Human beings are obsessed with the possibility of life on other planets. Countless movies, books, and television shows are centered around alien civilizations, and there is an entire subculture of people devoted to the idea that aliens not only exist, but have already visited our planet for the inexplicable purpose of livestock mutilation and the molestation of the barely-literate.
However, we can say with a candor close to absolute certainty that nobody on Earth will ever see warp drive starships or quad-breasted space women from the Crab Nebula, because for a number of reasons, the chances of us ever meeting any aliens are slim to none. Why? Well ...
#5. If They Exist, They're Likely Too, Well, Alien
Our concept of alien life is firmly rooted in the idea that it would be comparable to life on Earth. Almost every major alien race in the realm of science fiction and fantasy has been humanoid -- the Klingons from Star Trek are essentially angry space-cavemen while the Vulcans are virtually identical to human beings. Both Luke Skywalker and Han Solo are technically aliens, despite the fact that they look exactly like two white Earth men from the 1970s, and the Asari from the Mass Effect series look like blue strippers with subdermal cornrows.
Behold, inspiration for decades of uncomfortable Comic-Con costumes.
Even the so-called "eyewitness" accounts of extraterrestrial landings we see on those History Channel UFO specials describe the aliens as being essentially human in appearance, with identifiable arms, legs, eyes, and heads. Hell, even the xenomorphs in the Alien franchise, which were supposed to be inhuman bug monsters, were so close to us they could be played by humans in costumes. The point is, that our idea of intelligent life is dependent upon the assumption that the human race is a common point of reference, despite the fact that in all likelihood this is crushingly incorrect.
But the greater question is, "If aliens aren't going to have boobs, do we even want to meet them?"
The truth is, we don't know the first goddamned thing about what the makeup of life is in the Quasar Nebula or whatever distant star cluster aliens might hail from. The dominant life form on their planet could be a fart cloud of neon gas and space lightning that communicates with a series of atonal whistles, by changing the temperature of the air around them, or even by emitting certain smells (though to be fair, some human beings communicate in this third fashion).
In other words, even the basics of life as we know it on Earth (I.e., that carbon is the base element) is by no means the fundamental rule of the universe. Carbon may not even freaking exist on the aliens' home world. The reason we have yet to make contact with alien civilizations may very well be because we wouldn't recognize them even if they sat down in the booth next to us at Applebee's.
"Sorry, we don't serve hyper-intelligent shades of blue. Store policy."
But even if they were somehow amazingly close to humans in their psychology, their thought process could be significantly different to human in terms of speed and response (an idea postulated by Carl Sagan in the novel-turned-unfortunate-movie Contact). It could conceivably take an alien species several hours, days, months, or even decades to relate a single phrase translatable by human beings. For all we know, aliens have been paging us the same sentence for the past 70 years and we've just been dismissing it as bizarrely drawn-out radio static.
#4. They Might Not Want to Screw Us Up
But let's say that there are aliens out there who, by some random chance, evolved to be close enough to us that we could converse with them. And let's further assume that they don't simply want to destroy the planet and take our gold. They may still have solid reasons for simply not wanting to talk to us.
You can only leave so many crop circles without a reply before you start looking desperate.
If you've ever seen Star Trek (and let's not kid ourselves -- if you clicked on this article, you have seen Star Trek), you may know that the most important rule the crew of the Enterprise follows as they're zipping around the galaxy is the Prime Directive, which they break about eight times an episode:
"As the right of each sentient species to live in accordance with its normal cultural evolution is considered sacred, no Star Fleet personnel may interfere with the normal and healthy development of alien life and culture. Such interference includes introducing superior knowledge, strength, or technology to a world whose society is incapable of handling such advantages wisely … This directive takes precedence over any and all other considerations and carries with it the highest moral obligation."
"And that means no banging! Kirk!"
Basically, the Enterprise cannot interfere with life on other planets in any way, regardless of the outcome. They can't pick one side of a warring alien race and arm them with laser cannons, obviously, but they're also not allowed to bring a starving village a crate of space cupcakes (Starfleet considers these to be the same goddamned thing). They have literally let entire civilizations obliterate themselves for the sake of the Prime Directive. This is an actual theory about extraterrestrial life that scientists call the "Zoo hypothesis", which suggests that super advanced aliens do exist, but they refrain from contacting Earth in order to keep from interrupting our natural evolution and development. Essentially, the aliens are content to sit back and watch until we reach their level, and only then will they share their time-traveling rocket boot technology with us.
What a bunch of shitheads, right? Well, maybe not. Charity, no matter how well-intentioned, can backfire in unpredictable ways. For example, there have been a number of projects to increase the standard of living in Ethiopia, which is a country literally famous for being impoverished. One such project involved installing water taps in Ethiopian households. While this had several incredibly beneficial effects, most notably dropping the infant mortality rate, it ultimately contributed to household shortages. More children means more family members to support, and those water taps weren't spitting out any extra money -- so essentially, the children were surviving infancy only to grow up starving. By solving one problem, another equally devastating problem was created.
"I'm finally over my intimacy issues, but now I have herpes."
In the perspective of the Zoo hypothesis, imagine if aliens had touched down on Earth during the Dark Ages, and instead of face-raping everyone with space crabs, they decided to try and help. So they gave humanity self-perpetuating mooncube energy and advanced irrigation, thereby eliminating the need for any of us to ever compete for resources ever again. The aliens leave, patting themselves on the back for their good deed. However, with endlessly renewable resources, Earth quickly becomes overpopulated, and instead of fighting for oil or whatever, people are vaporizing each other with mooncube lasers just for living space. The aliens come back after a hundred years to check up on us only to find the Earth an ashen, blasted landscape of corpse fumes, and now they have to type up a substantial report explaining their actions to the intergalactic community.
We wouldn't want to have to deal with that amount of paperwork, so it's reasonable to assume that the aliens wouldn't, either. But even if they did, there might be another reason they avoid us ...
#3. We Might Not Be Worth the Aliens' Time
According to the Law of Accelerating Returns, once a civilization begins hitting a real technological stride, the level of advancement will begin to increase exponentially in a comparatively short period. For example, human beings have been trolling around the planet for thousands of years but have seen their greatest advancements (medicine, computers, flight, space travel, etc.) just within the past century. And each iteration of those advancements took less and less time to produce -- that is, the span between no computers and the first computers was much longer than the span between the iPhone 4 and the iPhone 5. Every time we build a house, we don't have to rediscover what a hammer and nails are -- we just take the tools we've already developed and continue to figure out better ways to use them.
"But see, this time, you swing the hammer. That's called 'innovation.'"
Now, let's apply the same logic to a super-advanced civilization of star-hopping aliens. We can assume that "flying saucers" are at the far end of the technological timeline, meaning that by now the aliens have theoretically enjoyed centuries of Accelerating Returns. So, take the last 50 years or so of Earth science and multiply that by, say, 300 or 400. That's the level of technology at which interstellar travelers would likely be operating, and it is far beyond anything our pizza-microwaving asses can even begin to comprehend.
So, what would we have to offer them?
"Come on, the first three seasons of The Wire for an interstellar warp drive is totally a fair trade."
Alien civilizations may not be trying to talk to us for the same reason that we don't spend a whole lot of time trying to talk to goldfish -- we really don't have anything worthwhile to say to each other. Maybe some dimensional-shambling moon lizards noticed intelligent life on our planet and decided to take a break solving Rubik's cubes with their mind fingers to discuss the finer points of time travel with our greatest minds, only to discover that our defining technological achievement of the past three years was figuring out how to rent movies from a vending machine. They would've sighed heavily, climbed back into their star cruiser, and signed into the Galactic Network to remove Earth from the list of potential candidates for the United Federation of Planets.
#2. We'd All Be Dead by the Time It Happens
When we talk about the likelihood of aliens existing, we tend to think about how many millions and millions of planets there are and figure, well, shit, the odds are at least one of them nearby has green people on it we can talk to. But what we tend to totally discount is time.
And Sam Rockwell. He's so underrated.
Think about it; Earth was round for four billion years before humans appeared. Maybe there was a thriving alien civilization nearby, and maybe they mastered space travel and gave us a visit. And maybe all they found here were a bunch of big, dumb lizards. So it's not just that two intelligent, space-faring civilizations would have to arise physically close to one another, but they would have to overlap chronologically, too.
And without making this too depressing, the odds are overwhelming one or the other is going to go extinct before that happens. In keeping with their long-standing tradition of ruining everything for everyone, scientists came up with something called "The Doomsday argument," which is a statistical equation to determine the number of future members of the human race given a rough estimate of the total number of people born so far. Essentially, it is a formula that predicts the maximum number of human beings that can ever possibly be born. And according to the formula, humans will probably be dust long before we master interstellar travel, or by the time any aliens bother to roll up in their flying saucers and show their green faces.
Or before Steven Tyler has to sing a song about asteroids.
The equation basically says that human beings have a 95 percent chance of becoming extinct within the next 9,000 years, which in the grand cosmic scheme of things isn't a whole lot of time. If we want to meet some aliens, we need to hurry up and develop interstellar technology, because they sure aren't in any kind of hurry to contact us.
The Earth is relatively young compared to the rest of the universe, which has theoretically been spinning around in operatic blackness for billions of years. Statistically speaking, any number of the trillions of celestial bodies out there would have produced intelligent life millennia ago -- if they haven't mastered the science of awesome spaceships by now, they probably never will. And if our remaining 9,000-year estimate turns out to be correct, our window to do the same is equivalent to a tiny coiled butt hair on the epic universal timeline of existence.
You are exactly this insignificant.
Even if we do manage to achieve interstellar travel, the Doomsday argument has a "many worlds" application to account for the possibility of multiple advanced civilizations, meaning that any alien life with the presence of mind to build interplanetary flying machines is just as likely to have an equally finite lifespan. So there is a very real possibility that our historic first visit to another galaxy might yield nothing but a bunch of big-headed skeletons and about a zillion gallons of wasted rocket fuel.
#1. Aliens May Not Exist at All
The Rare Earth hypothesis, put forth by two scientists named Peter Ward and Donald E. Brownlee, suggests that since the development of life as it is on Earth was the result of a laundry list of geological and astrophysical events so cosmically random yet so crucially specific down to the smallest detail, it is ball-smashingly unlikely for a comparable civilization to have come into being anywhere else in the universe. That is, while some kind of bacteria or algae or cosmic mushroom may exist underneath some rocks on some far distant planet, the chances of there being another race of intelligent and industrious living things are about the same as you winning the lottery every single day for the rest of your life and then dying on the morning of your 200th birthday after getting struck directly in the face by Doc Brown's time train.
While breeding a Shiny Ponyta.
First of all, the position of a solar system is vital -- if it's too close to the center of the galaxy, everything will get melted by supernova radiation, but if it's too far along the edge of the galaxy it won't be able to support life. Then, the star at the center of the solar system can't be too old, too bright, or too big, otherwise complex life won't develop (complex life is very fussy). Finally, the planet on which said life develops has to be in a perfect orbit. In Earth's case, if the orbit was 5 percent smaller or 15 percent larger we would all freeze or burn to death, respectively. The size and location of our moon keeps the planet on a stable axis, preventing rapid and cataclysmic climate changes -- if we didn't have exactly one moon of the exact shape and size orbiting at its exact distance, we would all be superdead (and likely would never have existed to begin with).
The sequence of geologic eras even plays a crucial part -- if the Mesozoic had occurred after the Cenozoic, for example, the exact conditions needed for human life to develop might never have been met, upsetting the evolutionary order and resulting in a race of dinosaur humans.
Broadcasting "2 Girls,1 Cup" into space also hasn't helped.
Even the other planets in the solar system can have an effect. For example, Jupiter plays a huge role in keeping us all alive because it acts like a giant defensive lineman, blocking us from cosmic debris and world-ending asteroids like a celestial Olin Kreutz. There are innumerable other variables, all of which played a part in intelligent life appearing on just one planet out of an entire galaxy. The odds of every one of those things falling into place in the exact configuration necessary to duplicate both the existence and success of human beings are virtually nonexistent. Therefore, the fact that we haven't made contact with any alien civilizations is probably because there isn't anything out there to contact.