Obi-Wan Kenobi said that strength holds the galaxy together. The same can be said about gravity. Fact: Gravity allows us to walk on the Earth, the Earth to revolve around the Sun, and the Sun to move around the supermassive black hole at the center of our galaxy. How to understand gravity? This is discussed in our article.
Let us say right away that you will not find here a uniquely correct answer to the question “What is gravity.” Because it simply doesn't exist! Gravity is one of the most mysterious phenomena, over which scientists are puzzling 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 look at the most interesting, relevant and modern ones.
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Gravity is a physical fundamental interaction
There are 4 fundamental interactions in physics. Thanks to them, the world is exactly what it is. Gravity is one of these interactions.
Fundamental interactions:
- gravity;
- electromagnetism;
- strong interaction;
- weak interaction.
Currently, the current theory describing gravity is GTR (general relativity). It was proposed by Albert Einstein in 1915-1916.
However, we know that the truth in last resort It's too early to say. After all, several centuries before the appearance of general relativity in physics, Newton’s theory dominated to describe gravity, which was significantly expanded.
Within the framework of general relativity, it is currently impossible to explain and describe all issues related to gravity.
Before Newton, it was widely believed that gravity on earth and gravity in heaven were different things. It was believed that the planets move according to their own ideal laws, different from those on Earth.
Newton discovered the law universal gravity in 1667. Of course, this law existed even during the time of dinosaurs and much earlier.
Ancient philosophers thought about the existence of gravity. Galileo experimentally calculated the acceleration of gravity on Earth, discovering that it is the same for bodies of any mass. Kepler studied the laws of motion of celestial bodies.
Newton managed to formulate and generalize the results of his observations. Here's what he got:
Two bodies attract each other with a force called gravitational force or gravity.
Formula for the force of attraction between bodies:
G is the gravitational constant, m is the mass of bodies, r is the distance between the centers of mass of 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 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 a 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 gravity, but establishes quantitative laws. Newton's theory does not contradict GTR. It is quite sufficient for solving practical problems on an Earth scale 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 disadvantages. The law of universal gravitation is a mathematical description, but does not provide insight into the fundamental physical nature of things.
According to Newton, the force of gravity 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 instantly at any distance, when it takes light 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.
Let's imagine space in the form of an elastic sheet. If you place a light tennis ball on it, the surface will remain level. But if you place a heavy weight next to the ball, it will press a hole on the surface, and the ball will begin to roll towards the large, 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 discovered only 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 appear on the surface of the water from where it falls. Gravitational waves are the same ripples, disturbances. Just not on the water, but in world space-time.
Instead of water there is space-time, and instead of a stone, say, a black hole. Any accelerated movement of mass generates a gravitational wave. If the bodies are in a state of free fall, when a gravitational wave passes, the distance between them will change.
Since gravity is a very weak force, detecting gravitational waves has been associated with great technical difficulties. Modern technologies made it possible to detect a burst of gravitational waves only from supermassive sources.
A suitable event for detecting 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 across the space of the Universe.
To record gravitational waves, a detector with a diameter of 4 kilometers was built. During the passage of the wave, vibrations of mirrors on suspensions in a 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, a hypothetical massless particle with energy, is responsible for gravity. By the way, in our separate material, read more about the Higgs boson, which has caused a lot of noise, and other elementary particles.
Finally, here are some interesting facts about gravity.
10 facts about gravity
- To overcome the force of Earth's gravity, a body must have a speed of 7.91 km/s. This is the first escape velocity. It is enough for a body (for example, a space probe) to move in orbit around the planet.
- To escape from the Earth's gravitational field, spaceship must have a speed of at least 11.2 km/s. This is the second escape velocity.
- The 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 issues 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 himself on Jupiter, the scales will show 142 kilograms.
- NASA scientists are trying to develop a gravity beam that will allow objects to be moved without contact, overcoming the force of gravity.
- Astronauts in orbit also experience gravity. More precisely, microgravity. They seem to fall endlessly along with the ship they are in.
- Gravity always attracts and never repels.
- The black hole, the size of a tennis ball, attracts objects with the same force as our planet.
Now you know the definition of gravity and can tell what formula is used to calculate the force of attraction. If the granite of science is pressing you to the ground stronger than gravity, contact our student service. We will help you study easily under the heaviest loads!
Gravity is the “curvature” of space. The greater the mass, the greater the “curvature” of space and, consequently, lighter objects “roll” into this “curvature.” All objects orbiting the Sun are held in their orbits by gravity. But it not only functions as a kind of tether, but also became the force that created these objects. The force of gravity does not allow the planets to choose the path of their own choosing, looping their orbits. But the dependence on this force decreases exponentially - when removed by two times, the impact is weakened by four times, and tripling the removal weakens the force by nine times.
Newton directly associated gravity with gravity. A force of gravity is applied to the body, the source of which is another body (or bodies), and the gravitational field, as such, simply does not exist. Since gravity refers to the direct interaction of bodies, it is determined by the Law of Universal Gravitation. The gravitational field is given a conditional character, necessary only for calculations. For terrestrial conditions this is quite acceptable.
Gravity from Einstein
Aristotle described the gravitational influence. He believed that the speed at which an object falls depends on its mass. But only Galileo was able to understand that any body has an equal acceleration value. And Einstein developed this statement in his theory of relativity, describing gravity with the concept of the geometry of space-time.
In the classical representation, the force of gravitational interaction between two points has the form of a dependence of the mass of these points on the distance squared between them. The larger the body, the greater the gravitational field it can create.
Although gravity is a very weak interaction, its effect extends to any distance.
Gravitational attraction is universal in its effect on matter; there are no objects that do not have it. Einstein postulated that gravitational effects are caused not by the force influences of a body or field located in space-time, but by changes in space-time itself. All this happens due to the presence of mass-energy. According to Einstein's theory, mass and energy are a single parameter of bodies. They are connected by a well-known formula: E = m c² Two massive bodies, interacting with each other, will bend space. But why this curvature occurs, Einstein could not give an answer. Gravity, due to its global nature, is responsible for large-scale phenomena. These are structures, the expanding Universe. But also simple facts astronomy - planetary orbits, gravity, falling bodies - are also dependent on gravity.
Celestial Mechanics
This part of mechanics studies the movement of bodies located in empty space, which are acted only by gravity. The simplest task of the section is to substantiate the gravitational influence of two bodies, point or spherical, in empty space. If there are more bodies that interact with each other, the task becomes more complicated. The numerical solution leads to instability of solutions from initial conditions. That is, if we apply it to our planetary system, we will not be able to predict planetary movements for periods exceeding one hundred million years. It is not yet possible to describe the long-term behavior of a system consisting of many attracting bodies with similar masses. This is hindered by the concept: dynamic chaos.
Gravitational waves
Gravitational waves are changes in the gravitational field that propagate like waves. They are emitted by moving masses, but after radiation they are separated from them and exist independently of these masses. Mathematically related to the perturbation of spacetime metrics and can be described as "spacetime ripples". Gravitational waves are predicted by general relativity. They were first directly detected in September 2015 by LIGO's twin detectors, which detected gravitational waves likely produced by two black holes merging to form a single, more massive, rotating black hole.
Graviton
Since gravitational interaction is present, it must be transferred somehow. In the 1930s, graviton became a candidate carrier. This particle is still hypothetical, but it should have a spin of 2 and two possible directions of polarization. Some physicists stubbornly deny the existence of this particle. They suggest: if there are gravitons, then they should be emitted by black holes, and this conflicts with general relativity. But attempts to extend the standard model with such particles pose real challenges at high energies. Some theories of quantum gravity being developed are based on solving this problem. According to their positions, gravitons are the state of strings, and are by no means point particles. But low energies still classify them as point particles. So far, gravitons have not been discovered because their gravitational influences are unusually weak.
Quantum gravity
A universal quantum theory that would explain the very concept of gravity has not yet been developed. To represent the gravitational interaction, it would be plausible to propose a graviton exchange in which gravitons act as spin-2 gauge bosons. But such a theory is not considered satisfactory. On existing time There are several approaches that allow gravity to be quantized. These approaches are considered quite promising.
- String theory. It replaces space-time background particles with branes (like strings). To solve multidimensional problems, branes are seen as already multidimensional particles, but at the same time they are structures of space-time. Gravitons here become states of strings rather than individual particles. Although low energies are considered one of them.
- Loop quantum gravity. Here time and space are discrete parts. They are not tied to the background of space-time, being quantum spatial cells. They are connected to each other in such a way that on small time scales they appear as a discrete structure of space. When enlarging the scale, the parts smoothly become continuous space-time. Loop gravity can describe the essence of the Big Bang, as well as shed light on its threshold. This even allows you to do without attracting.
Strong gravitational fields
In very strong gravitational fields there may be manifestations of some effects of general relativity:
- the law of gravity deviates from Newton's
- gravitational waves appear
- there are nonlinearity effects
- visible spacetime changes its geometry
- the appearance of singularities and the birth of black holes is possible.
But such manifestations can only take place if gravity has an infinitely greater force. So far, the densest objects in the Universe that have been discovered are. In one of many theories, the gravitational field is considered as the basis for any field - magnetic, electric, gluon. In this case, gravitons become the basic elements of matter. Well, a black hole is graviton, where the force of gravity destroys absolutely all elementary particles, except gravitons. And only one property remains - gravity.
Gravitational collapse
When a massive body, experiencing gravitational forces, is compressed catastrophically quickly, it collapses. This is how the life of a star with a mass of more than three times the sun can end. When stars run out of fuel to continue the thermonuclear process, their mechanical stability is disrupted and rapid, accelerated compression occurs towards the central part. If the pressure inside the star, which is constantly growing, can stop the compression, then the central part of the star will turn into a neutron star. In this case, the shell may be shed and a supernova may erupt. But if the star exceeds the mass determined by the Oppenheimer-Volkov limit, the collapse will end with its transformation into a black hole. The value of this limit has not yet been precisely established.
Some paradoxes
- A satellite revolving around the Earth is weightless in relation to the planet. And everything that is in it is also weightless. , relatively, is again weightless, but the bodies on its surface already have weight. It's the same with the Earth. It is relatively weightless, but we feel the weight on it. The Sun is also weightless relative to the galactic core. And so on ad infinitum.
- In stars, during thermonuclear reactions, enormous pressure is created. But it is restrained by gravitational forces. That is, the existence of a star is possible because there is a dynamic equilibrium: temperature-pressure - gravitational forces.
- In a black hole, all processes cease except one - gravity. Nothing can absorb or distort it.
Despite the fact that gravity is the weakest interaction between objects in the Universe, its significance in physics and astronomy is enormous, since it can influence physical objects at any distance in space.
If you are interested in astronomy, you have probably wondered what such a concept as gravity or the law of universal gravitation is. Gravity is the universal fundamental interaction between all objects in the Universe.
The discovery of the law of gravity is attributed to the famous English physicist Isaac Newton. Probably many of you know the story of the apple that fell on the head of the famous scientist. However, if you look deeper into history, you can see that the presence of gravity was thought about long before his era by philosophers and scientists of antiquity, for example, Epicurus. However, it was Newton who first described the gravitational interaction between physical bodies within the framework of classical mechanics. His theory was developed by another famous scientist - Albert Einstein, who in his general theory relativity more accurately described the influence of gravity in space, as well as its role in the space-time continuum.
Newton's law of universal gravitation states that the force of gravitational attraction between two points of mass separated by a distance is inversely proportional to the square of the distance and directly proportional to both masses. The force of gravity is long-range. That is, regardless of how a body with mass moves, in classical mechanics its gravitational potential will depend purely on the position of this object at a given moment in time. The greater the mass of an object, the greater its gravitational field - the more powerful the gravitational force it has. Space objects such as galaxies, stars and planets have greatest strength attraction and, accordingly, sufficiently strong gravitational fields.
Gravitational fields
Earth's gravitational field
The gravitational field is the distance within which gravitational interaction occurs between objects in the Universe. The greater the mass of an object, the stronger its gravitational field - the more noticeable its impact on other physical bodies within a certain space. The gravitational field of an object is potential. The essence of the previous statement is that if you introduce the potential energy of attraction between two bodies, then it will not change after moving the latter along a closed loop. From here comes another famous law of conservation of the sum of potential and kinetic energy in a closed loop.
In the material world, the gravitational field is of great importance. It is possessed by all material objects in the Universe that have mass. The gravitational field can influence not only matter, but also energy. It is due to the influence of the gravitational fields of such large cosmic objects as black holes, quasars and supermassive stars that solar systems, galaxies and other astronomical clusters are formed, which are characterized by a logical structure.
Recent scientific data show that the famous effect of the expansion of the Universe is also based on the laws of gravitational interaction. In particular, the expansion of the Universe is facilitated by powerful gravitational fields, both of its small and largest objects.
Gravitational radiation in a binary system
Gravitational radiation or gravitational wave is a term first introduced into physics and cosmology by the famous scientist Albert Einstein. Gravitational radiation in the theory of gravitation is generated by the movement of material objects with variable acceleration. During the acceleration of an object, a gravitational wave seems to “break away” from it, which leads to oscillations of the gravitational field in the surrounding space. This is called the gravitational wave effect.
Although gravitational waves are predicted by Einstein's general theory of relativity as well as other theories of gravity, they have never been directly detected. This is due primarily to their extreme smallness. However, in astronomy there is indirect evidence that can confirm this effect. Thus, the effect of a gravitational wave can be observed in the example of the approach double stars. Observations confirm that the rate of convergence of double stars depends to some extent on the loss of energy from these cosmic objects, which is presumably spent on gravitational radiation. Scientists will be able to reliably confirm this hypothesis in the near future using the new generation of Advanced LIGO and VIRGO telescopes.
In modern physics, there are two concepts of mechanics: classical and quantum. Quantum mechanics was developed relatively recently and is fundamentally different from classical mechanics. In quantum mechanics, objects (quanta) do not have definite positions and velocities; everything here is based on probability. That is, an object can occupy a certain place in space at a certain point in time. Where he will move next cannot be reliably determined, but only with a high degree of probability.
An interesting effect of gravity is that it can bend the space-time continuum. Einstein's theory states that in the space around a bunch of energy or any material substance, space-time is curved. Accordingly, the trajectory of particles that fall under the influence of the gravitational field of this substance changes, which makes it possible to predict the trajectory of their movement with a high degree of probability.
Theories of gravity
Today scientists know over a dozen different theories of gravity. They are divided into classical and alternative theories. The most famous representative of the former is the classical theory of gravity by Isaac Newton, which was invented by the famous British physicist back in 1666. Its essence lies in the fact that a massive body in mechanics generates a gravitational field around itself, which attracts smaller objects. In turn, the latter also have a gravitational field, like any other material objects in the Universe.
The next popular theory of gravity was invented by the world famous German scientist Albert Einstein at the beginning of the 20th century. Einstein was able to more accurately describe gravity as a phenomenon, and also explain its action not only in classical mechanics, but also in the quantum world. His general theory of relativity describes the ability of a force such as gravity to influence the space-time continuum, as well as the trajectory of elementary particles in space.
Among the alternative theories of gravity, the relativistic theory, which was invented by our compatriot, the famous physicist A.A., perhaps deserves the greatest attention. Logunov. Unlike Einstein, Logunov argued that gravity is not a geometric, but a real, fairly strong physical force field. Among the alternative theories of gravity, scalar, bimetric, quasilinear and others are also known.
- For people who have been in space and returned to Earth, it is quite difficult at first to get used to the strength of the gravitational influence of our planet. Sometimes this takes several weeks.
- It has been proven that human body in a state of weightlessness can lose up to 1% of bone marrow mass per month.
- Among the planets in the solar system, Mars has the least gravitational force, and Jupiter has the greatest.
- The known salmonella bacteria, which cause intestinal diseases, behave more actively in a state of weightlessness and are capable of causing to the human body much more harm.
- Among all known astronomical objects in the Universe, black holes have the greatest gravitational force. A black hole the size of a golf ball could have the same gravitational force as our entire planet.
- The force of gravity on Earth is not the same in all corners of our planet. For example, in the Hudson Bay region of Canada it is lower than in other regions of the globe.
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. Gravity does not depend on chemical composition 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 styrofoam, 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 upholds 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 total eclipse in 1919, believing that light rays are 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 after a massive star runs out of nuclear fuel, 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 domination 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.”.
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.
