So, as discussed, we’ve got roughly the same chance of getting to Mars in halfway decent (read: alive) shape as a one-winged fruit fly has of making it from here to Calcutta. (In fact, my money’s on the fruit fly.) And once we’re there, our problems are just beginning. The moon is closer, but an even worse place as far as livability is concerned. And those are the only two worlds we can even think about reaching. As far as extra-solar Earths are concerned (if there even are any), unless some geek with coke-bottle glasses comes up with warp drive in his parents’ basement real soon, we’re stuck trying to cross the cosmos in first gear.
So, it appears that there’s no other world in practical reach -- certainly nothing in the next century or so, which everybody with a PhD is telling us is longer than we’ve got left here.
So what can we do?
We can make a world.
We can, in theory, make at least two, and possibly more.
Everyone (well, everyone who’s reading this, all three of you) knows the “rubber-sheet” model of gravity -- the four-dimensional equivalent of a rubber sheet stretched taut. Drop a bowling ball in the center and call it the sun, then send a BB rolling around it and call it Earth, and you got yourself a model of how gravity works.
Sort of. As with just about everything else we’ve been discussing, it’s a bit on the simplistic side. Gravity systems are a lot more fluid, and though the influence of mass decreases with distance, it never really fades completely. The upshot being that, like the currents and ripples of a river, gravitational forces from the sun, the moon, and the Earth create eddies and stable points at certain locations. They’re called LaGrange Points. There are five of them in the Earth-Moon system, and of them, L-4 and L-5 are so stable that large objects plunked down in the middle of them tend to stay there, to all extents and purposes, forever.
Gerard O’Neill, in his book The High Frontier, proposed building space habitats -- huge, orbital colonies -- within the stable loci of L-4 and L-5. We are talking big, here -- these things are to the International Space Station or Skylab what a luxury high-rise is to a refrigerator box under the bridge. We’re talking cylinders five miles by twenty miles; big enough to comfortably house anywhere from a thousand to five thousand or more people. With materials mined from the moon or from NEOs (Near-Earth Objects such as asteroids and meteoroids) and aggressive recycling and population control, the colonies could be self-sufficient, or very nearly so. Populations of 5,000 or more in orbital colonies at both L-4 and L-5 would provide a more than sufficient gene pool for the human race’s survival. It’s even conceivable to build “Ark Habitats” that would be dedicated botanical and zoological gardens. Sufficient shielding to guard against cosmic storms wouldn’t be a problem, since it doesn’t matter how massive the habitat would be; the only place it’s going is around and around its own little orbit.
Gravity’s not a problem either. If you’re living on the inside of a cylinder instead of the surface of a planet, it’s easy (well, easier) to create artificial gravity by simply spinning the cylinder. Centrifugal force pushes everything on the inside against the inner aspect of the torus, just like in those old Tilt-A-Whirl rides at the carnival. (And if the cylinder’s big enough, the inner-ear effect will be diluted, so you won’t constantly feel like throwing up everything you’ve eaten since you were five.)
What’s more, the LaGrange Points aren’t just confined to the Earth-Moon system -- there are points of stability everywhere planets and moons do their complex dances. Colonies built at these points are, it seems to me, the only viable way of leaving Earth behind. Controlled environments, with regulated day and night cycles and normal “gravity,” free from natural disasters and presenting a much smaller target for bolide impactors, make a helluva lot more sense to me than trying to hardscrabble a living on the moon or Mars.
For most of recorded history we’ve been searching for a way to get to Heaven. Now, finally, we have the tools; if we’ve got the will and the fortitude as well, we can build Heaven.
It’s that, or take our chances on a world that’s all too rapidly going to hell.