I recently had a discussion with a friend. This friend is on the rather esoteric end of the spectrum – which to me is absolutely fine. However, at one point in the discussion, he was talking about alternative healing techniques of the ancient Mayans. I know nothing of the Mayan tradition. But in this discussion, my friend opened up to me that the Maya adapted their healing methods to the astrological occurrences of the time and the zodiac sign of the specific patient. To which I replied, that I doubt the reasonability of such practices – I was and am convinced, that our zodiac sign is absolutely meaningless to our health and the same applies to the current position of the moon and stars. His response was something I did not have a good answer for at the time.

He said:

“Do you not see what the moon is doing to the ocean? Have you seen the tides? Would you not suggest, that something so powerful – something that displaces tons and tons of water – would at least have a tiny effect on our body?
The human adult body is 60% water after all.”

I knew he was wrong, but I did not know why.
So I did my research and the next time a similar topic comes up, I will be prepared. And so will you.

# Calculating gravitational force

Suppose you want to calculate the size of the gravitational force acting between you and another object. This is done simply by using Newton´s equation.

We got a couple of letters here that need explaining:

F: is the gravitational force acting between two objects. This is measured in the unit Newton. One Newton or one N is the force needed to accelerate one kilogram of mass at the rate of one meter per second (squared) in the direction of the applied force.
Standing on earth one Newton of force would be the equivalent of carrying a load of 100g.

G: is the gravitational constant. This is an empirical physical constant, that is being used in the calculation of gravitational effects. It is being used in Newton’s law of universal gravitation and in Einstein’s general theory of relativity. G has stood the test of time – we can trust in G.

m: is the mass of the objects. It is also a measure of its resistance to acceleration when force is applied. How hard do I have to kick something to make it move? This depends on the mass of the object. It is measured in Kg. However Mass and Weight are not the exact same thing – think of it as two sides of the same coin.
In a constant gravitational field, the weight of an object is proportional to its mass, and it is unproblematic to use the same unit for both concepts. Imagine however something is in free fall. This object is now weightless, as its weight cannot be measured. No matter how strong the gravitational field, objects in free fall are weightless, though they still have mass. Conceptually, mass is something like the intrinsic weight of an object. But measuring the weight of an object depends on the gravitational force of the planet I am standing on or if the object is currently in free fall.

r: This is easy. This is the distance of the two objects measured in meters.

So, we can conclude that the strength of the gravitational force of two objects depends on their mass and how far away the objects are from each other.

The bigger the mass and the closer the distance – the stronger the gravitational pull.

# But water is liquid

To increase its mass – water has to stick together.
One liter of water has a mass of almost exactly one kilogram when measured at its maximal density, which occurs at about 4 °C. Individual drops of water do not have a lot of mass. Just like a solid, the density of a liquid equals the mass of the liquid divided by its volume. Depending on the temperature and on how many square meters of space the water exists in - the mass of the water increases. This is why the ocean is affected by the tides, but a puddle of water is not. But this is not the whole story!

# How tides work

The tides may work differently from how you think.
The moon does not actually pull the water off the coast. The sun and the moon create a bulge in the oceans. And the earth actually moves within this bulge.

You can see where the ocean surface is thinner. The earth is rotating into the bulge and out of the bulge, depending on where exactly you are positioned on the earth. The bulge is already there and all we are doing is passing through the bulge with the rotating earth.
The tides do not rise – it was just the explanation we humans gave the occurrence from the specific location it was observed from. The intensity of the tide, that the moon is responsible for is the same no matter if it’s a full moon or not or something in between. But what happens at full moon is that the sun’s gravitational force on the ocean adds to the moons.

This actually has a cool name. When three or more (eg. sun, earth, and moon) celestial objects are roughly in a straight-line it is called a Syzygy.

When Sun and Moon are at a 90-degree angle to each other, the bulges cancel each other - which creates the lowest tide. This is called a Nipptide.

So we now understand that the moon alone does not create the tide and it isn’t even pulling them. The earth rather moves through the bulge the sun and moon create.

# What about the gravitational pull on the human body then?

So let’s get to the gravitational pull the moon exerts on the human body. First of all, we now know, that the force of the gravitational pull depends on the mass of the two objects. The mass of the individual body of course is much less than the ocean, which greatly decreases the pulling force.

So let’s put it into our equation.

The mass of the moon is 7.347.673.090.000.000.000.000.000.000.000 kilograms.

The mass of a human being could be around 70 kilograms.

The distance to the moon is 384.400.000 meters.

So the force the moon alone is putting on our body would be 232.32 Newtons, which would be around 23.65742 kilograms of force. This could be seen as a lot. But we are put under this force at all times - no matter the state of the moon.

But tides were never about the moon alone but about the dance of the moon with the sun. The gravitational force of the sun on our bodies is also much bigger. So really we are looking at the difference of force applied depending on the position of the moon. Also - the side of our head that is facing the moon is closer and therefore has to endure a stronger force than the other side, which is further away. So we are really measuring the difference of force for each side of my head.

And now we are at such a small influence, that lying your head on a soft pillow is deforming your skull much more than the moon could ever affect your body in the first place.

Until next week,

Sam