlight from the Earth’s surface and atmosphere. Or, an ETI could learn of our technological civilization by detecting artificial nighttime lighting of large urban areas, or by detecting exaggerated amounts of carbon dioxide in the atmosphere.More conceptually, advanced civs could could pepper the galaxy with Bracewell communication probes — a point the authors fail to mention in the paper; they could already be in the neighbourhood waiting for a particular signal. ShareTweet Kinja is in read-only mode. We are working to restore service.