Sky and Telescope - January 2016 - 20

Cosmic Relief
David Grinspoon

No Need to Feel Lonely
Recent results do not support the conclusion that we are alone in the universe.
new evidence suggesting that we are, after all, quite possibly alone in the
universe - or so you may have heard. Don't believe it.
The biggest discovery of our time is that planets are at
least as common as stars. Strangely, some have interpreted this as implying that intelligent, technological,
communicating life has not evolved
elsewhere. One who has expressed this
view recently is William Borucki, the
just-retired principal investigator for
NASA's remarkable Kepler spacecraft
and thus the person most responsible
for our recent bounty of knowledge about
extrasolar planets. While in Hong Kong
last September to receive the 2015 Shaw
Prize in astronomy, Borucki told reporters that, given our new knowledge of
so many worlds, we can conclude that
intelligence has not evolved elsewhere.
"Why haven't we been contacted?" he asked. His conclusion: "The evidence says, no one's out there."
Borucki is a brilliant and wonderful man, and we are
forever in his debt for the success of Kepler. But there
is little basis for jumping to this conclusion. In fact, for
decades, SETI had already operated under the considered
assumption that planets around stars were common. At
the ﬁrst SETI conference in Green Bank, West Virginia
in 1961, the attendees reached agreement on an estimate
for the number of planets in the galaxy that was very close
to the numbers scientists are now deriving from observations. While beautifully reducing the uncertainty, Kepler
has also essentially validated the intuitive hunches about
planets that the early SETI investigators held.
In the six decades since the ﬁrst radio searches, we've
learned that our galaxy is not bristling with civilizations
broadcasting the kind of radio messages predicted by
some physicists in the 1950s, and that our solar system
is not so teeming with obvious interstellar probes that
we would stumble upon one on our ﬁrst ﬂeeting forays
to other planets. That is all we know. It's a far cry indeed
from that to "we are alone."
Another recent headline touts a study showing that
alien "supercivilizations" don't exist. The evidence?

Januar y 2016 sky & telescope

When we scan distant galaxies we don't see any that
are radiating the kind of waste heat that would be seen
if a civilization had overrun the galaxy, maximizing its
population and consuming the energy of every star.
Seriously? What kind of supercivilization would
behave in that manner? Only those conforming to some
very primitive notions of what constitutes a civilization. The premise is
that successful lifeforms will keep on
multiplying indeﬁnitely, and that successful civilizations will seek out and
use more and more energy. But we are
already learning here on Earth that true,
sustainable intelligence may require
thoughtful deviation from the drive to
mindlessly propagate and utilize whatever resources we can get our hands on.
It seems doubtful that any "advanced"
civilization would act like that.
Finally, I keep hearing about the "great ﬁlter." Supposedly, some universal process exists that stops civilizations from continuing. According to this idea, "the great
silence" means that our own days are numbered. When
you carefully examine this argument, you ﬁnd again
that it rests on the false notion that we already have good
evidence for the absence of other civilizations or on the
argument that, if there were civilizations, they would
make their presence so apparent that we couldn't possibly miss them. The detailed justiﬁcations always make
wild, unsupported assumptions about the properties and
behaviors of aliens.
These are all fun ideas to entertain, but people tend
to get attached to certainty and start to believe they
know the answer. The only clearly mistaken opinions on
this beguiling question are those that are overconﬁdent.
We have to be comfortable with the uncertainty of not
knowing, resist easy answers, and keep exploring the
universe with open minds and all the tools and techniques we can muster. ✦
ISTOCK.COM / SOLARSEVEN

Scientists have found

David Grinspoon is an astrobiologist, author, and Senior
Scientist at the Planetary Science Institute. Follow him on
Twitter at @DrFunkySpoon.

http://www.ISTOCK.COM

Sky and Telescope - January 2016

Table of Contents for the Digital Edition of Sky and Telescope - January 2016