Fahrenheit

Fahrenheit is a method of measuring temperature. It was developed in 1724 by German physicist Daniel Gabriel Fahrenheit (1686–1736). Typically abbreviated as °F, the Fahrenheit temperature scale defines the boiling point of water as 212°F and the point at which water freezes as 32°F. Normal human body temperature (taken orally) registers between 97.3 and 98.6°F.

Early Methods of Measuring Temperature

Prior to the development of the Fahrenheit method, people were aware of temperature differences but had no definitive ways to measure and compare them. Early humans relied on their senses, such as observing the glowing color of heated metal or the bubbling of boiling water, to determine when the proper temperature was reached for working with materials.

While there may have been devices used to facilitate these determinations in prehistoric times, the earliest recorded devices for measuring temperature were called thermoscopes and were developed in the sixteenth century. Italian astronomer and scientist Galileo Galilei (1564–1642) is credited with creating the first such device in 1638. It used the displacement of water in a glass bulb and tube to measure temperature. Galileo and others continued to work with the idea of using the displacement of various liquids within glass to measure temperature for many years. One of the most common of such devices was known as the Galileo thermometer, also called the Florentine thermometer. It had small blown glass globes filled with colored liquids that were sealed in a glass tube filled with a clear liquid. Each globe was weighted with a metal tag labeled with a temperature. The globes would rise or sink inside the larger tube depending on the temperature of the air around it, and the placement of the globes revealed the room temperature.

Development of Fahrenheit System

One of these colorful thermometers, which are still made today as a conversation item, sparked the development of the Fahrenheit system. It was named after its developer, Daniel Gabriel Fahrenheit. Fahrenheit was born in Poland in the city now known as Gdansk. The oldest of five siblings, Fahrenheit was fifteen when his parents died after consuming poisonous mushrooms, and he was apprenticed to a merchant from Amsterdam by leading citizens in Gdansk who were responsible for the children’s wellbeing.

Fahrenheit was not happy with this situation and, according to letters sent by the Gdansk elders who made the arrangements, he responded by stealing and engaging in other behavior they deemed so bad they declined to put it in writing. By the time he was twenty, they arranged to have him shipped off with the East India Company. This sent Fahrenheit on the run through Europe until he was old enough to be considered a legal adult at the age of twenty-four.

While Fahrenheit had no interest in becoming a merchant, his time in Amsterdam did expose him to the Galileo, or Florentine, thermometers, which fascinated him. He was intrigued enough to borrow against his inheritance to try to improve the devices. The original thermometers were calibrated to a low and high point on a particular day in a particular location. Fahrenheit wanted to standardize this and came to understand that the secret to this was finding liquids that reacted predictably at specific temperatures.

Over time, Fahrenheit developed a measuring system that targeted three specific temperature points: the freezing point of water, the boiling point of water, and the normal temperature of the human body. He used a basic system divided into twelve points with eight subdivisions between each, which accounts for the somewhat unusual points of 32° for the freezing point of water, 98° for body temperature, and 212° for the boiling point of water. Fahrenheit was twenty-eight years old when he was able to display two thermometers that gave the same readings at the same time, something no one had ever accomplished before.

Fahrenheit Compared to Celsius

Just as Fahrenheit worked to improve methods of measuring temperature, others attempted to find new ways as well. One such person was Anders Celsius (1701–1744), a Swedish astronomer who devised a scale based on a range of one hundred degrees between the freezing and boiling temperatures of water. Under the Celsius temperature scale, which is typically abbreviated as °C, water freezes at 0°C and boils at 100°C. Sometimes called the centigrade system, the Celsius scale was adopted as an international standard in 1948; however, the United States continues to use the Fahrenheit system. Conversions from Fahrenheit to Celsius can be accomplished by taking the Fahrenheit temperature, subtracting 32, and multiplying by 5/9. Conversions from Celsius to Fahrenheit can be achieved by taking the Celsius temperature, multiplying by 9/5, and adding 32.

Advantages and Disadvantages of Fahrenheit Scale

While the metric-based Celsius system might seem more orderly and reasonable, the Fahrenheit scale is generally seen as better and more precise at measuring air temperature, which is the most common use for temperature. For instance, freezing is recorded at 32°F and 0°C, while the average room temperature is 68°F and 20°C, a difference of almost two degrees Fahrenheit to every degree Celsius. This ratio and the wider range of degrees between the points on the Fahrenheit scale allow for a more precise definition of air temperature. Additionally, setting freezing at zero means that Celsius temperatures more frequently dip into negative numbers, which can be a psychological discouragement even if the air is no cooler in either system. For measurements of liquids, however, the Celsius system provides an advantage. It also is more universally used and understood, so it is more convenient in international contexts.

Fahrenheit’s Legacy

In addition to developing a temperature scale that remains in use more than 300 years later, Fahrenheit performed significant experiments to find the materials to use to measure temperatures. In developing his temperature scale, he learned how to blow glass and experimented with a variety of liquids, including alcohol. Fahrenheit invented the first mercury thermometer in 1714. One of three known existing examples of his original thermometer sold at auction for more than £67,000, or $96,000, in 2012.

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