Thermometer
Thermometer
[Cueball stands in the center of the panel holding a thermometer.] Cueball: This thermometer is in Celsius. How do you change it? Off-panel voice: Long press the button.
[Cueball presses the button, and the thermometer beeps] Press Beep Thermometer: Units: Kelvin Cueball: No...
[Cueball presses the button, and the thermometer beeps] Press Beep Thermometer: Units: Degrees Rankine Cueball: What.
[Cueball presses the button, and the thermometer beeps] Press Beep Thermometer: Units: Average Translational Kinetic Energy Cueball: This is the worst thermometer. Off-panel voice: Boltzmann's constant is on the side if you need it.
In 1643: Degrees , Cueball struggles with which temperature unit to use, and ultimately tells his friend the temperature in radians , which is not a valid temperature scale.
In 1923: Felsius , Randall proposes a combined Fahrenheit/Celsius temperature scale called Felsius.

This comic is arguably the 17th comic in a row (not counting the April Fools' comic ) in a series of comics related to the COVID-19 pandemic .
This comic expresses frustration at the multitude of temperature scales. Randall , as a former engineer, has strong opinions about units, as unit conversion is often a gripe for many engineers. (In a special preface in the UK edition of Randall's book What If , he mentions that one does not appreciate the metric system unless they have had to go through a bunch of scientific papers using really unusual units like "kilocubic feet per second" or "acre-feet".) As elevated body temperature is a symptom of COVID-19, the comic is thus also concerning the virus.
Cueball is holding what appears to be a medical thermometer, implying that he's trying to check his body temperature . He mentions that the thermometer is in Celsius, and asks how to change it.  Many thermometers sold in the United States have settings for both Fahrenheit and Celsius, with an option to change between the two. Americans are almost always more familiar with body temperatures in Fahrenheit, so Cueball presumably expects to change to that scale. However, he finds that the thermometer provides measurements in a series of scales that are increasingly unhelpful. Human body temperature in Celsius is 37 °C.
where k B is the Boltzmann constant , 1.380649×10 −23 J⋅K -1 . So if this thermometer told you a translational kinetic energy measurement in joules, you could get the measured temperature in the Kelvin scale by dividing by the Boltzmann constant and multiplying by 2/3. Somebody who actually wanted to use this measure of temperature might then find it useful to have Boltzmann's constant printed on the thermometer.
Using these last three units for home temperature gauging would be ridiculous, as Kelvin and Rankine measurements of body temperature are unfamiliar to the average user and even those familiar with them would need to do calculations to translate normal body temperature.  Kinetic energy is obscure enough that only physicists, engineers and thermodynamicists, a relative handful of the potential buyers, would likely know what it refers to. Those that do could make use of the value printed on the thermometer, but such would add a great deal of unnecessary complexity to what should be a simple and intuitive task.
In the last frame Cueball calls the thermometer the worst. It seems to lack Fahrenheit entirely, frustrating its American consumer base, including Cueball. From a nerd's perspective this would be an extraordinary device, offering even exotic temperature scales. However, a "normal person" would find this thermometer terribly difficult to use for everyday purposes when set on any of the non-Celsius scales, like checking their body temperature or the temperature of food. As an item of consumer electronics, especially one sold in the United States, it would be almost completely useless.
Deliberately lacking Fahrenheit is a jab against the Imperial system of units , and against the similar but distinct system of United States customary units . Although Imperial units and local traditional units are still used for various limited purposes (and/or by older generations) in different countries, most of the world has switched to using the metric system for most purposes going forward, with the US being relatively unusual in the extent to which it still routinely defaults to the US customary units in daily life.  Many proponents of the metric system have long pushed for the US to change over, arguing that Imperial and US customary units (and degrees Fahrenheit, specifically) are archaic and obsolete. Randall has dealt with this conflict in other strips ; as a physics major, he's partial to the metric system, and finds it frustrating to maintain multiple different scales (which is the basis of the conflict in this strip). On the other hand, he recognizes certain intuitive advantages to Imperial and US customary measurements, and recognizes that the forces of social inertia in US society make change difficult.
The title text references an archaic temperature unit, Rømer , first proposed in 1701, and is the common ancestor of both the Celsius and Fahrenheit scales. Unlike the other measurements mentioned in this strip, the Rømer scale is no longer used in any context, and only people interested in the history of temperature scales have any idea that it even exists. This is the ultimate form of obscure and outdated temperature measurements.
[Cueball stands in the center of the panel holding a thermometer.] Cueball: This thermometer is in Celsius. How do you change it? Off-panel voice: Long press the button.
[Cueball presses the button, and the thermometer beeps] Press Beep Thermometer: Units: Kelvin Cueball: No...
[Cueball presses the button, and the thermometer beeps] Press Beep Thermometer: Units: Degrees Rankine Cueball: What.
[Cueball presses the button, and the thermometer beeps] Press Beep Thermometer: Units: Average Translational Kinetic Energy Cueball: This is the worst thermometer. Off-panel voice: Boltzmann's constant is on the side if you need it.
In 1643: Degrees , Cueball struggles with which temperature unit to use, and ultimately tells his friend the temperature in radians , which is not a valid temperature scale.
In 1923: Felsius , Randall proposes a combined Fahrenheit/Celsius temperature scale called Felsius.
