Obi-Wan Kenobi said that strength holds the galaxy together. The same can be said about gravity. The fact is that gravity allows us to walk on the Earth, the Earth to revolve around the Sun, and the Sun to revolve around the supermassive black hole at the center of our galaxy. How to understand gravity? About this - in our article.
Let's say right away that you will not find here an unambiguously correct answer to the question "What is gravity." Because it just doesn't exist! Gravity is one of the most mysterious phenomena that scientists puzzle over and still cannot fully explain its nature.
There are many hypotheses and opinions. There are more than a dozen theories of gravity, alternative and classical. We will consider the most interesting, relevant and modern.
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Gravity is a physical fundamental interaction
There are 4 fundamental interactions in physics. Thanks to them, the world is exactly the way it is. Gravity is one of these forces.
Fundamental Interactions:
- gravity;
- electromagnetism;
- strong interaction;
- weak interaction.
At the moment, the current theory describing gravity is GR (general relativity). It was proposed by Albert Einstein in 1915-1916.
However, we know that it is too early to talk about the ultimate truth. After all, several centuries before the advent of general relativity in physics, Newtonian theory, which was significantly expanded, dominated to describe gravity.
At the moment, it is impossible to explain and describe all issues related to gravity within the framework of general relativity.
Before Newton, it was widely believed that gravity on earth and celestial gravity were different things. It was believed that the planets move according to their own, different from earthly, ideal laws.
Newton discovered the law of universal gravitation in 1667. Of course, this law existed even during the dinosaurs and much earlier.
Ancient philosophers thought about the existence of gravity. Galileo experimentally calculated the acceleration of free fall on Earth, discovering that it is the same for bodies of any mass. Kepler studied the laws of motion of celestial bodies.
Newton was able to formulate and generalize the results of observations. Here's what he got:
Two bodies are attracted to each other with a force called gravitational force or gravitational force.
The formula for the force of attraction between bodies is:
G is the gravitational constant, m is the mass of the bodies, r is the distance between the centers of mass of the bodies.
What is the physical meaning of the gravitational constant? It is equal to the force with which bodies with masses of 1 kilogram each act on each other, being at a distance of 1 meter from each other.
According to Newton's theory, every object creates a gravitational field. The accuracy of Newton's law has been tested at distances of less than one centimeter. Of course, for small masses these forces are insignificant and can be neglected.
Newton's formula is applicable both for calculating the force of attraction of planets to the sun, and for small objects. We simply do not notice the force with which, say, the balls on the billiard table are attracted. Nevertheless, this force exists and can be calculated.
The force of attraction acts between any bodies in the universe. Its effect extends to any distance.
Newton's law of universal gravitation does not explain the nature of the force of attraction, but establishes quantitative patterns. Newton's theory does not contradict general relativity. It is quite sufficient for solving practical problems on the scale of the Earth and for calculating the motion of celestial bodies.
Gravity in General Relativity
Despite the fact that Newton's theory is quite applicable in practice, it has a number of shortcomings. The law of universal gravitation is a mathematical description, but does not give an idea of the fundamental physical nature of things.
According to Newton, the force of attraction acts at any distance. And it works instantly. Considering that the fastest speed in the world is the speed of light, there is a discrepancy. How can gravity act instantaneously at any distance, when light needs not an instant, but several seconds or even years to overcome them?
Within the framework of general relativity, gravity is considered not as a force that acts on bodies, but as a curvature of space and time under the influence of mass. Thus, gravity is not a force interaction.
What is the effect of gravity? Let's try to describe it using an analogy.
Imagine space as an elastic sheet. If you put a light tennis ball on it, the surface will remain flat. But if you put a heavy weight next to the ball, it will push a hole in the surface, and the ball will begin to roll towards the large and heavy weight. This is "gravity".
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Discovery of gravitational waves
Gravitational waves were predicted by Albert Einstein back in 1916, but they were only discovered a hundred years later, in 2015.
What are gravitational waves? Let's draw an analogy again. If you throw a stone into calm water, circles will go on the surface of the water from the place of its fall. Gravitational waves are the same ripples, perturbations. Only not on the water, but in the world space-time.
Instead of water - space-time, and instead of stone, say, a black hole. Any accelerated movement of mass generates a gravitational wave. If the bodies are in a state of free fall, the distance between them will change when a gravitational wave passes.
Since gravity is a very weak force, the detection of gravitational waves has been associated with great technical difficulties. Modern technologies have made it possible to detect a burst of gravitational waves only from supermassive sources.
A suitable event for registering a gravitational wave is the merger of black holes. Unfortunately or fortunately, this happens quite rarely. Nevertheless, scientists managed to register a wave that literally rolled through the space of the Universe.
To register gravitational waves, a detector with a diameter of 4 kilometers was built. During the passage of the wave, oscillations of mirrors on suspensions in vacuum and the interference of light reflected from them were recorded.
Gravitational waves confirmed the validity of general relativity.
Gravity and elementary particles
In the standard model, certain elementary particles are responsible for each interaction. We can say that particles are carriers of interactions.
The graviton is responsible for gravity - a hypothetical massless particle with energy. By the way, in our separate material, read more about the Higgs boson and other elementary particles that made a lot of noise.
Finally, here are some interesting facts about gravity.
10 facts about gravity
- To overcome the force of gravity of the Earth, the body must have a speed equal to 7.91 km / s. This is the first cosmic speed. It is enough for a body (for example, a space probe) to move in orbit around the planet.
- To escape the Earth's gravitational field, a spacecraft must have a speed of at least 11.2 km/s. This is the second space velocity.
- Objects with the strongest gravity are black holes. Their gravity is so strong that they even attract light (photons).
- You will not find the force of gravity in any equation of quantum mechanics. The fact is that when you try to include gravity in the equations, they lose their relevance. This is one of the most important problems in modern physics.
- The word gravity comes from the Latin “gravis”, which means “heavy”.
- The more massive the object, the stronger the gravity. If a person who weighs 60 kilograms on Earth weighs on Jupiter, the scales will show 142 kilograms.
- NASA scientists are trying to develop a gravitational beam that will allow objects to be moved contactlessly, overcoming the force of gravity.
- Astronauts in orbit also experience gravity. More specifically, microgravity. They seem to fall endlessly along with the ship in which they are.
- Gravity always attracts and never repels.
- A tennis ball-sized black hole pulls objects with the same force as our planet.
Now you know the definition of gravity and you can say what formula is used to calculate the force of attraction. If the granite of science is holding you down harder than gravity, contact our student service. We will help you learn easily under the heaviest workloads!
I decided, to the best of my ability and ability, to focus on lighting in more detail. scientific heritage Academician Nikolai Viktorovich Levashov, because I see that today his works are not yet in the demand that they should be in a society of truly free and reasonable people. people still do not understand the value and importance of his books and articles, because they don't realize the extent of the deception in which we have been living for the last couple of centuries; do not understand that the information about nature, which we consider familiar and therefore true, is 100% false; and they are deliberately imposed on us in order to hide the truth and prevent us from developing in the right direction ...
Law of gravity
Why do we need to deal with this gravity? Is there anything else we don't know about her? What are you! We already know a lot about gravity! For example, Wikipedia kindly informs us that « gravity (attraction, worldwide, gravity) (from lat. gravitas - "gravity") - a universal fundamental interaction between all material bodies. In the approximation of low speeds and weak gravitational interaction, it is described by Newton's theory of gravitation, in the general case it is described by Einstein's general theory of relativity ... " Those. simply put, this Internet chatterbox says that gravity is the interaction between all material bodies, and even more simply - mutual attraction material bodies to each other.
We owe the appearance of such an opinion to Comrade. Isaac Newton, credited with the discovery in 1687 "Law of gravity", according to which all bodies are allegedly attracted to each other in proportion to their masses and inversely proportional to the square of the distance between them. I am glad that Comrade. Isaac Newton is described in Pedia as a highly educated scientist, unlike Comrade. who is credited with discovering electricity…
It is interesting to look at the dimension of the "Force of Attraction" or "Force of Gravity", which follows from Com. Isaac Newton, having the following form: F=m 1 *m2 /r2
The numerator is the product of the masses of the two bodies. This gives the dimension of "kilograms squared" - kg 2. The denominator is "distance" squared, i.e. square meters - m 2. But strength is not measured in strange kg 2 / m 2, and in no less strange kg * m / s 2! It turns out to be a mismatch. To remove it, the "scientists" came up with a coefficient, the so-called. "gravitational constant" G , equal to approximately 6.67545×10 −11 m³/(kg s²). If we now multiply everything, we get the correct dimension of "Gravity" in kg * m / s 2, and this abracadabra is called in physics "newton", i.e. force in today's physics is measured in "".
Interesting: what physical meaning has a coefficient G , for something reducing the result in 600 billion times? None! "Scientists" called it "proportionality coefficient". And they brought it in for fit dimension and result under the most desired! This is the kind of science we have today ... It should be noted that, in order to confuse scientists and hide contradictions, measurement systems have changed several times in physics - the so-called. "systems of units". Here are the names of some of them, replacing each other, as the need to create the next disguises arose: MTS, MKGSS, SGS, SI ...
It would be interesting to ask Comrade. Isaac: a how did he guess that there is a natural process of attracting bodies to each other? How did he guess that the “Force of Attraction” is proportional precisely to the product of the masses of two bodies, and not to their sum or difference? How did he so successfully comprehend that this Force is inversely proportional precisely to the square of the distance between the bodies, and not to the cube, doubling or fractional power? Where at comrade appeared such inexplicable guesses 350 years ago? After all, he did not conduct any experiments in this area! And, if you believe the traditional version of history, in those days even the rulers were not yet completely even, but here such an inexplicable, simply fantastic insight! Where?
Yes out of nowhere! Tov. Isaac knew nothing of the kind, nor did he investigate anything of the kind, and did not open. Why? Because in reality the physical process " attraction tel" to each other does not exist, and, accordingly, there is no Law that would describe this process (this will be convincingly proved below)! In reality, Comrade Newton in our indistinct, just attributed the discovery of the law of "Universal gravitation", simultaneously awarding him the title of "one of the founders of classical physics"; in the same way as Comrade was attributed at one time. bene Franklin, which had 2 classes education. In “Medieval Europe”, this did not happen: there was a lot of tension not only with the sciences, but simply with life ...
But, fortunately for us, at the end of the last century, the Russian scientist Nikolai Levashov wrote several books in which he gave "alphabet and grammar" undistorted knowledge; returned to earthlings the previously destroyed scientific paradigm, with the help of which easily explained almost all the "unsolvable" mysteries of earthly nature; explained the fundamentals of the structure of the Universe; showed under what conditions on all planets on which necessary and sufficient conditions appear, A life- living matter. He explained what kind of matter can be considered alive, and what physical meaning natural process called a life". Then he explained when and under what conditions "living matter" acquires Intelligence, i.e. realizes its existence - becomes intelligent. Nikolai Viktorovich Levashov conveyed to people in his books and films very much undistorted knowledge. He also explained what "gravity", where does it come from, how does it work, what is its actual physical meaning. Most of all this is written in books and. And now let's deal with the "Law of Universal Gravitation" ...
The "Law of Gravity" is a hoax!
Why do I so boldly and confidently criticize physics, the "discovery" of Comrade. Isaac Newton and the "great" "Law of Universal Gravitation" itself? Yes, because this “Law” is a fiction! Deception! Fiction! A worldwide scam to lead earthly science to a dead end! The same scam with the same goals as the notorious "Theory of Relativity" comrade. Einstein.
Proof of? If you please, here they are: very precise, strict and convincing. They were splendidly described by the author O.Kh. Derevensky in his wonderful article. Due to the fact that the article is quite voluminous, I will give here a very brief version of some of the evidence for the falsity of the "Law of Universal Gravity", and citizens who are interested in the details will read the rest for themselves.
1. In our solar system only the planets and the Moon, the Earth's satellite, have gravity. The satellites of the other planets, and there are more than six dozen of them, do not have gravity! This information is completely open, but not advertised by "scientific" people, because it is inexplicable from the point of view of their "science". Those. b about Most of the objects in our solar system do not have gravity - they do not attract each other! And this completely refutes the "Law of General Gravity".
2. Henry Cavendish Experience by attracting massive blanks to each other is considered irrefutable proof of the presence of attraction between bodies. However, despite its simplicity, this experience is not openly reproduced anywhere. Apparently, because it does not give the effect that some people once announced. Those. today, with the possibility of strict verification, experience does not show any attraction between bodies!
3. Launch of an artificial satellite into orbit around the asteroid. In the middle of February 2000 the Americans drove a space probe NEAR close enough to the asteroid Eros, leveled the speeds and began to wait for the capture of the probe by the gravity of Eros, i.e. when the satellite is gently attracted by the gravity of the asteroid.
But for some reason the first date didn't work out. The second and subsequent attempts to surrender to Eros had exactly the same effect: Eros did not want to attract the American probe NEAR, and without engine work, the probe did not stay near Eros . This space date ended in nothing. Those. no attraction between probe with mass 805 kg and an asteroid weighing over 6 trillion tons could not be found.
Here it is impossible not to note the inexplicable stubbornness of the Americans from NASA, because the Russian scientist Nikolai Levashov, living at that time in the United States, which he then considered a completely normal country, wrote, translated into English and published in 1994 year of his famous book, in which he explained everything that NASA specialists needed to know in order to make their probe NEAR did not hang out as a useless piece of iron in space, but brought at least some benefit to society. But, apparently, exorbitant self-conceit played a trick on the “scientists” there.
4. Next try repeat the erotic experiment with the asteroid Japanese. They chose an asteroid called Itokawa, and sent on May 9 2003 year to him a probe called ("Falcon"). In September 2005 year, the probe approached the asteroid at a distance of 20 km.
Taking into account the experience of the “stupid Americans”, the smart Japanese equipped their probe with several engines and an autonomous short-range navigation system with laser rangefinders, so that it could approach the asteroid and move around it automatically, without the participation of ground operators. “The first number of this program was a comedy stunt with the landing of a small research robot on the surface of an asteroid. The probe descended to the calculated height and carefully dropped the robot, which was supposed to slowly and smoothly fall to the surface. But... it didn't fall. Slow and smooth he got carried away somewhere far away from the asteroid. There he went missing ... The next number of the program turned out to be, again, a comedy trick with a short landing of the probe on the surface "to take a soil sample." It came out as a comedy because, in order to ensure the best performance of laser rangefinders, a reflective marker ball was dropped onto the surface of the asteroid. There were no engines on this ball either, and ... in short, there was no ball in the right place ... So did the Japanese Sokol land on Itokawa, and what did he do on it if he sat down, science does not know ... "Conclusion: the Japanese miracle of Hayabusa is not was able to discover no attraction between probe ground 510 kg and an asteroid with mass 35 000 tons.
Separately, I would like to note that an exhaustive explanation of the nature of gravity by a Russian scientist Nikolai Levashov gave in his book, which he first published in 2002 year - almost a year and a half before the start of the Japanese "Falcon". And, despite this, the Japanese "scientists" followed exactly in the footsteps of their American colleagues and carefully repeated all their mistakes, including landing. Here is such an interesting continuity of "scientific thinking" ...
5. Where do hot flashes come from? A very interesting phenomenon described in the literature, to put it mildly, is not entirely correct. “... There are textbooks on physics, where it is written what should be - in accordance with the "law of universal gravitation". There are also textbooks oceanography, where it is written what they are, tides, in fact.
If the law of universal gravitation operates here, and ocean water is attracted, including to the Sun and the Moon, then the "physical" and "oceanographic" patterns of the tides must coincide. So do they match or not? It turns out that to say that they do not match is to say nothing. Because the "physical" and "oceanographic" pictures have no relationship at all nothing in common... The actual picture of tidal phenomena is so different from the theoretical one - both qualitatively and quantitatively - that based on such a theory, tides can be predicted impossible. Yes, no one is trying to do it. Not crazy after all. They do this: for each port or other point of interest, the ocean level dynamics is modeled by the sum of oscillations with amplitudes and phases that are found purely empirically. And then they extrapolate this sum of fluctuations forward - so you get the pre-calculations. The captains of the ships are happy - well, okay! .. ”This all means that our earthly tides are also do not obey"Law of universal gravitation".
What is gravity really
The real nature of gravity for the first time in modern history was clearly described by academician Nikolai Levashov in a fundamental scientific work. In order for the reader to better understand what has been written regarding gravity, I will give a little preliminary explanation.
The space around us is not empty. It is all completely filled with many different matters, which Academician N.V. Levashov named "first matter". Previously, scientists called all this riot of matter "ether" and even received convincing evidence of its existence (the famous experiments of Dayton Miller, described in the article by Nikolai Levashov "Theory of the Universe and Objective Reality"). Modern "scientists" have gone much further and now they "ether" called "dark matter". Enormous progress! Some matters in the "ether" interact with each other to one degree or another, some do not. And some primary matter begins to interact with each other, falling into changed external conditions in certain curvature of space (heterogeneities).
Curvature of space appears as a result of various explosions, including "supernova explosions". « When a supernova explodes, fluctuations in the dimensionality of space occur, similar to the waves that appear on the surface of water after a stone is thrown. The masses of matter ejected during the explosion fill these inhomogeneities in the dimensionality of the space around the star. From these masses of matter, planets ( and ) begin to form ... "
Those. planets are not formed from space debris, as modern “scientists” for some reason claim, but are synthesized from the matter of stars and other primary matters that begin to interact with each other in suitable inhomogeneities of space and form the so-called. "hybrid matter". It is from these “hybrid matters” that the planets and everything else in our space are formed. our planet, just like the rest of the planets, is not just a "piece of stone", but a very complex system consisting of several spheres nested one into another (see). The densest sphere is called the "physically dense level" - this is what we see, the so-called. physical world. Second in terms of density, a slightly larger sphere is the so-called. "ethereal material level" of the planet. Third sphere - "astral material level". 4th the sphere is the "first mental level" of the planet. Fifth the sphere is the "second mental level" of the planet. And sixth the sphere is the "third mental level" of the planet.
Our planet should only be considered as the totality of these six spheres– six material levels of the planet nested one into another. Only in this case it is possible to get a complete picture of the structure and properties of the planet and the processes occurring in nature. The fact that we are not yet able to observe the processes taking place outside the physically dense sphere of our planet does not indicate that “there is nothing there”, but only that at present our sense organs are not adapted by nature for these purposes. And one more thing: our Universe, our planet Earth and everything else in our Universe is formed from seven various types of primary matter merged into six hybrid materials. And it is neither divine nor unique. This is just a qualitative structure of our Universe, due to the properties of the heterogeneity in which it was formed.
Let's continue: the planets are formed by the merging of the corresponding primary matter in the areas of space inhomogeneities that have properties and qualities suitable for this. But in these, as in all other regions of space, a huge number of primal matter(free forms of matter) of various types, not interacting or very weakly interacting with hybrid matters. Getting into the area of heterogeneity, many of these primary matters are affected by this heterogeneity and rush to its center, in accordance with the gradient (difference) of space. And, if a planet has already formed in the center of this heterogeneity, then the primary matter, moving towards the center of heterogeneity (and the center of the planet), creates directional flow, which creates the so-called. gravitational field. And, accordingly, under gravity you and I need to understand the impact of the directed flow of primary matter on everything that is in its path. That is, to put it simply, gravity is pressure material objects to the surface of the planet by the flow of primary matter.
Is not it, reality is very different from the fictitious law of "mutual attraction", which supposedly exists everywhere for no clear reason. Reality is much more interesting, much more complex and much simpler at the same time. Therefore, the physics of real natural processes is much easier to understand than fictional ones. And the use of real knowledge leads to real discoveries and the effective use of these discoveries, and not to sucked from the finger.
antigravity
As an example of today's scientific profanity one can briefly analyze the "scientists" explanation of the fact that "rays of light are bent near large masses", and therefore we can see that it is closed to us by stars and planets.
Indeed, we can observe objects in the Cosmos that are hidden from us by other objects, but this phenomenon has nothing to do with the masses of objects, because the “universal” phenomenon does not exist, i.e. no stars, no planets NOT attract no rays to themselves and do not bend their trajectory! Why then are they "curved"? There is a very simple and convincing answer to this question: rays are not bent! They just do not spread in a straight line, as we are accustomed to understand, and in accordance with form of space. If we consider a beam passing near a large cosmic body, then we must keep in mind that the beam goes around this body, because it is forced to follow the curvature of space, as if along a road of the corresponding shape. And there is simply no other way for the beam. The beam cannot help but go around this body, because the space in this area has such a curved shape ... Small to what has been said.
Now, returning to antigravity, it becomes clear why Mankind can never catch this nasty "anti-gravity" or achieve at least something of what the clever functionaries of the dream factory show us on TV. We are specifically forced for more than a hundred years, internal combustion engines or jet engines have been used almost everywhere, although they are very far from perfect both in terms of the principle of operation, and in design, and in efficiency. We are specifically forced mine using various generators of cyclopean sizes, and then transmit this energy through wires, where b about most of it is scattered in space! We are specifically forced live the life of unreasonable beings, so we have no reason to be surprised that we can’t do anything sensible either in science, or in technology, or in economics, or in medicine, or in organizing a decent life for society.
I will now give you a few examples of the creation and use of antigravity (aka levitation) in our lives. But these ways of achieving anti-gravity are most likely discovered by accident. And in order to consciously create a really useful device that implements antigravity, you need to know the real nature of the phenomenon of gravity, explore it, analyze and understand all its essence! Only then can something sensible, effective and really useful to society be created.
The most common anti-gravity device we have is balloon and many of its variations. If it is filled with warm air or a gas that is lighter than the atmospheric gas mixture, then the ball will tend to fly up, and not fall down. This effect has been known to people for a very long time, but still does not have a complete explanation- one that would no longer give rise to new questions.
A short search on YouTube led to the discovery of a large number of videos that demonstrate very real examples of antigravity. I will list some of them here so that you can be sure that antigravity ( levitation) really exists, but ... so far none of the "scientists" has explained it, apparently, pride does not allow ...
Gravity is the most powerful force in the Universe, one of the four fundamental foundations of the universe, which determines its structure. Once, thanks to her, planets, stars and entire galaxies arose. Today, it keeps the Earth in orbit in its never-ending journey around the Sun.
Attraction is of great importance for everyday life of a person. Thanks to this invisible force, the oceans of our world pulsate, rivers flow, raindrops fall to the ground. Since childhood, we feel the weight of our body and surrounding objects. The influence of gravity on our economic activity is also enormous.
The first theory of gravity was created by Isaac Newton at the end of the 17th century. His law of universal gravitation describes this interaction within the framework of classical mechanics. This phenomenon was described more widely by Einstein in his general theory of relativity, which was published at the beginning of the last century. The processes occurring with the force of gravity at the level of elementary particles should be explained by the quantum theory of gravity, but it has yet to be created.
Today we know much more about the nature of gravity than in Newton's time, but despite centuries of study, it still remains a real stumbling block in modern physics. There are many white spots in the existing theory of gravity, and we still do not understand exactly what generates it, and how this interaction is transferred. And, of course, we are very far from being able to control the force of gravity, so that antigravity or levitation will exist only on the pages of science fiction novels for a long time to come.
What fell on Newton's head?
People have thought about the nature of the force that attracts objects to the earth at all times, but it was only in the 17th century that Isaac Newton managed to lift the veil of secrecy. The basis for his breakthrough was laid by the works of Kepler and Galileo, brilliant scientists who studied the movements of celestial bodies.
A century and a half before the Newtonian Law of universal gravitation, the Polish astronomer Copernicus believed that attraction is “... nothing more than a natural desire that the father of the Universe bestowed on all particles, namely, to unite into one common whole, forming bodies of a spherical shape.” Descartes, on the other hand, considered attraction to be the result of perturbations in the world ether. The Greek philosopher and scientist Aristotle was sure that mass affects the speed of falling bodies. And only Galileo Galilei at the end of the 16th century proved that this is not true: if there is no air resistance, all objects accelerate equally.
Contrary to the popular legend about the head and the apple, Newton went to understand the nature of gravity for more than twenty years. His law of gravity is one of the most significant scientific discoveries of all time. It is universal and allows you to calculate the trajectories of celestial bodies and accurately describes the behavior of objects around us. The classical theory of gravitation laid the foundations of celestial mechanics. Newton's three laws gave scientists the opportunity to discover new planets literally "on the tip of a pen", in the end, thanks to them, a person was able to overcome the earth's gravity and fly into space. They summed up a strict scientific basis for the philosophical concept of the material unity of the universe, in which all natural phenomena are interconnected and controlled by common physical rules.
Newton not only published a formula that allows you to calculate what the force that attracts bodies to each other is, he created a holistic model, which also included mathematical analysis. These theoretical conclusions have been repeatedly confirmed in practice, including with the help of the most modern methods.
In Newtonian theory, any material object generates an attraction field, which is called gravitational. Moreover, the force is proportional to the mass of both bodies and inversely proportional to the distance between them:
F = (G m1 m2)/r2
G is the gravitational constant, which is equal to 6.67 × 10−11 m³ / (kg s²). Henry Cavendish was the first to calculate it in 1798.
In everyday life and applied disciplines, the force with which the earth pulls on a body is spoken of as its weight. The attraction between any two material objects in the universe is what gravity is in simple terms.
The force of attraction is the weakest of the four fundamental interactions of physics, but due to its features, it is able to regulate the movement of star systems and galaxies:
- Attraction works at any distance, this is the main difference between gravity and strong and weak nuclear interaction. With increasing distance, its effect decreases, but it never becomes equal to zero, so we can say that even two atoms located at different ends of the galaxy exert mutual influence. It's just very small;
- Gravity is universal. The field of attraction is inherent in any material body. Scientists have not yet discovered an object on our planet or in space that would not participate in this type of interaction, so the role of gravity in the life of the Universe is enormous. In this, gravitation differs from electromagnetic interaction, whose influence on cosmic processes is minimal, since in nature most bodies are electrically neutral. Gravitational forces cannot be limited or shielded;
- Gravity acts not only on matter, but also on energy. For him, the chemical composition of objects does not matter, only their mass plays a role.
Using the Newtonian formula, the force of attraction can be easily calculated. For example, gravity on the Moon is several times less than on Earth, because our satellite has a relatively small mass. But it is enough for the formation of regular tides in the World Ocean. On Earth, the free fall acceleration is about 9.81 m/s2. Moreover, at the poles it is somewhat larger than at the equator.
Despite their great importance for the further development of science, Newton's laws had a number of weaknesses that haunted researchers. It was not clear how gravity works through absolutely empty space over vast distances, and at an incomprehensible speed. In addition, data gradually began to accumulate that contradicted Newton's laws: for example, the gravitational paradox or the displacement of Mercury's perihelion. It became obvious that the theory of universal gravitation needs to be improved. This honor fell to the brilliant German physicist Albert Einstein.
Attraction and relativity
Newton's refusal to discuss the nature of gravity ("I make no hypotheses") was an obvious weakness in his concept. Not surprisingly, many theories of gravity emerged in the years that followed.
Most of them belonged to the so-called hydrodynamic models, which tried to justify the emergence of gravity by the mechanical interaction of material objects with some intermediate substance that has certain properties. Researchers called it differently: "vacuum", "ether", "flow of gravitons", etc. In this case, the force of attraction between bodies arose as a result of a change in this substance, when it was absorbed by objects or screened flows. In reality, all such theories had one serious drawback: quite accurately predicting the dependence of the gravitational force on distance, they should have led to the deceleration of bodies that moved relative to the “ether” or “graviton flow”.
Einstein approached this issue from a different angle. In his general theory of relativity (GR), gravity is seen not as an interaction of forces, but as a property of space-time itself. Any object that has mass causes it to bend, which causes attraction. In this case, gravity is a geometric effect, which is considered within the framework of non-Euclidean geometry.
Simply put, the space-time continuum affects matter, causing its movement. And that, in turn, affects the space, “indicating” to it how to bend.
The forces of attraction also act in the microcosm, but at the level of elementary particles their influence, in comparison with the electrostatic interaction, is negligible. Physicists believe that the gravitational interaction was not inferior to the rest in the first moments (10 -43 seconds) after the Big Bang.
At present, the concept of gravity, proposed in the general theory of relativity, is the main working hypothesis accepted by the majority of the scientific community and confirmed by the results of numerous experiments.
Einstein in his work foresaw the amazing effects of gravitational forces, most of which have already been confirmed. For example, the ability of massive bodies to bend light rays and even slow down the passage of time. The latter phenomenon is necessarily taken into account in the operation of global satellite navigation systems such as GLONASS and GPS, otherwise after a few days their error would be tens of kilometers.
In addition, a consequence of Einstein's theory are the so-called subtle effects of gravity, such as the gravimagnetic field and drag of inertial frames of reference (aka the Lense-Thirring effect). These manifestations of gravity are so weak that for a long time they could not be detected. Only in 2005, thanks to NASA's unique Gravity Probe B mission, the Lense-Thirring effect was confirmed.
Gravitational radiation or the most fundamental discovery of recent years
Gravitational waves are fluctuations in the geometric space-time structure that propagate at the speed of light. The existence of this phenomenon was also predicted by Einstein in general relativity, but due to the weakness of the gravitational force, its magnitude is very small, so it could not be detected for a long time. Only indirect evidence spoke in favor of the existence of radiation.
Such waves generate any material objects moving with asymmetric acceleration. Scientists describe them as "ripples of space-time." The most powerful sources of such radiation are colliding galaxies and collapsing systems consisting of two objects. A typical example of the latter case is the merger of black holes or neutron stars. In such processes, gravitational radiation can pass more than 50% of the total mass of the system.
Gravitational waves were first detected in 2015 by two LIGO observatories. Almost immediately, this event received the status of the largest discovery in physics in recent decades. In 2017, he was awarded the Nobel Prize. After that, scientists managed to detect gravitational radiation several more times.
Back in the 70s of the last century - long before experimental confirmation - scientists proposed using gravitational radiation for long-distance communication. Its undoubted advantage is its high ability to pass through any substance without being absorbed. But at present this is hardly possible, because there are huge difficulties in generating and receiving these waves. Yes, and we still do not have enough real knowledge about the nature of gravity.
Today, several installations similar to LIGO are operating in different countries of the world, and new ones are being built. It is likely that we will learn more about gravitational radiation in the near future.
Alternative theories of universal gravitation and the reasons for their creation
Currently, the dominant concept of gravity is general relativity. The entire existing array of experimental data and observations is consistent with it. At the same time, it has a large number of frankly weak points and controversial points, so attempts to create new models that explain the nature of gravity do not stop.
All theories of universal gravitation developed so far can be divided into several main groups:
- standard;
- alternative;
- quantum;
- unified field theory.
Attempts to create a new concept of universal gravitation were made as early as the 19th century. Various authors included in it the ether or the corpuscular theory of light. But the emergence of general relativity put an end to these researches. After its publication, the goal of scientists changed - now their efforts were aimed at improving the Einstein model, including new natural phenomena in it: the spin of particles, the expansion of the Universe, etc.
By the beginning of the 1980s, physicists had experimentally rejected all concepts, except for those that included general relativity as an integral part. At this time, "string theories" came into fashion, looking very promising. But experimental confirmation of these hypotheses has not been found. Over the past decades, science has reached significant heights and has accumulated a huge array of empirical data. Today, attempts to create alternative theories of gravity are inspired mainly by cosmological studies related to such concepts as "dark matter", "inflation", "dark energy".
One of the main tasks of modern physics is the unification of two fundamental directions: quantum theory and general relativity. Scientists seek to connect attraction with other types of interactions, thus creating a "theory of everything." This is exactly what quantum gravity does, the branch of physics that attempts to give a quantum description of the gravitational interaction. An offshoot of this direction is the theory of loop gravity.
Despite active and long-term efforts, this goal has not yet been achieved. And it's not even the complexity of this problem: it's just that quantum theory and general relativity are based on completely different paradigms. Quantum mechanics deals with physical systems operating against the background of ordinary space-time. And in the theory of relativity, space-time itself is a dynamic component that depends on the parameters of the classical systems that are in it.
Along with the scientific hypotheses of universal gravitation, there are theories that are very far from modern physics. Unfortunately, in recent years, such "opuses" have simply flooded the Internet and the shelves of bookstores. Some authors of such works generally inform the reader that gravity does not exist, and the laws of Newton and Einstein are inventions and hoaxes.
An example is the work of the "scientist" Nikolai Levashov, who claims that Newton did not discover the law of universal gravitation, and only the planets and our satellite the Moon have gravitational force in the solar system. The evidence given by this "Russian scientist" is rather strange. One of them is the flight of the American probe NEAR Shoemaker to the asteroid Eros, which took place in 2000. Levashov considers the lack of attraction between the probe and the celestial body to be evidence of the falsity of Newton's works and the conspiracy of physicists who hide the truth about gravity from people.
In fact, the spacecraft successfully completed its mission: first, it entered the asteroid's orbit, and then made a soft landing on its surface.
Artificial gravity and what it is for
There are two concepts associated with gravity that, despite their current theoretical status, are well known to the general public. These are anti-gravity and artificial gravity.
Antigravity is the process of countering the force of attraction, which can significantly reduce it or even replace it with repulsion. The mastery of such technology would lead to a real revolution in transportation, aviation, space exploration and radically change our whole life. But at present, the possibility of antigravity does not even have theoretical confirmation. Moreover, proceeding from general relativity, such a phenomenon is not feasible at all, since there can be no negative mass in our Universe. It is possible that in the future we will learn more about gravity and learn how to build aircraft based on this principle.
Artificial gravity is a man-made change in the existing force of gravity. Today, we do not really need such technology, but the situation will definitely change after the start of long-term space travel. And it has to do with our physiology. The human body, “accustomed” by millions of years of evolution to the constant gravity of the Earth, perceives the impact of reduced gravity extremely negatively. A long stay even in the conditions of lunar gravity (six times weaker than the earth) can lead to sad consequences. The illusion of attraction can be created using other physical forces, such as inertia. However, these options are complex and expensive. At the moment, artificial gravity does not even have theoretical justifications, it is obvious that its possible practical implementation is a matter of a very distant future.
Gravity is a concept known to everyone since school. It would seem that scientists should have thoroughly investigated this phenomenon! But gravity remains the deepest mystery to modern science. And this can be called an excellent example of how limited human knowledge about our vast and wonderful world is.
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Gravity, also known as attraction or gravitation, is a universal property of matter that all objects and bodies in the Universe possess. The essence of gravity is that all material bodies attract to themselves all other bodies that are around.
Gravity
If gravity is a general concept and quality that all objects in the Universe possess, then the earth's attraction is a special case of this all-encompassing phenomenon. The earth attracts to itself all the material objects that are on it. Thanks to this, people and animals can safely move around the earth, rivers, seas and oceans can remain within their shores, and air can not fly through the vast expanses of the Cosmos, but form the atmosphere of our planet.
A fair question arises: if all objects have gravity, why does the Earth attract people and animals to itself, and not vice versa? Firstly, we also attract the Earth to ourselves, it's just that compared to its force of attraction, our gravity is negligible. Secondly, the force of gravity is directly proportional to the mass of the body: the smaller the mass of the body, the lower its gravitational forces.
The second indicator on which the force of attraction depends is the distance between objects: the greater the distance, the less the effect of gravity. Including due to this, the planets move in their orbits, and do not fall on each other.
It is noteworthy that the Earth, the Moon, the Sun and other planets owe their spherical shape precisely to the force of gravity. It acts in the direction of the center, pulling towards it the substance that makes up the "body" of the planet.
Earth's gravitational field
The gravitational field of the Earth is a force energy field that is formed around our planet due to the action of two forces:
- gravity;
- centrifugal force, which owes its appearance to the rotation of the Earth around its axis (daily rotation).
Since both gravity and centrifugal force act constantly, the gravitational field is also a constant phenomenon.
The gravitational forces of the Sun, the Moon and some other celestial bodies, as well as the atmospheric masses of the Earth, have an insignificant effect on the field.
Law of gravity and Sir Isaac Newton
The English physicist, Sir Isaac Newton, according to a well-known legend, once walking in the garden during the day, saw the moon in the sky. At the same time, an apple fell from the branch. Newton was then studying the law of motion and knew that an apple falls under the influence of a gravitational field, and the Moon revolves in an orbit around the Earth.
And then the thought came to the mind of a brilliant scientist, illuminated by insight, that perhaps the apple falls to the earth, obeying the same force due to which the Moon is in its orbit, and does not rush randomly throughout the galaxy. This is how the law of universal gravitation, also known as Newton's Third Law, was discovered.
In the language of mathematical formulas, this law looks like this:
F=GMm/D2 ,
where F- force of mutual gravitation between two bodies;
M- mass of the first body;
m- mass of the second body;
D2- distance between two bodies;
G- gravitational constant, equal to 6.67x10 -11.
To the question "What is power?" physics answers as follows: "Force is a measure of the interaction of material bodies with each other or between bodies and other material objects - physical fields." All forces in nature can be attributed to four fundamental types of interactions: strong, weak, electromagnetic and gravitational. Our article talks about what gravitational forces are - a measure of the last and, perhaps, the most widespread type of these interactions in nature.
Let's start with the attraction of the earth
Everyone living knows that there is a force that pulls objects to the ground. It is commonly referred to as gravity, gravity, or terrestrial attraction. Thanks to its presence, a person has the concepts of "up" and "down", which determine the direction of movement or location of something relative to the earth's surface. So in a particular case, on the surface of the earth or near it, gravitational forces manifest themselves, which attract objects with mass to each other, manifesting their action at any, both the smallest and very large, even by cosmic standards, distances.
Gravity and Newton's third law
As you know, any force, if it is considered as a measure of the interaction of physical bodies, is always applied to one of them. So in the gravitational interaction of bodies with each other, each of them experiences such types of gravitational forces that are caused by the influence of each of them. If there are only two bodies (it is assumed that the action of all others can be neglected), then each of them, according to Newton's third law, will attract another body with the same force. Thus, the Moon and the Earth attract each other, resulting in the ebb and flow of the earth's seas.
Each planet in the solar system experiences several forces of attraction from the Sun and other planets at once. Of course, it is the gravitational force of the Sun that determines the shape and size of its orbit, but astronomers also take into account the influence of other celestial bodies in their calculations of their trajectories.
What will fall to the ground faster from a height?
The main feature of this force is that all objects fall to the ground at the same speed, regardless of their mass. Once, until the 16th century, it was believed that the opposite was true - heavier bodies should fall faster than light ones. To dispel this misconception, Galileo Galilei had to perform his famous experiment of simultaneously dropping two cannonballs of different weights from the inclined Leaning Tower of Pisa. Contrary to the expectations of the witnesses of the experiment, both nuclei reached the surface at the same time. Today, every schoolchild knows that this happened due to the fact that gravity gives any body the same free fall acceleration g = 9.81 m / s 2, regardless of the mass m of this body, and its value, according to Newton's second law, is F = mg.
The gravitational forces on the Moon and on other planets have different values of this acceleration. However, the nature of the action of gravity on them is the same.
Gravity and body weight
If the first force is applied directly to the body itself, then the second to its support or suspension. In this situation, elastic forces always act on the bodies from the side of supports and suspensions. Gravitational forces applied to the same bodies act towards them.
Imagine a weight suspended above the ground on a spring. Two forces are applied to it: the elastic force of a stretched spring and the force of gravity. According to Newton's third law, the load acts on the spring with a force equal and opposite to the elastic force. This strength will be its weight. For a load weighing 1 kg, the weight is P \u003d 1 kg ∙ 9.81 m / s 2 \u003d 9.81 N (newton).
Gravitational forces: definition
The first quantitative theory of gravity, based on observations of the motion of the planets, was formulated by Isaac Newton in 1687 in his famous Principles of Natural Philosophy. He wrote that the attractive forces that act on the Sun and the planets depend on the amount of matter they contain. They propagate over long distances and always decrease as the reciprocal of the square of the distance. How can these gravitational forces be calculated? The formula for the force F between two objects with masses m 1 and m 2 located at a distance r is:
- F \u003d Gm 1 m 2 / r 2,
where G is the constant of proportionality, the gravitational constant.
The physical mechanism of gravity
Newton was not completely satisfied with his theory, since it involved interaction between gravitating bodies at a distance. The great Englishman himself was convinced that there must be some physical agent responsible for transferring the action of one body to another, about which he spoke quite clearly in one of his letters. But the time when the concept of a gravitational field was introduced, which permeates all space, came only after four centuries. Today, speaking of gravity, we can talk about the interaction of any (cosmic) body with the gravitational field of other bodies, the measure of which is the gravitational forces arising between each pair of bodies. The law of universal gravitation, formulated by Newton in the above form, remains true and is confirmed by many facts.
Gravity theory and astronomy
It was very successfully applied to solving problems in celestial mechanics during the 18th and early 19th centuries. For example, mathematicians D. Adams and W. Le Verrier, analyzing the violations of the orbit of Uranus, suggested that gravitational forces of interaction with a still unknown planet act on it. They indicated its supposed position, and soon the astronomer I. Galle discovered Neptune there.
There was one problem though. Le Verrier calculated in 1845 that Mercury's orbit precesses 35"" per century, in contrast to Newton's zero precession. Subsequent measurements gave a more accurate value of 43"". (The observed precession is indeed 570""/century, but a painstaking calculation to subtract influence from all other planets yields a value of 43"".)
It was not until 1915 that Albert Einstein was able to explain this inconsistency in terms of his theory of gravity. It turned out that the massive Sun, like any other massive body, bends space-time in its vicinity. These effects cause deviations in the orbits of the planets, but Mercury, as the smallest and closest planet to our star, they manifest themselves most strongly.
Inertial and gravitational masses
As noted above, Galileo was the first to observe that objects fall to the ground at the same speed, regardless of their mass. In Newton's formulas, the concept of mass comes from two different equations. His second law says that the force F applied to a body with mass m gives an acceleration according to the equation F = ma.
However, the force of gravity F applied to a body satisfies the formula F = mg, where g depends on another body interacting with the one under consideration (of the earth, usually when we talk about gravity). In both equations, m is a proportionality factor, but in the first case it is inertial mass, and in the second it is gravitational, and there is no obvious reason that they should be the same for any physical object.
However, all experiments show that this is indeed the case.
Einstein's theory of gravity
He took the fact of equality of inertial and gravitational masses as a starting point for his theory. He was able to construct the equations of the gravitational field, the famous equations of Einstein, and with their help calculate the correct value for the precession of the orbit of Mercury. They also give a measured value for the deflection of light rays that pass near the Sun, and there is no doubt that the correct results for macroscopic gravity follow from them. Einstein's theory of gravity, or general relativity (GR) as he called it, is one of the greatest triumphs of modern science.
Gravitational forces are acceleration?
If you cannot distinguish between inertial mass and gravitational mass, then you cannot distinguish between gravity and acceleration. An experiment in a gravitational field can instead be performed in a rapidly moving elevator in the absence of gravity. When an astronaut in a rocket accelerates, moving away from the earth, he experiences a force of gravity that is several times greater than that of the earth, and the vast majority of it comes from acceleration.
If no one can distinguish gravity from acceleration, then the former can always be reproduced by acceleration. A system in which acceleration replaces gravity is called inertial. Therefore, the Moon in near-Earth orbit can also be considered as an inertial system. However, this system will differ from point to point as the gravitational field changes. (In the Moon example, the gravitational field changes direction from one point to another.) The principle that it is always possible to find an inertial frame at any point in space and time in which physics obeys the laws in the absence of gravity is called the principle of equivalence.
Gravity as a manifestation of the geometric properties of space-time
The fact that gravitational forces can be viewed as accelerations in inertial coordinate systems that differ from point to point means that gravity is a geometric concept.
We say that space-time is curved. Consider a ball on a flat surface. It will rest or, if there is no friction, move uniformly in the absence of any forces acting on it. If the surface is curved, the ball will accelerate and move to the lowest point, taking the shortest path. Similarly, Einstein's theory states that four-dimensional space-time is curved, and the body moves in this curved space along a geodesic line, which corresponds to the shortest path. Therefore, the gravitational field and the gravitational forces acting in it on physical bodies are geometric quantities that depend on the properties of space-time, which change most strongly near massive bodies.