3rd Cent bc Euclid of Alexandria (325-265 bc)  
  writes, among many other works, Optics, dealing with vision theory and perspective.
1st Cent bc      
  Chinese fortune tellers begin using loadstone to construct their divining boards, eventually leading to the first compasses. (Mentioned in Wang Ch’ung’s Discourses Weighed in the Balance around 83 B.C.)
1st Cent      
  South-pointing divining boards become common in China.
2nd Cent Claudius Ptolemy (87-150)  
  writes on optics, deriving the law of reflection from the assumption that light rays travel in straight lines (from the eyes), and tries to establish a quantitative law of refraction.
2nd Cent Hero of Alexandria    
  writes on the topics of mirrors and light.
3rd Cent      
  True compasses come into use in China.
6th Cent      
  Discovery that loadstones could be used to magnetize small iron needles.
11th Cent Abu Ali al-Hasan ibn al-Haitam (Alhazen) (965-1039)  
  writes Kitab al-manazir (translated into Latin as Opticae thesaurus Alhazeni in 1270) on optics, dealing with reflection, refraction, lenses, parabolic and spherical mirrors, aberration and atmospheric refraction.
11th Cent      
  Iron is magnetized by heating it to red hot temperatures and cooling while in south-north orientation.
1086 Shen Kua (1031-1095)  
  writes Dream Pool Essays and makes the first reference to compasses used in navigation.
1150s      
  An anonymous author penned the earliest explicit reference to magnets per se, in Roman d’Enéas.
1190s Alexander Neckam (1157–1217)  
  writes De naturis rerum. It is the first western reference to compasses used for navigation.
13th Cent Robert Grosseteste (1168-1253)  
  writes De Iride and De Luce on optics and light, experimenting with both lenses and mirrors.
13th Cent Roger Bacon (1214-1294)  
  is the first to try to apply geometry to the study of optics. He also makes some brief notes on magnetism.
13th Cent Pierre de Maricourt, a.k.a. Petri Pergrinus (1269)  
  writes Letter on the magnet of Peter the Pilgrim of Maricourt to Sygerus of Foucaucourt, Soldier, the first western analysis of polar magnets and compasses. He also demonstrates in France the existence of two poles of a magnet by tracing the directions of a needle laid on to a natural magnet.
13th Cent Erazmus Ciolek Witelo (1230-1275)  
  writes Perspectiva around 1270, treating geometric optics, including reflection and refraction. He also reproduces the data given by Ptolemy on optics, though was unable to generalize or extend the study.
13th Cent Theodoric of Freiberg (1250-1310)  
  working with prisms and transparent crystalline spheres, formulates a sophisticated theory of refraction in raindrops which is close to the modern understanding, though it did not become very well known. (Descartes presents a nearly identical theory roughly 450 years later.)
13th Cent      
  Eyeglasses, convex lenses for the far-sightedness were first invented in or near Florence (as early as the 1270’s). Concave lenses for the near-sightedness appeared in the late 15th century.
16th Cent Girolamo Cardano (1501-1576)  
  elaborates the difference between amber and loadstone.
1558 Giambattista della Porta (1535-1615)  
  publishes his major work, Magia naturalis, analyzing, among many other things, magnetism.
1600 William Gilbert (1544-1603)  
  after 18 years of experiments with loadstones, magnets and electrical materials, finishes his book De Magnete. The work included: the first major classification of electric and non-electric materials; the relation of moisture and electrification; showing that electrification effects metals, liquids and smoke; noting that electrics were the attractive agents (as opposed to the air between objects); that heating dispelled the attractive power of electrics; and showing the earth to be a magnet.
1606      
  della Porta is the first to describe the heating effects of light rays.
1618 Francesco Maria Grimaldi (1618-1663)  
  discovers diffraction patterns of light and becomes convinced that light is a wave-like phenomenon. The theory is given little attention.
1621 Willebrord van Roijen Snell (1580-1626)  
  experimentally determines the law of angles of incidence and reflection for light and for refraction between two media.
1629 Nicolo Cabeo (1585-1650)  
  publishes his observations on electrical repulsion, noting that attracting substances may later repel one another after making contact.
1637 René Descartes (1596-1650)  
  publishes his Dioptics and On Meteors as appendices to his Discourse on a Method, detailing a theory of refraction and going over a theory of rainbows which, while containing nothing essentially new, encouraged experimental exploration of the subject.
1644      
  Descartes’ Principia philosophiae, describing magnetism as the result of the mechanical motion of channel particles and their displacements, and proposing the absence of both void and action at a distance.
1646 Thomas Browne (1605–1682)  
  coins the term electricity in his Pseudodoia Epidemica.
1657 Pierre de Fermat (1601-1665)  
  formulates the principle of least time for understanding the way in which light rays move.
1660 Otto von Guericke (1602-1686)  
  builds the first electrical machine, a rotating frictional generator.
1661      
  Fermat is able to apply his principle of least time to understand the refractive indices of different materials.
1664 Robert Hooke (1635-1703)  
  puts forth a wave theory of light in his Micrographia, considering light to be a very high speed rectilinear propagation of longitudinal vibrations of a medium in which individual wavelets spherically spread.
1665      
  Grimaldi’s Prysico-mathesis de lumine coloribus et iride describes experiments with diffraction of light and states his wave theory of light.
1669 Erasmus Bartholin (1625-1698)  
  publishes A Study of Iceland Spar, about his discovery of double refraction.
1675 Robert Boyle (1627-1691)  
  writes Experiments and Notes about the Mechanical Origin or Production of Particular Qualities.
1676 Ole Christensen Römer (1644-1710)  
  demonstrates the finite speed of light via observations of the eclipses of the satellites of Jupiter, although he does not calculate a speed for light. His results were not widely accepted.
1677 Christiaan Huyghens (1629-1695)  
  extends the wave theory of light in his work Treatise on Light, unpublished until 1690.
1687 Sir Isaac Newton (1642-1727)  
  notes magnetism to be a non-universal force and derives an inverse cubed law for two poles of a magnet.
1690      
  Huyghens formulates his wave theory of light in Traité de la Lumière, giving the first numerical quote for the speed of light, usually attributed to Römer, of 3.0 x 108 m/s.
1704      
  Newton’s research on light culminates in the publication of his Optics, describing light both in terms of wave theory and his corpuscular theory.
1709 Francis Hauksbee (1666-1713)  
  publishes Physico-Mechanical Experiments on various subjects.
1728 James Bradley (1693-1762)  
  discovers the phenomenon of steller aberration, confirming earlier suggestions by Römer that the speed of light is finite.
1729 Stephen Gray (1670-1736)  
  shows static electricity to be transported via substances, especially metals.
1733 Charles-Francois de Cisternai du Fay (1698-1739)  
  discovers that electric charges are of two types and that like charges repel while unlike charges attract.
1745 Ewald Jürgen Georg von Kleist (1700-1748)  
  invents the Leyden jar for storing electric charge.
1746 William Watson (1715-1789)  
  suggests conservation of electric charge.
1746 Jean Antoine Nollet (1700–1770)  
  publishes Essai sur l’electricité des corps.
1747 Benjamin Franklin (1706-1790)  
  proposes that electricity be modeled by a single fluid with two states of electrification, materials have more or less of a normal amount of electric fluid, independently proposing conservation of electric charge, and introducing the convention of describing the two types of charges as positive and negative.
1747      
  Watson passes electrical charge along a two mile long wire.
1750 John Michell (1724-1793)  
  demonstrates that the action of a magnet on another can be deduced from an inverse square law of force between individual poles of the magnet, published in his work, A Treatise on Artificial Magnets.
1759 Franz Ulrich Theodosius Aepinus (1724-1802)  
  publishes An Attempt at a Theory of Electricity and Magnetism, the first book applying mathematical techniques to the subject.
1764 Johannes Karl Wilcke (1732-1796)  
  invents the electrophorus, a device which can produce relatively large amounts of electric charge easily and repeatedly.
1766 Joseph Priestley (1733-1804)  
  deduces the inverse square law for electric charges using the results of experiments showing the absence of electrical effects inside a charged hollow conducting sphere.
1772 Henry Cavendish (1731-1810)  
  publishes, An Attempt to Explain some of the Principal Phenomena of Electricity, by Means of an Elastic Fluid.
1775 Alessandro Guiseppe Antonio Anastasio Volta (1745-1827)  
  invents an electrometer, a plate condenser and the electrophorus.
1777 Charles Augustin de Coulomb (1736-1806)  
  research sets a new direction in research into electricity and magnetism.
Early 1780s Luigi Galvani (1737-1798)  
  uses the response of animal tissue to begin studies of electrical currents produced by chemical action rather than from static electricity. The mechanical response of animal tissue to contact with two dissimilar metals is now known as galvanism.
1785      
  Coulomb independently invents the torsion balance to confirm the inverse square law of electric charges. He also verifies Michell’s law of force for magnets and also suggests that it might be impossible to separate two poles of a magnet without creating two more poles on each part of the magnet.
1799      
  Volta shows that galvanism is not of animal origin but occurred whenever a moist substance is placed between two metals. This discovery eventually leads to the “Volta pile” a year later, the first electric batteries.
1800      
  Volta writes a paper on electricity by contact.
1801 Thomas Young (1773-1829)  
  work on interference revives interest in the wave theory of light. He also accounts for the recently discovered phenomenon of light polarization by suggesting that light is a vibration in the aether transverse to the direction of propagation.
1801 Johann Georg von Soldner (1776-1833)  
  makes a calculation for the deflection of light by the sun assuming a finite speed of light corpuscles and a non-zero mass. (The result, 0.85 arc-sec, was rederived independently by Cavendish and Einstein in 1911, but went unnoticed until 1921.)
1807 Sir Humphrey Davy (1778–1829)  
  prepared a lecture, On Some Chemical Agents of Electricity which came very close to describing the possible relationships of chemical and electrical forces.
1812 Simeon-Denis Poisson (1781-1840)  
  formulates the concept of macroscopic charge neutrality as a natural state of matter and describes electrification as the separation of the two kinds of electricity. He also points out the usefulness of a potential function for electrical systems.
1813 François Étienne de la Roche (1780-1813)  
  Co-researched measurements of specific heat of air as a function of pressure.
1813 Jacques Étienne Bérard (1789-1869)  
  Co-researched measurements of specific heat of air as a function of pressure.
1814 Augustin Jean Fresnel (1788-1827)  
  independently discovers the interference phenomena of light and explains its existence in terms of wave theory.
1817      
  Fresnel predicts a dragging effect on light in the aether.
1818      
  Fresnel writes an essay on optics and the ether.
1820 Hans Christian Oersted (1777-1851)  
  notes the deflection of a magnetic compass needle caused by an electric current after giving a lecture demonstration. Oersted then demonstrates that the effect is reciprocal. This initiates the unification program of electricity and magnetism.
1820 André Marie Ampére (1775-1836)  
  confirms Oersted’s results and presents extensive experimental results to the French Academy of Science. He models magnets in terms of molecular electric currents. His formulation inaugurates the study of electrodynamics independent of electrostatics.
1820 Jean-Baptiste Biot (1774-1862)  
  co-developed the formula for the strength of the magnetic effect produced by a short segment of current carrying wire.
1820 Felix Savart (1792-1841)  
  co-developed the formula for the strength of the magnetic effect produced by a short segment of current carrying wire.
1825      
  Ampére’s memoirs are published on his research into electrodynamics.
1827 Georg Simon Ohm (1789-1854)  
  formulates the relationship between current to electromotive force and electrical resistance.
1828 George Green (1793-1841)  
  introduces the notion of potential and formulates what is now called Green’s Theorem relating the surface and volume distributions of charge. (The work goes unnoticed until 1846.)
1831 Michael Faraday (1791-1867)  
  begins his investigations into electromagnetism.
1832 Carl Friedrich Gauss (1777-1855)  
  independently states Green’s Theorem without proof. He also reformulates Coulomb’s law in a more general form, and establishes experimental methods for measuring magnetic intensities.
1835      
  Gauss formulates separate electrostatic and electrodynamical laws, including Gauss’s law. All of it remains unpublished until 1867.
1838      
  Faraday explains electromagnetic induction, electrochemistry and formulates his notion of lines of force, also criticizing action-at-a-distance theories.
1838 Wilhelm Eduard Weber (1804-1891)  
  he and Gauss apply potential theory to the magnetism of the earth.
1839      
  The potential theory for magnetism developed by Weber and Gauss is extented to all inverse-squared phenomena.
1842 William Thomson a.k.a. Lord Kelvin (1824-1907)  
  writes a paper, On the uniform motion of heat and its connection with the mathematical theory of electricity, based on the ideas of Jean Baptiste Joseph Fourier (1768-1830). The analogy allows him to formulate a continuity equation of electricity, implying a conservation of electric flux.
1845 – 1850      
  Faraday introduces the idea of contiguous magnetic action as a local interaction, instead of the idea of instantaneous action at a distance, using concepts now known as fields. He also estabishes a connection between light and electrodynamics by showing that the transverse polarization direction of a light beam was rotated about the axis of propagation by a strong magnetic field (today known as Faraday rotation).
1845 – 1850 Gustav Theodor Fechner (1801–1887)  
  proposes a connection between Ampére’s law and Faraday’s law in order to explain Heinrich Friedrich Emil Lenz’s law (1804-1865).
1846      
  Weber proposes a synthesis of electrostatics, electrodynamics and induction using the idea that electric currents are moing charged particles. The interactions are instantaneous forces. Weber’s theory contains a limiting velocity of electromagnetic origin.
1846 William Robert Grove (1811-1896)  
  writes Correlation of physical forces the partial-drag theory of George Gabriel Stokes (1819-1903) is revived for
the explanation of stellar aberration.
1849 Armand Hippolyte Louis Fizeau (1819-1896)  
  begins experiments to determine the speed of light.
1851      
  Fizeau’s interferometry experiment confirming Fresnel’s theoretical results.
1852      
  Stokes names and explains the phenomena of fluorescence.
1854 Bernhard Riemann (1826-1866)  
  makes unpublished conjectures about an investigation of the connection between electricity, galvanism, light and gravity.
1855 Heinrich Friedrich Theodor Kohlrausch (1780-1867)  
  co-determined with Weber a limiting velocity which turns up in Weber’s electrodynamic theory, and that it’s value is about 439,450 km/s.
1855 – 1868 James Clerk Maxwell (1831-1879)  
  completes his formulation of the field equations of electromagnetism. He established, among many things, the connection between the speed of propagation of an electromagnetic wave and the speed of light, and establishing the theoretical understanding of light.
1858      
  Riemann generalizes Weber’s unification program and derives his results via a solution to a wave function of a electrodynamical potential (finding the speed of propagation, correctly, to be c). He claimed to have found the connection between electricity and optics. (Results published postumously in 1867.)
1861      
  Riemann uses Lagrange’s theorem to deal with velocity-dependent electrical accelerations.
1861 Gustav Robert Kirchhoff (1824-1887)  
  formulates the model of the black body.
1863 John Tyndall (1820-1893)  
  publishes Heat Considered as a Mode of Motion.
1864      
  Maxwell publishes A Dynamical Theory of the Electromagnetic Field, his first publication to make use of his mathematical
theory of fields.
1865      
  Maxwell publishes A Dynamical Theory of the Electromagnetic Field, formulating an electrodynamical formulation of wave propagation using Lagrangian and Hamiltonian techniques, obtaining the theoretical possibility of generating electromagnetic radiation. (The derivation is independent of the microscopic structures which may underlie such phenomena.)
1870 Hermann Ludwig Ferdinand von Helmholtz (1821-1894)  
  developes a theory of electricity and shows Weber’s theories to be inconsistent with the conservation of energy.
1873      
  The first edition of Maxwell’s Treatise on Electricity and Magnetism is published.
1874 George Johnstone Stoney (1826–1911)  
  estimates the charge of an electron to be about 10-20 Coulombs and introduces the term electron.
1875 Hendrik Antoon Lorentz (1853-1928)  
  in his doctoral thesis, derives the phenomena of reflection and refraction in terms of Maxwell’s theory.
1875 Sir William Crookes (1832-1919)  
  performs experiments on cathode rays.
1879      
  Maxwell suggests that an earth-based experiment to detect possible ether drifts could be performed, but that it would not be sensitive enough.
1881 Albert Abraham Michelson (1852-1931)  
  begins his interferometry experiments to detect a luminiferous ether.
1884 Heinrich Rudolf Hertz (1857-1894)  
  develops a reformulation of electrodynamics and shows his and Helmholtz’s theories both amount to Maxwell’s theory.
1884 John Henry Poynting (1852–1914)  
  establishes that for electromagnetic radiation energy can be localized and flow (the first such energy localization principle established).
1885 – 1887 Oliver Heaviside (1850-1925)  
  writes Electromagnetic induction and its propagation over the course of two years, re-expressing Maxwell’s results in 3 (complex) vector form, giving it much of its modern form and collecting together the basic set of equations from which electromagnetic theory may be derived (often called Maxwell’s equations). In the process, He invents the modern vector calculus notation, including the gradient, divergence and curl of a vector.
1887      
  Hertz experimentally produces electromagnetic radiation with radio waves in the GHz range, also discovering the photoelectric effect and predicting that gravitation would also have a finite speed of propagation.
1887 Woldemar Voight (1850-1919)  
  working through an analysis of Doppler effects using an elastic model of the luminiferous ether to describe optical properties, produces a set of relations between space and time intervals which are later rediscovered independently by Lorentz and now known as the Lorentz equations (first so-called by Poincaré in 1904).
1889 George Francis Fitzgerald (1851-1901)  
  suggests that bodies contract in the direction of motion against the luminiferous ether by an amount which would account for the null results coming from the Michelson-Morley experiments on ether motion. A more detailed calculation is performed independently by Lorentz in 1895.) Fitzgerald also suggests that the speed of light is an upper bound on any possible speed. (This suggestion reappears in 1900 by Lorentz, in 1904 by Poincaré, and again in 1905 by Einstein.)
1889 John William Strutt a.k.a. Lord Rayleigh (1842-1919)  
  presents a model for radiation in terms of wave propagation.
1890      
  Hertz publishes his memoirs on electrodynamics, simplifying the form of the electromagnetic equations, replacing all potentials by field strengths, and deduces Ohm’s, Kirchoff’s and Coulomb’s laws.
1892 – 1904      
  Lorentz completes the description of electrodynamics by clearly separating electricity and electrodynamic fields and formulating the equations for charged particles in motion.
1893 Wilhelm Carl Werner Otto Fritz Franz Wien (1864-1928)  
  gives his displacement law of blackbody radiation.
1896      
  Wien theoretically derives the radiation distribution law.
1896      
  The discovery of X-rays and Becquerel radiation.
1896      
  The discovery of the Zeeman effect.
1897 Joseph John Thomson (1856-1940)  
  experimentally determines the charge-to-mass ration of electrons.
1898 Jules Henri Poincaré (1854-1912)  
  suggests that a complete measurement theory must formulate a notion of distant synchronization and discusses its relevance to the apparent constancy of the speed of light.
1899      
  Lorentz refines the transformation laws, formulating the notion of local time and local coordinate systems in electrodynamics.
1899 Thomson and Philipp Eduard Anton von Lenard (1862-1947)  
  begin experimental investigations of photoelectric radiation.
1904      
  Poincaré uses light signals as a functional technique to establish distant synchronization in application to Lorentz’s electron theory, also putting forth the first formulation of a principle of electrodynamic relativity.
1905 Albert Einstein (1879-1955)  
  analyzes the phenomena of the photoelectric effect and theorizes that light may be taken to be made up of vast amounts of packets of electromagnetic radiation in discrete units.
1905      
  Einstein publishes his paper, On the Electrodynamics of Moving Bodies, drawing out the symmetries of Lorentz’s electromagnetic theory, underlying connection in measurement theory and the status of the electromagnetic ether.
1907 Hermann Minkowski (1864-1909)  
  through considerations of the group properties of the equations of electrodynamics, re-interprets Einstein’s relativity theory as a kind of geometry of spacetime, considered as a single medium.