Fwd = How to Sort Signs of Artifical Life from the Real Thing (Shostak)
- Forwarded by: fwestra@... (Frits Westra)
Original Date: Fri, 31 Jan 2003 10:44:09 -0500
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How to Sort Signs of Artifical Life
from the Real Thing
By Seth Shostak
Senior Astronomer, SETI Institute
posted: 07:00 am ET
30 January 2003
Picture Jodie Foster, her eyes closed and a mildly bored look on her
face. Shes wearing earphones and listening to the dull roar of the
Now imagine Jodie 20 seconds later, when she hears something sounding
like an unpleasant accident in the Boston Pops percussion section.
Jodie knows shes scored big: the aliens are on the air.
Still, how can she be sure shes picked up intelligence, and not just
the cosmic gurgle of a completely natural object? How can she know
shes not merely harkening to the ticking beat of a pulsar, the whoosh
of a quasar, or perhaps the lasing bray of a molecular gas cloud?
Because the signal sounds artificial, thats how.
But what does that mean? In a universe awash in electromagnetic
radiation filled with light and radio from a slew of objects that
either emit or transmit how do we recognize a signal thats produced by
intelligence? How do we define artificial?
This problem is well known in the context of SETA, the Search for
Extraterrestrial Artifacts. For example, any astronomer would be
impressed by finding a stellar grouping in which a hundred stars were
precisely arrayed on a 10 by 10 grid, and quickly conclude it was an
alien construction. But not all artifacts are so unambiguous. For
decades, the Viking Orbiter photo of the "Face on Mars" lathered up a
lot of folk who felt that the appearance of this feature as seen by
the Orbiters camera met the criteria of artificiality. Surprisingly,
despite recent high-resolution photos of the "Face" that strongly
challenge this conclusion, the debate continues. (Crop circles are a
different matter: here the arguments fly not over whether or not
theyre artificial, but who makes them.)
In the late 1940s, a Soviet engineer and science fiction writer, A.P.
Kazantsev, suggested that the famous Tunguska meteor of 1908 (which
leveled trees as far away as 25 miles, and roasted 200 reindeer) might
have been an exploded, nuclear-powered spacecraft from another world
making this the Siberian equivalent of a purported alien landing
mishap in Roswell, New Mexico four decades later. (Extraterrestrial
rocket jockeys apparently can manage interstellar travel. Its the
landings that befuddle them.) But the failure to find any tell-tale
indications of nuclear reactions at Tunguska, and a better
understanding of how rocks from space can explode in our atmosphere,
has quelled this idea.
Artificiality, some property that belies intelligence, is a crucial,
and somewhat unresolved, concept in SETI. In the mid-1960s, a radio
source found and cataloged by Caltech radio astronomers, CTA-102,
piqued the interest of researchers in the U.S.S.R. This source
apparently varied on time scales of 100 days and even less. Such
relatively rapid change was, the Soviets averred, the result of
deliberate signaling, and the famous physicist Nikolai Kardashev
encouraged further study of CTA-102 as it might be a highly advanced
society. As it turns out, CTA-102 is a quasar, not a beacon.
In 1967, British radio astronomers found some radio sources that
emitted exquisitely regular pulses, and tentatively labeled them LGMs:
Little Green Men. Their methodical signals certainly seemed to be
mechanical, rather than natural. Once again however, the transmitters
were found to be odd but not alien. The Cambridge astronomers had
Its worth asking what about a pulsars precise radio heartbeat would
tell you that theyre not artificial. To begin with, the emissions
occur over a wide bandwidth; a broadcast splatter rather similar to
the static caused by lightning, and clearly a very inefficient way to
transmit information. In addition, endless, regular pulses dont convey
any information. Just as an interminable flute tone would not be music
(except, perhaps, to Andy Warhol), so too is an unceasing clock tick
devoid of any message. Within a few years of their discovery, pulsars
were found all over the sky, a further indication that they were
natural members of the galactic bestiary, rather than some societys
attempt to get in touch. Finally, astrophysicists quickly confected a
plausible theory that pulsars are collapsed stars. This has not only
explained their radio (and optical) ticks, but also even predicted the
fact that they slow down.
Is the ambiguity of the Cambridge discovery a thing of the past? Do
contemporary SETI researchers have such a firm hold on what
constitutes an artificial signal that theyll immediately recognize it
when they find it? Or need we be concerned that, in the words of The
Who, "we dont get fooled again"? Jodie Foster heard a rhythmic sound
effect that was, to her, unambiguous. Soon thereafter, her SETI team
discovered an old TV broadcast layered into the received signal. This
firmly tagged it as not only extraterrestrial, but intended for us. No
uncertainty there. But the scenario depicted in Contact could only
play out in real life if aliens are very nearby.
A true SETI signal is likely to be quite different from its fictional
counterparts. In the next installment of this two-part saga, well
explore how todays SETI scientists hope to discern that most
intangible cosmic commodity: artificiality.
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