Hoagland cites hyperdimensional physics as the cause of the fluffiness--an input of energy to the interior of the planet causing heating and thermal expansion. This is not one of the commonly accepted explanations.Heh, y'think? Damned narrow-minded Isis-worshipping jackbooted NASA lackeys! ;') Hyperdimensional physics are also responsible for ice cubes floating, water boiling at room temperature when the air is pumped out, and uh, and uh, socks disappearing out of the dryer...
Hyperdimensional physics might be interesting from an archaeological standpoint. It is mainly what physics was before Michelson-Morley and the Theory of Relativity. There were many lines of theoretical development such as the vortex theory of gravity let go abruptly in 1895-1905 since the new approaches were much easier to work with mathematically. However, these lines of theoretical development are still available and a few scientists continue work on them and Hoagland is assembling some of the current results. While Hoagland is more impressed with some of the geometrical results than is warranted, still the ideas should not be completely dismissed just because the math is not as well developed as tensors and string theory has been more productive so far.