But it all comes from scientists who have been looking for it for hundreds of years? Light? The mystery leads people to see a different world and catalyzes quantum mechanics that changes the world again. This process is long and outstanding. Today, let's see what we can learn from it.
Galileo began to study light.
We all know that light brings light to the world. Without light, we can't see everything and our world. But since ancient times, people have never paid attention to light, because light has always existed, and it is a thing that will exist forever and die forever. This kind of thing that can be obtained as easy as blowing off dust will not attract attention at all. It was not until Galileo, the originator of modern experimental science, began to be curious about the speed of light and began to measure it that some properties of light began to attract people's attention.
Galileo's measurement method is very primitive. He and his disciples stood on two hills 1 mile apart, each holding a lantern, and counted the interval between each holding a lantern with a stopwatch. He tried to measure the speed of light of 300 thousand kilometers per second in this rough way, of course, in vain. But he firmly believes that light has speed, but it is extremely fast.
Galileo didn't know the speed of light, but he aroused the world's curiosity about it. Generation after generation of scientists constantly improved the method of measuring the speed of light, and finally determined the accurate speed of light in the 1980s, that is, the speed of light C = 299,792,458 m/s (m/s). Since the measurement of the speed of light, people are not only interested in the speed of light, but also begin to explore the properties of light.
The exploration of the nature of light.
Rene, a French philosopher, mathematician and scientist, was the first person to make a hypothesis about the nature of light. Descartes put forward two hypotheses of light in the book Methodology of Correct Thinking and Discovery of Scientific Truth (abbreviated as Methodology) published by 1637. One is that light is a substance similar to particles, and the other is that light is a kind of light. Ether? Media pressure. He did not explicitly say that light is a wave, but he laid the groundwork for the debate between particle theory and wave theory of light later.
1655, grimma, a professor of mathematics at the University of Bologna, discovered the diffraction phenomenon of light, and concluded that light may be a fluid similar to water waves. Through pinhole imaging experiments, he further concluded that light is a fluid that can fluctuate. In fact, he has obtained the interference fringes of light through two small hole experiments, but he didn't realize that this is the double-slit interference phenomenon of light, but only thought it was the fluctuation of light. It can be considered that he is the earliest advocate of the theory of light fluctuation.
1663, British scientist Boyle discovered that color is not the nature of the object itself, but the effect of light irradiation. He first recorded the color stripes left by light on soap bubbles and glass balls, which further supported Grimm's statement. Soon after, the British physicist Hooke repeated Grimm's experiment, and through the observation of soap bubbles, he proposed? Is light the longitudinal wave of ether? The hypothesis that the color of light is determined by its frequency.
1672, Newton published his paper "A New Theory of Light and Color", describing his experiment of light dispersion: in a dark room, he let sunlight pass through a hole in a prism and got a chromatogram on the opposite wall. He believes that composite white light is like particles of different colors mixed together and separated by the decomposition of a prism. From this, he established the particle theory of light, thinking that light is composed of particles of different colors.
Debate between wave theory of light and particle theory.
Boyle, Hooke and others discovered the color of light, which seems to be the fuse of the debate between wave theory and particle theory of light. This debate has been going on for 200 years.
1672, the jury of the Royal Society composed of Hooke and Boyle rejected Newton's paper "The New Theory of Light and Color". The chairman of this committee is Hooke, which aroused Newton's argument. At first, he did not completely deny the wave theory, nor was he paranoid about the particle theory, but began to refute the wave theory.
1675, Newton reiterated his particle theory and refuted Hooke's wave theory in the article "A hypothesis to explain the nature of light mentioned in several of my papers". But at this time, neither side has formed a complete theory, and the debate has not been fully launched.
Later, Huygens, a famous Dutch astronomer, physicist and mathematician, joined the debate. During his tenure as an academician of the Paris Academy of Sciences, Huygens went to England and met Newton. They exchanged views on the nature of light and the two masters appreciated each other. However, after Huygens returned to Paris, he repeated and studied Newton's optical experiments, and also carefully studied Grimm's first experiment. He thought that many phenomena could not be explained by particle theory, so he finally supported Hooke's wave theory, which led to the disagreement with Newton.
1678, Huygens submitted the book "Light Wheel" to the Paris Academy of Sciences, which systematically expounded the wave theory of light and became the proponent of the complete theory of wave theory. In the same year, he gave a speech against particle theory. He thinks that light is a mechanical wave, light wave is a longitudinal wave propagating through a material carrier, and the medium is? Ether? . According to this theory, he proved the laws of reflection and refraction of light, perfectly revealed the phenomena of diffraction and birefringence of light, and the famous? Newton's ring? Experiment.
1990, Huygens' theory of light was officially published, and Huygens' propaganda of wave theory never stopped. He said that if light is composed of particles, it will collide with each other in the process of propagation, which will definitely lead to a change in the direction of light propagation. That was not the case. Newton made a tit-for-tat rebuttal. He put forward two arguments: first, if light is a wave, it will bypass obstacles like sound waves and will not produce shadows; Secondly, wave theory cannot explain the birefringence of Iceland spar. In addition, Newton also extended the particle view of matter to the whole nature and integrated it with his own particle mechanics system, which strengthened the position of particle theory.
In the process of refuting wave theory, Newton gradually established a complete particle theory. These viewpoints are all embodied in his optical book Optics, published in 1704. At this time, Huygens and Hooke were both dead, and the wave theory was not challenged. Newton has since become a monopolist. With the rise of his prestige, people began to worship and look up to him, and firmly believed his conclusion without questioning, thus Newton's particle theory occupied an absolute dominant position in the whole18th century.
The discovery of photoelectric effect makes people have a breakthrough in understanding the nature of light.
Newton's unparalleled academic position made his particle theory dare not be challenged for more than 100 years, and Huygens and Hooke's wave theory was gradually forgotten. This state lasted until the beginning of19th century, when Thomas, a British doctor and physicist? Yang's double-slit experiment is like a stone falling into calm water, which makes the forgotten wave theory ripple again.
Thomas is a strange man. He has a wide range of knowledge. He has high attainments in mechanics, mathematics, optics, acoustics, linguistics, zoology and archaeology. He also enjoys life very much and has a strong interest in art and fine arts. He can play various musical instruments, be good at riding horses and walk a tightrope.
In Thomas's double-slit experiment, the coherent light speed propagates from a light source and irradiates an opaque baffle engraved with two slits, and a photographic film or some kind of detection screen is placed behind the baffle to obtain black and white stripes, showing the interference pattern of the light beam, which conforms to the superposition principle followed by diffracted light waves, and is a wave behavior that Newton's light particle theory cannot explain, which just confirms the wave nature of light.
However, Thomas's experiment seems to be earth-shattering, but it has not attracted enough attention in the field of physics, nor has it completely solved the contradiction and debate between particle theory and wave theory. At this time, electromagnetism has developed vigorously, and a number of optical and electromagnetic giants, such as Nefeld, Maxwell and Hertz, have been born to undertake the important task of theoretical breakthrough.
Augustine? Jane. Niffel established huygens-fresnel principle in a new quantitative form, and perfected the diffraction theory of light. James. Maxwell predicted the existence of electromagnetic waves, put forward Maxwell equations, calculated that the wave speed of electromagnetic waves is equal to the speed of light, and thus put forward the conjecture that light waves are electromagnetic waves; Hertz proved the existence of electromagnetic wave, and proved that electromagnetic wave is shear wave through experiments, which has similar characteristics as light in reflection, refraction and diffraction, and put forward photoelectric effect.
People's understanding of light is getting closer to the essence. Through the study of photoelectricity, quantum theory has emerged!
Einstein pioneered the establishment of wave-particle duality of light.
Einstein's theory of relativity has become the most important cornerstone of modern physics, which makes people relish, but many people don't know that he has another great contribution, that is? Law of photoelectric effect? This theory was expounded in his paper "A Speculative Viewpoint on the Generation and Transformation of Light", and thus won the 192 1 Nobel Prize in Physics.
This paper, published in 1905, puts forward the optical quantum explanation of photoelectric effect, and people begin to realize that light waves have both the properties of waves and particles. After hundreds of years of arguments, it turns out that nothing is right. It turns out that light has both particles and fluctuations. If I know that these two theories are combined, I will be happy.
Of course it's not that simple. Einstein didn't take advantage, but he demonstrated the motion law of light quantum through strict mathematical logic on the basis of previous experiments, and put forward? Einstein photoelectric effect equation? It is proved that photon energy is equal to frequency multiplied by Planck constant, and the relationship between photon momentum and wavelength is put forward: p=h/? .
On this basis, he quickly established a more groundbreaking special theory of relativity.
1924, proposed by de Broglie? Matter wave? Assuming that all substances have wave-particle duality like light, electrons will also have fluctuations such as interference and diffraction. He extended the relationship between Einstein's photon momentum and wavelength to all microscopic particles, and thought that moving particles with mass m and velocity v also fluctuated. The wavelength of this wave was equal to the ratio of Planck constant h to particle momentum mv, that is? = h/(mv). Later electron diffraction experiments confirmed his guess.
At this point, everything became clearer and clearer, but then something strange happened.
Because photons and all microscopic particles have wave-particle duality, the so-called double-slit experiment was picked up by people and began to observe more closely. With the continuous improvement of observation methods, a series of strange phenomena have appeared. The results of various experiments thus obtained are as follows:
1, the interference phenomenon is not limited to basic particles such as photons, electrons, protons, neutrons, etc. Any particle will produce interference phenomenon, and even some macromolecular structures, such as fullerenes, will produce similar interference phenomenon.
2. A single electron emitted alone will also interfere, which shows that a single electron seems to be able to penetrate two slits at the same time and interfere with itself.
3. Using the detector to observe which slit the photon passes through and obtain the photon path information will lead to the disappearance of interference, and the photon will no longer appear in the form of waves, but stay in the background screen in the form of particles.
4. The conclusion of quantum erasure and delay experiment is that detecting photon path information will eliminate the interference grating of the background screen, and if the path information is erased, the interference grating will be restored.
5. After two entangled photons are separated at a long distance, observing the path information of photon A will immediately affect the behavior of photon B, and the interference pattern will disappear; Similarly, observing B will also affect A.
The observation and research of this double-slit experiment for a whole century gave birth to the Copenhagen interpretation of quantum mechanics and caused controversy for nearly a century. This debate is between Einstein and Schrodinger, the founders of quantum mechanics, and the Copenhagen School such as Bohr, Heisenberg, Born, Heisenberg and Pauli, who are also masters of quantum mechanics.
Copenhagen Interpretation and Schrodinger's Cat.
Copenhagen Interpretation is a school founded by Bohr and Heisenberg at the University of Copenhagen, which explains some strange phenomena in the quantum micro-world, including quantum wave-particle duality, uncertainty principle, wave function description principle and so on. That is, quantum always presents the superposition state of waves and particles, and human beings cannot know the momentum and position of microscopic particles at the same time. Measurement will collapse the wave function of the superposition state, and the original quantum superposition state will collapse into a quantum state that allows measurement.
These theories can be seen from the above-mentioned double-slit experimental results, which is a real and bizarre phenomenon in the micro-world. There seems to be nothing wrong with the Copenhagen interpretation. But Einstein and Schrodinger are both masters of quantum mechanics, but they show different views. They think that this explanation is only some superficial phenomena in the quantum world, so quantum theory is incomplete, and there should be a regular mechanism that we have not found, that is, the so-called? Completely locally hidden variables? As long as we find this, we can master the laws of quantum motion.
In order to refute the uncertainty principle and wave function collapse theory explained by Copenhagen, Schrodinger got a? Cat? Famous for thinking experiments? Schrodinger's cat? . This experiment assumes that a cat kept in a closed box may be released and poisoned at any time. Radioactive element control switch. As long as this radioactive element decays, it will trigger the switch and release poison to kill the cat. The decay of radioactive elements is random, and no one knows when. Therefore, no one knows the cat's life and death before unpacking. Only by opening the box can people see whether the cat is dead or alive.
This is very interesting. The classical controllable school, represented by Schrodinger, believes that the cat's life and death have been decided long before the box is opened. Opening the box only knows whether the cat is dead or alive, but it can't decide its life and death. According to the Copenhagen school, cats are always in a state of life and death before unpacking, and they may be alive or dead. What determines its ultimate life and death is open-box observation, that is, the superposition state collapses into the cost state.
Finally, this argument is proved by Bell inequality experiment. Complete local hidden variable theory? If it doesn't exist, the Copenhagen interpretation wins, and it has been regarded as an orthodox theory by the mainstream of science since then. ? Schrodinger's cat? It is Schrodinger who wants to use such a thought experiment to turn the uncertainty principle of the micro-world into the uncertainty principle of the macro-world. In the macro world, this is just? Cat? Of course, it is against logic, but the micro-world does have its special laws. It is quantum mechanics that reveals these special laws and makes a subversive breakthrough in human understanding of the world.
To sum up, the double-slit interference experiment plays an important and key role in the development of quantum mechanics. This reminds me of Archimedes, an ancient Greek philosopher, mathematician and physicist: Give me a fulcrum and I can move the earth. Thousands of years have passed, and mankind has not found this fulcrum. But the double-slit experiment is especially like giving quantum mechanics a fulcrum and letting human beings discover a completely different world.
Therefore, the double-slit experiment is not terrible. Only by probing into the deepest secrets of the world and discovering the deepest secrets of nature every time can we bring more happiness to mankind. The study of quantum mechanics has just begun, and there are still many mysteries to be explored in depth. So what did Einstein say about the world? God can't roll dice? , or Bohr, Heisenberg, etc? Is God really rolling the dice? And then what? We need to wait and see to know the answer.
That's it. Welcome to participate in the discussion. Thanks for reading.
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