IDIOT’S GUIDES: SCIENCE MYSTERIES EXPLAINED
If there really were aliens on other planets, wouldn’t
we have met them by now?
We’re discovering more and more Earth-sized planets, but we still haven’t found any evi-
dence of other intelligent life. Where are the aliens? Are we really alone in the galaxy?
While it’s puzzling that we haven’t seen any aliens in our stellar neighborhood, we’ve only surveyed a tiny
fraction of the galaxy. It’s just too early to tell ….
The case of the missing aliens has a name: the Fer-
mi Paradox. An Italian physicist named Enrico Fer-
mi came up with it in 1950. He said, since the galaxy
is so big and so old, there must be other Earth-like
planets that could have evolved life millions of
years before us. Even if faster-than-light travel is
impossible, over millions of years a civilization
could easily colonize the whole galaxy. So where’s
the evidence of that? One of the problems with
answering this question is that humans are pretty
bad judges of scale. We think a century is more than
a lifetime. We take one quick glance at the sky and
say: “Nope, can’t see any aliens, must be no aliens.”
The Fermi Paradox assumes that since we
can’t ﬁnd evidence of aliens really easily, there
must be no aliens. It doesn’t take into account
the fact we really haven’t been looking for very
long, or very far.
You might think that because we’ve shot
probes past all of the planets, we’ve pretty much
explored the whole Solar System. But we’ve
only seen a tiny fraction of what’s in our own
backyard. There could be alien probes observ-
ing Earth right now from, say, the Asteroid Belt,
and we wouldn’t be able to tell.
Many people also think we should be able
to pick up radio signals from other civiliza-
tions around other stars, that the sky should be
full of radio chatter and alien TV stations and