Haven’t we put enough sattelites and probes in space to have discovered such a planet, if it existed?
Couldn’t the voyager space probe have seen behind it as it left the solar system enough to have noticed the presence of another planet in earth’s orbit?
This seems like a good place to ask about another Nivenism. Just why is the Ringworld unstable, other than to give him an excuse to crank out another book?
Consider the Ringworld to be fixed, and its sun to be freely moving (this is valid due to Newton’s Third Law). Now consider the Sun to be slightly perturbed from the center. Using what we know about toroidal planets, we know that the sun would then have an unbalanced force on it, pulling it towards the nearer side of the Ring, with the result that it would eventually colide with the Ring.
But the cranking out another book part was probably inexcusible, given how the Ringworld sequels turned out.
The Ringworld is a rigid body, held together by mechanical continuum forces (i.e. the internal tension of the body); in essence, you can treat it as a suspension bridge with no endpoints. As a result, unlike an orbital body, it doesn’t depend on the balance of gravitational and interal forces to maintain equilibrium, as planets about the Sun do. So, when the Ringworld is perturbed so that the sun is off center, there is no regulating force to return it to center; it orbits out in an increasing spiral. It will continue to move away from center until it collides with the sun. A simple freebody diagram will demonstrate the inherent instability.
The MITSFS (MIT Science Fiction Society, pronounced “misfits”) were reputedly the first to bring this to Niven’s attention (as well as the retrograde rotation of the Earth in the first edition printing of Ringworld), and the result was The Ringworld Engineers, which was little more than an attempt to correct the technical errors of Ringworld (though in my estimation it was actually the best of the Ringworld novels).
There are numerous other problems with the concept of the Ringworld–for one, why make it so bloody big, when a much smaller construct that didn’t rotate about a central star would do just as well without requiring strucutural materials that extend into the realms of fantasy?–but Niven stuck with the concept, all the while acknowledging its absurdity. (The Pak would never place their “child” population in such an indefensible construct.) Massive magnetic ramjet engines to combat instability? Pffft. But at least he had vision. Personally, I think his Integral Trees/Smoke Ring was more innovative, though still lacking in literary value.
And yeah, The Ringworld Throne sucked harder than a Dyson (vacuum, not Sphere). I didn’t even read the followup; Niven really should retire before embarassing himself further. The best of authors seem to have no more than 2 or 3 great novels in them, and Niven cannot count himself within those ranks. He’s written some great short stories, though.
Stranger