For one, your internal organs naturally, on Earth, place downward pressure. Your blood vessels constrict and squeeze in attempt maintain the same pressure in both your head and feet. When you stand up quickly, we have blood vessel reflexes that prevent the blood from quickly draining from your head. Our entire bodies are innervated with muscle that works to fight against gravity. If you read any accounts from people in zero gravity, it feels *a lot* different than just "standing" there. The point is, either gravity exists, the place mimics gravity, or the channelers "assume" gravity, and therefore sort of create it for that specific environment.

Regardless of the reason, gravity exists there, otherwise everyone would have been shouting "What the fuck? why does everything feel so goddamn weird?" They'd also probably go floating off the platform with the slightest adjustment of their feet. You don't need a reference point to know that "down" is towards your feet.

Your point was that there was no gravity, and that the platform was rising up, which to an outside observer traveling upwards at the same velocity as the skimmming platform, would at first appear indistinguishable from falling (i.e. Aiel goes off edge, stays in same location, and platform rises up). My entire point is that yes, gravity does exist (for reasons mentioned above), so yes, the Aiel did fall. Whether gravity exists because it's a property of the Skimming place, or because the Channeler imposes that due to his own preconceptions is something that's not clear.