**Edmund Halley (1656 - 1742) was an English astronomer and mathematician. He is known for being one of the first to demystify the orbit of comets and for calculating the orbit of Halley’s comet. Halley was a member of the Royal Society and was involved with the publication of great works by Isaac Newton, particularly his theory of gravitation.**

**Along with other members from the royal society, including Robert Hooke and Sir Christopher Wren, Halley worked on an explanation for how the planets move. Together, they hypothesized about the forces which kept planets in orbit around the sun. Halley and Hooke had found that the force keeping a planet in motion decreases as the inverse of the square of its distance from the sun but could not come up with an orbit to match the equation. When Halley first visited Newton in 1684 in Cambridge, Newton told Halley that he had already solved the problem five years previous - that the orbit would be an ellipse - but could not put the mathematics together to prove it. Halley encouraged him to continue his work on the topic, which he did and compiled in a work called Principia, which was “one of the greatest masterpieces produced by the mind of man,” according to sources. The Royal Society assigned Halley to produce the book, which he published in 1687.**

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