The lowest temperature at which a substance can retain no heat energy is absolute zero. At this temperature, the vibrational motion of nature’s fundamental particles is insignificant. That temperature is 0K on the Kelvin scale, –273.15 degrees on the Celsius scale, and 459.67 degrees on the Fahrenheit scale.

Any thermometric scale on which a measurement of zero corresponds to temperature’s theoretical absolute zero, that is, the thermodynamic equilibrium condition of minimum energy is known as an absolute scale of temperature. The Kelvin (K) scale, which is an absolute scale defined by the Boltzmann constant of 1.380649 x 10–23 joule per kelvin, is the standard measure of temperature in the International System of units.

Temperature scales

To understand the absolute scale of temperature, let’s first learn the temperature scales.

Celsius scale

The most common unit of temperature measurement is Celsius or centigrade. Anders Celsius (1701–1744), a Swedish astronomer, was the inspiration for the name.

At one atmosphere pressure, water has a freezing point of 0oC and a boiling temperature of 100oC. The link between degrees Celsius and Kelvin is as follows:

T(Celsius) = T(Kelvin)–273.15°

Important points

• The degree Celsius (°C) is a unit of measurement that can be used to denote a temperature interval, a difference between two temperatures, or uncertainty on the Celsius scale.
• The unit “degree Celsius” and the Celsius scale are currently defined by two temperatures: absolute zero and the triple point of Vienna Standard Mean Ocean Water, as agreed upon by international agreement (VSMOW; specially purified water). This also explains how the Celsius scale connects to the Kelvin scale, which utilises the symbol K to identify the SI base unit of thermodynamic temperature. Absolute zero is precisely 0K and -273.15°C, the lowest temperature imaginable (the point at which matter achieves minimum entropy). The temperature of water at its triple point is precisely 273.16K and 0.01°C..

Fahrenheit scale

The Fahrenheit scale is named after Daniel Gabriel Fahrenheit (1686-1736), a scientist who proposed the concept in 1724. The temperature on this scale is measured in degrees Fahrenheit (oF).

Water’s freezing point, for example, is 32 degrees Fahrenheit, while its boiling point is 212 degrees Fahrenheit. As a result, a degree on the Fahrenheit scale is 1/180 of the temperature difference between the freezing and boiling points. Water’s freezing and boiling points are 100 degrees apart on the Celsius scale.

Important points

• During the mid-to-late 20th century, most countries replaced the Fahrenheit system with the Celsius scale. But still, the official temperature scale in the United States, the Cayman Islands, Palau, the Bahamas, and Belize is Fahrenheit.

Kelvin scale

Kelvin is one of the seven base units of the International System of units and has the symbol K (SI). The Kelvin scale is a thermodynamic absolute temperature scale that starts at absolute zero and ends at absolute zero. In the classical thermodynamics model, absolute zero is the temperature at which all thermal motion ceases.

Important points

• 0K (absolute zero) is universal because it suppresses all thermal movements in all materials to the greatest extent possible. As a result, absolute zero is a natural choice for the Kelvin scale’s null point.
• Because a variety of physical parameters, such as the volume of an ideal gas, are directly connected to absolute temperature, the Kelvin scale is widely utilised in scientific activity.
• The quantum mechanical zero-point energy, or the energy of the ground state, is still present in the K system at absolute zero. However, kinetic energy can be zero in the interpretation of classical thermodynamics, and matter’s thermal energy vanishes.
• In the laboratory, the lowest temperature has been attained in the 100 pK range, where pK (pico-Kelvin) equals 10-12 K. The lowest natural temperature ever recorded is around 1K, which was discovered in the Boomerang Nebula’s rapid expansion of gases.

Conclusion

A temperature scale is a methodology of calibrating the physical quantity temperature. Empirical scales are used to quantify temperature with reference to easy-to-understand and reliable factors like the freezing and boiling points of water. Absolute temperature is based on thermodynamic principles, which include choosing a useful incremental unit and using the lowest possible temperature as the zero point. Common temperature scales include Celsius, Kelvin, and Fahrenheit. -273.15 degrees Celsius is the lowest temperature imaginable. On the Kelvin scale, this equals 0K. A temperature of 0K signifies the point at which atoms cease to move. Absolute zero, or 0K, is the temperature at which atom motion comes to a standstill.  Thus, the study of the absolute scale of temperature is very critical and necessary.