Background
Ole Christensen Romer was born on September 25, 1644, in Orhus, Jutland (now Aarhus, Denmark). Romer came from a family of small merchants.
Ole Christensen Romer (1644-1710), Danish astronomer
University of Copenhagen, Copenhagen, Denmark
In 1662 Römer matriculated at the University of Copenhagen, where he studied astronomy and mathematics with Thomas (1616-1680) and Erasmus Bartholin (1625-1698).
Ole Christensen Romer (1644-1710)
Ole Christensen Romer is at work doing astronomical observations. New York Public Library/Science Source
Romer's portrait features the front of this 50 kroner note.
1676
A diagram of Jupiter (B) eclipsing its moon Io (DC) as viewed from different points in earth’s orbit around the sun. From Olaf (Ole) Roemer, “Demonstration tovchant le mouvement de la lumiere trouvé par M. Römer de l’ Academie Royale des Sciences,” December 7, 1676.
1676
A diagram of Jupiter (B) eclipsing its moon Io (DC) as viewed from different points in earth’s orbit around the sun. From Olaf (Ole) Roemer, “Demonstration tovchant le mouvement de la lumiere trouvé par M. Römer de l’ Academie Royale des Sciences,” December 7, 1676.
University of Copenhagen, Copenhagen, Denmark
In 1662 Römer matriculated at the University of Copenhagen, where he studied astronomy and mathematics with Thomas (1616-1680) and Erasmus Bartholin (1625-1698).
Ole Christensen Romer (1644-1710)
Ole Christensen Romer is at work doing astronomical observations. New York Public Library/Science Source
Romer's portrait features the front of this 50 kroner note.
Jean-Félix Picard (21 July 1620 – 12 July 1682) was a French astronomer and priest born in La Flèche, where he studied at the Jesuit Collège Royal Henry-Le-Grand. He died in Paris, France. He is principally notable for his accurate measure of the size of the Earth, based on a careful survey of one degree of latitude along the Paris Meridian.
Erasmus Bartholin, Danish scientist, physician, and grammarian.
Thomas Bartholin (Thomas Bartholinus; 20 October 1616 – 4 December 1680) was a Danish physician, mathematician, and theologian.
Astronomer mathematician physicist scientist
Ole Christensen Romer was born on September 25, 1644, in Orhus, Jutland (now Aarhus, Denmark). Romer came from a family of small merchants.
In 1662 Römer matriculated at the University of Copenhagen, where he studied astronomy and mathematics with Thomas (1616-1680) and Erasmus Bartholin (1625-1698).
After attending the University of Copenhagen in 1662, where he studied with both Thomas Bartholin, professor of medicine, and his brother Erasmus Bartholin, a physician who was better known for his discovery of double refraction of light in Iceland spar, Romer lived in Erasmus Bartholin’s house and studied astronomy and mathematics under his direction; Bartholin was so impressed with Romer’s abilities that he entrusted him with the editing of the unpublished manuscripts of Tycho Brahe.
In 1671 Erasmus Bartholin was visited by Jean Picard, who had been sent by the Academie des Sciences to measure precisely the position of Tycho Brahe’s observatory, the Uraniborg, on the island of Hven. In September of that year Bartholin and Romer accompanied Picard to Hven, where, in order to redetermine the longitude of the observatory, they made observations of a series of eclipses of the first satellite of Jupiter, while G. D. Cassini carried out the same work in Paris. When Picard returned to Paris he took with him a notebook containing eight months’ observations, the original manuscripts of Tycho Brahe’s observational works, and Romer, whom he had persuaded to work there under the auspices of the Academy.
Upon his arrival in Paris, Romer was assigned lodgings in the new Royal Observatory building designed by Charles Perrault; he lived there for nine years. He was appointed by Louis XIV to be a tutor to the dauphin and also made a number of astronomical observations, both in Paris and in other parts of France to which he was sent on behalf of the Academy. He constructed clocks and other devices, in which he displayed great mechanical skill and ingenuity, and invented a micrometer for differential measurement of the position that was so superior to previous instruments that it was speedily adopted into general use.
Romer’s greatest work, however, grew out of the problem that he had initially considered with Picard, the times of the occultations of the satellites of Jupiter. These measurements were of considerable practical use since it was recognized soon after the discovery of the Jovian satellites that their frequent occultations - particularly those of the first satellite by the planet itself represent well-defined moments of celestial time, which may be compared with time at the place of observation to establish geographical longitude. This knowledge was of particular use to mariners, and astronomers began to concern themselves with drawing up ephemerides predicting the times of eclipses at a fixed meridian, for example at Paris or Greenwich. Galileo had attempted to construct such an ephemeris, without notable success, and the task was assigned to the astronomers of the new Paris observatory by Colbert. G. D. Cassini and his nephew Maraldi discovered the first large inequality in the periodic times of the minima, that caused by the eccentricity of the orbit of Jupiter around the sun; their second discovery, announced by Cassini in August 1675, was more interesting since the inequality seemed to depend on the position of the earth relative to Jupiter.
Cassini considered, but discarded, the idea that the fluctuation of periodic times might be caused by the finite speed of light; it remained to Romer to demonstrate that such was indeed the case. With rare exceptions, previous astronomers, both ancient and more recent - including Aristotle, Kepler, and Descartes - had held that light propagated itself instantaneously. Galileo, on the other hand, was not only convinced of its finite velocity but also designed an experiment (although not an adequate one) by which the speed of light might be measured. These divergent views were discussed among the Paris academicians and were well known to Romer.
In his observational work, Romer noticed that the eclipses of Io occurred at longer intervals as the earth receded from Jupiter, but happened in closer sequence as the earth and that planet came closer together. Beginning from the point at which the earth and Jupiter were closest to each other, Romer tried to predict the time of occurrence of an eclipse of Io at a later date, when the earth and Jupiter had drawn further apart. In September 1676 he announced to the members of the Academy that the eclipse predicted for 9 November of that year would be ten minutes later than the calculations made from previous eclipses would indicate. Observations confirmed his hypothesis, and Romer correctly interpreted this phenomenon as being the result of the finite velocity of light. He was thereupon able to report to the Academy that the speed of light was such as to take twenty-two minutes for light to cross the full diameter of the annual orbit of the earth; in other terms, that the light from the sun would reach earth in eleven minutes (a time interval now measured to be about eight minutes and twenty seconds). The speed of light was thus established scientifically for the first time, with a value of about 140,000 miles per second - a reasonable first approximation to the currently accepted value of 186,282 miles per second.
Router's results were not immediately accepted by everyone. The Cassinis remained unconvinced for some time, and Descartes's view concerning the instantaneous propagation of light retained some currency. It was only after James Bradley, in 1729, discovered the periodic annual displacements in the positions of all stars in respect to the ecliptic - their aberration - that Romer'sinterpretation prevailed. The value for the time of the passage of light from the sun to the earth, deduced from Bradley’s aberration constant, was eight minutes and twelve seconds, a more accurate approximation than that originally obtained by Romer, whose result had incorporated additional perturbations of motion that he had not recognized.
In 1679 Romer undertook a scientific mission to England, where he met Newton, Flamsteed, and Halley. In 1681 he returned to Denmark to become a professor of mathematics at the University of Copenhagen. He left France at a propitious time, since four years after his departure Louis XIV revoked the Edict of Nantes, and as a Protestant Romer would surely have been forced to leave the country, as was Christiaan Huygens. Christian V of Denmark appointed Romer his astronomer royal and director of the observatory and gave him a number of technical and advisory duties; at one time or another Romer served as master of the mint, harbor surveyor, inspector of naval architecture, ballistics expert, and head of a commission to inspect highways. He performed all these tasks with distinction, and in 1688 was made a member of the privy council. In 1693 he became the first judiciary magistrate of Copenhagen and in 1694 he was made chief tax assessor, in which office he devised an efficient and equitable system of taxation.
Despite the press of other official duties, Romer did not neglect his work as an astronomer royal and director of the Copenhagen observatory. He performed a large number of astronomical observations (as many, in fact, as had Tycho Brahe) and designed and constructed astronomical instruments, particularly transit circles. The Copenhagen observatory was one of the oldest in Europe; at the time that Romer became its director, it was housed in the “Round Tower’’ built by Christian IV for Longomontanus in 1637. Romer began his observations there but soon found the site unsatisfactory. He, therefore, converted his own house into an auxiliary observatory, and in 1704 created another observatory, the Tusculaneum, located between Copenhagen and Roskilde and equipped with excellent and innovative instruments. (Indeed, Romer would seem to have been the first astronomer to have attached a telescope to a transit circle.)
Concomitant to his work in astronomical instrumentation, Romer invented the new thermometer. He was the first to recognize that the scales of thermometers designed to give concordant results must be based upon two fixed points. For this purpose he chose the boiling point of water and the melting point of snow - the same points later used by Celsius. Fahrenheit met Romer in 1708 and (according to his letter to Boerhaave in 1729) adopted so many of Romer’s ideas and techniques that the Fahrenheit thermometer should really have been named the Romer thermometer.
In 1681 Römer became an Astronomer Royal to King Christian V, and Director of the Royal Observatory. In 1704 he built his own observatory, the Tusculaneum, which he equipped with quality instruments of his own design, including the first transit circle. Römer also invented the thermometer with a scale based on two fixed points that influenced Daniel Fahrenheit's (1686-1736) thermometric researches.
Römer held many civic and advisory positions including master of the mint, harbor surveyor, and inspector of naval architecture. He was Copenhagen's first judiciary magistrate (1693), chief tax assessor (1694), and then mayor (1705). He was also appointed senator and then named head of the state council of the realm (1707).
Ole Römer's major achievement that he is famous for demonstrating the finite velocity of light. While working at the Royal Observatory in Paris, he made the first quantitative measurements of the speed of light. His determination of the speed of light demonstrated that light has a finite speed, and so doesn't travel instantaneously. In 1681, he was appointed professor of astronomy at the University of Copenhagen. As a royal mathematician, he introduced the first national system for weights and measures in Denmark in 1683. He developed one of the first temperature scales. Fahrenheit visited him in 1708 and improved on the Roemer scale, the result being the familiar Fahrenheit temperature scale still in use today in a few countries. In 1705, he was made the second Chief of the Copenhagen Police, a position he kept until his death in 1710.
His other achievements include an invention of the first street lights (oil lamps) in Copenhagen, and working hard to try to control the beggars, poor people, unemployed, and prostitutes of 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. He also invented the meridian circle and the altazimuth. He produced various scientific instruments including an improved micrometer, planetaria, the first transit circle, and an alcohol thermometer.
Romer's portrait features the front of this 50 kroner note. The structure on the right side of the front is the Rundetårn, or Round Tower, the former observatory of the University of Copenhagen from which Rømer made many of his observations. Today it's still in use for amateur astronomers. A plaque at the Observatory of Paris, where the Danish astronomer happened to be working, commemorates what was, in effect, the first measurement of a universal quantity made on this planet.
The Römer crater on the Moon is named after him.
While Römer lived at the home of Erasmus when he was a student, he eventually became his personal assistant and married his daughter Anna Marie Bartholin. At the end of his life, he died at the age of sixty-five, survived by his second wife, whom he had married in 1698. His first wife, Anna Maria, whom he married in 1681, died in 1694. He had no children.
born circa from 1581 to 1641, died in 1664
circa 1611-1690
1663-1694
1680-1763
born 1650
21 July 1620 – 12 July 1682
Thomas Bartholinus, 20 October 1616 – 4 December 1680, is a Danish physician, mathematician, and theologian. He is best known for his work in the discovery of the lymphatic system in humans and for his advancements of the theory of refrigeration anesthesia, being the first to describe it scientifically.
