The son of a poor illiterate farmer, Newton became the first scientific superstar. He entered Cambridge University in 1661 and was granted the degree of Bachelor of Arts in 1665. He left Cambridge for the country from 1665-1666 because the black plague had struck. In 1669 he was appointed Professor of Mathematics at Trinity College in Cambridge, eventually knighted for his achievements, his scientific reputation was unmatched until Einstein in this century. In mathematics, he discovered the binomial theorem and formulated the calculus. In 1666, he was able to establish that light is made up of colors that could be separated by a prism. In his Discourse on Optiks he described the laws of refraction and reflection. At about the same time, he explained the causes of motion (dynamics) in his celebrated three mathematical laws that encompass the motion of all objects, terrestrial or celestial. Central to this explanation is the notion of force. 
 

• Law 1. Inertia. Objects at rest remain at rest, and objects in unaccelerated motion remain in unaccelerated motion.
• Law 2. F= MA. Forces cause masses to accelerate. Acceleration is proportional to the force and is in the direction in which the force is applied. 
• Law 3. Forces come in pairs. Forces arise from interactions and in any interaction, the force on one object is equal in amount and opposite in direction to the force on the other object.

From Newton's time, one of the main currents of astronomical accomplishments focuses once again on expansion of our knowledge of the Solar System, a rich tradition that continues into our own century. In 1781, Herschel discovers Uranus. In 1846 Galle discovers Neptune. In 1930 Clyde Tombaugh discovers Pluto, and in 1978, Christy discovers Pluto's moon Charon. Nor should the legacy of discoveries from the space age be left unmentioned, as our travels to the moon and continued exploration of the Solar System by unmanned probes have enriched our knowledge and understanding immeasurably. 

In the 20th Century, astronomy expands beyond the Solar System and the Milky Way and becomes truly universal. With the discovery of variable cepheids (a type of star that can be used to determine distances) in spiral nebulae, Hubble is able to show that these spiral nebulae lie way outside the Milky Way, and thereby radically expands our concept of the size and richness of the universe. Mathematically, Einstein introduces a relativistic universe.