What causes the phases of the moon to change in same pattern every 29 days?

Answer 1

Although the Moon orbits the Earth once every 27.3 days, keeping the same face pointing inward at all times, the Earth is going around the Sun in the same direction (counter-clockwise). So the Moon has to make more of a turn to reach the same phase (its angle with the Sun and Earth) - variations in its orbit make the phase-to-phase period between 29.18 and 29.93 days, with the average being 29.53 days, as measured by Earth-based clocks.

Answer 2

The phases of the moon change in a repeating pattern every 29 days due to the Moon's orbit around the Earth. As the Moon travels around the Earth, the angle between the Earth, Moon, and Sun changes, causing the illuminated portion of the Moon visible from Earth to vary, creating the different phases.

Answer 3

The moon, Earth, and sun are in constant motion--the moon around the Earth and the Earth around the sun. When we face the sun, we see light. When we don't face the sun, we see darkness

Add the moon into this: the moon does not have its own light--it only reflects the sun. So like Earth, it has a face of light and darkness based on the sun's position relative to it. The amount of light we see "emitting" from the moon from our vantage point on Earth is based on the moon's relative position to the sun, which is in a constant cycle. So every 29.5 days (a lunar month), we see the same phases.

Imagine a soccer ball hung in the middle of a dark room at about the level of your head. Now imagine a flashlight shining on it from the side. Half is lit up, and half is in shadow. Now imagine walking around the soccer ball. When the ball is between you and the flashlight you can only see the shaded side. When you are between the ball and the flashlight the whole ball appears to be lit up.

The soccer ball is the moon. The flashlight is the sun. You are the Earth. Of course the moon goes round the earth, but the principle is the same.

Because of the way it orbits and the angle at which it is pointing towards the sun
it goes through a cycle of phases because here from the earth we can only see the side of the moon that faces us, and on that side of the amount of sun light reflecting as the moon changes

Answer 4

A more accurate figure is 27.32 days, and the best, brief answer to the question is:

Because the moon's average distance from the earth is 238,000 miles,

and that's the way gravity works.

Answer 5

It takes a month to complete the lunar cycle, because that is how long it takes for the Moon to revolve around the Earth.

Actually, the period of revolution of the Moon is 27.32 days, but the actual total cycle is 19 some odd years because the Moon's orbit is not aligned with the plane of the ecliptic, nor is it synchronized with the Earth's revolution around the Sun.

Answer 6

The "phase" that the moon displays ... i.e. the amount of the lighted half visible to earth ...

depends on the angle between where you look to see the sun and where you look to

see the moon.

Since from our point of view the moon is circling the earth every month or so, that angle

will go through every possible value every month or so, and the phases will repeat on

the same schedule.

The moon completes a revolution around the earth every 27.32 days, but takes 29.53 days

to complete a cycle of phases. The reason for the difference is really easy to explain

if we could draw a little sketch. But W.A. doesn't store sketches, and it's really tough

to explain the difference with only words.

Answer 7

The phases of the Moon are caused by the angle between the Moon and the Sun changing. At one time we see the illuminated side, at another time, its dark side. The full cycle is 29 1/2 days.

The phases of the Moon are caused by the angle between the Moon and the Sun changing. At one time we see the illuminated side, at another time, its dark side. The full cycle is 29 1/2 days.

The phases of the Moon are caused by the angle between the Moon and the Sun changing. At one time we see the illuminated side, at another time, its dark side. The full cycle is 29 1/2 days.

The phases of the Moon are caused by the angle between the Moon and the Sun changing. At one time we see the illuminated side, at another time, its dark side. The full cycle is 29 1/2 days.

Answer 8

The phases are basically caused by the Moon revolving in its orbit around the Earth.

The motion of the Earth and Moon around the Sun has a small effect too.

So, the Moon orbits Earth in about 27.3 Earth days, but the complete phase cycle takes about 29.5 Earth days.

The Moon's rotation period is exactly equal to its orbital period.

This results in the Moon having a "day" of about 29.5 Earth days.

So, the Moon's day length is related to the phases of the Moon.

However, I wouldn't say it was the cause of the phases.

Answer 9

Because the phases of the moon are determined by its relative position to the Earth and Sun.

The cycle of phases is a bit longer than its orbital period of 27.32 days, because as the Earth orbits the Sun during that period, the moon's orbit must 'catch up' a little bit to cycle through the same geometric positions with the Earth and Sun. This accounts for the extra 1.18 days.

If the Sun and Earth where perfectly still relative to each other then the cycle of Moon phases, also called the 'synodic period', would be the same as its orbital period.

Answer 10

The phases of the Moon are caused by the angle between the Moon and the Sun changing. At one time we see the illuminated side, at another time, its dark side. The full cycle is 29 1/2 days.