How Likely is Extraterrestrial Intelligence? Part 1

Two answers on that one.

First, given the vastness of the Universe and the sheer mind boggling number of stars and potential planets, it is pretty much inevitable.

However,

Given the incredible odds of many of the "processes" required, they may be few and far between.  Most people have heard of the Drake Equation, which attempts to predict the number of intelligent, communicative civilizations out there.

In short, it looks like this:

 


N = Total civilizations.  Each term is multiplied together to get a net product.  Many of these values are unknown and must be guessed at, which leads to a pretty large variance of the N value.

R = Total number of stars in the galaxy
Fp = The fraction of those stars which have planets
Ne = Number of Planets each star has, on average
Fl = Fraction of Planets which develop Life
Fi = Fraction of those planets which Life becomes Intelligent (self aware)
Fc = Fraction of those planets with Intelligent Life which learn to broadcast into space
L  = Length of Time such civilizations broadcast into space

The first Term, R, is reasonably well known - around 200 billion

Only recently (last 2-3 years) has Fp and Ne been narrowed down a bit.  Although Drake estimated it to be about one for each term, I believe we can be more generous here.  I believe, ultimately, planets are pretty commonplace, at about five or so per star.  Our star has 8, and I'm sure there's stars out there with many more.  Many near the Galaxy's core, may not have planets, as frequent close encounters with other stars may have dislodged those planets from their orbits and sent them careening through interstellar space.  It's pretty much a given that any planet wandering interstellar space is too cold for life.

As alluded to before, planets aren't likely to produce Life if they're too hot, like Mercury.  And, they're not likely to develop Life, if they're too cold, like Jupiter's moons Ganymede or Callisto.  Forget Jupiter.  Gas Giant planets are very inhospitable.  No solid surface, high concentrations of poisons like Hydrogen, or inert like Helium, extremely violent winds, lethal levels of radiation.  Hydrogen does not form complex bonds, and in large quantities, tends to rip apart complex bonds that are necessary for life.

Life needs stability, too.  A wild, swinging orbit that goes from Mercury's distance to Jupiter's does not lend itself to life, either.  To form and keep life, a planet should be large enough to hold onto a protective atmosphere.  The moon is in the same orbit as Earth but with no atmosphere: it is perpetually hammered by raw solar radiation.  Mars is almost big enough, but in the distant past, it cooled enough for its core to stop circulating around, so it no longer has a global magnetic field.  Without that field, Mars's atmosphere was stripped away by the Sun's particle flux, and it, too, gets hammered hard by radiation.  If Mars has any life, it's buried and forever banished to single cell status.

In summary, Life is probably pretty uncommon - probably only developing in one of every 100 to 1,000 systems.

Now, here's the kicker.  Going from single celled to multicellular was likely a huge jump.  It's reasonable to assume that single celled life cannot attain intelligence.  Far too simple.  To develop the complexity that breeds intelligence, cells need to band together in huge numbers.  Earth was populated by single celled life for much of its history - close to 3 billion years.  It was only about 600 million years ago, that nature figured out, Aha! Together we are strong.

But, multicelluar life is clearly not enough.  Earth grew multicellular life for 600 million years before humanity showed up on the scene.  Nature does not deliberately spawn intelligence.  Instead, every species tends to respond to local pressures, adapt to local conditions.  The Predator-Prey battle was a pretty critical factor, causing numerous varying arms races for speed, size, strength, and intelligence.  Only the fastest Prey escaped.  Only the fastest Predators caught Prey.  Competitive species battled it out for survival, both "improving" as a consequence.  On Earth, Predators are generally smarter than Prey.  This is because it's harder to plan an attack than it is to escape.

So, out of 600 million years of multicellular life, high intelligence has only been around about 2 million years.  One could argue that Cetaceans (Whales etc.) have high intelligence.  True, I believe they do.  But, technology requires the species be on land.

Why?  Because it's pretty difficult to build anything permanent under water.  Humans have hands.  This is really important.  Fins just aren't good for any kind of craftsmanship.  Nor writing.  And forget metalworking.  That requires fire.