Ernest William Brown FRS was an English mathematician and astronomer, who spent the majority of his career working in the United States and became a naturalised American citizen in 1923.
Ernest William Brown, from the American Mathematical Society
Lunar theory attempts to account for the motions of the Moon. There are many small variations in the Moon's motion, and many attempts have been made to account for them. After centuries of being problematic, lunar motion can now be modeled to a very high degree of accuracy.
Newton's diagram 'to find the force of the Sun to perturb the Moon' accompanying Book 3, Proposition 25 of the Principia
Alternative depiction of solar perturbations, vectors LS1 and LS2, like LS in Newton's diagram above, for 2 positions of the Moon P in its orbit around the Earth S
The Laser Ranging Facility at Goddard Spaceflight Center