In this section, we look at physics before the age of  Relativity and Quantum Physics, although many scientists today include relativity as part of classical mechanics.  This was the time when it was thought that the Universe was deterministic, and that everything could be predicted at any scale.  Scientists of the age believed that both time and space were absolute.  Today, Classical Mechanics is often considered as the non-relativistic, non-quantum mechanical limit for large objects.  I have structured this section around some of the major contributors, in roughly chronological order.  These are not biographical pieces, but discuss their scientific contributions.  I include links to detailed biographies as appropriate. 

In early astronomy, the geocentric, or Ptolemaic, model is the theory that the Earth is the center of the universe and other objects, the planets, the sun and the other stars, go around it. Aristotle, Ptolemy, and most of the Ancient Greek and Chinese philosophers adhered to this idea.  This was based on the simple observation that they all appear to revolve around the Earth!  It was also inconceivable to them that the Earth could itself be moving, either through space or on its own axis.  This was the most commonly held view until late into the 16th century. 

It was probably Democritus and his mentor Leucippus who first proposed the ideas of "atoms".  They suggested this purely as a way to describe what they saw in the world, and had no empirical basis.  They suggested that atoms of metal are solid with hooks that allowed them to bind into solids, while liquid atoms were smooth and slippery etc.  Their ideas were not widely accepted.  I will pass over Aristotle as virtually everything he wrote in his principles of physics is so completely wrong!  Hipparchus, a Greek astronomer and mathematician, was born about 200 years after Aristotle.  He was the founder of trigonometry, and is generally considered to be the greatest observational astronomer of ancient times.  Some 300 years later, around AD140, Ptolemy almost certainly used his observational results when constructing his Planetary Hypotheses.  These hypotheses provided a physical description of the universe as a set of nested, crystal spheres on which the planets, the Sun, and the other stars were fixed.  He went on to calculate the dimensions of the universe; for example, he estimated that the Sun was at an average distance of 1210 times the radius of the Earth (approximately 7.7 million km or 4.8 million miles), and the sphere for the stars was 20,000 times the radius of the Earth (approximately 127.4 million km or 79.8 million miles).  So he underestimated things a little. 

The Beginnings

WILLIAM & DEBORAH HILLYARD

Physics -

Classical Physics

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