Go and get a glass and a beer mat or similar to cover the glass.
Fill it with water and place the beer mat over it.
Upturn the glass and take your hand away from the beer mat. It stays in place.
The water does not push the beer mat away because atmospheric pressure stops it happening.
Why does it stop it happening?
Because the key to it is what atmospheric pressure is left inside the glass. Too little of it and it cannot push the water out to overcome the atmospheric external resistance to it.
Pretty simple really and shows a reality and also shows gravity to be utter nonsense.
And in one fell swoop, you have demonstrated your understanding science is fundamentally flawed.