Dinesh Lahotim Founder, Edugenie [email protected]
This section will carry everything related to Science, Technology, Engineering and Maths (STEM).
Any store and public place these days welcomes us with a thermal scanner that can measure our body temperature accurately and without making any physical contact, all in a matter of seconds. Just like any other modern-day device, thermometers have a long and interesting story of their own.
There are two important aspects in the history of development of thermometers – the device itself and also the scale attached to it.
Firstly, let us talk about the device. Thermometers measure temperature by using elements that change in some way when they are heated or cooled. In a mercury or alcohol thermometer, the liquid expands as it is heated and contracts when it is cooled, so the length of the liquid column is longer or shorter depending on the temperature. Modern thermometers are calibrated in standard temperature units such as Fahrenheit or Celsius, or Kelvin (used mostly by scientists).
Before there was the thermometer, there was the thermoscope – best described as a thermometer without a scale. It could only show the difference in temperatures. In 1593, Galileo Galilei invented a rudimentary water thermoscope, which for the first time, allowed temperature variations to be measured. Today, Galileo’s invention is called the Galileo Thermometer, even though, by definition, it was really a thermoscope. In 1612, the Italian inventor Santorio became the first inventor to put a numerical scale on his thermoscope. It was perhaps the first crude clinical thermometer (a mouth thermometer). Neither Galileo’s nor Santorio’s instruments were very accurate.
Daniel Gabriel Fahrenheit was the German physicist who invented the alcohol thermometer in 1709, and the mercury thermometer in 1714, and the Fahrenheit scale in 1724. The Celsius and Kelvin scales were invented later.
Thermometers were further evolved and converted to digital form. All modern digital thermometers descend from the first medical thermometer invented by Sir Thomas Allbutt. This was the story of the thermometer and the evolution of temperature scale has its own story, which will be covered in the next article.
