Astronomy

At the Earth's Core: The Geophysics of Planetary Evolution

Reciprocity XXVII, #1 (Spring, 1998), p. 9.

Very little is actually known about the Earth's interior. Actual research is limited to what is pulled up from a scant few miles of the crust, by deep mines and drilling rigs. Volcanoes provide some additional insight as to the existence of a molten plastic-like layer between the crust and mantle known as the asthenosphere. However, the bulk of data beyond this point comes from the distant echoes of earthquakes, and the seismographic machines that plot their deviations as they traverse the depths of the Earth's interior.

Gravitation and the Galaxies

Today, three centuries after Newton, gravitation is still one of the enigmas of science. "It may well be the most fundamental and least understood of the interactions," says Robert H. Dicke. In all of the efforts that have been made to formulate a unified physical theory the big challenge has always been to bring gravitation within the theoretical framework. One of the most basic problems is to define the nature of the phenomenon. According to Einstein's general theory of relativity, the theory that is currently accepted (often with some reservations), gravitation is equivalent to a motion. This assertion implies that, while it has some of the characteristics of motion, it is actually not a motion. The objective of the present discussion is to examine the validity of this conclusion.

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