Ole Rømer

Ole Christensen Rømer (September 25, 1644, Aarhus – September 19, 1710, Copenhagen) was a Danish astronomer who made the first quantitative measurements of the speed of light (1676).

General biography

Rømer was employed by the French government: King Louis XIV made him teacher for the Dauphin, and he also took part in the construction of the magnificent fountains at Versailles.

Related Topics:
Louis XIV - Dauphin - Fountain - Versailles

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In 1681, he returned to Denmark and was appointed professor of Astronomy at Copenhagen University. He was active also as an observer, both at the University Observatory at the Round Tower and in his home, using improved instruments of his own construction. Unfortunately, his observations have not survived: they were lost in the great fire of Copenhagen in 1728.

Related Topics:
1681 - Astronomy - Copenhagen University - Observatory - Round Tower - 1728

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In his position as royal mathemathican, he introduced the first national system for weights and measures in Denmark in May 1 1683. Initially based on the Rhine foot, a more accurate national standard was adopted in 1698. Later measurements of the standards fabricated for length and volume show an excellent degree of accuracy. His goal was to achieve a definition based on astronomical constants, using a pendulum. This would happen after his death, practicalities making it too inaccurate at the time. Notable is also his definition of the new Danish mile. It was 24000 Danish feet, which corresponds to 4 minutes of arc latitude, thus making navigation easier.

Related Topics:
May 1 - 1683 - Rhine foot - 1698 - Pendulum - Danish mile - Navigation

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In the year 1700, he managed to get the king to introduce the Gregorian calendar in Denmark-Norway – something which Tycho Brahe had argued for in vain a hundred years earlier.

Related Topics:
1700 - Gregorian calendar - Tycho Brahe

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He also developed one of the first temperature scales. Fahrenheit visited him in 1708 and improved on the Rømer scale, the result being the familiar Fahrenheit temperature scale still in use today in a few countries.

Related Topics:
Temperature - Fahrenheit - 1708 - Rømer scale - Fahrenheit

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He also established several navigation schools in many Danish cities.

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In 1705, Rømer was made the second Chief of the Copenhagen Police, a position he kept until his death in 1710. He fired the entire force as one of his first acts, being convinced that morale on the force was alarmingly low. He was the inventor of the first street lights (oil lamps) in Copenhagen, and worked hard to try to control the beggars, poor people, unemployed, and prostitutes of Copenhagen. This was the start of a social reform.

Related Topics:
1705 - Police - 1710

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In Copenhagen he made rules for building new houses, got the city's water supply and sewers back in order, ensured that the city's fire department got new and better equipment, and was the moving force behind the planning and making of new pavement in the streets and on the city squares.

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