By LEE BOWMAN
Scripps Howard News Service
September 01, 2004
- For more than two decades, scientists have been tuning into the stars for radio signals that might herald the presence of intelligent life beyond our planet.
But if a civilization really wants to do more than just say "hi" to another world, writing is more energy-efficient and perhaps ultimately more reliable, an engineer and a physicist contend in a new paper published Thursday.
"If haste is unimportant, sending messages inscribed on some material can be strikingly more efficient than communicating by electromagnetic waves," said Christopher Rose, a professor of electrical and computer engineering at Rutgers University and lead author of the report in the journal Nature.
"Our initial contact with extraterrestrial civilizations may be more likely to occur through physical artifacts - essentially messages in a bottle - than via electromagnetic communication," Rose and Rutgers physicist Gregory Wright said.
They argue that inscribing information and physically sending it to a location in deep space is more energy-efficient than pulsing it out on radio waves that disperse as they travel.
"Think of a flashlight beam. Its intensity decreases as it gets farther from its source. The unavoidable fact is that waves, both light and radio, disperse over distance, and over great distances, they disperse a lot," Rose said.
The paper grew out of Rose's work studying how to get the most information per second across a wireless channel. This led him to consider the "energy budget" required for sending a signal, with this budget increasing with distance.
The researchers calculated that because radio waves become so diluted, a distant world would have to produce an antenna the size of Earth to broadcast more than a basic message, and send it over and over to increase the chances it would eventually be heard.
By contrast, a physical message would take more energy to launch and more time to reach a destination, but it would be more durable. Several deep-space probes, including the Pioneer and Voyager craft, included metal plaques or discs containing diagrams and encoded information about Earth and its people.
Rose speculates that the "messages" originating out there could be anything from a text message in a real language to organic material from an asteroid - and that they might well be dotting our planet or other parts of the solar system, awaiting discovery and the technology needed to understand them.
In an accompanying Nature commentary, Woodruff Sullivan III, an astronomer at the University of Washington, noted that it's not certain that a more advanced civilization would be concerned about the cost of energy needed to send messages. But, he said, it would seem to us that radio messages would be the most efficient way to send greetings, and so radio astronomers should keep listening.
However, he added, "perhaps some attention should be paid to the possibility of one day finding in our solar system an information-drenched artifact, sent by an extremely advanced civilization interested only in one-way communication."
Something along the lines of the monolith in Arthur C. Clarke' s "2001: A Space Odyssey" or a message in a bottle.
On the Net: www.nature.com