When we look at the shapes of celestial bodies, including the Earth, we find that they are almost spherical. It seems that rotating celestial bodies become slightly ellipsoidal due to centrifugal force, and when we look at the oblateness, which indicates how elliptical a celestial body is, the Sun is 0.0009% of the Earth’s 0.3%, making it closer to a perfect sphere. The shape of the celestial body seems to vary depending on factors such as the strength of gravity and whether the material that makes up the body is dust/gas or rock.
https://diamond.jp/articles/-/356067
It would be easy to imagine something becoming a sphere in a world with no gravity, but when there is gravity, like on the Earth’s surface, it seems difficult to form a sphere. On Earth, it might be more appropriate to say that it is spherical or becomes spherical.
Is it when an object is in the air that we experience the closest state to weightlessness on Earth? The surface tension of liquids works to make the surface as small as possible, and since they do not come into contact with other objects in the air, small water droplets, mist particles, and small lava ejected from eruptions end up becoming spherical. Also, some objects become spherical by stacking thin, even layers around a small core, like pearls from Akoya oysters and hailstones, which are ice balls in the clouds.
Spherical shapes have the property that they are less likely to break because they have no corners, and because their surface area is small, they are less susceptible to the effects of external environments such as temperature and dryness. This may be why things that are important to organisms in protecting their species, such as fruits, seeds, and eggs, are spherical. When it comes to egg-laying, a spherical shape offers less resistance and is functional, and when it comes to seed dispersal, it may make sense that a spherical shape rolls easily. To digress a bit, chicken eggs are less likely to break if dropped horizontally rather than vertically.
https://www.natureasia.com/ja-jp/research/highlight/15229
Also, it seems that some small objects are almost spherical. The pollen of wind-pollinated plants such as cedars and cypresses is spherical, and has little resistance, so it can travel long distances on the wind and be scattered over a wide area. Cocci, which are spherical bacteria, and viruses, which are spherical viruses, may also be spherical in a similar sense.
In the living body, blood cells such as white blood cells and spherical proteins such as hemoglobin seem to have a spherical shape. When moving through blood, which has a higher viscosity than air, it is important that there is little resistance. It seems that it is meaningful for the nuclei of cells to be uniform and symmetrical.
https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-21K19079
Other examples include Giant Baronia, a giant single-celled organism; C60 fullerene, a soccer ball-shaped structure made up of carbon atoms; spherulites, which are polymer crystals that grow into spherical shapes; and ball lightning, floating, electrically charged, glowing spheres.
https://karapaia.com/archives/508606.html
地球上にある様々な球体状のものを調べていましたが、ミクロからマクロまで、ある種の効率や機能性を追求すると球という形が美しく合理的なのかもしれませんね。ある1点からの分布という意味では、重力場や電場も、球対称に広がっているようですし、球状は基本原理なのかもしれませんね。球体状、スゴイ。大いなる球体、地球スゴイ。
