 Why is there no feeling of acceleration in the elevator in the future?
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 can see a sort of foggy nothing surrounding the cockpit; it is probably the field that prevents passage through time from affecting us. 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. Doesn't hurt, and when you pull your arm back, you're still sound and uninjured. Then it comes to you slowly that you're actually traveling in time. "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. Maybe there is no machine, and it's just easier for us to imagine it. Anyhow, you sit there, watching nothing all around you, and no time, apparently, though there is a time effect back in the luggage space. That means you either carry a small time field with you, or you are catching a small increment of time from the main field. You suddenly realize that everything in the machine is wide open, yet you haven't seen any effects of air loss. Out there is neither time nor space, apparently. You still feel gravity, but I can't explain that, either. Maybe the machine has a gravity field built in, or maybe the time that makes your watch run is responsible for gravity. In spite of Einstein, you have always had the idea that time is an effect of gravity, and I sort of agree, still. You feel a dankish sort of air replace the stale air, and you breathe easier, though we're in complete darkness, except for the weak light in the machine, which always burns, and a few feet of rough dirty cement floor around. We have to walk up a flight of stairs, and there is an elevator waiting, fortunately with the door open. It gives out a coughing noise and the basement openings begin to click by us. There's no feeling of acceleration—some kind of false gravity they use in the future.
 The false gravity used in the interstellar civilization.
 The force is too fast to be felt.  The elevator doesn't actually move, only the scenery does.  It's moving slower in opposition to the gravity.  The false gravity used in the interstellar civilization.