(Bob Kuykendall) wrote in message . com...
Earlier, "bsquared" wrote:

I hate to disagree with you, but sailplanes
are "powered" by gravity, not the sun.

Well, we'll just have to agree to disagree, then. To say that gliders
are powered by gravity would have to involve a definition of power
with which I am not familiar.

Bob K.

Potential energy is stored in a gravitational field by raising a mass
to an altitude. This is analogous to storing energy in a capacitor
using a voltage (height) to create an electric (gravity) field. The
heavier the mass the greater the energy (which is why we use ballast).

But the storage mechanism is not the source of the power used to lift
the mass to altitude. This (usually) comes from the Sun. I say usually
because I have used nuclear powered thermals.


Tom Seim
Richland, WA