Visibility of eTwinning Projects Group July 2025 Newsletter
Lesson Plan for an Activity in the eTwinning STE( A) M Eratosthenes Project – Activity Integrated into the Curriculum by Iuliana Ciubuc and Mădălina Neagoe
Sparking curiosity Have you ever wondered how Earth can be compared to us? Since the Earth is so big, do you think it is possible to measure its size without using satellites? What if you could do that in your school, using only a stick – do you think it is possible?
The teacher uses Google Earth to offer the children a brief demonstration. The purpose of this demonstration is to impress the students by showing them how small we are compared to the size of the Earth.
The teacher informs the students that Eratosthenes measured the Earth ' s circumference over 2,200 years ago using only a stick( gnomon) and the position of the Sun( local solar time).
Content We define the objectives and / or questions based on prior knowledge.
• Do we know that the Earth is round? Since the Earth is round, its circumference is actually a circle.
• How many degrees are there in a full circle?
• What is an arc of a circle?
• Can we calculate the full circumference if we know the length of the arc that corresponds to a given angle?
• If we have two locations on Earth, what is the angle between them?
• How can we measure it?
The teacher explains to the students how Eratosthenes concluded that the Earth is a sphere by looking at the shadow it casts on the Moon. The teacher presents how the angular distance between two locations can be measured. Students need to understand the key idea: if we know the angle and the arc that corresponds to this angle, we can calculate the entire circumference.
Moreover, a hundred years before Eratosthenes, Aristotle( 384 – 322 BC) offered three classical proofs that the Earth is spherical:
First of all, during lunar eclipses, the edge of the shadow cast by the Earth on the Moon is always a circular arc, and the only body capable of casting such a shadow from any position and light direction is a sphere.
Secondly, ships sailing away from an observer at sea do not gradually disappear due to distance, but almost instantly seem to“ sink,” vanishing beyond the horizon line.
Third, some stars are visible only from certain parts of the Earth, and for other observers, they are never visible.
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