UPSC Prelims 2022 Q29: Longest Day & Summer Solstice — Explained
In the northern hemisphere, the longest day of the year normally occurs in the:
- First half of the month of June
- Second half of the month of June
- First half of the month of July
- Second half of the month of July
Answer: (b) Second half of the month of June
Statement-wise explanation
- a: incorrect — The longest day comes with the June (summer) solstice. NOAA and National Geographic put the solstice between 20 and 22 June each year. The first half of June ends on 15 June, so the solstice cannot fall in it. Days in the northern hemisphere are still getting longer through early June.
- b: correct — At the June solstice the northern hemisphere is tilted most towards the Sun. The Sun is then overhead at noon on the Tropic of Cancer (23°30'N). This happens between 20 and 22 June, usually on 21 June. That day has the most hours of daylight anywhere north of the Equator.
- c: incorrect — By early July the days are already getting shorter, because the Sun's overhead position is moving south from the Tropic of Cancer. Early July is when Earth reaches aphelion, its farthest point from the Sun. Day length depends on the tilt of Earth's axis, not on its distance from the Sun.
- d: incorrect — By late July the Sun has moved even further south from the Tropic of Cancer, so days in the northern hemisphere are shorter still. Late July is often among the hottest times of year because land and air keep warming after the solstice. Hottest is not the same as longest.
How to eliminate
You can only solve this if you know one fact: the summer solstice falls on about 21 June. That date is the 'International Day of Yoga' date, and NCERT gives it in its chapter on the motions of the Earth. Once you know 21 June, the two July options go, and 21 is past the middle of June, so it is the second half. The July options are traps. They rely on two ideas that sound right but don't fit: that the hottest month (July, when heat lags behind the Sun) must have the longest day, and that early-July aphelion matters for day length. It doesn't. Distance from the Sun does not set day length. The tilt of the axis does. Remember: summer solstice about 21 June, winter solstice about 22 December, equinoxes about 21 March and 23 September.
Know more
Why day length changes. Earth's axis is tilted about 23.5° from the perpendicular to its orbit, and it points the same way all year. As Earth goes round the Sun, first one hemisphere and then the other leans towards the Sun. The hemisphere leaning towards the Sun gets longer days and more direct sunlight.
The four key dates (northern hemisphere view)
| Event | Approx. date | Sun overhead at noon | Northern hemisphere |
|---|---|---|---|
| Vernal equinox | 21 March | Equator | Day ≈ night |
| Summer solstice | 21 June (20–22) | Tropic of Cancer, 23°30'N | Longest day; 24-hour daylight inside the Arctic Circle |
| Autumnal equinox | 23 September | Equator | Day ≈ night |
| Winter solstice | 22 December | Tropic of Capricorn, 23°30'S | Shortest day; 24-hour night inside the Arctic Circle |
In the southern hemisphere everything is reversed: 21 June is its shortest day.
Traps to avoid
- Aphelion vs. solstice. Earth is farthest from the Sun in early July (aphelion) and closest in early January (perihelion). Northern summer happens near aphelion. This shows that distance does not cause the seasons. Tilt does.
- Longest vs. hottest. The most sunlight arrives at the solstice, but temperatures keep rising into July. Land and oceans take time to warm up.
- Latitude effect. At the Equator, day and night stay close to 12 hours each all year. The further you go from the Equator, the bigger the gap between the longest and shortest day. That is why June days are longer in Srinagar than in Kanyakumari.
- India link. The Tropic of Cancer passes through the middle of India. On about 21 June the noon Sun is directly overhead along that line.
NCERT Concepts to Revise
- Summer solstice: The question asks when the longest northern day falls, and that day is the summer solstice.
- Inclination of the Earth's axis: The tilt of Earth's axis is what makes day length change through the year. This question turns on that tilt.
- Tropic of Cancer: Where the noon Sun is overhead at the Tropic of Cancer tells you when the northern hemisphere's days are longest.
- Aphelion: Aphelion falls in early July. It helps you see why Earth's distance from the Sun is a distractor in the July options.