Why does moon phases

The Moon takes as much time to rotate once on its axis as it takes to complete one orbit of Earth. Both are about In other words, the Moon rotates enough each day to compensate for the angle it sweeps out in its orbit around Earth.

Gravitational forces between Earth and the Moon drain the pair of their rotational energy. We see the effect of the Moon in the ocean tides. Likewise, Earth's gravity creates a detectable bulge -- a foot land tide -- on the Moon. Eons from now, the same sides of Earth and Moon may forever face each other, as if dancing hand in hand, though the Sun may balloon into a red giant, destroying Earth and the Moon, before this happens.

There is no real formula for determining the visibility of the young Moon. It depends on several factors: the angle of the ecliptic the Moon's path across the sky with respect to the horizon, the clarity of the sky how much dust and pollution gunks it up , and even the keenness of the observer's eyesight. The young Moon becomes visible to the unaided eye much earlier at times when the ecliptic is perpendicular to the horizon, and the Moon pops straight up into the sky.

In these cases, it may be possible to see the Moon as little as 24 hours after it was new, although every hour beyond that greatly increases the chances of spotting it. When the ecliptic is at a low angle to the horizon, and the Moon moves almost parallel to the horizon as it rises, the Moon probably doesn't become visible until at least 36 hours past new. The relative positions of our Sun, Earth, and Moon, cause these changes.

As our Moon orbits around Earth, the side facing the Sun is always illuminated, just like Earth's daylight side is illuminated by the Sun. What we see from Earth , however, is a different story. From Earth, the Moon's surface looks dark because the illuminated side is facing away from Earth. Between the new and full Moon, the amount of Moon we see grows — or waxes from its right side toward its left side.

As it passes the full Moon stage, the amount of illumination decreases — or wanes — from right to left. Finally, the Moon returns to its position between the Earth and the Sun, and on Earth we observe the new Moon again. In the southern hemisphere, illumination of the Moon increases from the left to the right side in the waxing phase and the dark part increases in coverage from left to right in the waning phase, which is opposite of the northern hemisphere.

No matter where on Earth an observer is, however, the phases of the Moon occur at the same time. What causes a lunar eclipse? Pictures of the Moon's phases often make it look like there should be a lunar eclipse during each full Moon and a solar eclipse during each new Moon. However, two things have to happen for a full lunar eclipse. First, the Moon has to be full, so there is only an opportunity for a lunar eclipse about once each month.

This elliptical orbit, combined with the phases is also what leads to the appearance of a so-called supermoon. In this phase, our satellite is invisible. The morning terminator starts its creep of In this phase, the Moon rises at noon and sets at midnight. Along the terminator, low-angled sunlight creates long shadows, throwing nearby crater and mountains into sharp relief — perfect for lunar observations. In this phase the Moon is almost fully illuminated.

The daylight area appears egg-shaped gibbous and is increasing in size waxing daily. The sunlit, egg-shaped area is diminishing waning. But why does the moon have phases at all? To answer this question, it's necessary to understand two important facts.

First of all, the moon revolves around the Earth once every And secondly, as the moon carries out its voyage around the planet, it's lit from varying angles by the sun. One half of the moon is always illuminated by the sun. But here on Earth, we can't always see the half of the moon that's lit up.