The lunar cycle is how we describe the visible change of shape the Moon takes as viewed from earth. We only see the Moon at all because light from the sun is reflected directly back to us. Within a month, the moon completes one full circle around the earth. This is known as a full lunar cycle and has been tracked by humans throughout history as a way of charting the earth's movement through space, and our movements on earth.
The length of a lunation, or the moon going from phase to phase, is 29.5305882 days on average. Also known as the "synodic period," this is the period of time the orbit takes from inside our solar system. But if you're watching from outside of the solar system, the time it takes is 27.3217 days. This is known as the "sidereal period" and is two days less than the synodic period. Why are these different? Simply put, not only is the moon always moving but so is the earth. As the moon completes its cycle, the earth has also moved along its orbit of the sun, which then changes our viewing angle.
There are certain times during the year where the earth, moon, and sun actually line up. When this happens, the moon can block the sun (or at least, a part of it). This is known as a solar eclipse. A solar eclipse can only happen during the new moon phase. When the earth casts a shadow over the moon, it is known as a lunar eclipse. This can only happen during the full moon phase. While there are four to seven eclipses that happen every year, they are often partial eclipses. Total eclipses are relatively rare and are affected by where you are in the world as to how much of it you will see.
When it comes to lunar phases, you’re likely to hear references to the moon phases just as much in astrology as astronomy. For thousands of years, it has been claimed that the relationship between the moon and the earth can impact or affect human behavior on earth. These correlate with specific times of the month. For example, it’s believed that when there is a full moon that stress will be a huge factor, and people can feel overloaded with work, or preoccupied with themselves. On the other hand, a new moon is believed to bring calm to the situation, and allow for a rebalancing of people’s moods.
Far from being limited to astrology, the term lunar effect has been coined to refer to the real or imaginary impact of lunar phases on the psychological, physiological, and behavioral changes. During the 1980s, there had been over 40 published studies on the impact of the moon on mental health, and 20 which drew connections between the moon phases and birth rates in humans. Since the ‘80s, large scale studies and literature reviews have been collected to suggest there is no correlation between the lunar phases and human behavior or biology.
One of the more lingering myths around the impact of the lunar cycle on humans is that it was claimed that surgeons used to refuse to operate on patients when there was a full moon. It was believed that during this moon phase, it would prevent safe clotting from occurring. However, this was debunked by a spokesman for the Royal College of Surgeons, who said that they would "laugh their heads off" at the suggestion they could not operate on the full Moon.
The suggestion that moon phases can impact humanity has prevailed for thousands of years. The word ‘lunatic’ derives from the Latin word lunaticus, which referred to epilepsy and madness as illnesses which could be caused or induced by the moon. In our current world, analyses of mental-health data have found that the moon had a significant effect on schizophrenic patients, with one study suggesting that violent or aggressive episodes were 1.8% more likely during a full moon.
The connection between the full moon and bad behavior has long been something that law enforcement has considered. In the UK, a spokesperson for the senior police force asserted that "research carried out by us has shown a correlation between violent incidents and full moons." Meanwhile, in Ohio and Kentucky, police blamed temporary crime increases on the full moon, and even in New Zealand, the Justice Minister suggested that a series of stabbings may have been influenced or affected by the full moon.
It’s not just troublesome behavior that’s provoked by the moon. In 2013, a study at the University of Basel suggested that a lunar rhythm could modulate sleep structures and that the quality of sleep was affected by the lunar phase. Under laboratory conditions, it was found that during a full moon, humans took longer to fall asleep and slept less deeply than at other times. As a result, the endogenous melatonin levels were decreased. Professor Cajochen, who led the experiment, noted that "the lunar cycle seems to influence human sleep, even when one does not 'see' the Moon and is not aware of the actual Moon phase."
When it comes to people proving the impact of the moon on human behavior, a popular suggestion is connected to tides. The moon affects large bodies of water thanks to something known as ‘tidal force’, and given the water composition of humans, it’s possible the moon can impact this. Skeptics are quick to point out that this theory ignores the importance of scale, and the dependence of tides.
If nothing else, the lunar cycle certainly impacts humans today on a broad scale - fundamentally through the calendars of major religions. While the Gregorian calendar is used in most countries, traditional lunar calendars are often used for calculating holy days and festivals. Some examples of lunar calendar events are:
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