Quote
"In all, Kepler tested seventy circular orbits against s Mars data, all to no avail. At one point, performing a leap of the imagination like Leonardos to the moon, he imagined himself on Mars, and sought to reconstruct the path the earths motion would trace out across the skies of a Martian observatory; this effort consumed nine hundred pages of calculations, but still failed to solve the major problem."
T
Timothy Ferris




