Sci-fi authors and have been inventive
in creating all kinds of various aliens. From the alien in Alien with
acid for blood that uses humans to gestate past the larva stage, to
silicon based lifeforms in Star Trek such as the Tholians, to the
giant bird like slash dinosaur creatures of Shipstar, to the Wookies
of Star Wars. We can see that imagination knows no bounds, but what
is the actuality that any of these aliens could in theory be real?
Are they potentially realistic?
We now know that space is full of the
key ingredients of life as we know it. First is water, think comets
and Europa. Europa is a frozen water world moon of Jupiter and its
speculated that Ganymede contains more water than the entire Earth!
(see
underground ocean on ganymede). It’s also theorized that comets and asteroids delivered Earth’s
water over the course of millions of years (see
oceans arrived early on earth). Second is sugar. Sugar has been discovered out in space as well
as other prebiotic molecular species such as amino acids (see
prebiotic molecules
and
building blocks of life).
It’s no wonder our bodies are ~70%
water, our DNA contains sugar, deoxyribose, and proteins are chains
of amino acids; and proteins are produced by the genes embedded in
out DNA. In fact, there have been meteorites found that contained
off world amino acids, such as the Murchison meteorite and several
others since then. Roughly 500 amino acids are thought to exit and
Earthly biology uses 20 of them, 9 have to be ingested since they are
not produced by our bodies.
Certainly DNA has been a successful
molecule for storing and spreading information, it has dominated life
on Earth, but is there another way for biology to spread information
and ultimately for life to thrive? I am reminded of a Voyager episode
where the crew discover a species known as 8472. It turns out
species 8472’s DNA has a triple helix instead of the Earthly double
helix of our own DNA. Is a triple helix DNA molecule possible? We
know that DNA came from RNA, but where did RNA come from? When and
where did it begin? These questions are outside the realm of
Evolution and are concerned in the study of Abiogenesis (see
Genesis by Robert Hazen).
It appears life exists in every niche
on Earth, even in the most extreme environments. These Extremophiles
are thought to be the first life on Earth, the Archaea if you will,
and the reasoning goes if they can exist in such extreme places on
earth then certainly they can be found in the various extreme
conditions that space provides. Especially if space is pervasive in
prebiotic molecules. Let us conduct a thought experiment using the
proverbial Drake Equation to guesstimate the chances of intelligent
life in our galaxy. It is as follows:
# of stars: 100 to 400 billion,
so we’ll go with a conservative number at 200 billion
% of stars with planets: 0.6 to
0.9, it appears that star formation goes hand in hand with planet
formation, but we’ll go with the conservative estimate at 0.6
% of planets in the habitable zone:
around 1/100 according to the latest surveys
% of habitable planets with life:
0.5 is a good number because either a planet has life or doesn’t,
but again we’ll go conservative here and guess at 1/100, we enter
uncharted area here
% with intelligent life: totally
unknown here so go conservative at 1/1000
200e9 * 0.6 * 1/100 * 1/100 * 1/1000 =
12,000
Wow that’s potentially 12 thousands
planets in our galaxy with intelligent life on them!! We can adjust
the values to develop a range with N being the number of planets with
intelligent life. It comes out to be:
1e6 >= N >= 3000
So, we can have anywhere from 1 million
to only 3 thousand, personally I think the 12 thousand is a pretty
good number. So far, we only know of one planet with (supposedly)
intelligent life on it. Here on Earth we have several smart
animals that can demonstrate a relatively higher intelligence.
Namely, certain bird species such as magpies, crows and ravens, elephants, whales, dolphins, and certain species of dog. The
smartest animals of course are our cousins, the great apes
specifically chimpanzees and bonobos (we share ~95% of our DNA with
them).
Star Trek has been criticized for
having aliens humanoid and too human like, but I’m convinced that
if intelligent life exists outside of our solar system, it would be
humanoid in form (see
aliens-will-look-a-lot-like-us). This argument was put forth by several
scientists, one of them [University of Cambridge paleontologist]
Simon Conway Morris even argued aliens would be as specific as being
bipedal primates! Also, [Harvard University biologist] Ed Wilson
argues for humanoid form. However, a number of scientists disagree
such as, Josh Timonen of the Richard Dawkins Foundation. See
will-e-t-look-like-us
for the ongoing discussion. Also,
is-there-any-plausible-reason
In general, I think the common thread
that makes an animal smart is having a big brain, stereo vision,
bilateral (but not necessarily bipedal), and dexterous appendages
such as hands, etc. for tool use. These, I feel are the necessary
characteristics for intelligent life, hence the humanoid form. If these conclusions aren’t so far
off base then maybe the aliens portrayed in sci-fi namely Star Trek
and Star Wars give us a slight glimpse of what’s really out there!
