- #1

Puchinita5

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## Homework Statement

My homework involves calculating the amount of energy the Earth receives from the Sun in a given year. I actually have the answer, but what I'm confused with is that the calculation says that the Sun "sees the cross section of the Earth, a circle". So in the calculation, we multiply the energy per square meter received at 1AU by pi*R^2 (R is the radius of the Earth).

Why isn't it multiplied by half of the surface area of Earth? I picture half of the Earth facing the sun as the surface receiving the energy. So I would think to multiply by 2*pi*r^2.