Key Historical Milestones:

1820 — Oersted: Discovered that an electric current deflects a compass needle — first evidence that electricity and magnetism are related.

1831 — Faraday: Discovered electromagnetic induction — changing magnetic field induces electric current. Introduced concept of field lines.

1855–1864 — Maxwell: Developed the four equations of electromagnetism. Introduced displacement current (~1861) to fix Ampere's law. Predicted EM waves with speed c = 1/$\sqrt{μ_{0}ε_{0}}$ ≈ $3 \times 10^{8}$ m/s — matching the known speed of light. Declared: light is an electromagnetic wave (~1864).

1887 — Hertz: Experimentally confirmed Maxwell's prediction using oscillating circuits (spark gaps). Produced and detected radio waves in the lab. Demonstrated reflection, refraction, and interference of these waves.

1895 — Röntgen: Discovered X-rays accidentally while experimenting with cathode ray tubes. X-rays named because their nature was then unknown.

1896 — Becquerel: Discovered gamma rays from uranium radioactivity. Later shown to originate from nuclear transitions.

1901 — Marconi: First transatlantic radio transmission — proving radio waves could travel globally.

20th Century: Development of radar (WWII), microwave ovens (1947 by Percy Spencer — accidental discovery from radar work), infrared astronomy, X-ray medical imaging, radio telescopes.