Law of gravitational attraction. Earth gravity
We first learn about the concept of gravity in school. There we are usually told that there is such an amazing force that holds everyone on Earth, and only thanks to it we do not fly into outer space and do not walk upside down. This is where the fun practically ends, because at school we are told only the most basic and simple things. In reality, there is a lot of debate about universal gravity, scientists propose new theories and ideas, and there are many more nuances than you can imagine. In this collection you will find several very interesting facts and theories about gravitational influence, which either were not included in the school curriculum, or they became known not so long ago.
10. Gravity is a theory, not a proven law.
There is a myth that gravity is a law. If you try to do online research on this topic, any search engine will offer you many links about Newton's Law of Universal Gravitation. However, in the scientific community, laws and theories are completely different concepts. A scientific law is an irrefutable fact based on confirmed data that clearly explains the essence of occurring phenomena. A theory, in turn, is a kind of idea with the help of which researchers try to explain certain phenomena.
If we describe gravitational interaction in scientific terms, it immediately becomes completely clear to a relatively literate person why universal gravity is considered in a theoretical plane, and not as a law. Since scientists still do not have the ability to study the gravitational forces of every planet, satellite, star, asteroid and atom in the Universe, we have no right to recognize universal gravity as a law.
The robotic Voyager 1 probe traveled 21 billion kilometers, but even at such a far distance from Earth, it barely left our planetary system. The flight lasted 40 years and 4 months, and during all this time the researchers did not receive much data to transfer thoughts about gravity from the theoretical field into the category of laws. Our Universe is too big, and we still know too little...
9. There are many gaps in the theory about gravity
We have already established that universal gravity is just a theoretical concept. Moreover, it turns out that this theory still has many gaps that clearly indicate its relative inferiority. Many inconsistencies have been noted not just within our solar system, but even here on Earth.
For example, according to the theory of universal gravity on the Moon, the gravitational force of the Sun should be felt much stronger than the gravity of the Earth. It turns out that the Moon should revolve around the Sun, and not around our planet. But we know that the Moon is our satellite, and for this, sometimes it’s enough just to raise your eyes to the night sky.
At school we were told about Isaac Newton, who had a fateful apple fall on his head, inspiring him with the idea of the theory of universal gravitation. Even Newton himself admitted that his theory had certain shortcomings. At one time, it was Newton who became the author of a new mathematical concept - fluxions (derivatives), which helped him in the formation of that very theory of gravitation. Fluxions may not sound so familiar to you, but in the end they have become firmly entrenched in the world of exact sciences.
Today, in mathematical analysis, the method of differential calculus is often used, based precisely on the ideas of Newton and his colleague Leibniz. However, this section of mathematics is also rather incomplete and not without its flaws.
8. Gravitational waves
Albert Einstein's general theory of relativity was proposed in 1915. Around the same time, the hypothesis of gravitational waves appeared. Until 1974, the existence of these waves remained purely theoretical.
Gravitational waves can be compared to ripples on the canvas of the space-time continuum, which appear as a result of large-scale events in the Universe. Such events could be a collision of black holes, changes in the rotation speed of a neutron star, or a supernova explosion. When something like this happens, gravitational forces spread across the space-time continuum, like ripples in water from a stone falling into it. These waves travel through the Universe at the speed of light. We don't see catastrophic events very often, so it takes us many years to detect gravitational waves. That's why it took scientists more than 60 years to prove their existence.
For almost 40 years, scientists have been studying the first evidence of gravitational waves. As it turns out, these ripples arise during the merger of a binary system of very dense and heavy gravitationally bound stars revolving around a common center of mass. Over time, the components of the binary star come closer together and their speed gradually decreases, as predicted by Einstein in his theory. The magnitude of gravitational waves is so small that in 2017 they were even awarded the Nobel Prize in Physics for their experimental detection.
7. Black holes and gravity
Black holes are one of the biggest mysteries in the Universe. They appear during the gravitational collapse of a fairly large star, which becomes a supernova. When a supernova explodes, a significant mass of stellar material is ejected into outer space. What is happening can provoke the formation of a space-time region in space in which the gravitational field becomes so strong that even light quanta are not able to leave this place (this black hole). It is not gravity itself that forms black holes, but it still plays a key role in observing and studying these regions.
It is the gravity of black holes that helps scientists detect them in the Universe. Because gravitational pull can be incredibly powerful, researchers can sometimes notice its effects on other stars or on the gases surrounding these regions. When a black hole sucks in gases, a so-called accretion disk is formed, in which matter is accelerated to such high speeds that it begins to produce intense radiation when heated. This glow can also be detected in the X-ray range. It was thanks to the accretion phenomenon that we were able to prove the existence of blacks (using special telescopes). It turns out that if it weren’t for gravity, we wouldn’t even know about the existence of black holes.
6. Theory about black matter and black energy
Photo: NASA
Approximately 68% of the Universe consists of dark energy, and 27% is reserved for dark matter. In theory. Despite the fact that in our world dark matter and dark energy have been allocated so much space, we know very little about them.
We presumably know that dark energy has a number of properties. For example, guided by Einstein's theory of gravity, scientists have suggested that dark energy is constantly expanding. By the way, scientists initially believed that Einstein’s theory would help them prove that over time, gravitational influence slows down the expansion of the Universe. However, in 1998, data obtained by the Hubble Space Telescope gave reason to believe that the Universe is expanding only at an increasing speed. At the same time, scientists came to the conclusion that the theory of gravity is not able to explain the fundamental phenomena occurring in our Universe. This is how the hypothesis about the existence of dark energy and dark matter appeared, designed to justify the acceleration of the expansion of the Universe.
5. Gravitons
Photo: pbs.org
At school we are told that gravity is a force. But it could also be something more... It is possible that gravity in the future will be considered as a manifestation of a particle called graviton.
Hypothetically, gravitons are massless elementary particles that emit a gravitational field. To date, physicists have not yet proven the existence of these particles, but they already have many theories about why these gravitons must certainly exist. One of these theories states that gravity is the only force (of the 4 fundamental forces of nature or interactions) that has not yet been associated with a single elementary particle or any structural unit.
Gravitons may exist, but recognizing them is incredibly difficult. Physicists suggest that gravitational waves consist of just these elusive particles. To detect gravitational waves, the researchers conducted many experiments, in one of which they used mirrors and lasers. An interferometric detector can help detect mirror displacements over even the most microscopic distances, but unfortunately it cannot detect changes associated with particles as tiny as gravitons. In theory, for such an experiment, scientists would need mirrors so heavy that if they collapsed, black holes could appear.
In general, it does not seem possible to detect or prove the existence of gravitons in the near future. For now, physicists are observing the Universe and hope that it is there that they will find answers to their questions and will be able to detect manifestations of gravitons somewhere outside of ground-based laboratories.
4. Theory of wormholes
Photo: space.com
Wormholes, wormholes or wormholes are another great mystery of the Universe. It would be cool to go into some kind of space tunnel and travel at the speed of light to get to another galaxy in the shortest possible time. These fantasies have been used more than once in science fiction thrillers. If there really are wormholes in the Universe, such jumps may be quite possible. At the moment, scientists have no evidence of the existence of wormholes, but some physicists believe that these hypothetical tunnels can be created by manipulating gravity.
Einstein's general theory of relativity allows for the possibility of mind-bending wormholes. Taking into account the work of the legendary scientist, another physicist, Ludwig Flamm, tried to describe how the force of gravity could distort time space in such a way that a new tunnel would form, a bridge between one region of the fabric of physical reality and another. Of course, there are other theories.
3. Planets also have a gravitational influence on the Sun
We already know that the gravitational field of the Sun affects all objects in our planetary system, and that is why they all revolve around our single star. By the same principle, the Earth is connected with the Moon, and that is why the Moon revolves around our home planet.
However, each planet and any other celestial body with sufficient mass in our solar system also has its own gravitational fields, which affect the Sun, other planets and all other space objects. The magnitude of the gravitational force exerted depends on the mass of the object and the distance between the celestial bodies.
In our solar system, it is thanks to gravitational interaction that all objects rotate in their given orbits. The strongest gravitational attraction, of course, is from the Sun. By and large, all celestial objects with sufficient mass have their own gravitational field and influence other objects with significant mass, even if they are located at a distance of several light years.
2. Microgravity
Photo: NASA
We have all seen more than once photographs of astronauts soaring through orbital stations or even going outside the spacecraft in special protective suits. You are probably accustomed to thinking that these scientists usually tumble in space without feeling any gravity, because there is none there. And you would be very wrong if so. There is gravity in space too. It is customary to call it microgravity, because it is almost imperceptible. It is thanks to microgravity that astronauts feel light as feathers and so freely float in space. If there were no gravity at all, the planets simply would not revolve around the Sun, and the Moon would have left Earth’s orbit long ago.
The further an object is from the center of gravity, the weaker the force of gravity. It is microgravity that operates on the ISS, because all objects there are much further from the Earth’s gravitational field than even you are right here now. Gravity weakens at other levels as well. For example, let's take one individual atom. This is such a tiny particle of matter that it also experiences a fairly modest gravitational force. As atoms combine into groups, this force, of course, increases.
1. Time travel
The idea of time travel has fascinated humanity for quite some time. Many theories, including the theory of gravity, give hope that such travel will actually one day become possible. According to one concept, gravity forms a certain bend in the space-time continuum, which forces all objects in the Universe to move along a curved trajectory. As a result, objects in space move slightly faster compared to objects on Earth. More precisely, here’s an example: the clocks on space satellites are 38 microseconds (0.000038 seconds) ahead of your home alarm clocks every day.
Since gravity causes objects to move faster in space than on Earth, astronauts can actually be considered time travelers as well. However, this journey is so insignificant that upon returning home neither the astronauts themselves nor their loved ones notice any fundamental difference. But this does not negate one very interesting question - is it possible to use gravitational influence for time travel, as shown in science fiction films?
You've probably heard that gravity is not a force. And it is true. However, this truth leaves many questions. For example, we usually say that gravity "pulls" objects. In physics class we were told that gravity pulls objects towards the center of the Earth. But how is this possible? How can gravity not be a force, but still attract objects?
The first thing to understand is that the correct term is "acceleration" and not "attraction". In fact, gravity does not attract objects at all, it deforms the space-time system (the system by which we live), objects follow the waves formed as a result of the deformation and can sometimes accelerate.
Thanks to Albert Einstein and his theory of relativity, we know that space-time changes under the influence of energy. And the most important part of this equation is mass. The energy of an object's mass causes spacetime to change. Mass bends spacetime, and the resulting bends channel energy. Thus, it is more accurate to think of gravity not as a force, but as a curvature of space-time. Just as a rubber coating is bent under a bowling ball, space-time is bent by massive objects.
Just as a car travels along a road with various curves and turns, objects move along similar curves and curves in space and time. And just as a car accelerates down a hill, massive objects create extreme curves in space and time. Gravity is capable of accelerating objects when they enter deep gravity wells. This path that objects follow through spacetime is called a "geodesic trajectory."
To better understand how gravity works and how it can accelerate objects, consider the location of the Earth and Moon relative to each other. The Earth is a fairly massive object, at least compared to the Moon, and our planet causes spacetime to bend. The Moon revolves around the Earth due to distortions in space and time caused by the mass of the planet. Thus, the Moon simply travels along the resulting bend in space-time, which we call an orbit. The moon does not feel any force acting on it, it simply follows a certain path that has arisen.
Don DeYoung
Gravity (or gravitation) keeps us firmly on the earth and allows the earth to revolve around the sun. Thanks to this invisible force, rain falls on the earth, and the water level in the ocean rises and falls every day. Gravity keeps the earth in a spherical shape and also prevents our atmosphere from escaping into outer space. It would seem that this force of attraction observed every day should be well studied by scientists. But no! In many ways, gravity remains the deepest mystery of science. This mysterious force is a remarkable example of how limited modern scientific knowledge is.
What is gravity?
Isaac Newton was interested in this issue as early as 1686 and came to the conclusion that gravity is the force of attraction that exists between all objects. He realized that the same force that makes the apple fall to the ground is in its orbit. In fact, the Earth's gravitational force causes the Moon to deviate from its straight path by about one millimeter every second as it orbits the Earth (Figure 1). Newton's Universal Law of Gravity is one of the greatest scientific discoveries of all time.
Gravity is the “rope” that holds objects in orbit
Picture 1. Illustration of the moon's orbit, not drawn to scale. Every second the moon travels approximately 1 km. Over this distance, it deviates from the straight path by about 1 mm - this occurs due to the gravitational pull of the Earth (dashed line). The moon constantly seems to fall behind (or around) the earth, just as the planets fall around the sun.
Gravity is one of the four fundamental forces of nature (Table 1). Note that of the four forces, this force is the weakest, and yet it is dominant relative to large space objects. As Newton showed, the attractive gravitational force between any two masses becomes smaller and smaller as the distance between them becomes larger and larger, but it never completely reaches zero (see "The Design of Gravity").
Therefore, every particle in the entire universe actually attracts every other particle. Unlike the forces of weak and strong nuclear interactions, the force of attraction is long-range (Table 1). The magnetic force and the electrical force are also long-range forces, but gravity is unique in that it is both long-range and always attractive, which means it can never run out (unlike electromagnetism, in which forces can either attract or repel).
Beginning with the great creation scientist Michael Faraday in 1849, physicists have continually searched for the hidden connection between the force of gravity and the force of electromagnetic interaction. Currently, scientists are trying to combine all four fundamental forces into one equation or the so-called “Theory of Everything”, but to no avail! Gravity remains the most mysterious and least studied force.
Gravity cannot be protected in any way. Whatever the composition of the blocking partition, it has no effect on the attraction between two separated objects. This means that it is impossible to create an anti-gravity chamber in laboratory conditions. The force of gravity does not depend on the chemical composition of objects, but depends on their mass, known to us as weight (the force of gravity on an object is equal to the weight of that object - the greater the mass, the greater the force or weight.) Blocks consisting of glass, lead, ice or even styrophoma, and having the same mass, will experience (and exert) the same gravitational force. These data were obtained during experiments, and scientists still do not know how they can be theoretically explained.
Design in gravity
The force F between two masses m 1 and m 2 located at a distance r can be written as the formula F = (G m 1 m 2)/r 2
Where G is the gravitational constant first measured by Henry Cavendish in 1798.1
This equation shows that gravity decreases as the distance, r, between two objects becomes greater, but never completely reaches zero.
The inverse square law nature of this equation is simply fascinating. After all, there is no necessary reason why gravity should act as it does. In a disorderly, random, and evolving universe, arbitrary powers such as r 1.97 or r 2.3 would seem more likely. However, precise measurements showed an exact power, to at least five decimal places, of 2.00000. As one researcher said, this result seems "too precise".2 We can conclude that the force of gravity indicates a precise, created design. In fact, if the degree deviated even a little from 2, the orbits of the planets and the entire universe would become unstable.
Links and notes
- Technically speaking, G = 6.672 x 10 –11 Nm 2 kg –2
- Thompsen, D., "Very Accurate About Gravity", Science News 118(1):13, 1980.
So what exactly is gravity? How is this force able to operate in such a vast, empty space? And why does it even exist? Science has never been able to answer these basic questions about the laws of nature. The force of attraction cannot arise slowly through mutation or natural selection. It has been in effect since the very beginning of the universe. Like every other physical law, gravity is undoubtedly a remarkable evidence of planned creation.
Some scientists have tried to explain gravity using invisible particles, gravitons, that move between objects. Others talked about cosmic strings and gravitational waves. Recently, scientists using a specially created LIGO laboratory (Laser Interferometer Gravitational-Wave Observatory) were only able to see the effect of gravitational waves. But the nature of these waves, how physically objects interact with each other over vast distances, changing their head start, still remains a big question for everyone. We simply do not know the origin of the gravitational force and how it maintains the stability of the entire universe.
Gravity and Scripture
Two passages from the Bible can help us understand the nature of gravity and physical science in general. The first passage, Colossians 1:17, explains that Christ “there is first of all, and everything depends on Him”. The Greek verb stands (συνισταω sunistao) means: to adhere, to hold, or to be held together. The Greek use of this word outside the Bible means a vessel containing water. The word used in the book of Colossians is in the perfect tense, which generally indicates a present ongoing state that has arisen from a completed past action. One of the physical mechanisms in question is clearly the force of gravity, established by the Creator and unfailingly maintained today. Just imagine: if the force of gravity were to cease for a moment, chaos would undoubtedly ensue. All celestial bodies, including the earth, moon and stars, would no longer be held together. Everything would immediately be divided into separate, small parts.
The second Scripture, Hebrews 1:3, declares that Christ “He holds up all things by the word of his power.” Word holds (φερω pherō) again describes the support or preservation of everything, including gravity. Word holds, as used in this verse, means much more than just holding weight. It involves control over all the movements and changes that occur within the universe. This endless task is carried out through the omnipotent Word of the Lord, through which the universe itself began to exist. Gravity, a “mysterious force” that remains poorly understood after four hundred years of research, is one manifestation of this amazing divine care for the universe.
Distortions of time and space and black holes
Einstein's general theory of relativity views gravity not as a force, but as the curvature of space itself near a massive object. Light, which traditionally follows straight lines, is predicted to be bent as it passes through curved space. This was first demonstrated when astronomer Sir Arthur Eddington discovered a change in the apparent position of a star during a total eclipse in 1919, believing that light rays were being bent by the sun's gravity.
General relativity also predicts that if a body is dense enough, its gravity will distort space so much that light cannot pass through it at all. Such a body absorbs light and everything else that is captured by its strong gravity, and is called a Black Hole. Such a body can only be detected by its gravitational effects on other objects, by the strong bending of light around it, and by the strong radiation emitted by the matter that falls on it.
All matter inside a black hole is compressed at the center, which has infinite density. The “size” of the hole is determined by the event horizon, i.e. a boundary that surrounds the center of a black hole, and nothing (not even light) can escape beyond it. The radius of the hole is called the Schwarzschild radius, after the German astronomer Karl Schwarzschild (1873–1916), and is calculated by the formula RS = 2GM/c 2, where c is the speed of light in vacuum. If the sun were to fall into a black hole, its Schwarzschild radius would be only 3 km.
There is good evidence that once a massive star's nuclear fuel runs out, it can no longer resist collapsing under its own enormous weight and falls into a black hole. Black holes with the mass of billions of suns are thought to exist at the centers of galaxies, including our own galaxy, the Milky Way. Many scientists believe that super-bright and very distant objects called quasars harness the energy released when matter falls into a black hole.
According to the predictions of general relativity, gravity also distorts time. This has also been confirmed by very accurate atomic clocks, which run a few microseconds slower at sea level than in areas above sea level, where Earth's gravity is slightly weaker. Near the event horizon this phenomenon is more noticeable. If we watch an astronaut's watch as he approaches the event horizon, we will see that the clock is running slower. Once inside the event horizon, the clock will stop, but we will never be able to see it. Conversely, an astronaut will not notice that his clock is running slower, but he will see that our clock is running faster and faster.
The main danger for an astronaut near a black hole would be tidal forces caused by the fact that gravity is stronger on parts of the body that are closer to the black hole than on parts further away from it. The power of tidal forces near a black hole with the mass of a star is stronger than any hurricane and easily tears into small pieces everything that comes their way. However, while gravitational attraction decreases with the square of distance (1/r 2), tidal influence decreases with the cube of distance (1/r 3). Therefore, contrary to conventional wisdom, the gravitational force (including tidal force) at the event horizons of large black holes is weaker than at small black holes. So tidal forces at the event horizon of a black hole in observable space would be less noticeable than the mildest breeze.
The stretching of time by gravity near the event horizon is the basis of creation physicist Dr. Russell Humphreys' new cosmological model, which he describes in his book Starlight and Time. This model may help solve the problem of how we can see the light of distant stars in the young universe. In addition, today it is a scientific alternative to the non-biblical one, which is based on philosophical assumptions that go beyond the scope of science.
Note
Gravity, a “mysterious force” that, even after four hundred years of research, remains poorly understood...
Isaac Newton (1642–1727)
Photo: Wikipedia.org
Isaac Newton (1642–1727)
Isaac Newton published his discoveries about gravity and the motion of celestial bodies in 1687, in his famous work " Mathematical principles" Some readers quickly concluded that Newton's universe left no room for God, since everything could now be explained using equations. But Newton did not think so at all, as he said in the second edition of this famous work:
“Our most beautiful solar system, planets and comets can only be the result of the plan and dominion of an intelligent and powerful being.”
Isaac Newton was not only a scientist. In addition to science, he devoted almost his entire life to the study of the Bible. His favorite Bible books were the book of Daniel and the book of Revelation, which describe God's plans for the future. In fact, Newton wrote more theological works than scientific ones.
Newton was respectful of other scientists such as Galileo Galilei. By the way, Newton was born in the same year that Galileo died, in 1642. Newton wrote in his letter: “If I saw further than others, it was because I stood on shoulders giants." Shortly before his death, probably reflecting on the mystery of gravity, Newton modestly wrote: “I don’t know how the world perceives me, but to myself I seem only like a boy playing on the seashore, who amuses himself by occasionally finding a pebble more colorful than the others, or a beautiful shell, while a huge an ocean of unexplored truth."
Newton is buried in Westminster Abbey. The Latin inscription on his grave ends with the words: “Let mortals rejoice that such an adornment of the human race lived among them.”.
Even a person who is not interested in space has at least once seen a film about space travel or read about such things in books. In almost all such works, people walk around the ship, sleep normally, and do not have problems eating. This means that these - fictional - ships have artificial gravity. Most viewers perceive this as something completely natural, but this is not at all the case.
Artificial gravity
This is the name for changing (in any direction) the gravity that is familiar to us through the use of various methods. And this is done not only in science fiction works, but also in very real earthly situations, most often for experiments.
In theory, creating artificial gravity doesn't look that difficult. For example, it can be recreated using inertia, or more precisely, the need for this force did not arise yesterday - it happened immediately, as soon as a person began to dream of long-term space flights. Creating artificial gravity in space will make it possible to avoid many problems that arise during prolonged periods of weightlessness. Astronauts' muscles weaken and bones become less strong. Traveling in such conditions for months can cause atrophy of some muscles.
Thus, today the creation of artificial gravity is a task of paramount importance; without this skill it is simply impossible.
Materiel
Even those who know physics only at the school curriculum level understand that gravity is one of the fundamental laws of our world: all bodies interact with each other, experiencing mutual attraction/repulsion. The larger the body, the higher its gravitational force.
The Earth for our reality is a very massive object. That is why all the bodies around her, without exception, are attracted to her.
For us, this means, which is usually measured in g, equal to 9.8 meters per square second. This means that if we had no support under our feet, we would fall at a speed that increases by 9.8 meters every second.
Thus, only thanks to gravity we are able to stand, fall, eat and drink normally, understand where is up and where is down. If gravity disappears, we will find ourselves in weightlessness.
Cosmonauts who find themselves in space in a state of soaring—free fall—are especially familiar with this phenomenon.
Theoretically, scientists know how to create artificial gravity. There are several methods.
Large mass
The most logical option is to make it so large that artificial gravity appears on it. You will be able to feel comfortable on the ship, since orientation in space will not be lost.
Unfortunately, this method is unrealistic with modern technology development. To build such an object requires too many resources. In addition, lifting it would require an incredible amount of energy.
Acceleration
It would seem that if you want to achieve a g equal to that on Earth, you just need to give the ship a flat (platform-like) shape and make it move perpendicular to the plane with the required acceleration. In this way, artificial gravity will be obtained, and ideal gravity at that.
However, in reality everything is much more complicated.
First of all, it is worth considering the fuel issue. In order for the station to constantly accelerate, it is necessary to have an uninterruptible power supply. Even if an engine suddenly appears that does not eject matter, the law of conservation of energy will remain in force.
The second problem is the very idea of constant acceleration. According to our knowledge and physical laws, it is impossible to accelerate indefinitely.
In addition, such a vehicle is not suitable for research missions, since it must constantly accelerate - fly. He will not be able to stop to study the planet, he will not even be able to fly around it slowly - he must accelerate.
Thus, it becomes clear that such artificial gravity is not yet available to us.
Carousel
Everyone knows how the rotation of a carousel affects the body. Therefore, an artificial gravity device based on this principle seems to be the most realistic.
Everything that is within the diameter of the carousel tends to fall out of it at a speed approximately equal to the speed of rotation. It turns out that the bodies are acted upon by a force directed along the radius of the rotating object. It's very similar to gravity.
So, a ship with a cylindrical shape is required. At the same time, it must rotate around its axis. By the way, artificial gravity on a spaceship, created according to this principle, is often demonstrated in science fiction films.
A barrel-shaped ship, rotating around its longitudinal axis, creates a centrifugal force, the direction of which corresponds to the radius of the object. To calculate the resulting acceleration, you need to divide the force by the mass.
In this formula, the result of the calculation is acceleration, the first variable is the nodal speed (measured in radians per second), the second is the radius.
According to this, to obtain the g we are accustomed to, it is necessary to correctly combine the radius of space transport.
A similar problem is highlighted in films such as Intersolah, Babylon 5, 2001: A Space Odyssey and the like. In all these cases, artificial gravity is close to the earth's acceleration due to gravity.
No matter how good the idea is, it is quite difficult to implement it.
Problems with the carousel method
The most obvious problem is highlighted in A Space Odyssey. The radius of the “space carrier” is about 8 meters. In order to get an acceleration of 9.8, the rotation must occur at a speed of approximately 10.5 revolutions every minute.
At these values, the “Coriolis effect” appears, which consists in the fact that different forces act at different distances from the floor. It directly depends on the angular velocity.
It turns out that artificial gravity will be created in space, but rotating the body too quickly will lead to problems with the inner ear. This, in turn, causes balance disorders, problems with the vestibular apparatus and other - similar - difficulties.
The emergence of this obstacle suggests that such a model is extremely unsuccessful.
You can try to go from the opposite, as they did in the novel “The Ring World”. Here the ship is made in the shape of a ring, the radius of which is close to the radius of our orbit (about 150 million km). At this size, its rotation speed is sufficient to ignore the Coriolis effect.
You might assume that the problem has been solved, but this is not the case at all. The fact is that a full revolution of this structure around its axis takes 9 days. This suggests that the loads will be too great. In order for the structure to withstand them, a very strong material is needed, which we do not have at our disposal today. In addition, the problem is the amount of material and the construction process itself.
In games of similar themes, as in the film “Babylon 5”, these problems are somehow solved: the rotation speed is quite sufficient, the Coriolis effect is not significant, hypothetically it is possible to create such a ship.
However, even such worlds have a drawback. Its name is angular momentum.
The ship, rotating around its axis, turns into a huge gyroscope. As you know, it is extremely difficult to force a gyroscope to deviate from its axis due to the fact that it is important that its quantity does not leave the system. This means that it will be very difficult to give direction to this object. However, this problem can be solved.
Solution
Artificial gravity on the space station becomes available when the O'Neill Cylinder comes to the rescue. To create this design, identical cylindrical ships are needed, which are connected along the axis. They should rotate in different directions. The result of such an assembly is zero angular momentum, so there should be no difficulty in giving the ship the required direction.
If it is possible to make a ship with a radius of about 500 meters, then it will work exactly as it should. At the same time, artificial gravity in space will be quite comfortable and suitable for long flights on ships or research stations.
Space Engineers
The creators of the game know how to create artificial gravity. However, in this fantasy world, gravity is not the mutual attraction of bodies, but a linear force designed to accelerate objects in a given direction. The attraction here is not absolute; it changes when the source is redirected.
Artificial gravity on the space station is created by using a special generator. It is uniform and equidirectional in the range of the generator. So, in the real world, if you got under a ship with a generator installed, you would be pulled towards the hull. However, in the game the hero will fall until he leaves the perimeter of the device.
Today, artificial gravity in space created by such a device is inaccessible to humanity. However, even gray-haired developers do not stop dreaming about it.
Spherical generator
This is a more realistic equipment option. When installed, gravity is directed towards the generator. This makes it possible to create a station whose gravity will be equal to the planetary one.
Centrifuge
Today, artificial gravity on Earth is found in various devices. They are based, for the most part, on inertia, since this force is felt by us in a similar way to gravitational influence - the body does not distinguish what cause causes acceleration. As an example: a person going up in an elevator experiences the influence of inertia. Through the eyes of a physicist: the rise of the elevator adds the acceleration of the cabin to the acceleration of free fall. When the cabin returns to measured movement, the “gain” in weight disappears, returning the usual sensations.
Scientists have long been interested in artificial gravity. A centrifuge is most often used for these purposes. This method is suitable not only for spacecraft, but also for ground stations where it is necessary to study the effects of gravity on the human body.
Study on Earth, apply in...
Although the study of gravity began in space, it is a very terrestrial science. Even today, advances in this area have found their application, for example, in medicine. Knowing whether it is possible to create artificial gravity on a planet, it can be used to treat problems with the musculoskeletal system or the nervous system. Moreover, the study of this force is carried out primarily on Earth. This makes it possible for astronauts to conduct experiments while remaining under the close attention of doctors. Artificial gravity in space is another matter; there are no people there who can help the astronauts in the event of an unforeseen situation.
Bearing in mind complete weightlessness, one cannot take into account a satellite located in low-Earth orbit. These objects, albeit to a small extent, are affected by gravity. The force of gravity generated in such cases is called microgravity. Real gravity is experienced only in a vehicle flying at a constant speed in outer space. However, the human body does not feel this difference.
You can experience weightlessness during a long jump (before the canopy opens) or during a parabolic descent of the aircraft. Such experiments are often carried out in the USA, but on an airplane this sensation lasts only 40 seconds - this is too short for a full study.
In the USSR, back in 1973, they knew whether it was possible to create artificial gravity. And they not only created it, but also changed it in some way. A striking example of an artificial reduction in gravity is dry immersion, immersion. To achieve the desired effect, you need to place a thick film on the surface of the water. The person is placed on top of it. Under the weight of the body, the body sinks under water, leaving only the head above. This model demonstrates the support-free, low-gravity nature of the ocean.
There is no need to go into space to experience the opposite force of weightlessness - hypergravity. When a spacecraft takes off and lands in a centrifuge, the overload can not only be felt, but also studied.
Gravity treatment
Gravitational physics also studies the effects of weightlessness on the human body, trying to minimize the consequences. However, a large number of achievements of this science can also be useful to ordinary inhabitants of the planet.
Doctors place great hopes on research into the behavior of muscle enzymes in myopathy. This is a serious disease leading to early death.
During active physical exercise, a large volume of the enzyme creatine phosphokinase enters the blood of a healthy person. The reason for this phenomenon is unclear; perhaps the load affects the cell membrane in such a way that it becomes “holey.” Patients with myopathy get the same effect without exercise. Observations of astronauts show that in weightlessness the flow of active enzyme into the blood is significantly reduced. This discovery suggests that the use of immersion will reduce the negative impact of factors leading to myopathy. Experiments on animals are currently being carried out.
Treatment of some diseases is already carried out using data obtained from the study of gravity, including artificial gravity. For example, treatment of cerebral palsy, strokes, and Parkinson's is carried out through the use of stress suits. Research into the positive effects of the support, the pneumatic shoe, has almost been completed.
Will we fly to Mars?
The latest achievements of astronauts give hope for the reality of the project. There is experience in providing medical support to a person during a long stay away from Earth. Research flights to the Moon, whose gravitational force is 6 times less than our own, have also brought a lot of benefits. Now astronauts and scientists are setting themselves a new goal - Mars.
Before queuing up for a ticket to the Red Planet, you should know what awaits the body already at the first stage of work - on the way. On average, the road to the desert planet will take a year and a half - about 500 days. Along the way you will have to rely only on your own strength; there is simply nowhere to wait for help.
Many factors will undermine your strength: stress, radiation, lack of a magnetic field. The most important test for the body is a change in gravity. During the journey, a person will become “acquainted” with several levels of gravity. First of all, these are overloads during takeoff. Then - weightlessness during the flight. After this - hypogravity at the destination, since the gravity on Mars is less than 40% of the Earth's.
How do you cope with the negative effects of weightlessness on a long flight? It is hoped that developments in the field of artificial gravity will help solve this issue in the near future. Experiments on rats traveling on Cosmos 936 show that this technique does not solve all problems.
OS experience has shown that the use of training complexes that can determine the required load for each astronaut individually can bring much greater benefits to the body.
For now, it is believed that not only researchers will fly to Mars, but also tourists who want to establish a colony on the Red Planet. For them, at least for the first time, the sensations of being in weightlessness will outweigh all the arguments of doctors about the dangers of prolonged stay in such conditions. However, in a few weeks they will also need help, which is why it is so important to be able to find a way to create artificial gravity on the spaceship.
Results
What conclusions can be drawn about the creation of artificial gravity in space?
Among all the options currently being considered, the rotating structure looks the most realistic. However, with the current understanding of physical laws, this is impossible, since the ship is not a hollow cylinder. There are overlaps inside that interfere with the implementation of ideas.
In addition, the radius of the ship must be so large that the Coriolis effect does not have a significant effect.
To control something like this, you need the O'Neill cylinder mentioned above, which will give you the ability to control the ship. In this case, the chances of using such a design for interplanetary flights while providing the crew with a comfortable level of gravity are increased.
Before humanity succeeds in making its dreams come true, I would like to see a little more realism and even more knowledge of the laws of physics in science fiction works.
The most important phenomenon constantly studied by physicists is movement. Electromagnetic phenomena, laws of mechanics, thermodynamic and quantum processes - all this is a wide range of fragments of the universe studied by physics. And all these processes come down, one way or another, to one thing - to.
In contact with
Everything in the Universe moves. Gravity is a common phenomenon for all people since childhood; we were born in the gravitational field of our planet; this physical phenomenon is perceived by us at the deepest intuitive level and, it would seem, does not even require study.
But, alas, the question is why and how do all bodies attract each other, remains to this day not fully disclosed, although it has been studied far and wide.
In this article we will look at what universal attraction is according to Newton - the classical theory of gravity. However, before moving on to formulas and examples, we will talk about the essence of the problem of attraction and give it a definition.
Perhaps the study of gravity became the beginning of natural philosophy (the science of understanding the essence of things), perhaps natural philosophy gave rise to the question of the essence of gravity, but, one way or another, the question of the gravitation of bodies became interested in ancient Greece.
Movement was understood as the essence of the sensory characteristic of the body, or rather, the body moved while the observer saw it. If we cannot measure, weigh, or feel a phenomenon, does this mean that this phenomenon does not exist? Naturally, it doesn't mean that. And since Aristotle understood this, reflections began on the essence of gravity.
As it turns out today, after many tens of centuries, gravity is the basis not only of gravity and the attraction of our planet to, but also the basis for the origin of the Universe and almost all existing elementary particles.
Movement task
Let's conduct a thought experiment. Let's take a small ball in our left hand. Let's take the same one on the right. Let's release the right ball and it will begin to fall down. The left one remains in the hand, it is still motionless.
Let's mentally stop the passage of time. The falling right ball “hangs” in the air, the left one still remains in the hand. The right ball is endowed with the “energy” of movement, the left one is not. But what is the deep, meaningful difference between them?
Where, in what part of the falling ball is it written that it should move? It has the same mass, the same volume. It has the same atoms, and they are no different from the atoms of a ball at rest. Ball has? Yes, this is the correct answer, but how does the ball know what has potential energy, where is it recorded in it?
This is precisely the task that Aristotle, Newton and Albert Einstein set themselves. And all three brilliant thinkers partly solved this problem for themselves, but today there are a number of issues that require resolution.
Newton's gravity
In 1666, the greatest English physicist and mechanic I. Newton discovered a law that can quantitatively calculate the force due to which all matter in the Universe tends to each other. This phenomenon is called universal gravity. When you are asked: “Formulate the law of universal gravitation,” your answer should sound like this:
The force of gravitational interaction contributing to the attraction of two bodies is located in direct proportion to the masses of these bodies and in inverse proportion to the distance between them.
Important! Newton's law of attraction uses the term "distance". This term should be understood not as the distance between the surfaces of bodies, but as the distance between their centers of gravity. For example, if two balls of radii r1 and r2 lie on top of each other, then the distance between their surfaces is zero, but there is an attractive force. The thing is that the distance between their centers r1+r2 is non-zero. On a cosmic scale, this clarification is not important, but for a satellite in orbit, this distance is equal to the height above the surface plus the radius of our planet. The distance between the Earth and the Moon is also measured as the distance between their centers, not their surfaces.
For the law of gravity the formula is as follows:
,
- F – force of attraction,
- – masses,
- r – distance,
- G – gravitational constant equal to 6.67·10−11 m³/(kg·s²).
What is weight, if we just looked at the force of gravity?
Force is a vector quantity, but in the law of universal gravitation it is traditionally written as a scalar. In a vector picture, the law will look like this:
.
But this does not mean that the force is inversely proportional to the cube of the distance between the centers. The relation should be perceived as a unit vector directed from one center to another:
.
Law of Gravitational Interaction
Weight and gravity
Having considered the law of gravity, one can understand that it is not surprising that we personally we feel the Sun's gravity much weaker than the Earth's. Although the massive Sun has a large mass, it is very far from us. is also far from the Sun, but it is attracted to it, since it has a large mass. How to find the gravitational force of two bodies, namely, how to calculate the gravitational force of the Sun, the Earth and you and me - we will deal with this issue a little later.
As far as we know, the force of gravity is:
where m is our mass, and g is the acceleration of free fall of the Earth (9.81 m/s 2).
Important! There are not two, three, ten types of attractive forces. Gravity is the only force that gives a quantitative characteristic of attraction. Weight (P = mg) and gravitational force are the same thing.
If m is our mass, M is the mass of the globe, R is its radius, then the gravitational force acting on us is equal to:
Thus, since F = mg:
.
The masses m are reduced, and the expression for the acceleration of free fall remains:
As we can see, the acceleration of gravity is truly a constant value, since its formula includes constant quantities - the radius, the mass of the Earth and the gravitational constant. Substituting the values of these constants, we will make sure that the acceleration of gravity is equal to 9.81 m/s 2.
At different latitudes, the radius of the planet is slightly different, since the Earth is still not a perfect sphere. Because of this, the acceleration of free fall at individual points on the globe is different.
Let's return to the attraction of the Earth and the Sun. Let's try to prove with an example that the globe attracts you and me more strongly than the Sun.
For convenience, let’s take the mass of a person: m = 100 kg. Then:
- The distance between a person and the globe is equal to the radius of the planet: R = 6.4∙10 6 m.
- The mass of the Earth is: M ≈ 6∙10 24 kg.
- The mass of the Sun is: Mc ≈ 2∙10 30 kg.
- Distance between our planet and the Sun (between the Sun and man): r=15∙10 10 m.
Gravitational attraction between man and Earth:
This result is quite obvious from the simpler expression for weight (P = mg).
The force of gravitational attraction between man and the Sun:
As we can see, our planet attracts us almost 2000 times stronger.
How to find the force of attraction between the Earth and the Sun? In the following way:
Now we see that the Sun attracts our planet more than a billion billion times stronger than the planet attracts you and me.
First escape velocity
After Isaac Newton discovered the law of universal gravitation, he became interested in how fast a body must be thrown so that it, having overcome the gravitational field, leaves the globe forever.
True, he imagined it a little differently, in his understanding it was not a vertically standing rocket aimed at the sky, but a body that horizontally made a jump from the top of a mountain. This was a logical illustration because At the top of the mountain the force of gravity is slightly less.
So, at the top of Everest, the acceleration of gravity will not be the usual 9.8 m/s 2 , but almost m/s 2 . It is for this reason that the air there is so thin, the air particles are no longer as tied to gravity as those that “fell” to the surface.
Let's try to find out what escape velocity is.
The first escape velocity v1 is the speed at which the body leaves the surface of the Earth (or another planet) and enters a circular orbit.
Let's try to find out the numerical value of this value for our planet.
Let's write down Newton's second law for a body that rotates around a planet in a circular orbit:
,
where h is the height of the body above the surface, R is the radius of the Earth.
In orbit, a body is subject to centrifugal acceleration, thus:
.
The masses are reduced, we get:
,
This speed is called the first escape velocity:
As you can see, escape velocity is absolutely independent of body mass. Thus, any object accelerated to a speed of 7.9 km/s will leave our planet and enter its orbit.
First escape velocity
Second escape velocity
However, even having accelerated the body to the first escape velocity, we will not be able to completely break its gravitational connection with the Earth. This is why we need a second escape velocity. When this speed is reached the body leaves the planet's gravitational field and all possible closed orbits.
Important! It is often mistakenly believed that in order to get to the Moon, astronauts had to reach the second escape velocity, because they first had to “disconnect” from the gravitational field of the planet. This is not so: the Earth-Moon pair are in the Earth’s gravitational field. Their common center of gravity is inside the globe.
In order to find this speed, let's pose the problem a little differently. Let's say a body flies from infinity to a planet. Question: what speed will be reached on the surface upon landing (without taking into account the atmosphere, of course)? This is exactly the speed the body will need to leave the planet.
The law of universal gravitation. Physics 9th grade
Law of Universal Gravitation.
Conclusion
We learned that although gravity is the main force in the Universe, many of the reasons for this phenomenon still remain a mystery. We learned what Newton's force of universal gravitation is, learned to calculate it for various bodies, and also studied some useful consequences that follow from such a phenomenon as the universal law of gravity.