Advances and theories

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Astronomy and mechanics were not the only scientific fields that saw great advances during the seventeenth century.

Galileo himself devised a type of thermometer. It was based on the principle that liquids expand as they are heated; when the temperature of a liquid rises, its specific gravity drops. A glass sphere that will just float in water at one temperature, will sink when the water gets a little warmer. A collection of such spheres, each of different specific gravity, can be used to determine the water's temperature.

A pupil of Galileo, Evangelista Torricelli (1608-47) recognized that atmospheric pressure affected how far liquid would rise in a tube, and used this to invent the first barometer. Torricelli was also an important mathematician.

Otto von Guericke (1602-86) became deeply interested in the possibility of creating a true vacuum and invented the first air-pump in order to create one. He combined the pump with two bronze hemispheres, engineered to fit exactly together, and then sucked out the air. In an dramatic display before Emperor Ferdinand III at Regensburg in 1654, he then demonstrated that it required sixteen horses to drag the two spheres apart. Guericke was also the inventor of a machine to produce electrical sparks.

William Gilbert (1544-1603) published in 1600 De magnete. He distinguished between magnetic and electric (a term he coined) forces, described the earth's magnetic field and named its poles, and explained the use of the magnet in navigation. The compass had been in use for decades, but Gilbert explained its deviation and declination.

	William Harvey (1578-1657) an Englishman who had studied at the University of Padua, published De motu cordis (1628). This described the circulation of the blood in animals for the first time.
	Another important invention was the compound microscope, developed by Zacharias Janssen, Galileo, and Antony van Leeuwenhoek (1632-1723) who observed & described bacteria, protozoa, sperm, & red blood cells.
	Robert Boyle (1627-91), the father of modern chemistry discovered Boyle's law (PV = k) showing that the pressure of gas is inversely proportionate to its volume.

John Napier (1550-1617) invented logarithms and published an account of them in 1614. He also invented a table called "Napier's bones" to work out square roots and cube roots.

René Descartes (1596-1650) pioneered co-ordinate geometry, showing that geometric problems could be reduced to algebraic problems and solved more easily.
In La Géometrie, Descartes modestly requested, "I hope that posterity will judge me kindly, not only as to the things which I have explained, but also to those which I have intentionally omitted so as to leave to others the pleasure of discovery".

In Italy, Bonaventura Cavalieri (1598-1647) worked on indivisibles, conic sections and trigonometry. The polymath Gottfried Wilhelm von Leibniz (1646-1716) worked on mathematics and developed a version of infinitesimal calculus.

Isaac Newton

The towering figure of seventeenth century science was Isaac Newton (1642-1727).

"During the last quarter-millennium of unprecedented human change, Newton has enjoyed an influence and authority only comparable to that of Aristotle in the two previous millennia. If one had to sum up the history of scientific ideas about the universe in a single sentence, one could only say that up to the seventeenth century our vision was Aristotelian, after that Newtonian."

(A. Koestler).

	Isaac Newton was educated at the University of Cambridge and became Lucasian Professor of Mathematics there in 1669.
	Independently of Leibniz (who later became involved in a quarrel about precedence) Isaac Newton developed the basic ideas of differential and integral calculus.

	Galileo and Descartes had argued that both planets and terrestrial bodies acted in accordance with the same laws of motion. It was Newton who described exactly what these laws were. His Philosophiae naturalis principia mathematica (1687) laid out three laws of motion and changed humanity's comprehension of the universe forever.
1. Every object in a state of rest or of uniform motion tends to remain in that state unless an external force is applied to it. 2. For a constant mass, force equals mass times acceleration. (i.e. F = ma: where m is an object's mass, its acceleration is a, and the applied force is F). 3. For every action there is an equal and opposite reaction.

Newton applied his three laws to explaining both events on earth such as the tides of the sea, the motion of comets and planets, and a universal quantitative theory of gravitation.

Newton's experimented with prisms and light and so discovered the heterogeneous, corpuscular nature of white light. This was the foundation for almost all subsequent work on the nature and properties of light.

	Newton invented a new type of telescope - the reflecting telescope - in 1668. (Galileo used a refracting telescope). Because the reflector used a mirror rather than lenses, it was both cheaper and easier to produce in really large sizes. Robert Hooke (1635-1703) soon built a large reflecting telescope and used it to study Mars and recognize that Jupiter rotated on its axis. However, he and Newton were at daggers drawn and never co-operated on scientific matters.
	Sir Isaac Newton was not only a scientist but a public figure. He became President of the Royal Society in 1703 and was knighted in 1705 (the first English scientist to be so honored). He was a Member of Parliament (1689-90, & 1701-02) and was Warden (1696) and then Master (1699-1727) of the Royal Mint. Newton played an active role there, working on tracing forgers, setting the value of the guinea at 21 shillings, and administering the re-coinage of the 1690s.
	Sir Isaac Newton was deeply interested in biblical chronology and prophesies. Although only one of his works on the topic - Observations Upon the Prophecies of Daniel and the Apocalypse of St. John (1733) - was published, Newton devoted vast amounts of time to considering such matters.

"I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me".

(Sir Isaac Newton).

Scientific organizations

The Royal Society was established with Charles II's support in 1662. It encouraged scientific experimentation and disseminated the results of these experiments and other scientific news and theories to members all over England. The Royal Society's Journal, The Philosophical Transactions was first published in 1665, and is now the oldest scientific journal in continuous publication.

In France the Journal des sçavans (sçavans = savants, scholars or scientists) was published from 1665 under the direction of Denys de Sallo, Sieur de Hedouville (1626-1669). He obtained Colbert's support for his scheme for copying and publishing extracts from and reviews of the most interesting scientific, literary and artistic writings of the day.

	The ACADEMIE ROYALE DES SCIENCES had its origins in regular meetings of French scientists, including Descartes, Pascal and Fermat. The Académie, authorized by Louis XIV, held its first official meeting in December 1666, and discussed exclusively scientific subjects. It published the Histoire and Mémoires, which documented research, from 1699.The Histoire covered physics, chemistry, botany and mathematics. The Mémoires included contributions by the Italian astronomer Giovanni Domenico Cassini (1625-1712), Nicholas Malebranche (1638-1715), Johann Bernoulli,Guillaume-François-Antoine de L’Hopital (deviser of L'Hopital's Rule), Gottfried Wilhelm von Leibniz and others.
	Another influential scientific journal, the Acta eruditorum, was published in Leipzig from 1682, edited by Otto Mencke (1644-1707). Leibniz was one of its main contributors (often carrying on his controversy with Newton).
	The scientific academies of Europe kept in touch with one another and their journals spread news of scientific developments across Europe. The educated public were interested in science, and at this time the publications were generally not so technical as to be beyond interested amateurs.