Sci fi stories set in space always seem to ignore three horrendous difficulties: escape velocity, reentry heat, and artificial gravity. Ignoring the first two makes it easy to hop from planet to planet. Artificial gravity lets film crews shoot on solid floors. It makes it possible to avoid any counter intuitive interactions that occur in from a 360 degree environment. It also allows one to ignore the terrible effects long time weightlessness causes (muscular atrophy). But for a blog post let’s not ignore anything. What challenges lie ahead for designers of gravity drive?
Gravity has always been deceptively simple yet overwhelmingly complex. When a flat earth was circled by other celestial bodies the idea of gravity must have been a moot point. Things just went down. The rotating earth orbiting the sun had to have some force to keep things from falling/spinning off. That force was soon to be called gravity.
Newton’s gravity become the stuff of legends for science, because it proposed that the properties of heavenly objects obeyed the same rules as the ones down here. Newton even developed an equation for calculating the gravitational force between to objects.
What Newton was unable to do was explain why gravity exerted the force it did. This work was staggeringly complex and lay undone until Einstein, over two hundred years later. Gravity resulted from the curving of time and space.
Einstein’s equations revolutionized celestial mechanics, but gravity has remained as difficult as ever. How is the curving of space-time achieved? Some scientists have posed the idea of a graviton, a particle like a photon that would carry gravitational force. No such particle has ever been found.
Where would it be located? In the nucleus? Hovering around matter? How would one extract it? In terms of the four forces in physics (electromagnetic, strong, weak, and gravity) extracting the strong force from the nucleus results in atomic fission, which can create an atomic explosion. Would the science of manipulating gravitons simply be too risky or expensive?
It’s simply impossible to tell at this point. Despite the simplicity of the falling apple that inspired Netwon’s gravity, gravity is still nowhere near being understanding, and it’s so complex that your lay person without an intensive scientific education probably won’t understand it anyway.
So ignore gravity in your sci fi tales? If they involve ships moving from planet to planet I’d say yes. Otherwise, centrifugal force might be a workable replacement. If your craft were spinning fast enough, you should be able to keep your feet on the ground (that ground being the outermost layer of the wheel like space ship). But who wants to go thtrough the trouble of explaining that kind of architecture?