The discovery of stars orbiting the supermassive black hole at the galactic center was a turning point in astrophysics.
读书不体验认识，就好像闪电照物，一点都抓不到；读书不能身体力行，就像水上行车、陆上行舟、一点用处都没有。
A good abstraction is one that emphasizes the important details and suppresses the unimportant ones.