How to judge the length of day and night in a certain area?

Morning and dusk lines. The latitude on the earth is divided into two parts: the day arc and the night arc, and the length of the day and night arcs determines the length of the day and the length of the night, and the arc length of 15° is 1 hour. On the light map, the meridians divide the parallels into segments, and the longitude difference between adjacent meridians is generally 30° or 45°, which shows that the time difference between each longitude segment is 2 or 3 hours.

The length of day or night can be determined by reading the degrees of longitude.

The higher the latitude, the longer the days and the shorter the nights; The hemisphere (north or south) to which the point of direct fire moves, the day becomes longer and the night becomes shorter.

The morning and dusk lines coincide with the meridian planes, and the global day and night are equally divided; The intersection angle between the morning and dusk lines and the meridian plane is the largest (23°26'), and the difference between day and night is the largest.

The length of day and night is determined by looking at the corresponding lengths of the day and night arcs in the same latitude coil:

When the sunrise is known to be a: day length = 2 (12-a), night length = 2a, a + b = 24 hours.

When the sunset is known to be b: day length = 2 (a 12), night length = 48 2a

Day length = sunset Sunrise, night length = 24 day length.

Different regions with the same latitude have the same length of day and night.

When the sum of the day lengths of two parallels with the same north-south relative and equal latitude values is 24 hours, and when the sum of the night lengths is 24 hours, the relative values of day and night are equal (the night length of a certain latitude in the southern hemisphere is equal to the same latitude value in the northern hemisphere.

of day length).

The day length of a place is equal to the number of times that the day arc of the latitude coil where the place is located, and the night length is equal to the number of times that the night arc of the latitude coil where the place is located.

Let's start with the northern and southern hemisphere seasons.

The length of day and night is the length of time occupied by day and night.

The length of day and night varies according to the seasons:

Summer (Northern Hemisphere) has long days and short nights.

Winter (Northern Hemisphere): Short days and long nights.

Spring and autumn (global) day and night are equally divided.

By latitude: (for example, in the Northern Hemisphere).

In the summer half of the year, the days are longer than the nights at each latitude, and the higher the latitude, the longer the days and the shorter the nights.

In the winter half of the year, the day length is smaller than the night length at each latitude, and the higher the latitude, the shorter the day and the longer the night.

The day of the vernal and autumnal equinoxes equinoxes equinoxes are equinoxes globally.

The higher the latitude in the Northern Hemisphere summer, the longer the days Analysis:

1. Since the earth always maintains this angle of inclination around the sun in its motion, and the north pole is always facing the vicinity of the north star, the direct point of the sun only moves back and forth between the north and south latitudes. - You can use a sphere thing to demonstrate pondering, and it's easy to understand.

2. On the summer day (June 22), the sun shines directly on the Tropic of Cancer, and the area north of the Arctic Circle is irradiated by the sun 24 hours a day, forming a polar day. The area south of the Antarctic Circle (Antarctic Circle) does not see the sun for 24 hours a day, forming a polar night.

3. Think about it: the Arctic region is the polar day, and the daytime time is already the longest 24 hours, and it is impossible to have a longer daytime from the Arctic Circle to the south, of course, the shorter the daytime is the further south you go; On the contrary, the Antarctic region is the pole, and the night time is already the shortest 0 hours, and it is impossible to have a shorter daytime from the north of the Antarctic Circle, of course, the longer the daylight hours can only be longer the further north you go.

The algorithm for the difference between the length of day and night is as follows.

Familiarize yourself with the warp and weft lines.

basic nature.

On the same parallel, the length of day and night is equal everywhere, and the place of sunrise and sunset is the same; On the same meridian line, the local time is the same everywhere, and the longitude is 1 hour apart every 15° time, that is, the longitude is every 1°, and the local time is 4 minutes apart.

It can correctly identify the morning line and the evening line.

Morning and dusk lines. It is composed of two parts, the morning line and the dusk line, which follows the direction of the earth's rotation and enters the night hemisphere from the day hemisphere, which is called the dusk line; On the contrary, the one that enters the day hemisphere from the night hemisphere is called the morning line. The dot on the morning line coincides with sunrise, and the dot on the dusk line coincides with sunset.

Understand the distribution of the length of day and night.

The point where the sun shines directly.

Whichever hemisphere is shot directly, the day in that hemisphere is longer than the night, and the day length changes from low latitudes to high latitudes.

In the other hemisphere, the days are shorter than the nights, and the day length decreases from low latitudes to high latitudes.

There are several special cases to keep in mind.

The equinox is equinoxical to the global diurnal equinox, the diurnal equinox is equinoxical throughout the year on the equator, and the polar day is within the polar circle.

The length of the day is 24 hours, and the polar night is long.

The length of the night is 24 hours.

The methods and techniques for calculating the length of day and night are:

Calculated using the difference in longitude between two adjacent meridians.

On the light map, generally only a few meridians are given evenly, and the longitude difference between two adjacent meridians can be obtained by dividing 360° by the number of meridian intervals in the figure; Then according to the interval of the meridian crossed by the daytime arc, the longitude spanned by the daytime arc is calculated, and the longitude is multiplied by 1 15 to be the day length of the place.

It is calculated using the ratio of the day arc to the night arc.

The ratio of the day arc to the night arc can be estimated from the longitude spanned by the day and night arcs, if we find out: day arc arc = a, then day length = 24 (1 + 1 stupid nucleus a).

Calculated when using the sunrise and sunset.

When calculating places, the influence of the topography of the earth's surface, the elliptical shape of the earth and the scattering of the atmosphere on the length of the day are generally not considered, so the time interval from sunrise to noon and from noon to sunset is the same, if it is assumed that the place of nuclear attack on sunrise or sunset is a, then the day length of the place = 2 |12-a|。

Calculated using symmetrical latitude.

Two parallels with the same latitude in different hemispheres complement each other in terms of day and night. That is, the length of the day (night length) of a certain latitude is equal to the night length (day length) of another latitude with the same number of latitudes

The length of day and night can be judged by observing the position of the sun. Specifically, the change in the length of day and night can be further judged by judging whether the sun rises or sets, and combined with the change in the height of the sun over a certain period of time.

The change in the length of day and night is mainly related to the rotation and revolution of the earth. The rotation of the earth refers to the movement of the earth itself around the axis of rotation from west to east, so the appearance of the sun in one day can be regarded as the rise of the sensitivity caused by the rotation of the earth. Revolution refers to the orbital movement of the earth around the sun, which causes the earth's irradiation to the sun to have a certain regular change, which leads to a change in the length of day and night.

In addition, the Earth's rotation and revolution speed is uneven, which can also affect the length of day and night. Specifically, the old orbit of the Earth's orbit is approximately elliptical, so the distance from the Earth to the Sun will change depending on the season, so the impact on the duration of sunshine will also change. However, at the same location, the Earth's orbital speed and rotation speed are constant, so the phenomenon of day and night will not be disturbed.

In summary, we can judge the length of day and night by observing the changes in the position and altitude of the sun, referring to the rotation and celebratory revolutions, and the changes in the seasons. At the same time, we can also better understand the interaction between the earth and the sun and their impact on our lives through in-depth research on the rotation and revolution of the earth. <>

The length of day and night is caused by the rotation and revolution of the Earth. We can judge the length of day and night by observing the time of sunrise and sunset, as well as the height of the sun in the sky.

First of all, the length of day and night depends on the speed of the Earth's rotation. Earth's rotation is when the Earth rotates from west to east on its own axis. This process causes the sun and other stars to appear to rise in the east and set in the sky.

At the time of the Earth's rotation, the observer is in the position when the sun is on the horizon from the sunlight shining on that location, that is, during the day. As the Earth continues to rotate, the Sun leaves the horizon and rises higher in the sky. At this time, the sunlight will shine on the earth in the form of a corner.

When the Sun is at its highest point, the Sky Wheel is bright and hot. It's noon. Then, as the sun gradually sets, the observer's position becomes that the sun shines on the other side of the earth.

At this time, the sunrise can be seen by other observers on Earth. There will be periods of darkness on Earth as the different positions of observers on Earth and the Earth's rotation continues. After this dark night, the sun once again passes over the horizon and starts a new day.

Secondly, the length of day and night is also related to the rotation of the earth. Earth's revolution refers to the process by which the Earth revolves around the Sun. As the Earth rotates, the Sun moves through the sky in a slow rhythm from east to west.

When the Earth's revolution causes the Sun to move away from the Earth's normal, i.e., at the spring and autumn equinoxes, the length of day and night will be equal. As the Earth's revolution continues in daily activities, the Sun's rise and west setting and the changes in the sunshine area on Earth will become more significant, as will the length of day and night. As the sun crosses the sky from south to north, the summer solstice, the days in the Northern Hemisphere become longer and the nights shorter; Conversely, as the sun crosses the sky from north to south, that is, during the winter solstice, the days in the Southern Hemisphere become longer and the nights shorter.

In conclusion, the Earth's rotation and revolution are two important factors that affect the length of day and night. We can judge the length of day and night by looking at the height of the sun in the sky and the time of sunrise and sunset. At the same time, the orbit of the earth itself is from near to far, and spring, summer, autumn and winter are the cycles when people discover the length of day and night.

In addition, the altitude of the sun and the time of indifference can also be accurately measured by means of astronomical instruments, and the length of day and night can be determined. <>

The vernal equinox (March 21) and the autumnal equinox (September 23) are equinoxes of day and night globally.

Vernal equinox - autumn equinox (March 21 - September 23):

The days are longer and the nights are shorter in the Northern Hemisphere, and the higher the latitude, the longer the days and the shorter the nights. On June 22, the phenomenon of polar daytime oranges appeared north of the Arctic stool reputation circle.

In the Southern Hemisphere, the days are shorter and the nights are longer, and the higher the latitude, the longer the nights and the shorter the days. On June 22, the polar night phenomenon occurred south of the Antarctic Circle.

North Pole Half-year Polar Day;The South Pole is a half-year polar night.

Autumnal equinox - vernal equinox (September 23 - March 21):

In the Northern Hemisphere, the days are shorter and the nights are longer, and the higher the latitude, the longer the nights and the shorter the days. On September 23, the polar night phenomenon occurred north of the Arctic Circle.

In the Southern Hemisphere, the days are longer and the nights are shorter, and the higher the latitude, the longer the days and the shorter the nights. On September 23, the polar day phenomenon occurred south of the Antarctic Circle.

North Pole Polar Night;The South Pole is a half-year polar day.

The formula for calculating the length of day and night is as follows:Day length Sunset time Sunrise time Arc occupied by the day hemisphere 15=(12:00-sunrise hour) 2=(12:

00 + sunset time) 2 = 24 hours night length.

Night length (24:00 - sunset) 2=Night arc 15 = (0:00 + sunrise time) 2=24 hours Day length.

How to calculate the length of day and night:Fangdong Zen Method 1: Proportional Method.

1) In the side-view solar diagram, the proportion of the day arc and night arc divided by the morning and dusk lines is used to calculate.

2) In the top-down solar diagram, the radian ratio of the day arc and night arc divided by the morning and dusk lines is used to calculate.

Method 2: Sunrise and sunset time method.

1) Sunrise Time The moment when the latitude and morning lines meet.

2) Day length (12 days when the sun rises in place) 2.

3) Sunset Moment The moment when the local latitude and dusk line meet.

4) Day length (12 at sunset) 2.

Method 3: Symmetry method.

On the same day, the length of the day in a place in the Northern Hemisphere is equal to the length of a night in a place at the same latitude in the Southern Hemisphere;The length of the day in one place in the Southern Hemisphere is equal to the length of the night in one place at the same latitude in the Northern Hemisphere.

Does the landlord want to know how to calculate the length of the day on a specific day and place?There are the following algorithms:

Let : The geographic latitude of a place is ;

The declination of the sun on a given day (which can be understood as the latitude of the point where the sun shines directly) is δ;

Sunrise time tr;

The length of the day is ld;

The length of the night is ln;

Then: tr=arccos(tg *tgδ) 15;

It should be noted that:

1. The result of the inverse cosine function should be measured in degrees, because the rotation period of the earth relative to the sun (not the real sidereal period) is 24 hours, that is, the sun has made one rotation (360 degrees) on the celestial sphere in 24 hours, and 15 degrees is an hour, so the result should be divided by 15 to turn the result into hours.

2. This formula ignores the influence of air refraction and the apparent radius of the sun, so the morning and dusk circles can be approximated as a great circle of the earth.

3. Note: The sum δ north latitude is positive, and the south latitude is negative, and the calculated time is true solar time, which is not the same thing as the time we usually use.

4. When tg *tgδ>1, it is equal to 1, indicating that there is no sunrise time, and the sun is always in the sky; When tg *tgδ <-1, it is equal to -1, indicating that there is no sunrise moment, and the sun has been underground.

ld=(12-tr)*2;

ln=24-ld;

March 21-23 (one of the days) is the vernal equinox, and September 23 (one of the days) is the autumnal equinox, and the two days are equinoxical, that is, 6 a.m. to 18 p.m. is day, and the rest of the time is night.

After the vernal equinox, the days get longer and the nights get shorter, and the summer solstice (one of the days on June 21-23) has the longest days and the shortest nights, and then after this day, the days slowly get shorter, and the nights slowly get longer, until the autumnal equinox day and night become the same length, and after the autumnal equinox, the days become shorter and the nights become longer, until the winter solstice night is the longest and the day is the shortest until December.