Gregor Mendel's pea plant experiments lead him to surmize many of the fundemental theories of genetics (dominant vs recessive genes, the 1-2-1 ratio, etc) (1856-1863)
Archimedes, while sitting in a bathtub, notices that his body becomes lighter as it pushes the water aside. This leads to the first true theory of buoyancy. (c. 250 BC)
Eratosthenes evaluates the diameter of the Earth by comparing the length of the lengthiest shadow of the day with the distance between that location and a place where the sun shines to the bottom of the well at midday (240 BC)
Galileo Galilei uses rolling balls to disprove the Aristotelian theory of motion (1602 - 1607)
Ole Rømer uses the timing of the eclipses of the moons of Jupiter with respect their distance from earth to estimate the speed of light for the first time. He yields a value of 225,000 km/s (Actual value of 299,792 km/s) (1672)
Christian Doppler arranges to have trumpets played from a passing train. The ground-observed pitch was higher than that played, demonstrating the Doppler Shift (1845)
Guglielmo Marconi demonstrates that radio signals can travel between two points separated by an obstacle. Marconi's servant is behind a hill 3 kilometers away and fires his rifle upon receiving the signals (1895).
Arthur Eddingtonleads an expedition to the island of Principe to observe a total solar eclipse. This allows for an observation of the bending of starlight under gravity, a prediction of Albert Einstein's Theory of Relativity. It was confirmed (although it was later shown that the margin of error was as great as the observed bending) (1919)
