Can I Spin in Zero-G Without Moving Laterally?

[Dr Lots-o'watts]

It's an imaginary point.

I don't understand where is this imaginary point.

 

[DaveC426913]

In a real world situation, you will never be at 100% arms length from the center of mass. It's an imaginary point. A human body as well does not have uniform density. In the REAL world, you'll always have translational movement. You'd need perfect axis of rotation, perfect transfer of momentum...etc.

I don't think so.

1] It is possible to have the propulsion at 100% distance (within the margin of error of the experiment).
2] Human body's varying density is irrelevant; it can be treated as a point at the CoM.

Basically, you can reduce the system to a point mass, with a massless arm extending out r, and a force applied to its tip (radius r).

Even in this perfect, ideal situation, if the reaction mass goes left, then to some extent the mass goes right, even while spinning.

Watch this video starting at 14:49:
http://www.youtube.com/watch?v=EOy1N...eature=channel