1. The Common Distance Myth
Many people believe summer occurs because Earth is closer to the Sun. This is completely false! In fact, Earth is actually closest to the Sun in January (during the Northern Hemisphere's coldest winter!).
2. The $23.5^\circ$ Tilt and Revolution
Earth's axis is tilted at an angle of $23.5^\circ$ to the perpendicular of its orbital plane.
- Summer Solstice (June 21): Northern Hemisphere tilts directly towards the Sun. Solar rays strike vertically (concentrated heat); days are longest, creating summer in India.
- Winter Solstice (December 22): Northern Hemisphere tilts away from the Sun. Rays strike at a slanted angle (diffused heat); nights are longest, creating winter.
- Equinoxes (March 21 & September 23): Neither hemisphere tilts towards the Sun. Day and night are of strictly equal duration ($12\text{ hours}$ each) all across the globe.