How to write a documentary for TV

Hi
I am looking at writing a documentary on `What may cause Gravity' ...I am wondering if anyone can help with a reference book etc....is it similar to writing a film script or is it massively different.
Regards Andrew

I am not a scientist, nor majored in it, but wouldn't that project be an educational film instead of a documentary?

Andrew- Gravity is the result of mass. The larger the mass, the stronger the force. The force pulls things towards the mass. Big things like planets and stars have a lot of gravity. Little things have gravitational force too, but it is just harder to detect it. Since it is one of nature's forces, there really is no answer to the "cause." Some say God is behind the forces of the universe like gravity, or an even stronger force- that which holds molecules and atoms together. Others say it is simply nature. As far as a documentary or educational film- you might just want to show the force of gravity in all its forms. As to what is the cause, don't attempt it. It's like you are a fish, and you want to do a film about water. You could show how you move in it, how you breath it through your gills, how it is everywhere, and surrounds everything, how it corrodes metal and decays wood. But it would be hopeless to show where it comes from, because you'd need to show the rain, and the trees in the jungle, and the rivers, and the snow. But poor you - you're only a fish. So do the film about water and your life in it. Start your film by showing people playing with a ball, and how much fun gravity can be. Then cut to the planets, and show how much fun it is to live on one that stays nicely in it's orbit, just the right distance from the sun, going at just the right speed to stay in its orbit, due to gravity. Then show how the people don't fall off this planet. Gravity is so much fun. You get the idea.