Why does the moon change its phases as the month progresses?

Answer 1

Because the relative position changes as the moon revolves around the earth. At the beginning of the lunar month, the moon is at a very low angle between the earth and the sun, showing us very little of the illuminated surface. As the month progresses, the angle increases from 0° to +90° (first quarter), then to 180° (full moon), then to -90° (last quarter), and back to 0° (new moon again).

Answer 2

because of the alignment of moon, earth, and the sun....
the moon revolves around the earth and the earth revolves around the sun, so what? the light that we see in the moon is really from the sun, when you only see a part of the moon that means that.... , argh!! it's so hard to explain by my own words so here goes some from the www.

Lunar phases are the result of our eyes seeing the illuminated half of the Moon from different viewing geometries: they are not caused by shadows of the Earth on the Moon that occur during a lunar eclipse. The Moon exhibits different phases as the relative geometry of the Sun, Earth and Moon change, appearing as a full moon when the Sun and Moon are on opposite sides of the Earth, and becoming invisible as a new moon (also named dark moon) when they are on the same side. The phases of full moon and new moon are examples of syzygies, which occur when the Earth, Moon and Sun lie (approximately) in a straight line. The time between two full moons (or between successive occurrences of the same phase) is about 29.53 days (29 days, 12 hours, 44 minutes) on average. This synodic month is longer than the time it takes the Moon to make one orbit about the Earth with respect to the fixed stars (the sidereal month), which is about 27.32 days. This difference is caused by the fact that the Earth-Moon system is orbiting about the Sun at the same time the Moon is orbiting about the Earth. The actual time between two syzygies is variable because the orbit of the Moon is elliptic and subject to various periodic perturbations, which change the velocity of the Moon.

Answer 3

When the moon is full you're looking at its day side--the earth is largely between the moon and sun.

When the moon is new, you see mostly its night side--the moon is between the earth and sun.

The terminator divides the lunar day from the lunar night. As the moon revolves around the earth, our view of the terminator sweeps across the moon (waxing), until the moon is largely in broad daylight from our perspective. Then the moon swings back towards earth's sun side, the daylit side wanes.

The moon would appear to wax and wane to us at the same rate regardless of how fast it rotated. But as it is tidally locked (always faces us with the same side), the lunar month and day are about the same length--just under 28 days.

Answer 4

The moon goes around the earth in 28 days.

Answer 5

I'ts all about triangles. The moon only goes around the earth once every 28 days and the earth spins once a day. Just imagine your above the rotational plane of the moon and visualize it.

Answer 6

as the moon goes through its orbit around earth, earths blocks the sun which in turns created the phases...darkness is earth shadow on the moon.... depending on where the moon on its orbit, don't for get its is not a perfect circle obit it is elliptical....

Answer 7

because of the shadow of the earth moving across the surface of the moon as it changes position during its orbit.