Ole Rømer.

Ole Christensen Rømer (September 25, 1644 – September 19, 1710) was a Danish astronomer who made the first quantitative measurements of the speed of light (1676). Rømer was born in Aarhus and died in Copenhagen. (PD by age) File links The following pages link to this file: Ole Rømer Categories: Public domain images ... (PD by age) File links The following pages link to this file: Ole Rømer Categories: Public domain images ... September 25 is the 268th day of the year (269th in leap years). ... Events February to August - Explorer Abel Tasmans second expedition for the Dutch East India Company maps the north coast of Australia. ... September 19 is the 262nd day of the year (263rd in leap years). ... Events April 10 - The worlds first copyright legislation became effective, Britains Statute of Anne Ongoing events Great Northern War (1700-1721) War of the Spanish Succession (1702-1713) Births January 4 - Giovanni Battista Pergolesi, Italian composer (d. ... An astronomer or astrophysicist is a scientist whose area of research is astronomy or astrophysics. ... Measurement is the determination of the size or magnitude of something. ... Cherenkov effect in a swimming pool nuclear reactor. ... Events January 29 - Feodor III becomes Tsar of Russia First measurement of the speed of light, by Ole Rømer Bacons Rebellion Russo-Turkish Wars commence. ... View of Aarhus from the harbor. ... City nickname: none Location in Denmark Area  - Total  - Water 526 km² xxx km² xx% Population  - City (2004)  - Metropolitan  - Density 502,204 1,116,979 954/km2 [including water] xxx/km2 [land only] Time zone Eastern: UTC+1 Latitude Longitude 55°43 N 12°34 W Copenhagen (Danish: København) is...

General biography

the Rundetårn, or round tower, in Copenhagen, on top of which the university had its observatory from the mid 17th century until the mid 19th century, when it was moved to new premises. The current observatory there was built only in the 20th century to serve amateurs.

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. Download high resolution version (1536x2048, 344 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (1536x2048, 344 KB) Wikipedia does not have an article with this exact name. ... (Louis-Dieudonné) (September 5, 1638 – September 1,rance]] and King of Navarre from May 14, 1643 until his death. ... The Dauphin was the heir apparent to the throne of France under the Valois and Bourbon dynasties. ... An ornamental lit fountain photographed at night for about 6 seconds. ... Versailles, formerly the capital city of the kingdom of France, is now a wealthy suburb of Paris and is still an important administrative and judicial center. ...

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. Events March 4 - Charles II of England grants a land charter to William Penn for the area that will later become Pennsylvania. ... Astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and monitoring of transient phenomena. ... University of Copenhagen The University of Copenhagen (Danish: Københavns Universitet) is the oldest and largest university and research institution in Copenhagen, Denmark. ... Categories: Stub | Astronomical observatories ... Rundetårn. ... Events Astronomical aberration discovered by the astronomer James Bradley Swedish academy of sciences founded at Uppsala Births January 9 - Thomas Warton, English poet (d. ...

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. May 1 is the 121st day of the year in the Gregorian calendar (122nd in leap years). ... Events June 6 - The Ashmolean Museum opens as the worlds first university museum. ... Events January 4 - Palace of Whitehall in London is destroyed by fire. ... A gravity pendulum is a weight on the end of a rigid rod (or a string/rope), which, when given an initial push, will swing back and forth under the influence of gravity over its central (lowest) point. ... The geographical mile is a unit of length determined by 1 minute of arc along the Earths equator, approximately equal to 1855 metres (6087. ... There are several traditions of navigation. ...

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. Events January 1 - Russia accepts Julian calendar. ... The Gregorian calendar is the calendar widely used in the Western world. ... Tycho Brahe (December 14, 1546 Knudstrup, Denmark – October 24, 1601 Prague, Bohemia (now Czech Republic)) was a Danish nobleman, well known as an astronomer/astrologer (the two were not yet distinct) and alchemist. ...

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. Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... Daniel Gabriel Fahrenheit, also called Gabriel Daniel Fahrenheit (May 24, 1686 - September 16, 1736), was a physicist and an engineer, who most of his life worked in Netherlands and for whom the Fahrenheit scale of temperature is named. ... Events March 23 - James Francis Edward Stuart lands at the Firth of Forth September 28 - Peter the Great defeats the Swedes at the Battle of Lesnaya Kandahar conquered by Mir Wais In Masuria one third of the population die during the plague J.S. Bach appointed as chamber musician and... Rømer is a disused temperature scale named after the Danish astronomer Ole Christensen Rømer, who proposed it in 1701. ... Fahrenheit is a temperature scale named after the German physicist Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ...

He also established several navigation schools in many Danish cities.

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 and control the beggars, poor people, unemployed, and prostitutes of Copenhagen. This was the start of a social reform. Events Construction begins on Blenheim Palace, in Oxfordshire, England. ... Events April 10 - The worlds first copyright legislation became effective, Britains Statute of Anne Ongoing events Great Northern War (1700-1721) War of the Spanish Succession (1702-1713) Births January 4 - Giovanni Battista Pergolesi, Italian composer (d. ...

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.

Inventions

As well as inventing the first street lights in Copenhagen, Ole Rømer also invented the Meridian Circle, the Altazismuth and the Passage Instrument.

Rømer and the speed of light

The determination of longitude is a significant practical problem in cartography and navigation. King Philip III of Spain offered a prize for a method to determine the longitude of a ship out of sight of land. Galileo proposed a method of establishing the time of day, and thus longitude, based on the times of the eclipses of the moons of Jupiter, in essence using the Jovian system as a cosmic clock; this method was not significantly improved until accurate mechanical clocks were developed in the eighteenth century. Galileo proposed this method to the Spanish crown (1616-1617) but it proved to be impractical, because of the inaccuracies of Galileo's timetables and the difficulty of observing the eclipses on a ship. However, with refinements the method could be made to work on land. Map of Earth showing curved lines of longitude Longitude, sometimes denoted λ, describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. ... Cartography or mapmaking (in Greek chartis = map and graphein = write) is the study and practice of making maps or globes. ... There are several traditions of navigation. ... Galileo Galilei (Pisa, February 15, 1564 – Arcetri, January 8, 1642), was a Tuscan astronomer, philosopher, and physicist who is closely associated with the scientific revolution. ... A clock (from the Latin cloca, bell) is an instrument for measuring time. ... (17th century - 18th century - 19th century - more centuries) As a means of recording the passage of time, the 18th century refers to the century that lasted from 1701 through 1800. ... Events Dirk Hartog lands on an island off the Western Australian coast Pocahontas arrives in England War between Venice and Austria Collegium Musicum founded in Prague Nicolaus Copernicus De revolutionibus is placed on the Index of Forbidden Books by the Roman Catholic Church Births May 18 - Johann Jakob Froberger, German... Events Change of emperor of the Ottoman Empire from Ahmed I (1603-1617) to Mustafa I (1617-1623). ...

After studies in Copenhagen, Rømer joined the observatory of Uranienborg on the island of Hven, near Copenhagen, in 1671. Over a period of several months, Jean Picard and Rømer observed about 140 eclipses of Jupiter's moon Io, while in Paris Giovanni Domenico Cassini observed the same eclipses. By comparing the times of the eclipses, the difference in longitude of Paris to Uranienborg was calculated. Uraniborg was the astronomical/astrological observatory of Tycho Brahe; built circa 1576-1580 on Hven (also known as Ven or Hveen), an island in the Öresund; between Zealand and Scania. ... Hven, or Ven, is a small Swedish island in the Öresund strait, between Scania and Zealand. ... Events May 9 - Thomas Blood, disguised as a clergyman, attempts to steal the Crown Jewels from the Tower of London. ... Jean-Felix Picard (July 21, 1620 – July 12, 1682) was a French astronomer and priest born in La Fleche. ... Atmospheric characteristics Atmospheric pressure trace Sulfur dioxide 90% Io (eye-oh, Greek Ιώ) is the innermost of the four Galilean moons of Jupiter. ... Giovanni Domenico (Jean-Dominique) Cassini Giovanni Domenico Cassini (June 8, 1625 - September 14, 1712) was an Italian-French astronomer and engineer. ...

Cassini had observed the moons of Jupiter between 1666 and 1668, and discovered discrepancies in his measurements that, at first, he attributed to light having a finite speed. In 1672 Rømer went to Paris and continued observing the satellites of Jupiter as Cassini's assistant. Rømer added his own observations to Cassini's and observed that times between eclipses (particularly Io's) got shorter as Earth approached Jupiter, and longer as Earth moved farther away. Cassini published in August of 1675 a short paper where he states: Events September 2 - Great Fire of London: A large fire breaks out in London in the house of Charles IIs baker on Pudding Lane near London Bridge. ... Events January - The Triple Alliance of 1668 is formed. ... Events England, France, Munster and Cologne invade the United Provinces, therefore this name is know as ´het rampjaar´ (the disaster year) in the Netherlands. ... The Eiffel Tower has become a symbol of Paris throughout the world. ... Events January 5 - The Battle of Turckeim August 10 - Building of the Royal Greenwich Observatory began November 11 - Guru Gobind Singh becomes the Tenth Guru of the Sikhs. ...

Cette seconde inégalité paraît venir de ce que la lumière emploie quelques temps à venir du satellite jusqu'à nous, et qu'elle met environ dix à onze minutes à parcourir un espace égal au demi-diamètre de l'orbite terrestre.

(translation)

This second inequality appears to be due to light taking some time to reach us from the satellite; light seems to take about ten to eleven minutes to cross a distance equal to the half-diametre of the terrestrial orbit.

Oddly, Cassini seems to have abandoned this hypothesis, which Rømer adopted and set about buttressing in an irrefutable manner. He estimated that the time for light to travel the diameter of the Earth's orbit, a distance of two astronomical units, was 22 minutes. This is somewhat greater than the currently accepted value, which is about 16 minutes and 40 seconds. The astronomical unit (AU or au or a. ...

His discovery was presented to the Académie royale des sciences and summarised soon after in a short paper, "Démonstration touchant le mouvement de la lumière trouvé par M. Roemer de l'Académie des sciences", in the Journal des scavans, December 7, 1676. In the paper, he stated « that for the distance of about 3000 leagues, such as is very near the bigness of the diameter of the Earth, light needs not one second of time ». He went so far as accurately predicting the delay that the November 9, 1676 eclipse of Io would have: 10 minutes. 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 French Academy of Sciences (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. ... December 7 is the 341st day (342nd on leap years) of the year in the Gregorian calendar. ... Events January 29 - Feodor III becomes Tsar of Russia First measurement of the speed of light, by Ole Rømer Bacons Rebellion Russo-Turkish Wars commence. ... November 9 is the 313th day of the year (314th in leap years) in the Gregorian Calendar, with 52 days remaining. ... Events January 29 - Feodor III becomes Tsar of Russia First measurement of the speed of light, by Ole Rømer Bacons Rebellion Russo-Turkish Wars commence. ...

As Rømer had no accurate value for the astronomical unit, he gave no value for the speed in his paper beyond the aforementioned lower bound. However, many others calculated a speed from his data, the first being Christiaan Huygens; after corresponding with Rømer and eliciting more data, Huygens deduced that light travelled 16.6 Earth diameters per second. If Rømer had used his own estimates of the Earth to Sun distance at that time, he would have obtained a speed of about 135,000 km/s. Christiaan Huygens Christiaan Huygens (pronounced in English ( IPA): ; in Dutch: ) ( April 14, 1629– July 8, 1695), was a Dutch mathematician and physicist; born in The Hague as the son of Constantijn Huygens. ...

Rømer's view that the velocity of light was finite was not fully accepted until measurements of the so-called aberration of light were made by James Bradley in 1727. In 1809, again making use of observations of Io, but this time with the benefit of more than a century of increasingly precise observations, Delambre reported the time for light to travel from the Sun to the Earth as 8 minutes and 12 seconds. Depending on the value assumed for the astronomical unit, this yields the speed of light as just a little more than 300,000 kilometres per second. Aberration of light (also referred to as astronomical aberration or stellar aberration) is an astronomical phenomenon defined as an apparent motion of the heavenly bodies; stars describing more or less elliptic annual orbits, according to the latitude of the star; consequently at any moment the star appears to be displaced... see Jim Bradley for the Ontario Member of Provincial Parliament James Bradley (1693 - July 13, 1762) was an English astronomer, Astronomer Royal from 1742. ... Events June 11 - George, Prince of Wales becomes King George II of Great Britain. ... 1809 was a common year starting on Sunday (see link for calendar). ... Cherenkov effect in a swimming pool nuclear reactor. ... A kilometre (American spelling: kilometer, symbol: km) is a unit of length equal to 1000 metres (from the Greek words khilia = thousand and metro = count/measure). ... This article is about the unit of time. ...

References

• R.J. MacKay and R.W. Oldford. "Scientific Method, Statistical Method and the Speed of Light", Statistical Science 15(3):254–278, 2000. (mostly about A.A. Michelson, but considers forerunners including Rømer. Also available on line: [1] (http://www.stats.uwaterloo.ca/~rwoldfor/papers/sci-method/paperrev))

Albert Abraham Michelson. ...

External links

• Roemer, Ole Christensen (http://galileo.rice.edu/Catalog/NewFiles/roemer.html) (at the Galileo Project (http://galileo.rice.edu))

• ROEMER, Démonstration touchant le mouvement de la lumière (http://astro.campus.ecp.fr/histoire/roemer.html) (Rømer's 1676 paper, in French, as ordinary text)

• A Demonstration concerning the Motion of Light, communicated from Paris (http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Roemer-1677/Roemer-1677.html) (Rømer's 1676 paper, in English and French, as bitmap images)

• Rømer and the Doppler Principle. (http://www.rundetaarn.dk/engelsk/observatorium/light.htm) (further details on Rømer's result)

• Fysikeren Ole Rømer (http://www.rundetaarn.dk/dansk/observatorium/indledning.htm) (in Danish)