Nice article Ella. But I have one particular question that I have yet to have answered. The ball on a sheet model only works -BECAUSE - of gravity, so it can't actually explain gravity. Why would something roll or slide down a slope if there wasn't gravity? So using indents in a sheet to explain gravity is actually circular logic - that model wouldn't work in space under zero gravity conditions. I understand that the earth is actually moving in a straight line through curved space-time - hence its apparent elliptical orbit. BUT whilst this might explain how a straight line becomes a circle, it doesn't explain the motion. This action at a distance seems to have no explanation. Why would an object move through warped space-time by itself without propulsion - an effect we call gravitational attraction? A ball placed on a large flat picture of converging lines does not roll by itself towards the conergence of those lines. I have heard some physicists invoke 'force particles' to explain gravity and then I suspect they are grasping at straws since no one seems to be able to define a 'force particle'. Any thoughts?