The Réaumur scale, also known as the "octogesimal division", is a temperature scale for which the melting and boiling points of water are defined as 0 and 80 degrees respectively. The scale is named for René Antoine Ferchault de Réaumur, who first proposed a similar scale in 1730.
Old thermometer in a pharmacy in Vienna, showing room temperature by Reaumur scale.
Réaumur and Celsius scale on thermometer. Private collection, central Europe.
Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making up a substance.
A typical Celsius thermometer measures a winter day temperature of −17 °C
Plots of pressure vs temperature for three different gas samples extrapolated to absolute zero
An illustration of the range of cosmic temperatures