Pressure comes about because of gravitational pull on the liquid. If the fluid has no weight, then the fluid molecules will not be pressing against the bottom and sides of its container, and against one another.
On Earth, we can simulate zero gravity conditions in the cup simply by dropping it. When both the water and the cup are free falling together, the water stops pressing against the cup. The water basically “hovers” in the cup and becomes “weightless”. NO WEIGHT, NO PRESSURE. This explains why the water stops leaking out through the hole once the cup is dropped.
Likewise, hydrostatic pressure does not exist in outer space, or at the International Space Station (ISS). In fact, water hovers in the air as water balls in zero-g conditions. (Click here for proof)
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