The answer lies in three fundamental physical principles: motion, gravity and inertia.
Motion simply means movement. In space, objects move at extremely high speeds compared to what we experience on Earth. For example, Earth travels around the Sun at about 107,200 kilometres per hour. In space, speeds are often measured in kilometres per second rather than per hour, showing how rapidly celestial bodies move.
Gravity is the force associated with mass that pulls objects toward each other. According to modern physics, gravity occurs because massive objects bend or warp spacetime around them. A common analogy is placing a heavy ball on a stretched sheet — the sheet curves, causing smaller objects to roll toward the heavier one.
Importantly, gravity works both ways. Earth pulls on a ping-pong ball, but the ping-pong ball also pulls on Earth with the same force. However, because Earth has vastly greater mass, the movement of the ping-pong ball is noticeable while Earth barely moves. This principle explains how large celestial objects influence one another’s motion.
Inertia is the tendency of an object to keep moving in the same direction unless a force changes its motion. For instance, a cup sitting on a desk will remain still unless someone pushes it. If pushed, it will move in a straight line unless another force — such as gravity — changes its path.
These three principles explain why planets orbit the Sun. Planets are constantly being pulled toward the Sun by gravity, but they also have forward motion and inertia. Because they move so fast, they keep “missing” the Sun as they fall toward it, creating stable orbits rather than crashing into it.
The Sun itself is also part of a much larger orbital system. It does not remain stationary in space. Instead, it orbits Sagittarius A*, the supermassive black hole at the centre of the Milky Way galaxy. The entire Solar System moves with the Sun through this orbit.
The Milky Way itself is also in motion within the Local Group of galaxies, a collection of galaxies spanning millions of light-years. On even larger scales, galaxies orbit one another within clusters and superclusters.
In this way, the universe is a vast network of objects in constant motion — moons orbit planets, planets orbit stars, stars orbit galactic centres and galaxies move within larger cosmic structures. Motion, gravity and inertia work together to keep these objects locked into complex and stable patterns.
Because of these forces, massive objects like the Sun cannot simply float away or remain motionless. Instead, they are part of an intricate cosmic dance that governs the structure and movement of the universe.
