Download Lecture 14 - York University

Lecture 14 – NATS 1710 - Turn of the Century Physics
- 19th / 20th century: realization of promise of natural philosophy for
society
- Two scientific traditions emerge from scientific revolution:
 Classical: astronomy, mathematics, mechanics, optics
 Theoretical and mathematical, problem oriented
 Baconian: electrical studies, experimental, less theoretical,
instrumental
Testing Newton:
 Halley’s comet (1758-59)
 In 1761 and 1769 passage of Venus across sun
 Uranus in 1781, Neptune 1846
- Pierre Laplace (1749-1827)
o Expansion of Newton’s work
o “I had no need of that hypothesis”
- Newton’s queries from the “Optiks”
- Ether used to explain electricity and magnetism
Electrical Studies as “Baconian” Science
- 1665 von Guericke, friction and electricity
- Studies of conduction, insulation, attraction and repulsion
- Stephen Gray (1666-1736), electricity an imponderable fluid
- Leyden jar, stored electricity for later use
- John Cockcroft (1897-1967) particle accelerator with Leyden jars
- Benjamin Franklin, electricity and lightning identical
Other Areas of Baconian Interest
- Meteorology, botany, natural history and geology
Chemistry, the “Odd Science Out?”
- Experimental tradition and instrument dependence of chemistry
- Phlogiston chemistry, nomenclature
- Lavoisier’s caloric
The “Second” Scientific Revolution
- Two trends: mathematization and unification
Electricity Again
- 1780 Luigi Galvani (1737-1798): frog’s legs spasm when spark
applied, “animal electricity”
- Coulomb (1736-1806): electrical charge (1785)
o Inverse square force relationship for magnetism & electricity
- Allesandro Volta (1745-1827) 1795, battery, electrical experiments
- John Dalton (1766-1844), chemical atomism, mechanical philosophy
- Hans Christian Oersted (1777-1851), magnetism and electricity
Michael Faraday (1791-1867)
- Experimentalist, “plunges a magnet through a closed coil of wire”
- Produces current, electric motor (1821)
- 1831 to 1838 Faraday questioned force at a distance
- 1845, rotation of plane of polarization of light due to magnetic field
- Lines of magnetic force, the concept of a field
- Electricity important as it was easily transformed and transmitted,
universal
- Telegraphy, electric power and electric lighting
James Clerk Maxwell (1831-1879)
- Unified electricity & magnetism, mathematized Faraday’s work
- Field theories, mathematical and physical theories
Sadi Carnot (1796-1832)
o Carnot studied the heat engine cycle, and determined limiting
efficiencies
 Efficiency (n) is: n = 1 – (To/Ti)
o First scientific analysis of steam engine
Social and Institutional Status of Science
- State institutions and universities
- “Scientist”, 1840
- Unification of sciences, science and technology
- University / industry partnerships, research laboratories (Kodak,
Dupont, Bayer)
Becquerel’s Experiment
- Small scale versus large scale science, cumulative scientific
developments
- Simplicity of experiments and purity of samples