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Deep-Earth Timetable of Ideas, Measures, Deductions, and Theories

© 2003 J. Marvin Herndon
W. Gilbert (1600)   Loadstone and magnetic bodies and on the great magnet the earth: (in Latin), London, (1600) Peter Short, 240 p.
More than a thousand years ago, the Chinese developed the compass for navigation. The instrument used a lodestone, a natural magnetic stone made of black iron oxide. Sir William Gilbert, the personal physician to Queen Elizabeth I, set out to show that the behavior of the compass was not magic. From experiments, Gilbert showed that the compass points to the North because the whole Earth acts as if it is a giant magnet (lodestone).
K. F. Gauss (1838) Allgemeine Theorie des Erdmagnetismus: Resultate aus den Beobachtungen des magnetischen Vereins in Jahre  1838, Leipzig, 73 p.
Karl Fredrik Gauss, a renowned mathematician, confirmed Gilbert’s hypothesis that the Earth acts like a magnet and showed that the magnetic force that attracts the compass needle originates deep inside the Earth, at or near the center of the Earth.
H. Cavendish (1798) Philosophical Transactions of the Royal Society of London, v. 88, (1798) p. 469-474.
Henry Cavendish measured the density of the Earth, finding it  to be 5.48 times as dense as water. The modern value is 5.5.
E. Wiechert (1898) Verhandlungen Gesellschaft Deutscher Naturforscher und Ärtze, v. 68, (1896) p. 42-43.
Realizing that Cavendish’s measured density of the Earth meant that the Earth as a whole is more dense than rock, Emil Wiechert postulated that the Earth has a core similar to iron meteorites as a way to explain the Earth’s greater density. Wiechert referred to the shell of rock surrounding the core as the Mantel, a German word, meaning cloak. Later, the shell of rock surrounding the core became known as the mantle.
R. D. Oldham (1906) Quart. J. Geol. Soc. Lond., v. 62, (1906) p. 456
When an earthquake occurs, it produces powerful vibrations, waves that are capable of passing through the interior of the Earth. In 132 A.D. the Chinese scientist Chang Heng invented the first devise, called a dragon jar, to detect earthquakes. In 1880, John Milne invented the first modern “pendulum” seismograph. In 1906, Richard Dixon Oldham deduced that the Earth has a core from seismograph tracings which showed that compression earthquake waves passing through the deep interior of the Earth travel at a slower rate than through the more shallow regions.
A. Mohorovičić (1909) Jb. Met. Obs. Zagreb, v. 9, (1909) p. 1-63.
Andrija Mohorovičić discovered, from the speed of travel of earthquake waves, the boundary between the crust and the mantle that occurs at a depth of about 35 km (22 miles) beneath the continents and a depth of about 10 km (6 miles) beneath the seafloor.
B. Gutenberg (1913) Physikalische Zeitschrift, v. 14, (1913) p. 1227-1218.
Beno Gutenberg made the first accurate determination the radius of the core to be 2900 km, a value close to the modern value of 3482 km (2164 mi). The mantle extends from that radius to a radius of about 6361 km (3953 mi) and is capped by the crust for an Earth radius of 6371 km (3959 mi).
B. Gutenberg (1926) Zeitschrift Geophysik, v. 2, (1926) p. 24-29.
Compression earthquake waves vibrate in the direction of travel; shear earthquake waves vibrate perpendicular to the direction of travel. Fluids do not support shear waves for the same reason that a liquid cannot be torn. Beno Gutenberg deduced that the Earth’s core is fluid due to its failure to support shear earthquake waves.
I. Lehmann (1936) Publication Bureau Central Seismologique International, Series A, v. 14, (1936) p.3.
Earthquake waves change speed and direction when entering and leaving the Earth’s core. Consequently, there is a region, a so-called shadow zone, where earthquake waves should not be detectable, if, as was thought at the time, the Earth consists simply of a mantle and a core. But earthquake waves were in fact detected in the shadow zone. In 1936, Inge Lehmann discovered the inner core by correctly deducing that the shadow-zone waves were reflections from a small inner core at the center of the Earth within the Earth’s fluid core. The radius of the inner core is 1221 km (759 mi).
W. M. Elsasser (1939) Physical Review, v. 55, (1939) p. 489-498.
Magnets lose their magnetism when heated. The Earth cannot have a permanent magnet in its core at the temperatures at which the iron alloy main core is molten; there must be some process or mechanism that produces Earth’s magnetism. William Elsasser proposed a dynamo theory to explain the Earth’s magnetism that was based on the 1919 dynamo theory of J. Larmor to explain magnetic field of the Sun. In dynamo theory, swirling, convecting molten iron combines with the Earth’s rotation to generate a magnetic field. The energy source required by the dynamo was assumed by Elsasser to be energy from natural radioactive decay.
F. Birch (1940) American Journal of Science, v. 238, (1940) p. 192-211.
Francis Birch thought (erroneously, because data to the contrary had not yet been discovered) that nickel and iron were always alloyed together in meteorites. He also knew that elements heavier than iron and nickel, if combined together, could not make a mass as great as the inner core. He therefore deduced the composition of the inner core as being partially crystallized nickel-iron metal, an intermediate point in the process of the solidification of the Earth’s fluid core.
W. B. Clarke, M. A. Beg, and H. Craig (1969) Earth and Planetary Science Letters, v. 6, (1969) p. 213-220.
Clarke et al. measured helium coming from deep within the Earth and attributed its origin to a mixture of trapped primordial light-helium, 3He, and heavy-helium, 4He, from the natural radioactive decay of uranium and thorium. For the next three decades, geophysicists were unaware of a process or mechanism deep within the Earth that could produce the light-helium, 3He.
J. M. Herndon (1979) Proceedings of the Royal Society of London, Series A, v. 368, (1979) p. 495-500.
On the basis of data discovered in the 1960’s, J. Marvin Herndon deduced the composition of the inner core as being nickel silicide, not partially crystallized nickel-iron metal as proposed by Francis Birch in 1940. This means that the deep interior is like an enstatite chondrite meteorite, rather than an ordinary chondrite meteorite as presumed by Birch. The principal implication is that the Earth’s core contains radioactive elements, including uranium, which would otherwise not have been expected.
J. M. Herndon (1980) Proceedings of the Royal Society of London, Series A, v. 372, (1980) p. 149-155.
By fundamental ratios of mass, J. Marvin Herndon showed that the core and lower mantle of the Earth are chemically analogous to the two components of the Abee enstatite chondrite. This provides evidence that the deep interior of the Earth is indeed like an enstatite chondrite meteorite and it means that one can estimate the abundances of the elements in the core and lower mantle from measured abundances in corresponding parts of the Abee meteorite.
J. M. Herndon (1993)  J. M. Herndon (1994) Journal of Geomagnetism and Geoelectricity, v. 45, (1993) p. 423-437.     Proceedings of the Royal Society of London, Series A, v. 445, (1994) p. 453-461.
With knowledge of the ancient remains of natural nuclear reactors discovered in Africa in 1972 and with an understanding that the Earth’s core contains uranium, J. Marvin Herndon used Fermi’s nuclear reactor theory to demonstrate the feasibility of a natural nuclear fission reactor within the inner core at the center of the Earth. A nuclear reactor is capable of producing much more energy than the radioactive decay of uranium. A natural nuclear reactor at the center of the Earth can provide energy to power the geomagnetic field over geologic time. But unlike other energy sources, which might change only gradually, a deep-Earth nuclear reactor is capable of variable energy output including stopping (because of fission product accumulation) and re-starting again (as the light fission products float radially outward). Variable deep-Earth energy production may have important, not yet appreciated, implications on planetary change and global warming.
J. E. Vidale and H. M. Benz (1993) Nature London, v. 361, (1993) p. 529-530.
Vidale and Benz deduced islands of matter at the core-mantle boundary from seismic data. Although only a minor component within the Earth, these islands are important because they are predicted to be a consequence of the deep interior of the Earth being like an enstatite chondrite meteorite.
J. M. Herndon (1993)  J. M. Herndon (1996) Journal of Geomagnetism and Geoelectricity, v. 45, (1993) p. 423-437.     Proceedings of the National Academy of Sciences USA, v. 93, (1996) p. 646-648.

J. Marvin Herndon predicted low-density, high-temperature Earth core precipitates [CaS and MgS] floating atop the fluid core at the core-mantle boundary. These are an expected consequence of the enstatite-chondrite-like core, originally containing some calcium and some magnesium dissolved in the iron alloy. 

D. F. Hollenbach and J. M. Herndon (2001) Proceedings of the National Academy of Sciences USA, v. 98, (2001) p. 11085-11090.
Daniel F. Hollenbach and J. Marvin Herndon demonstrated, from numerical simulations made at Oak Ridge National Laboratory, that a deep-Earth nuclear fission reactor will produce both light-helium, 3He, and heavy-helium, 4He, precisely within the range of values observed from deep-source lavas. The helium found in oceanic lavas, first observed over three decades ago, is evidence that a natural, planetary-scale, nuclear reactor operates at the center of the Earth.
J. M. Herndon (2003) Proceedings of the National Academy of Sciences USA, v. 100, (2003) p. 3047-3050.
J. Marvin Herndon demonstrated, from more detailed numerical simulations made at Oak Ridge National Laboratory, that a deep-Earth nuclear fission reactor will produce sufficient helium with precisely the range of ratios as observed from deep-source oceanic lavas. Moreover, the ratio of 3He to 4He increases over the lifetime of the georeactor. The high ratios observed in Icelandic and Hawaiian basalts suggest that the end of the georeactor lifetime is approaching, perhaps within the next billion years, and presumably soon thereafter the geomagnetic field will begin its final collapse.

 

 

 

 

 

 

 

 

 

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