World Science Scholars

2.7 Gravitational Field Energy

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    • Have you ever previously heard that the energy of a gravitational field can be negative? Does it surprise you? Are you convinced by the derivation given in the lecture?

    • I have heard this before and still find it surprising, but am willing to accept it if it allows consistency with theories and calculations. But I dont find the demonstration totally convincing. Allan says there is no gravitational field inside the sphere because the force from around the sphere cancels out. But isnt this only true at the centre? Away from the centre isnt there a net force because such a point is closer to one side of the sphere? So if there is a field there before the collapse, as the field contracts it isnt the case that a field appears where there was no field before.Also what happens if the sphere collapses without generating power. The same region of supposedly no gravitational field will after collapse have the same field with out doing any work. All very interesting!

    • Very interesting, I have heard this before and enjoy the concept.

    • Yes, persuasive demonstration from principle of conservation of energy in closed system.

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