Re: Spelljammer on planar walkabout

>No if what you are saying were true skydivers would have to wear
>heat-shields because they often free-fall for several miles and a
>human in free-fall reaches terminal velocity after only a few hundred
>feet.

I'm afraid I must admit ignorance on the matter of skydiving. I have
absolutely no idea when a skydiver reaches terminal velocity or whether he
heats up significantly. Since you favor the view that heat is _not_
generated--or at least not transferred to the skydiver--what do you propose
happens to the heat energy from friction?

>Also a Spelljammer would almost certainly (I can not say for certain
>because I do not have data for surface area and mass) have a terminal
>velocity well below the speed of sound and therefor would not generate
>excessive heat through friction.

I'm not certain what you mean. High air resistance would certainly mean
that you reach terminal velocity sooner, as you say, thus decreasing
kinetic energy. That just means, though, that you start using significant
amounts of heat energy sooner rather than later. Every kilogram dropping a
meter in Earth gravity generates one joule of energy, no matter _how_ fast
it's going, whether it's accelerating, or whether it's at terminal velocity
already. (This is, of course, because of the way energy is defined.)

While we're sort of on the subject, I need someone to check my logic on a
physics dilemma. Centripedal force is equal to [m*v^2/R], right? Thus, it
varies inversely with distance. Gravity varies as the inverse square of
distance, [G*m1*m2/d^2]. Double the distance, and centripedal force halves,
while the force of gravity quarters itself. Thus, an orbit would be a
delicate balance--get too far out, and you'll sail away into infinity. Too
close, and gravity overpowers centrifugal "force" and you crash into the
planet. Now, I know this can't be right, because it would make forced
orbits impossible. (That's where you get into orbit, then thrust toward the
orbited mass. It's very safe, because if you lose power you "fall" back to
the original orbit.) Thus, either my math or my physics must be wrong.
[scratches head] What am I doing wrong? Can anyone help?

						Hemlock