How did the ancients use the light shadow of the sun to record time?

It is called a sundial, which is an astronomical instrument used to observe the shadow of the sun and determine the apparent sun. It consists of two parts: the needle and the surface. According to the surface direction, it can be divided into equatorial type, horizontal type, vertical type and inclined type. The sundial, also called "sundial", is a kind of time measuring instrument in ancient China. Its principle is to use the shadow cast by the sun to measure and divide time. A sundial usually consists of a copper pointer and a stone disk. This method of timing by the projection of sunlight is a great invention of human beings in the field of astronomical timing, which has been used for thousands of years.

A device that uses the shadow cast by the sun to determine time. Also known as "solar gauge" (1), the shadow of the sun. China ancient time measuring instrument. It consists of a grating needle and a grating disk. The grating needle is perpendicular to the disk surface, and the time can be measured by the direction of the sun shadow on the disk surface. Due to the different directions of the disks, sundials can be divided into horizontal sundials, equatorial sundials, vertical sundials and inclined sundials. The early history of sundials is still unclear. The earliest reliable record is the short shadow level (namely horizon) invented by Yuan Chong in the 14th year of Sui Kai (594) mentioned in Tian Wenzhi. The clear record of the equatorial sundial was first seen in the shadow picture described in Volume II of Zeng Minxing's "Lonely Wake Magazine" in the Southern Song Dynasty, but the dial was made of wood. Later, it was changed to stone grate plate and metal grate needle. The Forbidden City in Beijing and other places have preserved the stone equatorial sundial made in Qing Dynasty. The surface of the equatorial sundial is parallel to the equatorial plane, and its pointer points to the north and south poles.

After a long stalemate, the sundial gradually moved. -A?vagho?a Xi Zhong's "The Story of the Wolf in Zhongshan" is a timekeeping instrument that used the sun shadow to measure time in ancient China. It usually consists of a copper pointer and a stone disk. The pointer made of copper is called "Gong Pin", which passes through the center of the disk vertically and acts as a neutral rod in the standard watch. Therefore, Gong Pin is also called "table", and the disk made of stone is called "Gong Mian". On the stone platform, the stone platform is high in the south and low in the north, making Gong Mian parallel to the equatorial plane of the sky. In this way, 12 large squares are carved on the front and back sides of the brick surface, and each large square represents two hours. When the sun shines on the sundial, the shadow of the sundial needle will be cast on the surface of the sundial, and the sun will move from east to west, and the shadow cast by the sundial needle on the surface will slowly move from west to east. The proportion of brick surface is uneven. Therefore, the moving shadow of the coffin needle seems to be the pointer of modern clocks and watches, and the coffin surface is the surface of clocks and watches to show the time. In the morning, shadows are cast near Shi Mao at the western end of the disc. Then, the shadow gradually becomes shorter and moves northward (below). When the sun reaches the highest position due south (upper meridian), the needle shadow is located due north (lower), indicating the local noon time. In the afternoon, the sun moves west and the shadow leans east, pointing to each hour in turn.

The sundial, also called "sundial", is a kind of time measuring instrument in ancient China. It usually consists of a copper pointer and a stone disk. The pointer made of copper is called "Gong Pin", which passes through the center of the disk vertically and acts as a neutral rod in the standard watch. Therefore, Gong Pin is also called "table", and the disk made of stone is called "Gong Mian". On the stone platform, the stone platform is high in the south and low in the north, making Gong Mian parallel to the equatorial plane of the sky. In this way, 12 large squares are carved on the front and back sides of the brick surface, and each large square represents two hours. When the sun shines on the sundial, the shadow of the sundial needle will be cast on the surface of the sundial, and the sun will move from east to west, and the shadow cast by the sundial needle on the surface will slowly move from west to east. Therefore, the moving shadow of the coffin needle seems to be the pointer of modern clocks and watches, and the coffin surface is the surface of clocks and watches to show the time.

From the vernal equinox to the autumnal equinox, the sun always runs on the north side of the celestial equator, so the shadow of the ray needle is cast above the ray plane; From the autumnal equinox to the vernal equinox, the sun runs on the south side of the celestial equator, so the shadow of the needle is cast below the surface of vernal equinox. therefore

Copper pointer is called "pointer"

When observing the sundial, we must first know the projection position of the sundial needle in two different periods.

The earliest sundial in the world was born in the great kingdom of Babylon six thousand years ago. The earliest documentary record in China is the short shadow level, namely the horizon sundial, which was invented by Yuan Chong in the 14th year of Emperor Yangdi's reign in 574 AD. The clear record of the equatorial sundial was first seen in the shadow picture described in Volume 2 of Zeng Minxing's "Lonely Wake Magazine" in the Southern Song Dynasty.

The equatorial sundial usually consists of a copper pointer and a stone disk. The copper pointer is called "gong needle", which passes through the center of the disc vertically. The gong needle is also called "watch". The stone plate is called the "gong face" and placed on the stone platform, with the south high and the north low, so that the gong face is parallel to the equatorial plane, and the upper end of the gong needle just points to the north celestial pole, and the lower end is just right. 12 cubes are carved on both sides of the brick surface, and each cube represents two hours. When the sun shines on the sundial, the shadow of the sundial needle will be cast on the surface of the sundial, and the sun will move from east to west, and the shadow cast by the sundial needle on the surface will slowly move from west to east. Therefore, the moving shadow of the coffin needle seems to be the pointer of modern clocks and watches, and the coffin surface is the surface of clocks and watches to show the time.

This method of timing by sunlight projection is an important invention of human beings in the field of astronomical timing. This invention has been used by human beings for thousands of years. But the sundial has a fatal weakness, that is, it can't be used in rainy days and at night. It was not until 1270 that early mechanical clocks appeared in Italy and Germany, while China got two foreign clocks in 160 1. Therefore, it is still a modern thing to completely abandon the sundial and get to know Guang Chen by looking at the clock.

An ordinary sundial, measured by the shadow of the sun, has any kind of sundial. The angle between the sundial and the ground plane must be the same as the local geographical latitude and point to the North Pole correctly, that is, there is a pointer parallel to the earth's rotation axis. By observing the projection of this pointer on the designated area, the time can be determined. According to the location of the sundial, the common sundial can be divided into the following different forms:

(1) Horizontal sundial Horizontal sundial is the most commonly used sundial. It uses a horizontal dial. The inclination of the sundial axis is set according to the latitude of the place of use, and the scale needs to be calculated and determined by trigonometric function. Suitable for use in low latitudes.

(2) Equatorial sundial The equatorial sundial is a device that fixes the axis (hour hand) toward the north pole according to the latitude of the place of use, and observes the scale of the projection of the axis on the disk perpendicular to the axis to judge the time. The scales on the disk are equally divided, and the shadows of the summer and winter axes projected on the disk will be divided into the north and south parts of the disk, which is suitable for middle and low latitudes. If the disc is changed into a ring, it is called the equatorial compass sundial.

(3) The polar dial provides a plane on which the clockwise hand is projected, which is parallel to the clockwise hand, that is, the angle with the ground plane is the same as the geographical latitude, and faces due north. The depiction of time can be handled by a simple geometric diagram, and the time axis of projection is a parallel line. Suitable for all latitudes.

(4) The dial of the south-facing vertical dial is a sundial facing south and perpendicular to the ground. This kind of sundial is suitable for mid-latitude (30 ~ 70).

(5) A direct sundial in the east or west, with its dial facing due east or west and perpendicular to the ground. This sundial can only be used in the first half (east) or the second half (west), but it is suitable for all latitudes in the world.

(6) The dial with horizontal and vertical scales adopts vertical sundial. This kind of sundial needs to be calibrated according to the direction of the building wall, so it is not easy to make. Depending on the season and time, sometimes there is no shadow. The sundials in the south and perpendicular to the east and west can be regarded as special cases of this shape.

(7) The projection sundial does not have an hour hand, but just draws ellipses with different oblateness on the ground plane according to different geographical latitudes, and draws a time line on it, with the long axis pointing in the positive east-west direction, while the short axis in the north-south direction needs to be engraved with a date to indicate the correct position of the vertical rod measuring time.

(8) Place a flat sundial horizontally on the surface of a flat sundial, and the pointer of the sundial points to the north pole. The angle between the sundial and the needle is the local geographical latitude.

Angle calculation, etc. Besides the correct installation of the pointer, the description of the timeline can not be ignored. The timeline description of various sundials is related to the geographical position of sundials and the height of the hour hand. Suppose the geographical latitude is φ, the height of the hour hand is h, and the difference between the time to be marked and noon is t; The angle between the time axis and the hour hand is a, and the distance is d, then the calculation formula of each sundial is as follows:

(1) horizontal sundial: TAN(A)=TAN(T)*SIN(φ)

(2) Equatorial sundial: bisecting the disk, which is equivalent to 15 degrees per hour, and the noon line is vertically downward.

(3) polar coordinates: D=H*TAN( 15*T)

(4) Southward vertical sundial: TAN(A)=TAN(T)*COS(φ)

(5) East or west vertical type: D=H*TAN((6-T)* 15)

(6) Horizontal and vertical formula: tan (a) = sin (o) * tan (r+15 * t)

Refers to the angle between the hour hand and the vertical line of the wall, TAN(W)=SIN(θ)*COT(φ)

Refers to the angle sin (o) between the height of the hour hand and the wall surface = cos (θ) * cos (φ).

Refers to the time line difference between the hour hand and the noon line COT(R)=COT(θ)*SIN(φ)

The included angle between 6 o'clock and 12 time line COT(S) =SIN(θ)*TAN(φ).

θ: the oblique angle of the sundial wall.

(7) Projection sundial: D= SIN(T* 15), V= sin(φ)*COT(φ).

The ratio of major axis to minor axis of ellipse: sin(φ)

The position of the vertical pole (where people stand): Z=TAN(del)*COS(φ)

Del: the declination of the sun, and v: the value of the time point in the short axis direction.

D: the value of the time point in the long axis direction.

From the vernal equinox to the autumnal equinox, the sun always runs on the north side of the celestial equator, so the shadow of the ray needle is cast above the ray plane; From the autumnal equinox to the vernal equinox, the sun runs on the south side of the celestial equator, so the shadow of the needle is cast below the surface of vernal equinox. Therefore, when observing the sundial, we must first understand the projection position of the sundial needle in two different periods. China ancient time measuring instrument. It consists of a grating needle and a grating disk. The grating needle is perpendicular to the disk surface, and the time can be measured by the direction of the sun shadow on the disk surface. Due to the different directions of the disks, sundials can be divided into horizontal sundials, equatorial sundials, vertical sundials and inclined sundials. The early history of sundials is still unclear. The earliest reliable record is the short shadow level invented by Yuan Chong in the 14th year of Sui Kai (594) mentioned in Tian Wenzhi. The clear record of the equatorial sundial was first seen in the shadow picture described in Volume II of Zeng Minxing's "Lonely Wake Magazine" in the Southern Song Dynasty, but the dial was made of wood. Later, it was changed to stone grate plate and metal grate needle. The Forbidden City in Beijing and other places have preserved the stone equatorial sundial made in Qing Dynasty. The surface of the equatorial sundial is parallel to the equatorial plane, and its pointer points to the north and south poles. After a long stalemate, the sundial gradually moved. -A?vagho?a Xi Zhong "The Legend of the Wolf in Zhongshan"

(2) sundial: a device that uses the shadow cast by the sun to determine the time. Also known as "solar gauge", it is an ancient time measuring instrument in China that used the sun shadow to measure time. It usually consists of a copper pointer and a stone disk. The pointer made of copper is called "Gong Pin", which passes through the center of the disk vertically and acts as a neutral rod in the standard watch. Therefore, Gong Pin is also called "table", and the disk made of stone is called "Gong Mian". On the stone platform, the stone platform is high in the south and low in the north, making Gong Mian parallel to the equatorial plane of the sky. In this way, 12 large squares are carved on the front and back sides of the brick surface, and each large square represents two hours. When the sun shines on the sundial, the shadow of the sundial needle will be cast on the surface of the sundial, and the sun will move from east to west, and the shadow cast by the sundial needle on the surface will slowly move from west to east. Therefore, the moving shadow of the coffin needle seems to be the pointer of modern clocks and watches, and the coffin surface is the surface of clocks and watches to show the time.

From the vernal equinox to the autumnal equinox, the sun always runs on the north side of the celestial equator, so the shadow of the ray needle is cast above the ray plane; From the autumnal equinox to the vernal equinox, the sun runs on the south side of the celestial equator, so the shadow of the needle is cast below the surface of vernal equinox. Therefore, when observing the sundial, we must first understand the projection position of the sundial needle in two different periods.

A sundial, also known as a sundial, is a timer used by ancient people to set time by the shadow of the sun. There are many kinds of sundials, which can be divided into horizontal, equatorial, meridian and unitary according to their different positions, and their functions are also different.

The earliest sundial in the world was born in the kingdom of Babylon 6000 years ago. The earliest documentary record in China is the short shadow level, namely the horizon sundial, which was invented by Yuan Chong in the 14th year of Emperor Yangdi's reign in 574 AD. The clear record of the equatorial sundial was first seen in the shadow picture described in Volume 2 of Zeng Minxing's "Lonely Wake Magazine" in the Southern Song Dynasty.

The equatorial sundial usually consists of a copper pointer and a stone disk. The copper pointer is called "gong needle", which passes through the center of the disc vertically. The gong needle is also called "watch". The stone plate is called the "gong face" and placed on the stone platform, with the south high and the north low, so that the gong face is parallel to the equatorial plane, and the upper end of the gong needle just points to the north celestial pole, and the lower end is just right. 12 cubes are carved on both sides of the brick surface, and each cube represents two hours. When the sun shines on the sundial, the shadow of the sundial needle will be cast on the surface of the sundial, and the sun will move from east to west, and the shadow cast by the sundial needle on the surface will slowly move from west to east. Therefore, the moving shadow of the coffin needle seems to be the pointer of modern clocks and watches, and the coffin surface is the surface of clocks and watches to show the time.

The sundial in the palace

This method of timing by sunlight projection is an important invention of human beings in the field of astronomical timing. This invention has been used by human beings for thousands of years. But the sundial has a fatal weakness, that is, it can't be used in rainy days and at night. It was not until 1270 that early mechanical clocks appeared in Italy and Germany, while China got two foreign clocks in 160 1. Therefore, it is still a modern thing to completely abandon the sundial and get to know Guang Chen by looking at the clock.

Portable folding sundial A portable sundial is called a folding sundial. It has two small surfaces hinged together. Usually, it is folded up and put in a small flat box, which is convenient to put in your pocket. Dial hands are belts between two dials. When the belt is pulled and straightened, the two watch surfaces will be perpendicular to each other, with one surface forming a vertical sundial and the other surface being a horizontal sundial. The most exquisite material of noodles is made of white ivory, decorated with dark real lacquer from China, and the needles are black silk, linen or hemp fibers.

If you tie a knot in the right position on the needle as a node, the folding sundial can also be used as a calendar, at least to show the appropriate time for farming.

The folding sundial can be adjusted by combining two surfaces with different angles (which will produce different projections). When both sides of the sundial show the same time and the hinge is horizontal, the folding sundial indicates the local sun time. In addition, when the hinge faces north (in the northern hemisphere), the folded sundial can only be parallel to the earth's rotation axis by rotating an angle. Then at noon, sunrise and sunset, the time of folding the sundial will not be affected by the latitude change, but at 9: 00 am and 3: 00 pm, the latitude deviation is 1 degree, which is between two sundials.

This means that the folding sundial can be used like a compass and even measure latitude. Some folding sundials are attached with small plumb hammers and indexers to read the correct latitude; Some have compasses, which can measure geographical features. In ancient times, large folding sundials (1 m or more) were used for navigation.

/kloc-portable sundial in the early 0/8th century

This sundial is made of brass, with a diameter of about 8 cm, and it is protected by a brass cover (not shown in the figure). Some functions enable him to maintain enough accuracy, such as the compass can correctly determine the north, and the time scale is 5 minutes. This sundial was made in 1742 by Gabriel Stokes, a mathematical instrument manufacturer in Dublin.

Elevation sundial

The astrolabe can show the correct date, which is a sundial used in navigation and astronomy.

Contour sundial

In design, it is a small flat ring with a small handle, just like an ornament on a watch chain, or a small ornament. . When the ring is hung by the handle, the small hole will cast a shadow on the inside of the ring, and the time can be displayed by the mark on the ring, but the user must know whether it is morning or afternoon. Usually this small hole is set on a piece of metal and can be slid and locked to adjust the date.

In modern times, American special forces still like to carve a simple sundial on the blade, so that they can still know when the watch fails. Points. . I want to divide it. . . You can have a sundial of your own.