19 12 put forward the photochemical equivalence law.
191511month, and put forward the complete form of the general relativity gravity equation, which successfully explained the motion of Mercury's perihelion.
19 16 In March, I finished my summary paper "The Basis of General Relativity". In May, the hypothesis that the universe is finite and unbounded was put forward. In August, he completed the quantum theory of radiation, summarized the development of quantum theory and put forward the theory of stimulated radiation.
An American journalist once asked Einstein the secret of his success. He replied: "As early as 190 1, when I was a 22-year-old young man, I had discovered the formula of success. I can tell you the secret of this formula, that is, A=X+Y+Z! A is success, X is hard work, Y is knowing how to rest, and Z is talking less nonsense! This formula is useful to me and I think it is also useful to many people. "
The establishment of special relativity: As early as 16, Einstein learned from books that light is a very fast electromagnetic wave. He has an idea. If a person moves at the speed of light, what kind of world scene will he see? He will not see the advancing light, but only the electromagnetic field that oscillates in space but stagnates. Is this possible?
In connection with this, he would like to discuss the so-called ether problem related to light waves. The word ether comes from Greece and is used to represent the basic elements that make up objects in the sky. /kloc-Descartes introduced it into science for the first time in the 0/7th century as a medium for spreading light. Later, Huygens further developed the theory of ether, thinking that the medium carrying light waves is ether, which should fill all spaces including vacuum and penetrate into ordinary matter. Unlike Huygens, Newton put forward the particle theory of light. Newton believed that the luminous body emitted a stream of particles moving in a straight line, and the impact of the particle stream on the retina caused vision. Newton's particle theory prevailed in18th century, but the wave theory prevailed in19th century, and the theory of ether developed greatly. At that time, the view was that the propagation of waves depended on the medium, because light can propagate in a vacuum, and the medium that propagates light waves is the ether that fills the whole space, also called optical ether. At the same time, electromagnetism has developed vigorously. With the efforts of Maxwell, Hertz and others, a mature electromagnetic phenomena's dynamic theory-electrodynamics was formed, which unified light and electromagnetic phenomena in theory and practice, and regarded light as electromagnetic waves in a certain frequency range, thus unifying the wave theory of light and electromagnetic theory. Ether is not only the carrier of light waves, but also the carrier of electromagnetic fields. Until the end of 19, people tried to find ether, but they never found it in the experiment.
But electrodynamics has encountered a big problem, which is inconsistent with the relativity principle followed by Newtonian mechanics. The theory of relativity existed as early as Galileo and Newton. The development of electromagnetism was originally included in the framework of Newtonian mechanics, but it encountered difficulties in explaining the electromagnetic process of moving objects. According to Maxwell's theory, the speed of electromagnetic waves in vacuum, that is, the speed of light, is a constant. However, according to the principle of speed addition in Newtonian mechanics, the speed of light in different inertial systems is different, which leads to a question: Is the principle of relativity applicable to mechanics applicable to electromagnetism? For example, there are two cars, one is approaching you and the other is leaving. You see the lights in the front car approaching you and the lights in the back car are far away. According to Maxwell's theory, the speed of these two kinds of light is the same, and the speed of the car doesn't work in it. But according to Galileo's theory, the measurement results of these two items are different. The car coming towards you will accelerate the light, that is, the speed of light in front of the car = speed of light+speed; Light leaves the car more slowly, because the speed of light behind the car = speed of light-speed of light. Maxwell and Galileo's statements about speed are obviously opposite. How can we resolve this disagreement?
Theoretical physics reached its peak in the19th century, but it also implied a huge crisis. The discovery of Neptune shows the incomparable theoretical power of Newtonian mechanics. The unification of electromagnetism and mechanics makes physics present a formal integrity, which is known as "a solemn and majestic architectural system and a touching and beautiful palace". In people's minds, classical physics has reached the point of near perfection. Planck, a famous German physicist, told his teacher when he was young that he would devote himself to theoretical physics. The teacher advised him: "young man, physics is a completed science, and there will be no further development." It is a pity to dedicate his life to this subject. "
Einstein seems to be the man who is going to build a brand-new physics building. During his stay in Berne Patent Office, Einstein paid extensive attention to the frontier dynamics of physics, thought deeply about many problems and formed his own unique views. During ten years of exploration, Einstein studied Maxwell's electromagnetic theory seriously, especially the electrodynamics developed and expounded by Hertz and Lorenz. Einstein firmly believes that the electromagnetic theory is completely correct, but there is one problem that makes him uneasy, and that is the existence of the absolute reference frame ether. He read a lot of books and found that all the experiments that proved the existence of ether failed. After Einstein's research, it was found that ether had no practical significance in Lorentz theory except as an absolute reference system and the load of electromagnetic field. So he thought: Is the absolute frame of reference of the ether necessary? Do electromagnetic fields have to be loaded?
Einstein likes reading philosophical works and absorbing ideological nutrition from philosophy. He believes in the unity of the world and the consistency of logic. The principle of relativity has been widely proved in mechanics, but it cannot be established in electrodynamics. Einstein questioned the logical inconsistency between the two theoretical systems of physics. He believes that the principle of relativity should be universally established, so the electromagnetic theory should have the same form for each inertial system, but there is a problem of the speed of light here. Whether the speed of light is constant or variable becomes the primary question whether the principle of relativity is universally established. Physicists at that time generally believed in ether, that is, there was an absolute frame of reference, which was influenced by Newton's concept of absolute space. /kloc-At the end of 0/9, Mach criticized Newton's absolute view of time and space in Mechanics in Development, which left a deep impression on Einstein. 1905 One day in May, Einstein and a friend Bezo discussed the problem that had been explored for ten years. Bezo expounded his point of view according to Mahism, and they had a long discussion about it. Suddenly, Einstein realized something, went home and thought about it again and again, and finally figured it out. The next day, he came to Bezo's house again and said, thank you, my problem has been solved. It turned out that Einstein thought clearly about one thing: there is no absolute definition of time, and time is closely related to the speed of optical signals. He found the key to the lock, and after five weeks of hard work, Einstein showed people the special theory of relativity.
1905 On June 30th, the German Yearbook of Physics accepted Einstein's paper "On Electrodynamics of Moving Objects" and published it in September of the same year. This paper is the first article about special relativity, which contains the basic ideas and contents of special relativity. Special relativity is based on two principles: the principle of relativity and the principle of invariability of light speed. Einstein's starting point for solving problems is to firmly believe in the principle of relativity. Galileo first expounded the idea of relativity principle, but he did not give a clear definition of time and space. Newton also talked about relativity when he established the mechanical system, but he also defined absolute space, absolute time and absolute motion. He contradicts himself on this issue. Einstein greatly developed the principle of relativity. In his view, there is no absolute still space, and there is no absolute constant time. All time and space are connected with moving objects. For any reference system and coordinate system, there is only space and time belonging to this reference system and coordinate system. For all inertial systems, the physical laws expressed in space and time of the reference system are the same in form, which is the principle of relativity, strictly speaking, the principle of relativity in a narrow sense. In this article, Einstein did not discuss too much about taking the constant speed of light as the basis of the basic principle. It is a bold assumption that the speed of light is constant, which is put forward from the requirements of electromagnetic theory and the principle of relativity. This article is the result of Einstein's thinking about ether and electrodynamics for many years. At the same time, he established a brand-new space-time theory from the perspective of relativity, and gave a complete form of electrodynamics of moving objects on the basis of this new space-time theory. Ether is no longer necessary and ether drift does not exist.
What is the relativity of simultaneity? How do we know that events in two different places happen at the same time? Generally speaking, we will confirm by signal. In order to know the simultaneity of events in different places, we must know the speed of signal transmission, but how to measure this speed? We must measure the spatial distance between the two places and the time required for signal transmission. The measurement of spatial distance is simple, but the trouble lies in the measurement time. We must assume that every place has an aligned clock, and the propagation time of the signal can be known from the readings of the two clocks. But how do we know that the clocks in different places are right? The answer is that another signal is needed. Can this signal set the clock right? If we follow the previous thinking, it needs a new signal, so it will retreat indefinitely, and the simultaneity of different places cannot be confirmed. But one thing is clear, simultaneity must be associated with a signal, otherwise it is meaningless to say that these two things happen at the same time.
Optical signal may be the most suitable signal for a clock, but the speed of light is not infinite, which leads to a novel conclusion that two things happen at the same time for a stationary observer but not for a moving observer. Let's imagine a high-speed train, its speed is close to the speed of light. When the train passed the platform, A stood on the platform, and two lightning flashes appeared in front of A's eyes, one at the front end of the train and the other at the back end, leaving traces at both ends of the train and the corresponding parts of the platform. Through measurement, the distance between A and both ends of the train is equal, and the conclusion is that A saw two lightning flashes at the same time. Therefore, for A, two received optical signals travel the same distance in the same time interval and reach his position at the same time. These two things must happen at the same time, and at the same time. But for B in the center of the train, the situation is different, because B moves with the high-speed train, so he will intercept the front-end signal that propagates to him first, and then receive the optical signal at the back end. For B, these two events are different at the same time. In other words, simultaneity is not absolute, but depends on the observer's motion state. This conclusion denies the framework of absolute time and absolute space based on Newtonian mechanics.
Relativity holds that the speed of light is constant in all inertial reference frames, and it is the maximum speed at which an object moves. Due to the relativistic effect, the length of the moving object will become shorter and the time of the moving object will expand. However, due to the problems encountered in daily life, the speed of motion is very low (compared with the speed of light) and the relativistic effect cannot be seen.
Einstein established relativistic mechanics on the basis of completely changing the concept of time and space, pointing out that the mass increases with the increase of speed, and when the speed approaches the speed of light, the mass tends to infinity. He also gave a famous mass-energy relation: e = MC 2, which played a guiding role in the later development of atomic energy.
The establishment of general relativity;
1905, Einstein published his first article on the special theory of relativity, which did not immediately arouse great repercussions. But Planck, the authority of German physics, noticed his article and thought that Einstein's work could be comparable to Copernicus's. It is precisely because of Planck's promotion that relativity quickly became a topic of research and discussion, and Einstein also attracted the attention of academic circles.
1907, Einstein listened to his friend's advice and submitted the famous paper, and applied for the position of supernumerary lecturer at Federal Institute of Technology, but the answer was that the paper was incomprehensible. Although Einstein is very famous in the German physics field, in Switzerland, he can't find a teaching post in a university, and many famous people began to complain about him. 1908, Einstein finally got the position of supernumerary lecturer and became an associate professor the following year. 19 12 years, Einstein became a professor, 19 13 years, at the invitation of Planck, he became the director of the newly established Institute of Physics of Emperor William and a professor at Berlin University.
At the same time, Einstein is considering expanding the accepted theory of relativity. For him, there are two problems that make him uneasy. The first is the problem of gravity. Special relativity is correct for the physical laws of mechanics, thermodynamics and electrodynamics, but it cannot explain the problem of universal gravitation. Newton's theory of gravity is beyond distance, and the gravitational interaction between two objects is instantaneous, that is, at infinite speed, which conflicts with the view of field on which relativity is based and the limit of light speed. The second problem is the non-inertial system, and the special theory of relativity, like the previous physical laws, only applies to the inertial system. But in fact, it is difficult to find the real inertial system. Logically speaking, all natural laws should not be limited to inertial systems, and non-inertial systems must also be considered. It is difficult for special relativity to explain the so-called twin paradox. Paradoxically, there are two twins. My brother is traveling near the speed of light in a spaceship. According to the effect of relativity, the high-speed clock slows down. When my brother came back, he was very old, because the earth had gone through decades. According to the principle of relativity, the spacecraft moves at a high speed relative to the earth, and the earth also moves at a high speed relative to the spacecraft. Brother looks younger than brother, and brother should look younger. This question can't be answered at all In fact, special relativity only deals with uniform linear motion, and my brother has to go through a process of variable speed motion to come back, which relativity can't handle. While people are busy understanding the relative special relativity, Einstein is accepting the completion of the general relativity.
1907, Einstein wrote a long article about the special theory of relativity, "On the Principle of Relativity and Its Conclusions". In this article, Einstein mentioned the principle of equivalence for the first time, and since then, Einstein's thoughts on the principle of equivalence have been developing continuously. Based on the natural law that the inertial mass is directly proportional to the gravitational mass, he proposed that the uniform gravitational field in an infinitely small volume can completely replace the frame of reference for accelerating motion. Einstein also put forward the view of closed box: no matter what method is used, the observer in closed box can't be sure whether he is still in the gravitational field or in the accelerating space without gravitational field. This is the most commonly used viewpoint to explain the equivalence principle, and the equality of inertial mass and gravitational mass is the natural inference of the equivalence principle.
1915438+01In June, Einstein submitted four papers to the Prussian Academy of Sciences. In these four papers, he put forward a new viewpoint, proved the precession of Mercury's perihelion, and gave the correct gravitational field equation. At this point, the basic problems of general relativity have been solved, and general relativity was born. 19 16 years, Einstein finished his long paper "The Basis of General Relativity". In this article, Einstein first called the theory of relativity that once applied to the inertial system as special relativity, and called the principle that only the physical laws of the inertial system are the same as the principle of special relativity as special relativity, and further expressed the principle of general relativity: for any moving reference system, the physical laws must be established.
Einstein's general theory of relativity holds that space-time will be curved due to the existence of matter, and the gravitational field is actually a curved space-time. Einstein's theory that space is bent by the sun's gravity well explains the unexplained 43 seconds in the precession of Mercury's perihelion. The second prediction of general relativity is gravitational redshift, that is, the spectrum moves to the red end in a strong gravitational field, which was confirmed by astronomers in the 1920s. The third prediction of general relativity is that the gravitational field deflects light. The gravitational field closest to the earth is the solar gravitational field. Einstein predicted that distant starlight would deflect 1.7 seconds if it passed through the surface of the sun. 19 19, encouraged by British astronomer Eddington, Britain sent two expeditions to observe the total solar eclipse in two places. After careful study, the final conclusion is that the starlight does deflect around the sun for 1.7 seconds. The Royal Society and the Royal Astronomical Society officially read out the observation report, confirming that the conclusion of general relativity is correct. At the meeting, Tang Musun, a famous physicist and president of the Royal Society, said, "This is the most significant achievement of gravity theory since Newton's time" and "Einstein's theory of relativity is one of the greatest achievements of human thought". Einstein became a news figure. 19 16 years, he wrote a popular book about relativity, Introduction to Special and General Relativity. By 1922, it has been reprinted 40 times, translated into more than a dozen languages and widely circulated.
The significance of relativity:
Special relativity and general relativity have been established for a long time. It has stood the test of practice and history and is a recognized truth. Relativity has a great influence on the development of modern physics and modern human thought. Relativity logically unifies classical physics and makes it a perfect scientific system. On the basis of the principle of special relativity, special relativity unifies Newton's mechanics and Maxwell's electrodynamics, pointing out that both of them obey the principle of special relativity and are covariant to Lorentz transformation, while Newton's mechanics is only a good approximate law of low-speed motion of objects. On the basis of generalized covariation, general relativity establishes the relationship between local inertia length and universal reference coefficient through equivalence principle, obtains the generalized covariant forms of all physical laws, and establishes the generalized covariant gravity theory, and Newton's gravity theory is only its first-order approximation. This fundamentally solved the problem that physics was limited to the inertia coefficient in the past, and got a reasonable arrangement in logic. Relativity strictly examines the basic concepts of physics such as time, space, matter and motion, and gives the time-space view and material view of scientific system, thus making physics a perfect scientific system logically.
Special relativity gives the law of high-speed motion of objects, and puts forward that mass and energy are equivalent, and gives the relationship between mass and energy. These two achievements are not obvious to macroscopic objects moving at low speed, but they are extremely important in the study of microscopic particles. Because the speed of microscopic particles is generally relatively fast, and some of them are close to or even reach the speed of light, the physics of particles cannot be separated from relativity. The mass-energy relationship not only creates the necessary conditions for the establishment and development of quantum theory, but also provides the basis for the development and application of nuclear physics.
At that time, most physicists on earth, including Lorenz, the founder of relativistic transformation relation, found it difficult to accept these new concepts introduced by Einstein. Some people even said that "at that time, only two and a half people in the world understood the theory of relativity". The obstacle of the old way of thinking makes this new physical theory not familiar to physicists until a generation later. Even in 1922, when the Swedish Academy of Royal Sciences awarded Einstein the Nobel Prize in Physics, it just said, "Because of his contribution to theoretical physics, but also because he discovered the law of photoelectric effect." Einstein's Nobel Prize in Physics was awarded, but Einstein's theory of relativity was not mentioned.
E=mc^2
The law of material immortality refers to the immortality of material quality; The law of conservation of energy is about the conservation of energy of matter. (Law of Conservation of Information)
Although these two laws have been discovered one after another, people think that they are two unrelated laws, each of which explains different natural laws. Some people even think that the law of immortality of matter is a chemical law, and the law of conservation of energy is a physical law, belonging to different scientific categories.
Einstein thought that the mass of matter is a measure of inertia and energy is a measure of motion. Energy and mass are not isolated from each other, but are interrelated and inseparable. The change of the mass of the object will change the energy accordingly; And the change of the energy of the object will change the mass accordingly.
Einstein put forward the famous formula of mass and energy in the special theory of relativity: e = MC 2 (where e represents the energy of an object, m represents the mass of an object, and c represents the speed of light, that is, 3×10.8m/s).
Einstein's theory was initially opposed by many people, and even some famous physicists at that time expressed doubts about this young man's paper. However, with the development of science, a large number of scientific experiments have proved that Einstein's theory is correct. Einstein has become a world-famous scientist and the greatest scientist in the world in the 20th century.
Einstein's formula of mass-energy relationship correctly explains all kinds of nuclear reactions: take helium 4 as an example, its nucleus consists of two protons and two neutrons. In principle, the mass of helium 4 nucleus is equal to the sum of the masses of two protons and two neutrons. In fact, this arithmetic doesn't hold water. The mass of helium nucleus is 0.0302 atomic mass unit less than the sum of the mass of two protons and two neutrons [57]! Why is this? Because when two deuterium [dao] nuclei (each deuterium contains 1 proton and 1 neutron) are polymerized into 1 helium 4 nuclei, a large amount of atomic energy is released. When 1g helium 4 atom is generated, about 2.7× 10 12 joules of atomic energy is released. Because of this, the mass of helium 4 nucleus decreases.
This example vividly shows that when two deuterons are polymerized into 1 helium 4 nucleus, it seems that the mass is not conserved, that is, the mass of helium 4 nucleus is not equal to the sum of the two deuterons. However, calculated by the formula of mass-energy relationship, the mass lost by helium 4 nucleus is exactly equal to the mass reduced by releasing atomic energy during the reaction!
In this way, Einstein expounded the essence of the law of immortality of matter and the law of conservation of energy from a newer height, and pointed out the close relationship between the two laws, which made human beings further understand nature.
photoeffect
When light shines on some substances, their electrical characteristics will change. This photoelectric change phenomenon is collectively called photoelectric effect.
The photoelectric effect can be divided into photoelectron emission, photoconductive effect and photovoltaic effect. The former phenomenon occurs on the surface of an object, which is also called external photoelectric effect. The latter two phenomena occur inside the object, which is called internal photoelectric effect.
Hertz discovered the photoelectric effect in 1887, and Einstein was the first to explain it successfully. The effect of electrons emitted by metal surface under the action of light irradiation is called photoelectron. Only when the wavelength of light is less than a certain critical value can electrons be emitted, that is, the limit wavelength, and the corresponding frequency of light is called the limit frequency. The critical value depends on the metal material, and the energy of emitted electrons depends on the wavelength of light, which has nothing to do with the intensity of light and cannot be explained by the fluctuation of light. And the fluctuation of light is also contradictory, that is, the instantaneity of photoelectric effect. According to the fluctuation theory, if the incident light is weak and the irradiation time is long, the electrons in the metal can accumulate enough energy and fly out of the metal surface. But the fact is that as long as the frequency of light is higher than the limit frequency of metal, no matter the brightness of light, the generation of photons is almost instantaneous, no more than ten MINUS nine seconds. The correct explanation is that light must be composed of strictly defined energy units (i.e. photons or optical quanta) related to wavelength.
In the photoelectric effect, the emission direction of electrons is not completely directional, but most of them are emitted perpendicular to the metal surface, regardless of the irradiation direction. Light is electromagnetic wave, but light is an orthogonal electromagnetic field with high frequency oscillation, and its amplitude is very small, which will not affect the emission direction of electrons.
1905, Einstein put forward the photon hypothesis and successfully explained the photoelectric effect, so he won the 192 1 year Nobel Prize in Physics.
"God doesn't roll dice"
Einstein was once one of the promoters of quantum mechanics, but he was not satisfied with the subsequent development. Einstein has always believed that "quantum mechanics (Copenhagen interpretation led by Born:" Basically, the description of quantum systems is probabilistic. The probability of an event is the absolute square of the wave function. " ) incomplete, but suffering from the lack of a good explanation model, there will be a famous negative cry of "God does not roll dice"! In fact, Einstein's intuition is right, and the quantum interpretation of determinism is the truth and foundation of "quantum interpretation" Einstein didn't accept quantum mechanics as a complete theory until his death. Einstein also has another famous saying: "Does the moon only exist when you look at him?"
cosmical constant
Einstein used the cosmological constant when he put forward the theory of relativity (in order to explain the existence of a static universe with non-zero density of matter, he introduced a term in the gravitational field equation that is proportional to the metric tensor, which was represented by the symbol λ. This proportional constant is very small and can be ignored at the galactic scale. λ is only meaningful at the cosmic scale, so it is called the cosmological constant. The so-called fixed value of antigravity) into his equation. He believes that there is an anti-gravity that can balance gravity and make the universe finite and static. Einstein was ashamed when Hubble proudly showed it to him in the telescope. He said, "This is the biggest mistake I have made in my life." The universe is expanding! Hubble and others believe that anti-gravity does not exist, and the expansion speed is getting slower and slower due to the gravity between galaxies.
So Einstein was completely wrong? No, there is a twisting force between galaxies, which makes the universe expand continuously, that is, dark energy. 7 billion years ago, they "conquered" dark matter and became the masters of the universe. The latest research shows that dark matter and dark energy account for about 96% of the universe in mass composition (only real mass, no virtual matter). It seems that the universe will continue to accelerate its expansion until it collapses and dies. At present, there are other statements that are controversial. Although the cosmological constant exists, the value of anti-gravity far exceeds gravity. No wonder stubborn physicists and Bohr argued in quantum mechanics: "God doesn't roll dice!" " "Don't tell God how to decide the fate of the universe.
Linde said humorously: "Now, I finally understand why he (Einstein) likes this theory so much and is still studying the cosmological constant after many years. Cosmic constant is still one of the biggest problems in physics today. "