【Selected Readings】

It feels like basic physics hasn't developed for a long time, what is wrong?

On this issue, we must first confirm one point, that is, the development of theoretical physics is no longer about "right" and "wrong", but on "error", and whoever has a smaller theoretical error and can explain it more likely to become a mainstream scientific theory. With this in mind, let's take a look at what the development of theoretical physics really looks like.

We all know that modern physics originated in the times of Copernicus, Galileo, and Newton. Newton, in particular, unified the physics of heaven and earth. (Prior to this, Aristotle believed that the moon was different from the moon.) Subsequently, a group of mathematicians in France deepened Newton's theory, and they are all famous in history, Lagrange, Euler, Laplace, and so on. So far, the Newtonian theories used in the field of aerospace are the theories that have been deeply deduced by these mathematicians. Since then, using Newton's theory, humans can predict the positions of the planets and can explain astronomical phenomena in the solar system very accurately. The whole process has also gone through hundreds of years. Therefore, it is not enough to put forward a theory, and there will be a lot of follow-up work after the whole theory is proposed, which requires the participation of scientists and mathematicians.

Similarly, about 150 years after Newton, Maxwell proposed the famous Maxwell's equations, which unified "electricity" and "magnetism" and predicted the existence of electromagnetic waves, which are electromagnetic waves. Hertz validated Maxwell's theory. However, there is an irreconcilable contradiction between Maxwell's theory and Newton's theory, that is, the situation of light in an inertial frame of reference. According to Newton's worldview, it is possible to exceed the speed of light. Maxwell's theory, on the other hand, tells us that the speed of light is absolute.

Another 50 years later, Albert Einstein came out of nowhere to reconcile the contradictions between Newton and Maxwell and proposed the theory of relativity. "Time" and "space" are unified, and they are called "space-time", and the speed of light is a characteristic property of space-time, which describes the distance of space-time between any two events. In the same year that he proposed the special theory of relativity, Einstein also published an article in which he unified matter and energy and proposed the famous mass-energy equation. In 1915, Albert Einstein proposed the general theory of relativity, which described the nature of gravity as the curvature of space-time, and in 1919, it was verified by Eddington by observing a total solar eclipse.

Almost at the same time as the development of the theory of relativity, quantum mechanics also developed, from Planck and Einstein in the first generation, to Bohr, Bonn, and Sommerfeld in the second generation, and then to Heisenberg, Schrödinger, Planck, Pauli, and de Broglie in the third generation. Compton et al.

Gradually, a grand theory of quantum mechanics was constructed. Therefore, in fact, after the 30s, many scientists expressed their helplessness, because the two dark clouds at the beginning of the 20th century gave birth to two major theories, and the foundation of the two theories was laid almost in 30 years. The golden age of physics seems to have come to an end, and some physicists were influenced by Schrödinger's book "What is Life" and devoted themselves to the field of biology, and four of them finally established the double helix structure of DNA through various methods and efforts.

But has physics really come to a standstill? In fact, in many people's cognition, physics is stuck in the era of quantum mechanics. However, in fact, the development of theoretical physics is still very amazing. This is actually the "Standard Model of Particle Physics".

Newton and Einstein devoted their lives to the theory of "great unification", but in fact, no matter how hard they worked, how many geniuses they could do. This is because people at that time only knew that gravity and electromagnetic forces existed in the world. The development of physics in the past 70 years has let us know that in addition to gravitational and electromagnetic forces, there are also strong interaction forces and weak interaction forces.

During this period, Fermi and Yang Zhenning proposed the weak force theory, Yang Zhenning and Mills proposed the Yang Mills theory, Gell-Mann proposed the quark model, Higgs et al. proposed the Higgs mechanism, and Weinberg proposed the weak electricity unified theory. Finally, under the framework of Yang Mills' theory, electromagnetic force, weak force, and strong force are realized. If we look at the development of physics as a whole, from the eyes of future physicists, physics during this period is also a golden age, with more than 40 Nobel Prize winners, including several Chinese, Yang Zhenning, Li Zhengdao, and Ding Zhaozhong.

In other words, in less than 20 years before the theory of relativity and quantum mechanics, scientists have developed a new set of theories, which lasted for about 30 years, from the 50s to the 80s, and this set of theories has a tendency to achieve a "great unification" theory. However, gravity has never been taken into account. The string theory, derived by powerful mathematical tools, is also promising to be called the theory that will eventually realize the grand unification theory.

So, let's see, from Newton's theory to Maxwell's theory of electromagnetism, it took about 150 years; From Maxwell's theory of electromagnetism to the theory of relativity, quantum mechanics has gone through more than 50 years, and from the theory of relativity, quantum mechanics to the Standard Model of particle physics, it has only taken 20 years. This is clearly in a state of acceleration, not a state of deceleration, so why hasn't physics developed for a long time?

And the so-called whether the theory of physics is wrong is even more nonsense. So far, physics has been perfectly fitted to phenomena, and scientists have pursued errors by several decimal places. To verify the special theory of relativity, a cesium atomic clock is used, which can be accurate to fifteen decimal places.

So, the current physics is not about who is right and who is wrong, but who is less wrong. Did Eddington's test of general relativity prove Newton wrong? No, he just proved that general relativity is closer to the truth, and that Newton's theory is more accurate in explaining the deflection of light than that of general relativity.

Therefore, students still have to learn Newton's theory, which is still perfect at macroscopic low speeds.

And physics does not stagnate, the actual means of observation that can make physics stagnate, the reason why it is so difficult for Newton to cross to Maxwell, is actually that the means of observation cannot keep up. As long as new observation techniques are available and new phenomena can be observed, theoretical physicists will rush to the scene and come up with new theories in a lot of time. Throughout the history of physics, the closer we get to modern times, the more this is true. If the development of physics is slow, it can only be because the observation instruments cannot keep up with the pace of theoretical physics.

This is also the reason why countries are desperately building high-energy particle accelerators, gravitational wave detectors, dark matter detectors, dark energy detectors, and studying black holes. This is because these detectors are actually exploring physical phenomena at a new scale.

：。 ：