Mystery of the Next Step

Chatting one evening with a friend, the subject of extraterrestrials came up.  “I wonder,” he said, “about extraterrestrial life.  I mean, I believe it's out there.  But, why haven't they contacted us?  Are we the oldest sentient beings in the universe?  Or do they think we're the hillbillies and stay away? Are they avoiding our little backwoods planet, or are they on the way with a conquering fleet?”  Well, that got me to thinking, too.  What are the chances of intelligent life outside our solar system discovering us, or us discovering them?  And why haven't we yet?  Come, Watson; the game is afoot.

First, let’s pick a distance to consider; say, five hundred light years.  Most of the signals of our civilization completely disappear long before reaching this distance, faded and buried in the cosmic background noise.  Signals that MIGHT reach five hundred light years are very few: high power directional radars, high energy lasers, and above ground nuclear detonations.  At five hundred light years distance even these would only be tiny ‘clicks’ of radio or light energy, and would probably not be detectable at one thousand light years.  If there is any chance of discovering or contacting a neighbor civilization, it lies within five hundred light years of us.

About a third of a million stars shine within five hundred light years of Earth.  If we assume most stars have planets (and evidence is building for that assumption), then there might be about a quarter of a million solar systems in that region. Some of these stars just aren't suitable for life, being too bright or too dim, too radioactive or not enough,  too big or too small, too hot or too cold.  Furthermore, many stars have one or more companion stars, which makes habitable planets unlikely in that system.  Let's assume a generous half of these stars have at least a chance for a life sustaining planet orbiting them, about one hundred and twenty-five thousand solar systems.  

The science of the possibility of life is well written about, but let me sum up here the best I can of what I understand.  For life to develop along the same lines as on Earth, we'd need a planet with similar gravity, plenty of water, with a relatively short rotational period, and orbiting within the life-zone of its sun.  Some convincing arguments say we need a moon, since tides seem to be essential to early evolution.  If the conditions were too different, then life may not develop at all, much less an intelligent, technological race. 

The ranges of conditions for life are very broad, though; from world-freezing glaciers to baking aridity to steamy rainforests, our Earth has seen it all. Let's assume that 10% of the remaining solar systems have such a planet.  That's still twelve and a half thousand  planets that could develop life like ours within a mere five hundred light years.  Go outside tonight, look up, and count twenty-five stars; a sister of Earth is probably orbiting one of them.

We know just from looking around us that if life can, it will.  Fly, crawl, or float; eat wood, blood, or manure, life adapts.  Even if the events that led to life here on Earth were unique, I believe life would find a way to use whatever chance it had to get started on these other planets.  It would be asking a lot to assume each planet would develop life, evolve animals, and grow a species to intelligence, but if life can it will, so let's assume most of the worlds will develop intelligent life, creatures we could recognize and understand. If ten thousand worlds within five hundred light years of us have already developed or will soon develop intelligent life, life that survives to develop technology, then the question becomes that much more relevant:  where are they?    

Nobody on Earth has found evidence of extraterrestrial life, at least nothing outside tabloids.  Some of these planets are older than Earth, some younger, but mostly born about the same time.  On Earth life developed billions of years ago, but took its own sweet time to evolve into anything more exciting than worms.  It’s the last one hundred million years that have been the most important to us humans.  Assuming human development is fairly typical, civilizations could have been popping up on these planets every five or ten thousand years for the last fifty million years. 

If planetary development is similar among these planets, that rate may even have increased over the last few million years to every three or four thousand years.  Yet, we have no sign that hundreds or thousands of intelligent, technological species live in our galactic neighborhood.  It seems there should be at least a few species out there, broadcasting radio and television, testing nuclear weapons, beaming lasers into space, tracking satellites with radar.  It seems that someone should be out there, someone we could hear, someone looking for us the same way we're looking for them.  Why are there no signs of our neighbors?

Like Sherlock Holmes, we are forced to accept the only remaining possibility, however unlikely.  Perhaps it’s because they aren't there.  We, Homo Sapiens, are still here, a species growing in the face of adversity.  Plague, war, famine, and stupidity only slow us down, make us stronger.  If these extraterrestrial brethren of ours were like us, then they were survivors, too; so what could have taken them out?  The mystery is very personal to us, since we seem doomed to disappear also.

Since nobody is out there, it's obviously an inside job.  That is, there doesn't seem to be any interstellar wars going on, and the very scale of space means no single disaster could have wiped everybody out without leaving behind evidence, so the cause of the disappearances likely came from within each species.  Perhaps some of our neighbors committed suicide through war or pollution, but it's very unlikely hundreds or thousands did so.  And even so, it seems likely there would be some evidence of the suicide, a legacy of electromagnetic signs.  Not only are they not there, they don't seem to have been there recently.  They didn't die, didn't get killed, and have been gone long enough that the trail is cold.  The inescapable conclusion is they left, and soon after developing technology. 

Thanks to technology, human understanding is approaching the very basic concepts of our universe.  Once a species reaches the point of written language, knowledge begins to accumulate, allowing the talented and interested members to start their own search for further knowledge where others left off.  Knowledge begets technology, which begets more knowledge and more power to use that knowledge to create more technology. 

In just a thousand years, this feedback cycle has taken humanity from the Dark Ages to the Moon, even outside our solar system.  As we live longer and longer we are exposed to more and more knowledge.  We are able to pose questions and solve problems beyond the understanding of previous generations.  Where will this lead us?  How long before humanity masters space, time, matter, and energy?  How long before our descendants find the answer to a question we don't even know enough to ask?  How long before Mankind breaks the surly bonds of gravity, flees the cage of our flesh, and we transcend ourselves?

In Arthur C. Clarke’s novel ‘Childhood's End,’ Earth was visited by alien constructs studying the transcendent disappearance of mature species, and they had come to Earth because humans were on the verge of transcending into another kind of existence.  Are we truly approaching  transcendence?  Man has come from telegraphs to supercomputers in a single century; where will we be one hundred years from now?  Two hundred years ago atomic theory was born; what will we learn about the nature of the universe in the next two hundred years?  In five hundred years Mankind could easily be gone, transcendent, vanished into an existence we cannot imagine today.

And here is the solution to our mystery.  If the cycle is that rapid for our stellar neighbors, then we now know why we have no evidence of extraterrestrial neighbors.  The period a species is capable of being detected and detecting others is less than a tenth of the average time between the possible rise of civilizations.  This makes the odds of having coexisting extraterrestrials about the same as cutting an ace from a deck of cards, or rolling craps on your first roll at Las Vegas.  If the pharaohs had known how, they might have heard the last voices from a soon-to-be-gone neighbor.  By now their radio broadcasts, television signals, nuclear tests, and all other evidence would be long past us, leaving the silence of an abandoned house.  And we humans will be long gone before the next race rises to look up and out, listening . . .

Watch out for that next step, neighbor . . . it’s a doozy.