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The term itself, however, was coined by Jack Williamson in a science-fiction short story ("Collision Orbit") published in 1942 in Astounding Science Fiction, [6] [7] [4]: 235 [8] although the concept of terraforming in popular culture predates this work; for example, the idea of turning the Moon into a habitable environment with atmosphere was ...
The internal structure of Earth are the layers of the Earth, excluding its atmosphere and hydrosphere. The structure consists of an outer silicate solid crust , a highly viscous asthenosphere , and solid mantle , a liquid outer core whose flow generates the Earth's magnetic field , and a solid inner core .
Of all Earth’s layers, the inner core is the most remote and mysterious. This solid sphere of iron and nickel is about 70% the size of the moon, with a radius of approximately 759 miles (1,221 ...
Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 20% of Earth's radius or 70% of the Moon's radius. [1] [2] There are no samples of the core accessible for direct measurement, as there are for Earth's mantle. [3]
Gravity at different internal layers of Earth (1 = continental crust, 2 = oceanic crust, 3 = upper mantle, 4 = lower mantle, 5+6 = core, A = crust-mantle boundary) Earth's radial density distribution according to the Preliminary Reference Earth Model (PREM). [13] Earth's gravity according to the Preliminary Reference Earth Model (PREM). [13]
The most famous example of subterranean fiction is Jules Verne's 1864 science-fiction novel Journey to the Center of the Earth, which has been adapted many times as a feature film and for television. The novel is not an example of Hollow Earth, as his characters actually descend only 87 miles beneath the surface, where they find an underground ...
For example, the Earth's mean specific gravity (5.515) is far higher than the typical specific gravity of rocks at the surface (2.7–3.3), implying that the deeper material is denser. This is also implied by its low moment of inertia ( 0.33 M R 2 , compared to 0.4 M R 2 for a sphere of constant density).
Subterranean fiction is a subgenre of speculative fiction, science fiction, or fantasy which focuses on fictional underground settings, sometimes at the center of the Earth or otherwise deep below the surface. The genre is based on, and has in turn influenced, the Hollow Earth theory.