We all love a good space war right?
From the final battle in the film ‘Serenity’ to the climatic Battle of Endor in the last Star Wars’ movie, the sight of hundreds of advanced starships engaged in an almighty interstellar ruckus is enough to turn the head of even the least nerdy layperson.
Now of course even someone with next to no scientific knowledge should be able to point out some of the glaring technical flaws in these battles. Why does the Millennium Falcon bank when it turns? How do laser blasts appear to visibly move like bullets? Why is the bridge of the Enterprise perched so precariously on the top of the ship’s dome, rather than buried deeper in the vessel?
Now yes, yes, I am aware that Star Wars and most other sci-fi franchises are meant to be heroic, adventurous tales where scientific accuracy takes a back-seat to the needs of the plot, and that’s perfectly alright. But today I’d like to try and set the record straight, or at least a little straighter, and outline some of the more important elements of space warfare that contemporary sci-fi tends to ignore.
10. Battles will be fought at long ranges
This one should be pretty obvious. As cool as it is to have giant dreadnoughts blasting away at each other at point-blank range, its hard to envisage circumstances in which this would actually happen. Throughout human history battles have gradually been fought at longer and longer ranges. We’ve gone from hand-to-hand combat with clubs and swords, to longbows and catapults with ranges measured in the hundreds of yards, then to muskets and cannons, then modern artillery that could lob shells several kilometers, and finally to modern aircraft and missiles capable of crossing entire continents.
In space this trend can only continue. Mass drivers, particle beams and missiles should be capable of hitting targets many thousands of kilometers away. Powerful lasers might have the longest range of all, potentially capable of zapping targets hundreds of thousands or even millions of K’s away. Its not hard to imagine missiles being launched from platforms in Earth-orbit to hit targets on Mars. Why get any closer to the enemy that you have to?
This also applies to possible fleet formations. Placing your spacecraft within a few kilometers of each other is suicidal in space combat. Ultimately you want your ships close enough to effectively command, but light speed moves quickly enough (300,000 km/s) that this only imposes a very high upper limit. If any of your ships are close enough, for instance, that two could be taken out in a single nuclear blast, then they’re way too close. Also consider what happens if one of your ships does blow up. The resulting cloud of debris will expand in a rapidly growing sphere that will badly dent the hulls of any other ships nearby. It would seem that an absolute minimum on the placement of your major warships in a combat situation is a few hundred K’s apart.
There are countless example of sci-fi getting this wrong. A particularly egregious one is near the end of the film ‘Serenity’. The heroes covertly fly their ship into the middle on an enormous fleet of swarming reaver vessels in an attempt to shoot at one and then lure the whole fleet behind them to try and get around an alliance blockade.
Their successful use of this tactic begs the question, why doesn’t someone else just drift a nuclear bomb into the middle of the enemy fleet and detonate it? The lack of nuclear weapons is very common in sci-fi, notably in Star Wars and Star Trek, where they would be very handy on a number of occasions. In many sci-fi series any major fleet battles that do occur are obviously inspired by battles in our own history, especially naval battles, most particularly WW2-era carrier engagements. The Battle of Endor draws on tactical situations found in a number of famous naval battles. The way that fighters are used, to dogfight one another and strafe capital ships, is drawn quite directly from carrier engagements like the Battle of Midway.
However, there are some sci-fi novels that actually get this right. Alastair Reynolds excellent ‘Revelation Space’ series depicts many of the realities of space warfare very well. In the book ‘Redemption Ark’ there’s a scene involving a line of warships entering a battle each spaced ‘about a million miles apart’.
9. Wars will probably take longer
The longest conflicts in human history have lasted maybe a few generations. The medieval ‘Hundred Years War’ between England and France lasted on and off between 1337 and 1453 (116 years), the Punic Wars between the early Roman Republic and the Carthaginian Empire lasted on and off between 264 and 146 BC (118 years, 46 of which saw active fighting) while the Cold War lasted from roughly 1945-1991 (46 years). Quite possibly the longest example is the series of wars (about thirteen in total) fought between the Russian and Ottoman Empires between 1568 and 1918. These lasted 350 years in total, occurring about once a generation until both empires collapsed during the First World War.
Interstellar warfare however, could put all these brief little spats to shame. Fleets travelling between star systems will (lets presume) be limited to travelling slower than the speed of light. It would take over four years just to reach Alpha Centauri, the nearest star system to our own, though likely even longer considering that even if you could accelerate the whole time at a very impressive 1G it would take you about a year just to approach light speed, and then another year to slow down.
At the moment the closest star system to Earth that may contain a habitable planet is Gliese 832, which is 16 lights years away. Even if the war was easily won in a Gulf War-style blitzkrieg, it would have to last at least that long. But what if the first warfleet Earth sent wasn’t successful? It would take us at least 16 more years to find out, and in that time the inhabitants of Gliese could have launched their own invasion back at us. But say we then repelled that fleet, and sent out a second one of our own? We’ve already looking at a war lasting fifty odd years, and that’s against a relatively close star system. The Galactic Core is at least 25,000 light years away, and the entire galaxy 100,000 light years across. Its easy to envision far-future wars lasting thousands or even millions of years. On the scale of galaxies, war is a geological process.
A notable work of science-fiction that gets this right (its basically the cornerstone of the book in fact) is ‘The Forever War’ by Joe Haldeman. While FTL travel is actually possible in the book, relativistic effects still occur and deployments to distant star systems nominally lasting just a few years coincide with decades or even centuries passing back on Earth. The novel deals with the psychological trauma suffered by soldiers who return home from the battlefront to find a society generations changed from when they left it. Overall the war between the humans and a strange race known as the ‘Taurans’ lasts over a thousand years, but due to those same relativistic effects the main protagonist survives its entire duration (its worth noting that Haldeman was a Vietnam veteran).
A further dynamic to space warfare is that news will probably not travel much faster than the fighting fleets involved. Assuming you and your enemy have both developed means of interstellar travel that approach light speed, then news of a defeat may reach you just days before the enemy’s victorious battleship fleet arrives in orbit. In our modern world, where messages can traverse the globe in seconds while conquering armies would take a lot longer, we have at least some sense of security than an invasion fleet won’t land on our shores completely unannounced.
This is absolutely not true in interstellar warfare. The closest historical parallel is probably that of the Mongol invasions in the 13th century. The mongols often moved more quickly than local communications at the time, meaning that many soon-to-be conquered cities still thought the Mongols to be hundreds of miles away, only for them to suddenly appear on nearby hilltops.
8. Battlefronts and borders will probably not be ‘static’
Returning to the hypothetical example of a war between the Earth and Gliese 832, an additional element to the above scenario needs to be addressed. If both sides know that an enemy invasion fleet is at least ten or twenty years travel away, then why not evacuate much or even all of the planet’s population as a precaution in the meantime?
Planets make big, juicy targets. They’re just about impossible to move, meaning that an enemy could launch projectiles from a different star system entirely to later impact their surface with devastating effect. On Earth we’re deeply tied to the notion of static cities and national borders, but space is big enough that anchoring your civilization to a single spot can become more a liability than an advantage.
And if we’re going to evacuate the planet to avoid this not unlikely apocalypse, then why not just abandon it entirely? Have your people board an enormous fleet, perhaps composing millions of transports, pack away your most precious artworks and anything else of irreplaceable value, then head off into the stars for safety against the impending Earthling invasion.
Sure, your escape is limited to light speed, but so is the enemy’s pursuit. Theoretically, you could spend thousands of years traversing much of the galaxy in this manner. Eventually the enemy might just give up. You’re fleeing for your life – the enemy is pursuing for mere conquest. You’ve probably got a stronger incentive to keep going. Imagine you were in charge of the British government in 1940, knowing that a German bomber blitz and possible invasion are imminent. If you know you’ve little chance of surviving such an attack, why not just pack up and leave if you had the option? Its better to live to fight another day then face certain destruction.
Tying into this reality, its unlikely that the borders of interstellar empires will remain al that static, like in Star Trek and many other sci-fi series. From the moment they begin travelling between stars and colonizing other planets, what reason is there for them to stop? There’s a strong incentive in fact to just keep going, as your rivals will no doubt be doing the same. Like the European colonial empires from the 16th to 19th centuries, the galaxy’s strongest powers will inevitably keep trying to expand until there is nowhere left to peacefully settle. This could mean a WW1-style showdown eventuates between said great powers once the whole galaxy had been settled. However this scenario is made unlikely by another factor that needs to be taken into account.
7. Interstellar ‘Empires’ will be very difficult to create and maintain
This is a very broad topic, worthy of its own essays and books, but we can cover a few of the basics here. Many sci-fi series get around the question of how to maintain an effective interstellar government by making Faster-Than-Light travel a reality. But in a universe where there is (apparently) no such thing as worm holes, hyperspace or a warp drive, how does the Galactic Emperor maintain control over even neighboring star systems? Let alone the more far-flung colonies of their domain?
When we think ‘interstellar empire’ we tend to think of planets as being the most prized possessions around, but I’d contend that’s just our naive Earth-bound upbringing fooling us. Planets are relatively tiny and useless compared to stars. Stars give off solar energy in vastly greater quantities then whatever puny energy sources you could extract from a planet. Stars have a much greater mass. Our own sun contains well over 99% of the solar system’s matter.
Mining the sun may seem like a ludicrous proposition today, but is also inevitable in the long run. Even if you disassembled all of the solar system’s planets, Jupiter and the other gas giants included, you may not have enough mass to fully construct a Dyson swarm around a star to harness all its energy. You might have to start mining the outer layers of the sun itself. For these reasons stars, not planets (‘habitable’ or otherwise) will define galactic politics in the long run.
Partly depending on what form it takes, its hard to guess how big a ‘typical’ empire can grow before governing it becomes impractical. Fifty light years? A hundred? A thousand? It would seem that in the long term galactic politics would come to focus most on the rich core region. There are about 2,000 stars within fifty light years of the Earth. However if the Earth were located near the galactic core this number could be well into the millions. The intricacies of galactic geo-politics are hard to guess at. There are an estimated four or five hundred billion stars in our galaxy. They tend to be clustered closer together near the galactic core and more spaced out the further away you go. The galactic spiral arms have the densest concentrations of stars outside of the core. Then there are several, maybe a few dozen, ‘satellite galaxies’ of the Milky Way.
Perhaps a useful way to think of this layout is the analogy of a large, circular continent on the Earth’s surface. The center of this continent is extremely fertile, allowing the local civilizations to have large populations and sustain powerful empires. Radiating out from this center are several fertile river valleys (the galactic spiral arms) which are the equivalent of the Nile or Indus rivers. Between these river valleys, and towards the continent’s outskirts, are barren wastelands with only the occasional oasis (or star) to support a population. In these regions the most powerful local kingdoms cluster around the largest and most productive oases’ (or the largest and brightest stars, this would include Arcturus and Vega in the sun’s neighborhood ).
We can assume that the inhabitants of this continent can never advance technologically beyond the medieval era and such methods of transportation as horses and walking on foot. Why? Well say this continent was ten thousand kilometers across, which is somewhat larger than Asia. This would make it about a hundred million million times smaller than the actual galaxy. If we were to slow down the speed of light so that is crossed such a continent in as much time as it takes to cross the actual galaxy, it would move at a speed of only a hundred meters a year. How could somebody run even a small town, let alone an entire country, if the maximum speed of communication were that high? This is partly the reason why so few pre-industrial empires were able to grow all that large, at least not without collapsing relatively quickly. The analogy could perhaps be improved by treating interstellar civilizations as insect colonies instead. I would say it is about as difficult for a single ant colony to rule a continent as it is for a human civilization to ever rule the entire galaxy.
There is also the matter of how to control empires with large populations. Even today here on Earth, most countries have grown so large that their governments are somewhat detached from the everyday affairs of their citizens. People only rarely encounter their local member of parliament. Most will never meet their country’s prime minister or president. The splitting of the Roman Empire in 285AD into two administrative halves (with the eastern half eventually becoming the Byzantine Empire) is an example of a state growing so large that it becomes ungovernable. With modern technology this limit can probably be increased a great deal. Modern day China and India for instance have functioning governments despite having populations about twenty times greater than the Roman Empire at its peak.
A pair of simple equations can outlay the stability of any given hierarchy. Take the military for instance, a squad of maybe ten soldiers is commanded by a corporal, a platoon of three squads by a lieutenant, a company or three or fours platoons by a captain, and so on. An army half a million strong has maybe ten levels in its command structure.
The other factor is how effectively orders are communicated and carried out between the different levels. If 95% of orders are effectively transmitted at each level, then only 60% of the army general’s directives will reach and be followed by the average army private. To achieve the greatest possible stability in any governing system, either the number of levels must be minimized or the breadth of each maximized. Any system with more then about eight or ten levels tends to become dangerously unstable. Its not hard to see how this reality can limit the size of any interstellar empire just as effectively as the speed of light.
6. Battles will largely be fought by robots
Sorry Luke Skywalker, but your piloting skills will no longer be necessary.
This is something evident even in contemporary militaries. Drones are rapidly replacing manned aircraft in a variety of combat roles. While at the moment physical pilots are far from obsolete (even the drones, mind you, are still piloted by a human, just remotely) it is only a matter of time before AI programs have replaced most military personal on the battlefield.
Note that ‘most’ does not necessarily mean ‘all’ and there is good reason for this. So far computers, while growing increasingly sophisticated, are still limited by their programming. We haven’t been able to re-create a truly ‘human’ mind in silicon form. Even if this becomes possible someday, it is likely us humans and our descendants will still want to have some oversight over our technological terrors (the topic of trans-humanism i.e. whether humans will gradually merge with machines and basically become cyborgs, is a bit beyond this article. Suffice it to say it is likely, and that the distinction between ‘man’ and ‘machine’ will inevitably blur in the long run). Humans will basically be in the role of officers, commanding their mechanical foot soldiers and other war machines.
This means that manned fighters will probably never be a reality in space combat, at least not in the style of Cold-War era or Star Wars-ish dogfights. Warfleets will probably consist of individual carriers and their entourage of combat drones. This article outlines the very practical concept of the ‘Killer Bus’, where basically you fire a big hulk of metal at the enemy and have it explode just before it hits, smacking the enemy with hard to intercept buckshot.
The carriers could contain a small staff of human commanders, probably inhabiting a shielded bunker deep within the vessel. The vessel is unlikely to be very large, as maneuverability, rather than armor, will probably be the most effective defensive strategy. Its entourage of drones would include sensor craft, offensive and defensive units and other supporting craft. The most easily conceivable weapons systems carried by these drones are either missiles with nuclear (or later on maybe even antimatter) warheads, mobile laser turrets (also useful for shooting down incoming projectiles) or simply kamikaze craft in the style of the killer bus. Possibly the best example of such drones in contemporary fiction is in the movie ‘Oblivion’.
The debate over whether defensive lasers or offensive kinetics would win is seemingly undecided, and probably will be until an actual interstellar war decides a winner. At the moment our guesswork on the nature of space warfare is perhaps reminiscent of European military strategists in the 19th century. At the outbreak of WW1 most strategists insisted that future wars would be short given the vast potential of modern weapons, from machine guns to artillery to aircraft. However, few people realized just how effective such weapons could be in defense as well.
5. Wars will not be fought over gold, diamonds, princesses, or really any other precious commodity we’ve fought so many over here on Earth
From H.G.Well’s ‘The War of the Worlds’ onward aliens have attacked Earth again and again with goals that sound distinctly human, often pulled straight from the colonial era. In most of the seminal alien invasion works they invade Earth to conquer (Footfall, Worldwar), subvert (The Puppet Masters, Invasion of the Body Snatchers, Animorphs, The Tripods) or exterminate (Independence Day, Ender’s Game, Mass Effect, Halo) humanity, and more often than not steal our resources conquistador-style. There are some variations on this theme. Sometimes the aliens are mindless monsters with no higher intention then just killing everything (Alien, Beserker) or are just here on holiday to test out their martial skills (Predator). They may even be here to demolish the Earth in order to…make way for the construction of a new hyperspace bypass (The Hitchhiker’s Guide to the Galaxy).
However, when we look at the question of why aliens might really invade Earth, it quickly becomes obvious that resources is the last thing they’d attack us for. You want water? Head for Jupiter’s moon Europa, there’s twice as much water there as in all of Earth’s oceans combined. Want precious metals? There’s an entire asteroid belt of them right next door. You want energy? Feel free to build your own solar power collectors around our sun, god knows we’re not using 99.9999999% of what it gives off. There’s also half a trillion other stars in the galaxy you could build your Dyson swarms around. An excellent article covering these topics can be found at, of all places, tvtropes.org.
Take note, however, that I’m not saying wars will never occur, just not for those reasons. There are various disputes that could constitute a casus belli. Two stand out – ideological reasons and pre-emptive strikes.
Ideological conflicts are widely covered in Iain M. Banks ‘Culture’ series of novels. The eponymous ‘Culture’ is an extremely advanced civilization that, free of practically all material constraints, has evolved into an astonishingly hedonistic and carefree society. Many of the books concern the Culture’s dealings with ‘lesser’ civilizations who may not yet be advanced enough to have abandoned violent conquest as a foreign policy. The books also serve as an analogy of the modern western world’s dealings with various third world countries. The question of whether the Culture should intervene in an interstellar civil war between two lesser races, for instance, is clearly a thinly veiled analogy for whether the United States should intervene in conflicts like the Rwandan genocide. Various other works have covered the topic of a ‘benevolent’ alien invasion (The Day the Earth Stood Still, Childhood’s End). The aliens are often portrayed as having to carry a ‘little green man’s burden’ similar to the ‘white man’s burden’ that was used to justify many imperialist conquests in the past.
There are many forms this ideological struggle could take, but in the long run they will likely be very alien to our political values today. Its doubtful that traditional economic and political systems like monarchy, feudalism, slavery or even organised religion will survive a society’s transfer into space. Instead we’ll be arguing over things like which form of democracy is the most representative, or to what extent humanity should abandon its biological origins and replace our brains and bodies with machines. Five hundred years ago it was heresy to argue that the Earth revolved around the sun. No doubt our values in a few centuries time will have shifted just as much.
As for pre-emptive strikes, this is another plot device common in fiction, and is somewhat more convincing than the ‘they want our resources’ argument. The novel The Killing Star has a most dramatic (and perhaps realistic) take on this, with an advanced alien race launching an enormous barrage of relativistic projectiles which raze the Earth of all life and almost completely wipe out humanity’s fledgling presence across the solar system in a matter of hours (the rest of the book is about how most of the surviving colonies and ships are gradually hunted down and wiped out one by one, its not a lighthearted tale). The logic behind the alien’s attack is simple. The moment humanity became spacefaring was the moment we could have one day done to the aliens what they just did to us (it was ‘nothing personal’ the aliens feel obliged to say).
Similarly, in the film Titan A.E. the Drej, an advanced species of sentient beings composed of pure energy, attack (and completely destroy!) the Earth in the first fifteen minutes of the film. It is eventually revealed that they feared the completion of the ‘Titan project’, a device that could be used to convert huge amounts of energy into mass. Its original purpose was to build planets, but the Drej feared it in the role of a doomsday weapon if used against them.
In broader terms, here’s a quote by geopolitical analyst George Friedman:
When the risk of not acting is greater than the risk of acting – that is the basis for war
Given that humanity today is likely on the cusp of a rapid interstellar expansion (a few centuries away maybe, but that’s still an eyeblink in galactic terms) its not hard to imagine an advanced alien race taking notice and deciding upon a pre-emptive strike, either by exterminating us all outright or just neutering our ambitions by letting us join their own, vastly more powerful empire as a vassal species. Interstellar civilizations will have to work hard to maintain bonds of trust with each other, and I wouldn’t be surprised if many interstellar ‘Cold Wars’ occur in future. These conflicts will be driven by much the same impetus as the original Cold War, and hopefully will not turn hot for much the same reason, which is that a war would likely devastate both sides. This is an important topic to cover in detail.
4. ‘Mutually Assured Destruction’ is going to get bigger and badder than ever
So you’ve finally made it into space?
Congratulations! But just be careful. Make sure your interplanetary space-tugs don’t head off course and accidentally crash down onto some poor city, or that nobody re-configures your giant orbiting solar power collectors and turns them into the ultimate set of magnifying glasses to wipe out a few small countries, or that none of your antimatter rockets spiral out of control and vaporize some poor continent, or that a mining crew sent to the asteroid belt doesn’t accidentally (or deliberately) send a dinosaur-killer off course to smack into some poor planet.
The point should be clear. Space travel involves the harnessing of enormous energies. Most conceivable methods of interstellar or even interplanetary travel can be turned into truly apocalyptic weapon systems. Even the most peaceful spacefaring civilization is going to be frighteningly powerful. The combined nuclear arsenals of all the world’s great powers reached a peak explosive strength of about five gigatons during the Cold War. A single dinosaur killer, that is an asteroid about ten km across impacting the Earth at a decent speed, has an explosive yield equivalent to 100 trillion tons of TNT, or about 20,000 times as much.
While it wouldn’t exactly destroy the Earth, which would take many orders of magnitude more energy, it would largely sterilize the surface and certainly kill the vast majority of humans if it occurred today. The movie Deep Impact got it right.
I would also submit this Discovery Channel simulation of a collision with an even larger body, around 500km in diameter (more of a proto-planet than an asteroid).
Beyond even the power of a dinosaur killer comes relativistic weapons. The distinction is simple. It depends on whether you accelerate a mass so that it’s moving really fast, or moving really, really fast. Rather than just shoving an asteroid onto a collision course with a target, instead accelerate a much smaller mass to near light speed. The asteroid that wiped out the dinosaurs had a mass somewhere on the order of a trillion tons. To create a similar sized explosion you could accelerate a mere 4,000 ton mass up to 90% of light speed. An excellent article covering relativistic weapons can be found here.
What makes relativistic weapons so devastating is how difficult it is to intercept them. Even very advanced alien species will be hard pressed trying to stop an object you can’t even see until its almost upon you. The simple truth of the matter is that a state of constant, Cold War-esque mutually assured destruction will always exist between neighboring, settled star systems.
3. Simulations and negotiations may preclude a great number of wars
This is a topic somewhat hard to fathom, but is potentially of great enough significance that it shouldn’t be ignored. Basically, within a few generations computers here on Earth should have grown so powerful that almost any conceivable reality can be simulated in a virtual environment. What does this have to do with interstellar warfare? Quite a lot actually.
Aside from its obvious uses as an enormous training aid, if virtual realities grow sufficiently realistic as to become essential predictors of the future, then it begs the question, why bother fighting the war at all?
Humans are stupid, its a simple fact of life. We’re bad at planning, have short memories, and keep making the same mistakes. Most wars (if not all, in a sense) have been fought with both sides hoping to win. Sometimes the end result is obvious (ie. the Gulf War), other times not nearly so.
Say you’re the head of a fledgling interstellar empire, and your expanding borders graze up against a rival empire. Conflict may seem inevitable, but why not avoid the cost (and the likelihood of mutually assured destruction) entirely by designing your own VR scenarios as to the conflict’s future course and then presenting these to your rivals as an aid in negotiations? Of course there is a potential for distortions and exaggerations, but perhaps both sides would see the sense in being honest. Through such a method many wars could be averted.
Take the combatants of WW1 for instance. Both sides initially expected the war to be short, and that their side would quickly emerge victorious. Europe’s leaders may have fallen into the trap of being blinded by their own nationalistic propaganda. But if you had been able to compile the data to come up with a much more accurate picture of Europe at the time, then feed it into a scenario and run it forward in time, the fighting sides may have been much more willing to enter into negotiations.
You could point to internal discontent in the Russian peasantry, ethnic tensions in the Austro-Hungarian empire, Germany’s susceptibility to being blockaded by sea and Britain’s relatively weak land forces as reasons why neither side would be able to summon the strength for a knockout blow in a reasonable time-frame, if at all. International politics has always been about maintaining the balance of power between the great nations of the world. Galactic politics could take on a similar style, but with the galaxy’s rivals being able to summon far vaster reserves of computing power and intellect to maintain this balance and avoid a catastrophic war.
An example of this in fiction is in Iain M. Banks’ novel Surface Detail. A decades long virtual war is fought between the major galactic powers to settle a major ethical debate. The debate is over the existence of the ‘Hells’, virtual worlds created by many civilizations to punish members of their society (justly or unjustly) by interning them after death in virtual worlds where the inhabitants are subject to extraordinary and unending suffering (hence, the name of the conflict – the ‘War in Heaven’).
Schemes like this might not always work, but at the very least the leaders of the future should be a lot less naive about war, and not tend to suffer from over-confidence as much as us petty, biological humans do today. Interstellar wars in the future may potentially be very rare, sparked only by serious ideological differences. Border disputes meanwhile, are settled largely by negotiations, once both sides have showed off their respective muscles in a virtual world.
2. There will almost certainly be no aliens involved
Surprised? Don’t be. This argument has basic maths on its side.
As far as we know, as of 2017 no conclusive evidence for the existence of extraterrestrial life, past or present, has ever been found. It is one of the great mysteries of the cosmos, almost as big as what caused the Big Bang in the first place, as to why no other intelligent, spacefaring species ever seem to have evolved on worlds of their own beyond the Earth.
This mystery even has a name, the ‘Fermi Paradox’ after the physicist Enrico Fermi. He certainly wasn’t the first person to wonder whether aliens existed, but was probably the first prominent scientist with a decent knowledge of the makeup of the universe to work out the fundamental maths of the problem, which he first did in 1950 while having lunch with a group of fellow scientists. The full definition of the paradox is stated thus –
The apparent size and age of the universe suggest that many technologically advanced civilizations ought to exist. However, this hypothesis seems inconsistent with the lack of observational evidence to support it
A decade later astronomer Frank Drake quantified the paradox into a rough equation, although even he said his equation wasn’t intended to ‘solve’ the Fermi paradox, but merely a way of ‘organizing our ignorance’ on the subject. The ‘Drake Equation’ goes a little something like this –
Number of stars forming each year in the Milky Way Galaxy
X portion of stars that have planets
X portion of planets with the potential to sustain life
X portion of such planets that will develop life
X portion of these planets that will develop intelligent life
X portion that will become spacefaring
X how long such spacefaring civilizations will last.
At the moment our knowledge is very limited on all but the first two or three parts of the equation. Scientists disagree wildly on the other numbers. What is evident, however, is that no matter how generous we are with the equation, the number of observed alien civilizations is still zero. What’s stupendously unlikely though, are the odds of two civilizations of roughly equal military strength evolving relatively close to one another to the point where they could conceivably engage in a meaningful war.
Lets take the example of the Star Trek universe. Dozens of races have formed their own competing empires in the series. The Vulcan homeworld is supposedly only 16 light years away from Earth, around the star 40 Eridani A. The Vulcans are said to be quite an old race, having developed space travel around 3,000 years before their brethren on nearby Earth. Despite this, the first Vulcan flights to our own solar system did not occur until the 20th century. This begs the question, why? Why did it take so long? Is there much chance that it would take humanity three whole millennia to travel a mere sixteen light years? Even with fusion powered probes we could quite capably build today we could travel between star systems at maybe 10% of light speed without facing insurmountable difficulties.
Even more to the point, what are the odds of the Vulcans or any other neighboring species evolving, let alone industrializing and becoming spacefaring, at almost exactly the same time as us in galactic history? The universe is about 13.8 billion years old. Our own sun is 4.6 billion years old and the Earth just a touch younger. The earliest evidence of life goes back over 4 billion years, and complex life (following the ‘Cambrian explosion’) about 550 million years.
The first creatures you could arguably call intelligent evolved at least a million years ago. Homo Erectus evolved at least 1.8 million years ago, and knew how to control fire and make basic tools, meaning they fill a reasonable criteria for being intelligent. Modern humans evolved about 100,000 years ago. Within the last ten to twenty thousand years we’ve seen the development of agriculture, and the industrial revolution in just the last three hundred or so. Its likely within the next few centuries we’ll be sending probes and then manned spaceships on interstellar voyages.
While the galaxy is a very big place, its size is not quite overwhelming in the context of its age. Light can travel from one end of it to the other in about 100,000 years. Given that life took about 4 billion years to become spacefaring here on Earth, if aliens in another star system had progressed just 1% quicker, than theoretically they could have developed spaceflight and crossed the galaxy several hundred times over by now.
To work out the maths of it, less try and estimate the odds of a species evolving on a planet within a hundred light years of Earth that is less than a thousand years more advanced thn us, a sort of simplified Drake Equation. A difference any bigger would probably make one species so vastly more powerful than the other as to make any serious conflict impossible.
Its not an unreasonable guess that within a thousand years a species will have expanded outwards an average of 100 light years or more. We’ll even make the assumption that the Earth was among the first life-bearing planets to ever form in our galaxy (it shouldn’t be, since the oldest known star in the Milky Way is 13.2 billion years old, only 600 million or so years younger than the universe itself). Using rounded figures –
Age of Earth = 4.5 billion years
Technological difference = <1000 years
Number of stars in galaxy = 500 billion
Number of stars within 100 lights years of Earth = 20,000
Odds equal 4.5 million X 25 million = 112.5 trillion
Therefore, the odds we’ll stumble across (or be stumbled across by) such a close civilization are about 1 in 112.5 trillion. If life ever had or ever will emerge within that 100 light year bubble of us, then either they should already have been here long ago (and we’d likely have been colonized or at least closed off as a zoo exhibit) or we’ll reach their world first and do the same.
So we’re unlikely to have alien neighbours, but what about distant pen-pals? Assuming it takes humanity about a million years to colonize the whole galaxy (expanding at an average of 10% light speed) what are the odds that another alien species will have become spacefaring within that narrow window?
Age of Earth = 4.5 billion years
Technological difference = <1 million years
Odds equal 1 in 4,500
And these are very generous figures!
To deal with this problem, many science fiction authors have to invent some sort of timeline of galactic history that has wiped the galactic slate clean relatively recently, so that any spacefaring races alive today must be very young.
Mass Effect is a blatant example of this, with the idea that a terrifying race of aliens, the ‘reapers’ invade the Milky Way Galaxy every 50,000 years to cull it of the current crop of civilizations. Its a setting that has a lot of story-telling potential. It roughly equalizes the power of the alien races competing with humanity since all of them have developed spaceflight almost as recently, and you also have the sinister threat of the staggeringly powerful reapers lurking in the background.
Series as diverse as Halo and Star Trek touch upon this trope. Its even included in the backdrop of the turn-based strategy game Galactic Civilizations. It is said that the first alien empire that ruled most of the galaxy (the ‘precursors’) split into two factions over the question of how to deal with the emerging younger races. These factions, the ‘noble Arnor’ and the ‘evil Dread Lords’ waged an epic civil war, only for both to mysteriously vanish as the dread lords were on the cusp of victory. Their sudden absence (‘coincidentally’ not long before humanity became spacefaring) drives the plot of the game, as there is a sudden rush among the younger races to claim the now abandoned worlds of the precursors and fill in this power vacuum.
Most major works of science-fiction with a focus on interstellar politics have the feel of say, medieval or Napoleonic Europe, where you’ve got plenty of exotic, squabbling kingdoms and powerful, expansionist empires fighting bloody wars with one another. Generally the protagonists are members of a more ‘enlightened’ faction that is an obvious reference to (relatively democratic) early modern England and contrasts with the other factions of the time.
The Federation from Star Trek is the classic example, and its more democratic nature is meant to stand in contrast with the mere ’empires’ constructed by other races such as the Klingons or Romulans. A more modern view is that the Federation is basically a re-branded United States, and their opponents are dictatorial regimes akin to Nazi Germany or the Soviet Union. Rarely are the humans the unenlightened barbarians of the story, although there are exceptions, such as Stephen Baxter’s acclaimed Xeelee Sequence series of novels, where some alien races are portrayed as much more benevolent than humans (this series also includes the novel Ring which I highly recommend as one of the best and most mind-boggling sci-fi books I’ve ever read).
Ultimately some complicated backstory is usually needed to develop this reality of competing empires. The exception of course is if all (or most) of the warring factions are merely different branches of humanity. This can work well in and of itself (the Foundation series being the classic example) but this generally means such a work is set in the far future when Earth is just a distant memory, meaning it may lose some of its emotional impact with contemporary readers.
Alastair Reynold’s Revelation Space series uses this same mechanism, but with a plot that perhaps comes close to making sense (#spoilers). He comes up with the idea that the galaxy was originally home to a great number of newly evolved races, but most were destroyed in the cataclysmic ‘Dawn War’ billions of years ago.
The winning faction regretted the bloodshed and their past genocidal actions so much that they eventually constructed the ‘Inhibitors’, a race of advanced machines, to farm newly emerging intelligent life. Their role is actually somewhat similar to the aliens who built the Tycho Monoliths in 2001: A Space Odyssey, though seemingly not as benevolent. They leave alone species who stick to their home planet, but will hunt down and mercilessly wipe out spacefaring races. Why? Because in a few billion more years the Milky Way Galaxy and Andromeda will collide. The Inhibitors seek to manage this merger to limit the damage it will do to life across the galaxy. When future humanity (the books are set in about 400-700 years time) accidentally awakens the Inhibitors, interstellar war erupts, driving a very compelling plot.
1. The amount of energy and resources able to be wielded by major combatants will quickly spiral to ludicrous heights
How big were the opposing Rebel and Imperial fleets in the Battle of Endor? A few dozen larger ships varying in size from ocean liners to Manhattan-sized behemoths accompanied by a few thousand F-15-sized fighters?
Its hardly a lot for the two main combatants in a galactic civil war is it?
The opposing fleets are similar in size and composition to some of the larger naval fleets we’ve seen in human history. At the Battle of Jutland in 1916 the opposing British and German fleets had 151 and 99 vessels respectively. The Battle of Leyte Gulf in 1944 was arguably larger, with at least 211 Allied and 68 Japanese warships involved (plus about 2,000 aircraft between them).
You have to put these numbers in context. Those fleets were built by a few newly industrialized powers down here in the Earth’s uncomfortably deep gravity well in just a few short years. It makes one wonder, if you’re really in charge of a vast empire spanning thousands of stars systems across hundreds of light years, that has trillions of citizens and has existed for millennia, just how big is your Imperial Fleet going to be?
To its credit, Star Wars actually tackles this issue rather well in the expanded universe. It is said in the books that over 25,000 Star Destroyers were actually produced in the history of the empire. Its hard to reconcile this vast figure with the mere forty or so present at the Battle of Endor, but I guess we can cut the makers of the original Star Wars some slack for not bothering to produce so many hundreds and hundreds of models.
Star Trek actually features some battles much larger scale than anything in the original Star Wars trilogy (though perhaps not the prequels). In the Deep Space Nine episode ‘Favor the Bold’ we witness ‘Operation Return’, a major battle in which ‘600 Federation and 1200 Dominion’ ships take part. It’s still small by galactic standards, but given the sizes of the empires fighting in Star Trek, is probably more realistic.
As mentioned earlier, many works of science-fiction naively portray Earth-like planetary surfaces as the galaxy’s most prized real estate. Worlds commonly lack space elevators, orbiting habitats and orbital solar power collectors, even though these will probably become basic infrastructure around any industrialized planet, the same way any modern city has an airport, a highway system and is wired up to nearby power plants. One should also be aware just how expensive it is to transport large quantities of goods out of a planetary gravity well. Consider how big a rocket you need to send just a few tons worth of crew and cargo to orbit aboard the space shuttle, and then imagine how big it would have to be if a skyscraper-sized spaceship was itself the payload.
Within a few centuries, nearly all major industrial processes will probably occur in space. The amount of raw resources easily accessible in just our own solar system is truly staggering. You have to remember the main reason metals and other materials needed by an industrial society appear so rare down here on Earth is because when the planet formed all the heavier elements quickly sank down into the core. Consequently the core today is made up largely of iron, nickel and other heavy metals and makes up a quarter of the planet’s mass (or roughly twenty times the moon’s mass). Most of the metals currently found in the crust, and thus accessible to us, are ones deposited there by later asteroid strikes since the Earth formed.
In the short-term at least, the asteroids are the real prizes. The largest M-type (metallic, or metal-rich) asteroid in the main belt is 16 Psyche. It’s about 200km across and contains just under 1% of the belt’s mass, yet it contains enough iron to sustain current global production for several million years. If we split apart 16 Psyche, harvested its resources and turned it into a fleet of space warships, we would have a truly vast armada at our command. Even if only 10% of its mass was usable, that still comprises a fleet of 650,000 cubic-kilometer sized ships or, to put it in more contemporary terms, 3,250,000,000 (over 3 billion!) Nimitz-class supercarriers.
Of course there are other considerations beyond the sheer amount of matter required, but to any species just a few centuries more advanced than ourselves they should not prove insurmountable. The use of computers should preclude the need for much in the way of crew members. The energy requirements for constructing so many ships should be easily provided by solar energy (though we would be talking swarms of solar power collectors each themselves many thousands of K’s across).
Probably the main limit on the deployment of such a vast armada is the energy requirements of accelerating them up to a speed high enough to make interstellar deployment practical. Far-future civilizations with propulsion technologies we can only guess at may be able to get around this problem, but using fusion power, antimatter or anything else currently foreseeable the energy requirements are very steep. It seems you either have the choice of building a billion starships, but which can’t travel much faster than interplanetary speeds and so would take centuries or millenia to travel between stars, or you could build a much smaller fleet numbering perhaps in the thousands but that is capable of accelerating up to a significant fraction of light, allowing interstellar voyages to be measured in mere decades. Balancing these two considerations may become the largest single strategic issue in interstellar warfare.
We now come to a real dilemma when it comes to the waging of interstellar wars. We discussed above how very easy it is to harm another civilization, especially with relativistic weapons, but the problem is, it is equally difficult to conquer another civilization. If the average, industrialized star system can build a billion starships to defend its home turf, while a similar star system can only build and send say, a million starships to attack it in a reasonable timeframe, then how staggeringly difficult will it be for the aggressor to ever win?
Some sci-fi series actually do get this scale vaguely right, such as Iain M. Banks’ always reliable ‘Culture’ books. The novel ‘Consider Phlebas’ is set amidst the Idiran-Culture War, a war between the ‘Idiran Empire’ and the ‘Culture’, two of the galaxy’s great powers. Aside from interstellar travel being possible in the Culture universe, the books tend to showcase believable technologies, though often extremely advanced. The war is said to have lasted 48 years and its casualties include –
‘851.4±25.5 (3%) billion sentient creatures, including Medjel (slaves of the Idirans), sentient machines and non-combatants, and wiped out various smaller species, including the Changers. The war resulted in the destruction of 91,215,660 (±200) starships above interplanetary, 14,334 orbitals, 53 planets and major moons, 1 ring and 3 spheres, as well as the significant mass-loss or sequence-position alteration of 6 stars.’
Aside from the fact the war only went for 48 years (48 thousand might have been more realistic if FTL travel isn’t possible) this sounds like a very reasonable death toll for a war on the scale described. There’s also another scene in the novel Surface Detail featuring an interstellar battle in which one civilization awakens an entire planetary disk’s worth of ancient alien factories to start building a fleet of warships (its a long story). The disk consists of millions upon millions of abandoned ‘fabricaria’ orbiting around a gas giant planet, and is used to produce a fleet of 230 million moderately advanced warships in just a few weeks. Its a rather dastardly plot, and showcases the industrial might of any advanced spacefaring species. There’s another example in the novel ‘Excession’ where a single Culture ship is able to produce a fleet of 80,000 warships in a similarly short time-frame, ending a brewing interstellar war in one fell swoop.
If just harvesting the asteroid belt won’t cut it, then potentially you’ll have to go even further and start taking apart the planets themselves. Mercury for instance has over 14,000 times the mass of 16 Psyche. The big difference between asteroids and planets however, is that the latter have deep gravity wells that will exponentially increase the amount of energy it takes to mine them. You can mine an asteroid using conventional methods not unlike those we use on Earth. Basically you chip or drill away at it for a while, then collect the fallen chips and take them away to refine them into useful materials. Simple yes?
But a planet is very expensive to just ‘chip away at’. Consider again the example of the space shuttle. Its payload to Earth orbit was just 24 tons. Now imagine how many shuttle launches it would require to dismantle the entire Earth piece by piece. We’re talking many billions and billions of launches. Its just not a practical number, even if you’ve got a million years and as much solar energy as you could hope for.
What we’re talking about here is the planet’s ‘gravitational binding energy’. There’s an excellent article here on just how difficult it is to completely destroy (as opposed to simply razing the surface of, or even liquefying) an entire planet. You essentially have to accelerate its entire mass up to its escape velocity so that it won’t all clump back together again. If you really wanted to mine a planet its much cheaper to just detonate it and turn it into an asteroid belt in one fell swoop than to do it piece by piece.
Ultimately these challenges mean that even an advanced species would probably take quite a few thousand years to mine an entire earth-sized planet. The potential rewards though are staggering, and what’s a few thousand years in galactic terms? The Earth is twenty times the mass of Mercury, so we’re talking 910 trillion supercarriers. Its a fleet that would stretch end-to-end to Alpha Centauri and back four times.
In the long-run, and we’re talking projects that could take millions of years, you can go even bigger. The gas giant planets combined have a mass 445 times greater than the Earth. Though they largely consist of lighter elements like Hydrogen and Helium, you could perhaps fuse them into heavier and thus more useful elements using fusion reactions like those found in stars. Then there are of course, the stars themselves. The sun is almost a thousand times larger than Jupiter, and the galaxy has a mass between 200 and 400 billion times that of the sun.
Anyone else lost count of how many supercarriers we’ve built yet?
This enormous escalation applies just as much to energy as well as matter. The Three Gorges Dam, currently the world’s largest hydroelectric plant, produces 18 gigawatts (billion watts) of electricity and the total amount of energy consumed by humanity as of 2010 is 16 terrawatts (trillion watts).
By comparison, the constant influx of solar energy received by the Earth from the sun is 174 pettawatts (thousand trillion) and this is just a tiny fraction of the sun’s total luminosity of 384.6 yottawatts (trillion, trillion, watts). The sun provides 24 trillion times as much energy as we currently use, and the entire Milky Way Galaxy many billions of times more than that. The best way to harness this enormous power source is to start building Dyson swarms.
The ultimate inaccuracy in nearly all science-fiction works, especially those depicting warfare, is that sci-fi writers often have no sense of scale. There’s even a trope with this very name.
Consider how many thousands of settled worlds supposedly made up the Galactic Empire. Does that mean they only have an average of one Star Destroyer each? Or even less? Oddly enough the Death Star is perhaps a reasonable achievement for a civilization on the scale of an galactic empire, though maybe it would have made more sense for the Empire to simply build a few million tried and tested Star Destroyers instead? One wonders why the empire doesn’t start building Dyson swarms as well, allowing it to harness unprecedented amounts of solar energy, or at least the odd orbital habitat to house its citizens somewhere other than the uncomfortably deep gravity well of a planet.
It would do wonders for the galactic economy.