Peder Horrebow

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Peder Horrebow


Peder Horrebow
Born 14 May 1679
Løgstør, Jutland
Died 15 April 1764
Nationality Flag of Denmark.svg Denmark
Scientific career
Fields astronomy

Peder [Nielsen] Horrebow (Horrebov) (14 May 1679 – 15 April 1764) was a Danish astronomer. Born in Løgstør, Jutland to a poor family of fishermen, Horrebow entered the University of Copenhagen 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 writer in 1711.

Denmark constitutional monarchy in Europe

Denmark, officially the Kingdom of Denmark, is a Nordic country and the southernmost of the Scandinavian nations. Denmark lies southwest of Sweden and south of Norway, and is bordered to the south by Germany. The Kingdom of Denmark also comprises two autonomous constituent countries in the North Atlantic Ocean: the Faroe Islands and Greenland. Denmark proper consists of a peninsula, Jutland, and an archipelago of 443 named islands, with the largest being Zealand, Funen and the North Jutlandic Island. The islands are characterised by flat, arable land and sandy coasts, low elevation and a temperate climate. Denmark has a total area of 42,924 km2 (16,573 sq mi), land area of 42,394 km2 (16,368 sq mi), and the total area including Greenland and the Faroe Islands is 2,210,579 km2 (853,509 sq mi), and a population of 5.8 million.

Løgstør Town in Region Nordjylland, Denmark

Løgstør is a town in Denmark with a population of 4,284 It is located 47 km west of Aalborg and 64 km north of Viborg. Løgstør city centre consist of old streets with small houses built in the 1800s for fishermen and sailors. One of these houses was donated by Danish housemen to the author and poet Johan Skjoldborg in 1918, who lived in the house until his death. It is located on Johan Skjoldborgs Vej.

Jutland mainland of Denmark, a peninsula north of Germany

Jutland, also known as the Cimbric or Cimbrian Peninsula, is a peninsula of Northern Europe that forms the continental portion of Denmark and part of northern Germany. The names are derived from the Jutes and the Cimbri, respectively.

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"). His son Christian succeeded him in this position. Horrebow and his wife, Anne Margrethe Rossing, had a total of 20 children. [1]

Frederick IV of Denmark King of Denmark and Norway

Frederick IV was the king of Denmark and Norway from 1699 until his death. Frederick was the son of King Christian V of Denmark-Norway and his consort Charlotte Amalie of Hesse-Kassel.

Observatory location used for observing terrestrial or celestial events

An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geophysical, oceanography and volcanology are examples of disciplines for which observatories have been constructed. Historically, observatories were as simple as containing an astronomical sextant or Stonehenge.

Christian Pedersen Horrebow was a Danish astronomer of the 18th century. He was a son of Peder Horrebow, whom he succeeded as director of the observatory associated with the University of Copenhagen.

In 1728, the great fire of Copenhagen 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.

Copenhagen Fire of 1728 conflagration

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, left 20% of the population homeless, and the reconstruction lasted until 1737. No less than 47% of the section of the city, which dates back to the Middle Ages, was completely lost, and along with the Copenhagen Fire of 1795, it is the main reason that few traces of medieval Copenhagen can be found in the modern city.

Horrebow invented a way to determine a place's latitude from the stars. The method fixed latitude by observing differences of zenith 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.

Latitude The angle between zenith at a point and the plane of the equator

In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle which ranges from 0° at the Equator to 90° at the poles. Lines of constant latitude, or parallels, run east–west as circles parallel to the equator. Latitude is used together with longitude to specify the precise location of features on the surface of the Earth. On its own, the term latitude should be taken to be the geodetic latitude as defined below. Briefly, geodetic latitude at a point is the angle formed by the vector perpendicular to the ellipsoidal surface from that point, and the equatorial plane. Also defined are six auxiliary latitudes which are used in special applications.


The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere. "Above" means in the vertical direction opposite to the apparent gravitational force at that location. The opposite direction, i.e. the direction in which gravity pulls, is toward the nadir. The zenith is the "highest" point on the celestial sphere.

Andrew Talcott American civil engineer

Andrew Talcott (1797–1883) was an American civil engineer and close friend of Civil War General Robert E. Lee. He did not serve during the Civil War, as he could not fight against the Union, nor fight against his brothers in the South. He traveled to Veracruz to work on the Railroad. Coming back with the President to New York for supplies he was arrested and placed at Fort Layfayette accused of being a spy for the Confederate States of America. He was moved to Fort Adams in Boston under orders of General John E Wool. General John A Dix was placed in the command of the Eastern Military Department. Knowing Captain Andrew well and believing his loyalty to the Union he was released.

He wrote on 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's theory of correction of 1756.

Navigation The process of monitoring and controlling the movement of a craft or vehicle from one place to another

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. The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation.

Parallax difference in the apparent position of an object viewed along two different lines of sight

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects show a larger parallax than farther objects when observed from different positions, so parallax can be used to determine distances.

Tobias Mayer German astronomer

Tobias Mayer was a German astronomer famous for his studies of the Moon.

Horrebow was a member of a number of scientific societies, including the Académie des Sciences (from 1746). He also worked as a medical doctor and as an academic notary (from 1720).

He died in Copenhagen.

Illustration from Basis astronomiae sive Astronomiae pars mechanica... Acta Eruditorum, March 1736 Acta Eruditorum - IV strumenti, 1736 - BEIC 13456523.jpg
Illustration from Basis astronomiae sive Astronomiae pars mechanica... Acta Eruditorum, March 1736

The crater Horrebow on the Moon is named after him.

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  1. Hockey, Thomas (2009). The Biographical Encyclopedia of Astronomers. Springer Publishing. ISBN   978-0-387-31022-0 . Retrieved August 22, 2012.