5 Insane Theories About Why We Haven't Discovered Alien Life | Cracked.com

5 Insane Theories About Why We Haven't Discovered Alien Life | Cracked.com

It is reasonable to argue that the human race may never encounter an alien civilization.

The enormity of the universe creates a statistical likelihood that many planets must be capable of supporting life; and the imperatives of nature seem to suggest that if life can exist, it will. We can therefore safely assume that life exists elsewhere in the universe, perhaps on untold billions of worlds. For the sake of an hypothesis, let's assume that there are a quadrillion worlds capable of supporting life, and that life will eventually spring from all of them.

But the missing part of the equation is that life does not equal technological life. What if there is only a one in a trillion chance that life can evolve into a technological civilization? Given that assumption and our earlier assumption of a quadrillion worlds teeming with life, there might then be only a thousand technological civilizations across the entire span of the universe, and they may be so many light-years apart that they are highly unlikely to encounter one another, especially if we determine that the speed of light remains the limit of traveling speed.

Is it reasonable to assume that civilization is so unlikely to evolve from life? We don't really know, but we do know that our own existence is the result of an accident. The dinosaurs ruled the earth for hundreds of millions of years and made, to our knowledge, no progress toward technology. Moreover, the big lugs and their predatory ways prevented the development of any other large beings. The primitive mammals in that era were so tiny that they could survive only because they were essentially unnoticed by the dominant life-forms. Take away the great extinction event, the Alvarez Impact, and our own planet would still be teeming with non-technological life, as many others in the universe may be.

Furthermore, there are other scenarios which could have prevented the development of civilization. The precise timing of the Alvarez Impact helped to foster technological life on our planet, but it would have been a different story if the same impact had happened much earlier, or if a second similar event had occurred in (let's say) 1700, thus throwing everything right back to square zero. Moreover, even if it is not overwhelmingly difficult for technological civilizations to develop, their life-spans may be short and unlikely to overlap with one another.

Let's face it, we ourselves are the result of a serendipitous concatenation of circumstances and if any link in that chain had been different, nobody would here to be ask these sorts of questions, and there is no guarantee that anyone will be here to ask them in another thousand years or five thousand. There could easily be another extinction event, either sent by the cosmos or of our own making.

Of course I have fabricated all of the numbers in these calculations, and they may all be dramatically wrong. We simply don't know how many life-sustaining planets exist. There may be septillions. And we cannot calculate the likelihood that life will result in technological life. It may, in fact, be nearly inevitable. And the speed of light may not be anywhere near our limit. And we may figure out how to live without destroying our world or each other.

But I think my assumptions conform fairly well to what we know today. I think that there must be other technological civilizations somewhere out there among all those galaxies, but fewer than we once hoped, and much farther apart than sci-fi stories have led us to dream. We may never find those needles in the haystack of the universe, even if the speed of light is not an absolute maximum. And if the speed of light really is our limit, our own civilization's shelf life will probably expire before we ever become aware of other civilized worlds.

Reader comment:

Thoughts:

The Doomsday argument is basically specious because it's pretending humans are like tanks. The statistical method of estimation it uses was developed in WWII to estimate German Tank production. You simply looked at the serial numbers on captured tanks and said "since most of the tanks have serial numbers in the low thousands or hundreds it is unlikely that they have produced tens of thousands of tanks and very unlikely that there are hundreds of thousands." Tank models and have sequential serial numbers and limited production numbers. The Doomsday Argument says that there have been something like 60 billion humans born so far and there is a 95% chance that there will only be 1.2 trillion humans ever, ergo the human race will go extinct by ~120 generations from now if the world population stabilizes at 10 billion, more than 1000 if it dwindles to a more sustainable 1 billion. The problem is that they generally count from around 10,000 BCE not the origin of language- using humans around 70,000 BCE. That moves the total number of humans up to 100 billion instead of 60 billion. If you pick the origin of anatomically modern humans who don't appear to have had language skills, that pushes back the threshold to 250,000 BCE or earlier, you're up to 200 billion. And evolution forbids you to point out a specific organism and say "that was the first human". Strictly speaking, dinosaurs still exist because birds are defined as members of the dinosaur group now. While the living bird (and dinosaur) population is sharply down in the last 12,000 years thanks to us, there's no chance that a meaningful percentage of all the birds currently living being a meaningful percentage of the birds that have ever lived, implying that birds as a class will continue to exist for several millions of years more. Anatomically modern humans without the ability to use language ARE extinct though, and there were only about 100 million of them ever. It is very probable that if population stabilizes to a sustainable level, humans will have evolved into a new species within 20,000 years. It's actually virtually certain. Civilization may be ongoing even though the biological species has changed though. So the Doomsday Argument isn't applicable to the existence of civilizations.

(NOTE: If that wasn't clear the point was that there's no fixed beginning point for a species, only the point at which its ancestors diverged from a common ancestor, unlike a serial numbered manufactured product. Evolution is an ongoing process. Reproductively speaking, all the "races" are still one species, because reproduction is still completely possible between races. There are probably only a very few populations that have had true sustained reproductive isolation and the divergences that did develop were mostly disease immunities. (Sickle-cell anemia is a disease immunity.) So it is completely conceivable that a technological civilization descended from us biologically and culturally could persist after homo sapiens has ceased. The argument depends on a misunderstanding of the idea of species.)

It is likely that practical interstellar travel and communication ARE impossible though. Intelligent life may be quite common, but it is simply impossible to get close enough to it to communicate. Someone suggested interstellar radio communications and I responded thus:

Actually, I'm afraid that radio waves do "decay" from a practical standpoint. Broadcast radio waves outside the Earth's atmosphere expand in a theoretically infinite sphere, but the surface area of that sphere is also in proportion to the square of the radius. So every meter further away from the radio source you get the concentration of the broadcast radio photons in the leading edge of the broadcast gets less dense. Individual radio photons are cheap, but if you want a broadcast on a given frequency to be as powerful and as easy to detect from a light year away as it is from a light minute it has to be 525,600^2 more powerful. Put that another way, light waves are basically the same as radio waves, and Earth is about 10,000 Earth diameters from the Sun. If the Earth was on the surface of the Sun, it would be getting hit by about 100 million times more light. By the same token, the Sun is something like 1.5x as far from Mars as it is from the Earth, so sunlight is twice as intense here. Alpha Centauri is something like 25,000 times as far away from the Earth as the Sun is, so the Sun is less than one six millionth as bright there. And since our little toy radio transmitters putting out vastly fewer photons per square inch then the Sun, the signal was that much fainter to start with. That's why radio telescopes are the size of small towns.

You can get around this by using the same principle as a laser to make a powerful coherent beam directed at a single point in space, but lasers aren't perfectly coherent and you have to know where there's someone listening in the direction you are pointing the laser. So radio communications between distant star systems are very impractical, and it's exceedingly unlikely that if any civilizations within 100 light years exist they have noticed our radio broadcasts. With the background radio static it's simply like trying to differentiate an individual light bulb on Earth from Jupiter. I'll also toss out that your positing that the K-T extinction was a necessary condition for the appearance of intelligent life is probably wrong, leave aside that people are now debating whether the impact or the Deccan Flats supervolcano were the cause of the extinction. (The question of what the hell the odds that a major impact and one of the planet's worst supervolcanos happening at the same time without having anything to do with each other is another issue, although the idea that an impact could cause a supervolcano on the other side of the Earth makes a lot more sense then a supervolcano attracting an asteroid.)

The conditions for intelligence arising seem to be animals that behave socially using tools. That's it, and it still took 3 million years to reach critical mass. And there's no reason to think tool use is something only mammals can do. Any one of the herbivorous dinosaur species that "flocked" could have done it in principle if circumstances had arisen where a bipedal herbivore was selected for and had forelimbs that could be used for grasping. If you're looking for a likely culprit for causing human evolution, the Ice Ages seem like a better choice, and the cause of these seems to have been a combination of the semi-enclosed Arctic Ocean and the appearance of the Himalayas (lots of shiny glaciers near the equator reflecting sunlight and cooling the planet).