How does the Sun’s gravity keep Earth and the other planets in orbit?

The Sun’s immense mass—which accounts for more than 99 percent of the total mass in the solar system—creates a powerful gravitational force that acts as an inward, or centripetal, force on the planets.12

This gravitational pull is essential for maintaining planetary orbits. Without it, a planet would follow the law of inertia and travel in a straight line at a constant speed, moving tangentially away from its orbit. The Sun’s gravity continuously overcomes this inertial tendency, pulling the planet inward and forcing it to follow a curved path.13

In this context, an orbiting planet is essentially in a state of constant, free-falling motion toward the Sun, balanced by its orbital velocity. This interaction is described by Newton’s law of gravitation, which explains that the force between two bodies depends on their masses and the distance between them, diminishing as the inverse square of that distance.13