Earth, Moon and the Sun — NCERT Class 7: quick revision, 15 bites

The Sun is the Source of All Light and Heat

Everything on Earth runs on sunlight.

The Sun is a star at the centre of our solar system. It provides the **light and heat** that make life possible on Earth.

Takeaway. Without the Sun, there would be no light, heat, or life on Earth.

Earth, Moon and Sun: Key Terms

Know these three players first.

Takeaway. Earth revolves around the Sun; the Moon revolves around Earth.

The Moon Has No Light of Its Own

The Moon is a cosmic mirror.

The Moon does **not** produce its own light. We see it because it **reflects sunlight**.

Takeaway. Moonlight is actually reflected sunlight.

Why the Moon Shows Phases

Same Moon, different faces every night.

The Moon revolves around Earth, so the portion of its sunlit half that faces us changes. This cycle creates the **phases of the Moon**.

Takeaway. Moon phases are caused by the Moon's revolution around Earth, not by Earth's shadow.

Phases Are NOT Caused by Earth's Shadow

Don't confuse phases with eclipses.

Takeaway. Phases = changing view of the lit half. Eclipse = shadow blocking light.

Solar Eclipse vs Lunar Eclipse

Two eclipses, two very different shadows.

Takeaway. Solar eclipse = Moon in front of Sun. Lunar eclipse = Earth in front of Moon.

The Moon Takes 27.3 Days to Orbit Earth

One lap around Earth, one month.

Takeaway. The Moon's rotation and revolution are synchronised — we always see the same face.

Why We Always See the Same Side of the Moon

The far side is not the dark side.

The Moon rotates on its axis in the same time it takes to revolve around Earth. So the same face always points toward us.

Takeaway. The far side of the Moon is hidden from Earth, not from the Sun.

Day and Night on Earth

Earth spins, and the sky changes.

Takeaway. Day and night are caused by Earth's rotation, not by the Sun moving around Earth.

The Sun Does Not Move Across the Sky

It looks like it moves — it doesn't.

Takeaway. Apparent motion of the Sun is due to Earth's rotation.

The Moon Has No Atmosphere or Water

A world without air or oceans.

Takeaway. The Moon is a barren, airless world — very different from Earth.

Exam Tip: Order the Eclipse Line-Up

Sun-Moon-Earth or Sun-Earth-Moon?

Takeaway. Remember the middle body: Moon in the middle = solar; Earth in the middle = lunar.

Memory Trick: 'SME' and 'SEM'

Two three-letter codes to lock it in.

Takeaway. Use SME and SEM to never mix up eclipse order.

Why the Moon Looks Bigger Near the Horizon

A trick of the eye, not the sky.

The Moon appears larger near the horizon than high in the sky, but its actual size does not change. This is an optical illusion caused by how our brain compares it with objects on the ground.

Takeaway. The 'big Moon' near the horizon is an illusion, not a real change in size.

The Moon Is About 3,84,400 km Away

That's a long way for moonlight.

Takeaway. The Moon is close enough that its reflected light reaches us in just over a second.