Rømer (°Rø)
The Rømer scale is a historical temperature scale devised by Danish astronomer Ole Christensen Rømer around 1701. It sets the freezing point of water at 7.5°Rø and the boiling point at 60°Rø. Although obscure today, the Rømer scale holds a special place in the history of thermometry: Daniel Gabriel Fahrenheit visited Rømer and was directly inspired by his work when developing the Fahrenheit scale.
Definition
On the Rømer scale, brine freezes at 0°Rø, water freezes at 7.5°Rø, and water boils at 60°Rø at standard atmospheric pressure. To convert Rømer to Celsius: °C = (°Rø − 7.5) × 40/21. To convert Celsius to Rømer: °Rø = °C × 21/40 + 7.5. Normal body temperature (37°C) is approximately 26.925°Rø.
History
Ole Rømer, already famous for making the first quantitative estimate of the speed of light in 1676, developed his temperature scale around 1701 in Copenhagen. He chose the freezing point of brine (a salt-water mixture) as his zero point and set the boiling point of water at 60°. Water froze at 7.5° on his scale. When the young Daniel Gabriel Fahrenheit visited Rømer in 1708, he adopted Rømer's approach but multiplied the scale by a factor of four to eliminate fractions, yielding his 32° for the freezing point and 212° for boiling. Thus the Rømer scale is the direct ancestor of the Fahrenheit scale.
Common Uses
The Rømer scale has no modern applications. It is studied purely in the context of the history of thermometry and the development of the Fahrenheit scale. It occasionally appears in physics education and temperature conversion exercises.
Did You Know? Facts About Rømer
- Fahrenheit visited Rømer in 1708 and essentially multiplied Rømer's scale by 4 to get rid of the inconvenient 7.5° freezing point, yielding 32°F.
- Rømer is more famous for measuring the speed of light in 1676 than for his temperature scale.
- The Rømer scale's 7.5° freezing point seems arbitrary, but Rømer chose it because he wanted brine (the coldest mixture he could make) to be 0° and boiling water to be a round 60°.
- If Fahrenheit had not visited Rømer, the Fahrenheit scale might never have existed - and the US might use a completely different temperature system today.
- Ole Rømer served as mayor of Copenhagen and as head of the Danish police in addition to his scientific career.