What is the length of day and night in the Northern Hemisphere at the time of the vernal equinox? Wh

After the vernal equinox, the North Pole begins to appear in the polar day, and the range gradually expands outward to the summer solstice, the maximum range of the polar day, expanding to the Arctic Circle. After the summer solstice, the polar day range narrows inward from the Arctic Circle until the end of the autumnal equinox.

The direct sunlight on the summer solstice is at the Tropic of Capricorn, and the length of day and night in the Northern Hemisphere is the longest day and the shortest night, and the polar day phenomenon is stored in the Arctic circle.

The height of the Sun at noon in the region north of the Tropic of Cancer in the Northern Hemisphere reaches its maximum value of a year. The days are shortest and the nights are the longest in the Southern Hemisphere, and polar nights occur in the Antarctic Circle and areas south of it. The height of the sun at noon is the lowest everywhere.

Law. The polar day phenomenon occurs in the polar circle of the hemisphere where the direct sun shines on the sun. The range of the polar day is related to the latitude of the direct solar point, and the latitude difference between its boundary and the pole is the latitude of the direct solar point.

Therefore, after the vernal equinox, there will be a polar day near the North Pole, and the polar day will become larger and larger thereafter; It reaches its maximum on the summer solstice, and the border reaches the Arctic Circle.

After the summer solstice, the range of polar days near the North Pole gradually decreases, and it shrinks to 0 on the day of the autumnal equinox. After the autumnal equinox, the polar day appears near the South Pole, and the range of the polar day near the South Pole becomes larger and larger thereafter. Reaching its maximum on the winter solstice, the boundary reaches the Antarctic Circle; After the winter solstice, the range of polar days near the South Pole gradually decreases, reaching 0 on the vernal equinox.

Tomorrow is March 21, 2018, and people will usher in the mid-equinox of the spring three monthsVernal equinox。In ancient China, the day of the vernal equinox was the day when the emperor sacrificed to the sun, and it was also the time when folk farming entered the busy time, so it has always been regarded as important. And in astronomy, the vernal equinox is also a special time node, so let'sTo introduce you to the length of day and night in the northern hemisphere of the spring equinox.

Q: What is the length of day and night like in the Northern Hemisphere of the equinox?

Answer: On the day of the vernal equinox (and autumnal equinox), the sun shines directly on the equator, and the global day and night are of equal length, regardless of the southern hemisphere or the northern hemisphere, day and night are equinox, each for 12 hours. In addition, this day is infinitely day and night.

On the day of the vernal equinox, the sun shines almost directly at the Earth's equator, and the length of day and night is almost equal to that of the world (not taking into account the refraction of sunlight by the atmosphere and the shadow of morning and dusk). After the vernal equinox, the direct point of the sun continues to move from the equator to the northern hemisphere, and the days and nights are shorter in the northern hemisphere (the days are longer than the nights in the day), and the days are shorter and the nights are longer in the southern hemisphere (the days are shorter than the dark nights in the middle of the day). Therefore, the vernal equinox is also called the ascending equinox.

And at the North and South Poles, on the day of the vernal equinox, the sun is on the horizon all day. After that, as the direct sunlight continued to move northward, a six-month period of polar days began near the North Pole, and the range gradually expanded. A six-month period of polar night begins near the South Pole and gradually expands.

It is worth noting that the days are getting longer and longer from the winter solstice in the northern hemisphere, but the days are longer than the nights from the spring equinox; From the day of the summer solstice, the days get shorter and shorter, but from the autumnal equinox the days are shorter than the nights. The reasons for this are:

On the winter solstice, the sun directly hits the pure source line of the southward return, and the days are the shortest in the northern hemisphere, and then the direct sun begins to move northward, and the days are getting longer and longer in various parts of the northern hemisphere.

After the vernal equinox, the direct point of the sun moves to the Northern Hemisphere, where the days begin to be longer than the night. On the summer solstice, the sun shines directly on the Tropic of Capricorn, and the days are longest in the Northern Hemisphere, and then the direct sun begins to move south, and the days are getting shorter and shorter in the Northern Hemisphere. After the autumnal equinox, the direct point of the sun moves to the Southern Hemisphere, and the Northern Hemisphere begins to have shorter days than nights.

1. On the day of the vernal equinox (March 21), the sun shines directly on the equator, and the global day and night are of equal length, and there is no extreme day and night.

2. On the summer solstice (June 22), the sun shines directly on the Tropic of Capricorn, the days and nights in the northern hemisphere are short, the days in the southern hemisphere are short and the nights are long, the polar day in the Arctic Circle, and the polar night in the Antarctic Circle.

3. On the day of the autumnal equinox (September 23), the sun shines directly on the equator, and the global day and night are of equal length, and there is no pole of day and night.

4. On the winter solstice (December 22), the sun shines directly on the Tropic of Capricorn, the days are short and the nights are long in the northern hemisphere, the days are long and the nights are short in the southern hemisphere, the polar night in the Arctic Circle, and the polar day in the Antarctic Circle.

5. From the spring equinox to the autumnal equinox in the Northern Hemisphere, the days are longer than the nights; From the autumnal equinox to the spring equinox of the following year, the night is longer than the day, and the opposite is true in the southern hemisphere.

6. In the process of the earth's revolution around the sun, the earth's axis is always inclined to the orbital plane at an angle of 66 degrees and 34 minutes. Due to the tilt of the Earth's axis, the height of the Sun at different points on the Earth's surface is different when the Earth is in different positions in orbit.

7. When the sun is high, the sun shines directly and the heat is concentrated, as if it is facing the furnace; Moreover, the path of the sun in the sky is long, the sunshine hours are long, the days are long and the nights are short, and the temperature is bound to be high, which is the spring equinox to the autumn equinox.

8. On the contrary, when the height of the sun is small, the sunlight hits the ground obliquely, and the heat is dispersed, which is equivalent to facing the furnace obliquely; Moreover, the path of the sun in the sky is short, the sunshine hours are short, the days are short, the nights are long, and the temperature is low, which is the autumn equinox to the spring equinox of the following year.

Northern Hemisphere. The time period for the days to get shorter and the nights to get longer is from the summer solstice (June 21) to the autumn equinox (September 23) to the winter solstice (December 22).

But the summer solstice (June 21) - the autumn equinox (September 23) in the northern hemisphere day is longer than the night.

Autumnal Equinox (September 23) - Winter Solstice (December 22) The length of the day in the Northern Hemisphere is less than the length of the night.

Summer solstice: the days are longer and the nights are shorter in the Northern Hemisphere, and the days are longer the further north, with polar days occurring in the Arctic Circle and north of it; The days are short and the nights are long in the Southern Hemisphere, and the days become shorter the further south you go, and polar nights appear in the Antarctic Circle and south of it; The equator is equal in length for day and night.

Winter solstice: The days are short and the nights are long in the northern hemisphere, and the days are shorter the further north they go, with polar nights occurring in the Arctic Circle and north of it; The days are longer and the nights are shorter in the Southern Hemisphere, and the days get longer the further south you go, with polar days occurring in and south of the Antarctic Circle. The equator is equal in length for day and night.

Equinox and autumnal equinox days: the same length of day and night around the world.

The winter solstice day turns to the vernal equinox day is the northern hemisphere day and night, the winter solstice day is the day of the southern hemisphere, the day of the winter solstice is the longest night in the northern hemisphere, after the winter solstice, the direct point of the sun slowly moves to the northern hemisphere, the northern hemisphere gradually longer days and shorter nights, to the summer solstice day in the northern hemisphere day is the longest.

The earth revolution around the sun refers to the rotation of the earth around the sun according to a certain orbit. Just as the rotation of the earth has its own unique regularity, the rotation of the earth due to the action of the sun's gravitational field and rotation also has its own laws.

The rotation of the earth follows the laws of the earth's orbit, the earth's orbital plane, the yellow-red angle, the period of the earth's revolution, the speed of the earth's revolution and the effect of the earth's revolution. The time it takes for the earth to revolve is one year. There are two distinct cycles in the process of the Earth's revolution, which are the return year and the sidereal year, and the time of the return year is not the same as the sidereal year.

The one-year time difference between the two is called precession.

The time it takes for the earth to revolve is one year. There are two distinct cycles in the Earth's revolution, the return year and the sidereal year. The return year refers to the time interval between the two consecutive passes of the sun through the vernal equinox, that is, the time elapsed by the sun's center from west to east along the ecliptic from the vernal equinox to the vernal equinox, also known as the solar year.

1. The return year is a day, that is, 365 days, 5 hours, 48 minutes and 46 seconds. This is calculated based on the average of 121 regression years.

As shown in the figure, the dots on the graph represent the trajectory of the sun, which is the vernal equinox, when the sun shines directly on the equator, day and night are of equal length, and it is the autumnal equinox, and the situation is the same. It is the summer solstice, when the sun shines directly on the Tropic of Capricorn, the days are long and the nights are short in the northern hemisphere, the days are short and the nights are long in the southern hemisphere, it is the winter solstice, the days are long and the nights are short in the northern hemisphere, and the spring equinox.

In the process of moving from the winter solstice to the vernal equinox, the sun slowly turns north from the Tropic of Capricorn, and the days in the northern hemisphere slowly become longer until the vernal equinox, and then continue to get longer, until after the summer solstice, the days slowly become shorter.

You have to turn back slowly day by day, not right away