Question: What is the rotation of the Earth?

Answer: Rotation is the Earth spinning once on its axis, taking about 24 hours.

Question: What does rotation cause on Earth?

Answer: Rotation causes day and night.

Question: In which direction does the Earth rotate when viewed from the North Pole?

Answer: Counterclockwise (west to east).

Question: What is the axis of the Earth?

Answer: An imaginary line through the North and South Poles about which Earth rotates.

Question: What is the terminator?

Answer: The line dividing the day side and night side of Earth (sunrise/sunset boundary).

Question: What is revolution of the Earth?

Answer: Movement of Earth around the Sun in its orbit, taking about 365.25 days.

Question: How long does one revolution take?

Answer: Approximately 365.25 days (one year).

Question: What causes apparent movement of the Sun across the sky?

Answer: The Earth's rotation makes the Sun appear to move from east to west.

Question: Why do different places experience day and night at the same time?

Answer: Because Earth is spherical and only the half facing the Sun gets daylight while the other half is in night.

Question: What is the length of the day (approx.)?

Answer: About 24 hours.

Question: What is a solar day?

Answer: The time Earth takes to rotate so the Sun appears at the same position in the sky again — about 24 hours.

Question: Does Earth’s rotation cause seasons?

Answer: No — seasons are caused by Earth’s tilt and revolution, not rotation.

Question: What is the axial tilt of Earth?

Answer: About 23.5° to the plane of its orbit.

Question: Why do seasons occur?

Answer: Because Earth's axis is tilted, causing varying sun angles and day lengths during its revolution around the Sun.

Question: What is an equinox?

Answer: A day when day and night are nearly equal in length (around March 21 and September 23).

Question: What is a solstice?

Answer: The longest or shortest day of the year when the Sun reaches its highest or lowest point in the sky (around June 21 and December 22).

Question: Which hemisphere has summer on June 21?

Answer: Northern Hemisphere (around June 21 is summer solstice there).

Question: What happens to day length in summer?

Answer: Days are longer and nights are shorter in the hemisphere tilted toward the Sun.

Question: Name two effects of seasons.

Answer: Change in temperature and change in length of day and night.

Question: Do equator regions have large seasonal changes?

Answer: No — equatorial regions have smaller seasonal temperature variations.

Question: What is the position of Earth at summer solstice for Northern Hemisphere?

Answer: Northern Hemisphere is tilted maximally toward the Sun.

Question: When do we have spring and autumn?

Answer: Around equinoxes — spring (vernal) ~March, autumn (autumnal) ~September in the Northern Hemisphere.

Question: How long does the Moon take to revolve around Earth?

Answer: About 27.3 days (sidereal month), phases repeat in ~29.5 days (synodic month).

Question: Why do we see only one face of the Moon?

Answer: Because the Moon’s rotation period equals its revolution period (synchronous rotation).

Question: What is a new moon?

Answer: Phase when the Moon is between Earth and Sun and its near side is not illuminated (not visible).

Question: What is a full moon?

Answer: Phase when Earth is between Sun and Moon and the Moon’s near side is fully lit.

Question: Name any two intermediate moon phases.

Answer: Waxing crescent, first quarter, waxing gibbous, waning gibbous, last quarter, waning crescent.

Question: What causes the phases of the Moon?

Answer: Changing relative positions of Sun, Earth and Moon causing different portions of the Moon’s illuminated side to be visible.

Question: Is the Moon a light source?

Answer: No — the Moon reflects sunlight; it does not produce its own light.

Question: What is a lunar month?

Answer: The synodic month (~29.5 days) — time between successive same phases (e.g., full moon to full moon).

Question: When is the Moon highest in the sky during a full moon?

Answer: Around midnight (full moon rises at sunset and sets at sunrise).

Question: What is synchronous rotation?

Answer: The Moon rotates on its axis in the same time it takes to orbit Earth, showing the same face to Earth.

Question: What is a solar eclipse?

Answer: Occurs when the Moon comes between Sun and Earth and blocks Sun’s light from reaching parts of Earth (at new moon).

Question: What is a lunar eclipse?

Answer: Occurs when Earth comes between Sun and Moon and Earth’s shadow falls on the Moon (at full moon).

Question: What is the umbra?

Answer: The darkest central part of a shadow where the light source is completely blocked.

Question: What is the penumbra?

Answer: The lighter outer part of a shadow where only part of the light source is blocked.

Question: Why don’t eclipses happen every month?

Answer: Because the Moon’s orbit is tilted (~5°) to Earth’s orbital plane, so alignments are not exact each month.

Question: Which eclipse can be seen from a larger area on Earth — solar or lunar?

Answer: Lunar eclipses — they are visible from the entire night side of Earth; solar eclipses are visible from a narrow path.

Question: Name the types of solar eclipses.

Answer: Total, partial and annular solar eclipses.

Question: Why does the Moon sometimes appear red during a lunar eclipse?

Answer: Earth’s atmosphere scatters shorter wavelengths and bends red light into the umbra, colouring the Moon reddish.

Question: What causes tides?

Answer: Mainly the Moon’s gravitational pull on Earth’s oceans (Sun also affects tides).

Question: What are spring tides?

Answer: Higher high tides occurring when Sun, Earth and Moon are aligned (new or full moon).

Question: What are neap tides?

Answer: Lower high tides occurring when Sun and Moon are at right angles relative to Earth (first and last quarter).

Question: How often do spring and neap tides occur?

Answer: About every two weeks (roughly at new/full and quarter phases).

Question: How can a globe and torch be used in class?

Answer: Use torch as Sun and globe as Earth to demonstrate day–night, rotation and seasons.

Question: Define synodic month.

Answer: Time between two identical lunar phases (~29.5 days), e.g., full moon to full moon.

Question: What is the ecliptic?

Answer: The plane of Earth’s orbit around the Sun; the apparent path of the Sun on the sky lies on the ecliptic.

Question: What is a solar day vs sidereal day (short answer)?

Answer: Solar day ~24 h based on Sun’s position; sidereal day ~23 h 56 min based on distant stars.

Question: Why is Earth’s year not exactly 365 days?

Answer: Because Earth takes ~365.25 days to orbit the Sun, so extra ~0.25 days lead to leap years.

Question: Give one reason why study of Earth–Moon–Sun system is important.

Answer: Understanding these motions explains natural phenomena like day–night, seasons, tides and eclipses that affect life on Earth.