We explain what the phases of the Moon are and what they are, their causes and impact on various cultures from Antiquity to today.
What are the phases of the Moon?
Lunar phases or phases of the Moon are the apparent changes of the visible portion of the Moon, depending on how illuminated it is due to its position with respect to the Earth and the Sun.
These are not real changes in the nature of our only satellite, but in its relative position and its illumination, thus allowing us to observe more or less of its surface with the naked eye. To each position, thus, we give the name of a phase. Following these lunar phases, human beings have created the lunar calendar.
The phases of the Moon make up, in their entirety, a cycle of 28 days of duration that we know as lunation or lunar cycle, which goes from the total illumination of the Moon to its total occultation. It has nothing to do with lunar eclipses, although the latter can artificially reproduce certain phases.
The explanation of this lunar cycle has to do with the Moon's orbit around our planet, which ends in its entirety every four weeks. This is known as the sidereal month.
At the same time, and since the Moon lacks its own brightness, the illuminated portion of the Moon varies depending on how exposed it is to the Sun, although the face that the Moon offers us is always the same.
See also: Solar eclipse
What are the phases of the moon?
The lunar cycle is made up of eight phases, which repeat from the first to the last.
- New Moon or Black Moon In the initial stage of the cycle the part of the Moon is illuminated by the Sun, not visible from Earth. In these cases the Moon can only be observed during solar eclipses. From this phase onwards, the moon “grows” in apparent brightness.
- Crescent moon The first appearance of the Moon in the traditional sky, two days after the previous phase, is like a small scythe of light, on its right side in the northern hemisphere and its left side in the southern hemisphere. This moon can sometimes be seen during the day.
- Crescent quarter Four days after the previous phase, the Moon appears with half of its circumference illuminated and the other half in shadow (again, the illuminated half will be the right half in the northern hemisphere and the left half in the southern hemisphere). This phase can be seen at noon or midnight.
- Waxing gibbous moon The darkened half of the previous phase is gradually illuminated, as it acquires a convex shape on both sides.
- Full moon The entire lunar circle is in this illuminated phase, so we can see it in its fullness. This total appearance marks the middle of the lunar month (14 days, 18 hours, 21 minutes and 36 seconds).
- Waning gibbous moon Once the full Moon has passed, the “decrease” of the lunar brightness begins, returning to a concave appearance as it darkens.
- Last quarter A phase similar to the crescent, in which the Moon is half illuminated, only in the opposite direction. The moon can be seen in the sky during the morning hours.
- waning moon Also known as the “waxing crescent” or “old Moon”, it is similar to the crescent Moon, but in the opposite direction. It can only be seen at dawn, in the shape of a small scythe of light.
Importance of the phases of the moon
The phases of the Moon are part of the astronomical phenomena that humanity has observed since ancient times, and based on which numerous calendars have been established.
Lunar calendars were widely used by ancient cultures like the Egyptian or the Babylonian. They inspired numerous myths and legends, which offered explanations for the appearance and disappearance of the Moon. Also, its apparent coincidence with the female menstrual cycle led to the Moon being assimilated with the feminine in numerous cultures.
Thus, according to popular culture, the lunar phases could affect the growth of crops, human hair, and even the development of pregnancy and childbirth.
Continue with: Natural phenomena
References
- “Moon phase” on Wikipedia.
- “Phases of the moon” in the Argentine Naval Hydrography Service.
- “How long does each phase of the moon last?” at NASA Spaceplace.
- “The phases of the moon” (video) in Aula365.
- “Moon” in The Encyclopaedia Britannica.
