The gravity would have to be reduced and not completely turned off simply because all the loose objects would just migrate around freely in zero G. It would become a safety issue to have all that shit just lying around randomly when the AG is turned back on as the crew awakes. So it needs to be about 15%.
Why do this, anyway..?
The reduction in gravity, as I've outlined previously has a very practical energy conservation practice. Ripley even remarks about it being activated when it's needed as they exit the gravitational influence of LV-426. Many of the ship's other systems are powered down when the crew are in hypersleep and as Ripley would tend to indicate, the artificial gravity could very well be, too, especially if there's no one awake aboard the ship.
Producing artificial gravity is going to be resource expensive and energy conservation is always a premium during space travel. As there's no need for it to be at full capacity when everyone is asleep, 10-20% would be all that's needed just to keep loose items in place. Friction will do the rest to keep them in place.
This goes for objects adhering to the ceiling as well.
What's more, the egg weighs, what? 10kg? Try just fastening a 10kg bag of rice to the ceiling, let's see how that works out. lol. Bring that figure down to 1kg and yes, you could have an object securely fastened to the ceiling and just hang there. Even if it grew there, which is what we are looking at here after a proto facehugger anchors itself in that location.
The low gravity, while all crew are in hypersleep also allows the proto hugger(s) to migrate a lot easier, fasten themselves into place on any surface, floors, walls... ceilings. It's not that hard to figure out an explanation. Sure, there's some licence required getting the proto huggers there in the first place, but hey...
I'm not the first person to mess around and alter the Alien's life cycle on a whim...
I've outlined it all in previous posts. Check it out.
EDiT: Something that just occurred to me that might be worthy of consideration: Variance in the Nostromo's payload 20/200 million tons can be attributed to Artificial Gravity changes. When the movie starts, we see the Nostromo with all its crew asleep and the 20 million figure is displayed as part of the opening text; about 10% of the actual figure. Later, as visible in a video display read out, the figure jumps to 200 million - meaning full gravity is now applied to the ship. lol. I think that's right.
-Windebieste.
