The Value of Scientific Thinking: The Rise of Physics, The Scientific Method, and the

Elevate your thinking

Guide

Although scientific thinking is a profound and rich way of thinking, it is also a very simple thought.

Author: Liao Wei

Publisher: Science Press

Publication Date: 2021-08-01

Synopsis

"The Value of Scientific Thinking: The Rise of Physics, The Scientific Method and Modern Society" mainly takes the main scientific discoveries of Galileo, Newton and others as an example, and describes the characteristics of scientific thinking and scientific methods and their value to human beings, including the value of experimental science for rational understanding, how scientists think, the connection and important difference between scientific thinking and ancient wisdom, the relationship between science and technology, the challenges and opportunities given by science and technology to modern society, and many aspects such as science and technology. With some concrete examples, The Value of Scientific Thinking: The Rise of Physics, the Scientific Method, and Modern Society demonstrates the art of scientific thinking and shows that although scientific thinking is a profound and rich method of thought, it is also a very simple thought.

About the Author

Liao Wei graduated from the Department of Physics of Wuhan University in 1996, received his Ph.D. from the Institute of Theoretical Physics of the Chinese Academy of Sciences in 2001, worked at the International Center for Theoretical Physics in Italy and the Canadian National Laboratory for Particle Physics and Nuclear Physics, and has been a professor at East China University of Science and Technology since 2007.

Wonderful book excerpts

Chapter 5: The Power and Charm of Science

Light and heat are well-known phenomena, and there is a long history of research and conjecture about light and heat. As early as the pre-Qin era, the ancient Chinese Mojia discovered phenomena such as the linear propagation of light and the imaging of small holes of light through experiments. But what exactly light and heat really are, people have not known much for a long time. After Galileo, with the rise of scientific methods, the study of light and heat suddenly produced extremely fruitful results within a hundred or two hundred years.

Human understanding of light and heat has undergone a tortuous development, experienced many chaos and soberness to think that it has sorted out the chaos, which is very dramatic. In this development, there are many different ideas that contribute to deepening the understanding of light and heat, but also to creating chaos. However, with the help of experiments, people gradually grasped the basic properties of light and heat in a short period of time, and developed a systematic scientific theory of light and heat. Today, the understanding of light and heat is far beyond what people imagined in Newton's time, thanks to the sustained efforts of successive generations of physicists and the application of systematic scientific methods. Through a large number of and systematic experimental studies, physicists have revealed many previously unknown properties about light and heat. Some of the key experiments have also recalibrated people's thinking and steered physicists on the right path.

In this chapter, we will use the knowledge of light, heat, and vacuum as examples to further elaborate on the role of the scientific method in human understanding of the natural world.

5.1

5.1 Newton's optical experiments with particles of light said

There are many interesting phenomena in light that can cause a lot of speculation. People can notice that light is often accompanied by heat, for example, after being exposed to the sun, people can feel the heat, and the fire that makes people feel hot will also shine. Bacon thus speculated that light and heat have the same nature. In addition, people can always see the colors through light. Two points of view can arise here. One view is that color is what an object has, and color is not a property of light; another is that light has color, and color is a property of light. The observation of the rainbow makes it clear that light can have colors apart from objects, helping us to sort out the conflict between these two views. But what exactly is light? What is the color of light?

Before Newton, it had been noted that white light passed through the prism would reveal all the colors of the rainbow. In this regard, Descartes believed that when light passes through a prism, it is converted into light of various colors. This view is widely accepted and fits well with the intuitive look of the feeling.

Newton was a brilliant experimenter who did many optical experiments. He said:

In 1666 I worked on grinding optical glass in shapes other than spherical shapes and creating a triangular prism to experiment with this famous color phenomenon.

Newton went a step further and did one of the experiments shown in Figure 5.1. Newton's protocol is as follows:

1) Newton first projected white light onto a triangular prism, producing a spectrum;

2) Then project the spectrum produced by the triangular prism onto a plate;

3) Open small holes on the plate, so that different colors of light pass through different small holes, control the opening and closing of small holes, and only allow one color of light to pass through the small holes at a time;

4) Project light through the small hole onto the second prism.

Figure 5.1 Newton's dispersive optics experiment

Newton did this experiment over and over again with all the colors of light produced by the first prism. He found that after passing through the second prism, the color of the light did not change, and no longer changed to more colors. This led him to conclude that Descartes' theory was wrong. He thus believed that white light is a mixture of light with different refractories. That is: different colors of light have different refractions, and white light is a mixture of different colors of light. If you only use the first prism for experiments, you can get two possible conclusions, namely

1) The color of the light is transformed by a prism;

2) White light is a mixture, and prisms break down white light into different colors of light.

Only through the experiment of the second prism can the examination reveal that the first point of view is wrong. Newton also concluded that telescopes refracted using prisms would have a chromatic aberration effect caused by refraction, which would have a great impact on large telescopes. To avoid this problem, he designed a total reflection telescope.

Newton solved a problem while also leaving a new one. Newton believed that light was a particle, said the particles that hold light. The particle theory of light holds that light is a solid substance. As early as the ancient Greek period, it was explained in the way of particle theory. This theory holds that the surface of an object can emit particles, a kind of light atom, which can propagate in a vacuum, enter the human eye and form vision. This can be thought of as the germ of particle theory. Newton supported this hypothesis, and further believed that light is a particle of matter emitted from a light source that propagates at a certain speed in a homogeneous medium. He used particle theory to explain the color phenomenon of light, believing that different colors of light correspond to different particles, and the mixture of light colors comes from the mixing of particles with different colors. Particles of light are said to easily explain the phenomenon of linear propagation of light. The particle theory also makes it easy to explain the phenomenon of light reflection on a smooth plane, as this can be understood as a collision of particles with a smooth plane. The particle theory could also explain the phenomenon of refraction of light at the boundary of a transparent medium. However, the particle theory makes it difficult to explain that light can be reflected and refracted at the boundary of two transparent media at the same time. In addition, particles say that it is difficult to explain the phenomenon that light can pass through each other without affecting each other. Although there are many shortcomings, because of Newton's academic prestige, the particle theory of light became the mainstream understanding of light at that time.

5.2

5.2 Wave theory of light and interference experiments

The fluctuation theory of light also has a long history. Aristotle opposed the vacuum doctrine of atomism, and for him it was unacceptable to think of light as a particle that could propagate in a vacuum. His interpretation of vision is that objects can change the surrounding medium, and this change is transmitted through the medium, reaching the human eye and being perceived. This explanation can be seen as the germ of the wave theory. By the 17th century, Descartes had inherited this line of thought by proposing the wave theory of light. Descartes also did not believe in the vacuum doctrine, believing that the world was pervasive with aether matter. He drew an analogy between light and sound waves, arguing that light is the pressure to propagate through the ether.

Fluctuation theory was systematically developed and refined in Hooke and Huygens. The waves that are visible to everyday are water waves and sound waves. Such waves have some significant characteristics, such as: (1) have diffraction and interference phenomena; (2) two columns of waves can pass through each other; and (3) need to propagate through the medium. Hooke and Huygens likened light to sound waves, treating light as a longitudinal wave. They believe that light is a mechanical wave that propagates in an etheric medium. Hook believes that the color of light is determined by the frequency of the wave. Huygens proposed the Huygens principle, that is, every point reached by the wave propagation can be treated as a new wave source, producing secondary waves. Figure 5.2 illustrates such a thought. Spherical waves generated from point A propagate to the BG arc, and each point on the BG arc can be thought of as a new wave source. These wave sources produce secondary spherical waves that propagate to locations indicated by numerous arcs such as the KL arc. These secondary spherical waves are superimposed to produce the CE arc of the original spherical wave, and the entire wave still behaves as a spherical wave that propagates outward.

Figure 5.2 Huygens' demonstration of the nature of wave propagation (Image courtesy of The Wave Theory of Light Memoirs of Huygens, Young and Fresnel)

Huygens believed that the ether could penetrate into ordinary matter, causing light to propagate in a transparent medium. Huygens used his theory to explain the phenomenon of reflection and refraction of light. He also tried to explain the phenomenon of linear propagation of light using wave theory, but limited to the depth of the study at the time, his discussion was less convincing. The biggest problem with Huygens' theory is that his wave theory is analogous to sound waves, and he assumes that light waves are longitudinal waves. This gives his wave theory many weaknesses in explaining experiments.

Hooke and Huygens' theory of fluctuations in light formed a great contradiction with Newton's particle theory and caused great controversy at the time. But due to The Influence of Newton, in the years that followed, the theory of the fluctuations of light was shelved and forgotten for a long time.

A hundred years later, Thomas Young rediscovered the wave of light. In 1801, Thomas Young performed the famous Young's double-slit interference experiment. He shone a beam of light on two parallel narrow slits, and on the probe screen behind the slits he observed a series of bright stripes and dim streaks. Such a result contradicts the particle theory and is consistent with the wave theory. Figure 5.3 demonstrates the protocol of a double-slit interference experiment. Thomas Young used experiments to confirm that light is a wave, which had a revolutionary effect. Later, Thomas Young proposed that light waves are transverse waves, not longitudinal waves, which can explain phenomena such as the polarization of light. Since then, Fresnel has further developed Huygens' theory of wave propagation, using it to prove the law of linear propagation of light. In addition, Fresnel experimentally confirmed the peculiar diffraction phenomena predicted by this theory. After this, the wave theory of light was finally established, and the particle theory of light was gradually abandoned by people.

Figure 5.3 Double-slit interference experiment. Waves from S pass through the two slits, S1 and S2, interfering behind them

After this, Maxwell hypothesized that the aether was the propagating medium of electrical and magnetic phenomena, using the displacement current hypothesis to argue that electromagnetic fields could propagate in the ether, i.e., predicting electromagnetic waves. He found that electromagnetic waves travel at a speed about equal to the speed of light, and then deduced that light is an electromagnetic wave. Subsequently, Hertz discovered electromagnetic waves through experiments and found that electromagnetic waves propagate at a speed equal to the speed of light. He also used experiments to confirm that electromagnetic waves have phenomena such as reflection, refraction and polarization. This experimental evidence has led to a further understanding that light is a kind of electromagnetic wave. By the end of the 19th century, the wave theory of light was dominant, and people were thoroughly convinced that light was a wave.

However, the story doesn't end there. After a brief oblivion, the particles of light are revived in a different guise. The particles that cause light are said to be revived by new experiments.

The Value of Scientific Thinking: The Rise of Physics, The Scientific Method, and the | of Modern Society

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