Fahrenheit Celsius Rankine

Temperature megaConverter #9

Introduction and Overview
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Temperature is a measure of the thermal activity in a substance. There is a point, however, at which all thermal activity stops. This point is called absolute zero and is the coldest a temperature can get. Extremely cold temperatures have become important in recent years because the properties of certain materials exhibit very useful changes as the materials' temperature approaches absolute zero.

All substances expand and contract somewhat due to changes in thermal content. Thermal meters or thermometers take advantage of this expansion and contraction and are able to use it to gauge the temperature at any time. A scale can be set up that follows the movement of a liquid or a metal as it expands or contracts.

For a more comprehensive treatment of measurements, find "NTC’s Encyclopedia of International Weights & Measures" by William D. Johnstone at your local library. For a better discussion of temperature, see any college physics textbook.

* Much of our written history still refers to things in common units. The Bible does not refer to meters or kilograms, but to cubits and stadia, or shekels and drachma. Wouldn't it be nice to know what they were talking about way back then? Now you can use megaConverter! For a more complete listing of ancient, foreign, and obsolete measures, download our 'megaSpreadsheet' of conversions in MS Excel format.

Glossary of Conversions:

The first temperature scale in common use approximated 0 to 100 degrees as the normal range of earthly temperatures. This scale eventually fixed 100 degrees at the normal human body temperature. It turns out that the normal human temperature is somewhat less, around 98.6. It is believed that the inventors of the scale may have made their observations in a hospital and may have used sick people to set their scale. The zero point of the scale was set at the coldest they could then generate in a laboratory using ice and salt. Many people of the world still use the Fahrenheit system, although it is slowly being replaced by the Celsius, or centigrade system.

The Celsius system was devised as a standard where the zero and 100 degree points were more practical fixed physical constants. 100 degrees is the boiling point of pure water at a certain pressure. Zero degrees is the freezing point of pure water at some specific pressure. Thus, the break points of the new scale are based on the characteristics of arguably the most important substance on the planet.

Rankine, Kelvin
Physicists needed a way to represent absolute zero as the zero point on a temperature scale to make thermodynamic calculations come out right. So they just took the existing Fahrenheit scale and lowered it so that zero was now absolute zero, and called it the Rankine scale. The degrees were the same size, they just started at a different zero. Later, when the Celsius scale was invented, they did the same thing to it and called the new absolute zero based scale the Kelvin scale.

Note: Because of round-off errors, converting from very large units to very small units or vice-versa may not be accurate (or practical). Conversion factors can be found by converting a quantity of 1 unit to another unit several steps above or below the first. You may need to string several conversion factors together to find the factor from a very large unit to a very small unit, and then you can use a calculator with sufficient digits to find your answer.