# HEAT AND COLD

## MEASURING TEMPERATURE

### How was the Fahrenheit scale developed?

The temperature scale still in use in the United States (while the rest of the world uses the metric system of Celsius), is named after German engineer and physicist Gabriel Fahrenheit (1686-1736). Fahrenheit developed his scale after visiting Danish astronomer Ole Christensen Romer (1644-1710) in 1708. For his experiments, Romer was using an alcohol thermometer upon which he had marked a scale from zero degrees (the lowest temperature he could achieve in his laboratory using a mixture of ice, water, and salt) to 60 degrees, the boiling point of water. This system actually mimics the basic idea behind the Celsius scale.

While Fahrenheit left no records as to why he chose certain high and low points on his thermometers, there has been speculation on this matter. It is known that he used his own body temperature as the high point on his thermometer, but he marked this temperature as 96 degrees. Some believe he chose this number because it was easily divisible by twos and threes. For his zero degree mark he used Romer's figure. Fahrenheit later determined that water normally froze at 32 degrees on his scale and boiled at 212 degrees.

### What is the Kelvin temperature scale?

The Kelvin scale is typically used in laboratories dealing with extremely cold temperatures. Zero degrees Kelvin indicates absolute zero, which is the point at which molecular motion stops. The scale is named after the 1st Baron Kelvin, William Thomson (1824-1907), who was a British engineer and physicist. Thomson developed the absolute thermometric scale, which used degrees Celsius as its increments and had absolute zero being -273°C (the actual figure has now been deter

Thermometers in the United States display both Celsius and Fahrenheit temperatures, which saves people the trouble of having to convert degrees.

mined at -273.15°C. Such extremes are rarely needed in meteorological studies, however.

### Why was the name of the Centigrade scale changed to Celsius?

The centigrade temperature scale was created by Swedish astronomer Anders Celsius (1701-1744) in 1742. He was determined to create a new temperature scale as an international standard to be used by scientists. To do so, he wanted the degrees of zero and 100 to be set under conditions easily reproduced in the laboratory: and those were the freezing and boiling points of water. Because the two extremes were divided into 100 degrees, he named it the centigrade scale. To honor his accomplishment, the Ninth General Conference on Weights and Measures officially changed the name to Celsius in 1948. Fortunately, since both words begin with the same letter, °C did not have to be changed as well.

### How do I convert Fahrenheit to Celsius or Kelvin?

Fahrenheit and Celsius are two common temperature scales used throughout the world. Temperature in Fahrenheit can be converted to Celsius by subtracting 32 and multiplying by five; divide that number by nine and you have Celsius. Conversely, you can convert Celsius to Fahrenheit by adding 32, multiplying by nine and finally dividing by five. Kelvin, a system used by scientists, is based on the same scale as Celsius. All you have to do is add 273 to your Celsius temperature to obtain Kelvin. Zero degrees Kelvin is negative 273°C.

### What is a low high temperature and a high low temperature?

When meteorologists look at daily temperature, there is always a low and a high temperature for each day. If the high temperature is the coldest high temperature for that day or for the month on record, you have a new record—a new low high. Conversely, if the low temperature for a day is quite warm and breaks records, that's a new high low!