Claudius Ptolemy: (AD 90 - c. AD 168) was a Greco-Roman writer of Alexandria, known as a mathematician, astronomer, geographer, astrologer, and poet. His Planetary Hypotheses work presented a physical realization of the universe as a set of nested spheres with the earth at the center.
		Nicolas Copernicus: (1473 - 1543) was a Polish Renaissance mathematician and astronomer who formulated a heliocentric model of the universe which placed the Sun, rather than the Earth, at the center.
		Johannes Kepler: (1571 - 1630) was a German mathematician, astronomer, and astrologer. A key figure in the 17th century scientific revolution, he is best known for his laws of planetary motion. These works also provided one of the foundations for Isaac Newton's theory of universal gravitation.
		Issac Newton: (1642 - 1727) was an English physicist and mathematician who is widely recognised as one of the most influential scientists of all time. Newton also made seminal contributions to optics and shares credit with Gottfried Leibniz for the invention of infinitesimal calculus.