Defending Fahrenheit

By Brad Frizzell

I recently arrived home from traveling out of the country for work. Although I have been outside the country more times than I can count, there is absolutely one thing that drives me bananas about going abroad – it is this enigma known as a thermostat in Celsius. I know, I know, I know. I have a phone that I can do the conversions on between Fahrenheit and Celsius quite quickly and not have a problem. But who wants to do that when you wake up in the middle of the night sweating. I do not know if the thermostat is set insanely high, insanely low, or just right, or if the AC is broken. I do know that I am uncomfortable, and I am not sure how to fix it. Simply put, I do not speak Celsius.

If you have read any of my prior blogs, you know that I rely a lot on my gut instincts. Why do I love Fahrenheit so much and detest the ground that Celsius walks on? Is it because I was born with Fahrenheit as my preferred means of measuring temperature? Or is it because I am an American, and I hate the metric system?


Perhaps, it is something more. While waiting for my airplane, I began researching the Fahrenheit system. I grew up using Fahrenheit but never questioned why or what it was. The temperature seemed odd at best, but everyone knows that water freezes at 32 degrees F. It boils at 212 degrees F. But why 32 degrees and why 212 degrees? I just assumed that that is the way it is. Well, I am here to say that Fahrenheit might be the superior unit of measurement for temperature. Before you call shenanigans on what I just said, hear me out. I do not believe for a moment that Fahrenheit is vastly superior to Celsius in most applications. However, there may be one. Let us review Fahrenheit as I have come to know it, before proceeding any further. Through my exquisite abilities on Google, Wikipedia, and other unverified internet sources, I have become a self-appointed expert at the Fahrenheit standard. Or as I like to call it, the works of German physicist Daniel Gabriel Fahrenheit (1686-1736). Although the exact method of the madness by Daniel Fahrenheit is unknown, we do have a few clues into what he was thinking. Daniel Fahrenheit wanted to thermometers to measure the same thing at different points in time and give the same reading. According to Dr. John H. Lienhard, of the University of Houston, Daniel Fahrenheit understood rather than use the temperature of the hottest and coldest day of the year, materials whose physical property is more constant would serve as a better benchmark.

0 degrees Fahrenheit is defined as the temperature at which a brine solution of equal parts ice, water, and salt (ammonium chloride variety) would freeze. But you have to have more than one point to draw a line, in this case, the scale of Fahrenheit. Dr. Fahrenheit assumed that pure water would melt at 32 degrees F and that the temperature of the human body was 96 degrees F. Finally, Dr. Fahrenheit set the value of water boiling to 212 degrees F. Now we have a linear scale in which we can fix predefined intervals and adjust accordingly. So, for those that are keeping score at home, we have a 180 degree F separation, as defined at sea level and standard atmospheric pressure. Fast forward 300 years later, and Fahrenheit is the official temperature scale of only the United States of America. You may be saying to yourself hold on; you said that Fahrenheit was based on the body temperature of 96 degrees F, which we now know to be incorrect. I never said that Dr. Fahrenheit was perfect. However, it is my understanding he did invent the first mercury thermometer, which was the first practical and accurate thermometer. This pioneer of exact thermometry knew his stuff.


Not to leave well enough alone, along comes Anders Celsius, who in 1742 proposed the centigrade temperature scale, later to be named “Celsius” in his honor. (See Purdue citation below for more biographical information). The centigrade is very simple, “centi” meaning 0 degrees C is freezing water, and 100 degrees C is water, pure and at sea level, and standard atmospheric pressure boils. Mr. Ander’s solution seems so simple, so practical, and so apparent that how could anyone even argue that it is inferior to Fahrenheit. Anders Celsius took a convoluted temperature scale, simplified it to its bare parts, and for the last 300 years, defined how the world has measured temperature. 

Rankine Cycle

Not so fast. I had mentioned before that the United States was the only country using Fahrenheit as its official temperature scale. Although that is correct, it is not exactly forthcoming. In comes Glasgow University engineer and physicist William John Macquorn Rankine. If you are in any way a trained engineer in the areas that involve heat or motion or steam engines, you are no doubt familiar with the Rankine Cycle. It is a model used to predicate the performance of steam and turbine systems. At 0 degrees R, you have reached absolute zero; by definition, this is the perfect coldest temperature possible. For those who are still cheering on Mr. Anders Celsius and his equivalent of 0 degrees C, water freezes at 273.15 degrees K, or 459.67 degrees R. If you are keeping score, you would realize that the degree spacing for Rankine is that of Fahrenheit. The Kelvin scale was proposed in 1848, yet Mr. Rankine, some ten years later, proposed the Rankine scale. If Celsius was the end-all, be-all temperature measurement, then why would Rankine stick to a Fahrenheit scaling? The obvious answer would be that Rankine needed a counter scale that coincides with the Fahrenheit system for when you do engineering calculations and customary units. However, I have a new theory.

No one can argue that when it comes to water, Celsius is the end-all, be-all. The Alpha, the Omega. The cat’s meow. However, it is the measurement of air temperature that Fahrenheit excels in. As human beings, we do not inhabit the water—our time in water falls into the category of too cold or comfortable. However, human beings do inhabit an environment that does surround them with air. As such, our sensitivity to air is exact. 

I was reading an article on ZME Science that stated that most inhabit a world of existing temperatures that range from -20 degrees F to 110 degrees F, or a 130 range. On the Celsius scale, temperatures range from -28.8 degrees C to 43.3 degrees C or 72.1 degrees. What does all of this mean? Well, I took the long road around to get to what I already know. As I understood quite acutely from messing with a thermostat outside the country, Fahrenheit is much more suited for air temperatures than Celsius. Air temperatures, at least as far as the human psychological component is concerned, require more precise measurements than water.

I know that precision depends upon the instrument being used to measure the temperature and not the unit of measurement. However, the psychological component of accuracy is different altogether. I have found that humans memorize whole numbers much easier than decimals – this is strictly my observation. As a scientist, I have no data to back this up. However, I know that when a thermostat is 69 degrees F, it is about as cold as I can take it, and anything over 74 degrees F is uncomfortable. When I look at a newspaper, I know that it is going to be in the 90degrees and be quite warm, and then tomorrow it might be below 30 degrees and be very cold. If I look at a newspaper and I see that today is maybe 22.3 degrees and tomorrow will be 22.9 degrees, I have no idea what that means psychologically. As a man of science, I am quite familiar with the Celsius scale as it relates to water and thermodynamics. After trial and error, I feel that anything above 23 degrees C is uncomfortable for room temperature, and anything less than 22 degrees C is a slight bit chilly. As far as the decimals in between, I will have to ask the Sphinx the next time I see her. As far as I am concerned, I was born on a 70 degrees F day and hoped to die on a 70 degrees F day.

Although I write this in tongue-in-cheek, the purpose of this was to illustrate the importance of scaling both in our instrumentation of the world and drawing world, all too often we pass the importance of appropriate scaling. In the academic world and the software world, the art of scaling is more precise with formulas and accepted engineering practices. However, in the physical world of gauges and sensors and so forth, scaling sometimes becomes more of finesse than a repetitive exercise period. Sometimes, a given measure for a given application only comes in a limited number of scaling trims. We give it the best consideration we can, do the best we can provide with what is available, and our budgetary constraints. I have seen drawings with prints so small that it would require a high-end university electronic microscope to read. I have seen other drawings where my 2ft x 3ft page would be more appropriate as an instrument of surrender than an informative illustration due to all of the empty white space on it. So, for the sake of those whose lives and livelihood depend on these instruments and drawings that we put forth to the field, please give scaling its due respect. Thank you for giving me your attention and time, and I hope that you have found this a worthy read.

Please note the opinions expressed here are mine and mine alone. In no way are they meant to be a representation of the views of or an endorsement thereof, of the cited sources or mentioned people. In other words, I found these links on the Internet and thought they would be cool to pass on. These people have not communicated with me, nor have I communicated with them. Simply put, we have no relation with each other.