[Tango-L] Definition of Axis (was: On Axis, Off Axis)

[Zoltan Hidvegi]

Evan Wallace wrote:
> First of all, an "axis" is not a property of an object in the same way that
> mass or color or shape is. An axis is an imaginary construct used to

Actually, if you really want to be technical, each rigid body has at
least three mutually perpendicular principal axes, which *is* a
property of the object.  A rigid body will rotate freely around its
principal axes, but you have to use force to make something rotate
around other axes.  See
e.g. http://en.wikipedia.org/wiki/Moment_of_inertia or any physics
book for some more details.

Of course dancers are not rigid, a dancer's principal axes changes as
she moves her body, but still at every moment you can calculate the
principal axes of an individual dancer or a couple.  To allow easy
rotation, this principal axes must go through the point of contact
between the floor and the weight-bearing foot.  I think that would be
the meaning of the phrase, stay on your own axes.

-Zoltan