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Our Universe - Phases of the Moon

Grade 5ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The Moon is the Earth's only natural satellite and does not have its own light; it shines by reflecting the light of the Sun.

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The Moon revolves around the Earth in a fixed orbit. It takes approximately 27.327.3 days to complete one revolution and the same amount of time to complete one rotation on its axis.

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Phases of the Moon are the different shapes of the lit portion of the Moon as seen from Earth, caused by the changing positions of the Sun, Moon, and Earth.

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The cycle from one New Moon to the next takes approximately 29.529.5 days, which is known as a lunar month.

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Waxing refers to the period where the visible lit portion of the Moon is increasing (from New Moon to Full Moon).

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Waning refers to the period where the visible lit portion of the Moon is decreasing (from Full Moon to New Moon).

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The main phases include: New Moon→Waxing Crescent→First Quarter→Waxing Gibbous→Full Moon→Waning Gibbous→Last Quarter→Waning Crescent\text{New Moon} \rightarrow \text{Waxing Crescent} \rightarrow \text{First Quarter} \rightarrow \text{Waxing Gibbous} \rightarrow \text{Full Moon} \rightarrow \text{Waning Gibbous} \rightarrow \text{Last Quarter} \rightarrow \text{Waning Crescent}.

📐Formulae

Duration of one Lunar Cycle≈29.5 days\text{Duration of one Lunar Cycle} \approx 29.5 \text{ days}

Time from New Moon to Full Moon≈29.52≈14.75 days\text{Time from New Moon to Full Moon} \approx \frac{29.5}{2} \approx 14.75 \text{ days}

Average distance from Earth to Moon≈384,400 km\text{Average distance from Earth to Moon} \approx 384,400 \text{ km}

💡Examples

Problem 1:

If a Full Moon is observed on the 1st1^{st} of a month, approximately on what date will the New Moon occur?

Solution:

The New Moon will occur approximately on the 15th15^{th} or 16th16^{th} of the same month.

Explanation:

Since a complete lunar cycle (Full Moon to Full Moon) is about 29.529.5 days, the time taken to reach the New Moon (half a cycle) is approximately 29.52≈14.75\frac{29.5}{2} \approx 14.75 days. Therefore, 1+14.75≈15.751 + 14.75 \approx 15.75 days.

Problem 2:

During which phase is the Moon positioned between the Sun and the Earth?

Solution:

The New Moon\text{New Moon} phase.

Explanation:

During the New Moon\text{New Moon}, the side of the Moon facing the Earth receives no sunlight, making it invisible to us because the Moon is located between the Earth and the Sun.