Sir Edmund Halley (1656-1742, Halley’s Comet) – Halley’s most controversial theory originated from his study of magnetism. Halley realized that the magnetic poles were constantly moving. He believed this could be explained by having two fixed magnetic poles (north and south) in the crust of a hollow earth, and two more inside which were moving. He envisaged hollow spheres, one inside the other, rotating at slightly different speeds. One of these inner shells would contain the other set of magnetic poles. If that shell rotated slightly slower than the outermost shell, then that might account for the apparent motion of two of the magnetic poles while the other two stood still.
Halley speculated on whether there might be life inside these shells. Since God had created “animate beings” which inhabited every part of the Earth as we know it, why should He not therefore have also caused the interior of these shells to be habited? He suggested that the atmosphere might be luminous, or the inner sides of the spheres might emit light, or there might even be small Suns inside the Earth which he referred to as: “peculiar Luminaries below, of which we have no sort of Idea.” Many of the core features of the Hollow Earth theory were born out of Halley’s speculations.
Could there be any logical reason for thinking that a planet might be hollow? The only possibility which comes to mind is that a spinning sphere might become hollow naturally. This was originally suggested to me by John Flora, who joined my Internet list. His argument is as follows: Scientists believe stars and planets formed from huge clouds of dust in space. Gravity caused them to condense. Then they started spinning and eventually became spheres. If this is the case then, like an ice skater, these stars and planets would have spun ever faster as they contracted. This would be dictated by the law of conservation of angular momentum. However, the solar system tells a different story.
It is not the smallest planets which spin the fastest, but the largest ones. The Earth rotates om 24 hours, and many of the planets smaller than it rotate even slower. Jupiter, the largest planet, which has a diameter more than ten times that of the Earth spins about its axis in a mere 10 hours. This is not what one would expect from condensed, solid planets. John pointed out that this is also true of the different types of stars. The larger ones spin faster than the smaller ones. He believes that it can be shown mathematically that a high rate of rotation would cause a spherical body to expand until it reaches a point of maximum inertial stability.
In an e-mail dated 15 Feb 1998, he explained in part,
As I said earlier, the maximum moment of inertia for a rotating sphere to spin stably is that of a hollow sphere. . .
He suggested that the planets and stars be regarded as “tornadoes in space.” He explained:
This smaller size – slower rotation, bigger size – faster rotation relationship of planets and stars rotations is exactly what you would think if the planets and stars were created hollow however!
Because, according to spherical shell dynamic theory, the planets and stars were created out of convection currents between warm and cool regions of space, swirling the particles into whirling, twirling tornadoes of particles. In the zero-gravity of space these tornadoes took on the shape of spheres with open poles, and the faster they were rotating, the larger they became! John’s logic also suggests that Hollow Planets must have Polar Holes of some kind. He pointed out that there was a point at which centrifugal force and gravity balance. Gravity, (as we shall see later, is zero at the centre of the Earth (or any hollow sphere). All mathematical exercises show that if one could suspend an object at the centre of the Earth, then it would be weightless. So when a forming planet rotates, the matter at its core will be flung away from the centre. Gravity however, increases as one moves away from the centre of a planet because there is more matter “below” it. So a point is reached whereupon gravity is stronger than the centrifugal force, and the expansion then stops. One thus ends up with a hollow spinning sphere.