Let's see how Einstein deduced this theory, which was seriously advanced at that time.
In fact, the discovery process of this theory was mentioned by Einstein in a speech delivered in Kyoto, Japan on February 1922 14:
I first considered the idea of relativity about 17 years ago. I'm not sure where it came from, but it must have something to do with the optical problems of moving objects. Light travels through the etheric sea, and so does the earth. From the earth's point of view, the ether flows relative to the earth. However, I can't find any evidence of etheric flow in any physical books and periodicals. This makes me want to find any possible way to prove that the movement of the earth causes the ether to flow relative to the earth. When I began to think about this problem, I never doubted the existence of ether or the movement of the earth. So I predict that if the light of a light source is properly reflected by a mirror, it will have different energy, depending on whether it moves in the direction of the earth or in the opposite direction. Using two thermopiles, I tried to verify this by measuring the difference in heat generated by each thermopile. The idea was the same as that in Michelson's experiment, but I didn't understand his experiment clearly at that time.
When I was a student thinking about these problems, I was already familiar with the strange results of Michelson's experiment, and intuitively realized that if we can accept his results as facts, then it is wrong to think that the earth moves relative to the ether. This view actually provides the first way to the so-called principle of special relativity. I began to believe that although the earth moves around the sun, light experiments can't prove it.
It was about that time that I had the opportunity to read Lorenz's monograph in 1895. Lorenz discussed and managed to completely solve the first-order approximate electrodynamics, that is, ignoring the second-order and higher-order small quantities of the ratio of the speed of moving objects to the speed of light. I also began to study the problem of Fizeau experiment. Assuming that the vacuum coordinate system is replaced by the moving object coordinate system, the electronic equation established by Lorenz still holds, so as to explain the problem of Fizeau experiment. In any case, I believe that Maxwell-Lorenz electrodynamics equation is reliable, which describes the real state of events. In addition, the condition that the equation also holds in the moving coordinate system provides an argument called the invariance of light speed. However, this invariance of the speed of light is incompatible with the known law of velocity addition in mechanics.
Why do these two things contradict each other? I feel that I have encountered unusual difficulties here. I spent nearly a year thinking about this problem and thought that I had to make some amendments to Lorenz's point of view, but it was in vain. I have to admit that this is not an easy mystery to solve.
By chance, a friend who lives in Bern (Switzerland) helped me. The weather is fine. I went to visit him and said to him, "I have been struggling with a problem these days. No matter how hard I try, I can't solve it." Today, I bring you this difficult problem. "I discussed with him in many ways. Through these discussions, I suddenly realized. The next day, I visited him again and told him simply and happily, "Thank you. I have completely solved my problem. "
My solution is actually related to the concept of time. The point is that there is no absolute definition of time, but time and signal speed are inextricably linked. With this idea, I can completely solve that unusual difficulty for the first time.
With this in mind, I completed the special theory of relativity in five weeks. I have no doubt that this theory is also very natural from a philosophical point of view. I also realize that this is in line with Mach's point of view. Although special relativity is obviously not directly related to Mach's viewpoint, it can be said that it is indirectly related to Mach's analysis of various scientific concepts, just like those problems solved by general relativity later.
In this way, the special theory of relativity came out. Then there is general relativity:
The first idea of general relativity occurred two years later-1907. It happened in an unforgettable environment.
The relativity of motion is limited to relatively uniform motion, not suitable for random motion. I was already dissatisfied with it at that time. In private, I always wonder if I can get rid of this restriction in some way.
1907, which should be Yearbook of Radioactivity and Electronics (Jahrbuch der Radioaktivit? At the request of Mr. Staack, editor of tund Elektronik, I tried to summarize the results of special relativity for the yearbook. At that time, I realized that although all other natural laws can be discussed according to the special theory of relativity, this theory cannot be applied to the law of universal gravitation. I have a strong desire to try to find out the reason behind this. But it is not easy to achieve this goal. What I am most dissatisfied with the special theory of relativity is that although this theory can perfectly give the relationship between inertia and energy, the relationship between inertia and weight, that is, the energy of gravitational field, is still completely unclear. I think in special relativity, there may be no explanation at all.
I was sitting in the chair of Berne Patent Office, and suddenly I had an idea: "If a person falls freely, he certainly can't feel his own weight."
I was startled. This simple imagination has brought me a great impact, and it is it that pushes me to put forward a new theory of gravity. My next thought is: "When a person falls, he is accelerating." What he observed was nothing more than what he observed in the acceleration system. "Therefore, I decided to extend the theory of relativity from a uniform motion system to an acceleration system. I hope this promotion can help me solve the gravity problem. This is because people who fall can't feel their own weight, which can be explained as a new additional gravitational field offsetting the gravitational field of the earth; In other words, because the acceleration system provides a new gravitational field.
Based on this point of view, I failed to completely solve the problem at once. It took me more than eight years to find the right relationship. But at the same time, I began to realize the general basis of this solution.
Mach also insists that all acceleration systems are equivalent. But this obviously doesn't conform to our geometry, because if acceleration systems are allowed, Euclid geometry will not be applicable to all systems. Expressing a rule without geometry is like expressing an idea without language. We must first find a language to express our thoughts. So in this case, what are we looking for?
I didn't solve this problem before 19 12. It was that year that I suddenly realized that there was every reason to believe that Gauss's surface theory might be the key to solving this mystery. At that time, I realized that the coordinates of Gaussian surfaces were extremely important, but I didn't know that Riemann had provided a deeper discussion on the basis of geometry. One thing happened when I was a student. I heard Gauss theory in a class of a math professor named Gajser. From here, I developed my own ideas and thought of the concept that geometry must have physical meaning.
When I returned to Zurich from Prague, my good friend Professor Grossman was there. When I was in Berne Patent Office, it was difficult to get mathematical literature, and he was willing to help me. This time, he taught me Ritchie theory, and then Riemann theory. So I asked him if he could really solve my problem through Riemann theory, that is, whether the invariance of curve elements can completely determine its coefficient-I have been trying to find this coefficient. 19 13 years, we wrote a paper together. But we didn't get the correct gravity equation in that paper. Although I continued to study Riemann equation and tried various methods, I only found many different reasons, which made me believe that it could not get the desired results at all.
Then there are two years of hard research. Then I finally realized that my previous calculation was wrong. So I went back to the invariant theory and tried to find the correct gravity equation. Two weeks later, the correct equation finally appeared in front of my eyes for the first time.
As for the research I did after 19 15, I just want to ask cosmological questions. This problem involves the geometry of the universe and time. On the one hand, it is based on the treatment of boundary conditions in general relativity, on the other hand, it is based on Mach's view of inertia. Of course, I don't know Mach's view on the relativity of inertia, but at least he has had an extremely important influence on me.
In any case, after trying to find out the invariant boundary conditions of the universal gravitation equation, I can finally regard the universe as a closed space and eliminate the boundary, thus solving the cosmological problem. From this point of view, I come to the following conclusion: inertia is only an attribute enjoyed by some objects. If there are no other celestial bodies next to a particular object, its inertia will definitely disappear. I believe this makes general relativity epistemologically satisfactory.
It can also be seen from Einstein's description that these two theories were not all introduced at once, but a theory gradually introduced by some experiments and ideas, and its birth was also supported by a considerable physical foundation.
Later generations' evaluation of Einstein
Later generations thought that Einstein was a peace-loving man and made great contributions to world peace as much as he could, because Einstein burned all his research results before his death. Some close relatives and friends said that Einstein did this to avoid war and to prevent some people with ulterior motives from using his research data to make weapons.
In fact, when Einstein was alive, European scientists gave Einstein a very positive evaluation. They all think that Einstein did something that his predecessors could not do. Although Einstein made some small mistakes in his later years, on the whole, his contribution to all mankind can not be ignored. He created three laws, which changed people's world outlook and values, and also changed the technology after that.
Others focus on Einstein's personality. Many experts think that he is a low-key introverted person, maverick. In his will, he told the world not to worship him as a god and not to turn his former residence into a museum for future generations to see. It seems that this great scientist does not want to be disturbed by too many people after his death, nor does he want his death to affect people.