Thermometer

Lore & Background

The invention of the thermometer cannot be attributed to any single person or date with certitude; it is best viewed as an evolving technology. Early pneumatic devices by Philo of Byzantium (3rd century BC) and Hero of Alexandria (10–70 AD) provided inspiration. The first clear diagram of a thermoscope was published in 1617 by Giuseppe Biancani; the first showing a scale and thus constituting a thermometer was by Santorio Santorio in 1625.

The word 'thermometer' first appeared in 1624 in La Récréation Mathématique by Jean Leurechon. The first description of a sealed liquid-in-glass thermometer was published by Joseph Solomon Delmedigo in 1629. Ferdinando II de' Medici produced the first modern-style thermometer around 1654. Daniel Gabriel Fahrenheit invented a reliable mercury thermometer in 1714.

Anders Celsius proposed a scale in 1742. The first physician to use thermometer measurements in clinical practice was Herman Boerhaave (1668–1738). Sir Thomas Clifford Allbutt invented a clinical thermometer in 1866 that produced a reading in five minutes.

Reader's Guide

A thermometer measures temperature. For accurate comparison, thermometers must conform to an agreed scale. The most recent official temperature scale is the International Temperature Scale of 1990, extending from 0.65 K to approximately 1358 K. Early thermometers were sensitive to air pressure; sealed liquid-in-glass thermometers solved this. Mercury and alcohol are common liquids used in thermometers.