Why does the US use Fahrenheit instead of Celsius? What are the differences?

While unique and somewhat perplexing to the rest of the world, the Fahrenheit temperature measurement is a distinctive feature of the US. Interestingly, the Cayman Islands and Liberia also adhere to this system. It’s intriguing that a country of such magnitude would adopt a measurement that is challenging to interpret and lacks mathematical precision, as evidenced by a costly error in 1999.

A conversion mistake between the two scales destroyed a Mars rover; Fahrenheit has an inbuilt error that makes a perfect conversion impossible. So why is the US stuck to its old and outdated way of measuring heat?

What is the history behind the systems?

The Fahrenheit system, named after its creator, Daniel Gabriel Fahrenheit, a German scientist born in the Polish-Lithuanian Commonwealth in 1686, was the first to develop a reliable temperature measurement method. This historical context is crucial to understanding the system’s continued use in the US.

The German scientist set zero at the lowest temperature he could get a water and salt mixture to reach. The second fixed point in the system was the temperature of the human body, 96 degrees, but his measurement was slightly off. This set the boiling point of water at 212 degrees and the freezing point at 32 degrees.

The British liked his ideas, and after inducting him into the Royal Society in 1724, measurement proliferated around the globe as the British Empire expanded.

However, the invention of the metric system brought thermometers back under the microscope. The French Revolution inspired an overturning of the old ways, and Fahrenheit was thrown out. It helped that the change stuck; it makes sense that zero temperature is the freezing point of water, with 100 degrees as the boiling point. Both can be easily visualized as ice and steam, but Fahrenheit has no visual cue for the temperature.

Even the British changed their waves, mostly at least in 1965, and the US was very close to following suit.

Why hasn’t the US changed to the metric system?

In 1975, Congress passed a law to begin the metrication process and set up a Metric Board to supervise the transition.

However, as it made metrication voluntary rather than mandatory, people chose not to learn the new systems for temperatures and weights. This decision was not just a matter of preference but reflected the complexity and challenges of such a significant change.

“Motorists rebelled at the idea of highway signs in kilometers, weather watchers blanched at the notion of reading a forecast in Celsius, and consumers balked at the prospect of buying poultry by the kilogram,” Jason Zengerle writes in Mother Jones.

Despite the metric system gaining global popularity, the US has remained steadfast in its use of Fahrenheit. This can be attributed to a variety of factors, including the voluntary nature of the metrication process initiated by Congress in 1975, which led to a lack of widespread adoption of the new system.