Earth, Moon & the Sun | Science Grade 7 CBSE

Play with it

A month of moons

Drag through the 29.5-day lunar month. The big disc is the Moon as you see it from Earth; the inset shows where it is in its orbit and which half the Sun is lighting.

Explore · Moon-phase labdrag the slider

Day of the lunar month 1

Learn

The three big ideas

The Earth rotates on its axis once every ~24 hours — the side facing the Sun has day, the far side has night.
The Earth revolves around the Sun once every ~365¼ days — that is one year.
The Sun is a star — it makes its own light; the Earth and Moon only reflect it.

The Moon makes no light of its own — the Sun always lights up one half of it. As the Moon orbits the Earth (~29.5 days), we see different amounts of that sunlit half:

New moon → the lit half faces away; we see (almost) nothing.
Waxing (growing) → crescent → first quarter → gibbous → full moon.
Waning (shrinking) → gibbous → last quarter → crescent → back to new.

Common mistake: phases are not the Earth's shadow on the Moon. That's a lunar eclipse. Phases just depend on how much of the sunlit Moon faces us — use the explorer above to see it.

Worked example. Tonight the Moon is a thin crescent lit on the right, and it has grown a little each night. Is it waxing or waning, and what comes next?

Growing + lit on the right ⇒ waxing crescent. Next comes the first quarter (right half lit), then a gibbous moon, then the full moon.

An eclipse happens when the Sun, Earth and Moon line up so one casts a shadow on another:

Solar eclipse — the Moon comes between the Sun and the Earth (at new moon) and blocks the Sun. Never look at the Sun directly.
Lunar eclipse — the Earth comes between the Sun and the Moon (at full moon), and the Earth's shadow falls on the Moon.

Where you'll meet it

The Moon runs our calendars

Months & festivals

The ~29.5-day phase cycle is where the "month" comes from. Many festivals — Eid, Diwali, Holi, Karva Chauth — are set by the Moon's phase, which is why their dates shift each year.

Tides & timing

The Moon's pull raises ocean tides, strongest near new and full moon. Sailors and fishers have read the Moon's phase for safe timing for thousands of years.

Check yourself

Competency quiz

Modelled on the competency-based pattern — MCQ, assertion–reason and a case study, testing whether you can use the ideas, not just recall them.

Score 0/12

Earth, Moon& the Sun