Can't you side-step at least some of those directionality issues, Orac, by explaining them in terms of General Relativity?
No it gets worse under GR because gravity is basically seen as things running down the gradient ... 1 sec let me see if I can find a visualization I like ... there ...
(
http://web.mac.com/limuti/DWT/23_Gravity_Visualized.html) or another way (
http://www.adamtoons.de/physics/gravitation.swf)
So basically its like a soft foam matress put two heavy balls on it they displace the foam and want to run together ... married couples in bed should be very used to te effect :-)
So now you are left with the sticky problem where Bill ends up what the hell is stopping it all just collapsing. Why don't all the planets just collapse into one big ball.
You can show the effect even in newtonian simulator just use a one sided gravity equation. (
http://www.myphysicslab.com/beta/Inverse-square-gravity.html) Take the elasticity to zero so they don't bounce and see what happens.
So this is very much Bills problem as I see it potential energy at its most basic in gravity under our physics laws wants to drag stuff together .... what stops it?
See at it's heart the really big problem is a really simple question and I guess what I am saying is Bill is simply reworking the known bit but he still does not touch on answering the opposing ... that is all that potential energy is massive ... why doesnt it just collapse the universe in a blinding flash.
