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Degrees Rankine

The Rankine scale is an absolute scale of thermodynamic temperature named after the Glasgow University engineer and physicist Macquorn Rankine, who proposed it in 1859. Similar to the Kelvin scale, which was first proposed in 1848, zero on the Rankine scale is absolute zero, but a temperature difference of one Rankine degree (°R or °Ra) is defined as equal to one Fahrenheit degree, rather than the Celsius degree used on the Kelvin scale. Degrees Rankine is still commonly used in engineering and the aerospace industry in the United States.

Kelvins

The kelvin, symbol K, is the SI base unit of temperature, named after the Belfast-born and University of Glasgow based engineer and physicist William Thomson, 1st Baron Kelvin. The Kelvin scale is an absolute thermodynamic temperature scale, meaning it uses absolute zero as its null point. It is often used to measure the colour temperature of light sources, and is used in photography as a temperature unit to set white balance.