What exactly is the theory of relativity? What is the theory of relativity

The theory of relativity is a basic theory about space-time and gravity, mainly founded by Albert Einstein, and is divided into special relativity and general relativity according to the different objects of study. The basic assumption of relativity is the principle of relativity, that is, the laws of physics have nothing to do with the choice of frame of reference.

The difference between special relativity and general relativity is that the former deals with the laws of physics between frames of reference (inertial frame of reference) that move in a uniform linear manner, while the latter generalizes to frames of reference with acceleration (non-inertial frames) and is widely used in gravitational fields under the assumption of the principle of equivalence. The theory of relativity has greatly changed mankind's "common-sense" concept of the universe and nature, and has put forward new concepts such as "simultaneous relativity", "four-dimensional space-time", and "curved space-time". It developed Newtonian mechanics and propelled physics to a new level.

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The theory of relativity includes the special theory of relativity and the general theory of relativity, both of which are Einstein's masterpieces, and generally only the special theory of relativity In 1905, Einstein created an unprecedented miracle in the history of science

The special theory of relativity was established.

The two basic assumptions are:

1. The principle of relativity

principle) All laws of physics have the same form in all frames of inertia;

All inertial frames are equivalent, and there is no special absolute inertial frame.

2. The principle that the speed of light does not change.

principle

ofconstancy

oflight

velocity) The speed of light in a vacuum is constant c in any direction relative to any inertial frame, and is independent of the velocity of the light source.

1887 Michelson and Morey experiments.

It is considered one of the main experimental pillars of special relativity.

Main conclusion: The clock of motion is delayed.

Scale shrinkage. If interested.

Welcome to the Department of Physics.

The content of the theory of relativity is very extensive, and naturally it is not clear in one sentence.

The theory of relativity is divided into two parts: the special theory of relativity is based on the principle of relativity and the principle of invariance of the speed of light, and the principle of relativity is the core of the theory of relativity, that is, inertial frames are equivalent to each other and cannot be distinguished. The principle of invariance of the speed of light is that the velocity of light in any frame of inertia is a constant.

From these two principles, a whole set of theories can be derived, and both theory and experiment show that Newton's theory is only a low-speed approximation of special relativity, and there are many inferences of special relativity, such as the slowing down of the moving clock, the shrinkage of the moving ruler mass energy equation, and so on.

General relativity is a theory about gravity, theory and experiment prove that Newton's law of universal gravitation is only a weak field approximation of general relativity, it is established on the basis of the principle of general covariance and equivalence, is one of the most perfect theories so far, the current big ** theory, black hole theory, etc. are closely related to general relativity.

Albert Einstein once said that if you sit with a beautiful woman, you will feel that time flies, but if you sit with an ugly woman, you will feel that time is unbearably slow, and this is the theory of relativity. The motion of an object is relative and depends on the frame of reference you take. The measure of time and length in each frame of reference for relative motion is not the same.

For example, Cuba's Robles broke Liu Xiang's world record in the 110-meter hurdles some time ago, but those in a spaceship moving close to the speed of light relative to the Earth will think that he did not break the record, and those on the spacecraft measured that he would have taken longer to reach the finish line. This is because in frames of reference that move close to the speed of light, the measure of time becomes longer. In the same way, if you are wearing 25 cm shoes, the length of the shoes you are wearing by someone on a spaceship may only be 20 cm.

Another point is that the high-speed motion does not change the simultaneity of the event, and the two cars that reach the end at the same time appear to arrive at the same time on the ship. However, the order in which events occur at different times may be reversed, and the people on the ship may see that you eat the apple first, and then see the apple fall to the ground.

The theory of relativity is the theory of physics that studies the relative relationship between time and space. It is divided into special relativity and general relativity. The former believes that the motion of an object is relative, the speed of light does not change due to the motion of the light source, and the relationship between the mass of the object and the energy is e=mc2 (e represents energy, m represents mass, and c represents the speed of light).

The latter believes that the motion of matter is derived from the gravitational field of matter, and that the propagation of light in the gravitational field changes direction due to the influence of the gravitational field.

The theory of relativity was proposed by Albert Einstein. This theory corrected the view that space, time, and gravity were separated from each other since Newton, and that the laws of motion are eternal and unchanging, thus laying the foundation of modern physics.

Extended Materials. To put it simply, the two basic principles of general relativity are:

First, the equivalence principle: the kinetic effects of the inertial force field and the gravitational force field are locally indistinguishable;

The special theory of relativity can explain not only all the physical phenomena that classical physics can explain, but also some physical phenomena that classical physics cannot explain, and predict many new effects. It leads to the fact that the speed of light is the ultimate velocity, which leads to the relative significance of simultaneity at different locations, predicts the contraction of length and the slowing of clocks, and gives Einstein's formula for the addition of velocity, the formula for mass change with velocity, and the mass-energy relationship. Also, according to the special theory of relativity, the rest mass of the photon must be zero.

Albert Einstein was born in 1879 to a Jewish family in Ulm, Germany, to Jewish parents, and graduated from ETH Zurich in 1900 to Swiss citizenship. In 1905, he received a doctorate in philosophy from the University of Zurich, Einstein proposed the photon hypothesis and successfully explained the photoelectric effect, so he won the Nobel Prize in Physics in 1921 and founded the special theory of relativity in 1905. In 1915, he founded the general theory of relativity.

He died on April 18, 1955, at the age of 76.

Albert Einstein laid the theoretical foundation for the development of nuclear energy and ushered in a new era of modern science and technology, and is widely regarded as the greatest physicist since Galileo and Newton. On December 26, 1999, Albert Einstein was selected as a "Great Man of the Century" by Time Magazine.

The theory of relativity—gravitational redshift, gravitational time dilation effect, gravitational waves—has been confirmed one by one, which has established the important position of general relativity in modern physics. One of the practical applications of general relativity is the calibration of the clocks of navigation satellites. Since navigation satellites are far away from the earth and are less affected by the earth's gravitational pull, the spaceborne clock travels faster than the ground clock.

In addition, it is necessary to take into account the clock-slow effect caused by special relativity. Although this time difference is very small, there are huge errors in the navigation satellite positioning process. Therefore, it is necessary to eliminate the time dilation effect caused by the theory of relativity in order for navigation satellites to play the role of precise positioning.

General relativity is by far the most successful theory for describing the gravitational phenomenon of the universe. The law of universal gravitation is only an approximation of the general theory of relativity in the weak gravitational field, but because the form of Newton's theory of gravitation is simpler, it can be used conveniently when the accuracy is not high.

To summarize the theory of relativity simply, everything is relative, there is no God's vision, and everything you see is an illusion. It also includes time and space. Gravity is key.

Problem: When a person moves at the speed of light (3 x 10 to the eighth power m s), time also changes. Suppose a person flies to other planets in a day at the speed of light, then when he comes to Earth, millions of years have passed.

Does that seem outrageous? Could it be that time changes due to a change in speed?

Einstein's theory of relativity simply means that everything in the world is relatively static and in relative motion. For example, if I sit on a stool, I am relatively stationary with the stool and the objects around me, while I am in relative motion with the moon (or the sun, cars and pedestrians moving outside the window) (i.e., the distance and relative position between each other change).

As the saying goes, "time is like an arrow", time and our lives pass at a speed of 300,000 kilometers and seconds, and you should travel at a speed faster than the speed of light, and the result is like you driving a high-speed car to chase a train, and the train is compared to "time" (or time) You are at the same speed as the train in the car, then your relative position (or motion) with the train is stationary, that is to say, you are relatively still with time, then your life (or time) does not pass, so your age stays at this moment. Back on Earth, life on Earth is still passing at a speed of 300,000 kilometers per second, and of course the difference between the speed of rotation and the speed of light is a problem that seems outrageous.

How physics went from Newton's time to Einstein's time.

The theory of relativity is the relativity of space-time.