|
The Hollow Moon hypothesis proposes that Earth's Moon is either wholly hollow or otherwise contains a substantial interior space. No scientific evidence exists to support the idea; seismic observations and other data collected since spacecraft began to orbit or land on the Moon indicate that it has a thin crust, extensive mantle and small, dense core, although overall it is much less dense than Earth. The Hollow Moon concept is similar to the better-known Hollow Earth hypothesis, and was a recurring plot device in pre-spaceflight science fiction. Hollow Moon adherents can be broadly grouped in two major camps, both of which are considered by the scientific community to be unsupported by evidence: *The Moon's formation process produced a hollow sphere through natural means. Details vary widely; the proposed mechanism is usually an undefined or pseudoscientific factor in accretion-disk dynamics. *The Moon is an artifact (the "Spaceship Moon Theory"). This often corresponds with beliefs in UFOs or ancient astronauts. ==Scientific perspective== A 2011 NASA press release, and a single 1976 scientific study on the internal structure of the Moon speculate on the possibility of a solid internal structure with a thin crust, an extensive mantle and a small denser core.〔(Measurements of the lunar induced magnetic moment in the geomagnetic tail: Evidence for a lunar core? )〕〔(BASA Research: Moon has Earth-like core )〕 This is based on: #Seismic observations. Besides Earth, the Moon is the only planetary body with a seismic observation network in place. Analysis of lunar seismic data have helped constrain the thickness of the crust (~45 km) and mantle, as well as the core radius (~350 km). #Moment of inertia parameters. For the Moon, moment of inertia parameters have demonstrated that the core is ~1.4% of the total mass.〔 One such parameter, the normalized polar moment of inertia, is 0.393 ± 0.001.〔〔(NASA Moon Fact Sheet )〕 This is very close to the value for a solid object with radially constant density, which would be 0.4 (for comparison, Earth's value is 0.33). The normalized polar moment of inertia for a hollow Moon would have a higher value, closer to 0.67. In other words, the moment of inertia parameters indicate that the core of the Moon is both dense and small, with the rest of the Moon consisting of material with nearly-constant density. #Fine-scale variation (e.g., variation along the orbit of the Lunar Prospector orbiter) of the lunar gravitational field, which is consistent with geologic processes involving a crust, mantle, and core. The large-scale gravitational field of the Moon, however, is unaffected by the internal distribution of mass if the internal density is assumed to vary only radially. For example, had the Moon been replaced with a point object of identical mass, the current gravitational field would continue to exist at distances greater than the ~1700 km lunar radius. This can be derived directly for a spherically symmetric Moon by applying the integral form of Gauss's law. Therefore, the large-scale gravitational field of the Moon does not convey any information about the internal radial distribution of mass. Hollow Moon proponents would, however, have to account for the incredible density of the Moon's crust if it were in fact hollow. As gravitational pull is determined by mass, a hollow moon would require an inordinately dense crust to achieve observed gravitational values. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hollow Moon」の詳細全文を読む スポンサード リンク
|