The Solar constant reference article from the English Wikipedia on 24-Jul-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Solar constant

The solar constant is the amount of incoming solar radiation per unit area, measured on the outer surface of Earth's atmosphere, in a plane perpendicular to the rays. It is calculated to be roughly 1367 watts per square metre.

Thus, for the whole Earth, with a cross-section of 125,000,000 km², the power is 170 petawatt.

The angular diameter of Earth seen from the sun is ca. 1/11,000 radian, so the solid angle of Earth seen from the sun is ca. 1/140,000,000 steradian.

Thus, what the sun emits is about 2 billion times the amount caught by Earth.

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