*** 20th Anniversary: 2003 to 2023 ***

Anders Celsius Thermometer

A part of our heritage

Have a look at this old photograph of what may be the original Anders Celsius Thermometer. This is showing a scientist's creation that he created 5 years before he died.  Courtney Adamen of Auburn Maine provided this image and caption to StuffintheAir.com

Anders Celsius was an astronomer, physicist, and mathematician in Sweden who lived from 1701 to 1744. He became well-known for starting the Uppsala Astronomical Observatory, and even more so for coming up with the Celsius temperature scale, which is shown on the thermometer picture above.

Temperature scales have normally been defined by picking two points of interest, comparing their temperatures and sub-dividing it go get the scale. Any two will do. Body temperature or anything else that is consistent. That may have been a little more difficult to find.

A thermometer measures the temperature of an object or environment by using a temperature-sensitive material like mercury or alcohol.  With temperature changes, materials expand and contract, which is how thermometers work.

Mercury thermometers have a glass tube filled with mercury and sealed at both ends.  As the temperature changes around the thermometer, the mercury inside the tube expands or contracts, moving up or down.  There's a scale on the outside of the thermometer that corresponds to the height of the mercury column inside.

In 1742, our hero invented the Celsius thermometer.  Daniel Gabriel Fahrenheit had invented the mercury thermometer in the early 18th century, which was the basis for the Celsius thermometer.

It's better to have two temperatures that are further apart for defining the scale, rather than too similar. The idea of using the boiling and freezing points of water may seem a little obvious now but that probably wasn't always the case. They are not perfectly consistent, but the the greatest contribution from Celsius himself was finding a way to make them usable.

Celsius, maybe?

Actually, the scale he invented had zero for boiling and 100 for freezing (for water). Celsius also noted that while he could determine the variations in the boiling point of water, dependent on ambient pressure, the freezing point did not vary significantly at all.

Meanwhile another scientist, Jean-Pierre Christin, came up with zero for freezing and 100 for boiling and had a matching thermometer designed.  The Celsius scale was originally called the centigrade scale, which means "consisting of 100 degrees" in Latin.  

He based his scale on the freezing and boiling points of water because he thought they were universal reference points.  Using a decimal system also made it easier to calculate and measure temperature differences.

In most countries around the world, the Celsius scale has become the standard unit of temperature measurement since Celsius invented this thermometer and temperature scale.

He was in good company...

A lot of new inventions and technologies were developed in the 18th century which represented scientific breakthroughs.  Here are some science inventions:

- In the late part of that century, Scottish engineer James Watt invented the steam engine, which revolutionized transportation, industry, and agriculture.

- The electric battery was invented by Italian physicist Alessandro Volta in the late 1700's, which led to the study of electricity and modern electrical technology.

- In the mid-18th century, Swedish botanist Carolus Linnaeus developed a system for classifying living organisms that biologists still use.

- Around that same time, British chemist Joseph Priestley discovered oxygen, which revolutionized our understanding of air and respiration.

- English doctor Edward Jenner developed the smallpox vaccine in the late 1700's, which was a major breakthrough.

- Scottish engineer William Murdoch invented gas lighting in the late 18th century, which revolutionized street lighting and allowed people to work and read after dark.

I'm sure there are more, but this is a good start.

Want to learn more about this Anders Celsius Thermometer inventor?

The temperature measurement work Celsius did wasn't the only thing he did in astronomy.  He also observed the aurora borealis, studied the shape and size of the Earth, and designed an instrument to measure star positions called the zenith sector.  From 1730 until 1744, Celsius was the director of the Uppsala Astronomical Observatory in Sweden.  Although Celsius is best known for his work on temperature measurement, he contributed to a lot of fields.

More details can be found on Wikipedia: https://en.wikipedia.org/wiki/Anders_Celsius

I have written more about him and his thermometer development on this page.  Thank you for this inspiration, Courtney.

What has happened lately?  The idea behind thermometers is to detect temperature changes in a material and converting them into something readable.  In modern times digital thermometers are primarily used for this purpose.

In this case, temperature is measured by a thermistor (a resistor whose resistance changes with temperature).  The thermistor changes resistance when it's exposed to a temperature change, and the thermometer's electronics process the electrical signal to display the temperature.

Search this site for more information now.  Somebody liked this photo.  See below.

rare one
by: mia

Anders Celsius Thermometer, the rare one of the great thermometers. I really love to see this in real. Because I have searched a lot for this thermometer but never, found one.

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Thank you to my research and writing assistants, ChatGPT and WordTune, as well as Wombo for the images.