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Local astronomers share Mercury transit photo

By Sun Advocate

Astronomy fans Eddie Horvath and Mark Bunnell captured this photo of the Mercury transit across the solar disc Monday morning. Note the relative sizes of the little planet and an ordinary sunspot. Earth would look slightly bigger if our planet’s transit were seen from Jupiter. Time for some fun with math. How much of the Sun’s radiation does Earth get? Here’s our solution. Double check for yourself. Picture a colossal spherical balloon with the Sun at the center and Earth’s illuminated surface as a tiny circle on the skin of the balloon. The radius of the balloon is the distance from us to the Sun, 93 million miles. The interior surface area of the ballon, entirely lit by the Sun, is 4π r2, or 9.9 x 1016 square miles. The illuminated disc of the Earth is only about 50 million square miles, or 5 x 107 . We came up with a share of about 5 x 10-10, or 0.0000000005 of the Sun’s total output. Hope we haven’t made a careless arithmetic mistake, but our math seems reasonable.

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