Cosmos ladder from Tao’s lectures

Just a quotation (Terence Tao, Cosmic Distance Ladder)-

Aristarchus knew that lunar eclipses were caused by the Moon passing through the Earth’s shadow.
Aristarchus knew that lunar eclipses were caused by the Moon passing through the Earth’s shadow.
The Earth’s shadow is approximately two Earth radii wide.
The maximum length of a lunar eclipse is three hours
It takes one month for the Moon to go around the Earth.
This is enough information to work out the distance to the Moon in Earth radii.
Also, the Moon takes about 2 minutes to set.
The Moon takes 24 hours to make a full (apparent) rotation around the Earth.
This is enough information to determine the radius of the Moon, in terms of the distance to the Moon…
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About misha

Imagine a story that one can't believe. Hi. Life changes here. Small things only.
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