This is my first time to learn Quantum Mechanics, Quantum Mechanics is a very cool discipline to me.
MIT: 8.04.1x Quantum Mechanics I
1. Introduction to Superposition
Empirical fact: Electron is black or white, hard or soft.
Color and hardness is unrelated.
After you measured the color/hardness of a electron once, you are still not sure about its color/hardness before it’s measured second time.