Temperature is a measure of heat energy in an object. Temperature is a relative measurement so scales need to be based on a reference point to measure temperature accurately. There are four scales commonly used to measure temperature: Fahrenheit (°F) scale, Celsius (°C) scale, Kelvin (K) scale and Rankine (ºR) scale. Each of these scales uses a different set of increments based on different reference points.

Fahrenheit

The Fahrenheit scale was developed by Daniel Gabriel Fahrenheit he was a German physicist who invention the alcohol thermometer in 1709 and the mercury thermometer in 1714. The Fahrenheit scale was developed in 1724.Fahrenheit scale is based on the temperature of an ice-water-salt mixture which was set at 0 degrees. The temperature of an ice-water mixture with no salt was set at 30 degrees and the temperature of the human body was set at 96 degrees. Using this scale, the temperature of boiling water is 212°F on the Fahrenheit scale. Later he moved the freezing point of water from 30°F to 32°F, resulting in the difference between the freezing and boiling points of water is an even 180 degrees.

Celsius

The Celsius scale was developed by Anders Celsius he was a Swedish astronomer who created the centigrade scale in 1742. The two reference points used by Celsius was the melting point of ice and the boiling point of water he then divided the difference in temperature by 100. The centigrade scale was renamed after his death to the Celsius scale. On the Centigrade or Celsius scale the freezing point of water is 0°C and the boiling point of water is 100°C. The Celsius scale is more commonly used in scientific research because of its ten base format which is the same as the International System or SI metric measurement system.

Kelvin

The Kelvin scale was developed by a Scottish physicist named Lord William Kelvin in 1854. The Kelvin scale is based on the theoretical temperature of absolute zero. At this temperature all molecular movement stops and no energy can be detected. Theoretically the zero point on the Kelvin scale is the lowest possible temperature that exists in the universe. The Kelvin scale uses the same divisions as the Celsius scale except it resets the zero point to absolute zero, which would equal -273.15ºC on the Celsius scale. This makes the freezing point of water 273.15 Kelvins and 373.15 Kelvins is the boiling point of water. As there are no negative numbers on the Kelvin scale it is very useful when measuring extremely low temperatures for scientific research. The Kelvin scale is a standard International System unit of measurement used commonly in scientific measurements.

Rankine

The Rankine scale was proposed by a Scottish engineer and physicist called William John Macquorn Rankine in 1859. Like the Kelvin scale it is also based on the theoretical temperature of absolute zero. Also like the Kelvin scale Zero Rankin is absolute zero but the Rankin scale uses the degree as defined by the Fahrenheit scale. This makes the freezing point of water 459.67 degrees Rankine.



This can seem very confusing but each of the four temperature scales allows us to measure heat in a slightly different way. A measurement of any of the four scales can be easily converted to another scale using the converters or formulas listed on this site.