Expansion with constant mass In 1834, during the
second voyage of HMS Beagle,
Charles Darwin investigated stepped plains featuring
raised beaches in
Patagonia which indicated to him that a huge area of South America had been "uplifted to its present height by a succession of elevations which acted over the whole of this space with nearly an equal force". While his mentor
Charles Lyell had suggested forces acting near the crust on smaller areas, Darwin hypothesized that uplift at this continental scale required "the gradual expansion of some central mass" [of the Earth] "acting by intervals on the outer crust" with the "elevations being concentric with form of globe (or certainly nearly so)". In 1835 he extended this concept to include the
Andes Mountains as part of a curved enlargement of the Earth's crust due to "the action of one connected force". Not long afterwards, he abandoned this idea and proposed that as the mountains rose, the ocean floor subsided, explaining
the formation of coral reefs. In 1889 and 1909
Roberto Mantovani published a hypothesis of Earth expansion and continental drift. He assumed that a closed continent covered the entire surface of a smaller Earth.
Thermal expansion caused
volcanic activity, which broke the land mass into smaller continents. These continents drifted away from each other because of further expansion at the rip-zones, where oceans currently lie. Although
Alfred Wegener noticed some similarities to his own hypothesis of
continental drift, he did not mention Earth expansion as the cause of drift in Mantovani's hypothesis. A compromise between Earth-expansion and Earth-contraction is the "theory of thermal cycles" by Irish physicist
John Joly. He assumed that heat flow from
radioactive decay inside Earth surpasses the cooling of Earth's exterior. Together with British geologist
Arthur Holmes, Joly proposed a hypothesis in which Earth loses its heat by cyclic periods of expansion. By their hypothesis, expansion caused cracks and
joints in Earth's interior that could fill with
magma. This was succeeded by a cooling phase, where the magma would freeze and become solid rock again, causing Earth to shrink.
Mass addition In 1888
Ivan Osipovich Yarkovsky suggested that some sort of
aether is absorbed within Earth and transformed into new chemical elements, forcing the celestial bodies to expand. This was associated with his
mechanical explanation of gravitation. Also the theses of
Ott Christoph Hilgenberg (1933, 1974) were based on absorption and transformation of aether-energy into normal matter. After initially endorsing the idea of continental drift, Australian geologist
Samuel Warren Carey advocated expansion from the 1950s (before the idea of plate tectonics was generally accepted) to his death, alleging that
subduction and
other events could not balance the
sea-floor spreading at
oceanic ridges, and describing yet unresolved paradoxes that continue to plague plate tectonics. Starting in 1956, he proposed some sort of mass increase in the planets and said that a final solution to the problem is only possible by
cosmological processes associated with the
expansion of the universe.
Bruce Heezen initially interpreted his work on the mid-Atlantic ridge as confirming S. Warren Carey's Expanding Earth Theory, but later ended his endorsement, finally convinced by the data and analysis of his assistant,
Marie Tharp. The remaining proponents after the 1970s, like the Australian geologist James Maxlow, are mainly inspired by Carey's ideas. To date no scientific mechanism of action has been proposed for this addition of new mass. Although the earth is constantly acquiring mass through accumulation of rocks and dust from space such accretion, however, is only a minuscule fraction of the mass increase required by the growing earth hypothesis.
Decrease of the gravitational constant Paul Dirac suggested in 1938 that the universal
gravitational constant had
decreased during the billions of years of its existence. This caused German physicist
Pascual Jordan to propose in 1964, a modification of the theory of
general relativity, that all planets slowly expand. This explanation is considered a viable hypothesis within the context of physics. Measurements of a possible variation of the gravitational constant showed an upper limit for a relative change of per year, excluding Jordan's idea.
Formation from a gas giant According to the hypothesis of
J. Marvin Herndon (2005, 2013) the Earth originated in its
protoplanetary stage from a
Jupiter-like
gas giant. During the development phases of the young
Sun, which resembled those of a
T Tauri star, the dense atmosphere of the gas giant was stripped off by infrared eruptions from the sun. The remnant was a rocky planet. Due to the loss of pressure from its atmosphere it would have begun a progressive decompression. Herndon regards the energy released due to the lack of compression as a primary energy source for geotectonic activity, to which some energy from radioactive decomposition processes was added. He terms the resulting changes in the course of
Earth's history by the name of his theory
Whole-Earth Decompression Dynamics. He considered
seafloor spreading at
divergent plate boundaries as an effect of it. In his opinion
mantle convection as used as a concept in the theory of
plate tectonics is physically impossible. His theory includes the effect of
solar wind (
geomagnetic storms) as cause for the reversals of the
Earth magnetic field. The question of mass increase is not addressed.
Other A handful of studies consider obituary of the expanding Earth theory as a whole must be considered premature at this time, and point to recent space geodetic and gravimetric studies as evidence. ==Main arguments against Earth expansion ==