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20 kroner DENMARK (2013) Scientists - Ole Rømer

20 kroner 2013 Scientists - Ole Rømer - coins of Denmark
20 kroner 2013 Scientists - Ole Rømer - obverse to reverse alignment
diameter: weight: thickness: alloy:
27.0 mm 9.3 g 2.35 mm Cu92Al6Ni2
obverse:
in the coin centre head of Queen Margrethe II of Denmark facing right; along the top edge: MARGRETHE II DANMARKS DRONNING (Margrethe II Queen of Denmark); along the bottom edge year of issue: 2013
reverse:
in the coin centre drawing by Ole Rømer showing a geometrical alignment of the Sun, Earth, Jupiter and Io in respect to each other, on the basis of which he calculated the speed of light; below a date: 1675; along the top edge: OLE RØMER • LYSETS HASTIGHED (speed of light); along the bottom edge face value: 20 KRONER
edge:
seven plain and seven reeded sections
issue date:
7 X 2013
withdrawal date:
still circulating
designer:
Lis Nogel
mint:
The Royal Mint mint mark Den Kongelige Mønt (The Royal Mint), Copenhagen (mint mark before DANMARKS on the obverse)
mintage:
2013 300 000
interesting facts:
Commemorative coin with face value of 20 kroner from 2013 commemorates world's first estimation of the speed of light by Ole Römer (1644-1710). This Danish astronomer after several years of observation of Jupiter's moon Io noted that despite his precise calculation of the orbit of Io, his calculations of the moment of Io's illumination by the Sun disagree with his observations. Rømer noticed that the error of observation time depended on the distance from Earth to Jupiter. During a lecture for the French Academy of Sciences in 1675 Rømer announced that this observation error results from a finite speed of light. He then challenged the existing theory of the infinite speed of light. He estimated that light from the Sun takes about 10 minutes to reach the Earth. Rømer was not able to calculate the speed of light, because the distance from Earth to the Sun was not known. His theory was published a year later, but confirmed only after 50 years. Today we know that light from the Sun reaches the Earth in average of 8 minutes and 19 seconds, and the light travels at speed of 299792.458 km/s.

Drawing by Ole Rømer from 1676 showing the Sun (A) and Earth in different movement phases (E,F,G,H,L,K) in respect to the moon Io (C,D) orbiting Jupiter (B).

Drawing by Ole Rømer from 1676
thematic series:
The Danish series of thematic coins "Scientists" was launched to commemorate the centenary of the publication of the atomic model by Niels Bohr. Danes decided to show that Bohr was not the only Danish, who had part in the history of scientific progress. The thematic series includes:
20 kroner (2013) Scientists - Niels Bohr 20 kroner - Scientists - Niels Bohr (2013)
20 kroner (2013) Scientists - Hans Christian Ørsted 20 kroner - Scientists - Hans Christian Ørsted (2013)
20 kroner (2013) Scientists - Ole Rømer 20 kroner - Scientists - Ole Rømer (2013)
20 kroner (2013) Scientists - Tycho Brahe 20 kroner - Scientists - Tycho Brahe (2013)
last update: 10 XII 2013

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