Astrogator's Logs

Those who read Standing at Thermopylae know I promised a response to whiny vaporings that appeared on the Apex blog. My response is now up: Steering the Craft. It talks of embroidered jackets and starships, of bread and roses. Here’s the end:

Susan Seddon Boulet, Shaman Spider Woman (1986)

War for the Country
By Viktoría Theodórou – Poet, resistance fighter

A soft mat she found and sat, on the leaves.
A song emerges from the flute of her throat,
low, so her light-sleeping comrades don’t awaken,
just so she accompanies their dreams.
Her hands don’t stay idle, she takes up thread and needle
to darn their socks with the hand grenade
she always carries at her waist, with it she lies and rises.
The grenade in the sock, round and oblivious
to its fire, thinks it’s a wooden egg,
that the country was freed and the war ended
and Katia is not a partisan in the snow-covered woods –
that she sits by the window behind the white lilacs
and sews the socks of her beloved, who returned whole.

Note: For those who are asking, this is an overture. I’ve been invited to respond on the Apex blog. I’ll post the link when I do.

And here’s the link, as promised: Steering the Craft

People versed in the basics of Hellenic mythology know that Athená is the god of wisdom, justice and knowledge — all attributes inherited from her mother, Métis, one of the Great Goddesses literally and metaphorically subsumed by Zeus. Fewer know that Athená is also the god of a particular kind of war: fighting in defense of one’s home.

I have been a vocal and unapologetic feminist my entire life, because I have strong reasons to think that treating women as less than human damages all of humanity. In many ways, I was lucky in the time and place of my birth. Elsewhere/when, given my looks, interests and character, I would be already dead by stoning, burning, drowning, lobotomy… or buried alive in unchosen, coerced domesticity.

Those brave enough to first tackle gender equality often paid for it with their life, health, relationships, reputation, sanity — common fates of anyone who challenges the status quo. Middle-class white women in Western nations, who now make faces at the concept of feminism as démodé, would do well to notice the relentless erosion that happens when we relax our vigilance even slightly. And we still have a long way to go, even in Western nations, even in communities comfortably self-labeled progressive.

Humanity has managed to limp along despite the fierce misogyny that is so embedded in our lives that it passes almost entirely unnoticed. Yet I think we will never truly thrive until/unless we untie that knot. If we do, we may be able to better face the problems that threaten to extinguish us — and perhaps even take to the stars one day, instead of dying out in the churned mud of our own sludge.

I am a feminist and I am feisty. I’m also past fifty, hollowed from the fatigue of chronic pain and my job situation is increasingly uncertain. I would rather have epiphanies in my lab, watch stars fall and flowers bloom, hold my snacho close, dream within book covers, continue to build the universe that I created in my sagas. Besides, I know how little fame and fortune there is in the endless, thankless toil of maintenance. That’s why it’s traditionally women’s work, regardless of culture.

So when another alpha-wannabe knuckle-dragger whines about “PC zombies”and “quality compromised by diversity” without even checking his facts (let alone his assumptions), part of me wants to laugh and ignore him. Especially as I have so many ideas jostling in my head, eager to take form. But that planting will have to wait. Because speculative fiction is my home. Because the world is my home. And I know first-hand how fragile civilization is, and how easily trampled by such boots. So the harvest will have to wait while I don my notched weapons and stand at the gates of my home. As long as I can stand upright, he and his ilk shall not pass.

Images: Top, archaic sculpture of Athená, Acropolis Museum; bottom, Gandalf facing the Balrog in Peter Jackson’s Lord of the Rings.

Anyone who has read my writing, whether fiction or non-fiction, knows that I dislike genre ghettoes. I also think that well-run small presses are our best hope for publishing work that does not adhere to workshop recipes.

One such press is Hadley Rille Books, founded in 2005 by Eric Reynolds. Eric’s press publishes stories that straddle science fiction, archaeology and fantasy — three ingredients that mingle particularly well and can engender utterly absorbing stories.

To celebrate their fifth anniversary, Hadley Rille Books is launching a book sale drive from now till the end of the year. If you register at the site, you will be entered for the drawing of a Kindle 3G and will get any books you order at a discount and with free shipping.

I haven’t met Eric in person, but our e-mail exchanges made me realize that (contrary to common wisdom) a person can shoulder the herculean task of steering a small press and still be a thoroughly responsive and pleasant human being. Among Hadley Rille’s titles are the well-received Ruins series and the press has introduced several new authors to the world. I, for one, hope that such presses — and such editors — become the norm.

by Larry Klaes, space exploration enthusiast, science journalist

Part 1

Part 2

Part 3

How Might They Vanquish Us?

We have now looked at the most obvious motives (to us at least) for an alien species to want to crush humanity and found most of the feared concepts wanting.  Now it is time to explore the ways in which said alien marauders might take us out of the galactic picture.  Ironically, while the potential motives for invasion and destruction are often outright implausible, the methods available to a smart but aggressive species that might want us gone are often even more likely and effective than the usual imagined scenarios for the conquest of Earth.

If asked to visualize how an alien race might come after humanity, the scenario that seems to jump to most people’s minds is of giant spaceships hovering over major cities (Skyline is just the latest incarnation of that scenario), or a whole fleet of shiny silver spinning disks carrying  alien hordes wearing shiny silver spacesuits and gripping laser rifles in their clawlike hands.

Now while one cannot entirely rule out the possibility that one day Earth’s skies will be filled with large and dangerous alien vessels up to no good for us, the idea that more advanced beings would engage in a battle for Earth and against humanity in a manner similar to the scenarios described above seems about as efficient as targeting our world for its supply of water with all the much easier and more effective alternatives available.

If you want to get rid of humanity and don’t care if most of the flora and fauna inhabiting our globe also gets destroyed in the process just so long as the planet remains intact, all you need to do is attach some rockets to a collection of planetoids and aim them at Earth.  Humanity could be doing this with some of the smaller varieties of space rocks in just a few decades if we choose to, so a species that has actually made it to our Sol system via starship would be able to do the same.

Depending on the size and mass of the planetoid and where the ETI would target it, our civilization if not our very species could be rendered helpless in short order in a style reminiscent of the dinosaurs 65 million years ago.  Indeed, a number of small planetoids have recently come close to Earth.  Astronomers discovered them just a few days before their close encounters, leaving too little time to develop any countermeasures had they been on an intercept course.  And these objects were guided only by forces of nature!  A deliberate use of planetoids to smash us into submission or worse is a scenario that has been discussed and written about, but a real organized defense system is still decades away.

An even more frightening concept is to use a starship itself as a weapon.  A large vehicle moving at relativistic speeds, even a fraction of light speed, could hit Earth with more force than humanity’s entire nuclear arsenal at its peak in 1990 (55,000 nuclear bombs).  Such a weapon would be very hard to track and virtually impossible to stop with our present technology.

The details on this scenario, along with a very interesting discussion as to why an ETI might do such a thing to us and others (take out any potential aggressors/competition before it does the same thing, in essence) may be found on Winchell Chung’s fascinating Web site.

Keep in mind that while Chung does make some very compelling arguments, he is also a very big space war gamer.  Having a galaxy full of mature, peaceful, and altruistic beings may make for a nice place to live on a cosmic scale, but a rather dull RPG.  Going on the offensive with other species is also a pretty good guarantee that even an advanced ETI that gave up aggression and war ages ago may not like being threatened or seeing others in such a state and may take action against such a paranoid and self-serving race.

Another method for taking us out is one that has probably happened naturally across the Universe since the first stars came along:  Supernovae.  An exploding star would not only vaporize the members of its system but also spread deadly radiation for hundreds of light years around.  Earth has obviously survived having its native life forms become completely extinct by many stellar explosions over the last four billion years.  We can even thank a supernova for being here in the first place, as it was the violent death of an ancient star some five billion years ago that kick-started the cloud of dust and gas that became our Sol system, along with giving the elements needed for the evolution of life.

However, if an advanced species knew how to trigger and control a stellar detonation, they could fry our entire galactic neighborhood.  Other methods of sterilizing whole solar systems includes smacking two black holes together and directing galactic jets, which are streams of particles and radiation thrown out by massive black holes in the cores of some galaxies.  One hopes it won’t be possible to harness such energies, but who knows what beings that can survive and grow for eons in this Universe might be capable of?

Another cosmic weapon that fascinates and frightens is known as the Nicoll-Dyson Beam.  Dyson Shells are a fascinating concept in their own right:  Freeman Dyson envisioned a society taking apart its solar system and building a vast swarm of communities around its sun to collect as much energy from it as possible (right now 99% of Sol’s energy gets “wasted” into space).  From a distant vantage point, anyone monitoring such a system would see its star gradually dim in the optical realm and brighten in the infrared region of the electromagnetic spectrum.

Being able to collect and utilize so much energy from a sun has many benefits for an advanced technological society – and a few dangers for others as James Nicoll would later point out.  Dyson Shells would be able to focus and redirect the solar energy they collect into tight and powerful beams called a phased array laser.  The beams could easily destroy whole worlds many light years from the Dyson Shell.

Whether Dyson Shells actually exist and if their makers would use them as galactic-scale weapons is another matter, though there have been actual SETI programs which attempted to find these astroengineering projects.  This page from the Orion’s Arm web site gives an interesting visual and text description of this idea.

Is SETI Itself Dangerous?

There have been many who warn about sending greetings and other messages into the Milky Way and beyond.  The idea behind METI (Messaging Extraterrestrial Intelligences) is that since it may be hard for an alien species to find Earth and humanity among the 400 billion star systems of the Milky Way, we should increase the chances for detection by broadcasting into deep space towards what we think are favorable cosmic places for intelligent life.  The idea behind SETI is that alien beings are conducting their own METI programs, since that is probably the easiest way for humanity to detect another society in the galaxy at present.

The main and obvious issue with METI is that we do not know what other kinds of beings are out there.  Folks such as Carl Sagan have speculated that aggressive species tend to wipe themselves out before they can achieve space travel.  However, this has the flavor of painting an alien race with the traits and behaviors of our species.  What if there were species which cooperated as a unit and still decided that other beings must go before they become a threat to them?  Or what if they felt that other species, being viewed as inferior, were in need of a serious “makeover” that would effectively destroy whatever made the target species unique?

Some have speculated that an ETI might take out humanity and any other species at our stage of development by operating a METI program that carried what we might call an artificial virus.  The target species would pick up the alien “message” and in the process of decoding it would unleash a program that could do all sorts of dangerous and deadly things, from taking down our technology to giving us the plans for a superbomb that would detonate once we built it from the instructions given in the message.  Other potential scenarios involve converting humans into puppet slaves or replicating the alien species on Earth to take over and then aim more such messages at other potential worlds to continue the galactic conquest.

Of course it would seem easy to make sure that this never happens by simply keeping the alien message isolated or just never building the design plans.  However, the combined excitement of detecting an ETI signal and the often wild, vast, and intricate nature of the Internet could bring about the spreading of the virulent message and be released by those who feel it is their right to have and know such information.  In addition, as we see in the news on a regular basis, there are those groups of humans who might deliberately want to open up this cosmic Pandora’s Box to spread death and destruction across our planet for their own purposes.

This Web site goes into detail about the possibilities for an alien species to take out Earth without ever having to leave home either in person or even through a robot vessel:

Final Thoughts

This essay began thanks to Stephen Hawking’s well-publicized views on alien intelligences which he thought would not be a good thing for us to encounter any time soon.  While there is of course the possibility that we might encounter an alien species that is a threat, I was unsatisfied and disappointed with Hawking’s version of this scenario.  It struck me as not only being one-sided, limited, and old fashioned in thinking, but far too reminiscent of numerous recent Hollywood-style science fiction plots – an industry not exactly known for originality, deep thought or rigorous scientific accuracy.

Hawking’s take on alien life feeds into this negative, paranoid, and inward-looking attitude regarding the unknown that seems to be growing in human society these days.  While it is prudent that we do not just jump into the galaxy without at least having some idea who and what is out there, focusing on the idea that all alien beings are hostile monsters and that we should dismantle our radio telescopes and hide under our beds are not exactly the actions of a healthy, maturing society.  Besides, if an ETI were out to get us, remaining ignorant of the Universe and trying to be undetectable is not the way to go.

As I have pointed out in this essay, an advanced alien species would be able to destroy us in short order and we would have little recourse to stop them at present.  The fact that it has not happened may mean they simply haven’t found us yet, but it may also mean that we are either lacking in large numbers of intelligent galactic neighbors or that taking out another species that has barely gotten its feet wet in the cosmic ocean is not the way to behave as a galactic society.  We still have far more to worry about from members of our own species bringing down civilization than any hypothetical alien species.

Another thing I do know about human nature:  No matter how many warnings and precautions and even laws that get thrown up to control people when it comes to what society thinks is in its best interests, there will always be individuals and groups of people who defy these rules either because they disagree with them or because it is in their nature to go against the grain.

This will apply to voyaging into space as much as anything else.  The only reason it hasn’t happened already is due to the technological difficulties in making a deep space mission a reality.  However, once we establish a serious foothold in space in our Sol system, I know there will be groups that will not want to remain confined to our celestial neighborhood but will want to venture to those countless stars surrounding us.  This will keep happening for as long as humanity lasts.

This is the eventuality we must prepare for, because I will agree with Hawking on one thing:  If life’s evolution is similar everywhere, then it is likely that some other species will also share our drive and desire to see what it out there beyond their home world.  It may be only a matter of time before we are visited.  How we respond to them depends not only on their intentions but on how much we have learned and evolved when it comes to understanding the Universe as well.  Hopefully we will not let our fears turn a potential friend into an enemy.

Images: 1st, a meteor strike (Virgin Media); 2nd, a radiotelescope transmitting DNA to the galaxy (Jon Lomberg); 3rd, Jeriba Shigan (Louis Gossett, Jr.) and Willis Davidge (Dennis Quaid) in the film version of Barry Longyear’s novella Enemy Mine.

by Larry Klaes, space exploration enthusiast, science journalist

Athena’s note: Larry’s article is particularly timely, given the recent buzz about the Earth-type planet Gliese 581g.

Part 1

Part 2

For those who may still wonder and question just how much weight the words of the famous cosmologist Stephen Hawking hold for the concept of alien intelligences and their potential reactions to encountering humanity, consider this:  A new science fiction film coming out this November titled Skyline recently released its theatrical trailers.

One of the older Skyline trailers begins with the line:  “On August 28th, 2009, NASA sent a message into space farther than we ever thought possible… in an effort to reach extraterrestrial life.”

Now it is true that on that date a transmission was broadcast into deep space by a NASA-owned radio telescope located in Australia.  This collection of messages from people all over the world (sent as part of the Hello from Earth campaign) was aimed at a planet in the red dwarf star system of Gliese 581, which is only 20.3 light years, or 194 trillion kilometers from us.  That may seem like a long way to Earth-bound humanity, but on a celestial scale the Gliese 581 system is a near neighbor.  As of this writing, the transmission has traveled just over one light year.  That isn’t even far enough to reach our closest stellar neighbors, the Alpha Centauri system 4.3 light years away, let alone merit the title of the farthest-flung human message ever.

As a final point, we simply don’t know if life of any kind exists on or near the target of Hello from Earth, the fourth world circling the star Gliese 581.  However, astronomers now think at least one and possibly three planets in that system have the potential to possess liquid water, a major ingredient for the formation of at least terrestrial types of life.  Of course the transmission is not going to stop once it reaches that alien planet.  The messages will spread outward and onward into the galaxy at light speed, which will give them an increased chance of being detected some day by an ETI, assuming any exist in the signal path.

After this inauspicious beginning to the trailer, the viewer is treated to some apparently real news broadcasts about Hawking’s alien warnings interspersed with images of strange bluish-white meteor-like lights dropping down upon Los Angeles.  In the news segments, former CBS Television news anchor Dan Rather intones that “if extraterrestrials visit us, the outcome might be similar to when Columbus landed in America.  In other words, it didn’t turn out too well for Native Americans.”  The trailer caps off this dire warning with the text “Maybe we should have listened.”  And done what, I have to ask?  Cover Earth in black tarp with some stars painted on the outside and hope nobody notices us?

Too late.  The menacing spaceships of the alien Columbuses, looking like gothic metal sculptures, are bearing down on the places where the lights landed.  The name of the film flashes on the screen, then comes a close-up of one of the alien vessels hovering over LA.  Its underside open wide like the jaws of some immense beast, it’s pulling thousands of tiny screaming, tumbling humans up through the air and into itself for reasons yet unknown, but ones the audience has little trouble imagining may not be for the benefit of humanity.

A final text warning commands us “Don’t look up!”  The injunction is directly counter to everything our society has been taught in terms of social progress and evolutionary development – to say nothing of what the recently deceased astronomy popularizer Jack Horkheimer said at the end of every episode of his PBS program, Star Gazer, which was to “Keep Looking Up!”

More Than One Side to the Alien Encounter Debate

Aside from the near-certainty that Skyline will be little different or better than the majority of alien invasion stories of the last one hundred years, using the real words of a real scientist (and a cosmologist at that) to give a sense of weight and urgency to just one side of the concept of alien interaction with our species ultimately blurs and overshadows the wider range of possible outcomes for what may one day define the ultimate course of humanity among the stars.

While it is true that the primary overall purpose of Skyline is a material one – to line the pockets of its makers with money by appealing to the basic instincts of those who will provide said profits – the film (and Hawking) are nevertheless contributing to the debate on how we should deal with other intelligences in the Cosmos.  This is the case whether the filmmakers had any deep intentions of doing so or whether the idea is plausible.

Too many science fiction stories about aliens tend to focus on the negative aspects of encounters between different sentient species, thus biasing (and reflecting) public thought on this topic.  So it is both fitting and important to take a look at just how plausible dire predictions like Hawking’s truly are.  Of course, there are certain limits as to how much one can reasonably determine what an ETI may do in regards to humanity in its present state: not yet knowing for certain if there is any life beyond Earth tops the list here.  However, we do possess enough scientific and technological knowledge to make some plausible determinations on just how likely our greatest fears about our galactic neighbors might be.

Just as SETI requires its hypothetical subjects to share some common elements with humanity in order to work, any beings who wish to harm us must also think and behave somewhat like us.  So when examining types of invading aliens, I am excluding the ones with abilities we would consider to be godlike: able to appear at will anywhere or anytime and commanding so much knowledge and power as to make the act of rendering us extinct a quick and easy exercise.  I presume that if such superbeings wanted us gone, it would have happened by now.

The fact that this has not happened could mean a number of things: they are much too smart and nice to harm others; they don’t care about us one way or the other; or they will destroy us but just haven’t gotten around to it yet.  So I will not speculate further on superETI, except to warn that beings able to do just about anything blur the line between science and fantasy.  In addition, I make no pretense that my lists of alien motives and weaponry are in any way complete, so further ideas are welcome.

The Why of Alien Invaders

Since invading another world across interstellar distances requires serious time and resources, our hypothetical alien marauders will not attempt to take down humanity and its home planet on a whim or to follow some cliché of galactic hegemony.  Like the future humans in the 2009 film Avatar who travelled 42 trillion kilometers to reach the Alpha Centauri system moon Pandora for its mineral wealth to aid their ailing civilization, our invaders will have to come up with a compelling reason to travel all that way if they ever literally want to leave the ground.

Of all the “whys” for an alien assault on Earth, taking our planet as a new place to live and utilize because their homeworld is dying or destroyed for one reason or another, is at least as old as H. G. Wells’ The War of the Worlds.

Well’s 1898 novel was a reflection on how European colonizers of the era were treating the people and places they were colonizing and an extrapolation of the idea of advanced beings responding to the slow but inevitable demise of the habitability of their home planet, in this case Mars.  The numerous astronomical reports of seemingly straight lines on the Red Planet since 1877 had led to speculation that they were artificial.

The wealthy American astronomer Percival Lowell championed the idea that the lines were actually immense canals built by the Martians to bring water from the icy white polar caps to quench their drying, dying cities.  While Lowell seems to have assumed the superior Martians would eventually accept the end of their species and become extinct with dignity, Wells imagined these same creatures not wanting to go down with their planetary ship, thus their invasion of Earth.

Of course, one advantage Wells’ Martians had over just about any other species in the Milky Way galaxy was living so relatively near to our world.  A conventional rocket can propel a spacecraft to Mars in a matter of months, as they have in reality since the early 1960s.  However, it is an entirely different matter to send a ship between even the nearest stars.  Unlike the vessels of science fiction which are equipped with fanciful warp and hyper drives or have a convenient cosmic wormhole nearby, our current knowledge of what it would take to get from one star system to another is fraught with technological and celestial hurdles that make even a slow multigenerational ship a daunting task.

So even if an alien planet was going down the drain ecologically, geologically or cosmically, would it be wise (to say nothing of practical) to send a fleet across interstellar space to take over another star system?  Unless their sun was turning into a red giant or going supernova, it would be far easier to utilize the worlds in their own solar system for resources and settling.  For example, if an alien society was in desperate need of water like Lowell’s and Wells’ Martians, it would be much cheaper to mine the many, many comets that we know circle other stars, just as they do at the fringes of our Sol system.  And while we have yet to detect any exomoons, we do know that most of the moons circling the four Jovian planets are covered in water ice and some, like Jupiter’s Europa, probably have deep global water oceans.

The same goes for mineral resources.  The Milky Way galaxy alone is estimated to contain many billions of solar systems.  Presumably they have lots of planetoids and comets in addition to their major worlds, just like our celestial neighborhood.  It is also probable that many of those worlds are uninhabited but rich in elements that a technological civilization would find useful.  So even if our marauding aliens do want to journey all the way across the galaxy for gold or oil or whatever, why focus on Earth and its environs when the pickings are so easy and plentiful elsewhere?   Hauling all those rocks home would be expensive as all get out.  So trying to colonize a solar system that already has one intelligent species, even if that species is just starting to explore and utilize space, might be more trouble than it is worth.

Now let’s look at another classic reason for an ETI to want to come to Earth:  Dinner.  It has become practically an old joke that some aliens would see all the teeming life forms covering our planet and consider us an open buffet.  Not only do we once again invoke the question of whether it would be worth going to all that time and expense for a meal when there are probably much closer snacks at home; it is also virtually certain that our biochemistries would be so different that Earth organisms would be poison or cardboard to an alien creature (and vice versa).  The vastly different genetics would also prevent interspecies breeding, especially since it is unlikely that we and they will look anything alike.  As for needing a race of slaves, robots would be much less expensive and far more efficient.  Mission Serving Man sounds like some very old and very low-grade science fiction.

If it is just too much to fly all the way here for rocks or a meal, are there any other reasons why an ETI might still want to exterminate us?  We may not be a threat *now*, but perhaps there might be others who could see us as future cosmic competitors for available places and resources.  If the galaxy has beings who think in very long terms, certainly much longer than most present humans do, they may not want to wait until our descendants are arriving at their doorsteps and may want to take us out now instead.

I for one would like to think and hope that a stellar island of 400 billion suns over 100,000 light years across with perhaps 100 billion galaxies beyond our Milky Way in a Universe 13.7 billion light years wide would be plenty for everyone.  However, perhaps some cosmic real estate is more choice than others and its finite nature makes it a valuable target worth fighting for.  One estimate I saw in a Scientific American article from 2000 said the galaxy could be conceivably colonized in just 3 million years – a very short time compared to the 10 billion year age of the Milky Way.  The fact that our planet appears to be free of any alien conquerors/settlers may say something about that idea, or perhaps conquest and colonization is not as popular as we might imagine (and often do).

Even if we and others decide to be planetary homebodies for many generations, there will come a day when a home system’s main source of light and heat, their sun, will begin to die out.  Our yellow sun is no exception:  Sol is expected to start making things pretty unbearable on Earth in just a few billion years as it begins to expand into a red giant.  Even if Earth is spared being swallowed up by this bloated monstrosity of hot gasses, our planet will be charred into molten slag, killing anything living that remains.  Earth will later turn into a frozen iceball as Sol shrinks into a white dwarf and eventually a dead, dark cinder.  Even if our planet survives all this in at least its physical presence, when Sol goes completely so will Earth, its icy battered carcass floating off into the depths of the Milky Way as a rogue world.

So while we do have several billion years to prepare for this event, eventually nature will force our hand and make us choose either flight or extinction.  Even staying in distant parts of our system will become impossible once Sol starts collapsing upon itself.  And this is the fate of every star some day, even the very long lived red dwarfs, though some suns will also turn supernova or collapse into neutron stars or black holes.  I know things will be very different in those distant epochs, but anything beyond briefly visiting Earth or anyplace else nearby in those eras seems infeasible at best and deadly at worst.

Have other species around other suns realized this about their celestial hearths as well?  Will they decide to stay at home and wait for the end, or will they pack up and look for worlds where their suns won’t be going out quite so soon?  Will the fact that we have at least a few billion more years of relative safety be appealing to such refugees?  What happens when it is our species’ turn?  Perhaps there are many vague and hidden factors that will render all this speculation and prediction moot, but at least this idea has the merit of being a plausible reason why one might take up interstellar voyaging.

Another reason ETI might want to come to Earth is religion.  Perhaps like certain segments of humanity there are alien beings who strongly believe it is their sacred duty to share the Good News with everyone else, whether they want it or not.  Will alien missionaries ply the stars seeking to convert other species to what they perceive as The Truth, perhaps affecting “heathens” in the same way that missionaries affected other cultures in their zeal to save souls – settling in some very nice real estate in the process.  What will happen when a human group and an alien collective of very intense and very certain religious missionaries encounter each other?  Or is religion a primarily human concept?  Well, so far we have not been forced to worship any strange alien deities by clergy from the stars, unless some of our current religions were the direct result of an ancient missionary visit.

Images: 1st, the obligatory destruction of the White House by aliens, here in Independence Day; 2nd, alien appetites shown on Mars Attacks trading cards (Gelman, Brown and Saunders); 3rd, a bored godlike alien as embodied by Star Trek’s Q (John de Lancie); 4th, squabbles over choice real estate in Spielberg’s remake of War of the Worlds; 5th, A Case of Conscience by James Blish, an early SFnal example of planetary missionary fervor.

Part 3