Geophysicists utilize slight variations in gravitational force to characterize the mass of subsurface features. Particularly useful in petroleum exploration, subtle gravitational field differences can help identify solid subsurface plutonic bodies or fluid filled reservoirs.

1n 1687, English physicist Sir Isaac Newton (1642–1727) published a law of universal gravitation in his important and influential work Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy). In its simplest form, Newton's law of universal gravitation states that bodies with mass attract each other with a force that varies directly as the product of their masses and inversely as the square of the distance between them. This mathematically elegant law, however, offered a remarkably reasoned and profound insight into the mechanics of the natural world because it revealed a cosmos bound together by the mutual gravitational attraction of its constituent particles. Moreover, along with Newton's laws...