Melting Butter, Poisonous Mushrooms and the Strange History of the Invention of the Thermometer
BY PHIL JAEKL
In the early 17th century, during the the Scientific Revolution, when the frontiers of discovery were marked by new ways to quantify natural phenomena, Galileo Galilei was forging new, innovative and empirically based methods in astronomy, physics and engineering. He also got humanity started toward a lesser known but crucial advance: the ability to measure heat.
During this era, a flurry of measuring devices and units of measurement were invented, eventually forging the standard units we have in place today. Galileo is credited with the invention of the thermoscope, a device for gauging heat. But it’s not the same as a thermometer. It couldn’t measure—meter—temperature because it had no scale.
Around 1612, with a name so nice he used it twice, Venetian scholar Santorio Santorio made crucial conceptual advances to the thermoscope. He’s been credited with adding a scale—an advancement about as fundamental as the invention of the device itself. The early thermoscopes basically consisted of a vertically oriented glass tube with a bulb at the top and a base suspended in a pool of liquid such as water, which ran up a length of the column. As the temperature of the air in the bulb increased, its expansion changed the height of the liquid in the column. Santorio’s writings indicate that he set the maximum by heating the thermoscope’s bulb with a candle flame, and he set the minimum by contacting it with melting snow.