Western History 125: How did Physics and Astronomy develop in the 17th and 18th centuries?

Modern Science came of age in the 17^th Science with Galileo Galilei’s advancement of Experimental Science. In 1610 he used his own refracting telescope to observe the four large moons of Jupiter thus showing that celestial  objects need not orbit the Earth (he also saw the phases of Venus).  In 1638 Galileo's made use of inclined planes to determine the law for falling bodies. Galileo’s work on inertia (the property of mass that resists acceleration) served as the basis for Newton’s First Law of Motion and he is considered the leading thinker in the branch of physics known as kinemetics (study of motion without recourse to its cause).

Galileo Galilei source: britannica.com (he died in the same year that Newton was born 1642)

The early 17^th century was also the time frame that the German Mathematician Johannes Kepler developed his Three Laws of Planetary motion that he have already discussed in the question dealing with the Heliocentric Revolution/

However Physics in the 17^th century saw contributions from other players as well. Elizabethan scientist William Gilbert determined the nature of the Earth’s magnetic field and Dutchman Willebrod Snellius developed the law of refraction (Snell's Law)/. 

Earth's magnetic field source: livescience.com

Soon afterward in 1643, Evangelista Torricelli built a mercury barometer to measure air pressure. The Irishman Robert Boyle developed a law for ideal gases that showed the inverse relationship between the Pressure and Volume of a fixed mass of gas under constant temperature. His work was extended a century later by Jacques Charles who studied the impact of temperature on gas volume.

The second part of the 17^th century was the era most impacted by Sir Isaac Newton, arguably the greatest physicist of all time. It was Newton who demonstrated how white light can be broken down into component spectrum colours via a prism (dispersion) and then recombined (using a lens and another prism) to form white light again. He built one of the earliest reflecting telescopes, outlined the Three Laws of Motion and developed an equation for Universal Gravitation.

Sir Issac Newton source: nationalgeographic.org. Netwon published his results in his landmark work Principia (1687). He was encouraged to do so by his friend the noted astronomer Edmond Halley (of Halley Comet fame).Halley determined the periodicity of the comet.

Newton  synthesized Galilean inertia with his second law to show how the moon orbits the Earth and by extension the Earth orbiting the sun. He was able to show that gravity has both terrestrial and celestial implication sealing victory for the Heliocentric model.

Newton’s two rivals were Robert Hooke ,who showed how spring elongation varies with force and can be used to store elastic potential energy and Dutchman Christiaan Huygens, who studied Simple Harmonic Oscillators  and developed a wave front model of light that was later shown to conform well with reality (much more so than Newton’s corpuscular particle model). Another physicist, Dane Ole Roemer determined the speed of light in 1676.

Christiaan Huygens source: space.com

18^th century physics included a number of advances in Electricity. Ewald von Kleist invented the Leyden Jar in 1745. This was the first capacitor (storage device for electrical charge). American polymath  Benjamin Franklin identified lighting as a form of electricity in 1751 and Frenchman Charles Coulomb empirically worked out an inverse square law for the force between charges that had a similar form to Newton’s Law of Universal Gravitation. Like the Englishman Henry Canvendish who determined a value for the Universal  Gravitation Constant (G), Coulomb used a similar approach to determine a constant of proportionality for his charge law.

Benjamin Franklin conducting his famous kite and key experiment source: fi.edu

In Astronomy Immanuel Kant (of philosophy fame) posited a Gaseous  origin for the solar system (1755) that was extended over forty years later by Pierre-Simon Laplace into the Nebular Hypothesis. In 1171 Charles Messier developed a system for classifying distant objects in the sky (Messier catalogue). Observational astronomy was also boosted by the discovery of the planet Uranus by the German-born British astronomer William Herschel in 1781.

William Herschel was the Court astronomer of George III source: interlude.hk