Why are there full moons?

Have you ever wondered why the moon changes its appearance every night? Some evenings it shines round and bright in the night sky, while other times it appears to be just a thin crescent. These variations in shape, known as lunar phases, are in reality a marvelous space ballet orchestrated by the Earth, the Moon and the Sun. Let’s dive together into the mysteries of the moon and discover why there are full moons.

A lunar cycle that punctuates our calendar

The lunar cycle, also called moon calendar, is a time measurement system based on the phases of the Moon. It is fundamental to understanding the appearance of full moons.

During a lunar month, approximately 29.5 days, the Moon goes through different phases, ranging from new moon to full moon, including the quarter moon. Each phase corresponds to a precise position of the Moon in relation to the Earth and the Sun.

There new Moon is the first phase of the lunar cycle. This is the time when the Moon is aligned between the Earth and the Sun. The illuminated side of the Moon then faces the Sun, and the dark side faces the Earth. From our point of view on Earth, the Moon is therefore invisible.

From new moon to full moon: a journey through space

After the new moon, the Moon begins to move along its orbit around the Earth. As it moves away from the new moon position, a thin portion of the illuminated side of the Moon becomes visible from Earth. It’s the first quarter from the moon.

As the days go by, this portion gradually enlarges until the Moon reaches the full moon, about two weeks after the new moon. At the time of the full moon, the Moon and the Sun are on opposite sides of the Earth. The illuminated face of the Moon is then entirely visible from Earth. The Moon therefore appears as a complete luminous disk in the night sky. This is the phase we all know as the “full moon”.

The effects of the full moon: myths and realities

Full moons have always fascinated men, giving rise to numerous myths and beliefs. Some people believe that the full moon can influence our behavior or our sleep, while others attribute phenomena such as increased childbirth or acts of madness to the full moon.

Science, however, remains skeptical. Although some studies have attempted to link the full moon to these phenomena, none have provided solid evidence. However, the full moon has an undeniable impact on the tides terrestrial. When full or new, the Moon, in combination with the Sun, causes stronger tides, called “spring tides.”

The Moon, the Sun and eclipses

Finally, the positioning of the Moon, Earth and Sun during the full moon is also the cause of lunar eclipses. A lunar eclipse occurs when the Earth is between the Sun and the Moon, thus casting its shadow on the Moon.

Unlike a solar eclipse, a lunar eclipse can be observed from any location on Earth where the Moon is visible. The spectacle is all the more fascinating as the Moon can take on a reddish tint, earning it the nickname “Blood Moon”.

In short, the full moon is the result of a cosmic dance between the Earth, the Moon and the Sun. A celestial ballet that punctuates our nights and continues to fuel our dreams and our imagination.

The lunar calendar and human history

Since the dawn of time, human beings have looked to the sky to navigate and mark the passage of time. THE moon calendar, with its regular phases, became a valuable tool for our ancestors.

Early civilizations often based their calendars on the phases of the moon. This was the case for the Mesopotamians, the Maya, the Chinese, the Romans and many other peoples. Their lunar calendars were essential for determining the seasons, planning harvests, and even predicting eclipses.

For example, the Hebrew calendar, which is still in use today, is a mixture of the solar and lunar calendars. He uses the new Moon to mark the beginning of each month, and interposes a thirteenth month every two to three years to synchronize with the solar year.

In some cultures, each full moon of the year even has a specific name, which often reflects seasonal changes. Thus, the “Strawberry Moon” in June signals the time to harvest strawberries, while the “Harvest Moon” in September indicates harvest time.

The tradition of naming full moons has continued to this day. In the modern lunar calendar, each full moon has a name that reflects the seasons or other natural phenomena.

Full moons and popular culture

If the full moons fascinate scientists, they have also inspired artists and nourished our popular culture. They are present in the tales and legends of all cultures, often associated with magic, metamorphoses, and madness.

Full moons are found in many folk and religious traditions. For example, in Buddhism, the full moon is an auspicious time for meditation and contemplation. In Islam, the new Moon marks the start of each month of the Muslim lunar calendar, including the month of Ramadan.

Full moons also have their place in literature, cinema and music. Who has never heard of the werewolf who transforms at the full moon, or of the “moonlight” that has inspired so many poems and songs?

In the world of science fiction, full moons often play an important role. For example, in the “Star Wars” saga, the planet Endor, populated by Ewoks, is actually a moon. In the series “Doctor Who”, the Moon is revealed to be a cosmic dragon egg about to hatch.


The Moon, our closest neighbor in the cosmos, continues to fascinate and inspire us. Its regular dance with the Sun creates a celestial spectacle that punctuates our nights and our lives. The different lunar phases, from first quarter to full moon, have been used to measure time since ancient times.

Despite advances in science astronomy, the mystery and beauty of the Moon continues to captivate our imagination. Whether through the myths and legends linked to the full moon, the beliefs about its effects on our behavior, or simply the contemplation of its silvery light on a full moon evening, our link with this star remains strong and alive.

Beyond its influence on tides or the triggering of eclipses, the Moon has a profound cultural and historical impact. She inspired humanity to dream, to explore, and to seek to understand the universe around us. At each full moon, let’s take a moment to admire this celestial spectacle and to appreciate the wonders of our universe.