One summer day in 1950, physicists
Enrico Fermi, leader of the team that built the first nuclear reactor, enjoyed
lunch with several fellow physicists. Talk turned to recent UFO reports and the
possibility of faster than light travel. Referring to aliens, Fermi suddenly
blurted out "Don't you ever
wonder where everybody is?" This question led to “The Fermi Paradox.”
Simply stated, if (as we now know) our galaxy
contains billions of planets, many of them Earth-like, why haven’t we ever
encountered any aliens? Earth is young, in cosmic terms. Many solar systems
older than Earth exist, some billions of years older. If life existed on any of
them, it would take no more than 50 million years to colonize the galaxy with
the rocket technology being developed at that time, a blink of the eye in
cosmic terms. So, Fermi wondered aloud, where is everybody?
Over the years, other scientists have suggested various
answers.
Water is essential to life as we
know it. Earth’s water exists on the surface, but for most of the other worlds
in our solar system that possess oceans, four moons, the water is locked underground,
below a frozen surface. That may be common for life-bearing planets or moons.
Many of the planets we’ve
discovered that could have water are classified as super-Earths, planets up to
ten times larger than Earth. The gravity of such planets may well make space
travel impossible.
Futurist and astronomer Seth
Shostak, says that all intelligent aliens may actually be intelligent machines.
We ourselves are on the verge of creating such machines and, within a few
thousands of years, all intelligence on Earth may be machine-based, not biological.
Some scientists suggest that alien
life may be so different from us, we’d never recognize it. Or, perhaps just as
we destroy ants without even realizing it when building a house, maybe all
other life forms have been eradicated. Or they wiped themselves out with
climate change.
Maybe we have met the aliens and
they are us. The “panspermia hypothesis” says life was seeded on Earth by
comets (or alien spacecraft?), making us the very aliens we search for.
Even so, we need to keep looking.
From NASA's search for extraterrestrial life. Credit NASA-HST
On or about the first Tuesday of each month, I write an
astronomy-related column piece for the Oklahoman newspaper. On the following
day, I post that same column to my blog page.
