Johannes Kepler (1571-1630)
Modern astronomy begins with Copernicus (1473-1543) declaring (1530) the Earth rotates on its axis once daily and travels around the Sun once yearly. Next Tycho Brahe (1546-1601) made important contributions by devising instruments to observe motion of planets. In particular, Brahe compiled extensive data on the planet Mars. However, Johannes Kepler made the monumental discovery of the time. Brahe, fearing his bright assistant might eclipse him as the premiere astronomer of the day, assigned Kepler the perplexing orbit of the planet Mars (Mars has the most elliptical orbit of all the planets). Ironically it was precisely the Mars data that allowed Kepler to develop his three laws describing the orbit of planets around the Sun.
Kepler's Three Laws of Planetary Motion:
1. Planets revolve around the Sun in an elliptical path, with the Sun occupying one of the foci of the ellipse.
2. Straight line joining sun and planet sweeps out equal areas in equal intervals of time.
3. Squares of planets' orbital periods are proportional to the cubes of the semimajor axes of their orbits.

Galileo Galilei (1564-1642)
Mathematician/astronomer/physicist who made numerous contributions to modern science. Galileo was first to use telescope to gather evidence proving the earth revolves around the sun. His position represented such a radical departure from accepted thought that he was tried by the Inquisition in Rome, ordered to recant, and forced to spend the last eight years of his life under house arrest. But most of Galileo's projects didn't conflict with the church's interests?falling bodies, magnets, floating objects, the tides, compasses, arc of a cannonball, and rolling objects. He informally stated the principles later embodied in Newton's first two laws of motion. He also invented the mechanical pendulum clock, improved the telescope, and developed the first thermometer. Because of his pioneering work in gravitation/motion and in combining mathematical analysis with experimentation, Galileo is credited with ushering in the new age of science.

Sir Isaac Newton (1643-1727)
There can be no outstanding scientist list without Sir Isaac Newton; he made revolutionary advances in mathematics, optics, physics, and astronomy. In 1687 Newton published the Philosophiae naturalis principia mathematica. Principia, as it has become known, is recognized as the greatest scientific book ever written! Newton analyzed motion of bodies under the action of centripetal forces. The results were applied to orbiting bodies, projectiles, pendulums, and free-fall near the Earth. He further demonstrated planets were attracted toward the Sun by a force varying as the inverse square of the distance and generalized that all heavenly bodies mutually attract one another. In order to perform his calculations, Newton invented calculus.
Newton also explained a wide range of previously unrelated phenomena such as eccen...

Show full text: 10,619 characters