It's a good question. There's been very little data on partial gravity, but what there is shows that a pronounced physical sense of "down" and "up" doesn't kick in until about 1/5g [1]. That said, a horizon and big rock underfoot are powerful visual cues, and it's anyone's guess what it would feel like to walk on a small celestial body like that. There's one good way to find out!
> "a gravitational field of about 0.15 g is necessary to provide effective orientation information"
That's slightly less than lunar gravity (0.165 g). But, it's about the minimum amount needed to be able to use gravity to detect orientation, and is not necessarily enough to detect it reliably. That's thought to be one reason astronauts fell so often on the moon, although there were certainly other factors as well.
The paper also observes:
> Benson [30] showed that 0.22 g was not adequate to provide a vertical reference during experiments in the International Microgravity Laboratory (IML-1) on board Spacelab and Clément et al. [31] showed that in microgravity, 0.5 g provided by a centrifuge was enough to produce a perceived tilt of 90°. These values suggest that indeed it is likely to be the case that even after adaptation to a microgravity environment, forces in excess of 0.15–0.3 g are required to provide a behaviourally useful gravitational reference.
To answer your question, since vision is an important part of our orientation mechanism (also analyzed in the linked paper), it's likely that astronauts on the moon would have more difficulty with their eyes closed. Not necessarily that they'd have no sense of up at all, but that it wouldn't necessarily be accurate, so if they tried to walk with their eyes closed, they'd be much more likely to fall.
It's possible. There seems to be a lot of individual variability around this threshold, although as usual the problem is a severe lack of data on the effects of partial gravity on anything.
Alan Shephard and Ed Mitchell reported that the 7 degree tilt of their lunar module interfered with their sleep, which suggests it was noticeable. But it would be hard to point to something in their cabin arrangements that didn't interfere with sleep.
One unfortunate downside of tech limitations in the show The Expanse is that there's no good way to do low-g. Part of the first season is set on belter dwarf planets where the gravity would've been under 5% G.
They do show the coriolis effects on Eros(https://expanse.fandom.com/wiki/Coriolis_Effect).
But yes, for the most part we should see more awkward movement at such low g. Both Eros and Ceres are at 0.3g
Oh I didn't even realize they spun the asteroids for gravity. I'd assumed they were relying on the natural gravity, which would have no Coriolis but would also mean only 0.03G on Ceres and even less on Eros.
In the books especially, they talk about going "up" into the cheaper, lower-gravity areas, or "down" to the docks, where outsiders and tourists were more likely to be. The books also have more to say about cladding around Ceres and Eros so that they wouldn't fly apart when spun, and Tycho Station's part in engineering that.
I just wanted to ask about that: if they spun them for gravity, wouldn't they fly apart? Because you'd have a meaningful amount of gravity pulling the rocky surface away from the asteroid.
But even cladding the surface to keep it together, you're talking about many tons and tons of rock you suddenly need to keep together. At that point, why not make a space habitat completely separate from the asteroid? It seems silly to put your base on the gravity of an asteroid and then try to undo the gravity of that asteroid.
As long as a chunk of rock is in one piece (rather than a pile of rubble) it's not going to get pulled apart by a modest amount of gravity. Look at any cliff overhang (or the underside of any boulder) for proof. So the trick is just to pick an asteroid that is not a rubble pile.
Look at cliff erosion. Look at moons and asteroids being pulled apart just by differences in gravity between its different sides. I strongly doubt any asteroid of meaningful size is going to be strong enough to withstand meaningful rotational gravity.
[1] https://www.sciencedirect.com/science/article/abs/pii/S03043...