Between 1981 and 1996, the University of Colorado at Boulder hosted a series of conferences known as The Case for Mars, during which detailed arguments and plans emerged for the exploration and colonization of Mars. Unlike the other planets in our solar system, the conferees reasoned, Mars has a (nearly) livable climate and (trace quantities of) air and water and thus makes a plausible home for human beings in the future. Now, in the new and final season of Battlestar Galactica, a ragtag refugee fleet has come upon a ruined Earth—a miragelike disappointment of shattered cities and radioactive oceans. In the wake of this discovery, there has been understandable turmoil over what to do next: Where to go, whom to trust, who should be in charge for the difficult journey to somewhere better.
But there is a Case for Earth to be made here, not least because it gives human and Cylon a chance to live in peace without actually breathing down each other's necks. Certainly, whether they can live together without a planet is a question yet to be answered.
On the one hand, it's clear that Cylons are more than mere machines. They have free will, and a few have proven over and over again that they're trustworthy allies of the human race. That counts for something. In fact, I could argue that Cylons who've broken their programming are actually more trustworthy than human beings. A little stronger, a little smarter, less erratic and less prone to despair, they seem to have a stronger emotional center than we do. And you'd hope so, right? Or else why were they were built at all, and how did they managed to infiltrate and devastate 12 well-armed human homeworlds?
On the other hand, the dissident Colonials do have a point: Even the rebel Cylons are dubious allies, having pulled the rug out from under humanity more than once. They are members of a different species, after all, with different material and emotional needs and with their own separate survival imperative. Too, most of the Cylon models are like Blade Runner replicants: emotionally inexperienced and therefore lacking in empathy. In a way they're like children. Think of Leoben on New Caprica, trying over and over again to live as Starbuck's husband and really spectacularly failing to understand her resistance. Or Cavil, the Cylon leader, talking blithely about "reducing the human population" as a means of restoring peace and cooperation. And remember how shocked Caprica Six was when she realized that her friend Baltar might be killed, and that if that happened she would really, actually never see him again? Kids can be cruel, and because their worldview is simplistic they can also overreach, overreact and turn on a dime as new information is introduced. The Cylons launched their war with a terrible hubris, and while they're slowly coming to terms with it and learning to see themselves—and us—more clearly, they're hardly Nobel Peace Prize material, or even really grownups by any normal human definition.
Also, importantly, there may still be sleeper agents among them whose programming hasn't switched on yet. Dispensed by shadowy machinery in the depths of space, maneuvered by gibberish-talking "hybrids" and controlled by some master plan even they don't understand, the individual Cylons have no real idea what purpose they're intended to serve. Although orderly, their civilization is fundamentally clueless, and they know a timer can go off in any of their heads at any time and start issuing new instructions. So, really, it's only after the sleepers are exposed that you can start believing in their free will.
The humans may now be too weak to survive without Cylon assistance, and the rebel Cylons have little hope against their own nation without the protection of the Colonial fleet, so it appears that some kind of alliance is necessary. But if anything goes wrong—if old resentments bubble over or itchy fingers slip for even a moment on the triggers of war—with Galactica and the Cylon base ship sitting practically nose to nose and the fragile human fleet caught in the crossfire, both species could be wiped out in an instant. And let's not forget, there are still billions of main-force Cylons out there, waiting for a chance at revenge!
It seems to me the most logical course of action—the one least likely to end in tragedy—is to set up a permanent base on (or, better yet, beneath) the blasted surface of Earth. Crazy? Not at all. The cities may be blasted to smithereens, the plant and animal life may be stunted, the air and soil and water may be contaminated with "residual radiation," but it's still way better than no planet at all.
In the first place, "radiation" isn't some ghostly contaminant that leaches into matter and stays there like a bad smell. Rather, it consists of energetic particles—photons, neutrons, electrons and protons—emitted by unstable atoms. Each element on the periodic table comes in different flavors, called isotopes, each one a slightly different weight due to an excess of neutrons in the nucleus, and as a general rule the more extra neutrons there are, the more radioactive the isotope will be. And yes, the fallout from an atomic explosion is full of unstable isotopes, and it really does get into everything. In the long run, the most dangerous of these are the bone seekers—radioactive strontium, barium and radium—that are chemically similar to calcium and can be absorbed into living bone tissue. There are also radioactive variants of calcium and iodine, "heavy hydrogen," iron and other elements that can find their way into the body. These are a deadly gift that keeps on giving; unlike uranium or plutonium, we can't walk away from these. They're absorbed by our bodies as nutrients and then they emit their radiation from the inside, where we're most vulnerable. The possible results include inflammation, immune suppression, cancer and, in extreme cases, radiation sickness and rapid death.
However, every radioactive element has a half-life over which it decays. Every time it coughs out a "hot" particle, the atom gets one step closer to being stable, and in fact the most radioactive isotopes are, by definition, the ones most likely to split and therefore the shortest-lived. The hotter they burn, the quicker they burn out. Isotopes like calcium 45 and 47, iodine 123 and 131 and iron 59 are really nasty, but it takes only a few weeks for them to lose half their potency, and within a hundred years they've transmuted themselves into harmless substances and are no longer radioactive at all. Conversely, uranium 233 has a half-life of just under 130,000 years and will stick around for a long time but is not really all that dangerous—especially in trace amounts. For the most part, fallout is a short-term problem, which is why the cities of Hiroshima and Nagasaki—the only two cities on Earth that have actually ever been nuked—began rebuilding within five years and were, within a few decades, no more radioactive than any other city. This is also why the Cylons were able to occupy Caprica and the other colonies after destroying them.
But will every target be so lucky? When the Romans sacked the city-state of Carthage in 146 B.C., they scattered the bricks and then salted the ground to make sure nothing would ever grow there again, and (sadly) there are nuclear weapons capable of doing something very similar. Certain isotopes seem perfectly tuned for poisoning the ground, including cobalt 60 and strontium 90, with half-lives of 5 years and 29 years. Active enough to be deadly and persistent enough to outlive entire civilizations, these materials take hundreds of years to cool off, and if enough of them got thrown around in the Cylon apocalypse that took out Earth, then yes, the place could still be radioactive a thousand years later.
Still, it's important to ask: Is that really a reason to leave? You may not want to grow food in radioactive soil, but you certainly can remove the offending atoms from the mix. In principle, pulling strontium and cobalt out of dirt should be no more difficult than any other sort of mining, refining or purification process, and once the bad elements are gone, the soil is as safe as it ever was. The same is true for water, air, rubble, decaying biomass or what have you. Now, this means safe farming soil could be as expensive as starship fuel, so I'm not saying it's an ideal solution. You'd want to keep it in greenhouses so outside soil couldn't sneak in and recontaminate it. But when your food supply consists mainly of reprocessed algae grown in tanks of reprocessed sewage, this still seems like a real step up.
Similarly, wouldn't a planet-sized air supply be better than a handful of breachable hulls? You might need to filter it—no one goes outside for long periods without a dust mask!—but isn't that better than living in the wilds of space? Think of it: After four years of kicking around the universe, hunted and harried, would you turn your back on a ready supply of water, metal, hydrocarbons, flat ground and just about everything else a civilization needs to function? I'm not saying they should get rid of the spaceships, but I for one would rather live in a plastic dome than a metal barracks. It may not be quite the garden spot that New Caprica was, but Earth's biosphere has bounced back from a lot of insults over the past 3.5 billion years, so there may be some life in the old gal yet.
Wikipedia: The Free Encyclopedia (en.wikipedia.org): "The Case for Mars"
Britannica 2008 Ultimate Reference Suite: "Hiroshima," "Nagasaki," "Carthage," "Life"
The Dynamic Periodic Table of the Elements: www.dayah.com/periodic/