The esteemed astrophysicist Stephen Hawking has assured us that even the biggest and baddest black holes will just evaporate away. But he’s not so optimistic about the mood of any advanced civilizations in the Milky Way galaxy that we might encounter someday.
"We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet," he said on the Discovery Channel's "Into the Universe with Stephen Hawking."
Hawking extrapolates from anthropology to point out that the inferior culture — us in this case — would get the short end of the stick in any such close encounter of the rude kind. Thirty-seven years ago Nobel laureate biologist George Wald expressed similar worries: "I can't conceive of a nightmare as terrifying as establishing communication with a so-called superior technology in outer space."
I’ve mulled over these warnings and have converged on what I think are some simple truths, from a purely astronomical perspective. The bottom line is that I'm not losing any sleep worrying about awaking one morning to see an alien mothership hovering over Washington D.C.
Here are my top five reasons why an intelligent alien species will never invade our planet:
As my colleague Ian O’Neill pointed out in an earlier article, electromagnetic waves from telecommunications leaking off the Earth have now expanded out to a radius of merely 100 light-years. This volume encompasses over 2,000 stars, roughly 200 of which are sun-like. But it covers a feeble one ten-millionth the volume of the galaxy. Even by very optimistic estimates from the Drake Equation, the nearest super-civilization is well over 1,000 light-years away. And they won't know about us, if they can detect a signal at all, until after 3,000 A.D. Earth will show up as having a biosphere in spectroscopic studies taken by very advanced civilizations at farther distances, but that data doesn't give evidence for sentient beings.
If you were walking along the Appalachian Trail, what are the odds the first person you came across was your same age and was born a day before you? Though the nearest inhabited planet could be only 30 light-years away, it is equally unlikely that anyone living there just happen to be close to us in technological evolution (say by a few centuries or even a millennium). The galaxy is very old. Therefore it’s more probable that there are intelligent species that are 10,000, 1 million or even 10 million years more advanced than us. Perhaps they abandoned the plodding vagaries of biological evolution eons ago to engineer a new form of existence, one likely to be practically immortal. Therefore, we have as much in common with them as an amoeba has with us.
Even if we consider there might be civilizations closer to us in evolution, there is absolutely nothing on Earth they need. The stars and planets are made from the same chemical bricks and mortar. There is nothing so exotic as unobtanium, a plot contrivance of the film "Avatar." Transporting any cargo between the stars is infinitely more complex and expensive that simply fabricating whatever you need at home.
Equally implausible is the notion that an extraterrestrial race would want to colonize Earth. First they'd have to clear us out and then clean up our pollution mess and rework the entire biosphere to accommodate them. That's a lot of work to foreclose on an 8,000-mile-in-diameter ball of molten iron and rock. And, the idea of a space ark carrying a boatload of colonists here is a quaint 16th-century notion. It would be much cheaper to undertake a long-term program of terraforming their own planetary system. This would include building huge structures in space such as a Dyson sphere or a star-girdling "ringworld," as envisioned in the 1970 Larry Niven sci-fi story of the same name.
What's more, If a supercivilization had initiated a wave of colonizing other planetary systems across the Galaxy, then they would have likely swept through the solar system tens or hundreds of millions of years ago. The fact that it hasn't happened yet means that it is very improbable colonists will ever arrive at all. This idea is embodied in the Fermi Paradox.
In Damon Knight’s 1950 short story "To Serve Man," aliens befriend us only to eat us. If aliens think humans are a rare and tasty delicacy, they can easily replicate our taste — or DNA — artificially. Old science fiction movies fantasized about aliens wanting our Earth women (like the 1959 "Teenagers From Outer Space"). But the infinite pathways in evolution virtually guarantee that any remotely humanoid extraterrestrials would be very unlikely. So the idea of any cross species romance (as described in some UFO tall-tales) is beyond the impossible.
Altruistic aliens? Forget it. We'd get about as much altruism from an ant colony. As H.G. Wells wrote in his 1898 novel, "War of the Worlds," I’d expect their intellects to be "vast, cool, and unsympathetic."
But what about being malevolent too? Anything smart enough to build starships cannot be pathological, even if they are descended from carnivores as Michio Kaku predicts in the Discovery Channel documentary "Alien Planet." My colleague, radio astronomer Eric Chaisson, has written at length that only "ethical" civilizations avoid destroying themselves.
One might imagine a culture where mysticism and ritual encourage subjugating entire planets in a missionary conquest of the galaxy. But religious zealotry would also get in the way of rationality and therefore scientific advancement. This is a prerequisite for having the technical smarts to achieve interstellar travel. Carl Sagan once mused that, if not for the superstitious Dark Ages, we'd be flying to the stars today.
At best, studying our civilization could be some alien child's science fair project on exo-anthropology.
The distances between stars is so unimaginably vast it cannot be crossed by beings of flesh and blood — and certainly not entire armies. Artificial life could do it, but such entities would be indifferent to us.
This was parodied in a piece written by sci-fi author Terry Bison in Omni Magazine, where two non-biological aliens receive a signal from Earth:
"They use the radio waves to talk, but the signals don't come from them. The signals come from machines."
"So who made the machines? That's who we want to contact."
"They made the machines. That's what I'm trying to tell you. Meat made the machines."
"That's ridiculous. How can meat make a machine? You're asking me to believe in sentient meat."
"I'm not asking you, I'm telling you. These creatures are the only sentient race in the sector and they're made out of meat."
"It seems harsh, but there is a limit. Do we really want to make contact with meat?"
"I agree one hundred percent. What's there to say?" 'Hello, meat. How's it going?'
"Cruel. But you said it yourself, who wants to meet meat?”