FLASHCARDS: Hot and Cold Hacks for Temp Conversion
TRANSCRIPTS
It’s Flashcard Friday and here at Math! Science! History! and we’re going to figure out whether you need to take a coat or a swimsuit on your next vacation. Because, if the news from Vancouver, Canada is telling you it’s 35°, you’re definitely going to need a swimsuit. But if the news from Los Angeles, CA is telling you it’s 35°, you’re going to need a parka!
Today, we’re going to flash you with the fascinating history of temperature measurement and explore a neat trick for converting between Celsius and Fahrenheit in your head.
The story of temperature begins in the early 1700s, with two scientists: Gabriel Fahrenheit and Anders Celsius.
Gabriel Fahrenheit was a Polish-German physicist and engineer, born in 1686 in what is now modern-day Poland. He was fascinated with precision instruments, and in the early 1700s, he worked extensively with mercury thermometers, vastly improving their accuracy. In 1724, he introduced the Fahrenheit temperature scale, setting the freezing point of water at 32° and the boiling point at 212°, with 180 equal divisions in between. His work became widely accepted, especially in England and later in the United States.
Anders Celsius, born in Sweden in 1701, was an astronomer first and foremost. He traveled extensively across Europe, working with the leading scientists of his time. He was particularly interested in measuring the aurora borealis and improving astronomical observations. In 1742, he proposed his temperature scale, where water freezes at 0 degrees and boils at 100 degrees, which was far simpler than Fahrenheit’s system. Other than the reverse of degrees for boiling and freezing, it was a simpler measuring system. The reason why he set his temperature scale with 0° at boiling and 100° at freezing was that he was influenced by a scale that was used at the time called the Delisle scale. The Delisle scale was invented in 1732 by the French astronomer Joseph-Nicolas Delisle. Though he didn’t have a temperature for freezing, he had set the boiling point at zero. As a result, this particular scale had increasing numbers for decreasing temperatures. The purpose was to avoid working with negative values. However, after Celsius died in 1744, scientists and mathematicians flipped the scale putting 0° at freezing and 100° at boiling.
And in case you’re wondering, Fahrenheit and Celsius never met, and their scales weren’t exactly part of a direct rivalry. By the time Celsius introduced his system, Fahrenheit’s had already been in use for nearly two decades. However, the world naturally gravitated toward Celsius’ metric-based system over time because of its simplicity and compatibility with scientific measurements.
Fahrenheit remains the standard in the United States, as well as a few other places like the Bahamas and Cayman Islands. This is largely due to historical adoption—when the U.S. first established standardized measurements, Fahrenheit was already in use, and switching to Celsius later would have required massive effort and public adjustment. Additionally, Fahrenheit is often preferred for weather reporting because it provides more precise incremental changes at common temperatures, making it easier to describe small fluctuations.
Most of the world, however, uses Celsius due to its logical 0–100 scale, which fits well within the metric system used for scientific and everyday measurements. Countries that have switched from Fahrenheit to Celsius, such as Canada and the UK, did so as part of broader metrication efforts in the 20th century.
Now let’s say you are planning your vacation and you are listening to Radio Canada, one of my favorite apps, and you’re planning to go to Vancouver, Canada. Now you know they have tepid temperatures depending on the time of year. And the news is saying that it is 35°. And you’re thinking ohh my gosh, it’s like July and I have to take a parka this is awful. And then you show up, and everybody’s walking around in shorts and you’re burning up in a sweater. Why did that happen? Well, Canada measures their temperatures in Celsius and the United States measures their temperatures in Fahrenheit. You forgot to convert the two temperatures! But, now that will never happen, because there’s a way to quickly convert them in your head.
First, to convert Celsius to Fahrenheit, you can double the Celsius temperature and then add 30. Here’s how it works:
Let’s say it’s 20 degrees Celsius. Double it to get 40, then add 30. That gives you 70 degrees Fahrenheit.
To convert Fahrenheit to Celsius, you can subtract 30 and then divide by 2. For example, if it’s 86 degrees Fahrenheit, subtract 30 to get 56, then divide by 2, which gives you 28 degrees Celsius.
To make it even simpler, you can round down or up the numbers. So in the last example, to convert Fahrenheit to Celsius, if it’s 86°, you subtract 30, and you have 56. Just round 56 up to 60, and divide by two, which gives you approximately 30°.
But if you want more than an approximation, the actual formula is slightly different:
Fahrenheit equals Celsius times 1.8 plus 32, and Celsius equals Fahrenheit minus 32 times .56
Small fluctuations in Fahrenheit can result in seemingly larger changes compared to Celsius, due to the finer scale divisions. For example, a 1‑degree Fahrenheit change is only about 0.56 degrees Celsius, which means Fahrenheit allows for more detailed temperature gradations in weather forecasting and day-to-day use.
And if you’re listening to this while you’re driving and you’re trying to write it down and make sense of it, first, don’t write anything down while you’re driving pay attention to the road. But if you do want to write it down and you do want to solve this, don’t forget to use PEMDAS, which is an acronym for Parentheses, Exponents, Multiplication, Division, Addition, and Subtraction: in that order. It’s also an acronym for Please Excuse My Dear Aunt Sally, which is not only useful in remembering PEMDAS, but it’s also useful if you and your aunt Sally are in public and she’s really gassy.
So what are some takeaways that we can learn from this? First, understand the temperature scales, And remember that in Celsius, 0° is freezing and boiling is 100°. And in Fahrenheit, water freezes at 32°, and boils at 212°.
Second, Remember the simple rule for conversion, which is double the Celsius temperature, add 30, and you’re close to Fahrenheit.
Third, double-check your travel plans to ensure you’re traveling to a country with a temperature of either Fahrenheit or Celsius.
And there you have it! A quick look at the history of temperature measurement, a mental shortcut to convert between Celsius and Fahrenheit, and an understanding of why some regions prefer one scale over the other. Next time you’re checking the weather, you’ll be able to do those conversions with ease. Thanks for tuning in, and we’ll catch you next time on Math! Science! History!