A video showing laminar flow reminded me of a novel I read in my childhood, but I don't remember much of it, including the title or author.
What I do remember, however, is that there was a room with a "mirror", and said mirror actually turned out to be a window/portal into a region containing a city suspended in extremely slowed time - the protagonist returns several times to minor changes in the scenery, and he may have interacted with the slowed-time city to alter events, like a shootout, exploiting the difference in speed his "normal-time" status means in the slowed-time city. There is also a ambush that takes place just as the protagonist exits the slowed-time region, with some inner monologue telling that he [the protagonist or his assailant] did not know/remember that the vertical axis changes at the interface.
There is also a lingering image in my mind that the entire novel actually takes place on a gigantic spaceship, which is transporting the city to another system, and they used the time dilation technology to allow surreptitious transport while also reducing resource requirements.
I don't know when the novel was authored, but I probably read it in the early nineties, most likely translated to Hungarian.
To put things in a bullet point list:
- I'm looking for a novel, read early nineties, possibly written in the eighties
- I read it in Hungarian, but that was likely not the original language
- Involves a city suspended in slowed time
- Protagonist visits multiple times, sometimes using his "normal-time" status to make changes to events
- Access to slowed-time city is through a silvery surface that is initially mistaken as a mirror
- There is a fight where a key detail is that the vertical axis/axis of gravity changes at the interface surface
- The city is likely being transported to another star system in slowed time aboard a spaceship
