Lunar Phases and Eclipses

What causes the Moon to always show the same side to Earth?

• The Moon's orbit is elliptical.

• The Earth's gravity locks the Moon in place.

• The Moon does not rotate.

• The Moon's rotation period matches its orbit around Earth.

Answer explanation

The Moon's rotation period matches its orbit around Earth, resulting in synchronous rotation. This means it takes the same time to rotate on its axis as it does to orbit Earth, causing the same side to always face us.

What is the primary reason the Moon appears to change shape throughout the month?

• The Sun's light intensity varies.

• The Earth's shadow covers the Moon.

• The Moon's surface changes.

• The Moon orbits Earth, changing the view of its sunlit side.

Answer explanation

The Moon appears to change shape because it orbits Earth, which alters our view of its sunlit side. This is why we see different phases of the Moon throughout the month.

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NGSS.MS-ESS1-1

Which phase occurs when the Moon is between the Earth and the Sun?

• Waning Gibbous

• New Moon

• Full Moon

• First Quarter

Answer explanation

The New Moon phase occurs when the Moon is positioned between the Earth and the Sun, making it invisible from Earth. This is why the correct answer is New Moon.

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NGSS.MS-ESS1-1

How often does the lunar phase cycle repeat?

• Every 15 days

• Every 29.5 days

• Every 45 days

• Every 60 days

Answer explanation

The lunar phase cycle, known as the synodic month, takes about 29.5 days to complete. This is the time it takes for the Moon to return to the same phase, making 'Every 29.5 days' the correct answer.

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What is a total lunar eclipse?

• When the Moon passes directly between the Earth and the Sun.

• When the Moon is partially covered by Earth's shadow.

• When the Moon is closest to Earth.

• When the Moon is completely covered by Earth's shadow.

Answer explanation

A total lunar eclipse occurs when the Earth passes directly between the Sun and the Moon, causing the Earth's shadow to completely cover the Moon. This is why the correct answer is when the Moon is completely covered by Earth's shadow.

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NGSS.MS-ESS1-1

Why don't lunar eclipses occur every month?

• The Sun's position changes too frequently.

• The Moon's orbit is tilted relative to Earth's orbit around the Sun.

• The Moon's surface is uneven.

• The Earth's orbit is elliptical.

Answer explanation

Lunar eclipses don't occur every month because the Moon's orbit is tilted about 5 degrees relative to Earth's orbit around the Sun. This tilt means that the Earth, Moon, and Sun don't always align perfectly for an eclipse.

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NGSS.MS-ESS1-1

What color does the Moon appear during a total lunar eclipse?

• Green

• Blue

• Yellow

• Red

Answer explanation

During a total lunar eclipse, the Earth blocks sunlight from directly reaching the Moon. The refracted light through the Earth's atmosphere gives the Moon a reddish hue, often referred to as a 'blood moon', making red the correct answer.

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What is the umbra?

• The lightest part of Earth's shadow.

• The shadow of the Moon.

• The central, darkest part of Earth's shadow.

• The outer shadow of the Earth.

Answer explanation

The umbra is the central, darkest part of Earth's shadow, where light is completely blocked. This distinguishes it from the penumbra, which is the lighter outer part of the shadow.

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What is the phase called when the Moon is fully illuminated as seen from Earth?

• Full Moon

• New Moon

• Waning Crescent

• First Quarter

Answer explanation

The phase when the Moon is fully illuminated as seen from Earth is called the Full Moon. During this phase, the entire face of the Moon is lit by the Sun, making it appear bright and round.

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What happens to a solar-powered spacecraft during a lunar eclipse?

• It gains speed.

• It loses power as it falls into Earth's shadow.

• It is unaffected.

• It receives more power.

Answer explanation

During a lunar eclipse, the Earth blocks sunlight from reaching the spacecraft, causing it to lose power as it falls into Earth's shadow. This makes the correct answer "It loses power as it falls into Earth's shadow."

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