The balancer could be human or robot.

The beam is long, sturdy and unshakeable, with infinitessimal width and height. (The balancer gets magic shoes to avoid getting sliced and have sufficient friction with the beam)

"Maintain balance" means keeping one's center of mass higher than the beam, even in spite of small external perturbations.

Things that aren't in the spirit of "balancing" (not exhaustive):

• Expelling matter irrecoverably from the balancing system doesn't count. (So throwing objects is disallowed unless the balancer also catches them)

• Stuff that wouldn't work in a vacuum doesn't count. (So helium balloons or leaf-blowers wouldn't help.)

• Other system-boundary violating things that I haven't thought of

Resolves to whatever I'm convinced of in 1 month (before August 19). There will also be at least M100 managrammed to the most-hearted comment.

I won't bet in this market.