A Dynamical Theory of the Electromagnetic Field (1865)
Paper presenting the field equations and identifying light as an electromagnetic wave
Science · Physics
James Clerk Maxwell
1831–1879 · Scottish
Electromagnetism, kinetic theory and optics
James Clerk Maxwell, born in Edinburgh, unified electricity, magnetism and light in a single theory of the electromagnetic field, predicting that light is an electromagnetic wave. He also founded the statistical kinetic theory of gases, showed that Saturn's rings must consist of many small particles, and demonstrated the first colour photograph. He was the first Cavendish Professor of Physics at Cambridge.
How to spot them
- ▸Maxwell's equations; light as an electromagnetic wave
- ▸A Dynamical Theory of the Electromagnetic Field (1865); A Treatise on Electricity and Magnetism (1873)
- ▸Maxwell's demon; the Maxwell–Boltzmann distribution
- ▸The tartan ribbon: first colour photograph, shown in 1861
- ▸First Cavendish Professor; Glenlair, his Kirkcudbrightshire estate
Key discoveries & works
A Treatise on Electricity and Magnetism (1873)
Two-volume synthesis of electromagnetic theory
On Physical Lines of Force (1861–1862)
Mechanical model of the field introducing displacement current and hinting light is electromagnetic
Essay showing Saturn's rings are made of many small particles (1859)
Won Cambridge's Adams Prize; confirmed by the Voyager and Cassini missions
Demonstration of the first colour photograph (a tartan ribbon) (1861)
Three-colour method shown at the Royal Institution, photographs taken by Thomas Sutton
Distribution of molecular speeds in a gas (1860)
Statistical approach to kinetic theory, later extended by Boltzmann
Theory of Heat, introducing a sorting 'demon' (1871)
A thought experiment appearing to violate the second law of thermodynamics
Key ideas
- Electric and magnetic fields propagate as waves at a calculable speed equal to that of light
- Displacement current completes Ampère's law and allows electromagnetic waves
- Statistical mechanics: gas properties arise from distributions of molecular velocities
- Colour vision is trichromatic: any colour can be matched by mixing red, green and blue
- The compact four-equation form of Maxwell's equations was later developed by Oliver Heaviside
Quick-fire facts
- •Born at 14 India Street, Edinburgh, on 13 June 1831; died in Cambridge on 5 November 1879, aged 48, of abdominal cancer
- •Nicknamed 'Dafty' by schoolfellows at Edinburgh Academy
- •Published his first scientific paper, on oval curves, aged 14
- •Held posts at Marischal College, Aberdeen, and King's College London before Cambridge
- •Became the first Cavendish Professor of Experimental Physics in 1871 and oversaw the building of the Cavendish Laboratory
- •Einstein, born the year Maxwell died, kept a photograph of him on his study wall
- •The maxwell is the CGS unit of magnetic flux; the James Clerk Maxwell Telescope is in Hawaii
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Sources
- MacTutor History of Mathematics, University of St Andrews — James Clerk Maxwell
- Basil Mahon — The Man Who Changed Everything: The Life of James Clerk Maxwell