> What's interesting is that the power available from solar fusion is of a similar order of magnitude to that available from gravitational contraction.
No, it isn't; fusion provides much more energy per unit mass than gravitational contraction would for the Sun. As I calculated, gravitational contraction falling in from infinity to the current radius of the Sun provides about 2 x 10^11 Joules per kilogram. Fusion provides about 5 x 10^14 Joules per kilogram (the exact number depends on the particular fusion reaction).
No, it isn't; fusion provides much more energy per unit mass than gravitational contraction would for the Sun. As I calculated, gravitational contraction falling in from infinity to the current radius of the Sun provides about 2 x 10^11 Joules per kilogram. Fusion provides about 5 x 10^14 Joules per kilogram (the exact number depends on the particular fusion reaction).