I would like to know what "the expanse between departure and arrival when you’re seemingly nowhere, defined by another kind of time" means in the following sentences:
The bus was almost full now, and the driver climbed in, cigarette glued to his lips, and off we went. We vibrated with the rhythm of the clattering engine. Sun streamed on to my face and, outside, the spire of the city’s symbol – Stalin’s Palace of Culture – reached so high into the soft-blue sky it made your neck hurt to look at it. I was strangely elated. I had always liked the act of leaving, the expanse between departure and arrival when you’re seemingly nowhere, defined by another kind of time. This journey reminded me of the ride I’d taken four years earlier: the day I’d taken the train to Warszawa for the first time by myself, to come to the capital, to leave my old self behind. I’d stood on the platform with Granny, two large suitcases next to us, a handkerchief in her gloved hand dabbing her glassy eyes. She didn’t want me to go, but she didn’t say anything. I was eighteen, itching to leave. I’d kissed her hastily and got on the train, feeling selfish to be leaving her, dragging the suitcases to my compartment, passing smoking soldiers leaning out of the window in the narrow corridor. I’d settled into my compartment, between men in worn suits and women in hats, drinking tea from flasks and peeling apples, and eating boiled eggs wrapped in white lace cloths like christened babies. The train had moved off, and I’d fallen into a lull, villages sunk in forests rushing past. Selfish. Growing into yourself is nothing but that.
In this novel which is set in the 1980's in Poland under the socialist regime, where homosexuality was socially unacceptable, the protagonist Ludwik (a university graduate) left Poland in 1981 to live in the United States of America. And he remembers what it was like back then in Poland, where he went to the agricultural camp (which was mandatory for college graduation). On the way to the camp, Ludwik remembered his first time going to Warsaw by himself to come to the university, four years ago.
In this part, I am not sure whether it is right to see "expanse" as a temporal concept, rather than a terrestrial concept. I had seen "expanse" to mean "a stretch of land," but this "expanse" is modified by the "when" clause, so I cannot be sure what to make of this "expanse."
I am an English learner from South Korea, so thank you for your patience in advance as I may not know obvious things. I would very much appreciate your help. :)