Page 146 - Innovator's Science-8

When you hold the ball directly opposite the lamp, you can see its entire
bright side - just like we see a full Moon in the night sky.

When you turn and face the lamp, you can see only the dark side of the ball,
similar to the new Moon day, when the Moon's bright side faces away from
Earth.
Science In between these two positions, the line dividing the bright and dark
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portions appears curved. This curved boundary looks just like the one we
Testimony
The moon is rota ng at see on the Moon during other days of the month.
the same rate that it You can now compare your observations from this activity with the actual
revolves around Earth, so
the same hemisphere phases of the Moon shown below.
faces Earth all the me.
UNDERSTANDING THE PHASES OF THE MOON

The Moon revolves around Earth once in about a month. As it moves along
its orbit, sunlight falls on it from different angles, and we see changing
shapes of its bright part from Earth.

The side of the Moon that faces the Sun is always illuminated, but from
Earth, we see only that portion which faces us.

When the Moon appears more than half bright, it is called the gibbous phase .
When less than half of its bright part is visible, it is known as the crescent

phase.
The continuous change in the visible portion of the Moon's lit side causes
the various phases of the Moon .

Moon

Science Gibbous phase Crescent phase
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Testimony
Even though the Moon
Full Moon Day New Moon
completes one orbit
Day
around. Earth in about
27.3 days, we see a full
Moon only every 29.5
days. This extra Gibbous phase Crescent phase
me—about two days—
happens because Earth
itself moves around the Half Moon
Sun during that period.
The Moon needs to travel
a li le farther to reach
the same posi on with
respect to both Earth and
The Moon at different positions in its orbit around the Earth; Each position shows a
the Sun.
different amount of its illuminated part as seen from Earth. The sequence repeats once very months.
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Science-8