To move an object against gravity requires the expenditure of energy to do work. Therefore the gravitational potential energy of that object must be negative, because energy is not created or destroyed. QED. Zero and negative levels are required in maths. Maths is simply a description of reality.

Does anyone else have any idea what this simpering madman is drivelling on about?

All your base are belong to us.
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Why am I an atheist and not an agnostic? Sitting on the fence only gives you a sore arse.