Galileo Galilei and the first mechanical thermometer
Galileo Galilei possessed a rare talent for scientific foresight. The great Italian was able to find, even in simple details, the seeds of future brilliant discoveries. So it was with his famous thermobaroscope – the forerunner of the future modern thermometer.
In 1597 he put on public display a large glass sphere, to which a long tube was attached, lowered into a vessel with tinted liquid. And before the gathered spectators, Galileo demonstrated the principle of the new device's operation. Under the influence of heat, the liquid began to «run» along the glass tube. And it became clear to everyone that another invention had been added to the Italian scientist's collection – the air thermoscope.
At the same time, Galileo himself in no way recorded his invention – people learned of it only thanks to descriptions of the device by his students. According to their records, in 1597 Galileo presented an interesting construction – to a small glass sphere he soldered a long tube, also made of glass. Using fire, Galileo heated the sphere, and lowered the end of the tube into a vessel of water. As soon as the sphere began to cool, the pressure decreased as well, and the water in the tube rose. However, this invention was difficult to apply practically in practice – the tube had no scales for measurement. In essence, Galileo simply proved that the temperature of a body and of the environment could be measured, but that this still needed work.
Sixty years later, other Italian scientists took this up. They built the same device, but added beads to the tube and also pumped the air out of the sphere, which was interfering with giving more accurate readings.
Years later, the thermoscope underwent changes again. Now, instead of water, the tube contained…brandy, which made it possible to visually assess the changes. Besides, at zero water froze, but alcohol did not.
Santorio's first mercury thermometer
The famous Italian physician Santorio was the first of his colleagues to conclude that only a healthy person has a constant body temperature. To prove this theory in practice, he set about creating a corresponding device. In 1626 Santorio demonstrated to the venerable scientific public the world's first mercury thermometer.
It was bulky and awkward, but this did not prevent it from performing its main function. At the very bottom of the thermometer was a large sphere, in which liquid pulsed. To it was soldered a fairly wide glass tube with a marked scale. The first people who wanted to measure their temperature instantly felt the heaviness of the sphere when they had to hold it in their hands. Until this thermometer warmed up from the human body's heat to the necessary condition.
Santorio's mercury thermometer was far from perfect. The lack of a precise measurement scale -one of the significant shortcomings of this device gave its opponents grounds to treat the great discovery skeptically.
The modern form from Daniel Fahrenheit
In 1723 it was a German physicist who conceived and developed the now-familiar appearance of the thermometer. At first he filled the tube with alcohol, but later made the choice in favor of mercury.
The invention of the famous Celsius
The year 1742 can rightfully be called fateful: the brilliant solution to this pressing problem was found by the great Swedish astronomer and mathematician Anders Celsius. His famous measurement scale laid the foundation for the creation of the modern thermometer, which we use for all occasions in life. However, by Celsius's definition, 0 degrees meant the boiling of water, and 100 – its freezing.
The measurement scale from Carl Linnaeus and Mårten Strömer
After Celsius's death, these two scientists reversed his measurement scale – 0 degrees became the melting point of ice, and 100 – its boiling point. And everything fell into place. This is the scale we use today.
By the way
Many countries have abandoned the use of mercury thermometers in favor of infrared, electronic, and non-mercury-filled devices (the liquid galinstan is used – an alloy of gallium, indium, tin, and zinc). In 2014 Russia signed the Minamata Convention on Mercury. This means that by 2030 our country will completely abandon the production of mercury thermometers.
