Temperature
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INFORMATION
PAGE
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 "NTCs 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:
Fahrenheit
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.
Celsius
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.
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