 Who was talking to Jerome in the very beginning of the passage?
There is one fact no sane man can quarrel with ... You will, you know, so why quibble about it? Yes, it'll be pretty obvious it must be a time machine. You'll be puzzling over what I'll tell you, and you'll be getting used to the idea that you are the man who makes atomic power practical. You won't exactly believe it, but you'll want to go along. You start to say something, but by then I'm pressing a black button, and everything outside will disappear. You are completely outside of time and space, as best you can guess how things are. Then it comes to you slowly that you're actually traveling in time. Well, I asked it after I was told, then I came back and told it to you, and I still can't help answering when you speak. "Maybe it's no dimension—or it might be the fifth; if you're going to skip over the so-called fourth without traveling along it, you'd need a fifth. I figured out once that such a universe would need some seven or eight time and space dimensions. When you spend thirty years thinking about it, as I did—and you will—you get further and further from an answer. That means you either carry a small time field with you, or you are catching a small increment of time from the main field.
 Jerome, from 30 years in the future
 Jerome, from 30 years in the past  Jerome, from 10 years in the past  Jerome, from 10 years in the future  Jerome, from 30 years in the future