The world line of a deep space tube sock.

That's a phrase I've remembered for a long time, and not just because I'm amused by incongruity: There is a congruity among the three terms in the phrase. Can you guess what it is?

(RLC is not permitted to participate in this contest!)

IN THE COMMENTS: People are trying, but in need of a hint/clarification. So, let me help. The three two-word terms appeared in a newspaper article in the mid-1970s. The article did not use the one long phrase I made out of the three terms. There's nothing known as "the world line of a deep space tube sock." The question is: what news article contained the phrases "world line," "deep space," and "tube sock"? It is possible to just think hard about what sort of article this would be and come up with the right answer!