Why does water lose buoyancy in space?

During the space station's space lecture, astronaut Wang Yaping showed that the bubbles inside the water balloon in space do not float to the surface of the liquid, but only stay in the position of generation, that is, the buoyancy in space disappears.

Since this answer needs to involve gravity, we will first show that there is gravity in the Earth's orbit, but gravity is used to provide the centripetal force for the object to rotate around the Earth. Therefore, it is accurate to say that "the Earth's orbit is a microgravity environment". But because of customary usage, this answer still states that gravity is not exhibited in space.

Let's first review the description of buoyancy in junior high school physics: "The buoyancy of an object in a liquid is equal to the gravity of its discharge of liquid", so that in the absence of gravity in space, it is natural that there is no buoyancy.

Let's start from the liquid pressure formula P= ρgh and carefully analyze it. We learned in the hydrostatics of the second grade of primary school that the pressure of the liquid is generated by gravity [1]. In the water on the earth, there is no regularly shaped object, it is subjected to the pressure of the water from all directions, and because the pressure of the vertical plane cancels each other out, the combined force of the water subjected to the object is the pressure difference between the upper and lower bottom surfaces. Assuming that the upper and lower bottom areas are both S, then the combined forces F= ΔP×S = ρgΔh×S = ρgV, for general objects, can be calculated by integration. That is, the buoyancy comes from the pressure of the liquid, which essentially comes from gravity.

In space, water aggregates into water balls not because of gravity, but because of surface tension. Wang Yaping's two space lectures use a circular framework to constrain the water balloon for this reason. The interior of a water balloon does not distinguish between upper and lower as Earth does. That is to say, the internal pressure of the water balloon in space is equal everywhere, and the combined force of the objects in the water balloon is zero, so it will not float to the surface of the water balloon. The buoyancy is gone.

Resources:

Derivation of liquid buoyancy

By hiding stupidity