Anybody familiar with the Keno Don Rosa Unca Scrooge story where our anatidoid heroes accidentally create a hole all the way into Earth's core by spilling some very powerful solvent, and have to go after that solvent before it eats away all matter and condenses it into superdense dust?
Don Rosa got much of the gravity issues right, but he thought that there would be some negative pull towards the end of the journey. And actually he might have had that right, as Earth wouldn't be a hollow sphere; there could be higher-order effects from the basically cylindrar mass surrounding the narrow hole. Or then the Junior Woodchucks got it wrong, and the "negative gravity" they observed was just irregularities in the acceleration of the cart they used.
As the ducks reach the dead center, where the solvent has eaten a little cavity for itself due to yo-yoing for a while, they correctly observe zero gravity - although the solvent itself seems to have great mass from all the superdense waste it has accumulated, an issue that is conveniently forgotten after Unca Scrooge bags the stuff in a solventproof jar.
Other issues not evident in the comic, but not necessarily incorrectly portrayed, either, include the fact that the hole wouldn't necessarily be straight: the solvent would encounter coriolis forces on its way down, possibly influencing its path (even though its progress was necessarily slow and friction-limited as it ate through the rock). But the ducks rode down in a cart hugging the walls, not in a freefall capsule, so the curvature wouldn't affect the adventure.
There's also the classic Jeff Hawke adventure where aliens have pulled a cable through their smallish planet to construct a powerful magnet to regulate their planet's climate, and invite/abduct a few human engineers to help them out after a civil war severs the cable and savages the planet. That one gets the gravity part right, too - and it, too, involves a cart riding along the walls for the most part, leaving the freefall stuff for a single character only.
The Jeff Hawke tunnel was in a vacuum, another thing correctly and convincingly portrayed. The fatigued heroes just didn't think it through, though, so one of them got sucked into the shaft when the lid was forced open. He fell all the way through, using a bottle of compressed gas to compensate for any momentum lost, and emerged at the other pole. (The pole-to-pole ride also eliminated coriolis forces and thus fatal collisions with the walls.)
The Unca Scrooge one was also in a vacuum, with the Junior Woodchucks (or was it Gyro Gearloose?) correctly describing how the presence of 6,700 km of air in the hole would have made the rescue operation impossible. (A quantity of air did enter with the solvent initially, before the shaft was air-sealed, and there was enough of it left unconsumed by the solvent for our ducks to shed their spacesuits at the core.)
Dontcha love it when even Disney gets the science right for once? I wonder how Trek would have handled the concept... They did grasp things like space elevators, even when they fumbled easy ones like black holes or exploding stars.
Timo Saloniemi
