1900: A physics genius wandering around Europe

Chapter 60: Wave-Particle Controversy
At the defense meeting at Trinity College, Li Qiwei spoke eloquently under the gaze of more than 200 people.

"Since ancient Greece more than 2,000 years ago, scientists from the Pythagorean school have believed that light is a stream of tiny particles."

"There's no special reason. It's just that light is very common and intuitively it should be a particle."

"But the ancient philosopher Aristotle believed that the propagation of light is similar to ripples in water, but few people agree."

"So the idea that light is a particle persisted for nearly a thousand years without much progress."

"It wasn't until 1655 that the Italian mathematician Grimaldi discovered that if you put an object in the sun, the edges of the shadow formed would be blurred."

"So Grimaldi speculated that light might go around obstacles like water waves and run behind objects, causing the boundary between light and dark to be unclear."

"So, he did an experiment where he let a beam of light pass through a small hole and shine it onto a screen in a dark room."

"It turned out that after the light passed through the small hole, the light and shadow on the screen became significantly wider. This phenomenon is very similar to water waves."

"Therefore, he believed that light might be a fluid that could move in the form of waves, and proposed the concept of [diffraction of light] for the first time."

"Grimaldi also became the earliest advocate of the wave theory of light, breaking people's inherent understanding of the particle theory of light."

Everyone in the classroom listened quietly. They were impressed by Li Qiwei's simple and easy-to-understand language and even developed a little interest in physics.

"Then, British scientist Hooke inherited Grimaldi's ideas. He conducted experiments to observe the colors on soap bubble films and proposed that the color of light is determined by its frequency of fluctuation."

"And in 1665 he published Microscopy, which explicitly supported the wave theory of light."

"At this point, physicists generally believed that light was a wave, because particles could not explain the diffraction phenomenon."

"However, God may have thought this was too boring and wanted to make trouble, so the great Sir Newton was born."

"In fact, Newton also agreed with the wave theory of light at the beginning, but because he was discriminated against by Hooke, he was angry and firmly believed that light was a particle."

"In the famous prism dispersion experiment, Newton discovered that white light is composed of different colors of light and explained the color composition using the particle theory."

"Then, with his powerful mathematical ability, he used particles to explain the refraction, reflection, and even diffraction of light."

"The most outrageous thing is that he even used the particle theory to explain why light, which is a particle, can pass through glass."

"Newton believed that light propagates in the ether and travels on ether waves. When the ether waves encounter glass, they are partially transmitted, causing the light particles above to be transmitted along with them."

At this point, everyone in the classroom couldn't help but admire Newton's extraordinary imagination.

"Then, Hooke died, and no one could argue with Newton."

"And at this time, Newton had already published the law of universal gravitation and the three laws of motion. He was the authority in the field of physics, and no one dared to challenge him."

"However, the wave theory had successors. In 1690, Dutch physicist Huygens published "Treatise on Light", in which he used the wave equation to perfectly explain reflection, refraction and diffraction."

"And he asked a pointed question: If light is a particle, then why can't we see two beams of light collide when they cross each other?"

"Unfortunately, such strong evidence still could not defeat Newton, because Huygens died in 1695, and no one dared to challenge Newton since then."

"So far, Newton's particle theory of light dominated the entire 18th century."

"The debate between Newton, Hooke, and Huygens about the nature of light, which I call the first wave-particle war, ended with the victory of the particle theory."

"However, the victory of the particle theory is not a comprehensive victory, and it cannot convince everyone, because people are just succumbing to the aura of Newton's authority."

"Since Newton's death in 1727, physics has never lacked people who rebel against authority!"

"In 1801, British physicist Thomas Young did not understand why Newton had to go around in circles and use mechanics to explain the diffraction of light. No matter how you look at it, it is more natural to explain it as a wave." "Therefore, he proposed the idea of ​​interference. If light is a wave, then when a beam of light passes through two slits, it will leave light and dark stripes on the screen due to interference."

"If light were particles, on the other hand, there would be only two bright streaks on the screen."

"Thus, one of the most classic experiments in the history of physics, Young's double-slit interference experiment, was born. This experiment is so simple and beautiful that you can do it at home by lighting a candle."

"The bright and dark stripes did appear on the screen, which strongly proved that light is a wave, not a particle."

"After Thomas Young published his views, he was immediately attacked and insulted by countless people because he challenged Newton's authority."

"He was forced to apologize quickly, saying that he admired Newton very much, but that great men could also make mistakes, which affected scientific progress."

"Young's experiment started the second wave-particle war, but this time the main battlefield was not in Britain, but in France, because Newton had been deified in Britain."

"The French didn't care. In 1819, the French Academy of Sciences even offered a reward for an article that would use precise experiments to determine the diffraction of light and use mathematics to deduce the movement of light as it passes through an object."

"Soon after, French engineer Fresnel published a paper with rigorous mathematical analysis."

"He thought that if a beam of light passed through a disk of the right size, a bright spot would appear in the center of the shadow behind the disk, and bright rings of decreasing width would appear outside the shadow."

"French physicist Poisson was a staunch supporter of the particle theory and he believed that the predictions in the paper were impossible."

"So, he conducted a disk diffraction experiment on the spot in front of the reviewers of the Academy of Sciences, and the result actually showed bright spots, which was consistent with the description in the paper."

"Fresnel became famous and a legend in the field of optics, but this bright spot was later called the Poisson bright spot."

"At this point, Newton's particle theory failed. People found that Newton could make mistakes, which was incredible."

"In the second wave-particle war, the wave theory won."

Everyone in the classroom was fascinated by the talk, especially the students who were not from the physics department. They could not have imagined that Li Qiwei could make the boring physics knowledge so vivid and interesting, making people feel as if they had experienced every experiment and debate in person.

Many people put aside their contemptuous thoughts. To be so familiar with the history of physics, it showed that the other party was not only a genius, but also had worked hard.

Even many professors and lecturers were impressed by Li Qiwei's speech. If they could have this kind of thinking, I am afraid that more students would love to study physics.

Li Qiwei looked at the expressions of the crowd and knew that he had succeeded in pretending to be cool. Are you kidding me? Are all the popular science books on physics in later generations read in vain?

However, he then suddenly raised his voice and changed his expression.

No longer gentle and elegant, like a spring breeze, but full of vigor and vitality, extremely domineering.

"However, the debate over light is far from over, and the wave theory is not the truth."

"Today in this classroom, I will launch the third wave-particle war."

"However, unlike the previous two times, after this argument ended, there was never a fourth one."

"Because I will put an end to the discussion about the nature of light and put an end to the wave-particle debate."

boom!
There was an uproar in the classroom.

Those who mock him think that Li Qiwei is arrogant and aggressive.

His admirers, however, think that Li Qiwei is extremely talented and unique.

Thank you all for your votes and support. Lao Xu is here to collect and read. This round of PK is very important. Please don't hold back on reading. Please help click to the last page. Thank you very much. I beg you to read.

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(End of this chapter)