Peder ielsenHorrebow (Horrebov) (14 May 1679 – 15 April 1764) was a

Danish Danish may refer to: * Something of, from, or related to the country of Denmark People * A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark * Culture of Denmark * Danish people or Danes, people with a Danish a ...

astronomer. Born in

Løgstør Løgstør is a town in Denmark with a population of 3,967 (1 January 2022) It is located 47 km west of Aalborg and 64 km north of Viborg. Løgstør's city centre consists of old streets with small houses built in the 1800s for fishermen and sailo ...

Jutland Jutland ( da, Jylland ; german: Jütland ; ang, Ēota land ), known anciently as the Cimbric or Cimbrian Peninsula ( la, Cimbricus Chersonesus; da, den Kimbriske Halvø, links=no or ; german: Kimbrische Halbinsel, links=no), is a peninsula of ...

to a poor family of fishermen, Horrebow entered the

University of Copenhagen The University of Copenhagen ( da, Københavns Universitet, KU) is a prestigious public research university in Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in Scandinavia after Uppsala Unive ...

in 1703. He worked his way through grammar school and university by virtue of his technical knowledge: he repaired mechanical and musical instruments and cut seals. He received his MA from the university in 1716, and his MD in 1725. From 1703 to 1707, he served as an assistant to Ole Rømer and lived in Rømer's home. He worked as a household tutor from 1707 to 1711 to a Danish baron, and entered the governmental bureaucracy as an

excise file:Lincoln Beer Stamp 1871.JPG, upright=1.2, 1871 U.S. Revenue stamp for 1/6 barrel of beer. Brewers would receive the stamp sheets, cut them into individual stamps, cancel them, and paste them over the Bunghole, bung of the beer barrel so when ...

writer in 1711. After repeatedly petitioning King Frederick IV, Horrebow became professor of mathematics at the University of Copenhagen in 1714. He also became director of the university's observatory (called the

Rundetårn The Round Tower ( Danish: Rundetårn) is a 17th-century tower in Copenhagen, Denmark, one of the many architectural projects of Christian IV of Denmark. Built as an astronomical observatory, it is noted for its equestrian staircase, a 7.5-turn hel ...

, "the Round Tower"). His son Christian succeeded him in this position. Horrebow and his wife, Anne Margrethe Rossing, had a total of 20 children. In 1728, the

great fire of Copenhagen The Copenhagen Fire of 1728 was the largest fire in the history of Copenhagen, Denmark. It began on the evening of 20 October 1728 and continued to burn until the morning of 23 October. It destroyed approximately 28% of the city (measured by cou ...

destroyed all of the papers and observations made by Rømer, who had died in 1710. Horrebow wrote the ''Basis Astronomiae'' (1734–35), which describes the scientific achievements made by Rømer. Horrebow's own papers and instruments were destroyed in the same fire. Horrebow was given a special grant from the government to repair the observatory and instruments. Horrebow received further support from a wealthy patron. Horrebow invented a way to determine a place's

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

from the stars. The method fixed latitude by observing differences of

zenith The zenith (, ) is an imaginary point directly "above" a particular location, on the celestial sphere. "Above" means in the vertical direction ( plumb line) opposite to the gravity direction at that location ( nadir). The zenith is the "high ...

distances of stars culminating within a short time of each other, and at nearly the same altitude, on opposite sides of the zenith. The method was soon forgotten despite its value until it was rediscovered by the American Andrew Talcott in 1833. It is now called the ''Horrebow-Talcott Method''. He wrote on

navigation Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...

and determined the sun parallax, 9", an approximative solution to the Kepler equation. Horrebow also learned how to correct inherent flaws in instruments. This preceded

Tobias Mayer Tobias Mayer (17 February 172320 February 1762) was a German astronomer famous for his studies of the Moon. He was born at Marbach, in Württemberg, and brought up at Esslingen in poor circumstances. A self-taught mathematician, he earned a l ...

's theory of correction of 1756. Horrebow was a member of a number of scientific societies, including the

Académie des Sciences The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at th ...

(from 1746). He also worked as a medical doctor and as an academic notary (from 1720). He died in Copenhagen. The crater Horrebow on the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

is named after him.

References

Sources

Imago Mundi: Peder Horrebow

{{DEFAULTSORT:Horrebow, Peder 1679 births 1764 deaths People from Vesthimmerland Municipality 18th-century Danish astronomers 18th-century Danish mathematicians University of Copenhagen alumni Academic staff of the University of Copenhagen