This is a misunderstanding. In ancient times, people watched the tides of the sea and, seeing that the tidal wave followed the Moon, decided that there was a kinship between the moon and water, causing them to be drawn to each other. This explanation has already been transferred to water, not only in the seas, but in any form, without any verification. For example, people began to believe that during the full moon, groundwater rises closer to the surface and this promotes plant growth. Another form of this belief explained the behavior of sleepwalkers by the fact that the Moon attracts blood in the veins, which causes the blood to rush to the head and disrupt reason.
In fact, the Moon attracts not only water, but also any objects - according to Newton's law of universal gravitation. According to this law, the force of attraction decreases quite quickly with distance. The average distance to the Moon is 384,000 kilometers. The diameter of the Earth is 12,700 kilometers. This means that one side of the Earth is about 3% closer to the Moon than the opposite side. According to the law of gravity, the side of the Earth closest to the Moon is attracted by the Moon about 7% stronger than the side farther away. For the Earth, this means that a force acts on it, tending to pull the globe along the Moon-Earth axis. This force is called tidal force.
Under the influence of tidal force, the entire globe is slightly deformed. Small humps appear on the side of the Moon and on the opposite side, and on the sides the earth’s crust, on the contrary, sinks slightly. At the equator the height of these solid tides is about half a meter. At higher latitudes it decreases. Due to the rotation of the Earth around its axis, tidal waves move along the surface of the Earth, going around it in about 25 hours (an extra hour is associated with the movement of the Moon in orbit). During this time, the tide ebbs and flows twice at every point on Earth.
Solid tides are difficult to notice because the Earth's crust rises and falls on the scale of entire continents. They were measured only thanks to new astronomical and space technologies in the second half of the 20th century. For example, the global positioning system GPS (a system for determining the location of objects based on the use of artificial Earth satellites) in principle allows tracking the movements of the earth's crust with an accuracy of centimeters, and laser ranging of satellites with an accuracy of millimeters.
Tides in the oceans are caused by the same tidal force. In the open ocean, the height of the tidal wave is approximately the same as in the earth's crust - 30-60 centimeters. But sea water, unlike the earth's crust, is mobile. Therefore, as you approach the shore, the height of the tidal wave increases. In narrow bays it can rise 10 meters or more.
Tidal deformations explain many phenomena. You can read more about them in, published by the publishing house MCNMO.
Questions.
1. What was called universal gravity?
Universal gravity was the name given to the mutual attraction of all bodies in the Universe.
2. What is another name for the forces of universal gravity?
The forces of universal gravitation are otherwise called gravitational (from the Latin gravitas - “gravity”).
3. Who discovered the law of universal gravitation and in what century?
The law of universal gravitation was discovered by Isaac Newton in the 17th century.
4. How is the law of universal gravitation read?
Any two bodies attract each other with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
5. Write down a formula expressing the law of universal gravitation.
6. In what cases should this formula be used to calculate gravitational forces?
The formula can be used to calculate gravitational forces if the bodies can be taken as material points: 1) if the sizes of the bodies are much smaller than the distances between them; 2) if two bodies are spherical and homogeneous; 3) if one body, spherical in shape, is many times larger in mass and size than the second.
7. Is the Earth attracted to an apple hanging on a branch?
In accordance with the law of universal gravitation, an apple attracts the Earth with the same force as the Earth attracts an apple, only in the opposite direction.
Exercises.
1. Give examples of the manifestation of gravity.
The fall of bodies to the ground under the influence of gravity, the attraction of celestial bodies (Earth, Moon, sun, planets, comets, meteorites) to each other.
2. The space station flies from the Earth to the Moon. How does the modulus of the vector of its force of attraction to the Earth change in this case? to the moon? Is the station attracted to the Earth and the Moon with equal or different magnitude forces when it is in the middle between them? Justify all three answers. (It is known that the mass of the Earth is approximately 81 times the mass of the Moon).
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3. It is known that the mass of the Sun is 330,000 times greater than the mass of the Earth. Is it true that the Sun attracts the Earth 330,000 times stronger than the Earth attracts the Sun? Explain your answer.
No, bodies attract each other with equal forces, because... the force of attraction is proportional to the product of their masses.
4. The ball thrown by the boy moved upward for some time. At the same time, its speed decreased all the time until it became equal to zero. Then the ball began to fall down with increasing speed. Explain: a) whether the force of gravity towards the Earth acted on the ball during its upward movement; down; b) what caused the decrease in the speed of the ball as it moved up; increasing its speed when moving down; c) why, when the ball moved up, its speed decreased, and when it moved down, it increased.
a) yes, the force of gravity acted all the way; b) universal gravitational force (gravity of the Earth); c) when moving up, the speed and acceleration of the body are multidirectional, and when moving down, they are codirectional.
5. Is a person standing on Earth attracted to the Moon? If so, what is it more attracted to: the Moon or the Earth? Is the Moon attracted to this person? Justify your answers.
Yes, all bodies are attracted to each other, but the force of attraction of a person to the Moon is much less than to the Earth, because The moon is much further away.
Our planet has many mysteries, but over time people gradually unravel and explain certain processes and phenomena occurring on Earth. And today we want to talk about issues of gravity and understand why the Earth attracts surrounding bodies.
Why does the Earth attract people?
And we will start the conversation with ourselves. It's no secret that people are attracted to the Earth. This is an obvious and indisputable fact that is easy to prove: jumping from any height, be it an ordinary chair or a parachute jump, a person invariably rushes towards the Earth.
However, the question is why we are heading directly to Earth. And here the answer is ordinary physics, or more precisely, the law of universal gravitation. As Newton noted many centuries ago, bodies with greater mass have properties that allow them to attract bodies with less mass. That is why the Earth attracts not only humans, but also all surrounding bodies.
Why does the Earth attract the Moon?
As you know, our planet attracts not only those bodies that are located directly on its surface or even in the atmosphere. We are also talking about such a celestial body as the Moon, our natural satellite. As you know, the Moon revolves around the Earth, and the key to such rotation, by the way, is precisely the corral of universal gravity.
It is precisely due to its movement and attraction to the Earth that the Moon moves along its trajectory around our planet. It is noteworthy that scientists have long been observing a gradual change in the trajectory of our satellite, and also prophesy that in the future it may even collapse on the surface of the Earth. However, this “future” on a cosmic scale goes millions of years into the future.
It is worth understanding that in this situation, the rotation of the Moon around the Earth is nothing more than a controlled fall, working under the influence of gravity, as well as the speed of movement.
Why does the sun attract the earth
As we have already said, the law of universal gravitation is relevant not only on the surface of the Earth, but also in its orbit. However, no one cancels it in other parts of space and our universe. So, for example, just as the Earth attracts the Moon, the Sun attracts the Earth and other objects in our galaxy. All these objects revolve around the Sun, and this phenomenon also occurs due to universal gravity, because the Sun has the largest mass in our galaxy, which exceeds the combined mass of all other bodies in Space.
This is a misunderstanding.
In ancient times, people watched the tides of the sea and, seeing that the tidal wave followed the Moon, decided that there was a kinship between the moon and water, causing them to be drawn to each other. This explanation has already been transferred to water, not only in the seas, but in any form, without any verification. For example, people began to believe that during the full moon, groundwater rises closer to the surface and this promotes plant growth. Another form of this belief explained the behavior of sleepwalkers by the fact that the Moon attracts blood in the veins, which causes the blood to rush to the head and disrupt reason.
In fact, the Moon attracts not only water, but also any objects - according to Newton's law of universal gravitation. According to this law, the force of attraction decreases quite quickly with distance. The average distance to the Moon is 384,000 kilometers. The diameter of the Earth is 12,700 kilometers. This means that one side of the Earth is about 3% closer to the Moon than the opposite side. According to the law of gravity, the side of the Earth closest to the Moon is attracted by the Moon about 7% stronger than the side farther away. For the Earth, this means that a force acts on it, tending to pull the globe along the Moon-Earth axis. This force is called tidal force.
Under the influence of tidal force, the entire globe is slightly deformed. Small humps appear on the side of the Moon and on the opposite side, and on the sides the earth’s crust, on the contrary, sinks slightly. At the equator the height of these solid tides is about half a meter. At higher latitudes it decreases. Due to the rotation of the Earth around its axis, tidal waves move along the surface of the Earth, going around it in about 25 hours (an extra hour is associated with the movement of the Moon in orbit). During this time, the tide ebbs and flows twice at every point on Earth.
Solid tides are difficult to notice because the Earth's crust rises and falls on the scale of entire continents. They were measured only thanks to new astronomical and space technologies in the second half of the 20th century. For example, the global positioning system GPS (a system for determining the location of objects based on the use of artificial Earth satellites) in principle allows tracking the movements of the earth's crust with an accuracy of centimeters, and laser ranging of satellites with an accuracy of millimeters.
Tides in the oceans are caused by the same tidal force. In the open ocean, the height of the tidal wave is approximately the same as in the earth's crust - 30-60 centimeters. But sea water, unlike the earth's crust, is mobile. Therefore, as you approach the shore, the height of the tidal wave increases. In narrow bays it can rise 10 meters or more.
Tidal deformations explain many phenomena. You can read more about them in the brochure by V. Surdin “The Fifth Force”, published by the publishing house MCNMO.
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