SciFi Round Three: Larry Niven and the Limits of Retconning
We’ve talked about the contradictions, impossibilities, and failures in worldbuilding of several different stories. But what happens when a novel has been printed, a movie filmed, or a game sold to thousands of players, and then a contradiction comes up? Not even Clement foresaw everything.
There are several options here. One is to ignore the contradictions entirely, like the military tactics in Star Trek (trying to fix that is why I’m not supposed to write Star Trek stories anymore – MB). If you can re-write the entire medium, many contradictions can be resolved in the new version, such as in the 2003 Battlestar Galactica miniseries (although the later seasons of the show introduced more problems). The third option is to introduce corrections. If you have a game, introduce a rule patch. If you have a story, add material to a sequel that was either not referred to or contradicts parts of the original. This is a retcon.
Retconning is limited, though. The premise of a story can only be twisted so far before it breaks. This time, we’ll consider this problem in the Known Space series of Larry Niven.
Ringworld And Its Problem
In the extended setting that is Larry Niven’s Known Space universe, the Ringworld is the single largest structure. It is exactly what it sounds like – a ring around a star, a million miles wide, six hundred million miles long, and up to a thousand miles thick (we can pardon Niven for not using metric). Niven specified the implausibly strong materials that would be required for the ring to hold together while spinning fast enough to give the equivalent of about 1 g on the inside of the ring, and to hold together a smaller interior ring of separated squares to give days and nights inside the main ring as they rotated. Whoever built it loaded up the inside surface with a carefully-landscaped Earth-like biosphere.
But Niven missed something critical. As anyone who has studied Newtonian gravity, particularly the shell theorem, will remember, while there is no gravitational field inside of a uniform-density sphere, there is one on the inside of a uniform-density ring. So while a Dyson Swarm can be stable, the ring cannot be. Put the star in the exact center of the ring with any slight relative velocity and it will fall away from it. Out-of-plane perturbations are stable and lead to oscillations, but in-plane perturbations grow. And so the star falls onto the ring; which will destroy the ring either as its orbit around the star changes or as it runs into it.
This is a serious problem, which Niven’s readers were quick to point out to him. And so what did Niven do? He wrote a sequel.
In the sequel, The Ringworld Engineers, Niven reveals to the reader that the Ringworld was not just a Big Dumb Object. The engineers who built it had installed an active control system: Bussard ramjets powered by fusing hydrogen from the star’s stellar wind, which had worked without maintenance for thousands of years (impressive engineering). Then a reader pointed out that the magnetic fields from the ramjets would have fried the nervous systems of the creatures living on the Ring. So a way to fix that shows up in the third book in the series…
The Limits Of Retconning
So Niven has been adept at saving his Ringworld from destruction. But other problems in the setting can’t be retconned away.
In a Known Space story called “Neutron Star”, a human exploration team takes a ship with a (supposedly) indestructible hull and drops it on a near-hyperbola passing a few kilometers from the titular neutron star. But they forgot the tidal forces, and all died, smashed into opposite ends of the hull. This by itself is bad enough. It gets worse when the salvage team doesn’t figure out what happened, and sends a second ship to re-enact the mission (that pilot figures things out just in time). But Niven forgot that in flying by the star, the ships would acquire incredibly fast spins – about 40 revolutions per second. That fast of a spin would kill any human, even if she were sitting at the center of mass of the ship: there would be an effective force gradient of several hundred gravities from one side of his head to the other. Niven has quite sensibly not attempted to retcon that part of the plot, since then the entire story goes bye-bye.
Meanwhile, the Ringworld was inhabited by descendants of The Pak – Human Aliens who were supposedly also the ancestors of all Earth-descended humans, having settled Earth some millions of years ago. This was impossible even when Niven wrote the first Ringworld book in 1970 and the first story featuring The Pak, The Adults; in 1967. Genus homo traces back to the rest of the apes with a divergence time from genus Pan of 4-5 million years. This was known by blood serum albumin work as of 1967. Niven retconned The Pak to have also been ancestors to the chimps, gorillas, and orangutangs; but of course that doesn’t work either. The fossil record and basic biochemical similarity between all Earth-based life rules out any panspermia, directed or otherwise, at least for everything that doesn’t do a lot of horizontal gene transfer. And all that was known in ’67; all of the more sophisticated genetic work that’s been done since then has just been filling in the details.
But if Niven were to erase The Pak from Known Space, then none of his Ringworld-native characters would exist, and that is too big of a perturbation to keep the story within the bounds of what he’d like to tell. And so, again, he doesn’t retcon them away.