The suns rays were strong as they glowed through the tree casting a bright array of beams to lighten the day. Sunrise actually occurs before the Sun truly reaches the horizon because Earth`s atmosphere refracts the Sun`s image. At the horizon, the average amount of refraction is 34 arcminutes, though this amount varies based on atmospheric conditions. Also, unlike most other solar measurements, sunrise occurs when the Sun`s upper limb, rather than its center, appears to cross the horizon. The apparent radius of the Sun at the horizon is 16 arcminutes.
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