Why is there day and night Why is there day and night

The rotation of the earth produces a diurnal cycle; The Earth's revolution produces seasonal changes. Since the earth is an opaque planet, the sun and stars give the earth light, and the side that shines on the sun is day and the other side is night. The earth is constantly rotating from west to east around its axis of rotation, and the phenomenon of celestial bodies rising in the east and setting in the west is a reflection of the earth's rotation.

One rotation of the earth is equivalent to the week when the sun rises in the east, sets and rises again, and it is also our daily day. As the Earth rotates, it revolves around the Sun, which rotates from west to east. The orbit of the Earth's revolution is an ellipse that is close to a perfect circle, and the Sun is located in a focal point.

The Earth's orbital period is one year, and astronomically it is 365 days, 5 hours, 48 minutes and 46 seconds. The angle between the Earth's orbit (ecliptic plane) and the Earth's rotation plane (equatorial plane) is 23 degrees 26 minutes, which causes the direct point of the Sun to move between the Tropic of Cancer in a one-year cycle, forming the four seasons in temperate regions. On March 21 every year, the direct sun point moves from south to north to the equator, and the global day and night are equinox, which is our vernal equinox day, and on June 22, the direct sun point moves north to the Tropic of Capricorn, becoming the longest day in the northern hemisphere, which is what we call the summer solstice, and then the direct sun point turns to move south, and on September 23, it hits the equator directly, which is the autumnal equinox, and on December 22, it moves to the Tropic of Capricorn, and it is our winter solstice.

The change of seasons is actually the result of the combined effect of the earth's rotation inclination and revolution around the sun, without one of these conditions, the change of seasons will not occur, and everything on the earth will change accordingly. The first volume of the high school geography textbook is available.

The earth itself does not emit light. The light and heat on the earth are mainly due to the fact that the sun is shining, and the hemisphere where the sun shines is daytime, and the place where the sun does not shine is night. The earth is a sphere, which constantly rotates from west to east around the earth's axis, which is called the rotation of the earth.

In this way, the part of the earth that receives the sun's heat is constantly changing. The part that gets the sun's heat is constantly changing, and the part that doesn't get the sun's heat is also changing, resulting in a constant alternation of day and night.

Remember.

Because of the rotation of the Earth, the Earth is an opaque sphere that is only half in the day and half in the night.

The autobiography of the Earth has formed the idea that facing the sun is day, and facing away from the sun is night.

The distinction between day and night that we see is due to the rotation of the earth. The Earth is an illuminated, opaque sphere, and it is constantly rotating in a permeable state, so at any one time, the Sun can only illuminate half of the Earth's surface. Half of the world illuminated by sunlight is day, and half of the world that is not illuminated by sunlight is night.

This creates day and night.

And because the Earth's axis is tilted, the length of day and night is different in different parts of the Earth. In the north and south poles of the earth, the sun shines obliquely throughout the year, and the length of day and night varies the most.

In the high latitudes of the northern and southern hemispheres, there will also be a phenomenon that the sun does not set or does not come out all day long, that is, 24 hours a day is day or night, which is the phenomenon of "polar day" and "polar night" in the polar region.

The cycle of day and night, which is the time interval between the sun passing through the same meridian twice in a row, is called a solar day. The solar day restricts human daily life and rest, so it is used as the basic unit of time.

In addition, the short duration of the solar day makes the entire surface of the earth heat and cool not to be excessively violent, thus ensuring the survival and development of living organisms on the earth.

Day and night belong to two different time periods of the day in Senhong. Daytime refers to the first moment of the morning sun until the sun sets, which is often referred to as daytime. Evening generally refers to the period from sunset to the end of the night.

As follows: Hello refers to the rupture, I am happy to answer for you, day and night belong to time, I hope mine is helpful to you, I wish you a happy life. Source contains.

Day and night are a 24-hour cycle, when the sun is rising, it is daytime, and when the sun goes down, it is night.

Day and night are two periods of day and night, and day and night are determined by sunrise and sunset.