SETI Needs to Read, Not Listen
What technology would an extra-terrestrial intelligence use to communicate with us? For fifty years, the search has presumed that an ET would use radio waves to announce “we’re here.” Not a good idea, says a professor of computer and electrical engineering at Rutgers. He thinks investors on distant planets would put their money not on radio commercials, but books.
It’s not often that a topic as speculative as SETI gets coverage in elite science journals, but the ideas of Christopher Rose made the cover of Nature this week.1 Basically, he and Gregory Wright feel it is much more energy efficient to inscribe messages instead of broadcasting them. This has led to a flurry of clever headlines in the news media: such as, “ET, don’t phone home; drop a line instead” on EurekAlert, and “ET Phone Home? Try Writing,” on MSNBC News. The BBC News, however, suggests that the new ideas may have been stimulated by the silence (see 08/13/2004 headline); “A recent radio search of 800 stars showed no sign of a signal from ET,” it says.
Woodruff T. Sullivan, summarizing the new view in the same issue of Nature2, explains the authors’ energy analysis of communication methods:
Unless the messages are short or the extraterrestrials are nearby, this ‘write’ strategy requires less energy per bit of transmitted information than the ‘radiate’ strategy does. Cone-shaped beams of radiation necessarily grow in size as they travel outwards, meaning that the great majority of the energy is wasted, even if some of it hits the intended target. A package, on the other hand, is not ‘diluted’ as it travels across space…, presuming that it’s correctly aimed at its desired destination. (Emphasis added in all quotes.)
Radiation only has an advantage for short messages; otherwise, inscriptions are superior, Rose and Wright argue. EurekAlert elaborates:
In addition, Rose says, when waves pass a particular point, they’ve passed it for good. Potential recipients at that point might be unable to snag a passing message for any one of many reasons. They might not be listening. They might be extinct. So someone sending such a message would have to send it over and over to increase the chance of its being received. The energy budget goes up accordingly. A physical message, however, stays where it lands.
Sullivan has some reservations about their presentation. How can we presume to think like ET? How do we know economics would be a deciding factor in their deliberations? Furthermore, “we do not know if such packages, even if efficiently sent, would ever in fact be recognized and opened.” But then again, the same criticisms apply to radio messages.
An implication of this new energy-per-bit study is that there might be messages from extraterrestrial intelligence right under our feet.
So how should these results influence today’s SETI strategy? Short “we are here” messages would still seem to be most efficiently sent by electromagnetic waves, and we should continue looking for the same. But perhaps some attention should be paid to the possibility of one day finding in our Solar System an information-drenched artefact, sent by an extremely advanced extraterrestrial civilization interested only in one-way communication. This intruder might be orbiting the Sun or a planet, or resting somewhere on a planet, moon or asteroid…. If astroarchaeologists were to find such an object, it would hardly be the first time that science fiction had become science fact.
The news media have pointed out, with illustrations, that we humans have sent inscribed messages ourselves: most notably, the Pioneer plaque and the Voyager record. EurekAlert suggests some of the forms an incoming message might take:
Rose speculates that “messages” might be anything from actual text in a real language to (more likely) organic material embedded in an asteroid – or in the crater made by such an asteroid upon striking Earth. Messages – and Rose suggests there might be many of them, perhaps millions – might literally be at our feet. They might be awaiting our discovery on the moon, or on one of Jupiter’s moons. They might be dramatic or mundane. A bottle floating in the ocean is just a bottle floating in the ocean – unless, upon closer inspection, it turns out to have a message in it.
Difficult as these ideas might be to accept, they stem from our concern about time, Rose explains. The sender(s), however, may not be time dependent. The choice of medium might be a function of how much the extraterrestrial intelligence had to say. He says, “Since messages require protection from cosmic radiation, and small messages might be difficult to find amid the clutter near a recipient, ‘inscribed matter’ is most effective for long, archival messages, as opposed to potentially short ‘we exist’ announcements.”
Incidentally, rumors of a possible alien signal announced in the media such as on New Scientist were quickly denounced as nothing unusual on BBC News
1Christopher Rose and Gregory Wright, “Inscribed matter as an energy-efficient means of communication with an extraterrestrial civilization,” Nature 431, 47 – 49 (02 September 2004); doi:10.1038/nature02884.
2Woodruff T. Sullivan III, “Astrobiology: Message in a bottle,” Nature 431, 27 – 28 (02 September 2004); doi:10.1038/431027a.
Hmmmm; information-drenched artifact. A possible real message in an actual language. A lot to say. Millions of copies at our grasp. Contents dramatic or mundane (or both). A medium not limited to a fortunate few living in a particular century or country. A sender outside of time, whose intelligence, identity, and intentions we cannot presume to fathom. Receivers who might not be listening. A package that might not be recognized or opened. Sounds a lot like Hebrews 1:1-3, II Timothy 3:15-17, II Peter 1:16-21, John 5:38-47, and John 1:10-12. Maybe a good place to search for an intelligent message is in the hotel room drawer.