Which day of the year has the longest pole shadow at 12 noon and which day has the shortest pole sha

The pole shadow at 12 noon is the longest:

Northern Hemisphere. The shadow of the pole is longest at noon on the winter solstice (around December 22).

Southern Hemisphere. The shadow of the pole is longest at noon on the summer solstice (around June 22).

Equator: The pole shadow is longest at noon on the winter solstice (around December 22) and summer solstice (around June 22).

The rod shadow at 12 noon is the shortest:

Tropic of Cancer. and the area north of it: the shortest shadow at noon on the summer solstice (around June 22).

Tropic of Capricorn. and the area south of it: the pole shadow is shortest at noon on the winter solstice (around December 22).

The area between the Tropic of Cancer and the Tropic of Capricorn: The day when the sun shines directly on the local latitude has the shortest shadow at noon – there are two days a year when the pole shadow is the shortest. For example, on the equator, the spring equinox (around March 21) and the autumn equinox (around September 23) have the shortest pole shadow.

Of the year, the shadow of the pole at 12 noon on the winter solstice is the longest, and the shadow of the pole at 12 noon on the summer solstice is the shortest.

If you say that the place north of Shantou (Tropic of Cancer), the sun is in the south all year round, the shadow is facing north, and on the summer solstice, the Tropic of Cancer sun shines directly, and the area north of him reaches the maximum solar elevation angle and day length at noon. Again, the rod shadow is the shortest.

The length of the rod shadow at noon varies from "long-short-long". This pattern of change is caused by the change in the height of the sun during the day. In the morning, the sun is lower and the rod shadow is longer; As the height of the sun gradually increases, the rod shadow is shortest at noon; In the afternoon, the height of the sun gradually decreases, and the pole shadow becomes longer again.

This pattern of variation can tell us about the local season and the magnitude of the angle of the sun's altitude at noon on that day. For example, the longest shadow of the slag fruit stem indicates that the sun is in the summer of the year, and the height of the sun at noon is the largest. If the shadow of the sedan chair is the shortest, it means that the sun is in the winter of the year, and the height of the sun at noon is the smallest. In addition, the ratio of rod length to shadow length can also be used to calculate the noon solar altitude angle of the local day.

In addition, if the rod shadow is 0 in length at noon, that is, there is no shadow, it means that the point where the pole is located is exactly the point where the sun is shining on the sail. If you take into account the direction of the pole shadow, you can also guess the direction of sunrise and sunset in the local area.

1. The change in the length of the shadow of the big pole at noon can know the local season, the longest time is the local summer, and the shortest time is the local winter.

2. Using the ratio of rod length to shadow length, you can calculate the size of the noon sun height on the day when the local socks are erected.

3. If the shadow length of the rod is 0 (at noon), it means that the point where the rod is located is exactly the point of direct sunlight.

If you take into account the direction of the rod shadow, you can also guess the direction of the local sunrise and sunset).

After long-term observation and recording, it has been found that the length of the rod shadow varies every day at noon (due south of the sun) during the year, and the change is regular: short summer, middle autumn, long winter, and middle spring.

(1) The reason for the change in the length of the pole shadow in a day is that the angle between the sunlight and the pole changes due to the rotation of the earth;

2) The reason for the change in the length of the pole shadow in a year is that the earth revolves around the sun, and the orbit of the revolution has an angle with the orbit of the earth, which changes the angle of irradiation between the sun and the pole during the year

3) As can be seen from the picture, the shadow of the pole at noon in the place where the student is located is facing north Therefore, he is in the northern hemisphere;

4) As can be seen from Figure 1, the rod shadow length at noon is the shortest and the solar altitude angle is the largest during the day.

5) According to Figure 2, applying this knowledge to architecture, the distance between the two residential buildings should be calculated according to the shadow of the building on the winter solstice in order to ensure that the window sill of the ground floor residents is exposed to sunlight throughout the year

So the answer is: (1) the rotation of the earth; (2) The earth revolves around the sun, and the direct point of the sun changes; (3) North; North; (4) short; Big; (5) Winter solstice

Sun noon altitude angle = 90 - geographic latitude + celestial declination.

For the summer solstice, the sun declination is taken; For the winter solstice, the sun declination is taken.

Take Shanghai as an example, at 31° north latitude.

Summer solstice day = 90°-31°+

Winter solstice day = 90°-31°

As for how to calculate the length of the rod shadow, I don't need to explain it, right?