Project Paridhi 2019

Many people believe that science is all about instrumentation and working in labs. Well, no its not! To increase awareness among public, SPACE has initiated this hands-on science activity that can be done without any complicated equipment. ‘Project Paridhi’ was started by SPACE, 9 years ago. Under this project students measure the circumference of Earth just by marking shadows made by sun as it was done by the great astronomer, Eratosthenes, 3000 years ago. This project has also been accredited in a report on ‘Astronomy in Public Places and Highways’ by French Professors, Mr. Prof. Denis Savoie and Prof. Bonnet Bidaud.


The experiment is known as Eratosthenes experiment is to measure shadow casted by a device called Gnomon (in Greek, whose shadow can be casted to measure time, especially of the hour of the day). A gnomon can be of any size, in past soft drink bottles, cricket wickets, or even tall buildings like Qutub Minar and Samrat Yantra at Jantar Mantar have been used. The shortest shadow at noon is recorded and a right- angled triangle is formed with gnomon length as the base and shortest shadow length as height. Using simple geometry and trigonometry circumference of Earth is measured.


The experiment can be conducted on any day of the year but since the Sun is directly overhead on equinoxes and solstices, it makes calculations easier. This projects also celebrates the events of solstices and equinoxes and teaches students about how are these events important and helps participants understand the change of seasons.

Further upcoming is the summer solstice for which the expected date is 21st June. Summer solstice is the day when sun reaches its highest position in the sky and which marks the longest day and shortest night in the year. This also marks the mid- summer day usually, however, in some countries it marks the beginning of summer.

Article by – Hrithik Thukral


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