Question

Suppose a sunspot the size of the Earth were completely dark. How much would that affect the brightness of the sun? Hint: What is the size of the earth compared to the size of the Sun?

Answer 1

a little i guess !!

Answer 2

Off the top of my head I vaguely recall the Sun being about 860,000 miles in diameter, and the Earth being 7927. The ratio of surface areas goes like the square of the ratio of diameters, so the Earth should have about (7927/860000)^2 = 8.5x10^-5 of the surface area of the Sun. So an Earth-sized sunspot that was completely dark would reduce the luminosity of the Sun to 99.991504% of its normal value.