Meaning of Moon Phases

What is Moon Phases:

The phases of the Moon are the changes that occur on the visible face of the natural satellite during a lunar cycle, in which variations can be seen in its illuminated portions.

These changes occur as the Moon rotates on itself and makes its movement of translation. The different positions it occupies with respect to the Earth and the Sun are what cause the changes in lighting.

moon cycle

A lunar cycle is a period in which all phases of the Moon occur. It is also known as synodic month and lasts 29.5 days.

The Earth makes its translation movement around the Sun, and by the effect of gravity, it brings the Moon with it.

However, it takes the Moon a little more than one revolution to reach the same position with respect to the Earth and the Sun. So it takes 28 days to complete the revolution around the planet (sidereal month) and one and a half days more to reach to the Sun (synodic month).

During the lunar translation, there are 4 phases known as the new Moon, the first quarter, the full Moon and the last quarter. Each of them lasts approximately 7.4 days.

Moon phases

New Moon

It is the beginning of a new lunar cycle, hence the name of this phase. It is also known as a black moon or astronomical new moon.

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In this part of the cycle, the satellite travels from 0 to 45 degrees of its orbit and cannot be seen from Earth, since the Sun is illuminating the lunar face that cannot be seen from the planet, while the glow hides the side that is visible.

Illumination in this phase is 0 to 2 percent.

Crescent moon

Three or four days after the new Moon, the waxing Moon begins. It is called like this because the illuminated portion grows with the passing of days. The part visible from Earth is shaped like a horn, and is seen from the right side in the northern hemisphere, and from the left side in the southern hemisphere.

In this time, the satellite travels between 45 and 90 degrees of its orbit. This is the part of the cycle in which the Moon can be seen during the day and at the beginning of the evening.

Illumination in this phase can reach up to 23 percent.

first quarter

Four days after the waxing Moon, the first quarter occurs. In this phase, it is already possible to distinguish 50 percent of the lunar face that is visible from Earth, illuminated by the Sun, while the satellite travels between 90 and 135 degrees of its orbit.

In the northern hemisphere, the right portion is illuminated, while the left remains dark. For its part, in the southern hemisphere the opposite occurs, and it is the left side that can be seen illuminated.

full moon

Also called a full moon, it occurs when the Moon, Earth, and Sun are almost in a straight line, causing the lunar side visible from the planet to be fully illuminated, so it appears as a complete circle from the planet.

It can be seen from sunset to sunrise, and during midnight it reaches its maximum height. During this period, the moon travels up to 180 degrees of its orbit.

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The illuminated portion is 96 percent.

last quarter

From this phase, the Moon is about to complete its cycle. The last quarter is exactly like the first quarter, only in this case, the portion that is illuminated in the northern hemisphere is the left. And in the southern hemisphere, it’s the right.

The luminosity of the visible portion of the moon during this period progressively decreases from 65 percent to 35 percent.

waning moon

As during the crescent Moon, in the waning Moon the visible part is leather-shaped, only this time it is seen from the left side in the northern hemisphere, and from the right side in the southern hemisphere.

During these days, the illumination decreases up to 3 percent.

gibbous moons

Before the full Moon, the illuminated portion (which until then appears straight) begins to take on a convex shape. This is called a waxing gibbous moon.

After the full Moon, the illuminated part begins to decrease progressively, taking a concave shape. It is called the waning gibbous moon.