# Coriolis force and liquid on a rotating space station?

On a rotating wheel space station crewed by humans with sea-level conditions (temperature above the freezing point), if liquid was spilled on the floor am I correct in understanding that the Coriolis Effect would cause the liquid to appear to move in the direction opposite of the direction of spin of the station?

Would the speed of the liquids apparent motion be slower at a point halfway between the center of the station and the outer ring?

• It depends on atmosphere as well. Is there some artificial atmosphere with a normal pressure and at room temperature or just a vacuum? Nov 7 '20 at 17:08
• Wouldn't a vacuum preclude a liquid state? How would atmospheric pressure effect the movement of the liquid? Nov 7 '20 at 18:22
• You did not answer my question. Is there some artificial atmosphere at room temperature? Nov 7 '20 at 19:08
• Lets assume the conditions on the International Space Station: cabin pressure nominal range: T = 14.2 to 14.9 psi, oxygen and nitrogen distribution: P = 93 - 120 psia, cabin Temperature nominal range: T = 65 to 80˚F, about 60% relative humidity space.stackexchange.com/q/2539 Nov 7 '20 at 19:25
• @AlexTrounev Do be aware that Bob516 has developed a theory of motion that is incompatible with the standard theory. According to this new theory an amount of water, located on the floor, initially at rest with respect to the floor, will start to lag behind the rotating wheel space station. According to Bob516 this will happen because the water is not rigidly connected to the floor. See the comments by Bob516 to my answer. Nov 7 '20 at 19:34

Each revolution of the station would make any object in it have a rotational distance of 2pi*r where r is radius of the object from the center of rotation. So the outer edge of the cylinder would have twice the linear speed of anything inside at half its radius. Increasing the object's radius inside the cylinder would make it appear, in the cylinder's frame of reference, to move anti spin ward until, or if, some force caused its linear speed to match the linear speed of its greater radius. So as long as your liquid moved "downward" you would notice a Coriolis force.

• So if the fluid was on the floor, and moving, it wouldn't be called the Coriolis Effect? If that is correct what would it be called that is causing the fluid to appear to move across the floor? Nov 7 '20 at 4:38
• It would be the Coriolis force causing the initial difference in speed. The Coriolis effect pertains to the perceptions of the human body. see; en.wikipedia.org/wiki/Coriolis_effect_(perception) also see; en.wikipedia.org/wiki/Coriolis_force Nov 7 '20 at 4:56

It is referred to as Coriolis effect when there is velocity towards or away from the axis of rotation.

(However, in many cases a generalized concept is used, this generalized concept also looks at the effect of velocity in tangential direction. I will get to that at the end of this answer.)

On the rotating wheel space station:
Water flowing out of a tap will not be seen to fall straight down towards the sink. Instead the water will be seen to lag behind. The amount of lagging behind is not correlated with the distance to the central axis of rotation, so you cannot infer your distance to the central axis from observing the amount of lagging behind.

However, the case of water in motion is not what you are asking about.

You are asking about water that is stationary in a pool on the floor.

I'm referring to that pool of water as stationary because that pool of water is co-rotating with the space station. For a pool of water on the floor there is nothing to make it move with respect to the floor.

Compare the Earth.
The water on the Earth is co-rotating with the Earth. As seen from the south pole the Earth is rotating clockwise, and the water on the Earth isn't lagging behind.

About a generalized concept of Coriolis force.
Imagine a pool of water on that rotating wheel space station, large enough for a toy boat, the toy boat is motorized. Let the boat be cruising in a direction so that it is moving faster than the space station. Then the boat is circumnavigating the central axis faster than the space station itself. Faster circular motion requires a larger centripetal force. So: when the boat is circumnavigating the central axis faster than the space station itself the boat will be a bit deeper in the water, so that the buoyancy force is larger. Conversely, if the boat is cruising in the opposite direction then it is circumnavigating the central axis slower than the space station. By cruising fast enough the boat can completely negate the angular velocity of the space station. The water of the pool will then lift the boat completely out of the water. When the boat is no longer circumnavigating the central axis then there is no longer a requirement for a centripetal force.

• I thought only an object that has some physical connection to the structure of the station would be co-rotating. What is the difference between a ball dropped from the hand of a person standing inside the station and a liquid resting on the surface of the station, not in a container? In neither case is there no connection between the object in question and the station itself. Nov 7 '20 at 15:35
• @Bob516 In my answer I gave the comparison with the oceans of the Earth. More specific: the body of water surrounding Antarctica: the Southern Ocean. The water of the Southern Ocean is free to flow all the way around; it never meets any obstruction. According to your theory of physics the water of the Southern Ocean will lag behind the Earth's rotation. In actual fact it doesn't. That body of water is co-rotating with the Earth. I recommend you think about that. Nov 7 '20 at 15:53
• I did think about that. The water in the ocean is co-rotating because Earth's gravity has an equal effect on it as it has on any mass in the earth system. What force is keeping a puddle of water in place inside the station, co-rotating, since it doesn't have a physical connection to anything in the station? Yes, inertia will keep the water moving in one direction for a time. Since the station turns about its axis a person standing on the floor will move in a different direction. Wouldn't it cause the water to not remain in the same spot on the floor as the person? Nov 7 '20 at 22:42