So pressurized gas of the type we can breath and the stuff birds fly in keeps us grounded?
So a bird that folds the wings in mid air will be directed downwards. No matter how you turn the bird - legs up or down - the pressure knows where the bird belongs when it is not moving the wings? If there is slightly more pressure on the birds upside that would work but since there is no gravity in flat earth all forces has to be made by air. With the upside down duck a pressure difference would then be detectable as a downward wind close to the duck. So if you place a upside down duck on a stick you will feel the wind since there is more air pressure above the duck than under. As some people have noticed if there is a difference in air pressure the wind tends to move in that direction.
In the gravity world you can pile air vertically and have a variation in pressure but that is due to stapling. In a steady state world heating air will make it expand (collide more frequently with surroundings and use more room) using more room with the same amount of molecules makes the hot air less dense and it will float upwards and so on.
I understand nothing of this is true on flat earth, just unproven theories. But that is a problem with everything. Ju have to test your theories or make general observations on gases and stuff to be certain enough to even build theories and be able to calculate and simulate things without actually making physical experiments for everything.
Having robust theories does not mean you are blind to new possibilities, but the new possibilities will hav to qualify and be tested for validity before put in the toolbox.
The same if you have a steel object of one kilo and carve out half of the mass and weld the hole. The air pressure knows the stuff inside the metal object is missing and makes less force on the object?
Why do flat earth have a problem with gravity but have no problems with completely unknown things like the edge of the flat world and the plate thickness and how all continents are lit up by the sun and sometimes in shade or darkness. One would suspect it is difficult to have complete darkness at one spot and horribly strong sunlight at the same time on a completely flat surface. That kind of lighting experiment can easily be tested. How come some people have full darkness and some sunshine but the ones in darkness are unable to see the lamp? Even if the lamp is flat is it sending out light only perpendicularly to the surface and can not be seen from an angle.
How come it appears the light source does not go off when on the sky. It allways hides behind the horizon before being turned off.
Do you have a theory for the light too?
Just apply a magic force to act on all objects in a specified direction and problem is solved.
As long as you supply alternative theories involving air pressure you get no where. It is so simple to experiment with air you have no chance explaining the downward force or motion that seems so common to all objects except ballons and smoke and hot air that travels upwards.
Why do you reject ours of studies made by people before you that was both qurious and smart enough to draw conclusions and even communicate the findings for others to prove right or wrong.
Flat earth causes a lot of problems that where already figured out. Now that you messed it upp you better come up with a model that can be accepted by a wide public.
