E.T. really interested in getting in touch with home, he might be
better off writing, not phoning. So contends Christopher Rose,
professor of electrical and computing engineering at Rutgers, and
Gregory Wright, physicist and private consultant, co-authors of a new
analysis of interstellar communications that made national headlines as
a cover article in the Sept. 2 issue of “Nature.” In their paper, Rose
and Wright 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.
“Our initial contact with extraterrestrial civilizations,” Rose says,
“may be more likely to occur through physical artifacts – essentially
messages in a bottle – than via electromagnetic communications.”
Rose and Wright hit upon their theory while trying to answer a
practical question – how to cram the most information per second across
a wireless channel. This led them to consider distance and the energy
required to send a signal. “Think of a flashlight beam,” Rose says.
“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 distance, they disperse a lot.” Once waves
pass a point, they’ve passed it for good, so a messenger must send a
wave-borne message continually. Physical messages encoded in an object,
however, stay where they land.
Rose is in favor of listening for messages, but he thinks researchers
should look for them as well. Messages may already have landed; we
might literally be standing on them, Rose says. Messages might not
arrive as language, per se: They might include anything from text to
organic material embedded in an asteroid or crater. Rose concedes that
the idea may be hard to accept, but, he says, the difficulty arises
from our concern about time. If the sender doesn’t care about its
greeting reaching his intended target and getting a reply in its own
lifetime, the difficulty disappears.
– Ken Branson