# ONiel world gravity?

1. Sep 24, 2015

### darthsasquatch

Im doing some research on ONiel cylinder worlds and the use of rotation to imitate gravity. My question is, if you jump in a ONiel cylinder (full of air) is it just the rotating air which exerts force to bring you back to the inner surface? Expecting the cylinder has too little mass to create earth like gravity.

2. Sep 25, 2015

### 256bits

Air, or vacuum, doesn't matter. You would "fall" back to the surface in either case. With air though there may be some air currents, or wind, if you prefer, but any such effect upon the imitation gravity would not be taking that into account, just as much one does not consider the minimal effects of air currents on earth.

3. Sep 25, 2015

### darthsasquatch

Thank you for responding. Im unclear of the mechanics, so just by placing a rotating cylinder around an object floating in space, that object would be attracted to the surface? Where does the force come from?

4. Sep 25, 2015

### 256bits

No, that will not work.

Basically, all objects on the cylinder surface travel at the same velocity. If you jump, that velocity stays with you. Since there is no force acting upon you, you will travel in a straight line( assuming the jump upwards is not too great in strength ) and then bump back into the cylinder. It will feel as if the cylinder has attracted you to it.

5. Sep 25, 2015

### darthsasquatch

Right, it ocurred to me after my relpy that just jumping in the Y does not change the X the surface was giving you. So if a person could momentarly negate the cylinders spin, say by jumping against its rotation, they could "hover" over the rotating surface?

6. Sep 25, 2015

### A.T.

Yes, running against the spin will reduce the apparent gravity, and when it's down to zero you can just hover (ignoring the effect of air).

7. Sep 25, 2015

### darthsasquatch

Great! Thank you for clearing this up for me. Now i can plug more numbers into a calculator i found for these type of stations, and figure out how feasable such an attempt would be.