• Question: What is the circumference of the earth?

    Asked by sciencetube145 to Gioia, Iain, Jo, Leo, Mariam on 19 Jun 2010 in Categories: .
    • Photo: Joanna Watson

      Joanna Watson answered on 17 Jun 2010:

      Sorry sciencetube145 – I don’t know.

    • Photo: Mariam Orme

      Mariam Orme answered on 18 Jun 2010:

      The earth isn’t completely round. The circumference at the Equator is around 24900 miles (40075 km), while the circumference going through the North and South Poles is a bit smaller at 24860 miles (40008 km).

    • Photo: Leo Garcia

      Leo Garcia answered on 19 Jun 2010:

      The circumference of the earth at the equator is 24,901.55 miles (40,075.16 kilometers).

      http://geography.about.com/library/faq/blqzcircumference.htm

      That’s a long way round!

    • Photo: Iain Moal

      Iain Moal answered on 19 Jun 2010:

      Its about 25,000 miles. What I find amazing is the way this number was first found out, about two thousand years ago, by a man called Eratosthenes.

      He was reading a book that had an anacdote which most people wouldn’t have paid much attention to, about a very deep well in Egypt. It said that, on one day every year, the sunlight reached the bottom of the well, and reflected on the water. He realised that, on this day, the sun must be directly above the well. He reasoned that if the earth was flat, then on that day, the light should reflect on the water in every well. He also realised that he could also check ithis with a stick. If the stick didn’t have a shadow, then the sun was directly above the stick.

      So, what he did was to put sticks in two diffrent places, about 25 kilometers apart and realised that when one stick had no shadow, the other stick DID have a shadow. Not only that, but he measured the length of the shadow and calculated the curvature of the earth. From this, he could calculate the circumference of the earth.

      So that is how, two thousand years ago, a man managed to calculate the circumference of the earth, using nothing but a stick and a ruler! Amazing.

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