 Fifty years later, Tweenietown has a population of 1,154, some of which is undoubtedly due to natural increase by the original Tweenie population, and some of which is equally undoubtedly due to the arrival of more orphaned Tweenies from Mars (since Scanlon and Max's discovery of atomic power makes interplanetary travel more common).In the fifty-one years that pass in the course of the story, the situation for the Tweenies remains unchanged on Earth.The Tweenies lack, as Scanlon notes, political, legal, economic, and social equality with humans (and, for that matter, with native Martians).