The kelvin (K) is a unit of measurement for temperature, similar to the Celsius and Fahrenheit scales. What sets it apart?
Most people typically refer to temperature in Fahrenheit or Celsius. Still, scientists favor Kelvin due to its status as an absolute scale. This means it starts at the lowest possible temperature in the universe, making it ideal for accurate scientific research.
It's also one of the seven base units in the International System of Units (SI).
The Kelvin scale begins at 0 K, a point known as absolute zero. This isn't just a random number—it's the theoretical temperature where all atomic motion would completely stop. It's the ultimate cold.
Unlike Celsius, where 0° is the freezing point of water, 0 K is based on a fundamental truth of the universe. This non-arbitrary starting point is why scientists in fields like physics and astronomy rely on it.
While you won't use Kelvin to check the daily weather, it's essential in many scientific and technological fields.
- Astronomers use it to measure the frigid temperatures of deep space and the scorching heat of stars.
- Physicists need it for experiments in quantum mechanics and superconductivity.
- Engineers use it when working with materials at extreme temperatures, from rocket engines to medical MRI machines.
The good news is that converting between Kelvin and Celsius is very easy. The size of one unit is identical in both scales, meaning a change of 1 K is the same as a change of 1 °C.
Here are the conversion formulas you need:
- To convert Celsius to Kelvin: Add 273.15 to your Celsius temperature.
- To convert Kelvin to Celsius: Subtract 273.15 from your Kelvin temperature.
Examples:
- Water freezes at 0 °C, which is 273.15 K.
- A pleasant room temperature is approximately 20 °C, which corresponds to 293.15 K.
- Water boils at 100 °C, which is 373.15 K.
The scale is named after its inventor, the brilliant Scottish engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907). In 1848, he introduced an "absolute" thermometric scale beginning at what he called "infinite cold" — the temperature now known as absolute zero. His work established the foundational principles of a measurement system central to modern science.