Fahrenheit (°F)
The Fahrenheit scale, denoted as °F, was established in 1724 by Daniel Gabriel Fahrenheit, a physicist of Polish-German origin. Initially, he based 0°F on the freezing point of a saltwater mixture and set 96°F near average human body temperature. The system was later revised so that pure water freezes at 32°F and boils at 212°F under standard atmospheric conditions. Fahrenheit continues to be the primary temperature scale for everyday purposes in the United States and some Caribbean regions, especially for weather, cooking, and household measurements. While most countries have shifted to Celsius, Fahrenheit remains popular in the U.S. due to tradition and its compatibility with customary units.
Kelvin (K)
The Kelvin (K) is the SI base unit for temperature, named after the Scottish physicist William Thomson, known as Lord Kelvin, who introduced this scale in the 19th century. The scale begins at absolute zero, the point at which particles possess minimal thermal energy. Unlike Celsius or Fahrenheit, the Kelvin scale starts at an absolute reference, eliminating negative values and making it particularly useful in scientific research and engineering. Since 2019, the Kelvin has been officially tied to the Boltzmann constant, ensuring a measurement standard based on fundamental physical properties. It is extensively used in disciplines such as physics, chemistry, astronomy, and cryogenics where exact temperature readings are necessary.