In sci-fi with “spinning” ships to make gravity, how does someone drop something and it lands at their feet?

Question

This fogs my brain every time I watch one of these shows and I feel like maybe I’m completely misunderstanding the physics.

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You’re in a “ring” ship. The ring spins. You’re standing on the inside of the ring so it takes you along with it, and the force created “pins” you to the floor, like a carnival ride. Ok, fine.

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But that’s not gravity, and it’s not “down”. Gravity is acceleration, so what keeps the acceleration going in the ring ship is that you are constantly changing your angular momentum because you’re going in a circle. Ok, so when you let go of something, like a cup or a book, wouldn’t it go flying towards the floor at an angle? If you jumped wouldn’t you look like you rotated a little before you hit the ground, because you’d, for that moment, be continuing the momentum of your angular velocity from when you left the floor and the room would continue on it’s new, ever turning, course?

Wouldn’t it kind of feel like walking “uphill” one direction and “downhill” the other, with things sliding about as the room “changed” direction constantly?

Am I just COMPLETELY missing this idea and creating a cause and effect that doesn’t exist?

In: Physics

Answer 1

The earth is rotating very quickly. If you jump you fall straight down and don’t feel any rotation. If the ship were extremely large then you would not notice any difference between it and earth. However, if the ship is small, then near the center of the ship is rotating slowly and the outer edge of the ship is rotating faster. So for a ship that is not incredibly large then yes, you would get rotational effects as you go toward or away from the center of rotation. This is called the Coriolis Effect and actually does happen on earth too, we just generally don’t notice it because earth is so big.

The Coriolis effect is why hurricanes always spin counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. Since hurricanes are so large, the effect of the changing rotational speed away from the equator is not negligible. In a smaller ship, you would notice that same Coriolis effect just walking around. The only reason you don’t notice that effect on earth is because you, unlike a hurricane, are tiny compared to the earth so there is not any significant change is rotational speed as you walk around.