Visibility of eTwinning Projects Group July 2023 Newsletter
shadow and its direction towards the north . The pupils created slideshow and time lapse video . It is interesting to locate solar noon on the day of the equinox , because the end of the shadow traces a straight line during this day .
The pupils from the 19 countries were ready to measure or calculate the angle of the sun towards the vertical . On a same day , they tried to compare results and their accuracy with different methods of gnomons . In addition , they produced Slideshows or . pdf materials of the observations . They were conscious that the notion of alternate interior angles is necessary to draw Eratosthenes geometric figure . They showed that the angles that lie on the inner side of the parallel lines but on the opposite sides of the transversal are equal .
Our pupils analysed the Astronomical events : March 20th Equinox ; April 05th Zero Shadow Day ; May 09th Zero Shadow Day . The changes of seasons are astronomical events when the sun is directly above are : 1 ) the Equator on March and September equinoxes ; 2 ) the Tropic of Cancer on June solstice and 3 ) the Tropic of Capricorn on December solstice . Between the 2 tropics , there are special days , special places , when and where the sun casts no shadow at noon . On those zero shadow days , the observations are the same as those of the first Eratosthenes experiment between Alexandria and Aswan , 2200 years ago .
The quality of the measures was evaluated on March equinox . Thus , 26 schools realized 46 measures of the angle of the sun from 17 to 23 March at solar noon . This angle decreases by 0.4 ° per day and is equal to the latitude on the day of the equinox ( taking into account the measurement errors . To allow the participation of the largest number of schools , measurements are not only carried out on the
day of the equinox , but also from 3 days before this date until 3 days after . The measurement procedure is thus adapted , limiting the problems of bad weather conditions as well as the fact that the day of the equinox falls on a Sunday .
During these 7 days , the partner schools exchanged the results of their measurements of the height of their gnomon and the length of its shadow at solar noon , which define the angle of the sun at that moment . It was not necessary for these schools to be located on the same meridian . These measurements being synchronized at solar noon , it was indeed the distance between the parallels passing through these 2 schools which was used to calculate the circumference of the Earth .
The historical measurement of Eratosthenes took place during the summer solstice , with Tropic of Cancer as a reference , for instance the place where the Sun is at its zenith on this date . These conditions are also fulfilled on the day of the equinox for all places located on the equator . The measurements of March 20 but also those carried out during the week , thanks to a regression calculation , made it possible to verify that latitude and angle of the Sun are equal on the day of the equinox .
The dissemination of the project activities is made by newsletters , presentations of local activities of each school , as well as the actions dedicated to Pi Day , Math Day , and Eratosthenes Festivity . Eratosthenes Festivity takes place on 21 June of every year at the BA and in Aswan city . It is designed for preparatory school students and includes a series of activities that revolve around Eratosthenes ' s methodology in measuring the Earth ’ s circumference 2000 years ago .
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