Despite the
accusations of my correspondents, I try to keep an open mind about our search
for ET.
That's not
entirely trivial. Scientists, whose job description is to learn something
wonderfully new, are just as human as the next haberdashed hominid. After
pursuing an exploratory experiment for years or decades, they inevitably build
up both a psychological and monetary investment in their strategy. They can
easily become thoroughly marinated in their current approach, and dismiss other
ideas with a sneer and a wave.
I try not
to do that, and I credit my colleagues with the same.
It's a
constant battle, as SETI
scientists (and string theorists, for that matter) are often accused of falling
down the wrong rabbit hole. If only they'd adopt a completely different research
tack, it's said, they could look forward to stashing a Nobel medal in their
desk drawer.
"Why waste
time looking for old-style radio signals," many people have written me,
"when the aliens will be shooting neutrinos our way?" Neutrinos are one of many
types of suggestions for "weird SETI" that make sense, but perhaps not
overwhelming sense. These ghostly particles have the advantage of barreling
right through such petty obstacles as planets, which means you don't have to
worry much about where to aim your "telescope" the signal could even come
from behind you. The problem with these particles is that they cost a
tremendous amount of energy to produce, and our neutrino detection efficiency
is really low.
Quantum
entanglement has become an oft-heard phrase at the low-grade parties I frequent.
"The aliens will use entangled particles to signal us," many tell me.
At first
blush, this sounds like a nifty idea. QE could offer the gold standard for
interstellar chit-chat: inexpensive and instantaneous a kind of subspace
communication channel a la "Star Trek."
Well, you
can put that thought away for now. A subtle piece of logic known as Bell's theorem shows that, despite the spooky action at a distance of entangled particles,
they're not instruments for faster-than-light
shout-outs.
Another
perennially popular refrain with correspondents is to suggest looking for
gravity waves, probably because a lot of people make the unwarranted assumption
that gravity propagates faster than light. As far as we know, it doesn't, and (like
neutrinos) gravity waves are difficult to generate and painfully hard to
detect.
There's a raft
of clever schemes for sending information from one place to the next if you
don't demand a lot of bandwidth (which translates into the speed of information
conveyed). I've written before about how garrulous aliens might grab our
attention with a flash of laser light beamed our way. This might be a
once-a-month or even once-a-century signal, but that would be good enough. After
all, if a periodic, bright flash were to be seen on some random patch of sky, legions
of astronomers would relentlessly study that position and perhaps turn up a
low-power broadcast with gobs of useful information (such as the meaning of
life, or how to make a perfect souffle).
Luc Arnold,
a French astronomer, has suggested that aliens might
signal us with giant shadow puppets. Possibly inspired by NASA's Kepler
mission, which uses a space-based telescope to find small planets by the slight
dimming they induce when passing in front of their home stars, Arnold opined that
the aliens might produce a simple signal that Kepler or something like it could
easily find. A signal that's always "on the air."
The idea is
that the extraterrestrials would construct big, opaque polygonal structures,
and sling them into orbit around their sun. Anyone observing stars using a
technique similar to the Kepler telescope could notice one of these light
blockers. If the screens were some shape other than round, the time pattern of
the observed dimming would tip off distant astronomers that they hadn't found a
planet rather, they'd discovered a manufactured object.
None of
these types of "transmissions" is currently the subject of SETI scrutiny, and that
might sound as if we've got deaf ears to new ideas. Well, not to worry. These
schemes may be pursued by others. Neutrino and gravity wave detectors are
being deployed by physicists, and Kepler is collecting data as we speak. And
frankly, there's ample precedent for serendipity in exploration. Think of the
1967 discovery of pulsars. They were found by a radio astronomer who wasn't
looking for anything of the kind. Quasars were also found by accident (as was
Viagra).
So in some
sense, traditional SETI which after all, involves only a few dozen
professional researchers world-wide has backup; namely physicists, and just
about the entire field of astronomy. That's a good thing, because SETI funding
is still too cramped to permit its practitioners to test a whole lot of different
strategies.
As for me,
I try to constantly reassess our work by keeping an open mind about new approaches.
So far, none has swayed me from our schemes to hunt for light or radio signals.
But if a slicker idea comes along even if it's weird well, I'm willing to
give it an audition.
Seth Shostak is the author of Confessions of an Alien Hunter.
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