 Why can't Joe go back to 1960?
A gun is an interesting weapon; it can be hired, of course, and naturally doesn't care who hires it. Something much the same can be said of the gunman, too.... The evening was dark, it was unlikely that the other even saw the circle of steel that was the mouth of the shotgun barrel, now resting on the car's window ledge. And at that moment, the universe caved inward upon Joseph Marie Prantera. There was a falling through all space and through all time. And he came out of it as quickly and completely as he'd gone in. A door slid open in the wall in a way that Joe had never seen a door operate before. Joe had been born in Naples and his mother had died in childbirth. His father hadn't brought him to the States until the age of five and by that time he had a stepmother. Joe gingerly tried swinging his feet to the floor and sitting up, while the other stood watching him, strangely. With the exception of a faint nausea, which brought back memories of that extreme condition he'd suffered during ... during what? Joe Prantera stared at him, said finally, flatly, "What's it all about?" The fear of police, of Al Rossi's vengeance, of the measures that might be taken by Big Louis on his failure, were now far away. Reston-Farrell, the one Joe had already met, was tall and drawn of face and with a chainsmoker's nervousness. He wondered, all over again, if this was some kind of pressure cooker. Reston-Farrell said, "Of course," and then something else Joe didn't get. Whatever the something else was, a slot opened in the middle of the table and a glass, so clear of texture as to be all but invisible, was elevated. "I was about to say, Los Angeles of 1960. "What is the date, Old Calendar?" "2133," Reston-Farrell said. Warren Brett-James said softly, "Mr. Prantera, you are no longer in the year 1960, you are now in the year 2133." Joe Prantera had never been exposed to the concept of time travel. Reston-Farrell said, "Suffice to say, you are now one hundred and seventy-three years after the last memory you have." Joe Prantera's mind suddenly reverted to those last memories and his eyes narrowed dangerously.
 Time only moves one way.
 Temple-Tracy destroyed the vortex manipulator.  The time circuits were damaged when they brought Joe into the future.  Temple -Tracy destroyed the time transmitter.  Time only moves one way.