Katrin Laas: Can a Full Moon Really Affect the Human Being?

Katrin Laas, a physics lecturer at TU Institute of Mathematics and Natural Sciences discusses the effects of the full moon on our everyday lives.

Throughout the centuries, people have thought that a full moon can affect our behaviour. They think people tend to make more mistakes while in traffic, there is more criminal activity, more calls to the Emergency Services and, of course, somnambulism or sleep walking. But what is really the case: does a full moon affect our behaviour?

Let’s be honest – a full moon lights the earth pretty well and this makes the nature around us seem more mystical, says Katrin Laas, a lecturer at the Tallinn University Institute of Mathematics and Natural Sciences.

An abundance of statistical studies on the influence of the full moon to people’s behaviour were made in the 1970s and 1980s and are still being conducted throughout the world. We have researched the connections between a full moon and criminal behaviour, bouts of epilepsy and schizophrenia, blood loss during operations, the numbers of suicides and many other phenomena.

Sadly, we have to admit that on most occasions there is no correlation between the phases of the moon and human behaviour. Many researches, that initially found a connection, have today been disproven. Therefore, a full moon does not affect us and is just an urban legend that has been shared for centuries.

So why do we connect everything bad and unexpected to the full moon? The most scientific explanation would have to do with the selective memory of the human being. In actuality, criminal activity and various accidents happen also during other phases of the moon, but if something dramatic happens during a full moon, we will remember it more likely. We tend to forget when nothing happens during a full moon and this gives us the impression that more strange things happen during it. This deceptive connection is also called an illusory correlation – we see correlation where it does not exist.

Can we then say the position of the Moon in relation to the Earth does not affect us at all? No we cannot – during full moon and new moon the Moon, the Earth and the Sun are almost in line, which brings along the biggest tides. Could such highs and lows influence the human being and have something to do with the so-called full moon effect? I must emphasise – during the tides, the most important factor is not the gravitational field of the influencer (the Sun or the Moon), but its change toward the object under influence. Therefore, being significantly smaller than the Earth, the tides within our bodies are also significantly smaller.

But how small are they? Let us say the Sun and the Moon create tides within our bodies, which are as much smaller from those on the Earth, than we are smaller (from head to toe) from the Earth’s diameter. So when the Earth is about 12,742km wide = 12,742,000 metres, and the average human being is 1,75m, then the high and low tides in a human being are about 12,742,000/1,75=7,281,142 times smaller than  those on the Earth.

The high and low tides happen in the solid, liquid and gaseous parts of the Earth. In the solid areas the surface of the earth rises and falls around 50cm on average and brings on changes in the atmospheric pressure, but these changes are insignificant compared to the changes in weather. Since the consistency of a human being is closer to water, we can rather compare the tides within our bodies to those in the water.

Thus, if the surface of the open sea rises on average by 1 metre and up to 21 metres in tight gulfs, and just a few centimetres in Estonia, the tides within people could mathematically be equal to three micro metres on average and up to three nanometres in Estonia. The width of a human hair is around 80 micro metres, so even the most powerful high and low tides would change our height by 0,04 hair widths (in Estonia that would be 0,00004 hair widths).

Therefore we can boldly claim that compared to the change in our diameter brought on by breathing, the influence from the tides created by the Sun and the Moon is insignificant. Therefore, the full moon effect cannot even be connected with the tides – the change in human height during tides is practically impossible to measure. Breathing and other biological processes influence the height of the human being a lot more.