Joan Welsh, age 12, of Laconia, N.H., for her question:
WHEN WAS THE THERMOMETER INVENTED?
Galileo, an astronomer, made the first thermometer in 1593. His rather crude instrument, which was then called a "thermoscope," was not very accurate.
The first accurate thermometer was invented in 1641. This model used alcohol.
The thermometer was continually improved upon until 1714 when Gabriel Fahrenheit, a scientist, built a mercury thermometer of the type which is still used today.
Fahrenheit was a German physicist. His thermometer determined three fixed temperatures: zero degrees for the freezing point of ice, salt and water, 32 degrees as the freezing point of pure water and 96 degrees for the normal temperature of the human body.
Later experiments proved the body temperature to be 98.6 degrees Fahrenheit rather than 96.
The Celsius scale of.the thermometer came about through the work of Anders Celsius in 1742. It was changed and improved a few years later.
In 1954, the United States Army announced the invention of an electronic clinical thermometer by Col. George Perkins. It was a stainless steel probe connected to a mercury cell battery and a small meter.
Liquid in glass thermometers work on the principle that liquids increase in volume as their temperatures rise. The most common thermometer, and the one most widely used in the home, is the mercury in glass type.
The mercury in glass thermometer is made up of a glass tube with a small but uniform bore, a reservoir or bulb at the bottom and a sealed end at the top. The bulb and part of the tube are filled with mercury.
When the temperature being measured goes up, the volume of the mercury increases more than the capacity of the glass bulb. Therefore, the mercury rises in the tube.
When the temperature and the substance whose temperature is being measured have the same temperature, the mercury ceases to rise.
Temperature scales used on thermometers today can include either the Celsius or Fahrenheit, or both. Some use a third scale, called the Reamur, which is rapidly passing out of use. It has 80 divisions between the freezing point (zero degrees) and the boiling point (80 degrees),
The Fahrenheit scale has 180 divisions between the freezing point of water (32 degrees Fahrenheit) and the boiling point of water (212 degrees Fahrenheit). This scale is the one in general use in most English speaking countries.
The Celsius scale has 100 divisions between the freezing point of water (zero degrees Celsius) and its boiling point (100 degrees Celsius). The Celsius scale is used throughout the world in scientific work. This scale is used for all temperature measurements in countries where the metric system is standard.