Subject: How do you tell left and right to an alien, revisited

I recently read the question "How do you tell left and right to an alien?" 
posted in August 1999, where you can only communicate verbally to an alien 
to explain the concept of left and right. The problem, of course, is 
complicated by the fact that we do not know how the aliens label basic 
directions (left/right, north/south, counter/clockwise, etc.) or how their 
planet rotates or which direction its magnetic poles are aligned.

In the response to this question, the alien is instructed to sit in a 
swivel chair and hold a spinning bicycle wheel such that its plane of 
rotation is parallel to the ground. This part I understand. Then the alien 
is told to orient the wheel such that the angular-momentum vector L is 
pointing in the opposite direction of gravitational acceleration (i.e., 
pointing "up") and turn the wheel over, causing the alien in the swivel 
chair to spin to the left. This is the part that baffles me. Isn't the 
direction of the angular-momentum vector defined by the right-hand rule? If 
this is the case, the direction is completely arbitrary and cannot be 
derived from fundamental physics. Then the problem still remains - How do 
you verbally explain the concept of left and right to an alien?

Re: How do you tell left and right to an alien, revisited