45 - "The Earth is "falling" around the Sun just like a satellite (including the Moon) is falling around the Earth."
Good simple explanation. Now why? What causes the thing to fall?
All the simple gravity explanations I remember they seem to use 'centrifical force' and a rope, and a bucket (or whatever), and it makes no sense to me.
Imagine firing a super-range cannon. The cannonball doesn't travel in a perfectly straight line tangential to the Earth; instead, it "hugs" the curve of the Earth... e.g., if you fire it 6 feet above ground, the cannonball stays 6 feet above ground instead of travelling in a line tangent to the Earth.
Fire it hard enough, and it'll go around the Earth completely before falling down. Fire it even harder, and you'll have a satellite that'll stay up a really long time before it gradually gets lower & slower until it finally crashes into the ground.
It's the exact same way with the planets, they're giant cannonball that are revolving around the Sun, and indeed, they're slowly losing energy and "falling" into the Sun. Hope that helps a bit.
The centrifugal force you are speaking of simply has the same mathematics of a planet in orbit. Gravity would be the same force as the string.
A very confusing subject.