NCERT Curiosity · Class 7 · Science
Earth, Moon, and the Sun
In Kanniyakumari, Rashmika noticed the coconut trees' shadows were long in the morning, short by afternoon. Does the Sun move — or does the Earth?
Key idea
The Rotation of the Earth
Like a merry-go-round rider seeing the world seem to spin the opposite way, the Sun appears to move across our sky because the Earth itself is spinning.
The Earth spins on its axis — an imaginary line through the North and South Poles — completing one full turn about every 24 hours, West to East.
Key idea
Day and Night
1
Half lit, half dark
The half of Earth facing the Sun has daytime; the other half has night.
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2
East to West
Because Earth spins West to East, the Sun (and Moon and stars) appear to rise in the East and set in the West.
Key idea
Why the Pole Star Stays Put
1
Pointing at a fixed spot
Earth's axis points almost exactly at the Pole Star, so it appears nearly stationary while other stars circle around it — captured in long-exposure photos as star trails.
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2
Aryabhata's insight
This ancient Indian astronomer described this apparent motion and calculated Earth's rotation period remarkably close to today's accepted value.
Key idea
The Revolution of the Earth
Revolution is the motion of an object around anotherthe path it follows is called its orbit.
One trip, ~365¼ daysThe Earth revolves around the Sun in a nearly circular orbit — and as it does, the stars visible after sunset gradually change through the year.
Key idea
What Really Causes the Seasons
1
A tilted axis
Earth's axis stays tilted throughout its orbit. In June, the Northern Hemisphere tilts toward the Sun (summer); in December, it tilts away (winter).
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2
Not about distance
Earth is actually closest to the Sun in January — the tilt and shape of the Earth cause seasons, not distance.
Key idea
Solstices and Equinoxes
Event | Around | What happens
Summer solstice21 June — Longest day in the Northern Hemisphere
Winter solstice22 December — Shortest day in the Northern Hemisphere
Equinoxes21 March, 23 September — Day and night each about 12 hours
Key idea
Solar Eclipse
Same apparent size, different distance. The Moon is far smaller than the Sun, but also far closer to Earth — so it can appear to just cover the Sun completely.
Key idea
Total and Partial Solar Eclipses
1
Total vs partial
A total eclipse fully blocks the Sun in a small area; a partial eclipse blocks only part of it over a wider area.
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2
Safety first
Never look directly at the Sun during an eclipse, even with sunglasses or binoculars — use proper eclipse-viewing methods, like a mirror projection.
Key idea
Lunar Eclipse
Safe to watch. Earth's shadow falls on the Moon — this is completely safe to view directly with the naked eye.
Key idea
Solar vs Lunar Eclipse
| Solar eclipse | Lunar eclipse
What blocks whatMoon blocks the Sun — Earth's shadow falls on the Moon
Visible fromA small area on Earth — A large part of Earth's night side
Safe to view directly?No — Yes
Chapter · Key terms to remember
Key Terms
Rotation
Earth spinning on its own axis (~24 hours).
Axis of rotation
The imaginary line through the poles.
Revolution
Earth's motion around the Sun (~365¼ days).
Chapter · Key terms to remember
More Key Terms
Orbit
The path followed while revolving.
Solstice
Day of longest or shortest daylight.
Equinox
Day when daytime and night are equal.
Chapter · Key terms to remember
More Key Terms
Solar eclipse
Moon blocks sunlight from reaching Earth.
Lunar eclipse
Earth blocks sunlight from reaching the Moon.
Questions for your notebook
Write these down, then discuss
1During one Earth rotation, how many hours of sunlight do the North Pole and South Pole each receive?
2Fill in the blanks: (i) Stars rise in the ___ and set in the ___. (ii) Day and night are caused by Earth's ___. (iii) When the Moon fully covers the Sun, it's called a ___ solar eclipse.
3Padmashree saw Orion nearly overhead at 8 pm yesterday. When will she see it overhead today?
Project as-is — students copy the questions, then the class discusses answers together.