What does Einstein mean by "God can't roll dice"?

God's roll of the dice actually took place at a Solvay meeting, which was a summit of scientists. In the 1920s and 1930s, scientists had a topic, that is, whether the Copenhagen School's explanation of "uncertainty" in quantum mechanics was reliable.

Is light particles or waves?

To understand this, we have to start with Newton. Newton's era solved the macroscopic low-speed physical phenomenon, that is, Newtonian mechanics, and this theory also made Newton a god. But in fact, Newton was more than the book Mathematical Principles of Natural Philosophy. There are four books in the statue in front of his tomb in Westminster Abbey, representing four masterpieces including optics.

Maybe you want to know the difference between optics and Newtonian mechanics. What we need to be clear is that the speed of light is not low, and it is even hard to say what light is. Galileo tried to measure the speed of light, but he failed. In other words, in Newton's time, what is the speed of light is still a mystery. Secondly, what is light? In fact, scientists of that era did not have good ideas to verify. Can't verify, doesn't mean can't put forward the theory, Newton thought that light is a particle, Huygens and others think that light is a wave.

Of course, they all have their own evidence. For example, the reflection of light shows that light is particle-like, while the diffraction of light actually shows that light is wave-like. Supposedly, it should be a close situation, but because Newton's academic status is God, the view that light is only particles has the upper hand. In fact, we all know that light has wave-particle duality later, but this is another story.

Later, with the efforts of Thomas Young and Maxwell, a single wave prevailed. Maxwell, in particular, is a scientist at the same level as Newton. He put forward Maxwell's equation, unified electricity and magnetism, and predicted that light is electromagnetic wave, which was also proved by Hertz.

The birth of quantum mechanics

But in the 20th century, there were two dark clouds floating over the physics building, one was ether and the other was blackbody radiation. Ether led to the emergence of relativity, and blackbody radiation led to the emergence of quantum mechanics. What does this have to do with light? Relativity is actually related to the speed of light. What is the relationship between blackbody radiation and light?

If light is a wave, it means that electromagnetic radiation should be continuous, not discontinuous. But if we solve the problem of blackbody radiation according to Maxwell's electromagnetic theory, there will be many problems. Then, plank, who was forced to do nothing, put forward the concept of "quantum" under the inspiration of Boltzmann.

He believes that energy is not continuous but one after another, and the smallest unit of energy is called quantum. Einstein further solved the problem of photoelectric effect by using "quantum"

uncertainty principle

But then the problem broke out. When scientists study the atomic structure, it is difficult to describe the atomic structure and the behavior of electrons with classical theory. In this process, scientists gradually abandoned the classical theory, and finally solved all this in matrix mechanics proposed by Heisenberg and Schrodinger's Schrodinger equation. Bonn proved that matrix mechanics and Schrodinger equation are equivalent, and gave the explanation model of probability wave, then Heisenberg further put forward the uncertainty principle, namely:

The momentum and position of microscopic particles cannot be determined at the same time. The smaller the uncertainty of momentum, the greater the uncertainty of position. Similarly, the smaller the uncertainty of position, the greater the uncertainty of momentum.

What the hell does that mean? In our traditional physics, the motion of an object is generally described as follows: at what speed does something move in a certain direction at a certain moment? However, when it comes to quantum mechanics, it becomes how much is something at a certain time and place? As for the electrons outside the nucleus, the Copenhagen school of quantum mechanics thinks that electrons appear in all positions outside the nucleus at the same time, and the difference of each position lies in the difference of probability, that is to say, the movement of electrons should be described by probability clouds.

God doesn't roll dice

This explanation model of "probability cloud" is actually unacceptable to Einstein, Schrodinger and others, so Einstein thinks this theory is incomplete. So, when he argued with Bohr, he said that famous sentence:

God doesn't roll dice.

Bohr also refuted 1:

Einstein, don't tell God what to do.

Here, we can objectively say that this theory of Copenhagen School actually explains microscopic phenomena extremely accurately, especially with high accuracy. So Einstein can only prove its incompleteness. After several wars, niels bohr, the boss of Copenhagen School, basically gained the upper hand. Later, scientists' experiments proved the viewpoint of Copenhagen School again and again.