Why sphere special? Why solar system spherical, why sun spherical and also all stars and planets also spherical?
In water column we observe single bubble of air slowly rising to surface. We can see it change shape little, but it is spherical. Why bubble spherical? It is same. When there is balance in pressure and difference in density, at that time, spherical shape is naturally formed. Why rising? If medium where bubble rising would continuously change density with depth, at that time, the bubble would find depth where density also in balance. Then it would hover in that depth. Even if poking it, it will return to balance. But in reality no such medium with infinite change in density. We observe different mediums with different density if change in density big. We have air, and water. Each different. There are natural boundary between density. Here it is water surface. Bubble naturally find balance on this boundary, because its density in between. We too observe transverse waves on the boundary waving like blanket. In infinite medium of same density, no up, or down, left or right, no perpendicular. At that time, no transverse waves, only longitudinal.
In water column we observe single bubble of air slowly rising to surface. We can see it change shape little, but it is spherical. Why bubble spherical? It is same. When there is balance in pressure and difference in density, at that time, spherical shape is naturally formed. Why rising? If medium where bubble rising would continuously change density with depth, at that time, the bubble would find depth where density also in balance. Then it would hover in that depth. Even if poking it, it will return to balance. But in reality no such medium with infinite change in density. We observe different mediums with different density if change in density big. We have air, and water. Each different. There are natural boundary between density. Here it is water surface. Bubble naturally find balance on this boundary, because its density in between. We too observe transverse waves on the boundary waving like blanket. In infinite medium of same density, no up, or down, left or right, no perpendicular. At that time, no transverse waves, only longitudinal.