Tomorrow, Indonesia will have the rare phenomenon of the equinox, which only occurs twice a year
Netgenz - Technology | A very rare September equinox event in Indonesia could happen tomorrow (23/9). The equinox events occur twice a year, namely in March and September. It usually occurs on March 20-21 and September 22-23. On an equinox day, the sun will come out almost right in the east and set just in the west. Equinox is defined as the state of the Earth when the Northern Hemisphere or Southern Hemisphere receives the same amount of solar radiation and the same duration of time. The term equinox comes from the Latin word equinoctial, equal which means the same, and Noctis which means night. Literally, the meaning of the equinox is more appropriate to the condition of the Earth, where the Northern Hemisphere or Southern Hemisphere receives the same amount of solar radiation and the same duration of time.
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This is because the Northern Hemisphere is neither inclined nor "closer" to the Sun, nor is it farther away from the Sun. The same thing happened in the Southern Hemisphere. When viewed from observers of the Solar System outside the Earth, the status of the Earth's rotation axis is upright on the plate in the direction of the Sun's light to Earth. This causes the terminator (the day-night boundary) on Earth to coincide with the meridian or geographic longitude of each Earth's surface.
Equinox events that occur twice a year in March and September
This is also what causes every place on Earth to feel the night is not so long and not so short. The length of day and night for any place on Earth is almost the same. Although in reality, it does not fit 12 hours because it is controlled by atmospheric refraction. Through Instagram, LAPAN describes the September equinox as the point of intersection of the ecliptic and the celestial equator through which the Sun passes as part of the Sun's apparent annual journey from the Northern Hemisphere to the Southern Hemisphere. LAPAN explained that this year's September equinox could occur on September 23, 2021.
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Why does the equinox occur?
This change in the setting out of the Sun to be more north and south occurs due to the apparent annual motion of the Sun. This apparent annual motion arises because the Earth's axis of rotation is tilted 66.5 degrees when it circles the Sun. This makes the direction out and setting of the Sun will appear to turn quite north or quite south for a year when viewed in equatorial regions such as Indonesia. This exit and sunset status only exists in the west and east directions at the same time as the equinox event. In addition, for observers who are right in the equatorial area, because of this event, the Sun will look just above the head during the day.
Meanwhile, for observers in the northern hemisphere such as the United States, this tilt causes the northern hemisphere to experience a longer day. Meanwhile, when it coincides, observers in the Southern Hemisphere such as Australia feel a long night, as quoted from the official website of the National Aeronautics and Space Agency (LAPAN).