There are only four ways of providing a given acceleration of gravity, until some genius finds a way to create it. One is simply to accumulate the necessary mass. Thought was given to altering the orbits of all the five largest Uranian moons, smashing them together. That would have been fun, don't you think? But it wouldn't have provided as much gravity as the engineers were seeking, and besides, it would have taken forever for the resulting mass to cool enough to be useful.
Then there is Pluto's Solution, which I guess is technically Method 1A, since it also involves accumulating mass, but it certainly feels like a different solution. Over a century and a half people have been venturing out into the really distant spaces—so far that Brementon and the sun look like next-door neighbors—bringing back tiny black holes. I mean really tiny. Smaller than atoms, they say, though I find that unlikely. There are now thousands and thousands of those little black holes orbiting near the core of Pluto, through solid rock that presents no more obstacle to them than interstellar space. There's enough of them in there now to provide about one third of a gravity on the surface. Those little suckers pull hard!
One day the black holes will suck all the mass of Pluto into what would be, so I read, a tiny-to-small black hole (the large ones contain whole galaxies, if you can believe that). There's no question this will happen. The debate is about how long it will take. Prevailing opinion is at least a million years, so you may not want to unload your real-estate holdings. Of course, some scientists claim it will happen next Tuesday. Take that into your vacation plans.
It's the sort of predicament that appeals to Plutonians, a fatalistic bunch. They get a kick out of telling newly arrived tourists about the latest catastrophic prediction.
The Oberon engineers rejected the Pluto Solution, mostly because of the almost unimaginable expense and the time it would take. Black holes are very rare, and cost the planetary income of some asteroids. They are not labor-intensive, and one hoped-for side effect of the Gravity Project was putting a lot of people to work, jazzing the economy.
And I suspect they decided to wait a few centuries, see if Pluto did fall into a black hole.
The third and fourth ways are also related, and don't involve actual gravity but the illusion of gravity. If a spaceship accelerates at a steady rate, it will seem just like real gravity to an observer inside the ship. Einstein noted that no experiment done inside the ship could distinguish between "real" gravity and the force of acceleration. If you're wondering how I, a mathematical dunderhead, know all this stuff, it's simply that I had to memorize great swatches of it as dialogue when I played the old windbag in Einstein and Marx, the techo-philosopho-porno extravaganza you've never heard of because it played three times before going to a richly deserved extinction. ("Ken Valentine manages to bring some much-needed humor to the role of Albert. But this will only appeal to communist theoretical-physicist necrophiles. There must be two of them in the system, maybe three. Let them have it.—The Phlegethon Phlogiston)
There are several insurmountable hurdles to using method number three for "residential" gravity. For one thing, your residence would spend most of its time moving like a bat out of Pluto. After a few months (weeks? Do the math yourself), you'd be moving near the speed of light and time contraction would be a problem. Well, then why not accelerate twelve hours out, turn around, and accelerate twelve hours back? Oddly enough, that would work, though the expense would probably be prohibitive. It would avoid the other problem of constant acceleration, though: the fact that we have yet to produce a means of propulsion that can operate indefinitely, at any useful thrust. When you got home, you could refuel.
One of the many unlikely propositions I have sold in a lifetime of selling was based on that idea. We set up a Big Store, selling shares in a company that was "right on the edge of a breakthrough!" in the field of light-speed travel. The dodge was to put your money in the bank, get on the ship, and return a few hundred years later to reap the compound interest. The trip would only be a few months subjective time. Brilliant! Of course, we were the bank. And I already mentioned what happened to W. C. Fields's bank account. But you'd be surprised how easy a proposition it was to put over.
So now we come to the fourth method, or 3A, depending on how you apply the rules. This is the wheel, or the bucket on a rope.
Put some water in the bucket and whirl it around your head. The water doesn't spill out. Magic! Actually, centripetal force, which is a constant acceleration toward the center of a circle.
If you build a wheel in zero gee and set it spinning, you can walk around on the inside of that wheel just as if you were in real gravity. If you want to be heavier, you spin the wheel faster. Slow it down for less gravity.
Make the wheel very large....
We've been building structures like this since humans went permanently into exile in deep space. The asteroid belt, the lunar Trojan points L4 and L5, the Jupiter and Saturn Trojans, J4 and J5 and S4 and S5, all are thick with wheels like this, or more often, cylinders. Up until the inception of the Oberon Gravity Project the largest of these artificial worlds was about sixteen miles in diameter.
The Gravity Project proposed a wheel one thousand miles in diameter.
To make a leap like that you need a significant new technology, or a major breakthrough in an old one. The Oberoni had a little of both.
When I had last come through about twenty years before, Oberon II had looked like this:
(—o—)
The O was the hub of the wheel-to-be, hollow in the center. If you were building an interplanetary Conestoga wagon that was where you'd put the axle. The long lines were the first pair of a proposed twelve spokes of the wheel. The two little arcs at the end were all that had been built so far of the outer rim of the wheel, the place where people would live and work.
Today it looked like this:
Four more spokes finished, and two separate portions of wheel arc. Each spoke was five hundred miles long. Each arc had reached a length of about six hundred miles. It looked like the project was half through but it was actually further along than that. You learn as you go, and getting started was much tougher than getting finished. They expected to wrap the whole thing in ten more years. That is about half a mile of rim every day. Don't ask me how they do it. I've stood at Edge City and watched the work, and I still don't know.
Oddly, a thousand-mile wheel turning once an hour produced just about the 0.4 gravity the engineers had in mind. From Luna, with a decent telescope, you could tell time by Oberon II. And since the diameter was one thousand miles the circumference was π thousand miles: 3,141.592654 miles. That led to the first of a long line of disparaging nicknames during the early construction: Pi in the Sky. But nobody was laughing now.
"Yeah, whaddaya want?"
"Is this the computerized answering service of Oberon National?"
"You got a problem with that?"
"I got a problem with your tone of voice."
"Fuck you. You dialed the aggressive-response number. Hold on, asshole, I'll connect you with obsequious response, if that's all you can handle. Good afternoon! I hope I can be of service.