Fahrenheit

The Fahrenheit scale is a way to measure temperature that was created by a scientist named Daniel Gabriel Fahrenheit in 1724. He used special points to mark the scale, like the temperature when water freezes and the temperature of the human body. Over time, these points were changed to make them easier to use. Today, pure water freezes at 32 °F and boils at 212 °F when measured at normal air pressure.

For many years, the Fahrenheit scale was very important, especially in the United States. It is still used there and in a few other places like Palau, the Federated States of Micronesia, and the Marshall Islands. Some other countries, like Antigua and Barbuda and the Bahamas, also use it sometimes alongside another temperature scale called Celsius.

Most countries around the world now use the Celsius scale instead. It was created later than Fahrenheit and is easier for many everyday uses. Still, understanding the Fahrenheit scale helps because you will see it used in weather reports, cooking, and other places in some parts of the world.

Definition and conversion

On the Fahrenheit scale, water freezes at 32 °F and boils at 212 °F when the air is pressing down normally. This means there are 180 steps between freezing and boiling on this scale. Each step on the Fahrenheit scale is a little smaller than on the Celsius scale, where water freezes and boils are only 100 steps apart.

The two scales cross at -40; -40 °F is the same as -40 °C. Absolute zero, the coldest possible temperature, is 0 K, which is -273.15 °C or -459.67 °F. The Fahrenheit scale uses the same size steps as the Rankine scale but starts at absolute zero, just like Kelvin starts at absolute zero for the Celsius scale.

History

Fahrenheit created his temperature scale in 1724. He chose two important temperature points to build his scale. The first point, 0 °F, was based on a special mix of ice, water, and a salt called ammonium chloride. This mix stays at a steady, very cold temperature.

The second point, 96 °F, was close to the temperature of a human body. He also marked 32 °F as the temperature where ice and water meet without any added salts. Later, the scale was changed so that water freezes at exactly 32 °F and boils at 212 °F. This made it easier to use for everyday temperatures.

Usage

The Fahrenheit scale was the main way to measure temperature in English-speaking countries until the 1960s. After that, most of these countries started using the Celsius scale instead, except for the United States.

Today, Fahrenheit is still used in the United States for everyday things like weather reports, cooking, and freezing food. However, scientists in the U.S. use Celsius and Kelvin for their research.

United States

In the early 1900s, some people thought Fahrenheit was easier to understand for talking about outdoor temperatures in places with mild weather. For example, 100 °F feels like a hot summer day, while 0 °F feels like a cold winter day.

Canada

Canada has laws that support the international system of units, but people there still use Fahrenheit on ovens. Weather reports in Canada are usually in Celsius, but sometimes Fahrenheit is mentioned, especially when broadcasting to places near the U.S. border. Thermometers sold in Canada often show both Celsius and Fahrenheit.

European Union

In the European Union, temperatures for important purposes like health and safety must be given in Kelvins or Celsius. However, Fahrenheit can sometimes be used as an extra measure alongside Celsius.

United Kingdom

Most people in the United Kingdom use Celsius for temperature. But sometimes, Fahrenheit appears in newspapers, especially for higher temperatures, because it can sound more dramatic. For example, "94 °F" might sound hotter than "34 °C."

Unicode representation of symbol

Unicode has a special symbol for the Fahrenheit degree, shown as ℉. This symbol is kept for compatibility with older systems, but Unicode suggests using the degree sign ° followed by the letter F instead, as this is preferred and should be treated the same for searching.