Take a look out your window. Can you tell if it’s hot or cold outside today? In most cases, unless there is snow falling from the sky or it’s so hot that the pavement is shimmering, it’s hard to tell what the temperature is like. Thankfully, we can determine if we should wear shorts or pants by examining temperature scales.
What Is Temperature?
When you hear the word temperature, what comes to mind? For most, it’s likely their weather app or the thermometer you use to determine if you’re running a fever. We see temperature as the measurement of heat or cold, whether that means we’re measuring outside our homes or inside our ovens.
For scientists, especially those that study physics, the temperature is the measurement of the average kinetic energy of moving particles in a substance. When something is hot, its particles move and vibrate faster than when it’s cold.
A fun side note: That kinetic energy has also been used as a plot point to explain the magic behind setting something on fire with your mind, at least in the Disney movie “The Sorcerer’s Apprentice.” Nicholas Cage’s character, Balthazar, explains that to set something on fire, you simply have to make the molecules vibrate faster and faster until they eventually spontaneously combust. Wouldn’t that be an awesome ability to have? You’d never have to worry about being stuck without matches ever again.
How Do We Measure Temperature?
While we might not be setting things on fire with our mind, we do still need to be able to understand whether it’s hot or cold outside, which leads us to our next subject. How do we measure temperature?
In the past, analog thermometers relied on mercury. Once we realized how dangerous this element is when it comes into contact with the human body, we switched to less toxic chemicals. These thermometers have a reservoir of liquid at the bottom of a tube. When exposed to heat, the liquid expands and moves up.
The sides of the thermometer are marked with temperature readings in either Fahrenheit or Celsius — or sometimes both. When the liquid stops rising, the mark it’s next to indicates the temperature.
Digital thermometers work in much the same way, but instead of using an expanding liquid, they use sensors to detect and display the temperature. Laser and infrared thermometers measure the infrared energy that hot or cold items give off, and show that as temperature.
Fahrenheit vs. Celsius vs. Kelvin
There are three different temperature scales, but unless you’re working in the sciences, you’ll probably only encounter two of them in your lifetime.
If you’re in the United States, Belize, Palau or the Bahamas, and someone asks you the temperature, you will generally answer in Fahrenheit. This temperature scale was invented in 1724 by a German scientist named Daniel Gabriel. On the Fahrenheit scale, water boils at 212 degrees and freezes at 32 degrees. The average temperature of the human body is 98.6.
The rest of the world uses Celsius. Andres Celsius invented this method in 1742 and called it Centigrade. It became Celsius in 1948 to prevent confusion since French and Spanish languages already used that word as a unit of measurement. Like the rest of the metric system, Celsius relies on nice clean multiples of 10, so water freezes at 0 degrees and boils at 100. The average temperature of the human body in Celcius is 37 degrees.
You can convert temperatures in Fahrenheit to Celsius with the following formula: (F-32)/1.8 = C, with F being your temperature in Fahrenheit. To convert from Celsius to Fahrenheit, simply reverse the formula.
The final temperature scale is Kelvin. Typically scientists like physicists and chemists use this scale to record very precise temperatures. It represents the amount of kinetic energy inside a substance and starts at absolute zero, which is the point where kinetic energy ceases. Absolute zero, or 0 Kelvin, is equal to -274.15C or -459.67F. Water’s freezing temperature is 273K and boils at 373K.
To convert from Fahrenheit to Kelvin, you first need to change your temperature to Celsius. Then, take your temperature in Celsius and add 273.15.
Fun With Temperature Scales
When you look out your window, is it hot or cold outside? Whether you use Celsius, Fahrenheit or Kelvin, you’ve got the tools to figure out what kind of clothes you should be wearing for the day. If the United States would get on the ball and start using Celsius like the rest of the world, things would get even easier to understand.