Anders Celsius: Centigrade Thermometer, 1742
A Swedish astronomer who founded the Uppsala Astronomical Observatory, Anders Celsius served as Professor of Astronomy at Uppsala University in Sweden. In 1742, he proposed a new method of measuring temperature. Grading his system from zero degrees for boiling water and 100 for the freezing point, he named it the Centigrade Scale.
He kept meticulous records of careful experiments, determining scientifically how to measure the boiling and freezing points of water. He proved water freezes at the same temperature regardless of barometric pressure or latitude, establishing ways to determine variations on the boiling point from barometric differences.
Carl Linnaeus inverted the Centigrade scale in 1745, with zero degrees as water’s freezing point and 100 the boiling point. The Centigrade scale was renamed the Celsius Scale to honor Anders Celsius, who died the year before.
James Watt: Power Measurement, 1782
By the time he developed a unit to measure the rate of work performed over time, Scottish engineer James Watt was already famous for brilliant innovations in early steam engines. He was a prolific inventor in multiple disciplines, patenting the double-action engine, the direct copy machine, a steam pressure indicator and the rotary engine.
Watt made his fortune on a new steam engine design, making steam engines practical to pump water out of mines. Refining the design over years, Watt’s steam engines became the industry standard.
Through careful experimentation and measurement, Watt developed the horsepower unit (hp) by determining that a horse could pull 33,000 lbs one foot in one minute. The international standard unit for power and energy measurement is named the Watt (W) in his honor.
Alessandro Volta: Electric Battery, 1799
Alessandro Giuseppe Antonio Anastasio Volta was an energy production pioneer who discovered methane gas and invented the galvanic cell method for continuous electric current. Volta was Physics Professor at the Royal School of Como when he first isolated methane gas in 1776.
He was interested by Luigi Galvani’s 1791 frog leg experiments, in which Galvani had provoked a twitching response from dead frog legs by attaching metal strips to each other and to the legs. Galvani thought he had proven “animal electricity.” Volta realized it was simply the nervous system responding to an electric current.
Volta began experimenting with a way to produce electricity without animal tissue. Checking for current by touching two metal strips to his tongue, Volta realized he could use an electrolyte to stimulate electron flow. In 1799 he invented the Voltaic Pile. The device inspired a flood of inventions and patents. Napolean Bonaparte bestowed a count’s title on Volta in 1810. The Volt (V) is the standard international symbol for electrical potential.
Ernst Mach: Shock Waves, 1887
The Mach Number (M) is a ratio between the speed of a subject and the speed of sound. An airplane traveling two and a half times the speed of sound is going 2.5M. Mach devised the ratio as part of his work in the study of shock waves. Mach’s work in ballistics established fluid dynamics as a new branch of physics.
Ernst Mach served 28 years as Chair of Experimental Physics at Charles University. He discovered that the human inner ear regulates balance and in 1887, captured an iconic photograph of a bullet breaking the sound barrier. His principles and formulas for ballistic shockwaves define how a compressed disk of air forms in front of an object moving faster than sound.
These scientists made their marks on history, literally inscribing their names in the annals of history. As long as people need to measure these quantities, the names of these scientists will continue to live on.