19:6 going forth. The Hebrew word does not refer to the sun’s daily orbit, but to that which “goes forth” from the sun itself—that is, the “heat thereof” the radiant energy which sustains all life on earth and even energizes the entire solar system.
19:6 his circuit. The critical charge that this verse reflects an unscientific geocentric view (the sun orbiting a fixed earth) is puerile. All motion is “relative motion,” since no one knows where a stationary “center of the universe” might be (the sun apparently moves in a gigantic circuit around the center of the Milky Way galaxy, and the galaxy itself moves with respect to other galaxies). The most scientific way of dealing with different motions is to assume a point of zero motion, and measure other motions relative to that. The best point to assume as a point of zero motion is the one for which the equations of motion are simplest. For all surveyors, all navigators, and most astronomers, that reference point is the surface of the earth at the location of the observer. David takes this scientific approach in referring to the sun’s motion relative to the earth. At the same time, his statement is also correct for any other assumed fixed point, since the sun and the galaxy do actually move throughout the whole universe.
19:6 hid from the heat. The laws of thermodynamics (i.e., “heat power”) are the most important and universal laws of science, and the sun’s heat “going forth” from its surface provides the basic energy for all earth’s processes. The First Law (conservation of energy in quantity) and Second Law (decay of energy quality) ultimately depend upon the sun’s heat for their meaningful existence and operation.