The fascination of the full moon in 5 points What is fantasy and what is fact?

People have been fascinated by the night sky for thousands of years. The moon has shaped our sense of time and inspired imagination and art. But it still has its secrets. Putting the full moon to the test.

DPA

30.04.2025, 13:53

dpa

The history of language reveals a lot about this: "Lunatic", for example, means a madman in English. The term goes back to the Latin word "luna" for moon. It reflects a popular belief that was widespread in the Middle Ages: according to this belief, the celestial body had an influence on feelings and behavior.

In German, the word "Laune" has survived. Beethoven's Moonlight Sonata or Matthias Claudius' poem "The moon has risen" sound clearly emotional. From a scientific point of view, however, there are not only facts but also puzzles as to whether the moon can really charm us.

Swiss chronobiologist Christian Cajochen studies the human internal clock at the University of Basel, for example with regard to shift work.

"But when it comes to the moon and sleep, many researchers are rather reserved," he says. Just setting up a serious study in the sleep lab is difficult as soon as volunteers know that it's about the moon. "This immediately has a psychological impact and can distort the results," says Cajochen to the German Press Agency (dpa).

At Cajochen's institute, a full moon effect emerged in retrospect from a study that was actually about Alzheimer's disease. Healthy people spent the night as a control group in an isolated laboratory.

A look at the data showed that the test subjects were more active in the evening during a full moon and fell asleep less easily. The result surprised Cajochen, who has no esoteric inclinations and would have preferred to disprove a popular belief. His ambivalence made him hesitate before publishing the findings in 2013.

"There was huge media interest and very little scientific interest," he says with a grin. In 2021, a US study comparing the influence of the moon on people in rural Argentina, some without electricity, with students in the large city of Seattle produced almost identical results. However, other studies found no such effects.

"It's still a mystery," summarizes Cajochen. "From a strictly scientific point of view, you would have to observe the same people for two whole months under laboratory conditions to find out whether they really have inner moon clocks." Circalunar is the scientific term for this. Researchers have already proven such clocks for some animal species. Proving it for humans remains difficult. "There would probably be a lack of volunteers and money for a study," says Cajochen. And even then, there would probably not automatically be an explanation for the observations.

The influence of the celestial body on the calendar is easier to explain: The moon is already in the word month. It takes about 28 days for it to orbit the earth. This was the basis for the original division of the months in many calendars.

With the Romans and refined in the Gregorian calendar at the end of the 16th century, the solar year became established: According to this, most months have 30 or 31 days.

However, the date of Easter remains linked to the Earth's satellite: It falls on the first Sunday after the ecclesiastically defined spring full moon - and can therefore be earlier or later in the year. If a Christian church does not calculate according to the Gregorian calendar, the celebration is postponed even further.

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Many planets in our solar system have cosmic companions. However, according to current knowledge, the size of the moon in relation to the earth is unique and spectacular: with a diameter of around 3,476 kilometers, it is more than a quarter of the earth's diameter at the equator. Its distance from the Earth varies between around 356,000 and 407,000 kilometers due to its elliptical orbit.

The closer the moon is to the earth, the brighter and larger it appears, even if only minimally. It does not shine itself, but is illuminated by the sun.

However, its size and brightness are nothing compared to the early Earth age around four billion years ago. Back then, the moon was only around 60,000 kilometers away from the earth - and must have seemed gigantic. But back then there were no humans to marvel at such a spectacle.

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