Friedman says the Milky Way is like a jigsaw puzzle;he says only when all the pieces are in place, and all the planets are explored, will astronomers understand how the galaxy was formed.

• 弗里德曼说，银河系就像七巧板，只有所有的部分位置都对了，也就是所有的行星都探究清楚了，天文学家才能研究出星系是如何形成的。