 What is the unspoken warning of the psychologist?
Rootless and footloose, a man in space can't help but dream of coming home. But something nobody should do is bet on the validity of a homesick dream! Flight Officer Robert Craig surrendered the tube containing his service record tapes and stood waiting while the bored process clerk examined the seal. He felt anxiety as the much-handled card refused for a time to match the instrument's metal contact points. "No specific destination," supplied the man as he punched a key on a small instrument, "Air-lock ahead and to your right. The knowledge that much of it was motivated by envy soothed him as he clumsily let himself into the lock. "Place your clothing in the receptacle provided and assume a stationary position on the raised podium in the center of the lock." Craig obeyed the robot voice and began reluctantly to remove his flight jacket. "Insert your right arm into the instrument on the central table," commanded the same voice he had heard before. "Mr. Craig, I suppose you've guessed that the next step in our little torture system here is psych." Short of Gravitational conditioning, there is nothing to stop you from going to Terra." Your body is conditioned to a normal state of free fall, or at best to a state of acceleration." It helps suppress certain physiological reactions to an entirely new set of conditions. They play an important part in our awareness of balance. There were excellent psychological reasons for the old stereotype, the 'drunken sailor.' During the days that followed, the psychologist seemed to Craig to become progressively more didactic. And yet the man could not be pinned down to any specific condition the spaceman would find intolerable. He had been on Einstein IV, the planet of eight moons, and had felt the pulse of all eight of the satellites at once that no PON could completely nullify. But even if he could accept the psychologist's authority for the cumulative effect of a gravity system, he could not understand the unspoken warning he felt underlying all that the man said. You agreed that you could not decide that for me and that my decision is logical. "Mr. Craig," the psychologist said slowly, "you have my authorization for you to return to Terra as a private citizen of that planet. On the eighth day, two attendants, who showed the effects of massive doses of PON to protect themselves from the centrifugal force, had to carry a man out of the tank.
 The culture on Terra is radically different from the culture in space.
 Even good jobs get boring on Terra.  Private citizens do not enjoy the same rights as spacemen.  The culture on Terra is radically different from the culture in space.  The gravity on Terra could make a spaceman feel sick all the time.