"or of other shapes. If the shadow falls on a surface that is symmetrical about the celestial axis (as in an armillary sphere, or an equatorial dial), the surface-shadow likewise moves uniformly; the hour-lines on the sundial are equally spaced. However, if the receiving surface is not symmetrical (as in most horizontal sundials), the surface shadow generally moves non-uniformly and the hour-lines are not equally spaced; one exception is the Lambert dial described below. Some types of sundials are designed with a fixed gnomon that is not aligned with the celestial poles like a vertical obelisk. Such sundials are covered"
"inexpensive, mass-produced decorative sundials to have incorrectly aligned gnomons and hour-lines, which cannot be adjusted to tell correct time. There are several different types of sundials. Some sundials use a shadow or the edge of a shadow while others use a line or spot of light to indicate the time. The shadow-casting object, known as a ""gnomon"", may be a long thin rod or other object with a sharp tip or a straight edge. Sundials employ many types of gnomon. The gnomon may be fixed or moved according to the season. It may be oriented vertically, horizontally, aligned with the"
"cast its shadow in the evening direction. A sundial uses a gnomon to cast a shadow on a set of markings calibrated to the hour. The position of the shadow marks the hour in local time. The idea to separate the day into smaller parts is credited to Egyptians because of their sundials, which operated on a duodecimal system. The importance of the number 12 is due the number of lunar cycles in a year and the number of stars used to count the passage of night. The most precise timekeeping device of the ancient world was the water clock,"
"History of sundials A sundial is a device that measures time by using a light spot or shadow cast by the position of the Sun on a reference scale. As the Earth turns on its polar axis, the sun appears to cross the sky from east to west, rising at sun-rise from beneath the horizon to a zenith at mid-day and falling again behind the horizon at sunset. Both the azimuth (direction) and the altitude (height) can be used to create time measuring devices. Sundials have been invented independently in all major cultures and become more accurate and sophisticated as"
"modeled sculpture instead of a direct carving. The sculpture is composed of two bronze semicircles, one set inside and at right angles to the other and a slim bronze rod that extends from one end of the outer semicircle to the other that serves as the gnomon (indicator). The bowstring equatorial sundial derives its name from the appearance of the shadow-casting gnomon, which resembles a bow string. The shadow of the rod projects onto the inner semicircle, which serves as the dial face (or dial plate), to mark the time of day when there is sufficient sunlight to produce shadows."
"of sundials to indicate solstices and equinoxes. Indeed, a gnomon required adjustments from a place to another because of the difference in latitude. In his time, the gnomon was simply a vertical pillar or rod mounted on a horizontal plane. The position of its shadow on the plane indicated the time of day. As it moves through its apparent course, the sun draws a curve with the tip of the projected shadow, which is shortest at noon, when pointing due south. The variation in the tip's position at noon indicates the solar time and the seasons; the shadow is longest"
"to isolate a single ray of light; the former are sometimes called ""aperture dials"". The oldest example is perhaps the antiborean sundial (""antiboreum""), a spherical nodus-based sundial that faces true North; a ray of sunlight enters from the South through a small hole located at the sphere's pole and falls on the hour and date lines inscribed within the sphere, which resemble lines of longitude and latitude, respectively, on a globe. Isaac Newton developed a convenient and inexpensive sundial, in which a small mirror is placed on the sill of a south-facing window. The mirror acts like a nodus, casting"
"light-spot (called ""declination line"") traces out a conic section such as a hyperbola or an ellipse. The collection of hyperbolae was called a ""pelekonon"" (axe) by the Greeks, because it resembles a double-bladed ax, narrow in the center (near the noonline) and flaring out at the ends (early morning and late evening hours). There is a simple verification of hyperbolic declination lines on a sundial: the distance from the origin to the equinox line should be equal to harmonic mean of distances from the origin to summer and winter solstice lines. Nodus-based sundials may use a small hole or mirror"
"Biancani's ""Constructio instrumenti ad horologia solaria"" (ca. 1620) discusses how to make a perfect sundial. They have been commonly used since the 16th century. In general, sundials indicate the time by casting a shadow or throwing light onto a surface known as a ""dial face"" or ""dial plate"". Although usually a flat plane, the dial face may also be the inner or outer surface of a sphere, cylinder, cone, helix, and various other shapes. The time is indicated where a shadow or light falls on the dial face, which is usually inscribed with hour lines. Although usually straight, these hour"
"the earliest surviving one is a limestone sundial that dates back to 1500 BCE, discovered in the Valley of the Kings in 2013. It was found in a housing area of construction workers and its division of daytime into 12 parts was possibly used to measure work hours. Shadow clocks were modified sundials that allowed for greater precision in determining the time of day, and were first used around 1500 BCE. Their major innovation was a modified, more precise gnomon that allowed for the division of night time into 50 parts, with an additional two ""twilight hours"" in the morning"
"and was discovered in the Valley of the Kings in 2013. Sundials have their origin in shadow clocks, which were the first devices used for measuring the parts of a day. Ancient Egyptian obelisks, constructed about 3500, are also among the earliest shadow clocks. Egyptian shadow clocks divided daytime into 12 parts with each part further divided into more precise parts. One type of shadow clock consisted of a long stem with five variable marks and an elevated crossbar which cast a shadow over those marks. It was positioned eastward in the morning, and was turned west at noon. Obelisks"
"sundials it is possible to view the time of day according to the sunlight by inserting a finger at the center of the dial and tilting it approximately 50 ˚ to the north. ‘Meridians’ are one of the names for the bars that cast a shadow on the sundial, an idea that originates from the location of the meridian arc (an imaginary line that stretches across the globe from the North Pole to the South Pole). Meridians are also an extensive network of cross-channels of life energy in the human body. Danny Lavie, the same artist who developed the Solar"
"Earth's shadow Earth's shadow or Earth shadow is the shadow that Earth itself casts onto its atmosphere and into outer space, toward the antisolar point. During twilight (both early dusk and late dawn), the shadow's visible fringe (sometimes called the dark segment or twilight wedge) appears in a clear sky as a dark and diffused band low above the horizon. Earth's shadow cast onto the atmosphere can be viewed during the ""civil"" stage of twilight, assuming the sky is clear and the horizon is relatively unobstructed. The shadow's fringe appears as a dark bluish to purplish band that stretches over"
"Shadow A shadow is a dark area where light from a light source is blocked by an opaque object. It occupies all of the three-dimensional volume behind an object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or a reverse projection of the object blocking the light. A point source of light casts only a simple shadow, called an ""umbra"". For a non-point or ""extended"" source of light, the shadow is divided into the umbra, penumbra and antumbra. The wider the light source, the more blurred the shadow becomes. If two penumbras"
"clock time considered to be ""right"", and sundial time usually ""wrong"", so the Equation of Time became used as it is today. The most commonly observed sundials are those in which the shadow-casting style is fixed in position and aligned with the Earth's rotational axis, being oriented with true North and South, and making an angle with the horizontal equal to the geographical latitude. This axis is aligned with the celestial poles, which is closely, but not perfectly, aligned with the (present) pole star Polaris. For illustration, the celestial axis points vertically at the true North Pole, where it points"
"to east). This is why hours must be drawn in horizontal sundials in that manner, and why modern clocks have their numbers set in the same way, and their hands moving accordingly. For a vertical sundial (such as those placed on the walls of buildings, the dial being ""below"" the post), the movement of the sun is from right to top to left, and, accordingly, the shadow moves from left to down to right, i.e., counterclockwise. This effect is caused by the plane of the dial having been rotated through the plane of the motion of the sun and thus"
"Sundial cannon A sundial cannon, sundial gun, noon cannon or meridian cannon, also noonday gun is a device consisting of a sundial incorporating a cannon with a fuse that is lit by an overhanging lens, concentrating the rays of the sun, and causing the cannon to fire at noon, when properly oriented along a north-south axis. The cannon sizes ranged from large to small depending on the location of their use. The household variety was used in estates to signal the time for the midday meal. Larger sizes were used in European parks to signal noon. The cannons were used"
"way that the shadow cast directly onto the altar on Augustus’s birthday. The sundial was also integrated in the design of the Mausoleum of Augustus in such a way which illustrated that the entire complex was a cosmic representation of the Principate and the destiny of Augustus, along with his peaceful reign and death. In the mid-1980s Schutz and Bandini challenged the erroneous reconstruction. Bandini found several mistakes made by Buchner on interpreting the ancient texts written by Pliny. Pliny referred to a solar meridian, not a sundial. A solar meridian indicates the length of days and nights, therefore reflecting"
"Noon mark The Noon mark is a type of sundial that at its simplest is a vertical line on a south facing wall or a north-south line on a horizontal pavement. When the shadow of a point (or a projected image of the Sun) crosses the line it will be midday. Noon in local standard time is defined as when the sun is overhead, however clocks and watches use mean time which varies from standard time by a few minutes each day. The difference is calculated using the equation of time and this can be shown on the noon mark"
"to the post of Inspector of Weights. His nephew continued the business under the name of Whitehurst & Son. The family business was known for their turret clocks. Sundial construction is based on understanding the geometry of the solar system, and particularly how the sun will cast a shadow onto a flat surface, in this case a horizontal surface. Each day over a yearly cycle the shadow will be different from the day before, and the shadow is specific to the location of the dial, particularly its latitude. The dial is designed to tell local apparent time so the longitude"
"by drawing an analemma, or using a correction table. Noon mark The Noon mark is a type of sundial that at its simplest is a vertical line on a south facing wall or a north-south line on a horizontal pavement. When the shadow of a point (or a projected image of the Sun) crosses the line it will be midday. Noon in local standard time is defined as when the sun is overhead, however clocks and watches use mean time which varies from standard time by a few minutes each day. The difference is calculated using the equation of time"
"to the light source, the apparent size of the occluding body increases until it causes a full umbra. Umbra, penumbra and antumbra The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a point source only the umbra is cast. These names are most often used for the shadows cast by celestial bodies, though they are sometimes used to describe levels of darkness, such as in sunspots. The umbra (Latin for ""shadow"") is the innermost and darkest part of a shadow, where the"
"Earth's axis, or oriented in an altogether different direction determined by mathematics. Given that sundials use light to indicate time, a line of light may be formed by allowing the sun's rays through a thin slit or focusing them through a cylindrical lens. A spot of light may be formed by allowing the sun's rays to pass through a small hole or by reflecting them from a small circular mirror. Sundials also may use many types of surfaces to receive the light or shadow. Planes are the most common surface, but partial spheres, cylinders, cones and other shapes have been"
"shelf, bench, or altar, and a rectangular base. Possibly used as a sundial, it was aligned with the sun's position during the winter solstice. The Inca believed the stone held the sun in its place along its annual path in the sky. At midday on the equinoxes the sun stands almost above the pillar, casting no shadow at all. On June 21, the stone is casting the longest shadow on its southern side and on December 21, a much shorter one on its northern side. The base is said to be ""in the shape of a map of the Inca"
"sundial. Clocks with hands were first built in the Northern Hemisphere (see ""Clock""), and they were made to work like horizontal sundials. In order for such a sundial to work north of the equator during spring and summer, and north of the Tropic of Cancer the whole year, the noon-mark of the dial must be placed northward of the pole casting the shadow. Then, when the Sun moves in the sky (from east to south to west), the shadow, which is cast on the sundial in the opposite direction, moves with the same sense of rotation (from west to north"
"be used to measure the sun's elevation and, thence, the time. The Venerable Bede gave a table for estimating the time from the length of one's shadow in feet, on the assumption that a monk's height is six times the length of his foot. Such shadow lengths will vary with the geographical latitude and with the time of year. For example, the shadow length at noon is short in summer months, and long in winter months. Chaucer evokes this method a few times in his ""Canterbury Tales"", as in his ""Parson's Tale"". An equivalent type of sundial using a vertical"
"shadows cast by objects. For example, in molybdomancy, a random shape produced by pouring molten tin into cold water is interpreted by the shadow it casts in candlelight. A shadow person (also known as a shadow figure, shadow being or black mass) is often attributed to pareidolia. It is the perception of a patch of shadow as a living, humanoid figure, particularly as interpreted by believers in the paranormal or supernatural as the presence of a spirit or other entity. Pareidolia is also what some skeptics believe causes people to believe that they have seen ghosts. Pareidolia Pareidolia ( )"
"geometric construction. In the world of sundials some of the technical terms use an old form of language, so the angle to which the style is set is called the style height. The style height is identical to the geographical latitude, and in London this was 51 degrees 30 minutes or 51.50 degrees, which roughly corresponds with Westminster Bridge. The gnomon has thickness, and thus two shadow throwing edges (the styles) one for the morning and one for the afternoon, there is a gap left on the dialplate the width of the gnomon. A sundial displays the local apparent time,"
"listed all the known types of dials in Book IX of his ""De Architectura"", together with their Greek inventors. All of these are believed to be nodus-type sundials, differing mainly in the surface that receives the shadow of the nodus. The Romans built a very large sundial in 10 BC, the Solarium Augusti, which is a classic nodus-based obelisk casting a shadow on a planar ""pelekinon"". The Globe of Matelica is felt to have been part of an Ancient Roman sundial from the first or second century. The custom of measuring time by one's shadow has persisted since ancient times."
"earlier date, but this is hard to verify. In roughly 700 BC, the Old Testament describes a sundial — the ""dial of Ahaz"" mentioned in and . The Roman writer Vitruvius lists dials and shadow clocks known at that time. A canonical sundial is one that indicates the canonical hours of liturgical acts. Such sundials were used from the 7th to the 14th centuries by the members of religious communities. Italian astronomer Giovanni Padovani published a treatise on the sundial in 1570, in which he included instructions for the manufacture and laying out of mural (vertical) and horizontal sundials. Giuseppe"
"light vertical shadow. Graded shadows are possible by using moldings in different shapes: the concave ""cavetto"" molding produces a horizontal shadow that is darker at the top and lighter at the bottom; an ""ovolo"" (convex) molding makes a shadow that is lighter at the top and darker at the bottom. Other varieties of concave molding are the ""scotia"" and ""congé"" and other convex moldings the ""echinus"", the ""torus"" and the astragal. Placing an ovolo directly above a cavetto forms a smooth ""s""-shaped curve with vertical ends that is called an ""ogee"" or ""cyma reversa"" molding. Its shadow appears as a"
"edge is the style which throws the shadow after noon. The dial plate is not made up of one complete circle, but two semicircles separated by the thickness of the style. In this design of sundial, the angle of the style to the dial plate is exactly the same as latitude, which is 53° 1′ 49″ the latitude of the Bridge Hill House. The dial plate will be perfectly horizontal, slight adjustments for latitude can be made were the dial moved by shimmying up the dial plate by the change in degree, from the horizontal. As the dial is now"
"Sail shade A shade sail is a device to create outdoor shade based on the basic technology as a ship's sail. Shade sails use a flexible membrane tensioned between several anchor points. While generally installed permanently, they are cheap and easy to set up. They are usually provided above public gathering places such as seating areas and playgrounds in countries where strong sun radiation makes prolonged stays in the open sun unpleasant or dangerous due to sunburn and skin cancer risk. Ancient Egyptians and later the Greeks and Romans used large pieces of fabric to provide shade. The Colosseum in"