What is the date of vernal equinox in the northern hemisphere
Show Hint
Equinox means "equal night" in Latin, which occurs twice a year when day and night are of equal length (12 hours each) everywhere on Earth.
The two equinoxes are the Vernal (March 21) and the Autumnal (September 23).
Step 1: Understanding the Concept:
An equinox is an astronomical event that occurs twice a year when the plane of the Earth's equator passes directly through the geometric center of the Sun's disk.
During an equinox, the tilt of the Earth's axis is perpendicular to the Sun's rays, resulting in nearly equal duration of day and night across the globe. Step 2: Detailed Explanation:
Let us review the key solar events and their corresponding dates for the Northern Hemisphere:
- Vernal Equinox (Spring Equinox): This occurs around March 20 or 21, marking the transition from winter to spring in the Northern Hemisphere.
At this time, the Sun crosses the celestial equator moving from south to north, and the subsolar point is located exactly at the equator. This corresponds to Option (B).
- Autumnal Equinox (Autumn Equinox): This occurs around September 22 or 23, marking the transition from summer to autumn in the Northern Hemisphere.
At this point, the Sun crosses the equator moving from north to south.
- Summer Solstice: This occurs around June 21 when the Northern Hemisphere is tilted at its maximum angle toward the Sun, resulting in the longest day of the year.
The subsolar point is located at the Tropic of Cancer (\(23.5^{\circ}\text{ N}\)).
- Winter Solstice: This occurs around December 21 or 22 when the Northern Hemisphere is tilted at its maximum angle away from the Sun, resulting in the shortest day of the year.
The subsolar point is located at the Tropic of Capricorn (\(23.5^{\circ}\text{ S}\)).
Therefore, the vernal equinox in the northern hemisphere occurs on March 21. Step 2: Final Answer:
The date of the vernal equinox in the northern hemisphere is 21st March.
