If we ponder over which physical quantity is measured the most, then it would be none other than temperature. Even slight changes in the value of temperature impacts the ecological processes of the world in a significant way. Before the invention of temperature measuring devices, hot and cold could be perceived only by sensory organs. The devices to measure temperature have been slowly developed since the times of Galileo, who first invented the documented thermometer in about 1592. The modern-day thermometers are based on Fahrenheit and Celsius scale units. Fahrenheit Scale The 18th century was a significant year in the history of temperature measuring devices, when Daniel Gabriel Fahrenheit, a German instrument maker, invented the mercury and alcohol thermometers. The limitations of the alcohol thermometer were overcome by the mercury thermometer. In the Fahrenheit scale, Gabriel Fahrenheit based on his recordings, experiments, and data, concluded 0 as the temperature of his mixture; 32 as the temperature of water and ice; and 212, as the boiling point of water. He arrived at the number 212 to be the boiling point of water by chance. Celsius Scale The credit for the development of Celsius scale goes to Anders Celsius, an astronomy professor in Sweden, who introduced a new temperature scale in 1741. As per his calibrations, 100 was the temperature at which water boiled and 0 was the temperature at which water froze. Shortly after the death of Andres, the name of the scale was changed to centigrade scale. There is a slight difference in Celsius and centigrade scales (a difference of 0.1 degrees in readings), however, for day-to-day use, both are almost same. Units of Temperature Most modern-day thermometers and instruments use either the Celsius or Fahrenheit scale. The difference between the freezing and boiling points on the Fahrenheit scale is 180 degrees while for the centigrade scale it is 100 degrees. As we can see, temperature has to be represented on some scale, and without any calibrations it is not possible to measure temperature accurately. The size of the temperature unit and the zero point of the scale is necessary for the thermometer to give correct readings. Fahrenheit to Celsius Conversion

Point on Thermometer	Celsius Scale	Fahrenheit Scale
Boiling Point Water	100º	212º
Freezing Point	0º	32º
Absolute Zero	-273º	-460º

The two scales, Fahrenheit and Celsius, are connected through the simple formulas by the help of which we can convert the scales into one another. The Conversion Formula

Fahrenheit to Celsius Conversion:

ºC = 5/9 (ºF - 32)

Celsius to Fahrenheit Conversion:

ºF = 9/5 (ºC) + 32

The Fahrenheit to Celsius conversion factor 5/9, comes after dividing 100 by 180. That is the range between the ice point in the Celsius and Fahrenheit scale. A simpler way of calculating this is as follows: We know that 9/5 = 1.8 = (2.0 - 0.2) = 2(1 - 0.1). This means that if you have to convert degree Celsius to Fahrenheit then you need to double the given ºC value, subtract 10%, and add 32 to it. Let's understand this by an example: Convert 344 ºC to ºF by the above shortcut. As mentioned above, 344 ºC = Double (ºC value) - 0.1(subtract 10%) + 32 = 2(344) - 0.1 (2) (344) + 32 = 651.2 ºF What is the common point to both Celsius and Fahrenheit scales? Well, the point -40 ºC is common to both, and so we can derive some more alternative Fahrenheit conversion to Celsius conversion formulae that are as follows: ºC = (ºF + 40º) 5/9 - 40º ºF = (ºC + 40º) 9/5 - 40º For example, 150 ºF = ?ºC, ºC = (150 + 40) 5/9 - 40 = 65.56 ºC (approximately) The conversion from Celsius to Fahrenheit or vice versa just involves transferring the variables on the left and right side of the equation and putting the given values. Have fun studying them!