Keeping Time with the Skies
CBSE · Class 8 · Science
Summary of Keeping Time with the Skies for CBSE Class 8 Science. Key concepts, important points, and chapter overview.
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Overview
Natural cycles in the sky form the basis of timekeeping. The rotation of Earth gives the day, the phases of the Moon give the month, and Earth’s revolution around the Sun gives the year. People observed these repeating patterns and used them to create lunar calendars, solar calendars, and luni-solar
Key Concepts
The mean solar day is
The mean solar day is the average time the Sun takes to move from its highest position in the sky on one day to the highest position on the next day.
The Moon does not make its
The Moon does not make its own light. It shines by reflecting sunlight. As it revolves around Earth, different parts of its illuminated half are seen
When the bright part of
When the bright part of the Moon increases, it is the waxing period, called Shukla Paksha in India. When the bright part decreases, it is the waning p
The Moon takes about 29
The Moon takes about 29.5 days to complete one cycle of phases. Twelve lunar months make about 354 days, which is nearly 11 days shorter than the sola
Earth takes nearly 365
Earth takes nearly 365.25 days to revolve around the Sun, and this forms the basis of the solar year. Solar calendars are adjusted to keep in step wit
Learning Objectives
- Understand how the day, month, and year are linked to natural celestial cycles
- Explain the phases of the Moon and why they change
- Distinguish between lunar, solar, and luni-solar calendars
- Describe leap years and calendar adjustments in the Gregorian and Indian National calendars
- Recognise how festivals are linked to lunar and solar calendars
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Sources & Official References
- NCERT Official — ncert.nic.in
- CBSE Academic — cbseacademic.nic.in
- CBSE Official — cbse.gov.in
- National Education Policy 2020 — education.gov.in
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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