Explanation on the quality and speed of light.
Light is a very important concept not only in the history of physics, but also in our daily life. But are we really familiar? Do you really understand light? In fact, so far, the research on light continues. For example, whether light has mass or not, and whether the speed of light can be surpassed, I will give you a detailed explanation with my own understanding and understanding on these hot issues.
First of all, we should have a general understanding of the existing research process of light. I have to mention one person here-james clerk maxwell. On the basis of Faraday's work, he initiated the electromagnetic theory and became a master in this field.
And he calculated that the speed of light and electromagnetic wave is the same, so he boldly predicted that light is electromagnetic wave. After Maxwell put forward his theory in 1864, German physicist Hertz confirmed the existence of electromagnetic waves through experiments in 1887. After 1898, Marconi conducted many experiments, which not only proved that light is an electromagnetic wave, but also found more forms of electromagnetic waves. Their essence is exactly the same, but there are great differences in wavelength and frequency.
In this way, in addition to knowing the speed of light, human beings began to understand the course of light in essence-light is electromagnetic waves!
It is worth mentioning that Galileo was the first person to measure the speed of light. Although he didn't finish the measurement, he started the human to measure the speed of light. Everyone knows that Galileo can be said to be the founder of modern experimental science. Many great scientists, including Newton and Einstein, were inspired by Galileo.
Followed by Hertz, Hertz also discovered the photoelectric phenomenon that light irradiates on metals, causing changes in the electrical properties of substances. This photoelectric phenomenon is called photoelectric effect, which was later explained by Einstein. And thus won the Nobel Prize in Physics of 192 1. Einstein argued that the energy of light is not uniformly distributed, but is loaded on discrete light quanta, and the energy of photons is related to the frequency of the light it constitutes. This breakthrough theory can not only explain the photoelectric effect, but also promote the birth of quantum mechanics.
In the process of establishing the quantum mechanical system, the research on light is also deepening, especially the wave-particle duality theory. In other words, light has wave-particle duality, and it is incomplete to describe light only by waves and particles. Only by combining the two can we explain all the phenomena of light.
Later, inspired by the wave-particle duality of light, De Broglie pointed out that wave-particle duality exists not only in photons, but also in all microscopic particles, including electrons, protons and neutrons. He extended the relationship between photon momentum and wavelength p=h/λ to all microscopic particles, and pointed out that moving particles with mass m and velocity v also fluctuate, and the wavelength of this wave is equal to the ratio of Planck constant h to particle momentum mv, that is, λ= h/(mv). This relationship was later called de Broglie formula.
Three years later, through two independent electron diffraction experiments, it was proved that De Broglie equation could describe the quantum behavior of electrons. At the University of Aberdeen, George Tang Musun irradiated an electron beam through a thin metal sheet and observed the predicted interference pattern. In Bell Laboratories, Clinton Davidson and Lester germain did experiments to make low-speed electrons incident on nickel crystals, and the diffraction patterns of electrons were obtained, which were consistent with the theoretical predictions.
Another theory about light is that the speed of light is constant. This has to mention a famous experiment-Michelson-Morey experiment! Michelson-Morey experiment is a famous physical experiment done by Michelson and Morey in 1887. The speed difference between two perpendicular lights is measured by Michelson interferometer. But it turns out that the speed of light is the same in different inertial systems and different directions, thus denying the existence of ether (absolute stationary reference system), thus shaking the foundation of classical physics, becoming the beginning of modern physics and occupying a very important position in the history of physics development.
You should know that Einstein himself was deeply influenced by ether theory, and was later denied by Michelson-Morey experiment. Based on the principle that the speed of light is constant, he denied the simultaneous absoluteness of classical Newton space-time and established the special theory of relativity. Later, special relativity was extended to general relativity by equivalence principle. But the speed of light remains unchanged, which is still the cornerstone of special and general relativity!
The above brief content is about the course of human understanding of light. But the discussion about light never stopped. Let's start with the common question: Can the speed of light be surpassed? Does light have quality?
Even many news reports have said that the speed of light can be surpassed, for example, quantum entanglement is the most.
As for light, does it have quality? Many people will say that light energy is deflected by the gravity of a massive object, indicating that it has mass.
Let me explain this to you: in a real sense, the speed of motion of an object will not exceed the speed of light, and photons have no rest mass, so light has no rest mass. I agree with Ai on this point.
Let's talk about why the speed of an object will not exceed the speed of light. Let's look at this formula m = M0/sqrt (1-V 2/C 2). If the speed v of an object is greater than the speed of light, it must be 1 under the root sign. Subtract the number greater than it to get a negative number. How to find the root of negative numbers? Even if it comes out, it doesn't mean anything. That's why ftl doesn't exist in theory.
In the same formula, we assume that the mass of the object is 1. The speed of an object reaches the speed of light. Then the mass of the object becomes 1 divided by 0. 1 divided by zero is meaningless in mathematics, but in the real universe, it means infinity. In other words, the mass of an object tends to infinity. If you type 1 and divide it by 0, infinity will be displayed.
So this is the mathematical explanation why objects cannot reach the speed of light. No matter whether the mass is any positive number such as 1, 2, 3, dividing by zero is an infinite trend.
This is a mathematical explanation. Are you satisfied? I want to ask more deeply, why can't objects move at the speed of light? All numerical formulas will become powerful and clear when they return to reality!
Let me answer you like this. Einstein explained the cause of gravity by bending time and space, which I think needs to be corrected. That is, the cause of gravity is space-time, not space-time bending. And time, space and matter are the same thing. This comprehensive thing can be measured by space-time energy. So any object must be in the gravitational field, in the universe.
Then if an object wants to exceed the speed of light, it must overcome the space-time property. This space-time property refers to the cosmic environment. After all, time, matter and space are one thing, and they are sticky.
Moreover, if a mass object moves at the speed of light, its mass will tend to infinity and time will stop. It's like saying that this object as a "force point" will affect and pull the whole universe. So it's impossible.
Because the energy of a single object will not exceed the energy of the whole universe. So in this way, the speed of light is actually a law, a bound state, a bound state law. That's why objects don't move faster than light!
Our problem is not over yet! Since light can be deflected by the gravity of a massive object, it means that it should have mass. If there is no mass, gravity will not act on it.
Let's look at two formulas, mass-energy formula E=mv? Planck E=hv. Assuming that photons have mass, different jumping photons correspond to different velocities, but this is not consistent with the observed results, and the observed photon velocities are uniform. Moreover, there is no m in Planck's formula, which in itself means that the photon rest mass is zero. Or it can be said that there is no rest mass. This is more accurate.
In fact, we know that the rest mass of photons is zero, which is a theoretical requirement. None of us has measured that its mass is zero. You can't measure it because you can't find a stationary photon. So it is accurate to say that photons have no rest mass. It can also be said that photons must have mass, but they have moving mass.
Einstein once questioned that Newton's first law was suspected of circular argument, and here I found that his theory was also suspected of circular argument. In real life, we can't find the inertial system, but we have to explain that in the inertial system, objects always keep moving in a straight line at a constant speed and are at rest. Similarly, in order to prove that the rest mass of photons is zero, we must first find the rest photons. But we can't find the rest photon, but we also say that the rest mass of the photon is zero. Or photons have no rest mass. The discussion here seems meaningless, but it is actually very interesting.
Then we assume that photons have no rest mass, and photons with different transitions correspond to a fixed spectrum, which is consistent with the observed results. So we say that photons have no rest mass.
Then the problem comes again. Light has a moving mass. Why is the movement process and quality not infinite? But we still don't understand. Have sports quality, why not follow the theoretical content!
There is a similar question: Why does the speed of light travel at the speed of light? What is the essence of the principle of light speed and the mechanism of cosmic laws?
Answer the first question first. Light has moving mass, but it can travel at the speed of light! Personally, I think this is related to wave-particle duality. Photon energy is partially transmitted, and when it is deflected by a massive object, it shows the nature of "wave".
Mass and energy are two concepts, two sides of an object. Photons are mostly described by energy. That is, what is the energy of a photon moving at the speed of light, not its mass. Energy is not infinite, and quality is naturally not infinite. Therefore, photons, a special particle moving at the speed of light, will not have infinite mass.
Otherwise, the sunshine that hits us will directly destroy us! But sunlight is warm, which means it carries energy. In our visible vocabulary, it is "warmth". Have you ever met someone who will say, "Give me two Jin of warmth"? This description is actually inaccurate, just to let everyone have an intuitive feeling.
In fact, wave-particle duality itself is the combination of "macro" and "quantum". It can also be said that it is the transitional embodiment of the "mass" and "energy" of the object. Therefore, it is correct and possible for Einstein to unify the four basic forces in his mind after he discovered the photoelectric effect and established the theory of relativity. The development of physics itself proves this point, but the last section of the Great Wall in Wan Li has not been completed!
As for the last question: why does light move at the speed of light? In fact, it is caused by the "stickiness" of time and space. This viscosity prevents matter from moving at the speed of light and enables photons to move at the speed of light.
Speaking of the above circular argument, I thought of Godel's incompleteness theorem.
1, any formal system containing first-order predicate logic and elementary number theory has a proposition, which can neither be proved true nor negative in this system.
2. If the system S contains elementary number theory, when S has no contradiction, its non-contradiction cannot be proved in S. ..
As you can see, the great Godel has revealed a philosophical inspiration for us. Any circular argument, paradox or theory wants to say this, prove that and follow up at different levels. The final result is unprovable and unspeakable.
This tells us that the universe exists in an interconnected form, but it cannot prove its authenticity. Yes, the universe doesn't need truth and falsehood, but human beings do!
Excerpted from Chapter 26 of Dunzhe Ling's popular science book Change, he is an independent scholar, poet, writer and famous Chinese scholar.