Today I will talk about the hypothetical basis of the theory of relativity—the speed of light does not change. Many people know Einstein’s theory of relativity. They also know that the theoretical basis of the theory of relativity is that the speed of light does not change. That is, no matter which frame of reference you refer to, the speed of light is constant. This is a difficult question to understand. I have seen other people's understanding before, and I also thought about how to understand the problem of the constant speed of light, which is puzzled!
When I was in the bathroom today, I suddenly became interested in this question again, so I searched for how to understand the speed of light unchanged. I read the previous answer. The knowledge I said was quite complete, but I still didn’t use the simplest words to talk about the speed of light. To be clear, I still cannot understand why the speed of light does not change in different frames of reference!
So I picked up my little book and started thinking about this problem that once made me give up, but this time I seem to have a different understanding. I dare not say that I fully understand that the speed of light does not change, but I am closer to the truth. One step! The following is my explanation of the speed of light that is constant relative to any frame of reference. I will try to express it in very popular language. For ordinary us, we have not learned any electromagnetic theory or Maxwell's electromagnetic equations, so we want to pass around The most common thing to understand the concept of constant speed of light!
Classic Case
What is light?
For this question, we will not correct those Baidu official answers, because you still can't understand it after reading it! Have you seen a pearl necklace? We cut the necklace and arranged the pearls in a straight line. Each pearl in this one is a photon, so many pearls connected together are a string of photons, which can be understood as a beam of light!
What are the characteristics of light?
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Light, there is a feature! It is the same speed in the same medium. What does this mean? Air is a kind of medium, water is a kind of medium, the speed of light propagation in the air is a fixed value, understand this!
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The movement of the medium does not affect the speed of light propagation . This is very important. After understanding this sentence, you can understand the next question! How to understand it? Let's look at a life case!
Case 1: You have a box in your hand. Light energy passes through the left side of the box and shoots out from the right! You think, there is air in this box, and just passing through the air in the box shoots out from left to right! At this point, you move the box forward, assuming that only one beam of light enters from the left side of the box. Will the light passing through the box bend? , The medium in the box-the air is moving, but the light still follows its straight line. You can understand that no matter the medium moves left or right, it cannot affect the speed and direction of the light. The speed of light is only related to the medium, and has nothing to do with whether the medium is moving and the direction of movement! To understand this, look at another case! If you don’t understand it, you can think about it again and again. Light is solid, and its ejection speed is only related to what medium it is in. It doesn’t matter whether the medium moves or not. The relative velocity in this Newtonian mechanics is incompatible. According to the understanding of Newtonian mechanics, you light runs in my air. If my air has speed, should your speed be the speed of air movement plus your own speed? However, this is not the case!
Case 2: You can understand it this way, my light is quite awesome, my running speed does not refer to any objects, I rely on myself to move one by one photon! Running in the air, your air is still a hindrance, which reduces my speed. I run in a vacuum at the fastest speed. Nothing hinders me! I'm running in your air. I penetrated you directly. After squeezing you away, I opened up a channel for myself! Because I pass through your air, there is friction in contact with your air, and the friction between me and your air is sliding friction, so the resistance is fixed, no matter which direction your medium moves, only the speed is not the same as the speed of my light. , The resistance is fixed! All my running speed is also fixed, not affected by whether your medium is moving!
Train case
In a train, student A sent a beam of light from a flashlight on the locomotive to the end of the train! The speed of the train at this time is 100m/s
. If student B is on the platform to measure the speed of the light, is this speed C or C+100? (C stands for light beam)
Answer analysis: Of course everyone knows it, it must be C. It is said that the speed of light will not change according to the reference! If you are a primary school student, the Newtonian mechanics you have learned is not understood in this way. Newtonian mechanics says: I am moving on a train, and the train itself has speed, so my speed is the speed of my movement + the speed of the train! But as we said earlier, the speed of light moving in the air medium has nothing to do with the movement of the medium itself! I care whether your train is 100m/s or 1000m/s. As long as you are air, I can penetrate you. No matter how fast you move, I will penetrate you at my own speed!
Grow together
No, no understanding, why not, let's discuss it together! Welcome to pay attention to the public account [Python Sharp Sword], here I will post some of my thoughts and related articles including not limited to Python, VBA, Mysql, RPA robots, etc. I hope to help you!
