# The Man Who Found the Flat Spots in Space

/The theory behind Lagrangian points--those places in space where a vehicle can stay in the same position relative to two bodies--was conceived by an ingenious mathematician named Joseph-Louis Lagrange.

Born in Italy, he moved to Berlin to become the director of mathematics at the prestigious Prussian Academy of Sciences. He ended up in revolutionary France, where he became instrumental in development of the metric system. Lagrange helped invent probability theory and advanced number theory. He corrected Newton’s theory of sound, pioneered the study of work efficiency; and his calculus equations led to the greatest advances in physics in the nineteenth century.

Oh, and Napoleon, a huge fan (the feeling was not mutual), appointed Lagrange a senator in the French assembly. Engineers revere him for the math he brought to celestial mechanics.

In 1764, using a set of differential equations to calculate the gravitational dance of the Sun, Earth, and Moon, Lagrange explained why the Moon has one side always turned away from us. Eight years later, he helped solve one of the great mysteries of outer space: the “general three-body problem.” Take Earth, Moon, and Sun. You know the initial position, the mass, and the velocity of each. You know Newton’s laws of motion and universal gravitation. Now explain how all these forces act upon each other. Lagrange’s formulas helped form the math that determined the Apollo flights to the Moon.