Revision Notes for Class 7 Science Chapter 12: Earth, Moon and the Sun

Quick revision notes summarizing all key concepts from Class 7 Science Chapter 12 “Earth, Moon and the Sun”. These Class 7 Science Chapter 12 notes are ideal for quick revision just before exams.

• Rotation: the Earth spins on its own axis from west to east, completing one turn in about 24 hours; this causes the cycle of day and night and makes the Sun and stars appear to move from east to west across the sky.
• Revolution: the Earth moves around the Sun in a nearly circular orbit, taking about 365 days (one year) to complete one revolution.
• The Pole Star lies almost directly above Earth’s rotational axis and so appears almost fixed in the sky, while other stars appear to circle around it through the night.
• Stars appear to rise about 4 minutes earlier each successive night, because of the Earth’s combined rotation and revolution; over a year this adds up to a full 24-hour (one-day) shift, so the same star pattern returns to the same position after about 365 days.
• Different constellations are visible at different times of year because Earth’s revolution changes which direction in space faces us at night.
• Seasons are caused by the tilt of Earth’s axis (about 23.5° to its orbital plane) combined with its revolution around the Sun — not by the Earth’s changing distance from the Sun.
• When a hemisphere is tilted towards the Sun, it has longer days, more direct sunlight, and summer; when tilted away, it has shorter days, slanting sunlight, and winter — the two hemispheres always have opposite seasons at the same time.
• At the equinoxes (around 21 March and 22/23 September), neither hemisphere is tilted towards the Sun, and day and night are close to equal (about 12 hours each) everywhere on Earth.
• Near the poles, extreme tilt effects can cause continuous daylight (“midnight Sun”) or continuous darkness for weeks at a time around the solstices.
• Solar eclipse: occurs on a new Moon day, when the Moon comes between the Sun and the Earth; the Moon’s small shadow (umbra) falls on a narrow strip of Earth, so totality is visible only briefly and from a small area; never look directly at a solar eclipse without proper eye protection.
• Lunar eclipse: occurs on a full Moon night, when the Earth comes between the Sun and the Moon; the Earth’s large shadow falls on the Moon, so it is visible from a much wider area of Earth and is safe to view with the naked eye. The Moon often looks reddish (“blood moon”) during totality due to sunlight bending through Earth’s atmosphere.
• The Moon can appear to exactly cover the much larger Sun during a total solar eclipse because apparent size depends on both actual size and distance — the Sun is about 400 times wider than the Moon but also about 400 times farther away, making their apparent sizes in the sky nearly equal.
• Because the Earth rotates west to east, places to the east experience sunrise, noon and sunset earlier than places to the west at a similar latitude.

See also: NCERT Solutions for Class 7 Science Chapter 12

Practice more: Extra Questions for Class 7 Science Chapter 12

For the full chapter list, see the Class 7 Science book page and the Class 7 Science Formulas Handbook.

Written by Satish

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