01 Apr 2004 Justin B Rye


Welcome to an elementary course in Theoretical Cryptoastronomy, the study of imaginary things from outer space.  The syllabus consists of five modules:

Evaluation will be based partly (∼7 %) on secret observation by intellects vast and cool and unsympathetic, partly (∼12 %) on direct use of the Probe, and partly (∼98 %) on guesstimates derived from arbitrary assumptions.

I'm at a loss for an explanation of quite why I should have written this, apart from the obvious fact that it's yet another foray into the world of quasiscience cliché‐mockery.  It lets me add a few more site‐internal links, recycle offcuts from my guides to SF Chronophysics, Xenolinguistics, or Exobiology, and put on display the routines I've got bored with rehearsing in arguments.

Guide to Fermi's Paradox

The big mystery in SETI (the search for extra‐terrestrial intelligence) is why we should have to search for it at all.  There's nothing obviously special about Earth; starsystems much like ours have been around for billions and billions of years.  So shouldn't outer space be crawling with lifebearing planets, technologically advanced aliens, and unmistakable evidence of inhabitation?  Shouldn't somebody already have come looking for us?  As the Italian physicist Enrico Fermi put it, “Where is everybody?”

Naturally, it's only a paradox if we're right to imagine that the ETs are out there.  Somewhere in our chain of assumptions there's got to be a misstep – a Great Filter that's winnowing our imagined multitude of space‐opera galactic empires down to approximately zero.  But where is it?  Let's run through the options:

  1. Maybe planetary systems are rare.  This idea used to seem highly plausible; but astronomers have discovered an awful lot of stuff going around nearby stars lately, so it's out of fashion.  Mind you, it's all seriously weird stuff, so perhaps what they're detecting is the junk that's messed up all the potential biospheres.  Well, at least it improves the likelihood of extra‐solar planets having interesting things in their skies to stand in for the absurd fire‐balloon nightlights the SCI‑FI Channel has been promising us… people don't appreciate what a great light‐show Luna puts on, compared to, say, Phobos and Deimos!
  2. Maybe life doesn't appear very often.  Somehow it's taboo to mention that possibility at all these days – dead Martian sands don't sell newspapers or attract research grants.  However, even if life isn't so common that we can afford to wreck Earth and move next door, it still might be common enough that anyone prepared to spend a few centuries freeze‐dried in transit could expect to get someplace where the air's only a slow poison.  That would mean a galaxy teeming with potential ETI… but we really have no idea what the odds are.
  3. Maybe it's rare for intelligence to evolve.  That is, perhaps the microbes in most alien seas come up with some obvious alternative to being multicellular that outcompetes all opposition and stops any interesting “higher” fauna ever developing.  Or perhaps the biochemistry of Earthly vertebrates is unusual and all the comparable creatures elsewhere find the warm‐blooded big‐brained lifestyle unprofitable.  I'd be mildly surprised if this was true – life on Earth made it all look so easy, beating the deadline with aeons to spare – but again, without a good statistically significant sample of laboratory planets, who's to say?
  4. Maybe intelligence rarely leads to sufficiently high technology.  Now, it's easy to dream up doomsday scenarios in which With a Tragic Irony the ETs are Destroyed by Their Own Creations as soon as they invent nukes (or fire, or VR Tetris, or warpdrive)… but it's hard to imagine every single sapient race messing things up so badly no replacement civilisation ever arises.  Once you're thinking on a galactic scale, it hardly matters if they do suffer a Dark Age or two, or get stalled in the palaeolithic – they can keep ringing the genetic and memetic changes for millions of years, and if the cultural snowball ever gets rolling then science and technology are pretty much downhill all the way.  They may not come up with the same problem‐solving techniques in the same order, but as long as they keep finding new problems they'll have to keep building on the toolkit they've got.
  5. Maybe the technologically advanced societies aren't interested in exploring.  This one again sounds strained: we're the only race ever to evolve that isn't autistic?  Sure, they might not be conquistadors dedicated to settling every available rock, but that's fine.  We can already imagine ways of using foreseeable technologies to get probes to every last corner of the galaxy within a mere couple of million years; if the average alien isn't interested enough to insist on going there in the flesh, and waits until the task's trivial before bothering to start designing automated probes, then if anything that's likely to mean an obviously intelligence‐filled universe sooner rather than later.  After you've launched a self‐replicating interstellar explorer AI, it doesn't matter what happens to you – your culture will come into contact with ours sooner or later.
  6. Maybe the galactic explorers have indeed found us, and have been watching us for millions if not billions of years, but they're hiding, like traditional little green men.  The problem with this idea (apart from its sheer tinfoil‐hattiness) is that the fewer inhabited worlds there are, the more talking to us becomes a rare and valuable opportunity; and on the other hand the more there are, the more races have to independently come up with a reason for abiding by a strict ultra‐long‐term policy of pretending not to be there.

So; there's no good obvious candidate for the Great Filter.  For such a tenuous piece of reasoning from so little hard evidence, this has surprisingly big and unwelcome implications, since we know the filter's somewhere, and it might be somewhere that's bad news.  Real evidence of life on Mars or Europa becomes something we should be hoping never to find!  After all, the weaker candidate #2 is, the more danger it puts at position #4 where it might be about to filter us.  We're left having to consider possibilities like strong nanotech being a universally lethal thing to research…

A BDO‐Spotter's Handbook

It's conceivable that a super‐advanced space‐travelling civilisation used to be out there, but – oh, bad luck – we just missed them!  In which case they might have left some fun pieces of industrial palaeontology lying around waiting for us to find and investigate them.  And I don't mean crumbling ancient cities or drifting space‐hulks – I mean truly vast pieces of machinery.

People who are trying to be serious about this kind of stuff usually call them “megastructures”.  Unfortunately, architects have started using that term to refer to mere office blocks; and on the whole rather than retreat up the SI prefix table to “gigastructures”, I prefer going straight for the SF‐fannish jargon term: they're “Big Dumb Objects”.

Solar Power
Perhaps the most famous kind of BDO (so mainstream it has even been in Star Trek!) is a shell built around a star to collect all of its output for the owners' use – the “Dyson Sphere”, a concept invented by the Dyson who didn't invent bagless vacuum‐cleaners.  Oh, and when I say “sphere”, I'm not necessarily talking about a solid sheet of ironmongery englobing the sun like some humongous work of Victorian engineering, though admittedly that is how it's usually depicted.  The more reasonable approach is to arrange swarms of energy‐gathering satellites in carefully calculated orbits.
Mind you, if you want to squeeze all the power out of a star efficiently, this approach may be a good start, but it seems a bit half‐hearted!  I'd have thought what you want to do is throw an electromagnetic bottle round the star then decant all that plasma into a couple of zillion frozen‐hydrogen comets.  That way you can power your village streetlights off nuclear fusion for the rest of time, or alternatively charge up a single planet‐sized antimatter firecracker then light the blue touchpaper and retire immediately.
Meanwhile, one other use for circumstellar constructions of this sort is as an unusually literal “stardrive” – the “Shkadov Thruster”, which converts your entire starsystem into a self‐propelled solar‐sail vessel!
Death Stars
Given the improbability of encountering aliens whose technological level is within millennia of your own, the only point of commissioning astro‐dreadnoughts is so you can threaten others of your own race – and you don't need a stardrive to do that.  This calls for an alternative funding model involving some natural hazard that can only be defended against by huge space‐based missile‐silos; but remember that you need to take into account not only the theoretical risk per century of (e.g.) an asteroid hitting your planet but also the risk of a loon getting hold of the button.
Experimental killing‐machines are also a bad place to test new software designs… and if you find one floating dormant in an apparently lifeless region of space, don't even think about it.
Living Space
Designs for residential megastructures can be classified by where they get their gravity:
  • Spinning hoops, where centrifugal force lets you live on the inner surface (this includes both rings/orbitals and the ever‐unpopular “cosmic macaroni” design; the big ones require unlikely building materials).
  • Supramundanes, which are strips or shells suspended in a gravity‐well (such as a gas giant's), so you can live on the outside – a sort of round‐the‐world suspension bridge.
  • Habitats built with artificially generated gravity, which can thus be any shape you fancy (the inside of a Dyson Sphere, for instance).  One option if you can't manage anything better is the pie‐dish‐shaped starship, which has a “down” while you're accelerating.
  • Things are simpler if you aren't fussy about gravity – especially if you can live without air or radiation shielding, because then space makes a fine open‐plan residence, and even turning your homeworld into an asteroid belt can seem like an improvement.  After all, what good is a nickel‐iron core if you can't get at it?
But who needs a habitat that big?  People inhumanly bad at arranging their furniture?  Or maybe just incredibly incompetent when it comes to contraception?  The idea of assembling a Ringworld for the sake of Lebensraum sets off warning bells for me.  I can't help imagining a trillion‐odd workers labouring on it for generations while sleeping in shanty‐town orbital‐habitats… then being told when it's finished that they can't afford the rates and that they should be grateful the owner isn't going to demolish the slums.
Celestial Mechanics
I dare say the aliens might need a gigahabitat because they have religious objections to birth control (cue visions in which the BVM orders a BDO)… or maybe they're sun‐worshippers who want to protect the sacred photons from falling into infidel retinas.  Once you start wondering about this kind of thing there's no obvious limit to how strange it might get, and it's particularly liable to result in baffling “neutronium‐henge” artefacts.
Radio Star
For those too lazy to go exploring, how about the option of setting up a big here‐I‐am signal and waiting for ETI to come to you?  It could be a plain electromagnetic beacon (in which case the leftover emission wavefront counts as a sort of a relic), but it's a bizarre sort of laziness unless you're getting some functional advantage from your BDO –
  • The Lighthouse: if you're convinced there are slightly myopic aliens out there, maybe a focussed beam's what you need.
  • The Transducer: how about a Dyson shell that converts a star's output into exotic particles… tachyonic ones would be good for getting quick replies.
  • The Magnet: maybe a sufficiently large vortex in hyperspace will make your system a natural target for explorers.
Of course, it's possible for message‐sending activity to be less innocent than it seems, but any race that goes opening mystery attachments under Windows deserves everything it gets.
Big Science
Another possible case for huge engineering projects is where the physics of it establishes a minimum size – a subparticle super­dupercollider, “Tipler Cylinder” time machine, or Q‑wave lens.  Experimental equipment tends to have an inherently limited lifespan, but in principle your whole social infrastructure could end up dependent on some such obscure piece of physics; maybe the giant Quantum Interocitor is necessary to keep your communal brain‐the‐size‐of‐a‐planet topped up with fresh supplies of computronium.
Gardener's World
Refurbishing planets to enhance their ability to sustain life isn't usually seen as megastructure engineering unless you've built the whole thing, lithosphere, fjords, and all.  Well, you never know – it's possible your efforts might go unnoticed by later visitors, especially if the place has been ecoformed to suit ammonia‐drinkers rather than terraformed.  However, some of the suggested techniques are unsubtle enough to deserve mention here, such as ringing Mars with mirrors, disassembling Venus's planetary mantle, or igniting Jupiter.
Then again there's the kind of refurbishing you can do to your original home.  Girdle the equator with a string of space‐elevator towers connecting to the orbital ring‐city factories… illuminate the night sky, using the magnetosphere as a billboard… the end result could be a planet paved with Soviet‐grade concrete, so it would be nice to imagine we'd have the sense to target our terraforming efforts on Earth and save the industrial lunaforming for Mars!

Starship Combat Top Tips

There are two possible approaches to planning for interplanetary or interstellar battles.  If what's important to you is efficient and well engineered astronautics, read the recommendations in the left‐hand column.  If you prefer something that's going to provide good footage in the media, read the right‐hand column, and don't forget to arrange the schedule of Internet trailers, main release, and associated games/action‐figures to fit your reelection campaign.

While you aren't accelerating, point your nose towards safety and your drive‐tubes towards danger.  This not only saves time in emergencies but presents any potential attacker with the prospect of a reaction‐drive going off in their face. Keep your nose pointed in the direction of travel.  Where possible, use a stardrive that enforces cinematic kinematics, such as a stutter‐teleporter: you aren't accelerating, you're just being continuously relocated in front of where you were.
Projectile and coherent‐radiation weapons work perfectly well at long ranges; there's no excuse for star‐destroyers colliding with one another when they have the whole of space to manoeuvre in.  If you can see one another, you're too close. Make sure your fights are dramatic by only engaging the enemy while parked at a strategic location (such as a wormhole exit), and/or only using blasters with inverse‐cube‐law range limits.  Never miss an opportunity to call for “ramming speed”.
Organic lifeforms make good mascots but bad pilots.  When the enemy's deploying clouds of war‐drones, each accelerating on its own vector in its own relativistic frame of reference, primate tree‐swinging instincts just won't cut it. Embedded‐software journalists are one thing, but never put an AI in charge of your Ultimate Weapon.  Get Star‐Captain Biggles to centre the cross‐hairs by hand – his brain may be made of meat, but he's far more photogenic.
If you don't want to run the risk of your orbit decaying, standard operating procedure should be to use a “forced” orbit at higher than escape velocity, so that if you stop actively maintaining it you drift away from the planet. Given that your stardrives provide cheap hyper‐acceleration and you're not planning on hanging around for long, gravity‐wells are relevant mainly for the associated scenery.  Remember to park side‐on to the planet so your starboard portholes get a good view.
There's no such thing as a survivable impact.  You get enough lethality to spare from any contact that doesn't involve deliberate velocity matching; there's little point using fancy gimmick missiles if they're going to hit the enemy head on at Einsteinian velocities. An armoured hull will save you from drifting space‐grit, but to fly through the Peasoup Nebula on ultradrive you need a serious tachyon‐snowplough – and since that has to be magic in the first place, you might as well go for the whole “divert power to shields!” shtick.
Never look directly at an enemy starship – if it explodes it'll be a silent (and slightly delayed) point‐source blast as their antimatter cells lose containment, and if not you're staring up the barrel of their laser cannons!  Either way, ophthalmologically inadvisable. To make beam‐weapons visible in a vacuum, you'll need side‐scatter; maybe some sort of laser‐launched plasma‐bolt?  With luck it'll also produce static‐roar sound effects on your comms channels… as will your manoeuvring thrusters.  But what you really want is Cherenkov radiation “vapour‐trails”.
Unless you've got some appropriate “jumpdrive”, you can only ambush a victim in the emptiness of space by outrunning their sensors – for instance, radar's no good against photonic torpedoes. Nobody to fight?  Hunt Space Pirates!  Not only are they naturally exciting, they're also guaranteed to remain a lurking menace to civilisation for as long as you need them!
Asteroid belts are negligibly hazardous compared to the junk‐strewn space around your homeworld; even deliberately scattering “mines” is a waste of effort unless they're armed and mobile in their own right. Space badly needs chunky bits.  Hang around in ring‐systems as much as possible, and always fly through a planetary system in the plane of the ecliptic (banking dramatically as you steer) with all your hull‐mounted lights blazing.
Any strategy that involves blockading a frontier in space (let alone hyperspace) against intruders is doomed.  Indeed, why would you have territorial borders when the Rigellians aren't interested in Earthlike planets? The best thing about sweeping fleet manoeuvres in three or more dimensions is that you can usually find a map display angle that makes it look as if you outflanked them while they were trying to run away rather than vice versa.
The one thing you need before you can conquer an Earthlike world is atmospheric supremacy.  As soon as your military nano‐robots have 0wn3d the inhabitants' brains, you can recruit any infantry you need from the local populace. Space Marines are cool.  The name's a bit dumb, given that “marine” is the one thing they aren't, but hell, give them space‐axes and call them Special Ninja Assault Squad, what does it matter as long as they're blowing things up!

Space Invaders Howto

I hear of more and more alien invaders these days who seem to set out with no clear idea of what they want or how they should go about getting it, and who unsurprisingly end up bungling the whole operation.  It's dreadfully upsetting to see Greys bawling their eyes out, so here's a guide to best practice classified by objective.

Quite a lot of aliens go about turning worlds to rubble, with a variety of motives.  The Vogons were fibbing about that whole hyperspatial bypass thing, but the Daleks' old obsession with stealing Earth's core makes some kind of sense, it being after all a nice magnetically active one.  Or you might be the kind of people who really like asteroids (cf. above).
Planeticide is an expensive feat of demolition, with energy requirements on the order of 10³² joules; but if you can create space–time wormholes, a simple shortcut between the planet and its star should take care of it very effectively.
Having the permanent annihilation of all life on Earth as your primary objective is pretty hard to justify, unless maybe carbon‐based organisms lower local property values.
I recommend prolonged antimatter bombardment – there are some tough microorganisms in that bedrock.  Alternatively, use nanotech… but make sure it's pointed in the right direction.
Well, if a policy of exterminating intelligent aliens on the off chance that otherwise they might someday decide to do the same to you is sane enough for Heinlein, I'm sure it's sane enough for bug‐eyed monsters.
A light‐to‐moderate bombardment with kinetic‐energy weapons from translunar range should do it; the more flexible you're prepared to be about follow‐up strikes on survivors, the more of the local ecosystem you can afford to leave standing.  Or you can go for biotechnological subtlety and just beef up the common cold with a few traits from Ebola and rabies – don't worry, you can't catch it any more than a shark can get leaf blight.  (Or, use nanotech.  In fact you might as well tack that alternative on the end of each of these entries – nanotech's boring that way.)
For interplanetary imperialism to make sense habitable worlds have to be extremely rare, and world‐to‐world travel has to be extremely easy.  If you were planning to invade by a slower‐than‐light voyage in multi‐generation starships, then don't bother attacking when you arrive – now you've got the hang of living without a planet it's easier to build more of the starships instead.
But assuming you still want to do it, you might as well use the same approach as for genocide.  Or ecosphericide… you'd be redecorating the place anyway.
Coming to Earth to steal our water (à la “V”) makes about as much sense as breaking into a bank to steal the floorboards.  The thing you're after has to be something unsynthesisably biological or you'd be better off setting up your tritium mines, hydrocarbon refineries, or whatever in some uninhabited corner of space.
Whatever it is, persuade the local yokels to grow it as a cash crop.  For example, if all‐natural organic free‐range babies are the perfect ingredient for tentacle lotion, point out to each bunch that after all, they can use foreign infants!
Inhabited planets are the last place you'd go for fuel resources, let alone raw energy (try the big glowing thing in the sky instead).  Still, it's imaginable there's some special power‐source like Atlantean Orgone Crystals or Cheddite Unleaded that's only available locally.  Hokey, but imaginable.
Proceed as above; but be prepared for disappointment.  For instance, the bio‐electricity generated by a baby's nervous system is nothing compared to the power‐bill for its life‐support.  They're a net drain on your resources – throw them straight into your furnaces.
Interspecies trade (as opposed to grabbing anything you fancy in exchange for a few shiny trinkets) is tricky when one side holds the title deeds to a planet and the other has staked out the remainder of the observable cosmos, but if several different Ferengi corporations are racing you to buy up local virtual‐tourism rights then it becomes worth the effort of ripping them off.
Hrmm, playing the futures market must be much easier when you can warp space–time…
What, so you've developed interstellar invasion technology, but you're so ungifted at robotics that you need manual labourers, and so bad at coming up with weaselly employment contracts that keeping slaves is actually cheaper?  In that case you're probably better off sticking to the drudge work yourself and getting human management consultants to be the masters.
But whatever the exact job description, there are billions of potential applicants; just call for volunteers – you'd be surprised how many will step forward to welcome their new clueless overlords.
If you're so desperately insecure that you constantly feel the need to force others to acknowledge their inferiority, then once you've finished taunting your goldfish you might want to invade some planet full of balding primates.  Just a suggestion, your awesomeness.
Fake up a full Hollywood‐style invasion (complete with raygun‐toting mock‐aliens), and/or induction into the Interstellar League of Tribal Chiefdoms.
Invading a mudball like Earth would be insane, obviously – it's got no resources worth seizing.  But that's just the sort of crazy thing your rivals in the Great War would do, so you're obliged to invade anywhere that's tactically significant before they do!
There's no need to hurt the locals, though.  Give them all invulnerable cyborg bodies and they can even help out with token bits of unskilled labour in your war‐machines' maintenance pits.  They'll thank you later, once you've pumped the appropriate neurochemicals into their brains.
Any new society assimilated into the galactic melting‐pot brings uniquely valuable novel insights and perspectives, apparently.  So try to catch them before they start homogenising into one big global village; then once you've harvested their ethnic diversity you might as well “plough them back in” so as to get the next crop of novelties out of the planet's successor culture ASAP.
The easiest way of making civilisations implode is probably for the ambassador to tell them their religions are literally true.
Something like the above can also apply to the planet's evolutionary resources – “ooh, woodpeckers, that's a neat trick” (or indeed, “ooh, Bacillus pallidus, that's a neat trick”).  You've arrived a little late to collect groundsloths and dodo‐pox, though, so you'll probably want to do some weeding.
Nukes might seem perfect for this job, but don't overdo the radioactivity: you're adaptation‐farming, not mutation‐farming.
Dining on the biochemically alien fruit of another evolutionary tree is only likely to do you any good if what you're after is a particularly foul‐tasting slimming aid.  But maybe you're visiting Earth because you're fond of cats; in which case your advanced cat‐scanning technology might have told you what they really dream about eating.
Proceed as for baby oil.  Cookbooks available.
Er… you do realise this just isn't going to work out, right?
Try asking Google.

The End

While “researching” all this I've run into several pages advocating a position that seems dafter the more often I see it – the idea that humanity should throw all its energies into filling the Milky Way with self‐sustaining colony‐worlds so as to reduce the risk of extinction when Sol goes red giant in five billion or so AD.  Here's an alternative proposal: we round up all the gung‐ho idiots so keen on exhausting our planet's resources and fire them out of a catapult in the general direction of Alpha Centauri.  That's a much better way of safeguarding our survival.

Besides, why should we care whether the cosmos will ever run out of hominids?  It's not as if our evolutionary descendants at that distance would be recognisably human!  And while the development of true “artificial intelligence” is a way off yet, on a geological timescale it's the AIs we should be thinking of as our descendants, not their pet monkeys.  As long as we avoid doing anything irresponsible in the short term, we can expect the long‐term survival of our intellectual offspring to take care of itself.

So by all means let's have manned bases anywhere we have business doing things that can't be automated; it might even make sense to terraform Mars, eventually.  But there's no need to dress up squalid factional land‐grabs as some sort of grand cosmic destiny.  Exporting concepts like political boundaries, territorial conquests, and military arms races into space sounds like a good way of ending up fighting wars of independence against our colonies – and Mutual Assured Destruction won't help anybody's survival chances.