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Rising Sun

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Sunrise (or sunup ) is the moment when the upper rim of the Sun appears on the horizon in the morning , at the start of the Sun path . The term can also refer to the entire process of the solar disk crossing the horizon.

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30-517: Rising sun may refer to sunrise . Rising Sun or The Rising Sun may also refer to: Sunrise Although the Sun appears to "rise" from the horizon, it is actually the Earth's motion that causes the Sun to appear. The illusion of a moving Sun results from Earth observers being in a rotating reference frame ; this apparent motion caused many cultures to have mythologies and religions built around

60-418: A combination of Rayleigh scattering and Mie scattering . As a ray of white sunlight travels through the atmosphere to an observer, some of the colors are scattered out of the beam by air molecules and airborne particles , changing the final color of the beam the viewer sees. Because the shorter wavelength components, such as blue and green, scatter more strongly, these colors are preferentially removed from

90-422: A non-piecewise expression by G.G. Bennett used in the U.S. Naval Observatory's "Vector Astronomy Software". The generalized equation relies on a number of other variables which need to be calculated before it can itself be calculated. These equations have the solar-earth constants substituted with angular constants expressed in degrees. where: where: where: where: where: where: where: Alternatively,

120-400: Is due to Rayleigh scattering by air molecules and particles much smaller than the wavelength of visible light (less than 50 nm in diameter). The scattering by cloud droplets and other particles with diameters comparable to or larger than the sunlight's wavelengths (more than 600 nm) is due to Mie scattering and is not strongly wavelength-dependent. Mie scattering is responsible for

150-554: Is equal to π 180 {\displaystyle {\frac {\pi }{180}}} , and dpr is equal to 180 π {\displaystyle {\frac {180}{\pi }}} . The above expression gives results in degree in the range [ 0 ∘ , 180 ∘ ] {\displaystyle [0^{\circ },180^{\circ }]} . When ω ∘ = 0 ∘ {\displaystyle \omega _{\circ }=0^{\circ }} , it means it

180-401: Is instead lofted into the stratosphere (as thin clouds of tiny sulfuric acid droplets), can yield beautiful post-sunset colors called afterglows and pre-sunrise glows. A number of eruptions, including those of Mount Pinatubo in 1991 and Krakatoa in 1883 , have produced sufficiently high stratospheric sulfuric acid clouds to yield remarkable sunset afterglows (and pre-sunrise glows) around

210-516: Is polar night, or 0-hour daylight; when ω ∘ = 180 ∘ {\displaystyle \omega _{\circ }=180^{\circ }} , it means it is polar day, or 24-hour daylight. Suppose ϕ N {\displaystyle \phi _{N}} is a given latitude in Northern Hemisphere, and ω ∘ N {\displaystyle \omega _{\circ N}}

240-511: Is the corresponding sunrise hour angle that has a negative value, and similarly, ϕ S {\displaystyle \phi _{S}} is the same latitude but in Southern Hemisphere, which means ϕ S = − ϕ N {\displaystyle \phi _{S}=-\phi _{N}} , and ω ∘ S {\displaystyle \omega _{\circ S}}

270-585: Is the corresponding sunrise hour angle, then it is apparent that which means The above relation implies that on the same day, the lengths of daytime from sunrise to sunset at ϕ N {\displaystyle \phi _{N}} and ϕ S {\displaystyle \phi _{S}} sum to 24 hours if ϕ S = − ϕ N {\displaystyle \phi _{S}=-\phi _{N}} , and this also applies to regions where polar days and polar nights occur. This further suggests that

300-583: Is typically that the observer latitude ϕ {\displaystyle \phi } is 0 at the equator , positive for the Northern Hemisphere and negative for the Southern Hemisphere , and the solar declination δ {\displaystyle \delta } is 0 at the vernal and autumnal equinoxes when the sun is exactly above the equator, positive during the Northern Hemisphere summer and negative during

330-530: 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. 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

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360-463: The axial tilt of Earth, daily rotation of the Earth, the planet's movement in its annual elliptical orbit around the Sun , and the Earth and Moon's paired revolutions around each other . The analemma can be used to make approximate predictions of the time of sunrise. In late winter and spring, sunrise as seen from temperate latitudes occurs earlier each day, reaching its earliest time shortly before

390-416: The geocentric model , which prevailed until astronomer Nicolaus Copernicus formulated his heliocentric model in the 16th century. Architect Buckminster Fuller proposed the terms "sunsight" and "sunclipse" to better represent the heliocentric model, though the terms have not entered into common language. Astronomically, sunrise occurs for only an instant, namely the moment at which the upper limb of

420-429: The summer solstice ; although the exact date varies by latitude. After this point, the time of sunrise gets later each day, reaching its latest shortly after the winter solstice , also varying by latitude. The offset between the dates of the solstice and the earliest or latest sunrise time is caused by the eccentricity of Earth's orbit and the tilt of its axis, and is described by the analemma, which can be used to predict

450-410: The Northern Hemisphere summer, and when − 90 ∘ − δ < ϕ < 90 ∘ + δ {\displaystyle -90^{\circ }-\delta <\phi <90^{\circ }+\delta } during the Northern Hemisphere winter. For locations outside these latitudes, it is either 24-hour daytime or 24-hour nighttime . In

480-742: The Northern Hemisphere winter. The expression above is always applicable for latitudes between the Arctic Circle and Antarctic Circle . North of the Arctic Circle or south of the Antarctic Circle, there is at least one day of the year with no sunrise or sunset. Formally, there is a sunrise or sunset when − 90 ∘ + δ < ϕ < 90 ∘ − δ {\displaystyle -90^{\circ }+\delta <\phi <90^{\circ }-\delta } during

510-579: 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 . The figure on the right is calculated using the solar geometry routine in Ref. as follows: An interesting feature in

540-496: The Sun appears tangent to the horizon. However, the term sunrise commonly refers to periods of time both before and after this point: The stage of sunrise known as false 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

570-455: 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 . The timing of sunrise varies throughout the year and is also affected by the viewer's latitude and longitude , altitude , and time zone . These changes are driven by

600-626: The Sun's declination could be approximated as: where: This is the equation from above with corrections for atmospherical refraction and solar disc diameter. where: For observations on a sea horizon needing an elevation-of-observer correction, add − 1.15 ∘ elevation in feet / 60 {\displaystyle -1.15^{\circ }{\sqrt {\text{elevation in feet}}}/60} , or − 2.076 ∘ elevation in metres / 60 {\displaystyle -2.076^{\circ }{\sqrt {\text{elevation in metres}}}/60} to

630-416: The beam. At sunrise and sunset, when the path through the atmosphere is longer, the blue and green components are removed almost completely, leaving the longer-wavelength orange and red hues seen at those times. The remaining reddened sunlight can then be scattered by cloud droplets and other relatively large particles to light up the horizon red and orange. The removal of the shorter wavelengths of light

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660-440: The dates. Variations in atmospheric refraction can alter the time of sunrise by changing its apparent position. Near the poles, the time-of-day variation is extreme, since the Sun crosses the horizon at a very shallow angle and thus rises more slowly. 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

690-410: The equation given at the beginning, the cosine function on the left side gives results in the range [-1, 1], but the value of the expression on the right side is in the range [ − ∞ , ∞ ] {\displaystyle [-\infty ,\infty ]} . An applicable expression for ω ∘ {\displaystyle \omega _{\circ }} in

720-411: The expression ω ∘ / 15 ∘ {\displaystyle \omega _{\circ }/\mathrm {15} ^{\circ }} , where ω ∘ {\displaystyle \omega _{\circ }} is in degree, gives the interval of time in hours from sunrise to local solar noon or from local solar noon to sunset . The sign convention

750-403: The figure on the right is apparent hemispheric symmetry in regions where daily sunrise and sunset actually occur. This symmetry becomes clear if the hemispheric relation in to the sunrise equation is applied to the x- and y-components of the solar vector presented in Ref. Air molecules and airborne particles scatter white sunlight as it passes through the Earth's atmosphere. This is done by

780-399: The format of Fortran 90 is as follows: omegao = acos(max(min(-tan(delta*rpd)*tan(phi*rpd), 1.0), -1.0))*dpr where omegao is ω ∘ {\displaystyle \omega _{\circ }} in degree, delta is δ {\displaystyle \delta } in degree, phi is ϕ {\displaystyle \phi } in degree, rpd

810-413: The global average of length of daytime on any given day is 12 hours without considering the effect of atmospheric refraction. The equation above neglects the influence of atmospheric refraction (which lifts the solar disc — i.e. makes the solar disc appear higher in the sky — by approximately 0.6° when it is on the horizon) and the non-zero angle subtended by the solar disc — i.e. the apparent diameter of

840-403: The light scattered by clouds, and also for the daytime halo of white light around the Sun ( forward scattering of white light). Sunset colors are typically more brilliant than sunrise colors, because the evening air contains more particles than morning air. Ash from volcanic eruptions , trapped within the troposphere , tends to mute sunset and sunrise colors, while volcanic ejecta that

870-510: The sun — (about 0.5°). The times of the rising and the setting of the upper solar limb as given in astronomical almanacs correct for this by using the more general equation with the altitude angle (a) of the center of the solar disc set to about −0.83° (or −50 arcminutes). The above general equation can be also used for any other solar altitude. The NOAA provides additional approximate expressions for refraction corrections at these other altitudes. There are also alternative formulations, such as

900-490: The world. The high altitude clouds serve to reflect strongly reddened sunlight still striking the stratosphere after sunset, down to the surface. Sunrise equation The sunrise equation or sunset equation can be used to derive the time of sunrise or sunset for any solar declination and latitude in terms of local solar time when sunrise and sunset actually occur. It is formulated as: where: The Earth rotates at an angular velocity of 15°/hour. Therefore,

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