The Fahrenheit scale, although very popular in the US has an intriguing history and varied worldwide adoption scenarios. While the US sticks to it, most other countries do not and its usage is also often combined with other scales in various parts of the world.
The Fahrenheit scale was developed by Daniel Fahrenheit who born in the year 1686 and lived until 1736. The Dutch physicist, engineer and glass blower had actually performed precise calculations in the early 18th century to arrive at the absolute zero of the Fahrenheit scale and although it may appear random, the scale was based on solid scientific choices that make the number 32 (degree)°F the freezing point of water on the scale.
He wanted to create a temperature scale that defined fixed temperature points including the starting (absolute zero) and three important points which include the absolute zero, which is the coldest possible temperature, the temperature of freezing water and also the temperature of the human body. An older system invented by Ole Christensen Romer, twenty years earlier formed the basis of these choices.
When water is placed at sea level and under standard atmospheric pressure, it boils at approximately 212 (degree)°F according to the original scale exactly 180 higher than the freezing point of water. Similarly, the human body temperature is difficult to precisely determine as it varies depending on various factors such as the age of the person, the time of the day, the body's rate of metabolism etc. However, this too was adjusted for accuracy from the original 96 (degree)°F to 98 (degree)°F.
The Fahrenheit scale is now defined by only the two fixed temperature points of the freezing point of water into ice, which is defined as 32 (degree)°F and the point at which water boils into water vapor, which is defined 212 (degree)°F. Both these temperature points are considering sea level and the standard atmospheric pressure.
In comparison, although the Celsius temperature scale came into being at about the same time, it was not widely adopted for several decades. Its adoption finally accelerated when several countries around the world switched to the metric system in the 1960-70s. Until the late 1960s the Fahrenheit scale was used in the meteorological domain as well as the industrial establishment and the medical community in most English-speaking nations but in the 1970s almost all these nations switched to the Celsius scale. This change was so rapid that at the end of the 20th century, the Fahrenheit scale was only officially used in the United States of America and a few smaller regional states.
Canada has legislation that favors the Celsius scale but also maintains the legal definitions for the older imperial units. Weather reports in the country usually include the Celsius scale and a few references to the Fahrenheit temperatures. Even thermometers used in Canada show reading on both Celsius and Fahrenheit scales.
On the other hand, the European Union has made it compulsory to use degrees Celsius when using a temperature reference in any public announcements and communications be it health, administrative or the public safety departments. It only allows the use of the Fahrenheit scale temperature points as a supplementary unit.
In the UK certain unregulated sectors including journalism, follow no fixed pattern and references to both scales appear together or side by side in the written material. While some newspapers use the Celsius temperatures first on their weather page, followed by the Fahrenheit temperature, in brackets, other newspaper may not use the Fahrenheit scale at all on their weather reports and some go as far as to have several metrics listed and accompany it with a Temperature Scale conversion table.
For the Fahrenheit scale:
Water's freezing point = 32 (degree)°F
Water's boiling point = 212 (degree)°F
Therefore, One degree on Fahrenheit scale = 1180 of this interval.
For the Celsius scale:
The difference between the freezing point and the boiling point of water = 100 degrees.
Therefore an interval of 1 (degree)Fahrenheit = an interval of 5/9 (degree)Celsius. Absolute zero on the Celsius and Fahrenheit scales are −273.15 (degree)C and −459.67 (degree)°F respectively. Therefore an exact formula for conversion would be: the temperature T in degrees Celsius or (degree)°C is equal to temperature T in degrees Fahrenheit or (degree)F minus 32, times 5/9. This is the simplest formula for converting temperatures between the Celsius and Fahrenheit scales.