Summer Solstice
Explanation
The seasonal changes on Earth are driven by the revolution of the Earth around the Sun and the tilt of its axis ($66.5^\circ$ with the plane of its orbit). This orientation determines the angle of incidence of solar rays and the duration of daylight at different latitudes.
Detailed Analysis:
- Summer Solstice (June 21): On this date, the Northern Hemisphere is tilted towards the Sun. The rays of the Sun fall directly on the Tropic of Cancer ($23.5^\circ$ N). As a result, the Northern Hemisphere experiences the longest day and the shortest night of the year. This position is technically termed the Summer Solstice.
- Winter Solstice (December 22): The Southern Hemisphere is tilted towards the Sun, and the rays fall vertically on the Tropic of Capricorn. For the Northern Hemisphere, this marks the shortest day.
- Equinoxes (March 21 and September 23): On these dates, the direct rays of the Sun fall on the Equator. The whole Earth experiences equal days and equal nights.
Key Takeaway:
June 21st is known as the Summer Solstice because the Sun is vertically overhead at the Tropic of Cancer, resulting in maximum insolation for the Northern Hemisphere.