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Twilight
Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this illumination occurs. The lower the Sun is beneath the horizon, the dimmer the twilight (other factors such as atmospheric conditions being equal). When the Sun reaches 18° below the horizon, the twilight's brightness is nearly zero, and evening twilight becomes nighttime. When the Sun again reaches 18° below the horizon, nighttime becomes morning twilight. Owing to its distinctive quality, primarily the absence of shadows and the appearance of objects silhouetted against the lit sky, twilight has long been popular with photographers and painters, who often refer to it as the blue hour, after the French expression ''l'heure bleue''. By analogy with evening twilight, the word ''twilight'' is also sometimes used metaphorically, to imply tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Twilight Description Full Day
Twilight is diffuse sky radiation, light produced by sunlight scattering in the upper Earth's atmosphere, atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this illumination occurs. The lower the Sun is beneath the horizon, the dimmer the twilight (other factors such as atmospheric conditions being equal). When the Sun reaches 18° below the horizon, the twilight's brightness is nearly zero, and evening twilight becomes nighttime. When the Sun again reaches 18° below the horizon, nighttime becomes morning twilight. Owing to its distinctive quality, primarily the absence of shadows and the appearance of objects silhouetted against the lit sky, twilight has long been popular with photographers and painters, who often refer to it as the blue hour, after the French language, French expression ''l'heure bleue''. By analogy with evening twilight, the word ''twil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Twilight Toronto Across Lake Ontario51km With Ship5-10km
Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this illumination occurs. The lower the Sun is beneath the horizon, the dimmer the twilight (other factors such as atmospheric conditions being equal). When the Sun reaches 18° below the horizon, the twilight's brightness is nearly zero, and evening twilight becomes nighttime. When the Sun again reaches 18° below the horizon, nighttime becomes morning twilight. Owing to its distinctive quality, primarily the absence of shadows and the appearance of objects silhouetted against the lit sky, twilight has long been popular with photographers and painters, who often refer to it as the blue hour, after the French expression ''l'heure bleue''. By analogy with evening twilight, the word ''twilight'' is also sometimes used metaphorically, to imply tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Twilight In Landers
Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this illumination occurs. The lower the Sun is beneath the horizon, the dimmer the twilight (other factors such as atmospheric conditions being equal). When the Sun reaches 18° below the horizon, the twilight's brightness is nearly zero, and evening twilight becomes nighttime. When the Sun again reaches 18° below the horizon, nighttime becomes morning twilight. Owing to its distinctive quality, primarily the absence of shadows and the appearance of objects silhouetted against the lit sky, twilight has long been popular with photographers and painters, who often refer to it as the blue hour, after the French expression ''l'heure bleue''. By analogy with evening twilight, the word ''twilight'' is also sometimes used metaphorically, to imply that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Twilight Subcategories
Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this illumination occurs. The lower the Sun is beneath the horizon, the dimmer the twilight (other factors such as atmospheric conditions being equal). When the Sun reaches 18° below the horizon, the twilight's brightness is nearly zero, and evening twilight becomes nighttime. When the Sun again reaches 18° below the horizon, nighttime becomes morning twilight. Owing to its distinctive quality, primarily the absence of shadows and the appearance of objects silhouetted against the lit sky, twilight has long been popular with photographers and painters, who often refer to it as the blue hour, after the French expression ''l'heure bleue''. By analogy with evening twilight, the word ''twilight'' is also sometimes used metaphorically, to imply that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dusk
Dusk occurs at the darkest stage of twilight, or at the very end of astronomical twilight after sunset and just before nightfall.''The Random House College Dictionary'', "dusk". At predusk, during early to intermediate stages of twilight, enough light in the sky under clear conditions may occur to read outdoors without artificial illumination; however, at the end of civil twilight (when Earth rotates to a point at which the center of the Sun's disk is 6° below the local horizon), such lighting is required to read outside. The term ''dusk'' usually refers to astronomical dusk, or the darkest part of twilight before night begins. Technical definitions The time of dusk is the moment at the very end of astronomical twilight, just before the minimum brightness of the night sky sets in, or may be thought of as ''the darkest part of evening twilight''. However, technically, the three stages of dusk are as follows: *At civil dusk, the center of the Sun's disc goes 6° below the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blue Hour
The blue hour (from French ; ) is the period of twilight (in the morning or evening, around the nautical stage) when the Sun is at a significant depth below the horizon. During this time, the remaining sunlight takes on a mostly blue shade. This shade differs from the colour of the sky on a clear day, which is caused by Rayleigh scattering. The blue hour occurs when the Sun is far enough below the horizon so that the sunlight's blue wavelengths dominate due to the Chappuis absorption caused by ozone. Since the term is colloquial, it lacks an official definition such as dawn, dusk, or the three stages of twilight. Rather, blue hour refers to the state of natural lighting that usually occurs around the nautical stage of the twilight period (at dawn or dusk). Explanation and times of occurrence The still commonly presented incorrect explanation claims that Earth's post-sunset and pre-sunrise atmosphere solely receives and disperses the sun's shorter blue wavelengths and scatter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sunset
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 until ... [...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] |
Lighting-up Time
In the United Kingdom, lighting-up time is a legally-enforced period from half an hour after sunset to half an hour before sunrise, during which all motor vehicles on unlit public roads (except if parked) must use their headlights. History Lighting-up time was first introduced in the nineteenth century in local by-laws and enforced nationally by the Lights on Vehicles Act 1907. In the 1920s, service stations started displaying cardboard clock-face displays, set to the lighting-up time for the day. The Road Lighting Act 1942 stipulated 1 hour after sunset/before sunrise. It was amended to 30 minutes by the Road Traffic Act 1956 because of the increasing speed of traffic. These were the required times for showing all lights on all vehicles, including bicycles and horse-drawn carts, hence the name ''lighting-up time''. The current Road Vehicles Lighting Regulations 1989 tightened the requirements further. Lighting-up time is retained as the required period for use of mot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Night
Night (also described as night time, unconventionally spelled as "nite") is the period of ambient darkness from sunset to sunrise during each 24-hour day, when the Sun is below the horizon. The exact time when night begins and ends depends on the location and varies throughout the year, based on factors such as season and latitude. The word can be used in a different sense as the time between bedtime and morning. In common communication, the word ''night'' is used as a farewell ("good night", sometimes shortened to "night"), mainly when someone is going to sleep or leaving. Astronomical night is the period between astronomical dusk and astronomical dawn when the Sun is between 18 and 90 degrees below the horizon and does not illuminate the sky. As seen from latitudes between about 48.56° and 65.73° north or south of the Equator, complete darkness does not occur around the summer solstice because, although the Sun sets, it is never more than 18° below the horizon at lowe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffuse Sky Radiation
Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere. It is also called sky radiation, the determinative process for changing the colors of the sky. Approximately 23% of direct incident radiation of total sunlight is removed from the direct solar beam by scattering into the atmosphere; of this amount (of incident radiation) about two-thirds ultimately reaches the earth as photon diffused skylight radiation. The dominant radiative scattering processes in the atmosphere are Rayleigh scattering and Mie scattering; they are elastic, meaning that a photon of light can be deviated from its path without being absorbed and without changing wavelength. Under an overcast sky, there is no direct sunlight, and all light results from diffused skylight radiation. Proceeding from analyses of the aftermath of the eruption of the Philippines volcano Mount Pinatubo (in Ju ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horizon
The horizon is the apparent line that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This line divides all viewing directions based on whether it intersects the relevant body's surface or not. The ''true horizon'' is a theoretical line, which can only be observed to any degree of accuracy when it lies along a relatively smooth surface such as that of Earth's oceans. At many locations, this line is obscured by terrain, and on Earth it can also be obscured by life forms such as trees and/or human constructs such as buildings. The resulting intersection of such obstructions with the sky is called the ''visible horizon''. On Earth, when looking at a sea from a shore, the part of the sea closest to the horizon is called the offing. Pronounced, "Hor-I-zon". The true horizon surrounds the observer and it is typically assumed to be a circle, drawn on the surface of a perfectly spherica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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