The theory of gravity, an interaction between matter.Among the four basic interactions of matter known today, gravity is the weakest.The four interactions are in the order of action intensity ratio:Strong interaction(1)，Electromagnetic interaction(10)，Weak interaction(10)，Gravitational interaction(10)。Therefore, when studying the motion of elementary particles, gravity is generally ignored.However, in the field of astronomy, due to the extremely large mass of the objects involved, gravity becomes not only the dominant factor in the movement of celestial bodies, but also often the decisive factor in the structure and evolution of celestial bodies.
Law of universal gravitation, a law of interaction between objects, 1687NewtonFound.All objects have mutual attraction. The force is proportional to the mass of each object and inversely proportional to the square of the distance between them.If m1 and m2 are used to represent the mass of two objects, and r is the distance between them, then the mutual attraction between objects is f=(gm1m2)/r2, and g is calledUniversal gravitational constant。The law of universal gravitation was published by Newton in 1687《Mathematical Principles of Natural Philosophy》First proposed in the book.Newton used the law of universal gravitation not only to explain the laws of planetary motion, but also pointed out that Jupiter and Saturn also have the same laws of motion around the planet.He believes that the moon is not only attracted by the earth, but also by the sun, thus explaining the double average deviation and business trip that have been found long ago in the movement of the moon.In addition, he also explained the orbit of comets and the tide phenomenon on the earth.According to the law of universal gravitation, he successfully predicted and discovered Neptune.After the emergence of the law of universal gravitation, the research on the movement of celestial bodies was formally established on the basis of the theory of mechanics, thus creating celestial mechanics.In short, the greater the mass, the greater the gravity generated. The gravity generated by the mass of the earth is enough to hold everything on the earth firmly.[1]
theoretical development
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Universal Gravity Explains Gravitational Action between Cosmic Celestial Bodies
In 1859,Leverrier Found onMercury perihelion precession problemIn 1882, there were parts that Newton's theory could not explain,newcon It is determined that the difference is 43 ″ per hundred years, which cannot be ignored.Some people speculate that this may be due to the so-calledAquatic planetsCaused by the attraction of;Some people tried to modifyNewton's law of universal gravitationThe inverse square law in the, but all failed.
In 1905,EinsteinproposeSpecial relativity, breaking through the concepts of absolute time and absolute space, denying the instantaneous action of over distance, and fundamentally shaking Newton's theory of gravity based on these old concepts.After about ten years of exploration, Einstein put forward the most successful modern theory of gravity so far in 1915 -General relativity。
General relativity
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Einstein and the Theory of Gravity
The basic starting point of general relativity is that in the gravitational field, all free falling objects have the same acceleration in a small range.In other words, the gravitational mass of any object is equal to its inertial mass.This is fromGalileoThe facts that have been known since the era were verified by Hungarian physicist Efou at the end of the 19th century to the accuracy of 10-9 (since the 1960s, the accuracy of this experiment has been improved to 10 and 11).Based on this, Einstein proposed the principle of equivalence of uniform gravitational field and uniform acceleration reference system (seePrinciple of equivalence）, and the principle that all natural laws should be covariant under arbitrary coordinate transformation (commonly referred to as the general relativity principle).
The basic content of general relativity is: three-dimensional space and one-dimensional time constitute four-dimensional space-time continuum;Physical events are represented by points in the four-dimensional space-time continuum;The geometric properties of four-dimensional space-time continuum areRiemannian Geometry Description.The metric tensor and curvature of space can be determined byGravitational field equation, determined by the energy momentum tensor of matter.The gravitational field equation can be written as:
WhereRμvIs Richie tensor,RIs scalar curvature,gμvIs the metric tensor,TμvIs the energy momentum tensor of matter,GIs the gravitational constant (seeSpatial curvature、Curved space、Gauge）。
Astrophysics (gravitational phenomena)
The free particles in the gravitational field move along the geodesic line in the four-dimensional space-time continuum.The differential equation of geodesic is:
In the formula, τ is the original time, which is the contact.
General relativity overcomes the difficulties encountered by Newton's law of universal gravitation and perfectly explains the precession of Mercury's perihelion;It is predicted that the light will deflect in the gravitational field;Compared with the same spectral line emitted by the same atom in the weak gravitational field, the spectral line emitted by the atom in the strong gravitational field moves towards the red end.These effects have been confirmed by observation and experiments to varying degrees (see astronomical verification of general relativity).
Although general relativity has made great achievements, there are still some problems.For example, it has been proved that under some fairly general conditions, there will always be difficulties of physically unacceptable singularity and non renormability after quantization.Therefore, other theories of gravity have been proposed for decades.These theories can be roughly divided into two categories: one is gravity theory satisfying Lorentz covariance in flat space, and the other is metric gravity theory in curved space.After various tests, with very few exceptions, all these theories have been eliminated one by one.However, the gauge theory of gravity, based on the existence of local inertial frames, has attracted extensive attention.In terms of geometric properties of spacetime, this theory not only considers curvature, but also torsion;In terms of the properties of matter, not only energy, momentum, but also spin are considered.Like general relativity, it can not only withstand the test of current experiments and observations, but also overcome the singularity and reformulation difficulties.In this direction, the recently emerged supergravity theory has shown an attractive prospect of unifying the four basic interactions.
The essence of gravity theory
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Deep analysis of gravity,Gravitational waveThe essence of gravitational field and the unified overview of four basic forces
Two key points: 1. The relationship between gravity and other basic forces. Here, electromagnetic force is chosen as the breakthrough.2. The four basic forces are unified.
Moreover, in the physical universe book "Change", the understanding of the macro, especially the theory of relativity is much more than that of quantum mechanics.Therefore, it is necessary to increase the explanation of quantum mechanics.To support the repeatedly stressed view that Eisenhower's general relativity can be in harmony with the other three basic forces!
So we have many points to discuss, and the scope involved has reached an unprecedented level, which is why this topic is scary.If only the topic is scary, that's good.What is behind the topic is a headache for us human beings.Come into this magical world!
Of course, the topic we want to discuss in this chapter is based on the previous knowledge theory.First of all, philosophically, I said from the beginning that things are generally connected, and the connection is conditional.So how can the four basic forces of the universe not be interrelated?Is it not harmonious?
But why have we failed so many times and failed to unify the four basic forces.Every failure is the preparation for the next success.With more foreshadowing, new conditions and new ideas, the problem will be solved.
Gravitational theory
We now know that space-time is an integrated combination of time, matter and space.And the origin of gravity is space-time!That is to say, gravity is a space-time property.
All previous theories have not discussed who is the most important and fundamental of the four basic forces.In other words, gravity is the most fundamental and important force in my theory.
In addition to gravity, the other three forces have been unified in the gauge field theory.But in fact, gravity still has an effect on particles in the quantum field.But we usually think that this kind of gravitational effect is negligible within the scope of quantum mechanics, so we ignore it.
Obviously, this ignorance is not rigorous.It also believes that parity is not conserved,Uncertainty principleThe spontaneous breaking is related to gravity.Gravity acts as a "disturbance".
This shows that gravity is a fundamental force in the universe and a space-time property.Is there a broader force than this?No,That is to say, the other three forces are within the scope of space-time, and the fundamental embodiment of the nature of space-time is gravity.
From a philosophical perspective, when dealing with the relationship between various forces, we tend to analyze various phenomena and states with gravity as the main contradiction.The other three forces are considered as secondary contradictions.
Start with the latest research.First, let's see what gravitational waves are and how gravity is discovered.
Gravitational wave is a space-time ripple.It spreads outward from the radiation source in the form of waves, which transmit energy in the form of gravitational radiation.In 1916, Einstein predicted the existence of gravitational waves based on general relativity.The existence of gravitational waves is general relativityLorentz invarianceBecause it introduces the concept that the propagation speed of interaction is limited, that is, the speed of light.
In contrast, gravitational waves cannot exist in Newton's classical theory of gravity, because Newton's classical theory assumes that the interaction of matter propagates at an infinite speed.
On February 11, 2016, the LIGO Scientific Cooperation Organization and the Virgo cooperation team announced that they had used the advanced LIGO detector to detect the gravitational wave signal from the merger of two black holes for the first time.
Gravitational theory
In the early morning of June 16, 2016, the LIGO cooperation group announced that: at 03:38:53 (UTC) on December 26, 2015, two gravitational wave detectors located in Hanford District of the United States and Livingston, Louisiana, simultaneously detected a gravitational wave signal;This is the second gravitational wave signal detected by humans after LIGO detected the first gravitational wave signal on September 14, 2015.[2]
In order to give you a detailed understanding of the theory to be told later, it is necessary to understand the specific detection of gravitational waves.Let's use Dr. Liu Boyang's discussion in the above picture to show the composition.
The two masses are 26 and 39 solar masses respectivelyStellar black hole。Rotate each other, and finally merge.The merger of black holes produced a very large collision, so we observed gravitational waves far away from Earth.
This process is divided into three stages.
The first stage: the gravitational wave frequency of the two black holes starts from 30Hz, which is a relatively low frequency band in gravitational wave astronomy, but it means that the black holes have an orbital frequency of 15Hz.More specifically, these two black holes are 30 and 36 solar masses respectively.Each radius is about 100km, and the distance is about 1000km.Turn each other 15 times per second.
The second stage: when the two black holes merge, the gravitational wave frequency reaches 100Hz, and the orbital frequency is 50Hz, that is, 50 revolutions per second.By this time, the two black holes had almost become one, and the distance between the "centers" of the two black holes was about 200 kilometers.
The third stage: the combined black holes continue to distort and vibrate, forming a new, rotating black hole.The mass of this black hole is 63 solar masses.About three of the solar masses disappear in the collision and spread outward in the form of gravitational waves!
Return to the origin theory of gravity in Change - gravity is a space-time property.Space time is the space time of energy.So there is noMassive celestial bodyIn the case of disturbances, spatiotemporal ripples are difficult to detect.Although we are in time and space.There is a feeling of "not knowing the true face of Mount Lushan, but being born in this mountain".
Here again, it is emphasized that gravity is not generated by the curvature of space-time, but the nature of space-time - it is space-time that generates gravity!
Bending is an illusion.Because the back of space-time is curved, gravity can make space-time curved!But it's not the curvature of space and time that creates gravity!It is time and space energy that generates gravity!This is why all objects with mass have gravity.Because gravity is a kind of space-time property, any object with mass cannot break away from this space-time law.This is true from the macro level to the quantum level.
So it is obvious that gravitational waves are ripples of space-time, so what is a gravitational field?Space time is a gravitational field. Obviously, such gravitational field is a global field.This is fundamentally different from the existing definition of gravitational field.
In fact, it is not difficult to understand that gravity is a space-time property, and gravitational field is also a space-time property naturally.The difference between them is that space-time is online, surface and body, but they are all based on the same space-time nature!
So the definition of gravitational field is:Gravitational field is a global space-time property, and its field intensity is proportional to the distribution of energy and matter and the speed of motion.
Key words: global, material energy distribution, motion speed, proportional relationship.
The so-called global nature means that theoretically, the gravitational field is the property of the whole space-time, and its breadth means that there must be a gravitational field where space-time is located.
How to understand the distribution of material energy? The distribution of material energy is uneven in the whole space-time, and the intensity of gravitational field is naturally different.Although it is theoretically a global field, that is, it permeates the whole universe.However, starting from differential thinking, we can divide the whole field into N local fields due to the inhomogeneity of material energy.
However, it should be clear that this division is artificial and is intended to better study the theory of gravity.
Gravitational theory
What is the relationship between local field and local field?It is obviously proportional to the distribution of material energy and inversely proportional to the square of the distance between them.
Here we remind you that the transmission speed of gravity and gravitational field is the speed of light.This has been discussed in the previous chapter.
Many people may ask why the description of "inversely proportional to the square of distance" is not added to the definition of gravitational field, but such a description is added to the local gravitational field.As I said above, gravitational field should be a global field, which is a space-time property,.Only when you measure the gravity of specific objects, specific celestial bodies, and specific star clusters, can you distinguish their distance, that is, the distance between objects.That is, there are at least two particles, A and B.
In this way, we derive Newton's gravitational theorem: any two particles attract each other through the force in the direction of the centerline.The gravity is proportional to the product of their masses and inversely proportional to the square of their distance, independent of the chemical composition of the two objects and the type of medium between them.
The mathematical formula is expressed as: F=GMm/r ^ 2.G is the gravitational constant, equal to G=6.67 × 10 ⁻ ⁻ N · m ²/kg ².
Obviously, Newton's theory is a "static" gravity theory and an absolute space-time theory.Einstein's general theory of relativity is a "dynamic" theory of gravity and a theory of relative space-time.This is the advanced place of Aishi.
That is to say, Newton's theory of gravity has limitations and is not suitable for high-speed objects.Because of the relativistic effect, the mass of a highly moving object will increase.If Newton thought that the mass does not change with the speed of motion, then nature would not realize this.
This is why I redefine quality.It is to return the mass to the essence of energy.Then we use energy to define mass.That is:Mass is a physical property of an object in relative space-time. The amount of energy contained in an object is a measure of its mass.
In this way, the mass is always placed in the mass of relativistic space-time.Is Newton's theorem of universal gravitation wrong?In fact, we can't say that it is wrong. It is not accurate enough.This must be experienced in the process of human understanding the universe.
gravitational fieldThe origin of gravity is space-time.Gravitational waves are ripples of time and space.The concept of electromagnetic wave is proposed here.Gravitational waves are different from electromagnetic waves.Gravitational waves are ripples of time and space, and electromagnetic waves are generated by electromagnetic fields.Their relationship will be analyzed and discussed in detail later.
Now one of the biggest problems is that the origin of gravitational field, gravity and gravitational wave has been clarified.So we asked: Does the graviton exist??
The above describes the process of gravitational waves being detected.Black holes will lose several solar masses in the process of merging. These solar masses oscillate in the form of energy and are detected by us, namely gravitational waves.
That is to say, spacetime is also energy spacetime, and the origin of gravity and gravitational field is energy spacetime.It is a space-time property.Gravitational waves are caused by the huge changes in space and time, unlike electromagnetic waves.
The propagation of gravity does not need a medium, that is to say, the transmission of gravitational waves does not need a medium.Space time is a kind of energy space time, and the transmission of energy does not need a medium, which is why the transmission of gravity and gravitational waves does not need a medium.But they travel at the speed of light, not faster than light!
Gravitational theory
Otherwise, a rhetorical question will trap us. This rhetorical question is: if gravity, the propagation of gravitational waves is beyond the distance, that is to say, it does not take any time to propagate, then can humans still detect gravitational waves??It is obviously impossible!
Since the origin of gravity, gravitational waves and gravitational fields all return to energy space-time, the so-called graviton is the smallest unit of energy - the energy particle.
So what is the smallest unit of energy? Does it exist?The current research does not exist!That is to say, there is no minimum energy unit. There is no such definition!
Therefore, the exploration of gravitons needs to be cautious, and it is very likely that nothing will come of it.Because gravity is space-time.Time and space are energy time and space, and everything is the matter that constitutes energy time and space.
In other words, all particles in the quantum mechanical system also belong to energy.In this case, Einstein's general theory of relativity should be more compatible with the other three basic forces.That is to say, we need to establish an "energy field theory", which we will discuss in detail in the next chapter.
Finally, I would like to emphasize that since all material things are energy.In fact, the existing description of the unified theory has come out.That'sconservation of energy: Energy can neither be generated nor disappear out of thin air. It can only be transferred from one object to another, and the forms of energy can also be transformed into each other.
There are different expressions in different fields, as follows:
1. Conservative mechanical system
When only conservative forces do work, the system energy is expressed as mechanical energy, and the energy conservation (kinetic energy and potential energy) is specifically expressed asLaw of conservation of mechanical energy。
Energy is expressed as internal energy, heat and work. The expression of energy conservation is the first law of thermodynamics (heat can be transferred from one object to another, and can also be converted with mechanical energy or other energy, but the total value of energy remains unchanged in the conversion process).The expression is Q=△ U+W
2. Relativistic theory
In relativity, mass and energy can change each other.Considering the energy change caused by the mass change, the law of energy conservation still holds.In history, the law of conservation of energy in this case is also calledLaw of conservation of mass and energy。
In fluid mechanics, there is a boundary layer surface effect, also known as "Bernoulli effect".It means that when the fluid speed increases, the pressure on the interface between the object and the fluid will decrease, otherwise the pressure will increase. Bernoulli effect is the law of conservation of energy in fluid mechanics.Bernoulli discovered this phenomenon and successfully explained it, which led to the creation of fluid mechanics.
According to Lenz's Law, the magnetic field generated by induced current always hinders the change of magnetic flux of the original magnetic field. As a result of this obstruction, other forms of energy will be converted into electric energy in the process of electromagnetic induction, the induced current will form a loop, and then electric energy will be converted into other forms of energy.In other words, the essence of the relationship between the induced current and the original magnetic field revealed by Lenz's law is still the relationship between energy conversion, that is, the law of conservation of energy.
6. Chemistry
Law of conservation of mass: Before and after the chemical reaction, the total mass of the substances participating in the reaction is equal to the total mass of the substances generated after the reaction.This is called the law of conservation of mass
7. Classical mechanics
Nott's theorem connects symmetry with conserved quantity, which is very useful.It means that for every continuous symmetric transformation of the mechanical system, there is a conserved quantity corresponding to it.Symmetrical transformation means that the mechanical system remains unchanged under certain transformation.
Description: For the differentiable symmetry under each local action, there is a corresponding conservative current.
To be precise, the word "symmetry" in the above proposition refers to the covariance of physical laws under the action of one-dimensional Lie groups that meet certain technical requirements.The conservation law of physical quantity is usually expressed by continuity equation.
Formal proposition of the theorem only derives expression of the stream corresponding to a conserved physical quantity from invariance condition.This conserved quantity is called the Nott charge, and this flow is called the Nott flow.Nott flow is at most one divergence free vector field.
And absolute zero can not be reached, it means that all objects have energy!The profound expression of this knowledge is that gravity exists forever, and space-time exists forever.Therefore, Einstein and Hawking's theory of the finite universe is unreliable.
This article is excerpted from Chapter 31 of "Change", a popular science book on physics and the universe by an independent scholar, poet, writer, and founder of Chinese Studies
Bibliography
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Bergman, Zhou Qi and Hao Ping: Introduction to Relativity,Higher Education PressBeijing, 1961.(P.G.Bergmann,Introductionto the Theory of Relativity,Butterworths,London,1958.)
Weinberg, translated by Zou Zhenlong: Gravity and Cosmology, Science Press, Beijing, 1979.(S. Weinberg,Gravitation andCosmology,John Wiley and Sons,New York,1972.)
Y.B.Zeldovich and I. D. Novikov,RelativisticAstrophysics Vol. I, Univ. of Chicago Press,Chicago,1971.
