Summary
By 1590 Galileo Galilei had developed a number of criticisms of the
Aristotelian system's view of the physical world. Primary among these was
his theory on falling objects. In 1591, he demonstrated from the leaning tower
of Pisa that weights of one pound and one hundred pounds, dropped from the top
of the tower at the same time, hit the ground at the same time. Aristotle's
claim that the rate of fall was determined by the weight of an object was thus
overthrown, and replaced by Galileo's correct theory that the Earth's gravity
produced a universal acceleration of objects toward its surface. Galileo is
most important to the history of physics for his insistence upon viewing the
world in terms of calculable forces and measurable bodies, and his experimental
employment of this concept. In his 1638 Discourses Concerning Two New
Sciences, Galileo explores the relative strength of various physical
structures and his flawed theory on the attraction of separate particles which
produced solid objects. He goes on to reject the Aristotelian explanation of
the acceleration of falling bodies and substitutes his own, which has become the
foundation of modern dynamics.
In the years after Galileo's work, much work was done in the pursuit of a more
complete understanding of the character and conduct of matter. During the
Middle Ages, alchemists, considered experts on
matter, considered all matter to be made from four main elements: earth, air,
water, and fire. They believed that the variety of matter they observed
resulted from varying combinations of these four elements, and argued that if
one could adjust the proportions of these elements one could translate one type
of matter into another. Many alchemists spent their lives attempting to turn
lead into gold. Very little of scientific worth emerged from this school of
thought. One exception was the work of Jan Baptist Van Helmont of Belgium.
He experimented on the role of water in the growth of plants, claiming that
plants drew all of their substance from water. He also demonstrated that gases,
though they commonly appeared similar, could be quite different in character.
In fact, van Helmont invented the word 'gas.'
A large step in the understanding of the properties of gases was the invention
of the barometer, to measure air pressure, by Evangelista Torricelli in
1643. In 1656 Otto von Guericke invented the air pump, and did the first
experiments with vacuums, demonstrating many of the properties of gasses, such
as the (until then) disputed claim that they did, in fact, have weight. Von
Guericke also experimented a bit with electricity. Using von Guericke's air
pump, Robert Boyle and Robert Hooke of Oxford examined the elasticity,
compressability, and weight of the air. Boyle demonstrated later that only part
of the air was used in respiration and combustion, an important finding that
earned Boyle and Hooke credit as the discoverers of oxygen. Boyle's
Law, widely applied in physics and chemistry, states
that the volume of a gas varies inversely proportionally to the pressure exerted
upon it.
Boyle also worked extensively with more purely chemical experiments, his book,
The Skeptical Chymist (spelled with a 'y' in the original), debunks the
Aristotelian view of the four elements and suggests the use of chemical
indicators for the detection of acidic and basic liquids. In Boyle's Origin
of Forms and Qualities, published in 1666, he assumes the existence of a
universal type of matter, common to all bodies, and divisible into its smallest
components, which correspond to what are known today as atoms. He described the
structure of these smallest particles and the secondary structures that we know
as molecules. Though his views were largely flawed, they contributed greatly to
the study of the properties of matter.
The field of physics profited perhaps more than any other from the advances made
in mathematics, as physical phenomena could now be explained through the
quantification of forces that brought them about. Galileo was the first to
insist upon the quantification of these forces, arguing that only if quantified
would these forces lend themselves to logical description and understanding by
the human mind. Galileo's work in defining the properties of motion paved the
way for future physicists, and indeed, left the study of dynamics only a short
step from its utmost extension under Isaac Newton, who extrapolated
Galileo's theories into the laws of motion, and extended the Galileo's
mathematical theories on the laws of gravity into
fluxional calculus, which would become the cornerstone of modern physics.
Advances in physics constituted a sort of centerpiece in the evolution of
scientific knowledge during the Scientific Revolution. They were made possible
by advances in mathematics, which had linked pure numerical mathematics to
geometry and subsequently linked the new geometry to motion. The advances in
physics then gave birth to advances in astronomy, which applied the growing
knowledge of physics to the entire universe rather than simply to terrestrial
phenomena. However, during the immediate time of discovery, theories of physics
were generally applied solely to earthly phenomena.
