The theory of relativity was first put forward by Einstein, a German+Swiss physicist, in 1905. Of course, it was not called relativity at that time. He just graduated from philosophy (that is, our physics) that year and published five important papers, including his doctoral thesis. One of the papers on electrodynamics of moving objects puts forward that time and space are relative to explain a conclusion derived from Maxwell's equations. This article is what we call the physical theory of establishing a new concept of time and space for human beings-special relativity.
In the same year, he published another important paper on special relativity: "Is the inertia of an object related to the energy it contains? In this paper, he gave a famous mass-energy equation: E = MC 2. But to discuss the relativity of time, we actually only need the first article (about electrodynamics of moving objects).
In the epoch-making physical theory put forward in this paper, Einstein pointed out that time and space are not absolute, they are relative, and the time and space seen in different inertial reference frames are different. But he also pointed out that their time and space as a whole is absolute.
Many people who have just heard of the theory of relativity have a misunderstanding that everything is relative, but in fact, the core of the theory of relativity has several core absolute concepts, such as absolute space-time and absolute speed of light. However, once the misunderstanding arises, it is difficult to eliminate it, so that his new theory is given the name of "Relativity", which Einstein rejected in his heart. ...
But it doesn't really matter what name you use. People who know will naturally understand, and those who don't understand will change their names or not. ...
Back to the topic, Einstein proposed in his special theory of relativity that time and space are relative, and the length of time and space measured in different reference systems will be different. For observers in the stationary frame of reference (such as people on the earth), the time interval of the frame of reference where high-speed moving objects (such as high-speed spacecraft) are located will be longer and the spatial length will be shorter. We now call this effect clock slow effect (or time expansion effect) and scale contraction effect (or space contraction effect).
Then we can answer this question now. If people move at the speed of light, they will not live forever. According to the inference of time expansion effect, when the speed of motion is close to the speed of light, time will become slower and slower (the time interval is getting bigger and bigger). It can be inferred that when the speed of motion reaches the speed of light, time will stop and time will not live forever. Yes, in the eyes of people on earth, people who move at the speed of light are indeed immortal, because time has stopped (the time interval is infinite).
However, this is "in the eyes of the earth." Obviously, it is relative under special relativity. In the eyes of people on earth, people who exercise at high speed have slow time, but people who exercise at high speed don't think so. In the eyes of high-speed people, their own time is normal, but the outside time will slow down. This is the famous twin paradox, which tells us that time is normal "passing" in the observer's own frame of reference (whether it is an earth observer or a high-speed observer).
What about people who travel at the speed of light? The answer is: there is no such frame of reference ... this is a conclusion of special relativity: the speed of light cannot be used as a frame of reference.
In fact, it's easy for you to understand why, for a time-still frame of reference, even if there is an observer on it, he can't make any observation, because he has no time to observe. ...
This is embarrassing. Isn't it that people who exercise at high speed think their time is normal? How did it suddenly change as soon as it reached the speed of light? This brings up Einstein's second paper on special relativity.
Clock slowness effect and scale effect are derived on the basis of the principle that the speed of light is constant, that is, their basis is that the speed of light is constant. The so-called constant speed of light means that the speed of light in vacuum is the same in all inertial reference frames and will not change with the movement of light source or observer. That is to say, the speed of any object will not be superimposed, which makes people think that it is the limit of motion speed. Therefore, no matter how fast a moving object accelerates, it is impossible to exceed the speed of light.
After obtaining the relativistic effect of time expansion and space contraction, Einstein found in his second relativistic paper that when an object accelerates to near the speed of light, no matter how much energy is provided to it to continue accelerating, it cannot exceed the speed of light. Then the problem is coming. According to the theorem of kinetic energy, when the input energy continues to accelerate the object, the kinetic energy of the object should continue to increase. However, due to the limitation of the speed of light, the moving speed of the object cannot increase synchronously, which leads to the continuous synchronous increase of input energy and kinetic energy, and the input energy does not produce corresponding kinetic energy. So where did the input energy go?
Finally, Einstein deduced the third relativistic effect-mass expansion in the same way as time expansion and space contraction. He pointed out that when a moving object accelerates to near the speed of light, its mass will increase relative to a stationary observer, and the increased mass is the energy lost during the previous acceleration! In this way, Einstein inadvertently discovered a mystery of the universe-mass = energy, which is the greatest discovery in his special theory of relativity-the relationship between mass and energy!
According to the mass expansion effect, when a moving object is accelerated to near the speed of light, its relative mass will become larger and larger, and it will become more and more difficult to accelerate by any method. According to theoretical and mathematical inference, when it reaches the speed of light, its relative mass will become infinite, which is obviously impossible, because even if we find the energy of the whole universe, it is a finite value, not infinite ... so obviously, it is impossible for a moving object with static mass.
There is always an insurmountable gap between a high-speed moving object with mass and the speed of light!
From the earth's point of view, when a person moves infinitely close to the speed of light, his time will approach to stop, so he is immortal to us. But for people who are infinitely close to the speed of light, the time he has traveled has not changed. In his view, a second is still a second, a day is still a day, a year is still a year, but in his view, maybe the universe was not born in 65.438+03.8 billion years. ...
But his speed will never reach the speed of light and his time will never stop, so in his own opinion, he will never live forever. ...
I mentioned in the previous conclusion that "in his view, maybe the universe was not born 65.438+0.38 billion years ago", and it suddenly occurred to me. Due to the relativity of time, according to the special theory of relativity, the universe may soon be born in a person who is infinitely close to the speed of light, because in his view, the whole universe is smaller than what the earth sees (scale-down effect) ... If he moves fast enough, it seems that the universe is less than ten years old, and he is probably younger than his own age ... A person born before the birth of the universe appears. ...