Sunrise occurs before the Sun actually reaches the horizon because the Sun's image is refracted by the Earth's atmosphere. 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.
These two angles combine to define sunrise to occur when the Sun's center is 50 arcminutes below the horizon, or 90.83° from the zenith.
Other articles related to "angle, angles":
... and thinnest it is concave, and extends from the medial angle to the base of the coracoid process ... downward and backward to the inferior angle ... the three, and extends from the medial to the inferior angle ...
... allowing the transmission of an image through a right angle without inverting it (that is, without changing the image's handedness) as an ordinary right-angle prism or mirror ... internal reflection, since the beams are incident at an angle less than the critical angle (the minimum angle for total internal reflection) ... is not used optically but truncates what would otherwise be an awkward angle joining the two mirrored faces ...
... This system specifies the latitude and longitude of any location in terms of angles subtended at the centre of the Earth, using the equator and (usually) the Greenwich ... The angle between those lines can be measured, and is the angular separation between the two stars ... One could say, "The Moon's diameter subtends an angle of half a degree." The small-angle formula can be used to convert such an angular measurement into a ...
... There are 3 angles The superior angle is covered by trapezius ... The inferior angle is covered by latissimus dorsi ... The lateral or glenoid angle is broad and bears the glenoid cavity or fossa, which is directed forward, laterally and slightly upwards ...
Famous quotes containing the word angle:
“From whichever angle one looks at it, the application of racial theories remains a striking proof of the lowered demands of public opinion upon the purity of critical judgment.”
—Johan Huizinga (18721945)
“Modesty is the only sure bait when you angle for praise.”
—Philip Dormer Stanhope, 4th Earl Chesterfield (16941773)
“The good lawyer is not the man who has an eye to every side and angle of contingency, and qualifies all his qualifications, but who throws himself on your part so heartily, that he can get you out of a scrape.”
—Ralph Waldo Emerson (18031882)