Rømer scale

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**Rømer temperature conversion formulae**
	from Rømer	to Rømer
Celsius	[°C] = ([°Rø] − 7.5) × ⁴⁰⁄₂₁	[°Rø] = [°C] × ²¹⁄₄₀ + 7.5
Fahrenheit	[°F] = ([°Rø] − 7.5) × ²⁴⁄₇ + 32	[°Rø] = ([°F] − 32) × ⁷⁄₂₄ + 7.5
Kelvin	[K] = ([°Rø] − 7.5) × ⁴⁰⁄₂₁ + 273.15	[°Rø] = ([K] − 273.15) × ²¹⁄₄₀ + 7.5
Rankine	[°R] = ([°Rø] − 7.5) × ²⁴⁄₇ + 491.67	[°Rø] = ([°R] − 491.67) × ⁷⁄₂₄ + 7.5
For temperature intervals rather than specific temperatures, 1 °Rø = ²¹⁄₄₀ °C and 1 °Rø = ⁷⁄₂₄ °F Comparisons among various temperature scales

Rømer is a disused temperature scale named after the Danish astronomer Ole Christensen Rømer, who proposed it in 1701.

In this scale, the zero was initially set using freezing brine. The boiling point of water was defined as 60 degrees. Rømer then saw that the freezing point of water fell at roughly one eighth of that value (7.5 degrees), so he used that value as the other fixed point. Thus the unit of this scale, a Rømer degree, is 40/21 of a kelvin (or of a Celsius degree). The symbol is sometimes given as °R, but since that is also sometimes used for the Rankine scale, the other symbol °Rø is to be preferred. The name should not be confused with Réaumur.

A plausible story of how the Fahrenheit scale was invented is that Daniel Gabriel Fahrenheit learned of Rømer's work and visited him in 1708; he improved on the scale, increasing the number of divisions by a factor of four and eventually establishing what is now known as the Fahrenheit scale, in 1724.