“There are maybe 30 million species on the planet today—10 to 30 million. If we look at the fossils, there are hundreds of millions of species in the past. And one time on Earth has intelligence arisen to the point where we can build a radio telescope (which is the definition of intelligence to a radio astronomer). One time out of hundreds of millions of possibilities. That’s an astronomically small number of intelligences that have arisen—just one.”
Peter Ward -paleontologist and professor of Biology and of Earth and Space Sciences at the University of Washington.
The “Rare Earth” hypothesis is the idea that life is a staggeringly
unlikely event, and that the reason we haven’t seen hide nor hair (nor
scale nor weird gel-layer) of aliens is that there aren’t any. It’s
had some time in the spotlight, it makes us sound very important, and
it’s wrong.
The Rare Earth argument ignores a number of essential factors, the
first being how staggeringly huge the numbers involved are. Even the
Milky Way has 200 to 400 billion stars, and it’s only one of a hundred
billion galaxies in the observable universe, and there have been
billions of years for things to happen. Countering “it’s really
unlikely” with “but there are lots of things!” might sound weak, but
it’s the Rare Earthers who are taking the burden of proof - claiming
that nothing happens anywhere else ever. The more places there are,
the worse their argument gets.
Geologist Peter Ward and
astrobiologist Donald Brownlee, both of the University of Washington have outlined a
short list of conditions needed:
Right distance from a star; habitat for complex life; liquid water near
surface; far enough to avoid tidal lock; right mass of star with long
enough lifetime and not too much ultraviolet; stable planetary orbits;
right planet mass to maintain atmosphere and ocean with a solid molten
core and enough heat for plate tectonics; a Jupiter-like neighbor to
clear out comets and asteroids; plate tectonics to build up land mass,
enhance bio-diversity, and enable a magnetic field; not too much, nor
too little ocean; a large moon at the right distance to stabilize tilt;
a small Mars-like neighbor as possible source to seed Earth-like
planet; maintenance of adequate temperature, composition and pressure
for plants and animals; a galaxy with enough heavy elements, not too
small, ellipitcal or irregular; right position the galaxy; few giant
impacts like had 65 million years ago; enough carbon for life, but not
enough for runaway greenhouse effect; evolution of oxygen and photosynthesis; and, of course, biological evolution.
Claims that there aren’t many suitable planets over all these
stars are like hiding in a closet and claiming there’s no such thing as
coffee tables - we’re now detecting planets at an ever-increasing rate,
because now we have technology actually capable of detecting planets.
Almost as soon as we try any new planet-detecting technique it detects
a whole bunch of the things. We’re even edging into the ability to
find Earth-size planets, and what do you know? There they are! And
some even have water!
The second slip-up is ignoring the
suitability of the laws of physics to life - or rather, the suitability
of our form of life to the laws of physics. The idea of someone sitting
in pre-existence limbo and tuning the weak nuclear force in order to
create bald monkeys is patently ridiculous, as is the idea that only a
tiny range of values could give rise to any repeating pattern - our
pattern, DNA, is just the one that happened to work for the collection
of constants we call reality.
Once life is possible in a
universe, expecting it to occur in one place only is like leaving a
loaf of bread and expecting exactly one slice to go moldy. Life just
happens here - thermodynamic math has shown that amino acids simply
will be built anywhere their components can be found. Since those
components are on the periodic table, the literal “this is what happens
in this universe” list, they’re going to be all over. Assuming aliens
don’t come up with another pattern anyway (increasing the odds again).
Claiming
that we’re the only life in existence is a combination of ignorance and
self-importance that should have a livejournal, not a scientific
journal. The important work is getting ourselves out there and seeing
who and/or what we can find.
Posted by Luke McKinney.
Related Galaxy posts:
MIT Asks: How Would Extraterrestrial Astronomers Study Earth?
“The Great Silence” -A Galaxy Insight
Harvard-Smithsonian Scientists Zero In On Key Sign of Habitable Worlds
Cruising the Goldilocks Zone -The Search for Super Earths
Dead Zones in the Search for Extraterrestrial Life
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