Fermi Paradox Part 1
Our Galaxy Should Be Teeming With Civilizations, But Where Are They?
Is there obvious proof that we could be alone in the Galaxy? Enrico Fermi
thought so -- and he was a pretty smart guy. Might he have been right?
It's been a hundred years since Fermi, an icon of physics, was born (and
nearly a half-century since he died). He's best remembered for building a
working atomic reactor in a squash court. But in 1950, Fermi made a seemingly
innocuous lunchtime remark that has caught and held the attention of every
SETI researcher since. (How many luncheon quips have you made with similar
The remark came while Fermi was discussing with his mealtime mates the
possibility that many sophisticated societies populate the Galaxy. They thought
it reasonable to assume that we have a lot of cosmic company. But somewhere
between one sentence and the next, Fermi's supple brain realized that if
this was true, it implied something profound. If there are really a lot of
alien societies, then some of them might have spread out.
Fermi realized that any civilization with a modest amount of rocket technology
and an immodest amount of imperial incentive could rapidly colonize the entire
Galaxy. Within ten million years, every star system could be brought under
the wing of empire. Ten million years may sound long, but in fact it's quite
short compared with the age of the Galaxy, which is roughly ten thousand
million years. Colonization of the Milky Way should be a quick exercise.
So what Fermi immediately realized was that the aliens have had more than
enough time to pepper the Galaxy with their presence. But looking around,
he didn't see any clear indication that they're out and about. This prompted
Fermi to ask what was (to him) an obvious question: "where is everybody?"
This sounds a bit silly at first. The fact that aliens don't seem to be
walking our planet apparently implies that there are no extraterrestrials
anywhere among the vast tracts of the Galaxy. Many researchers consider this
to be a radical conclusion to draw from such a simple observation. Surely
there is a straightforward explanation for what has become known as the Fermi
Paradox. There must be some way to account for our apparent loneliness in
a galaxy that we assume is filled with other clever beings.
A lot of folks have given this thought. The first thing they note is that
the Fermi Paradox is a remarkably strong argument. You can quibble about
the speed of alien spacecraft, and whether they can move at 1 percent of
the speed of light or 10 percent of the speed of light. It doesn't matter.
You can argue about how long it would take for a new star colony to spawn
colonies of its own. It still doesn't matter. Any halfway reasonable assumption
about how fast colonization could take place still ends up with time scales
that are profoundly shorter than the age of the Galaxy. It's like having
a heated discussion about whether Spanish ships of the 16th century could
heave along at two knots or twenty. Either way they could speedily colonize
Consequently, scientists in and out of the SETI community have conjured
up other arguments to deal with the conflict between the idea that aliens
should be everywhere and our failure (so far) to find them. In the 1980s,
dozens of papers were published to address the Fermi Paradox. They considered
technical and sociological arguments for why the aliens weren't hanging out
nearby. Some even insisted that there was no paradox at all: the reason we
don't see evidence of extraterrestrials is because there aren't any.