Chapter 12: Earth, Moon, and the Sun (Earth and Space)
Answers to all "Let Us Enhance Our Learning" questions of Chapter 12, Earth, Moon, and the Sun (NCERT Class 7 Science, Curiosity, 2026-27): rotation and revolution, day and night, the tilt of the Earth's axis and seasons, time differences, and solar and lunar eclipses. All 12 questions are answered, with the key answer highlighted.
In Fig. 12.17, how many hours of sunlight do the North Pole and the South Pole receive during one rotation of the Earth?
Solution
In Fig. 12.17, sunlight falls on the left half of the Earth, and the Earth's axis is tilted so that the South Pole leans towards the light and the North Pole leans away from it. As the Earth rotates, the South Pole always stays in the lit half and the North Pole always stays in the dark half.
North Pole:0 hours of sunlight (continuous night).
South Pole:24 hours of sunlight (continuous day).
North Pole: 0 hours; South Pole: 24 hours (it is tilted towards the Sun).
Fill in the blanks: (i) Stars rise in the ___ and set in the ___. (ii) Day and night are caused by the Earth's ___. (iii) When the Moon fully covers the Sun from our view, it is called a ___ solar eclipse.
State whether True or False: (i) Lunar eclipse occurs when the Sun comes between the Earth and the Moon. (ii) Sunrise happens earlier in Gujarat than in Jharkhand. (iii) In Chennai, the longest day occurs on the summer solstice. (iv) We should watch the solar eclipse directly with our naked eye. (v) Seasons occur due to the tilt of Earth's axis of rotation and its spherical shape. (vi) The Earth's revolution around the Sun causes day and night.
Solution
(i) False. A lunar eclipse occurs when the Earth comes between the Sun and the Moon.
(ii) False. The Earth rotates from west to east, so places in the east see the Sun first; sunrise is earlier in Jharkhand (east) than in Gujarat (west).
(iii) True. Chennai is in the Northern Hemisphere, where the longest day is on the summer solstice (around 21 June).
(iv) False. Looking at the Sun directly can permanently damage the eyes; use solar eclipse goggles or projection.
(v) True.
(vi) False. Day and night are caused by the Earth's rotation; revolution (with the tilt) causes seasons.
(i) F (ii) F, Jharkhand sees sunrise first (iii) T (iv) F (v) T (vi) F, rotation causes day and night
Padmashree saw the Orion constellation nearly overhead at 8 pm yesterday. When will she see Orion overhead today?
Solution
At about 7:56 pm today, that is, about 4 minutes earlier than yesterday. Because the Earth also revolves around the Sun, the stars rise (and reach overhead) about 4 minutes earlier each day.
At about 7:56 pm, about 4 minutes earlier than yesterday.
Nandhini saw a group of stars rising at midnight on 21 June. When will she see the same group of stars rising at midnight next year?
Solution
On 21 June next year. The stars rise about 4 minutes earlier each day; after one full revolution of the Earth around the Sun (one year), these daily shifts add up to a full day (4 min × 365 ≈ 24 h), so the same stars rise at the same time again on the same date.
On 21 June next year, after the Earth completes one revolution around the Sun.
Abhay noticed that when it was daytime in India, his uncle in the USA was generally sleeping as it was night-time there. What is the reason behind this difference?
Solution
The Earth rotates on its axis from west to east, so at any time only half of the Earth faces the Sun (day) and the other half is in darkness (night). India and the USA are on opposite sides of the Earth (about 10–12 hours apart in time), so when India faces the Sun, the USA faces away from it and has night.
Because of the Earth's rotation, only the half facing the Sun has day; the USA is on the opposite side of the Earth from India, so it has night when India has day.
Four friends used the following ways to see the solar eclipse. Who among them was being careless? (i) Ravikiran used a solar eclipse goggle. (ii) Jyothi used a mirror to project the Sun's image. (iii) Adithya saw the Sun directly with his eyes. (iv) Aruna attended a programme arranged by a planetarium.
Solution
(iii) Adithya was careless. Looking directly at the Sun, even during an eclipse, can permanently damage the eyes. The others used safe methods.
The Moon is much smaller than the Sun, yet it can block the Sun completely from our view during a total solar eclipse. Why is it possible?
Solution
Although the Sun is about 400 times larger than the Moon, it is also about 400 times farther away from the Earth. So, as seen from the Earth, both appear to be almost the same size in the sky. When the Moon passes exactly between the Sun and the Earth, it can just cover the Sun's disc completely. (Like a small coin held close to your eye can hide a big building far away.)
The Sun is about 400 times bigger but also about 400 times farther away, so from Earth both look nearly the same size and the Moon can just cover the Sun.
The Indian cricket team matches in Australia are often held in December. Should they pack winter or summer clothes for their trip?
Solution
Summer clothes. Australia is in the Southern Hemisphere. In December, the Southern Hemisphere is tilted towards the Sun, so it has summer, while India (Northern Hemisphere) has winter. (A light jacket may still be useful for cool evenings in some cities.)
Summer clothes: Australia is in the Southern Hemisphere, which has summer in December.
Why do you think lunar eclipses can be seen from a large part of the Earth when they happen, but a total solar eclipse can be seen only by a small part of the Earth?
Solution
During a lunar eclipse, the Moon moves into the Earth's large shadow. Since the Moon is then simply darkened, everyone on the night side of the Earth (about half the Earth) who can see the Moon sees the eclipse.
During a solar eclipse, the Moon's shadow falls on the Earth. The Moon is small, so its darkest shadow (umbra) covers only a small strip of the Earth's surface, often less than a few hundred kilometres wide. Only people in that strip see a total eclipse; others nearby see a partial eclipse, and most see none.
In a lunar eclipse the whole night side of Earth can see the darkened Moon; in a solar eclipse the Moon's small shadow covers only a narrow strip of Earth, so only people there see it total.
If the Earth's axis were not tilted with respect to the axis of revolution, what would be the effect on seasons?
Solution
There would be no seasons (or hardly any change through the year). Every place would receive the Sun's rays at the same angle all year round, and day and night would be about 12 hours each everywhere throughout the year. Places near the equator would always be hot and places near the poles always cold, with no summer or winter. (The small changes in the Earth's distance from the Sun would cause only very slight differences.)
There would be no seasons: each place would get the same sunlight all year, with days and nights of about 12 hours each everywhere.
