Hollow Earth: The Long and Curious History of Imagining Strange Lands, Fantastical Creatures, Advanced Civilizatio Read Online Free PDF Page B

Poets when it makes for my purpose.”
    One way or another, there is light down there sufficient to support life.
    Somewhere along the way in this argument—after many readings I still find it difficult to pinpoint—truly warming to his subject, he raises the number of these interior spheres from one to three. He now refers the reader to a diagram appended to the end of the paper. Describing it, he says, “The Earth is represented by the outward Circle, and the three inward Circles are made nearly proportionable to the Magnitudes of the Planets Venus, Mars and Mercury, all of which may be included within this Globe of Earth, and all the Arches sufficiently strong to bear their weight.”
    There it is. Three independently moving spheres inside, well-lit and capable of supporting life. The paper concludes on a brave note, though tinged with a defensive twitch or two:
    Thus I have shewed a possibility of a much more ample Creation, than has hitherto been imagined; and if this Seem strange to those that are unacquainted with the Magnetical System, it is hoped that all such will endeavor first to inform themselves of the Matter of Fact and then try if they can find out a more simple Hypothesis, at least a less absurd, even in their own Opinions. And whereas I have adventured to make these Subterraneous Orbs capable of being inhabited, ’twas done designedly for the sake of those who will be apt to ask cui bono [What is the good of it?], and with whom Arguments drawn from Final Causes prevail much. If this short Essay shall find a kind acceptance, I shall be encouraged to enquire farther, and to polish this rough Draft of a Notion till hitherto not so much as started in the World, and of which we could have no Intimation from any other of the Phenomena of Nature.
     
    It should be noted that except for the life and light he posited down there, for which science fiction writers have been thanking him ever since, but about which, per the above, he obviously had certain reservations—his ideas regarding the causes of the earth’s magnetism and the complicated shifts in the magnetic poles were quite prescient and not far in principle from current thinking. According to recent Halley biographer Alan Cook, “he showed an understanding of the essential structure of the Earth’s magnetisation.” The earth does consist of separate spheres of a sort: the outer crust; the mantle, which accounts for two-thirds of the planet’s mass; a dense liquid layer of magma consisting chiefly of molten iron that’s about half the earth’s radius in extent; and a solid inner core inside that. The layer of molten metal is circulating—like Halley’s internal Sphere—which creates electrical currents, which in turn create magnetic fields. The earth can be thought of as a great electromagnet. Even today all of this isn’t entirely understood. But Halley was closer to being on the right track than it might seem at first blush.
     
     
    In 1716, England was treated to a spectacular aurora borealis display—another phenomenon little understood at the time, and not completely so now. This came at the end of the “maunder minimum” in Europe and England, a period of low sunspot activity lasting from 1645 to 1715 that coincided with a near absence of the northern lights. Halley observed the display and wrote a paper offering an explanation for it that involved his theory of the hollow earth. He rightly supposed that the earth’s magnetic field played a part in creating the aurora. Alan Cook comments that “his analysis of the structure of aurorae and their correspondence with the Earth’s magnetic field remains impressive after nearly three hundred years.” Halley further speculated—incorrectly—that the source of the particles reacting to the magnetic field to create the aurora might be the “medium” between the shell and the first internal sphere leaking out into the atmosphere. It might tend to leak more at the poles because, as Cook