Dear Hank & John, on episode 173, has a question of whether ghosts can ride in cars, for a book the asker is writing, in which the protagonist is a ghost who travels a lot. Hank responds that as a writer, you get to make up the rules, because fiction. In offering several conceivable ghost rules, he makes the point that if ghosts are totally ethereal, then you have to ask why they don’t just fall to the center of the Earth.
But that’s not right—if they’re completely incorporeal, of course they wouldn’t fall to the center of the Earth, because they have no mass for the Earth to attract. They’re probably like self-motivated neutrinos; they can go right through anything they like, only they can also choose when and where they go.
So, if they are incorporeal, they can absolutely go for a car ride, if they like. It’s just that, since they’re incorporeal, the car isn’t actually causing them to move; they have to anticipate it and maintain the same velocity and acceleration to stay “in” their seat, and they probably tend to sink into the seat a bit when the car speeds up, or slide left or right a couple inches when it changes lanes, and maybe, sometimes, when the driver slams on the brakes, the ghost has passed through the front seat and is in the middle of the glove compartment before they catch themself.
Now I hope someone makes this happen in some (probably not very good) tv show, because I want to see it outside of my mind’s eye.
Or, maybe, ghosts are incorporeal in the sense that they are physical in nature, just not material—purely energy beings. But it’s not our matter that keeps us from falling through the ground, anyway; matter in our kind of environment rarely interacts directly with other matter, and when it does, things tend to get a bit nuclear. Instead it’s the electromagnetic fields of us and other things, repelling each other, that keep us from falling through each other, and given that, it seems reasonable to suppose that matterless beings would find themselves subject to similar forces.
They may not have matter that would take out the surrounding area if they try to pass through a chair just a little bit wrong, but they would still be rearranging themselves to go around the matter and through the field of the object and shifting back when they’re on the other side. Maybe it’d be like forcing a T-1000 through a wire mesh: he could do it, but he’s got to glob himself back together afterwards, so he probably won’t do it all the time or absentmindedly.
I’d like to see that one, too.
And now that I’ve written this most valuable of missives to the void, I think I’ll go hit play and let Hank finish his answer.