All of North America seems to be excited about April’s total solar eclipse. But not many know the story of how ancient astronomers used the observations of an eclipse to estimate the distance of the Earth to the Moon.
Some 2100 years ago, a solar eclipse had cast its shadow across the eastern Mediterranean region.
Observers back then had no fancy sunglasses to observe the phenomena and no maps from space agencies that plotted every single second of the shadow’s progress along the earth’s surface.
But they did have geometry.
And because of a keen eye of observation, along with some interesting assumptions regarding the distance of the stars and sun, early Greek astronomers were able to use their understanding of the angles within a triangle to estimate the distance from the Earth to the Moon.
Electric Book Company’s Origins by Geometry line describes the work done by the ancient Greek astronomer Hipparchus as he used information about the amount of sunlight that bled through the edge of the Moon’s disk to estimate the Moon’s distance.
The chapter ‘Hipparchus Estimates Distance to the Moon’ goes into the details of his work which gave a reasonable estimate – considering the only tools they had were the eyes to observe and some rudimentary geometric propositions.
Give the chapter a look. And those who choose this month’s eclipse – please do so safely!