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In the sky - Pg. 64

Q.39: How far away is the horizon (neglecting refraction)? This is, of course, question 14, ``reloaded,'' and it leads naturally to ques- tion 40. From figure 39.1, we can approximate the distance x from an observer at O, a height h above sea level to the horizon at T. This neglects the effect of atmospheric refraction, of course, but since that increases the effective ``dis- tance'' by about 9% (see the article by French) this result represents a lower bound. Also ignored is the limiting effect of haze. By Pythagoras' theorem, if the distance OT ¼ x, then