Life On Other Worlds: By The Numbers


When it comes to the possibility of life on other worlds, there are three categories to consider:

  • Life of any type
  • Intelligent life of any type
  • Intelligent carbon-based life forms

For practical purposes, the third category is really the only one that concerns us.  The first type might be nothing more than a colony of microbes.  Sure, it's "life"… but so what?

The second type might be 'intelligent', but most likely we'll never know.  It could be anything from some parachute-shaped beings floating around in an atmosphere of pure methane to some formless creature living 10,000 feet below a sea of hydrochloric acid.

And then there's communicating with them.  We've been so brainwashed by Hollywood that I'm sure the first impulse of a great number of people would be, "Just build a voice translator and we'll be able to understand them perfectly!"

Sorry, it just doesn't work that way.

Nor, after such a long journey, are we going to be equipped to fly through an atmosphere of pure methane or dive 10,000 feet beneath an ocean of hydrochloric acid.

Again, it just doesn't work that way.

No, for our purposes, we really have to be talking about carbon-based life forms similar to us, and from a world similar to ours, if we want to have a real chance of communicating with them.

And that's really what it's all about.  If we sent back a signal to Earth declaring, "We've found alien life forms floating around in an atmosphere of pure methane!", well, everyone's going to find that pretty exciting for a minute or two, then it's back to the daily grind.

If we can communicate with them, however, then there's a real chance that we'll learn something that will vastly improve mankind, such as a new, pure form of energy or a transgalactic space drive.  Or, just as likely, something you and I can't even conceive of.

So, what are the odds of there being intelligent carbon-based life forms out there living on a world similar to ours?  Let us construct such a scenario step by step and see.

First, we need a sun.  But it has to be the exact size, type, phase and age.  You might think most suns are somewhat alike, but that's far from the truth:

A sun much smaller than ours wouldn't provide both the heat and solar wind so necessary for weather.  A sun much larger than ours would bake the planet to a crisp.  It has to be exactly the right size.

And you saw in the video how wildly different the sizes of suns can be and, for that matter, how far, far down the scale we are.  It's almost like ours is the smallest sun out there, or near to.

You also saw how many colors of suns there are.  Carbon-based life forms require a red sun, such as ours, which means we need to catch the sun at just the right phase.

And suns grow hotter over time, then cool, so we have to catch it at just the right age.

So, given what you saw in the above video, what are the odds the sun will be exactly the correct size, type, phase and age?

Now we need a planet that's a precise distance from the sun.  Too near and the oceans boil away; too far and it's a frozen ball of ice flying through space.

And certain laws in the carbon-based universe are immutable, such as "organic matter decays over time."  So, when it comes to the size of the sun and the planet's distance from it, you can't simply say that any size of sun will do and then place the planet farther away so it doesn't burn up. At some point fairly quickly the planet is going to be taking 500 years to circumnavigate the sun and organic matter such as seeds and eggs simply wouldn't be able to last out the duration.  A few spores might, but life as we know it would never flourish.

Plus, in order for the planet to have distinct seasons, it must circumnavigate around the sun in a precise elliptical orbit and have a particular tilt to its axis.  It can't be too near at its closest point or too far away at its furthest or it'd burn up or freeze over.  And if the tilt of the axis isn't far enough, the seasons aren't distinct enough to signal it's time for a change in the cycle of life, yet if it's tilted too far, the world would turn into Antarctica every winter and the Sahara Desert every summer.

So, given the vast size of an average solar system, what are the odds that a planet would end up that exact distance from the sun, and have that precise elliptical orbit and axis tilt?

Next, we need a moon so as to churn the oceans around.  Without tidal action, our planet would be a rotting cesspool.

Moons such as ours are formed by a huge asteroid colliding with the host planet, throwing tons of debris into space which eventually coagulates into a moon.

But if the asteroid is much larger, or strikes it more head-on, it could destroy the entire planet.  That's what the Asteroid Belt is in that big gap between Mars and Jupiter; a shattered planet.

But if the asteroid is much smaller, or hits the planet more of a glancing blow, not enough matter is flung into space to form a moon and the debris eventually settles back.  So the asteroid has to be just the right size and hit it at just the right angle.

Plus, the moon that's formed has to be exactly the correct size and distance away from the planet so that its gravitational field affects the tides below just enough, but not be overwhelming.

So, what are the odds that an asteroid would even hit the planet in the first place, and then be just the right size and hit it at just the right angle so as to throw off just enough material to form a moon that exerts just the right amount of gravitational influence on the planet below?

And we certainly need an atmosphere breathable by carbon-based life forms.  I'm sure you've read how wildly different the various atmospheres of our neighboring planets and moons are.  One will be pure methane, the next will be a delightful mix of sulfur dioxide and semi-frozen helium.

Plus, the atmosphere has to be the exact correct thickness in order to trap exactly the right amount of heat from the sun.  Too thick and you end up with a steam bath like Venus; too thin and the solar winds sweep it away and you end up with a barren rock like Mercury.

So, given the incredibly vast array of chemical possibilities, what are the odds that a planet will have an atmosphere composed of material that can sustain carbon-based life forms, and be the perfect thickness?

And here's a small catch:

When a planet's the perfect distance from the sun, with just the right thickness of air, it's still so close to the sun that the solar winds will sweep the atmosphere away.

Unless it has protection:

So, what are odds that a planet would even have a core in the first place, and, of all the possible metals in the universe, the only metal of them all with a large accompanying protective magnetic field?

Okay, let's do some rough math and then we'll continue:

  • It's a billion-to-one odds that the sun will be exactly the right size, type, phase and age.
  • It's a billion-to-one odds that the planet will be the exact correct distance from the sun and have the perfect elliptical orbit and axis tilt.
  • It's a billion-to-one odds that a large asteroid will strike the planet and be just the right size and strike it at exactly the right angle to form a moon the perfect size and distance from the planet.
  • It's a billion-to-one odds that the planet will have a breathable atmosphere with the perfect thickness.
  • It's a billion-to-one odds that the planet will have a molten iron core.

Give or take a few percentile points, of course.

All right, let us assume the odds have been overcome and the planetary cauldron awaits the first sign of life.

What are the odds of life appearing out of nowhere?

But it does.  It thrives and mutates and grows for millions upon millions of years.

Right up until about 65 million years ago.

At the time, our ancestors were small, muskrat-like creatures scurrying around the underbrush while dinosaurs ruled the earth.  Things had already been that way for a couple hundred million years, so there's no reason to assume they wouldn't still be that way today if it hadn't been for the next billion-to-one circumstance, the Cretaceous-Tertiary Extinction Event.

As before, the asteroid that struck the Earth had to be exactly the right size.  Much smaller and it wouldn't have blanketed the planet with dust and storms (which caused the major vegetation to die off and the dinosaurs to wither away), and if it had been much larger, it might have totally destroyed the planet's ecosystem and sent us all back to the microbe stage.

So, what are the odds that an asteroid would hit us at all, be precisely the right size, and hit us at that particular point in our planetary evolution?

But it did.  The dinosaurs conveniently skedaddled out of the way and the Day Of The Muskrat arrived.  65 million years later and I'm sitting here writing about it, eagerly awaiting contact with some extraterrestrial carbon-based life forms.

But getting us this far was only half the battle.

Next up, the species, itself, must show it can survive the test of time.  How many worlds came this far, only to fail because some intangible essence, such as a core belief in God, was missing from the puzzle?

But how does the concept of God begin in the first place?

So bear this in mind; that many worlds might have advanced to a certain degree, but some core, intangible factor such as God was missing from the greater scheme of things, keeping them in the dark ages of Us Against Them, Good Against Bad, and thus keeping them from evolving technologically to the point of deep space exploration.  They would tend to evolve to the point of nuclear technology and, without some greater belief staying their hand, would presumably start lobbing nukes at one another as fast as they could.  They might hold off for a while, but eventually someone would crack, and that'd be that.

So, what are the odds of God showing up?

And there's a timeline factor that must be considered.  Civilizations rise and fall, as do entire planetary ecosystems.  There are two factors, alone, that could impact our little hunt for intelligent life quite severely.

The planet is roughly 4½ billion years old.  Let us say that we have been cognizant enough to handle the concept of meeting alien life forms in a calm, intelligent manner for the past 100 years.  That's probably being too generous (the 'War of the Worlds' radio broadcast which faked an alien landing and panicked half the nation was only 70 years ago), but I like round numbers.

So, for approximately 0.00000000023% of the planet's history, we have been receptive to meeting aliens in a calm and intelligent manner.

Since we also need a future date in order to get an accurate figure, we must first look at two scenarios:

  1. Mankind takes itself out of the game.  With biotechnology becoming available to every Joe Terrorist, it might only be a matter of time before some bioterrorist wannabes accidentally unleash something that spells the end of humanity.  And, while it could be something a thousand times more deadly than Ebola, it might be something relatively benign that merely enters the reproductive system and renders every person on the planet sterile.  And, unlike a 'killer virus', the extent of the problem wouldn't be known for months, giving it plenty of time to encircle the globe.
  2. And, lest we forget, we've got another full-blown Ice Age just around the climatological bend.  It should be quite interesting watching the population of North America cram itself onto the Panama Isthmus.  It's my guess that they'll be much more interested in that thing called "survival" than deep space exploration at the time.

But let's be generous and assume that (1) mankind doesn't wipe itself out and (2) the next Ice Age is still 10,000 years away.  Adding the past 100 years to the future 10,000 years, we have a figure of 10,100 years as a time frame to work with.

That's 0.0000023% of our planet's existence that we have been, and hopefully will be, receptive to alien beings.  That's not much, as these things go, but at least this time we've got some hard numbers to work with.

So, given the infinite vastness of space, and what it takes to make a planet suitable for carbon-based life forms, and assuming other civilizations arose somewhat like we did, what are the odds that we'll meet up with intelligent beings within that 0.0000023% time frame of both planets?

The proponents of the "there are thousands/millions/billions of intelligent civilizations out there" theory basically use a 'by-the-numbers' argument: There are billions and billions of stars in our galaxy, and billions and billions of galaxies in the universe.  Therefore, it would seem obvious that there would have to be — by the numbers, alone — a couple thousand/million/billion advanced civilizations out there just like ours.

But I see the odds a different way.

When you think of how perfect everything had to be to get here; the perfect sun, the perfect planet, the perfect elliptical orbit and axis tilt, the perfect atmosphere, the perfect asteroid creating the perfect moon, another perfect asteroid wiping out a predominant life form blocking our way, and on and on and on, it strikes me that the odds against all of the pieces lining up matches up fairly well in the by-the-numbers game.

And if that's true, then it could very well be that we currently are the only intelligent, sentient, carbon-based life forms in the whole damn universe.

Just call us lucky.