A way of measuring temperature was not invented until 1724. Before that people would say things like its a bit nippy out there or I am too hot I really fancy an ice cream. Yes amazingly you could buy ice cream but you could not say how cold the ice cream was! The invention of the thermometer is credited to Galileo. Yes I know it seems that everything was invented by Galileo or Da Vinci. According to the Galileo project, Galileo had a toy which was a glass bulb with a tube filled with liquid. When the bulb was held in his hand the liquid would warm up in his hand and expand up the narrow tube. At this stage the instrument is called a thermoscope (literally see heat). However with the addition of a scale to the tube we get the first fully fledged thermometer. Unfortunately no body could decide on an appropriate scale. Everybody was using different scales so comparisons between temperatures could not be compared. So one scientist would say that water boils a 63 Smiths while another scientist would say no it boils at 34 Jones.
At this point a clever young man called Gabriel Fahrenheit enters the scene. He was a glassblower who made barometers and altimeters as well as thermometers. He also had a really cool surname so he was bound to famous.
Fahrenheit had the idea to use mercury in his thermometers. This made his thermometers extremely accurate and extremely poisonous, but back in 1724 there was no health and safety getting in the way of scientific innovation.
Fahrenheit then took a mixture of ice, water and ammonium chloride. This was the coldest mixture he could make. Even colder than ice cream. Fahrenheit apparently loved a bit of raspberry ripple. Some websites claim he liked a flake but that was not invented until 1920 so that is definitely not true. Anyway back to the true part of the story. Fahrenheit put his thermometer into his coldest mixture and marked on the thermometer the lowest point it reached. Fahrenheit, unsurprisingly called this 0°F. He then put his thermometer into water which was just beginning to freeze. He called this temperature 32°F. Then for no apparent reason he stuck the thermometer in his mouth and measured the temperature as 96°F. Over the years the scale was refined with the boiling point of water being 212°F and body temperature was adjusted from 96 to 98. With that Fahrenheit was onto a winner. Everybody started to measure temperatures using his scale. Everybody could compare results. This resulted in people finding out that Britain was really cold and the mediterranean was really hot.
Meanwhile at the same time in Sweden (which everybody now knew was very very cold) an astronomer called Andres Celsius came up with his own scale. Celsius put a thermometer in freezing water and marked a line. Then he did NOT stick the thermometer in his mouth. Instead he put it in boiling water and marked another line. Celsius then divided the difference between the two lines 100 times. He did not call his scale Celsius, obviously he was not quite as obsessed with himself as Fahrenheit, though as I noted earlier Fahrenheit is a way cooler name than Celsius. Approximately 32°F cooler!
Andres used the Latin term for 100 which is Cent (like centurion) to call his scale centigrade. Then everybody pretty much ignored his scale until 1948 when the unit was adopted at the 9th General Conference on Weights and Measures.
This conference decides on what unit everybody in the world should use. So everybody in the world started to use the celsius scale except America. So everything seemed alright until a Scotsman no less, decided to change our ideas about temperature completely and come up with another scale.
Kelvin stated that at -273°C molecules would stop moving. So Kelvin called this absolute zero or infinite cold. Infinite cold is a much better name but unfortunately nobody uses it.
At the 10th General Conference on Weights and Measures Kelvin was adopted as the absolute thermodynamic temperature scale for science.
With the Kelvin scale scientists started to try to achieve lower and lower temperatures. Two rival scientists James Dewar from Scotland and Heike Onnes from Holland were involved in trying to liquify the gases helium and hydrogen. Dewar succeeded in liquifying hydrogen by lowering the temperature to 21K. Onnes then liquified helium by lowering the temperature to 4K only four degrees above absolute zero. Onnes received the Nobel prize for his achievement. Onnes then discovered superconductivity in metals at near absolute zero. This means that metals show no resistance to an electrical current. Onnes work described a quantum mechanical effect which was called superconductivity.
So from Galileo's little toy, the thermometer transported scientists on a journey that led to the discovery of the quantum mechanical effect of superconductivity and really nice ice cream.