Why should we try for space travel? It cannot be a substance of any kind that can be expected to pay. It can only be something intangible, not involving haulage, which is at the same time more valuable. There is something like that: Knowledge.
Ideas, like large rivers, never have just one source.
The younger generation of rocket engineers is just beginning. They are of the new generation to which space travel is not going to be a dream of the future but an everyday job with everyday worries in which they will be engaged.
The point to remember is that a giant leap into space can be a giant leap toward peace down below.
The study of an idea is, of necessity, the story of many things. Ideas, like large rivers, never have just one source. Just as the water of a river near its mouth, in its final form, is composed largely of many tributaries, so an idea, in its final form, is composed largely of later additions.
