In sci-fi books and movies, aliens are continually trying to conquer our planet. But this question is seldom, if ever, answered: why would beings from a distant, advanced civilization go to the expense and effort of journeying to Earth to mount an invasion? After all, Earthlike rocky planets are relatively common on the universe—scientists estimate that as many as 30 percent of sun-like stars have them, and the Milky Way alone, by various estimates has between 50 million and 10 billion Earth-like planets situated in the so-called “Goldilocks Zone” of their stars, in which temperatures are sufficiently moderate for life-sustaining water to exist in liquid form. (Here’s an interesting analysis of the so-called Drake Equation.) And our particular planet, as you may have noticed, is the worse for wear, after centuries of humans killing off other species, deforesting vast swaths of the continents, and pumping such astonishing quantities of pollutants into the atmosphere that they’re rapidly altering the climate. If an alien civilization is sufficiently advanced to travel here from another star system, surely they could find a planet to invade that’s still under warranty.

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So if aliens ever are going to invade Earth, they’ll need a pretty good reason. Our feverish, paranoid brains have dreamed up 10 likely possibilities.

1.    Earth has some unique resource that they can’t find closer to home.  Who knows, maybe scandium, a mineral used to make aerospace components, is rare elsewhere in the cosmos. We’ve wiped out civilizations for less.  

2.    They want to prevent a mass extinction of other species. Maybe extraterrestrials see us as the equivalent of the yellow crazy ant, an invasive species that is wiping out Easter Island’s red crabs. Whales, dolphins and butterflies are a lot cuter than humans, you must admit.

3.    They want to enslave or domesticate us. Reality TV contestants notwithstanding, there’s ample evidence that humans can be productive, with the right motivation and guidance. We might make excellent pets, as well.

4.    They want us for food.  There’s genetic and physical evidence that our ancient ancestors were cannibalistic, so human flesh apparently has some nutritional value. The Earth’s burgeoning human population has the potential to provide billions of meals to Aliens, just like some hamburger chain whose name we won’t mention.

5.    They want our DNA. There are numerous sections of the human genome whose function is unclear. It could be that some of these genes might have some value if transplanted into an extraterrestrial species.

6.    They want to wipe us out because they’re afraid of us. Humans are small and physically puny compared to many other terrestrial species, but they make up for it  with their prehensile thumbs, highly-developed intellects, and propensity for brutal violence. If aliens learn of our lengthy history of wars and violent crime, they might decide that it’s prudent to eradicate us before we develop the technology to project our animus on an interstellar scale.

7.    Earth is in the way. We seem to remember that in Douglas Adams’ A Hitchhiker’s Guide to the Galaxy, our planet was demolished to make way for an interstellar expressway.  

8.    They want to test their weaponry. Remember that in 1937, German bombers destroyed the Spanish town of Guernica not so much to help the Spanish fascist cause, but as a preparation for a future war against the French, British and Americans. Maybe the aliens want to see how well their heat ray guns work in a real situation.

9.    They want revenge. Some have speculated that life on Earth is the result of ancient seeding by some extraterrestrial civilization. It’s not inconceivable that some rival bunch of aliens might hold a grunge against us as a result.

10.  For amusement. Humans’ capacity for senseless cruelty toward vulnerable species is well-established. As the Greek poet Bion noted in 100 BC, “Though boys throw stones at frogs for sport, the frogs do not die in sport, but in earnest.” It could be that to some alien species, we’re the equivalent of those frogs.

For more, be sure to tune in to When Aliens Attack this Sunday at 8P et/pt.


  1. Dr. Dimension
    May 23, 2011, 7:21 am

    Your reasoning is almost valid. It just has no historical underpinnings. We threw everything we had at the craft hovering over L.A. back in 1942, and (a)they did not shoot back (b)we did not prevail–they left-(recent experiments prove it was there). We can ignore history and continue speculating in bloodlust.
    You can fabricate a lot of fear-mongering if you don’t look at the facts. There are aliens, (thanks for considering that)and in spite of our history of trying to screw them in a power play, they have done nothing to us at a time when they should have…when nukes were in their infancy. Go back even further, and you will see that they have been noted throughout history, and they have always been benign. Ask Travis Walton. Hollywood took his story of healing and cooperation and turned it into a horror story. We won’t have too long to wait, I think. We can only hope the U.S. hasn’t developed weapons to equal them, because they aren’t going to let us continue warping the fabric of time-space with nuclear explosions.
    Then, there’s ten years of the Phoenix lights without incident from the craft….and no USAF response. What do they know? A lot of the wrong things are being said, but none of the right things. This show is pure propaganda.

    MI ... USA
    March 6, 2012, 2:04 pm



  3. Don't Spaz out Ron
    On a U.F.O
    January 2, 2013, 1:29 am

    if they have been watching us long before Man came to be then how where they watching us???

  4. derek
    May 15, 2013, 2:02 pm

    area 51

  5. ER
    June 14, 2013, 2:50 pm

    I’d say one good reason might have little to do with humans. The aliens could be at war with some other species and earth might just become strategically important. Also humans have proven to be adaptable warriors with a huge population. Properly trained and armed we could be made into the perfect disposable soldiers.

  6. GypsyJewel
    January 2, 9:45 pm

    Well watched to show and it was really good & insightful. Unfortunately when i heard the presidents voice I knew with out a doubt that this was truly science fiction B rated. You see what he would have said first was “Where is my teleprompter”, followed by, “The aliens have assured me that if you turn in your weapons that they will give us the cures to all major diseases”. What he fails to realize is that one of those diseases is “LIFE”. :) and then we would lose.

  7. Bull it
    May 9, 6:06 pm

    It’s unknown!

    - Couldn’t it be, that it’s them who colonized the human on
    - if they were so advanced and also different habitable planets
    The have a NATO sort of agenda or code to not interfere with
    uninvolved planets
    - who not to say that the human race issent the first intelligence
    race to invade. Cause who ever knew we could fly airplane
    - and we probley never make it that far.
    Mother Nature extinct the human race as it did with the Dino’s

    We just don’t know, or if it ever come that far

    “The truth is out there”

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    August 29, 9:35 am

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  9. Zorbledork Tindunglehung
    August 30, 3:12 pm

    You’re all deluded. We have landed and we only wanted some peanut butter cups. We’ll be leaving again soon so you can go back to your boring lives stranded on this planet. Good day to you, Earthlings.