What Happened to Centigrade? Confusion Over the Celsius Temperature Scale…

thermometer When I started teaching elementary school (as a second career in 1995), I was very surprised to find all the new textbooks now referring to the centigrade scale as the Celsius scale. Of course they are the same thing, but I wondered why the textbooks were now using this term when I had never heard it growing up. Now, I know why.

The short answer is that people continue to call a thing by the same name they, themselves, learned while growing up.  Most adults, and just about everyone in academia through the 1980s, grew up hearing “centigrade” and continued to use that term with their own students throughout high school and university.

The new name, “Celsius,” disturbed me ever since I began hearing it in the mid-1990s; but now that I know there was an actual reason for the name change, it no longer bothers me.  A unit of measurement, called a “grade,” was actually in use.  Therefore, in 1948, the Conference General de Pois et Measures (in France) decided to change the name of the scale to “Celsius.”

The International System of Units

The International System of Units

A second reason for the change in name was that the Conference General de Pois et Measures decided that “All common temperature scales would have their units named after someone closely associated with them; namely, Kelvin, Celsius, Fahrenheit, Réaumur and Rankine.”

The change in elementary-school textbooks began to take place around 1968, and during the 1970s, as districts began to replace their former textbooks.  In the meantime, parents, scientists, and college professors continued to use the name they had grown up with.  Only students born in the 1970s and later would have grown up calling the scale “Celsius.”  (I continue to catch myself saying “centigrade” to my own students.)

In England, the BBC Weather did not begin using the term Celsius until 1985, and the word centigrade continues to to be commonly used in England, according to some sources.

Swedish Astronomer Anders Celsius (1701-1744)

Swedish Astronomer Anders Celsius (1701-1744)

The centigrade scale was known as such from 1743-1954.  In 1948, the scale was renamed the Celsius scale, after the Swedish astronomer Anders Celsius (1701-1744) who developed a SIMILAR scale (but not actually the same scale).  Interestingly, Celsius’ original scale was the reverse of today’s scale; “0″ indicated the boiling point of water, while “100″ indicated the freezing point of water.

Swedish Zoologist and Botanist Carolus Linnaeus(1708-1777)

Swedish Zoologist and Botanist Carolus Linnaeus(1708-1777)

The Swedish zoologist and botanist, Carolus Linnaeus (1707-1778), remembered for giving us the basis of taxonomy (classification of living things into genus and species), reversed Celsius’ original scale so that “0″ indicated the freezing point of water, while “100″ indicated the boiling point. As the older generations retire and pass away, the new name change will become universal.  It seems to take about three generations for a name change to really become universally accepted in society.

–Lynne Diligent

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5 Responses to “What Happened to Centigrade? Confusion Over the Celsius Temperature Scale…”

  1. Gthomas Says:

    Interesting. Thanks!

  2. RainDancer Says:

    I’ve never paid attention to this, but I think we still use both Centigrade and Celsius in Arabic.

    Thanks Lynne

  3. Leslie Wilson Says:

    Kelvin, not Celsius. is the SI unit, I have sometimes slipped and said centigrade instead of Celsius. That causes confusion, so Celsius should be the relative (to water) unit. Ultimately, they need to understand why Kelvin in the.theoretical and absolute temperature scale.

  4. Joel Palmer Says:

    The other reason for the change might be that the Fahrenheit scale is also a “centigrade” (centi=100 grade=degree) scale. Fahrenheit divided the range between the coldest temperature he could make consistently, the freezing point of a specific concentration of salt water and another consistent temperature, human body temperature, by 100. His measurements were a little off due to the level of technology so human body temperature ended up at 98.7 rather than 100. So his was a centigrade scale as well. It Jan be shown that the Kelvin scale is also a “centigrade scale albeit with a different 0 refer ant than the Celsius scale. .

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