In the expansive reaches of the cosmos, countless planets adorn the celestial canvas, each holding its unique mysteries and marvels. However, within our solar system, a striking consistency prevails: all planets exhibit a spherical form.

As we all know, among the eight planets in the solar system, the planets are all spherical. Why is this? To understand this problem, we have to start with gravity.

In ancient times, before modern scientific discoveries, humanity struggled to understand the concept of the cosmos. Many civilizations believed that the sky and earth were separate and that the earth might be a cube with oceans cascading off its edges. However, these ideas were based on limited knowledge.

Thanks to modern physics, Sir Isaac Newton introduced the concept of gravity, which governs the behavior of celestial bodies. Over the centuries, scientists have come to understand the significant role that gravity plays in shaping the cosmos. In fact, the formation of stars is intricately linked to the gravitational pull they exert.

Newton's groundbreaking revelation shed light on the interconnectedness of all matter. He revealed that every object exerts a gravitational force on its surroundings, and this force is influenced by the mass of the objects and the distance between them. Therefore, gravity emerges as the guiding force that shapes the movement of celestial bodies throughout the universe.

Even between two people, there is a gravitational force. When people are in a space with very little gravity, the gravitational force between people will pull everyone's body into it. The gravitational force between two adults is greater than between two children at the same distance. It dominates the movement of every star in the universe from the beginning to the end.

For example, the moon revolves around the earth, which is caused by the gravitational force between the moon and the earth. The state of objects is mostly composed of several different forms such as solid, liquid, gas, and plasma.

The temperature of a celestial body commands the intensity of molecular vibrations within its substance. At lower temperatures, these vibrations diminish, leading to stronger bonds and solid formations. Conversely, to high temperatures of stars render matter into gaseous states, with particles diffusing in all directions. Under the sway of gravity, this diffusion manifests as a spherical shape.

In the universe, celestial bodies that have a diameter of over 500 kilometers generally have a circular shape, while those with a diameter of less than 500 kilometers often have irregular shapes. The reason for this is that when a celestial body reaches a diameter of over 500 kilometers, its own mass becomes significant, and a centripetal gravitational force is generated. This force is evenly distributed, resulting in a circular shape.

Objects in the universe are always subject to various gravitational forces, which affect their movement. Thus, celestial bodies rotate and revolve, and the centrifugal force caused by the rotation also shapes them into a spherical form.

The spherical shape of planets emerges to prove the profound influence of gravity on the cosmos. From the ancient ponderings of civilizations to the groundbreaking discoveries of modern physics, humanity's comprehension of the universe steadily advances, guided by the enduring principles that sculpt our celestial realm.