restricted theory of relativity
1905, Albert Einstein, an American physicist born in Germany (1879- 1955) published his special theory of relativity. This theory points out that the only constant in the universe is the speed of light in vacuum, and everything else-speed, length, mass and elapsed time-changes with the observer's frame of reference (specific observation). This theory has solved many problems that have puzzled physicists for a long time. This theory forms a famous formula: E=MC2, that is, energy (e) is equal to the square of mass (m) multiplied by the speed of light (c).
Relative time
Special relativity holds that time is not absolute (that is, fixed). Einstein pointed out that as the speed of linear motion of an object (in the observer's view) increases, time will slow down. The use of synchronous atomic clock proves the correctness of this conclusion. Leave one clock on the ground and carry another clock at a very fast speed (for example, on a jet plane), and then compare it, the stationary clock is always a little faster than the other clock.
Relative length
Irish physicist George Fitzgerald (1851-1901) suggested that matter will shrink (shrink) in the direction of motion, which means that according to the viewpoint of a stationary observer, a rocket running near light will show a shorter length than when it is at rest, although this seems to a rocket rider. Einstein pointed out that when any object moves at the speed of light, its length will shorten to zero.
space-time
Two hundred years before Einstein published his theory of relativity, British physicist isaac newton (1643- 1727) proposed that time and space are absolute, and space and time are completely separated. However, in relativistic mathematics, time and three-dimensional space-length, width and height-together form a four-dimensional space framework, which is called time-space correlation set.
Slaven
Einstein deduced the equation E=MC2 from his special theory of relativity (where e is energy, m is mass and c is constant speed of light), and he used this equation to explain that mass and energy are equivalent. It is now believed that mass and energy are different forms of the same substance, called mass energy. For example, if the energy of an object is reduced by a certain amount E, its mass is also reduced by an amount equal to MC2. However, whether mass can disappear is only released in another form, which is called radiant energy.
The classical physics of Galileo's relativity principle begins with denying Aristotle's view of time and space. There was a heated argument at that time. Those who agree with Copernicus' theory argue that the earth is in motion, while those who defend Aristotle-ptolemaic system argue that the earth is stationary. The static school has a strong reason to oppose the earthquake: if the earth is moving at a high speed, why can't people on the ground feel it at all? This is indeed an unavoidable problem.
1632, Galileo published his masterpiece "Dialogue between Ptolemy and Copernicus". "Salviati" of the earthquake school in the book gave a thorough answer to the above questions. He said, "Put you and some friends in the main cabin under the deck of the ship, let you take some small flying insects such as flies and butterflies, and put a big water bowl in the cabin with some fish in it." Then, hang a water bottle and let the water drop into the jar below. Ships and fish swim freely in all directions, and water drops drip into the jar below. When you throw anything to your friend, as long as the distance is equal, you don't have to use more force in one direction than in the other. Your feet jump together, and the distance in any direction is the same. When you carefully observe these things, and then let the ship move at any speed, as long as it moves evenly and does not sway from side to side, you will find that the above phenomenon has not changed at all. You can't tell whether the ship is moving or standing still from these phenomena. Even if the ship moves quite fast, you can't jump to the stern farther than the bow. Although when you jump into the air, the bottom of the boat moves in the opposite direction to the direction you jump. When you throw anything at your partner, whether he is at the bow or at the stern, as long as you stand on the opposite side, you don't need to use more force. The water drops will drop into the jar below as before, and not a drop will drop to the stern. Although the water drops are in the air, the ship has traveled a lot (the length from the big fingertip to the little fingertip is usually nine inches, which is an ancient unit of length). The force used by the fish before swimming to the water bowl is not greater than the force used after swimming to the water bowl; They swim leisurely to the bait placed anywhere on the edge of the water bowl. Finally, butterflies and flies continue to fly around carelessly. They will never focus on the stern, not because they may stay in the air for a long time, get rid of the ship's movement and look tired to catch up with it. "
Saviati's big ship tells an extremely important truth, that is, you can't tell whether the ship is moving or stationary from anything that happens on board. Now this paper is called Galileo's principle of relativity.
In modern language, Salviati's big ship is the so-called inertial reference system. In other words, ships that move at different uniform speeds without swinging from side to side are inertial reference systems. All kinds of phenomena that can be seen in one inertial system can certainly be seen in another inertial system, and there is no difference. In other words, all inertial reference frames are equal and equivalent. It is impossible for us to judge which inertial reference frame is at absolute rest and which is in absolute motion.
Galileo's theory of relativity not only fundamentally negates the criticism of the stationary party on the theory of ground motion, but also denies the concept of absolute space (at least within the scope of inertial motion). Therefore, in the transition from classical mechanics to relativity, many concepts of classical mechanics will be changed, but Galileo's principle of relativity not only does not need to be modified, but also becomes one of the two basic principles of special relativity.
Two principles of special relativity 1905, Einstein published the fundamental paper "On electrodynamics of moving objects". Regarding the basic principle of special relativity, he wrote: "The following considerations are based on the principle of relativity and the principle of invariance of light speed. We stipulate these two principles as follows:
1. The laws followed by the state changes of physical systems have nothing to do with which of the two coordinate systems with uniform motion is used to describe these state changes.
2. Any light moves at a certain speed c in the "stationary" coordinate system, no matter whether it is emitted by a stationary or moving object. "
The first is the principle of sex, and the second is the constant speed of light. The whole special theory of relativity is based on these two basic principles.
Einstein's philosophy is that nature should be harmonious and simple. In fact, his theory usually has a remarkable feature: simplicity and profundity. Special relativity is a system with this characteristic. The two basic principles of special relativity seem to be "simple facts" that are not difficult to accept, but their inferences have fundamentally changed the physics foundation since Newton.