Chapter 12: Earth, Moon, and the Sun
Does the Sun move, or do we? In this chapter we ride a merry-go-round to understand the Earth's rotation and the day–night cycle, watch stars wheel around the Pole Star, follow the Earth's revolution to explain changing night skies and seasons, and find out how the Moon and the Earth cast shadows to make solar and lunar eclipses.
In this chapter you will
- explain day and night through the Earth's rotation
- explain why the Sun and stars appear to move
- explain revolution, the changing night sky and seasons
- describe solar and lunar eclipses and how to view them safely
Topics
- Rotation of the Earth NCERT 12.1
The Earth rotates on its axis from West to East in about 24 hours, causing day and night.
- Revolution and Seasons NCERT 12.2
The Earth revolves around the Sun in about 365¼ days; the night sky changes through the year.
- Eclipses NCERT 12.3
Solar eclipse: Moon between Sun and Earth; never look directly at the Sun.
Key words
- Rotation
- spinning of the Earth on its axis (about 24 h)
- Revolution
- the Earth's journey around the Sun (about 365¼ days)
- Axis
- imaginary line through the poles about which the Earth spins
- Orbit
- the path of one body around another
- Solstice
- day of the longest or shortest daytime
- Solar eclipse
- the Moon blocks the Sun from part of the Earth
- Lunar eclipse
- the Earth's shadow falls on the Moon
Summary
- The Earth rotates West to East, giving day and night and the apparent motion of the Sun and stars.
- It revolves around the Sun in about 365¼ days; the night sky changes through the year.
- The tilt of the axis causes seasons, opposite in the two hemispheres.
- Solar eclipse: Moon in between; lunar eclipse: Earth in between. Never look straight at the Sun.