Download - Triangulating the Meridian
![Page 1: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/1.jpg)
Triangulating the Meridian
Two Men’s Quest for the Meter Through War and Revolution
![Page 2: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/2.jpg)
The Astronomers and the King
• On June 19, 1791, the French Revolution was about to begin
• King Louis XVI met with two astronomers, members of the Academy of Sciences
• The King authorized a huge undertaking: measure the Earth in order to standardize the length of the meter
Jean-Dominique, comte de Cassini
King Louis XVI of France
Pierre Mechain
The Palais des Tuileries
![Page 3: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/3.jpg)
Measurements Varied
• The volume of a “standard” bushel of corn was controlled by each local community
• The standard units of length, weight, and volume might change to compensate for bad times, such as decreasing the amount of bread in each loaf
• This is called a “Just Price” economy• It was confusing and could be unfairly
manipulated
![Page 4: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/4.jpg)
Enter the Savants
• Many savants (scientists or other learned people) and legislators wanted a standard
• In 1789, the nobility renounced all their legal privileges, leading they way to new laws governing measures
• The Paris Academy of Scientists designed the new system
![Page 5: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/5.jpg)
Natural Measures
• During the French Revolution people wanted the new measures to be natural, not based on antiquated notions
• Between 1793 and 1795 France adopted a ten hour day by decree, although it was rarely used
• They tried to mandate angle measurements in 400 grads per circle (instead of 360º) but mostly failed
![Page 6: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/6.jpg)
The Meter Controls Them All
• One liter is one thousand cubic centimeters
• One gram is the weight of one cubic centimeter of water
![Page 7: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/7.jpg)
The Meridian• One meter is supposed
to be one ten millionth of the distance from the equator to the pole
• The savants needed to accurately measure the size of the earth over a long distance
• They chose Dunkirk to Barcelona
![Page 8: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/8.jpg)
Triangulation• If you know the
angles of two triangles and one side, you can find the other sides
• The astronomers used special instruments to sight from one vertex to another
![Page 9: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/9.jpg)
Solving Triangles
• To find missing sides of general triangles, use the Law of Sines and the Law of Cosines
• Actual surveying must account for height also
![Page 10: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/10.jpg)
Revolution and Adventure!
• Two expeditions set out, one north and the other south
• Several times they skirted war zones
• They were captured by the Spanish army and the Italian navy
• They climbed steep hills to windswept lookout towers that marked each vertex
![Page 11: Triangulating the Meridian](https://reader036.vdocument.in/reader036/viewer/2022062322/568144bd550346895db185b4/html5/thumbnails/11.jpg)
CreditsImages:
Cassini - http://en.wikipedia.org/wiki/File:Jean_%28Jacques%29_Dominique_de_Cassini.jpg,Mechain - http://commons.wikimedia.org/wiki/File:Pierre_mechain.jpgLouis XVI - http://www.educatorunderground.com/bios/Louis%20XVI.htmlThe Palais des Tuileries - http://saint-sevin.pagesperso-orange.fr/pageg.htmMerdian map and triangulation map from The Measure of All Things, Ken Adler, 2002