A Brief History of Quantum Mechanics

　　Two of the biggest revolutions of physics are relativity and quantum mechanics(量子力學). What is quantum mechanics? It is the rule governing the microscopic world and they are all come from the wave-particle duality(波粒二象性).

Newton

Huygens

　　 What is light? Newton thought light as particles. But another physicist Huygens(惠更斯) thought light as wave. In 1801, physicist Thomas Young’s experiment(double-silt experiment) showed that light is wave. Is it true? In fact, light has wave-particle duality(after Einstein’ photoelectric effect theory in 1905 confirmed it).

de Broglie

Schrödinger

　　
        Light can have the property of wave, can electron be wave? Physicist de Broglie(德布羅意) published this idea in 1924(proofed in 1927). He got Nobel prize in 1929 because of this paper(this is his Ph.D paper).

　　In 1926, Schrödinger (薛丁格) published his theory of quantum mechanics to describe electrons. He write down a beautiful equation called “Schrödinger’s equation”(薛丁格方程式). There is a wave functionψ(波函數) to represent the state of electron. But how to explainφis a big problem. This is because the strange property ofψ. In 1927, Born(波恩) explain it as probability distribution(機率分布).

Schrödinger’s equation

　　Great physicist Niels Bohr(尼爾斯．波耳) summarized and epitomized(集大成) the interpretations of quantum mechanics and issued his “complementarity principle”(互補原理) in 1927. These interpretations are called “Copenhagen interpretation”(哥本哈根詮釋) and therefore become standard explanation of quantum mechanics.

Niels Bohr

　　
   




     What is the strange property of ψ? Because of the wave-particle duality, electron has the property of wave called superposition(疊加). It allows electron in “any” place before we do an observation. After the observation, electron’s wave function ψ“collapse”(波函數塌陷) to a single state.

　　 These are brief history and theory of quantum mechanics. In next article,I want to talk how such theory lead to ridiculous conclusions.