Class 7 Science · Original EZT practice
Earth, Moon, and the Sun (Class 7 Science Chapter 12): days, seasons and eclipses explained
Day turns to night because the Earth spins. Summer gives way to winter because the tilted Earth circles the Sun. And once in a while a shadow crosses the Sun or the Moon and the sky itself seems to flinch - an eclipse. All three follow from how these three bodies move. Below: the ideas in plain words, then original EZT practice with worked answers. (Note: this is original practice, not a textbook exercise key.)
10 original worked examples, 10 fresh self-check questions and 4 mixed questions, with explained answers. These are not copied textbook exercises, an official chapter index or a full answer key. No affiliation with NCERT is claimed.
Official sources for topic and edition context, checked 18 October 2026:
1. Rotation: why day follows night
Rotation is the spinning of the Earth on its own axis. As your part of the Earth turns towards the Sun you get daytime; as it turns away, night. One full rotation takes about 24 hours - one day.
2. Revolution: the year-long trip
Revolution is the Earth's journey around the Sun - one full trip per year. As the Earth moves, the stars visible in the night sky slowly change through the year.
3. The tilted axis: the real reason for seasons
The Earth's axis is tilted with respect to its orbit and keeps that tilt as it revolves. When a hemisphere tilts towards the Sun it gets more direct sunlight and longer days; when it tilts away it gets winter.
4. Solar eclipse: the Moon steps in front
When the Moon passes directly between the Sun and the Earth, it can block the Sun's light from reaching us. The Moon is far smaller than the Sun but also far closer to us, so from Earth it can cover the Sun's disc.
5. Lunar eclipse: the Earth's shadow
When the Earth comes between the Sun and the Moon, the Earth's shadow falls on the Moon. A lunar eclipse can happen only on a full-moon night and is safe to watch with the naked eye.
Choose, solve, check, then try a fresh question.
Before calculating, read the method prompt and name the condition that makes it useful. Write your own attempt. Open the steps only when you need them, and use the check to catch a wrong sign, unit or interpretation. Finish with the fresh question before reading its answer.
Use rotation to explain day and night
Choose the method: Track which side of the rotating Earth faces the Sun.
EZT practice question
If it is noon in Delhi, what is it in a place exactly on the opposite side of the Earth, and why?
Show the worked solution
- Noon means Delhi's side faces the Sun.
- The opposite side faces away from the Sun as the Earth rotates.
Answer: It is about midnight there because that side faces away from the Sun.
Check: The two places are on opposite sides, so one receives sunlight while the other is in darkness.
Watch for this: Do not say the Sun moves to the other side; the Earth's rotation changes which side is lit.
Now try it yourself
If one place is at sunset, what is happening to that place as the Earth rotates?
Check your answer
It is turning away from the Sun.
Rotation carries it from daylight into darkness.
Explain an apparent sunrise
Choose the method: Separate what appears to move from what actually moves.
EZT practice question
Does the Sun actually rise and set?
Show the worked solution
- The Sun stays where it is relative to this daily motion.
- The Earth's rotation carries us into and out of sunlight.
Answer: No. The Sun only appears to rise and set because the Earth rotates.
Check: The same model explains noon, sunset and midnight as rotation positions.
Watch for this: Do not describe the Sun as travelling around a fixed Earth in this chapter.
Now try it yourself
Why does the Sun appear to move across the sky during the day?
Check your answer
Because the Earth rotates.
Our viewpoint turns while the Sun's light stays in place.
Connect revolution with the changing night sky
Choose the method: Remember that the night side faces different directions in space through the year.
EZT practice question
Why do we see different constellations in summer and winter nights?
Show the worked solution
- As the Earth revolves around the Sun, its night side faces different directions in space.
- Different parts of the sky are therefore visible after dark at different times of year.
Answer: Revolution changes the direction of our night sky, so different constellations come into view.
Check: The change is gradual across the year, not a daily rotation effect.
Watch for this: Do not confuse the year's changing constellations with the nightly spin of the sky.
Now try it yourself
Why can a constellation visible after dark in January be absent after dark in July?
Check your answer
The Earth has moved around the Sun, so its night side faces another part of space.
That is the revolution effect.
Explain opposite seasons
Choose the method: Check which hemisphere tilts towards the Sun at that time.
EZT practice question
It is July. Why is it summer in India but winter in Australia?
Show the worked solution
- In July the Northern Hemisphere tilts towards the Sun.
- The Southern Hemisphere tilts away from the Sun at the same time.
Answer: India gets summer while Australia gets winter because the two hemispheres tilt in opposite directions relative to the Sun.
Check: More direct sunlight and longer days match the hemisphere tilted towards the Sun.
Watch for this: Do not explain seasons by saying the whole Earth is nearer the Sun.
Now try it yourself
When it is winter in India, what season is it in Australia?
Check your answer
Summer.
The Southern Hemisphere then tilts towards the Sun.
Test the role of the tilt
Choose the method: Remove the tilt and ask what would change through the year.
EZT practice question
Would we have seasons if the Earth's axis were perfectly upright?
Show the worked solution
- Without tilt, neither hemisphere would lean towards or away from the Sun through the year.
- Each place would get roughly the same sunlight pattern all year.
Answer: No. The tilt is essential to the changing seasons.
Check: Revolution alone does not change which hemisphere receives the more direct sunlight.
Watch for this: Do not blame distance from the Sun for the main seasonal pattern.
Now try it yourself
If the axis had no tilt, would summer days still be longer than winter days?
Check your answer
No.
The changing day length also comes from the tilt.
Link tilt to day length
Choose the method: Follow the Sun's daily path when your hemisphere leans towards it.
EZT practice question
Why are summer days longer than winter days?
Show the worked solution
- When your hemisphere tilts towards the Sun, the Sun's daily path across your sky is longer.
- It therefore stays above the horizon for more hours.
Answer: The tilt gives the Sun a longer path across the summer sky, so daylight lasts longer.
Check: The same hemisphere receives more direct sunlight and more hours of sunlight.
Watch for this: Longer days are not caused by the Sun moving faster.
Now try it yourself
Why are winter days shorter?
Check your answer
The hemisphere tilts away, so the Sun's path across the sky is shorter.
Less time above the horizon means less daylight.
Judge whether an object can eclipse the Sun
Choose the method: Compare the object's apparent size with the Sun's disc.
EZT practice question
Mercury and Venus also pass between the Earth and the Sun. Why do they not cause eclipses like the Moon does?
Show the worked solution
- Mercury and Venus appear far too small against the Sun from Earth.
- They block only a tiny speck of sunlight, while the Moon is close enough to cover the Sun's disc.
Answer: Their apparent size is too small to cover the Sun, so they do not cause an eclipse like the Moon.
Check: Position in line is necessary, but the blocking body must also appear large enough.
Watch for this: Do not call every planet crossing the Sun's line a solar eclipse.
Now try it yourself
Why can the Moon cover the Sun even though it is much smaller?
Check your answer
It is much closer to Earth, so it can appear large enough.
Apparent size depends on both actual size and distance.
State the solar-eclipse safety rule
Choose the method: Treat the Sun's invisible and intense rays as dangerous even when the disc looks dim.
EZT practice question
Why must you never watch a solar eclipse with the naked eye?
Show the worked solution
- The Sun's intense light and invisible rays can permanently damage the retina.
- This risk remains even when the Sun looks partly covered or dimmed.
Answer: Looking directly at a solar eclipse can cause permanent eye damage; use proper eclipse viewers or indirect projection only.
Check: A dimmed appearance does not make direct viewing safe.
Watch for this: Sunglasses are not safe eclipse viewers.
Now try it yourself
What is a safe way to observe a solar eclipse?
Check your answer
Use certified eclipse viewers or an indirect projection method.
Both avoid looking directly at the Sun with unprotected eyes.
Explain why lunar eclipses need a full moon
Choose the method: Put the Sun, Earth and Moon in line and check which side of Earth the Moon is on.
EZT practice question
Why can a lunar eclipse happen only on a full-moon night?
Show the worked solution
- At full moon, the Moon is on the far side of the Earth from the Sun.
- That is the geometry that lets the Earth's shadow reach the Moon.
Answer: Only at full moon can the Earth come between the Sun and the Moon, so only then can its shadow fall on the Moon.
Check: The order is Sun - Earth - Moon.
Watch for this: Do not place the Moon between the Sun and Earth for a lunar eclipse; that is the solar-eclipse geometry.
Now try it yourself
Can a lunar eclipse happen on a new-moon night?
Check your answer
No.
At new moon, the Moon is on the Sun side of Earth, not inside Earth's shadow.
Explain why eclipses are not monthly
Choose the method: Add the Moon's orbital tilt to the monthly orbit.
EZT practice question
Eclipses do not happen every month, even though the Moon orbits us monthly. Why?
Show the worked solution
- The Moon's orbit is tilted relative to the Earth's orbit around the Sun.
- In most months the Sun, Earth and Moon miss perfect alignment, so the shadows pass above or below their targets.
Answer: The tilted lunar orbit means exact shadow alignment happens only sometimes, not every month.
Check: A monthly orbit gives many near alignments but only occasional exact alignments.
Watch for this: Do not assume every full moon and every new moon produces an eclipse.
Now try it yourself
What extra condition beyond full moon is needed for a lunar eclipse?
Check your answer
The Moon must pass through the Earth's shadow in near-perfect alignment.
The orbital tilt often carries it above or below the shadow.
Try a mixed set
Choose a method or explanation before opening each answer.
1. Which motion causes day and night?
Show answer and reason
Rotation.
The Earth spins on its axis about once every 24 hours.
2. Which motion works with the axis tilt to cause seasons?
Show answer and reason
Revolution.
The Earth travels around the Sun while its tilt stays pointed in the same direction.
3. Whose shadow causes a lunar eclipse?
Show answer and reason
The Earth's shadow.
The Earth comes between the Sun and the Moon.
4. Is a lunar eclipse safe to watch with the naked eye?
Show answer and reason
Yes.
You are looking at the Moon in shadow, not directly at the Sun.
Try it yourself
Work these on paper before checking any notes. Answers are deliberately not shown here.
- Rotation or revolution - which causes day and night, and which causes seasons?
- Why is the South Pole's winter during our summer?
- Name the body whose shadow causes a solar eclipse and a lunar eclipse.
- Why is a lunar eclipse safe to watch but a solar eclipse not?
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Questions about this practice page
- What is the difference between rotation and revolution?
- Rotation is the Earth spinning on its axis - about 24 hours and the cause of day and night. Revolution is the Earth orbiting the Sun - one year and, with the axis tilt, the cause of seasons.
- What causes seasons on Earth?
- The tilt of the Earth's axis combined with its revolution around the Sun. Each hemisphere gets more direct sunlight and longer days when tilted towards the Sun.
- What is a solar eclipse?
- The Moon passes between the Sun and the Earth and blocks the Sun's light. Never watch it with the naked eye.
- What is a lunar eclipse?
- The Earth's shadow falls on the Moon when the Earth comes between the Sun and the Moon. It can happen only on a full-moon night and is safe to watch.
- Are these the NCERT exercise questions for Earth, Moon, and the Sun?
- No. EZT pages are original practice on this chapter - use them to prepare for the textbook exercises, not as a substitute for your book.