The world spins! Are you sure? Or is it the Universe that rotates, not the Earth?

The world is turning, no matter what you say, years pass, even if you don't notice...

This song of Nilüfer is beautiful, isn't it? It was once the most popular song, now it has become nostalgic.

Nilüfer also sings it in her song, but let me ask you a strange question.

Are you sure that the earth rotates?

Yes, of course it rotates, isn't it obvious from the movement of the sun during the day?

If you want, look from space, you will see that the earth is rotating.

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Yes, we can go into space today. Even we thought we would come to the moon with a little harsh touch, but now the plans seem to have changed, I heard that a more serious moon trip was planned, but no one knows to what day this trip was postponed. It certainly won't happen in 2023, it's just another one of those pre-election promises.

Anyway, the topic is not about our journey to the moon, but human beings were even able to go to the moon and when they looked from there, they saw that the whole world was revolving around themselves.

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However, in ancient times, human beings thought of an earth-centered universe.

The world is standing still and the whole universe is spinning like a propeller around the world!

This is how they thought in ancient times.

Actually, when you look at it from here, it really feels like that, just lift your head up, you won't notice the movement of the sun during the day, but at least the clouds are moving fast, you can understand it.

Sunset or, for those who get up early, dawn are the times when you can observe and notice the movement of the sun by watching it a little.

Look, it's sinking... and it's sinking!

Yes, it really is as if we are standing in our place and the whole universe is revolving around us, right?

We soon realized that the situation was exactly the opposite.

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Leon Foucault is a French physics scientist who lived between 1819 and 1868.

He built a pendulum called the Foucault pendulum and scientifically proved with this pendulum that the world rotates around itself.

Foucault is also the person who gave his name to the device we call gyroscope today (by the way, I have never heard of it, but the Turkish word for gyroscope is "flat rotating", there are also people who call it gyroscope!?).

Although it was known long ago that a rotating weight, such as a sphere, does not change its direction while rotating, the person who first used the modern gyroscope in his experiments and gave the final shape to the device was Leon Foucault.

Yes, Leon Foucault was paralyzed at an early age and passed away, but he also proved that the world rotates with the pendulum he built in his short life. He proved that the world rotates by observing that the pendulum slowly rotates in a certain rotation during its oscillation due to the rotation of the earth.

Today, there is a Foucault pendulum in many museums and it is said to attract the attention of visitors.

While the pendulum's swing rotates clockwise in museums in the northern hemisphere, it rotates in the opposite direction in museums in the southern hemisphere. It does not rotate over the equator.

It is interesting, is not it?

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I don't know if any of you remember that program?

Barış Manço showed the same thing with water in one of his programs in which he traveled around the world.

In a bowl, I think there was a hole or something under the bowl, and the direction of the vortex formed in the water changed direction when it shifted a little from the equator line to the north and south.

Barış Manço added color to the program by saying this is a magical place. He probably didn't know the reason during the program either.

The reason why the vortex changes direction is the rotation effect of the earth. The directions of vortices formed in the seas in the northern and southern hemispheres also vary.

The vortex created by the water draining from our sinks is always in the same direction, try it if you want. The reason for this is the rotation of the earth around itself.

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Apart from the pendulum, Leon Foucault also conducted the same experiment with a gyroscope and observed that the gyroscope made a rotation on the table in a similar way to the pendulum.

Although it seems that the gyroscope changes its direction as the earth rotates, when Foucault checked it with the stars at night, he found that the gyroscope rotates around itself without changing direction relative to the stars, and he said that yes, the gyroscope does not change direction, the earth rotates, and this is proof.

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There are many other studies done by Leon Foucault, for example, he was able to measure the speed of light very close to the real thing at that time.

He also developed a knife-edge method to ensure that telescope mirrors are properly focused.

However, his best-known invention is the Foucault pendulum.

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Yes, there have been many scientists in history who tried to prove that the world is round and revolves around itself, and Galileo is probably the most prominent of them.

Moreover, Galileo was punished by the Inquisition court for this reason.

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Of course, there is also Isaac Newton.

We can say that Newton no longer had any hesitation about the rotation of the earth, but he was also obsessed with some issues regarding the order of the universe.

There is a thought experiment known as “Newton's bucket.”

Isaac Newton said that if you hang a bucket half-filled with water on a rotating table or by tying it to a rope, when you rotate it, the water in the bucket will first stop where it is, but then He said that the water in the bucket will start to rotate with the bucket after a while due to the friction force on the surfaces of the bucket, and that the rotating water will rise on the side surfaces of the bucket due to the centrifugal force and its level will decrease in the middle parts and the water surface will take a concave, that is, parabolic, shape.

Newton said that what did this was the centrifugal force created by the rotation of the bucket, and he suggested that the universe outside the bucket had no role in the rotation of this water, therefore he predicted that the universe outside the bucket had no effect on the absolute order of motion.

According to Newton, the universe was just a background for events. Movement is a local concept. We can tell whether the bucket is spinning or not just by looking at the water in the bucket. He said that the universe has no effect on the rotation of the bucket.

Therefore, since time progresses at a constant speed and the universe, as a matrix whose dimensions do not change, is only the space where events take place, he developed his motion formulas with this logic.

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At this point, I should also tell you about Ernst Mach, an Austrian physicist.

Ernst Waldfried Josef Wenzel Mach is a physicist and also a thinker who lived between 1838-1916.

Albert Einstein was very impressed by his views.

The question that haunted Mach's mind was about motion.

You know, sometimes it has happened to you, when the train on the next platform starts to move while you are lost in thought, it seems as if you are moving with the train you are on.

Here, Mach was stuck on this question in principle when talking about motion.

Which train is actually moving? Is the train on the side platform moving, or are you moving?

How do we understand this?

Relativity! Relativity! This is the theory that Mach put forward in principle.

Mach stuck to the subject of motion.

In fact, he was a physicist who followed Isaac Newton, and he took Newton as a role model.

However, he did not agree with Newton's view that "the universe is the background" that I just mentioned.

He thought that movements should be measured not in a fixed coordinate system, as Newton predicted, but relative to another object, whatever the reference object is. He even thought it was a necessity.

He also influenced Albert Einstein with this idea, and Mach had a significant impact on the intellectual infrastructure of the relativity theories (specific and general) that Einstein would later develop.

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Mach also thought a lot about Newton's intellectual bucket experiment. All kinds of questions came to his mind.

He expressed the questions in his mind about the bucket experiment as follows:

If there was only water in the universe, could we be aware of the movement of water?

Could we see the water as rotating, or would it appear as if the water was motionless?

Since the bucket is outside the universe, could we say that the bucket is rotating?

So, could we claim that it was water that returned, not the bucket?

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In order to answer these questions, we need to include another object in the water universe.

Motion can only be described with reference to another object.

This is called Mach's principle, relativity was an idea that Ernst Mach thought about.

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So which one do you think is correct?

Is the world spinning? Or does the entire universe revolve around the earth?

How do we understand this?

Is Leon Foucault's pendulum enough to prove that the world rotates?

How about a gyroscope experiment? Is that enough?

Could Newton's bucket also be proof that the world rotates?

So what about Mach's principle in this case? Relativity? Who turns to whom and on what basis? Is it possible to understand this?

What if the earth stood still and the entire universe rotated?

Anyone have any ideas?

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Einstein said that if the entire universe revolved around the earth, the earth would begin to wobble from even the slightest impact.

Today we know that the Earth wobbles during its rotation.

Then, if Einstein said so, can we claim that the entire universe is in rotation around the earth?

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I won't tire you.

There is such a thing as the speed of light, the maximum possible speed in this universe is the speed of light.

Can you imagine the rotation speed of a star at the edge of the observable universe, which is approximately 28 billion parsecs in diameter, if the earth was stationary and the universe was in rotation around the earth?

Calculate if you want, let's see how many million times the speed of light that star's speed will be.

(28 billion parsecs means 93 billion light years; if we put the earth at the center of the universe, we are talking about an observable universe with a radius of 46.5 billion light years!)

So unfortunately the world is in a rotational motion, the world is rotating, not the universe.

However, I think what I said is not entirely true. After all, if we had a reference point outside this universe, then we could understand what kind of movement the universe had.

In our current conditions, we can say that the universe is not in rotation.

The world rotates, not the universe!

However, I still think that we can understand how the universe is moving with the help of a large gyroscope.

Anything that spins fast enough and can act as a gyroscope in the universe. Is there a celestial body?

Can we understand whether the universe is in motion or not with such a celestial body?

Of course, when I say motion, I am not talking about the expansion of the universe, what I am talking about is rotational motion. Could the universe be in a rotational motion like the earth?

Maybe one day there will be someone who can answer this question.

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Let me finish by saying, again, stay with the science.

With love and respect to everyone from Moscow.