The Centigrade scale is the most widely adopted system for temperature measurement. While many people still use the historical name, the modern, standardized term is the Celsius scale, with the symbol °C. This scale is fundamental to international communication, utilized in virtually all scientific, weather, and daily applications worldwide.
Defining the Centigrade Scale
The term “centigrade” is derived from the Latin words centum and gradus, meaning “100 divisions.” This naming convention describes the scale’s structure, based on the 100-degree interval between the freezing and boiling points of water. The scale sets the freezing point of pure water at one standard atmosphere of pressure as 0°C, and the boiling point under the same conditions at 100°C.
The Centigrade scale was officially renamed the Celsius scale in 1948 by international agreement, honoring the Swedish astronomer Anders Celsius, who first proposed a similar temperature scale in 1742. The temperature unit, the degree Celsius, is now recognized as the SI derived unit for temperature within the International System of Units. The 100-degree division between the freezing and boiling points of water remains the defining feature of the scale.
Practical Application and Global Use
The Celsius scale serves as the universal standard in science, meteorology, and most national temperature reporting. Its logical structure, based on powers of ten and tied to water, makes it easy to use in scientific calculations and daily life. This universal adoption simplifies international data sharing and manufacturing processes.
For general daily reference, familiar Celsius temperatures provide clear benchmarks for interpreting conditions. The average internal human body temperature is approximately 37°C, with a fever starting at 38°C or higher. A comfortable indoor room temperature is typically 20°C to 22°C.
Comparison to Fahrenheit
The primary alternative temperature system is the Fahrenheit scale, which uses different reference points and divisions. On the Fahrenheit scale, the freezing point of water is 32°F, and the boiling point is 212°F. This results in an interval of 180 degrees between the two fixed points, compared to the 100-degree interval of the Celsius scale.
Converting between the two scales is often necessary. The precise mathematical formula to convert Fahrenheit to Celsius is to subtract 32, then multiply the result by the fraction five-ninths (C = (F – 32) x 5/9). This calculation accounts for the different starting points and degree sizes.
A convenient mental shortcut exists for the single temperature value where the two scales align exactly: \(-40^\circ\text{C}\) is equal to \(-40^\circ\text{F}\). For rough approximations, doubling the Celsius temperature and adding 30 provides a quick, though inexact, estimate of the Fahrenheit equivalent. For example, \(20^\circ\text{C}\) (warm) becomes \(70^\circ\text{F}\), which is close to the actual \(68^\circ\text{F}\).