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Romer

Name: Ole Romer

Nickname/Alias: Olaus Romer

Achievements: First scientific measurement of the speed of light.

Born: September 25, 1644; Arhus, Jutland

Died: September 23, 1710; Copenhagen, Denmark. Aged 66

Field & Discipline: Science; Astronomy; Astronomer

Language: Danish

Father: Unknown

Mother: Unknown

Siblings: Unknown

Spouse: 1) Anna Maria Bartholin; 2) Name Unknown

Children: None

Education: University of Copenhagen

Life & Times:

Romer's family were moderately-well-off merchants. At Copenhagen University he

studied under [taught by] Thomas Bartholin* and lived in the house of [taught by] Erasmus Bartholin* who taught him astronomy and mathematics. Erasmus Bartholin recognised Romer's ability and gave him the unpublished manuscripts of the astronomer [edited manuscripts of] Brahe* to edit.  Romer later married Erasmus Bartholin's daughter, Anna.

In 1671, the French Academy of Sciences started a project to compare measurements made by Brahe in the previous century with new measurements made at the Paris Observatory.  [worked with] Picard* arrived from Paris to undertake this project and Romer accompanied him and Bartholin to Brahe's observatory on the island of Hven, in September 1671.

During the next eight months they made observations on eclipses of the first satellite of Jupiter and when Picard returned to Paris Romer accompanied him. He was given lodgings in the new Royal Observatory, and appointed by [taught son of] Louis XIV*  tutor to the Crown Prince.

Romer made a series of astronomical observations in Paris and other places in France. He also developed clocks and other pieces of apparatus, including a micrometer for differential measurement of position that became standard use. Scientists at that time were trying to establish accurate predictions of the time of eclipses of Jupiter's moons at a fixed meridian, such as Paris or Greenwich in England. Accurate data would be extremely useful to mariners in calculating geographical longitude.

It had already been discovered that the eclipses of Jupiter's moons by Jupiter were not

periodically regular. It was also discovered in 1675 that this irregularity appeared to be due to the position of the Earth relative to Jupiter. The idea that these irregularities might have anything to do with the finite speed of light (i.e. delays in sightings) was considered and discarded.

Romer noticed that the time between eclipses became shorter the closer earth moved to Jupiter and longer as the two planets moved further away from each other. On the basis of this observation, he predicted in September 1676 that the eclipse expected on November 9 of the same year would be ten minutes later than predicted. He was right and he correctly stated that this was due to the finite speed of light,  which took longer to cross between planets the further away from each other they were.

He reported that light would take eleven minutes to reach Earth (a measurement modified in 1729 to eight minutes and twenty seconds) and declared that the speed of light was 140,000 miles  per second (now accepted at 186.282 miles per second).  Romer was, in this, the first person to establish the speed of light scientifically.

In 1679 Romer visited England and met [met] Newton*, [met] Flamsteed* and [met] Halley*.  Two years later he returned to Denmark as professor of mathematics at Copenhagen. He was appointed astronomer royal by the Danish king (Christian V) and director of the observatory. He found that the observatory was not a suitable site from which to make his astronomical observations and built an observatory at his own house. He also gave advice on ballistics, led a commission to inspect the roads, and served as master of the mint, inspector of naval architecture and harbour surveyor.

In 1688 he became a Privy Councillor, five years later he was appointed first judiciary magistrate in Copenhagen and in 1694 he was made chief tax assessor and produced a new and fairer tax system.

In 1704 he established a new observatory equipped with the latest instruments. He appears to have been the first astronomer to have attached a telescope to altitude and azimuth circles, which enabled him to measure the location of celestial objects more accurately.

He became mayor of Copenhagen and prefect of police in 1705. King Frederick IV made him a senator and in 1707 he was made head of the state council of the realm. Knowing the importance of accurate instruments, Romer developed an innovative thermometer with a scale based on two fixed points: the upper one marking the boiling point of water and the lower point marking the melting point of ice.

In 1708 [met and influenced] Fahrenheit* visited Romer and was so impressed by his method of scaling his thermometers that he was inspired to develop a [developed] temperature scale* of his own.

Extra Connections: Used the tables of [used tables of] Cassini family*

His work related to that of [work related to] Leeuwenhoek*

His work related to that of Andreas [work related to] Celsius*

Assessment: Romer was the first person to provide a scientifically-accurate measurement of the speed of light and a workable temperature scale.

Oneliner: Ole Romer, first speed of light and temperature scale

Bibliography: