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67-457: Manhattanhenge , also called the Manhattan Solstice , is an event during which the setting sun or the rising sun is aligned with the east–west streets of the main street grid of Manhattan , New York City . The astrophysicist Neil deGrasse Tyson claims to have coined the term, by analogy with Stonehenge . The sunsets and sunrises each align twice a year, on dates evenly spaced around

134-448: A couple of days after the first such date of the year, and a couple of days before the second date, when a pedestrian looking down the center line of the street westward toward New Jersey can see the full solar disk slightly above the horizon and in between the profiles of the buildings. The date shifts are due to the sunset time being when the last of the sun just disappears below the horizon. The precise dates of Manhattanhenge depend on

201-541: A few days around the equinox when the Sun goes directly behind the satellite relative to Earth (i.e. within the beam-width of the ground-station antenna) for a short period each day. The Sun's immense power and broad radiation spectrum overload the Earth station's reception circuits with noise and, depending on antenna size and other factors, temporarily disrupt or degrade the circuit. The duration of those effects varies but can range from

268-400: A few days towards the winter side of each equinox. One result of this is that, at latitudes below ±2.0 degrees, all the days of the year are longer than the nights. The times of sunset and sunrise vary with the observer's location ( longitude and latitude ), so the dates when day and night are equal also depend upon the observer's location. A third correction for the visual observation of

335-403: A few minutes to an hour. (For a given frequency band, a larger antenna has a narrower beam-width and hence experiences shorter duration "Sun outage" windows.) Satellites in geostationary orbit also experience difficulties maintaining power during the equinox because they have to travel through Earth's shadow and rely only on battery power. Usually, a satellite travels either north or south of

402-538: A kid at age 15 on an expedition that [Hawkins] was the expedition head... and that stuck with me, which is why I named this phenomenon in Manhattan where the sun sets along the street grid... I named that Manhattanhenge, sort of harkening back to my early days thinking about the alignment of the sun and structures that we might build." In accordance with the Commissioners' Plan of 1811 , the street grid for most of Manhattan

469-437: A mountain peak turning gold in the sunlight long before the lower slopes are illuminated. The date on which the day and night are exactly the same is known as an equilux ; the neologism , believed to have been coined in the 1980s, achieved more widespread recognition in the 21st century. At the most precise measurements, a true equilux is rare, because the lengths of day and night change more rapidly than any other time of

536-478: A native New Yorker in 1997 in the magazine Natural History . In a later interview, Tyson stated that he coined the term, and that it was inspired by a childhood visit to Stonehenge on an expedition headed by Gerald Hawkins , an astronomer who was the first to propose Stonehenge's purpose as an ancient astronomical observatory used to predict movements of sun and stars, as outlined in his 1965 book Stonehenge Decoded . According to Tyson, "I visited Stonehenge as

603-486: A phenomenon dubbed Chicagohenge . In Toronto , the setting sun lines up with the east–west streets on February 16 and October 25, a phenomenon now known locally as Torontohenge . In Montreal , there is a Montrealhenge each year around June 12. When the architects designing the city centre of Milton Keynes , in the United Kingdom, discovered that its main street almost framed the rising sun on Midsummer Day and

670-416: A sunrise (or sunset) is the angle between the apparent horizon as seen by an observer and the geometric (or sensible) horizon. This is known as the dip of the horizon and varies from 3 arcminutes for a viewer standing on the sea shore to 160 arcminutes for a mountaineer on Everest. The effect of a larger dip on taller objects (reaching over 2½° of arc on Everest) accounts for the phenomenon of snow on

737-399: A year to form Scrippshenge . Sunset The time of actual sunset is defined in astronomy as two minutes before the upper limb of the Sun disappears below the horizon. Near the horizon, atmospheric refraction causes sunlight rays to be distorted to such an extent that geometrically the solar disk is already about one diameter below the horizon when a sunset is observed. Sunset

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804-600: A “Crack of light” between two very close buildings on the Summer Solstice at 1698 Sanchez Street every year. Variously over the years there has been a white or yellow line painted on the sidewalk to mark the place where the light shines through the crack on the Solstice. In San Diego , the sunset can be seen underneath the Ellen Browning Scripps Memorial Pier at Scripps Institution of Oceanography twice

871-462: Is astronomical twilight , which is the period when the Sun is between 12 and 18 degrees below the horizon. Dusk is at the very end of astronomical twilight, and is the darkest moment of twilight just before night . Finally, night occurs when the Sun reaches 18 degrees below the horizon and no longer illuminates the sky. Locations further north than the Arctic Circle and further south than

938-460: Is 50 arcminutes below the geometric horizon, which is the intersection with the celestial sphere of a horizontal plane through the eye of the observer. These effects make the day about 14 minutes longer than the night at the equator and longer still towards the poles. The real equality of day and night only happens in places far enough from the equator to have a seasonal difference in day length of at least 7 minutes, actually occurring

1005-479: Is a moment in time when the Sun crosses the Earth's equator , which is to say, appears directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" and set "due west". This occurs twice each year, around 20 March and 23 September . More precisely, an equinox is traditionally defined as the time when the plane of Earth 's equator passes through

1072-518: Is a reference to Stonehenge , a prehistoric monument located in Wiltshire , England, which was constructed so that the rising sun , seen from the center of the monument at the time of the summer solstice , aligns with the outer " Heel Stone ". The phenomenon (but not the term "Manhattanhenge") was described by Neil deGrasse Tyson , an astrophysicist at the American Museum of Natural History and

1139-481: Is applied to the x- and y-components of the solar vector presented in Ref. 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

1206-410: Is derived from the morpheme "ws" – meaning "up", and "chód" – signifying "move" (from the verb chodzić – meaning "walk, move"), due to the act of the Sun coming up from behind the horizon. The Polish word for west , zachód ( zakhud ), is similar but with the word "za" at the start, meaning "behind", from the act of the Sun going behind the horizon. In Russian , the word for west, запад ( zapad ),

1273-407: Is derived from the words за – meaning "behind", and пад – signifying "fall" (from the verb падать – padat' ), due to the act of the Sun falling behind the horizon. In Hebrew, the word for east is 'מזרח', which derives from the word for rising, and the word for west is 'מערב', which derives from the word for setting. The 16th-century astronomer Nicolaus Copernicus was the first to present to

1340-401: Is distinct from twilight , which is divided into three stages. The first one is civil twilight , which begins once the Sun has disappeared below the horizon, and continues until it descends to 6 degrees below the horizon. The early to intermediate stages of twilight coincide with predusk . The second phase is nautical twilight , between 6 and 12 degrees below the horizon. The third phase

1407-442: 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 (> 600 nm) is due to Mie scattering and is not strongly wavelength-dependent. Mie scattering is responsible for the light scattered by clouds, and also for

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1474-408: 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 stratus clouds containing sulfuric acid to yield remarkable sunset afterglows (and pre-sunrise glows) around

1541-524: Is rotated 29° clockwise from true east-west. Thus, when the azimuth for sunset is 299° (i.e., 29° north of due West), the sunset aligns with the streets on that grid. This rectilinear grid design runs from north of Houston Street in Lower Manhattan to south of 155th Street (Manhattan) in Upper Manhattan. A more impressive visual spectacle, and the one commonly referred to as Manhattanhenge, occurs

1608-491: The Antarctic Circle experience no full sunset or sunrise on at least one day of the year, when the polar day or the polar night persists continuously for 24 hours. At latitudes greater than within half a degree of either pole, the sun cannot rise or set on the same date on any day of the year, since the sun's angular elevation between solar noon and midnight is less than one degree. The time of sunset varies throughout

1675-542: The March equinox , indicating that at that moment the solar declination is crossing the celestial equator in a northward direction, and southward equinox for the September equinox , indicating that at that moment the solar declination is crossing the celestial equator in a southward direction. Daytime is increasing at the fastest at the vernal equinox and decreasing at the fastest at the autumnal equinox. Systematically observing

1742-677: The Strasbourghenge occurs in October where the rising sun seen from the A351 motorway lines up with the spire of the cathedral. In San Francisco , the sunrise lines up and falls perfectly above the San Francisco–Bay Bridge between California and Gough Street in San Francisco , twice a year (Spring and Fall). This has been called "California Henge" at times. Also in San Francisco there is

1809-519: The atmospheric refraction is assumed to be 34 arcminutes, and the assumed semidiameter (apparent radius ) of the Sun is 16  arcminutes . (The apparent radius varies slightly depending on time of year, slightly larger at perihelion in January than aphelion in July , but the difference is comparatively small.) Their combination means that when the upper limb of the Sun is on the visible horizon, its centre

1876-497: The date of Easter , which means he wanted to move the vernal equinox to the date on which it fell at that time (21 March is the day allocated to it in the Easter table of the Julian calendar), and to maintain it at around that date in the future, which he achieved by reducing the number of leap years from 100 to 97 every 400 years. However, there remained a small residual variation in

1943-525: The summer solstice and winter solstice . The sunset alignments occur around May 28 and July 13. The sunrise alignments occur around December 5 and January 8. Manhattan has a phenomenon of this kind due to its extensive urban canyons and its rectilinear street grid that is rotated 29° clockwise from true east–west. Many streets align with the view of the Manhattanhenge including 14th , 23rd , 34th , 42nd , and 57th Streets. The term Manhattanhenge

2010-435: The sunrise , people discovered that it occurs between two extreme locations at the horizon and eventually noted the midpoint between the two. Later it was realized that this happens on a day when the duration of the day and the night are practically equal and the word "equinox" comes from Latin aequus , meaning "equal", and nox , meaning "night". In the northern hemisphere, the vernal equinox (March) conventionally marks

2077-474: The Earth's shadow because Earth's axis is not directly perpendicular to a line from the Earth to the Sun at other times. During the equinox, since geostationary satellites are situated above the Equator, they are in Earth's shadow for the longest duration all year. Equinoxes are defined on any planet with a tilted rotational axis. A dramatic example is Saturn, where the equinox places its ring system edge-on facing

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2144-521: The North Pole is 18 March 07:09 UTC, and sunset on the South Pole is 22 March 13:08 UTC. Also in 2021, sunrise on the South Pole is 20 September 16:08 UTC, and sunset on the North Pole is 24 September 22:30 UTC. In other words, the equinoxes are the only times when the subsolar point is on the equator, meaning that the Sun is exactly overhead at a point on the equatorial line. The subsolar point crosses

2211-548: The Sun's non-zero size, whenever and wherever sunset occurs, it is always in the northwest quadrant from the March equinox to the September equinox , and in the southwest quadrant from the September equinox to the March equinox. Sunsets occur almost exactly due west on the equinoxes for all viewers on Earth. Exact calculations of the azimuths of sunset on other dates are complex, but they can be estimated with reasonable accuracy by using

2278-421: The Sun, atmospheric refraction , and the rapidly changing duration of the length of day that occurs at most latitudes around the equinoxes. Long before conceiving this equality, equatorial cultures noted the day when the Sun rises due east and sets due west , and indeed this happens on the day closest to the astronomically defined event. As a consequence, according to a properly constructed and aligned sundial ,

2345-450: The Sun. As a result, they are visible only as a thin line when seen from Earth. When seen from above – a view seen during an equinox for the first time from the Cassini space probe in 2009 – they receive very little sunshine ; indeed, they receive more planetshine than light from the Sun. This phenomenon occurs once every 14.7 years on average, and can last a few weeks before and after

2412-403: The Sun. It is only after a complete Gregorian leap-year cycle of 400 years that the seasons commence at approximately the same time. In the 21st century the earliest March equinox will be 19 March 2096, while the latest was 21 March 2003. The earliest September equinox will be 21 September 2096 while the latest was 23 September 2003 ( Universal Time ). On the date of

2479-409: The air is full of red dust , blown into the atmosphere by high winds, so its sky color is mainly determined by a Mie Scattering process, resulting in more blue hues than an Earth sunset. One study also reported that Martian dust high in the atmosphere can reflect sunlight up to two hours after the Sun has set, casting a diffuse glow across the surface of Mars. Equinox A solar equinox

2546-409: The analemma. As sunrise and sunset are calculated from the leading and trailing edges of the Sun, respectively, and not the center, the duration of a daytime is slightly longer than nighttime (by about 10 minutes, as seen from temperate latitudes). Further, because the light from the Sun is refracted as it passes through the Earth's atmosphere, the Sun is still visible after it is geometrically below

2613-585: The apparent height of the solar disk. Its width is unaltered, so the disk appears wider than it is high. (In reality, the Sun is almost exactly spherical.) The Sun also appears larger on the horizon, an optical illusion, similar to the moon illusion . Locations within the Arctic and Antarctic Circles experience periods where the Sun does not rise or set for 24 hours or more, known as polar day and polar night . These phenomena occur due to Earth’s axial tilt , causing continuous sunlight or darkness at certain times of

2680-415: 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 we see 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

2747-595: The beginning of spring in most cultures and is considered the start of the New Year in the Assyrian calendar , Hindu, and the Persian or Iranian calendars , while the autumnal equinox (September) marks the beginning of autumn. Ancient Greek calendars too had the beginning of the year either at the autumnal or vernal equinox and some at solstices. The Antikythera mechanism predicts the equinoxes and solstices. The equinoxes are

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2814-448: The calendar "drifted" with respect to the two equinoxes – so that in 300 AD the spring equinox occurred on about 21 March, and by the 1580s AD it had drifted backwards to 11 March. This drift induced Pope Gregory XIII to establish the modern Gregorian calendar . The Pope wanted to continue to conform with the edicts of the Council of Nicaea in 325 AD concerning

2881-436: The compass bear names etymologically derived from words for sunrise and sunset. The English words " orient " and " occident ", meaning "east" and "west", respectively, are descended from Latin words meaning "sunrise" and "sunset". The word "levant", related e.g. to French " (se) lever " meaning "lift" or "rise" (and also to English "elevate"), is also used to describe the east. In Polish , the word for east wschód ( vskhud ),

2948-457: The date and time of the vernal equinox of about ±27 hours from its mean position, virtually all because the distribution of 24 hour centurial leap-days causes large jumps (see Gregorian calendar leap solstice ). The dates of the equinoxes change progressively during the leap-year cycle, because the Gregorian calendar year is not commensurate with the period of the Earth's revolution about

3015-451: The date of the summer solstice, which varies from year to year, but remains close to June 21. In 2014, the "full sun" Manhattanhenge occurred on May 30 at 8:18 p.m., and on July 11 at 8:24 p.m. The event has attracted increasing attention in recent years. The dates on which sunrise aligns with the streets on the Manhattan grid are evenly spaced around the winter solstice and correspond approximately to December 5 and January 8. In

3082-539: The days get longer and sunsets occur later every day until the day of the latest sunset, which occurs after the summer solstice. In the Northern Hemisphere , the latest sunset occurs late in June or in early July, but not on the summer solstice of June 21. This date depends on the viewer's latitude (connected with the Earth's slower movement around the aphelion around July 4). Likewise, the earliest sunset does not occur on

3149-414: The days of the vernal and autumnal equinoxes (which occur around March 20 and September 23 respectively). In Baltimore , for instance, sunrise aligns on March 25 and September 18 and sunset on March 12 and September 29. In Chicago , where the street grid aligns with the cardinal directions, the setting sun lines up with the street canyons near the spring and autumn equinoxes, March 20 and September 25,

3216-497: The daytime duration is 12 hours. In the Northern Hemisphere , the March equinox is called the vernal or spring equinox while the September equinox is called the autumnal or fall equinox. In the Southern Hemisphere , the reverse is true. During the year, equinoxes alternate with solstices . Leap years and other factors cause the dates of both events to vary slightly. Hemisphere-neutral names are northward equinox for

3283-431: 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. Sometimes just before sunrise or after sunset a green flash can be seen. Ash from volcanic eruptions, trapped within the troposphere , tends to mute sunset and sunrise colors, while volcanic ejecta that

3350-481: The equator moving northward at the March equinox and southward at the September equinox. When Julius Caesar established the Julian calendar in 45 BC, he set 25 March as the date of the spring equinox; this was already the starting day of the year in the Persian and Indian calendars. Because the Julian year is longer than the tropical year by about 11.3 minutes on average (or 1 day in 128 years),

3417-428: The equinox, the center of the Sun spends a roughly equal amount of time above and below the horizon at every location on the Earth, so night and day are about the same length. Sunrise and sunset can be defined in several ways, but a widespread definition is the time that the top limb of the Sun is level with the horizon. With this definition, the day is longer than the night at the equinoxes: In sunrise/sunset tables,

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3484-556: The equinox; the Angkor Wat Equinox during which the sun rises in a perfect alignment over Angkor Wat in Cambodia is one such example. Catholic churches , since the recommendations of Charles Borromeo , have often chosen the equinox as their reference point for the orientation of churches . One effect of equinoctial periods is the temporary disruption of communications satellites . For all geostationary satellites, there are

3551-461: The equinoxes are currently defined to be when the apparent geocentric longitude of the Sun is 0° and 180°. The word is derived from the Latin aequinoctium , from aequus (equal) and nox (night). On the day of an equinox, daytime and nighttime are of approximately equal duration all over the planet. Contrary to popular belief, they are not exactly equal because of the angular size of

3618-466: The equinoxes. The equinoxes are sometimes regarded as the start of spring and autumn. A number of traditional harvest festivals are celebrated on the date of the equinoxes. People in countries including Iran, Afghanistan, Tajikistan celebrate Nowruz which is spring equinox in northern hemisphere. This day marks the new year in Solar Hijri calendar . Religious architecture is often determined by

3685-428: The following table, "full sun" refers to occurrences of the full solar disk just above the horizon, while "half sun" refers to occurrences of the solar disk partially hidden below the horizon. The same phenomenon happens in other cities with a uniform street grid and an unobstructed view of the horizon. If the streets on the grid were rigorously north-south and east–west, then both sunrise and sunset would be aligned on

3752-568: The geometric center of the Sun 's disk. Equivalently, this is the moment when Earth's rotation axis is directly perpendicular to the Sun-Earth line, tilting neither toward nor away from the Sun. In modern times , since the Moon (and to a lesser extent the planets) causes Earth's orbit to vary slightly from a perfect ellipse , the equinox is officially defined by the Sun's more regular ecliptic longitude rather than by its declination . The instants of

3819-400: The horizon. Refraction also affects the apparent shape of the Sun when it is very close to the horizon. It makes things appear higher in the sky than they really are. Light from the bottom edge of the Sun's disk is refracted more than light from the top, since refraction increases as the angle of elevation decreases. This raises the apparent position of the bottom edge more than the top, reducing

3886-412: The latest sunsets occurring some time after December 21 in summer, again depending on one's southern latitude. For a few weeks surrounding both solstices, both sunrise and sunset get slightly later each day. Even on the equator, sunrise and sunset shift several minutes back and forth through the year, along with solar noon. These effects are plotted by an analemma . Neglecting atmospheric refraction and

3953-455: The only times when the solar terminator (the "edge" between night and day) is perpendicular to the equator. As a result, the northern and southern hemispheres are equally illuminated. For the same reason, this is also the time when the Sun rises for an observer at one of Earth's rotational poles and sets at the other. For a brief period lasting approximately four days, both North and South Poles are in daylight. For example, in 2021 sunrise on

4020-497: The setting sun on Midwinter Day , they consulted Greenwich Observatory to obtain the exact angle required at their latitude, and persuaded their engineers to shift the grid of roads a few degrees. In Cambridge, Massachusetts , MIThenge occurs about January 29 and November 11, when the setting sun may be seen across the length of the " Infinite Corridor " at the Massachusetts Institute of Technology . In Strasbourg ,

4087-484: The size it does from Earth , due to the greater distance between Mars and the Sun. The colors are typically hues of blue, but some Martian sunsets last significantly longer and appear far redder than is typical on Earth. The colors of the Martian sunset differ from those on Earth. Mars has a thin atmosphere , lacking oxygen and nitrogen , so the light scattering is not dominated by a Rayleigh Scattering process. Instead,

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4154-517: The winter solstice, but rather about two weeks earlier, again depending on the viewer's latitude. In the Northern Hemisphere, it occurs in early December or late November (influenced by the Earth's faster movement near its perihelion , which occurs around January 3). Likewise, the same phenomenon exists in the Southern Hemisphere , but with the respective dates reversed, with the earliest sunsets occurring some time before June 21 in winter, and

4221-438: The world a detailed and eventually widely accepted mathematical model supporting the premise that the Earth is moving and the Sun actually stays still, despite the impression from our point of view of a moving Sun. Sunsets on other planets appear different because of differences in the distance of the planet from the Sun and non-existent or differing atmospheric compositions. On Mars , the setting Sun appears about two-thirds

4288-442: The world. The high-altitude clouds serve to reflect strongly reddened sunlight still striking the stratosphere after sunset, down to the surface. Some of the most varied colors at sunset can be found in the opposite or eastern sky after the Sun has set during twilight. Depending on weather conditions and the types of clouds present, these colors have a wide spectrum, and can produce unusual results. In some languages, points of

4355-441: The year and is determined by the viewer's position on Earth, specified by latitude and longitude , altitude , and time zone . Small daily changes and noticeable semi-annual changes in the timing of sunsets are driven by the axial tilt of the 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. During winter and spring,

4422-482: The year around the equinoxes. In the mid-latitudes, daylight increases or decreases by about three minutes per day at the equinoxes, and thus adjacent days and nights only reach within one minute of each other. The date of the closest approximation of the equilux varies slightly by latitude; in the mid-latitudes, it occurs a few days before the spring equinox and after the fall equinox in each respective hemisphere. Mirror-image conjugate auroras have been observed during

4489-465: The year. Approximate locations of sunset on the horizon ( azimuth ) as described above can be found in Refs. The figure on the right is calculated using the solar geometry routine as follows: An interesting feature in 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 sunrise equation

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