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https://blogs.nasa.gov/blog/tag/equinox/

From Spring Equinox To Autumn : First day of Springtime and Fall

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What is an Equinox?

More time was spent outside by the first people than it is now. They used the sky as a clock and a calendar at the same time. The course of the sun across the sky, the duration of daylight, and the location of sunrise and sunset could all be seen to change in a predictable way over the year.

Each equinox and solstice is now recognised as an astronomical event. It results from the Earth’s perpetual orbit around the sun and tilt on its axis. The tilt of the Earth is 23 1/2 degrees. Thus, during the year, the Northern and Southern Hemispheres of Earth alternate in whose region receives the most direct sunlight and warmth.

The Sun crosses what we refer to as the “celestial equator” at an equinox, which is really a hypothetical extrapolation of the Earth’s equator line. The Sun’s centre precisely crosses this line during the equinox.

For people in the Northern Hemisphere, the autumnal equinox occurs when the Sun crosses the equator moving from north to south; the vernal equinox occurs when it crosses from south to north. The opposite is true in the Southern Hemisphere.

Days get shorter than nights after the autumnal equinox as the Sun continues to rise later and nightfall comes earlier. The winter solstice marks the conclusion of this and the beginning of new day lengthening.

When the tilt of the Earth’s axis and Earth’s orbit around the sun combine in such a way that the axis is inclined neither away from nor toward the sun, we experience an equinox twice a year in the spring and fall. Around the equinox, the sun’s rays are distributed roughly equally between the two hemispheres of Earth. As seen from the equator, the sun is overhead at midday. Day and night are roughly equal.

Naturally, Earth’s orbit around the sun never stops. These days of roughly equal daylight and darkness will end soon.

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CourtesySpace.com

Earth During Equinox

The position of the sunrise and sunset, as well as the days with roughly equal amounts of daylight and darkness, will change quickly since Earth never stops orbiting the sun.

The Astronomy Picture of the Day for March 19, 2014, is the video embedded below. APOD explanation

Why Does the Sun Change Direction?

The subsolar point, which is located on the Earth’s surface immediately beneath the Sun, steadily moves along a north-south axis over the course of a year. At the June solstice, when it reaches its northernmost point, it begins to move southward until the September equinox, when it crosses the equator. The southernmost part of its voyage is at the December solstice.

The ecliptic, a hypothetical plane made by Earth’s orbit around the Sun, is slanted at an angle of roughly 23.4°, which causes the subsolar point to travel north and south throughout the course of the year. The subsolar point is located north of the equator in June, when the Northern Hemisphere is inclined toward the Sun. The Southern Hemisphere gradually receives more sunshine as the Earth moves toward the opposite side of its orbit, which it reaches in December, and the subsolar point moves south.

solar system g20315ffe8 1920
Image by 0fjd125gk87 from Pixabay
Why Is It Known as the “Equinox”?

All areas of the Earth see roughly the same number of hours of sunlight on the days of the equinoxes because the Earth’s axis is perpendicular to the Sun’s rays. In other words, day and night are, in theory, the same length everywhere. The term “equinox,” which is taken from Latin and means “equal night,” refers to this.

This literal translation is not totally accurate, though. Equinox days do not actually have 12 hours of daylight and 12 hours of darkness.

Spring Equinox

The March equinox, also known as the spring equinox or vernal equinox, takes place when the Sun crosses the equator in a northerly direction. In the northern hemisphere, this occasion heralds the arrival of spring. The Northern Hemisphere starts to tilt closer toward the Sun after this day, lengthening the day and raising temperatures.

The Sun travels from south to north across the celestial equator in spring every year. Because it is a fictitious line in the sky above the equator of the Earth, it is known as the “celestial” equator. The Sun would travel north when directly overhead if you were standing on the equator.

Only twice a year, on the equinoxes, does everyone on Earth experience the Sun rising in the east and setting in the west.

The Earth’s tilt in relation to the Sun is zero while the Sun is above, which implies that the axis of the Earth does not point in either a direction toward or away from the Sun.

equinox
CourtesyUtkaltoday.com

The Northern Hemisphere tilts toward the Sun following the spring equinox. Following the winter solstice, the amount of daylight has been growing daily in most regions (the North Pole and Equator being exceptions), but after the spring equinox, many places will see more daylight than darkness in each 24-hour day. Up to the summer solstice in June, when there is the longest time of daylight, the amount of daylight each day will grow.

Autumn Equinox

The astronomical event known as the autumnal equinox signals the beginning of autumn (or “fall”). The autumnal equinox takes place in September in the Northern Hemisphere and in March in the Southern.

The Harvest Moon

The full moon that falls closest to the autumnal equinox is known as the “Harvest Moon.” In the past, it was believed that the Harvest Moon’s brightness allowed farmers to work into the night to bring in the crops from the fields. In September, the Harvest Moon frequently occurs.

  • The equinox may occur on a different day depending on where you are due to time zone differences.
  • Although Saturn also experiences equinoxes, they only occur roughly every 15 years due to Saturn’s almost 30-year orbital period around the Sun.
YearEquinox (Types)Equinox (Southern Hemisphere)Equinox (Northern Hemisphere)
2022AutumnalSunday, March 20Thursday, September 22
2023AutumnalMonday, March 20Saturday, September 23
2022SpringThursday, September 22Sunday, March 20
2023SpringSaturday, September 23Monday, March 20

Equinoxes of Saturn

saturn g6045bcb0a 1920
Image by WikiImages from Pixabay

Equinoxes are not unique to Earth; as they orbit the Sun, all planets with noticeably tilted axes of rotation pass through two equinox points. However, Saturn is especially beautiful at these times since its bright rings appear to vanish!
The Sun illuminates Saturn’s rings, which are made of icy particles rotating in a thin disc parallel to the planet’s equator, during the Saturnian year.
However, the rings are edge-on to the Sun and cast themselves into shade as the planet reaches equinox, disappearing from view.
The equinoxes on Saturn occur just once every 14.7 Earth years. Two years after finding the rings, in 1612, Galileo saw this unusual occurrence and gasped, “Has Saturn swallowed his children?”

Click Here To Know About The Beautiful Astronomical Calendar Of 2022.

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