|
Sunsets
Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the spring and autumn equinoxes. As viewed from the Northern Hemisphere, the Sun sets to the northwest (or not at all) in the spring and summer, and to the southwest in the autumn and winter; these seasons are reversed for the Southern Hemisphere. The time of sunset is defined in astronomy as the moment when 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 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 u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sunset Tokyoarea-timelapse-2019-03-17
Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the spring and autumn equinoxes. As viewed from the Northern Hemisphere, the Sun sets to the northwest (or not at all) in the spring and summer, and to the southwest in the autumn and winter; these seasons are reversed for the Southern Hemisphere. The time of sunset is defined in astronomy as the moment when 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 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 unti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time Zone
A time zone is an area which observes a uniform standard time for legal, Commerce, commercial and social purposes. Time zones tend to follow the boundaries between Country, countries and their Administrative division, subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time. All time zones are defined as offsets from Coordinated Universal Time (UTC), ranging from UTC−12:00 to UTC+14:00. The UTC offset, offsets are usually a whole number of hours, but a few zones are offset by an additional 30 or 45 minutes, such as in Indian Standard Time, India, Time in Australia, South Australia and Nepal Time, Nepal. Some areas of higher latitude use daylight saving time for about half of the year, typically by adding one hour to local time during spring (season), spring and summer. List of UTC offsets In the table below, the locations that use daylight saving time (DST) are listed in their UTC offse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Analemma
In astronomy, an analemma (; ) is a diagram showing the position of the Sun in the sky as seen from a fixed location on Earth at the same mean solar time, as that position varies over the course of a year. The diagram will resemble a figure eight. Globes of Earth often display an analemma as a two-dimensional figure of equation of time vs. declination of the Sun. The north–south component of the analemma results from the change in the Sun's declination due to the tilt of Earth's axis of rotation. The east–west component results from the nonuniform rate of change of the Sun's right ascension, governed by combined effects of Earth's axial tilt and orbital eccentricity. One can photograph an analemma by keeping a camera at a fixed location and orientation and taking multiple exposures throughout the year, always at the same time of day (disregarding daylight saving time, if applicable). Diagrams of analemmas frequently carry marks that show the position of the Sun at variou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctic Circle
The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of Earth. The region south of this circle is known as the Antarctic, and the zone immediately to the north is called the Southern Temperate Zone. South of the Antarctic Circle, the Sun is above the horizon for 24 continuous hours at least once per year (and therefore visible at midnight) and the centre of the Sun (ignoring refraction) is below the horizon for 24 continuous hours at least once per year (and therefore not visible at noon); this is also true within the equivalent polar circle in the Northern Hemisphere, the Arctic Circle. The position of the Antarctic Circle is not fixed and currently runs south of the Equator. This figure may be slightly inaccurate because it does not allow for the effects of astronomical nutation, which can be up to 10″. Its latitude depends on the Earth's axial tilt, which fluctuates within a margin of more than 2° over a 41,000-year period, due ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sunrise
Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the solar disk crossing the horizon and its accompanying atmospheric effects. Terminology 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 is so convincing that many cultures had mythologies and religions built around 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: the moment at which the upper limb of the Sun appears tangent to the horizon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Latitude And Longitude
The geographic coordinate system (GCS) is a spherical or ellipsoidal coordinate system for measuring and communicating positions directly on the Earth as latitude and longitude. It is the simplest, oldest and most widely used of the various spatial reference systems that are in use, and forms the basis for most others. Although latitude and longitude form a coordinate tuple like a cartesian coordinate system, the geographic coordinate system is not cartesian because the measurements are angles and are not on a planar surface. A full GCS specification, such as those listed in the EPSG and ISO 19111 standards, also includes a choice of geodetic datum (including an Earth ellipsoid), as different datums will yield different latitude and longitude values for the same location. History The invention of a geographic coordinate system is generally credited to Eratosthenes of Cyrene, who composed his now-lost ''Geography'' at the Library of Alexandria in the 3rd century BC. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Noon
Noon (or midday) is 12 o'clock in the daytime. It is written as 12 noon, 12:00 m. (for meridiem, literally 12:00 noon), 12 p.m. (for post meridiem, literally "after noon"), 12 pm, or 12:00 (using a 24-hour clock) or 1200 (military time). Solar noon is the time when the Sun appears to contact the local celestial meridian. This is when the Sun reaches its apparent highest point in the sky, at 12 noon apparent solar time and can be observed using a sundial. The local or clock time of solar noon depends on the longitude and date, with Daylight Savings Time tending to place solar noon closer to 1:00pm. Etymology The word ''noon'' is derived from Latin ''nona hora'', the ninth canonical hour of the day, in reference to the Western Christian liturgical term none, one of the seven fixed prayer times in traditional Christian denominations. The Roman and Western European medieval monastic day began at 6:00 a.m. (06:00) at the equinox by modern timekeeping, so the ninth hour star ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Azimuth
An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematically, the relative position vector from an observer (origin) to a point of interest is projected perpendicularly onto a reference plane (the horizontal plane); the angle between the projected vector and a reference vector on the reference plane is called the azimuth. When used as a celestial coordinate, the azimuth is the horizontal direction of a star or other astronomical object in the sky. The star is the point of interest, the reference plane is the local area (e.g. a circular area with a 5 km radius at sea level) around an observer on Earth's surface, and the reference vector points to true north. The azimuth is the angle between the north vector and the star's vector on the horizontal plane. Azimuth is usually measured in d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
September Equinox
The September equinox (or southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward. Because of differences between the calendar year and the tropical year, the September equinox may occur anytime from September 21 to 24. At the equinox, the Sun as viewed from the equator rises due east and sets due west. Before the Southward equinox, the Sun rises and sets more northerly, and afterwards, it rises and sets more southerly. The equinox may be taken to mark the end of astronomical summer and the beginning of astronomical autumn (autumnal equinox) in the Northern Hemisphere, while marking the end of astronomical winter and the start of astronomical spring (vernal equinox) in the Southern Hemisphere. Occurrences The September equinox is one point in time commonly used to determine the length of the tropical year. The dates and times of the September equinoxes that occur from the year 2017 to 2027 (UTC) are listed as follows: C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
March Equinox
The March equinox or northward equinox is the equinox on the Earth when the subsolar point appears to leave the Southern Hemisphere and cross the celestial equator, heading northward as seen from Earth. The March equinox is known as the vernal equinox (spring equinox) in the Northern Hemisphere and as the autumnal equinox in the Southern Hemisphere. On the Gregorian calendar, the northward equinox can occur as early as 19 March or as late as 21 March at 0° longitude. For a common year the computed time slippage is about 5 hours 49 minutes ''later'' than the previous year, and for a leap year about 18 hours 11 minutes ''earlier'' than the previous year. Balancing the increases of the common years against the losses of the leap years keeps the calendar date of the March equinox from drifting more than one day from 20 March each year. The March equinox may be taken to mark the beginning of astronomical spring and the end of astronomical winter in the Northern Hemisphere but m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
