NCERT Class 7 Science Chapter 12
Earth, Moon and the Sun
This chapter introduces CBSE Class 7 students to the structure and movements of the Earth, Moon, and Sun, and their effects on phenomena like day and night, seasons, and lunar phases. Students learn about the rotation and revolution of the Earth, the Moon's orbit around the Earth, solar and lunar eclipses, and the reason for different phases of the Moon. The chapter connects astronomy to everyday observations.
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Key Terms
- Rotation
- The spinning of the Earth on its own axis, which takes approximately 24 hours (one day) and causes the cycle of day and night.
- Revolution
- The movement of the Earth around the Sun in an elliptical orbit, which takes approximately 365.25 days (one year) and causes the seasons.
- Lunar Phases
- The different shapes of the Moon as seen from Earth throughout the month, caused by the changing relative positions of the Earth, Moon, and Sun. The cycle includes new moon, crescent, quarter, gibbous, and full moon.
- Solar Eclipse
- A celestial event that occurs when the Moon comes between the Earth and the Sun, blocking sunlight and casting a shadow on part of the Earth.
- Lunar Eclipse
- A celestial event that occurs when the Earth comes between the Sun and the Moon, casting its shadow on the Moon, causing it to appear dark or reddish.
- Axis of the Earth
- An imaginary line passing through the North and South Poles around which the Earth rotates. The Earth's axis is tilted at 23.5 degrees, which is responsible for the seasons.
Frequently Asked Questions
What causes day and night on Earth?▾
Day and night are caused by the rotation of the Earth on its own axis from west to east. The side of the Earth facing the Sun experiences day, while the side facing away from the Sun experiences night. The Earth completes one full rotation in approximately 24 hours.
What causes the seasons on Earth?▾
Seasons are caused by the revolution of the Earth around the Sun and the tilt of the Earth's axis (23.5 degrees). When a hemisphere is tilted toward the Sun, it receives more direct sunlight and experiences summer. When tilted away, it receives less sunlight and experiences winter.
What are the phases of the Moon?▾
The Moon's phases occur as it orbits the Earth over about 29.5 days. The phases are: New Moon (not visible), Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent. The phases depend on how much of the sunlit side of the Moon faces the Earth.
What is the difference between a solar eclipse and a lunar eclipse?▾
A solar eclipse occurs when the Moon passes between the Earth and the Sun, blocking sunlight from reaching part of the Earth. A lunar eclipse occurs when the Earth passes between the Sun and the Moon, casting Earth's shadow on the Moon.
Why does the Moon appear to change shape every night?▾
The Moon does not actually change shape. Its apparent shape changes because as it orbits the Earth, we see different portions of its sunlit half. When the Moon is between the Earth and Sun, we see none of the lit side (new moon). When Earth is between the Sun and Moon, we see the entire lit side (full moon).
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