<P> Variations in atmospheric refraction can alter the time of sunrise by changing its apparent position . Near the poles, the time - of - day variation is exaggerated, since the Sun crosses the horizon at a very shallow angle and thus rises more slowly . </P> <P> Accounting for atmospheric refraction and measuring from the leading edge slightly increases the average duration of day relative to night . The sunrise equation, however, which is used to derive the time of sunrise and sunset, uses the Sun's physical center for calculation, neglecting atmospheric refraction and the non-zero angle subtended by the solar disc . </P> <P> Neglecting the effects of refraction and the Sun's non-zero size, whenever sunrise occurs, in temperate regions it is always in the northeast quadrant from the March equinox to the September equinox and in the southeast quadrant from the September equinox to the March equinox . Sunrises occur approximately due east on the March and September equinoxes for all viewers on Earth . Exact calculations of the azimuths of sunrise on other dates are complex, but they can be estimated with reasonable accuracy by using the analemma . </P> <P> Air molecules and airborne particles scatter white sunlight as it passes through the Earth's atmosphere . This is done by a combination of Rayleigh scattering and Mie scattering . </P>

Where does the morning sun began to rise
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