The difference between special relativity and general relativity is that the former discusses the physical laws between reference frames (inertial reference frames) with uniform linear motion, while the latter is extended to reference frames with acceleration (non-inertial reference frames), which is widely used in gravitational fields under the assumption of equivalence principle. Relativity has greatly changed the common sense concepts of the universe and nature, and put forward new concepts such as "simultaneous relativity", "four-dimensional spacetime" and "curved spacetime". It developed Newtonian mechanics and pushed physics to a new height.
The historical significance of the theory of relativity lies in:
The ruler in motion will become shorter: the research object of relativity is the high-speed moving world and the vast universe beyond people's daily experience. Special relativity holds that a ruler in motion will become shorter. Of course, it is impossible for people to notice when they are moving at a low speed, but if they are moving at a speed of 260,000 kilometers per second, the ruler of one meter will be reduced to half a meter. Special relativity shows that high-speed travel will slow down time. Suppose that in the future, people can build a spaceship flying close to the speed of light and fly from the earth to distant galaxies. The round trip is only a few years (according to the time on the spaceship), but during this time, thousands of years have passed on the earth.
19 15 years, Einstein developed special relativity into general relativity. General relativity holds that space-time without matter is flat, and space-time with matter becomes curved, and the distance between two points is stretched or squeezed because of the existence of matter. An intuitive metaphor is that a horizontally stretched cloth should be flat. When you put the shot put on the cloth, the surface of the cloth will become curved. At this time, if you put a small glass ball on the cloth, it will roll to the center of the shot put. Similarly, the mass of the planet bends the surrounding space-time, and the "gravity" on the planet is actually the phenomenon that space-time is bent. According to the general theory of relativity, American physicist Oppenheimer proved in 1939 that if the mass of a star is concentrated in a sphere small enough, the intense squeezing of gravity will make the density of that celestial body infinitely increase, and then it will collapse catastrophically, making the space-time there infinitely curved. This is what people often hear.
Theory gave birth to the atomic bomb: As an inference of relativity, Einstein put forward the famous mass-energy relationship: energy equals mass times the square of the speed of light. Under the guidance of this theory, in 1939, scientists discovered the neutron chain reaction that transformed mass into energy through fission and released huge atomic energy, and then made an atomic bomb, and later invented the hydrogen bomb through nuclear fusion. The peaceful use of nuclear reactors, such as nuclear power plants and controllable nuclear reactor heating systems, which can control the severity of reaction, has greatly improved people's lives.
Global positioning system also depends on Einstein's theory of relativity. Einstein pointed out that the traditional concept of time can only be determined under simple conditions, and when many factors are temporarily linked, the traditional timing method will lose its function. Because the signals from global positioning satellites are in different reference frames, time and space cannot be synchronized with the ground. Only by constantly adjusting the time according to the satellite and the atomic clock on the ground can the accuracy of the positioning system be guaranteed.
1976, physicists Wissot and Levin launched a rocket with a clock into space. They observed that this clock was110 microseconds faster than the clock placed on the earth. They believe that in order to travel in the future, we must use those gravitational fields whose intensity is much higher than the earth's gravity, such as neutron star gravitational field. If the spacecraft reaches the neutron star, it will be a big step in the future.