March 19-20 recently marked the Spring equinox, the first day of spring in the Northern Hemisphere.
About Spring Equinox:
- The Equinoxes are astronomical events marking the two times of the year when the Sun is exactly above the equator.
- During these times, day and night are approximately equal in duration, hence the term “equinox” (Latin for “equal night”).
- On Earth, the equinoxes occur around March and September, known as the vernal and autumnal equinoxes respectively in the Northern Hemisphere.
- It is the opposite in case of the Southern Hemisphere.
- Spring Equinox is also known as the vernal equinox, it occurs around March 20th or 21st in the Northern Hemisphere and marks the beginning of spring.
- This is when the Sun crosses the celestial equator moving northward, bringing longer days and warmer temperatures to the Northern Hemisphere.
- It occurs when a planet’s subsolar point intersects its Equator, resulting in nearly equal durations of daytime and nighttime.
- Autumn (Fall) Equinox: It happens around September 22nd or 23rd in the Northern Hemisphere, signaling the start of autumn.
- During this time, the Sun crosses the celestial equator moving southward, leading to shorter days and cooler temperatures in the Northern Hemisphere.
Impact of Equinoxes:
- During equinoxes, solar declination is 0°, with the subsolar point directly over the Equator, causing the Sun’s rays to strike Earth’s surface perpendicular to the Equator.
- Before and after equinoxes, the subsolar point migrates north or south.
- It reaches the Tropic of Cancer around June 21 (June/summer solstice) and the Tropic of Capricorn around December 21 (December/Winter solstice).
- Although equinoxes theoretically indicate 12 hours of day and night, atmospheric refraction causes deviations, with day length slightly exceeding night length.
- Equatorial regions experience minimal equinoctial variation due to constant sunlight, while midlatitudes witness increased seasonal variation and disparity in day-night lengths.
- The 30° latitude experiences around 8 minutes longer days.
- In polar regions, equinoxes signal transitions from “midnight sun” to “polar night,” with daylight extending about 12 hours and 16 minutes.
- This leads to significant disruptions in satellite communications known as “Sun outages.”
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