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Moon Width

3,474 kilometers (2,159 miles).

Sunlit Side of the Moon

A little less than half of the Moon faces the Sun at any given time.

Moon Shape

The shape of the Moon as it appears from Earth is referred to as its phase.

Terminater

The dividing line between the lit and unlit sides of the Moon

Lunar Orbit Duration

27.3 days.

Lunar Phases Duration

29.5 days.

Perigee

The part of the Moon's cycle when it is closest to the Sun

Growing Moon

waxing.

Moon's Position Change

As the Moon orbits the Earth, it moves slightly to the east every day.

First Quarter Appearance

a half-circle.

Full Moon

The phase of the Moon when it rises at sunset and sets at sunrise

Waning Moon

The term used when the Moon is viewed as shrinking

Waning Gibbous

The phase that comes a week after the Full Moon

Earthshine

The light that reflects from the Earth onto the Moon

Moon Phase Definition

what the Moon looks like from Earth at a particular time.

Full Moon Frequency

about once a month.

Moon's Motion

in a circular orbit around the Earth.

Earth's Motion

The Earth rotates on its axis, a straight line connecting the North Pole to the South Pole.

Moon's Positioning Reason

We see phases of the Moon because its position around the Earth changes relative to the Sun.

Illuminated Side of a Waxing Moon

The right side

Illuminated Side of a Waning Moon

The left side

Crescent Moon Identification

Determine if a crescent Moon is waxing or waning by its position (right = waxing, left = waning).

Moon Side Visibility

We always see the same side of the Moon because its rotation period is the same as its orbit around Earth.

Synchronization of Moon's Motion

The Moon takes about 30 days to orbit the Earth and to rotate once on its axis.

Rotation and Orbit Comparison

The time intervals for the Moon's rotation and orbit are the same, about 30 days.

How much of the Moon faces the sun?

half

Which word refers to the shape of the Moon, as it appears to us?

phase.

The Moon orbits the Earth roughly once per _____________

27.3 days.

Words that have similar etymological histories, like 'month' and 'Moon' are ____________

cognates.

What is the length of time for the Moon to go through all its phases?

29.5 days.

Which term means 'growing or getting bigger'?

waxing.

Because the Moon is orbiting the Earth, after a couple of days it’s moved a bit to the _____

east

Which term means 'swollen or convex'?

gibbous.

Which phase comes a week after full moon?

waning gibbous.