How do you measure the circumference of the earth using sun angles?

1 Answer
Feb 1, 2016

This is a bit tricky...!

Explanation:

You need two spots on the surface of the Earth, A and B.
When standing at A you produce a shadow while standing at B (at the same hour of the day, say, midday) you do not produce a shadow.
enter image source here
You can evaluate, from trigonometry, the angle θ using your height h and the length of the shadow l as:
θ=arctan(lh)
and knowing the arclength s you can find the radius r using the fact that:
s=rθ
giving:
r=sθ
and then use C=2πr for the circumference.

Hope it is understandable...