Comment by db48x

Interstellar travel is a bit more difficult than that, and doing it at FTL speeds is presumably more difficult still.

But that’s not really important. Science fiction is allowed to make things up that aren’t perfectly realistic. Campbell surmised that a good science fiction author would pick just one unrealistic thing, such as FTL space travel, for every story, and the reader would oblige by suspending their disbelief. Frank Herbert might have stretched that a bit but I still think he wrote a good story. I don’t hold it against him.