It looks like we hit zero, but we actually don't remember that we never go all the way to zero, so there's these little points if we were to look really carefully at an accurate probability density plot, And then, for example, how many nodes do we have in the 3 s orbital?

但其实没有，记住，我们永远不会到零,如果我们，在概率密度图上,非常细致的看这些点的话,它永远不会到零，在3s轨道里，有多少个点呢？，2个，正确？

麻省理工公开课 - 化学原理课程节选

The point is that administrations are always crafting long-term spending plans for defense and other facets of federal activity, and those plans almost never work out the way they were expected to because we live in a world of two-year political cycles and great global volatility.

FORBES: Defense Plans Will Change, So Don't Bank on Obama Blueprint