What force keeps planets in orbit around the Sun?

• A. Magnetic force
• B. Gravity
• C. Friction
• D. Normal force

Answer: (B)

Gravity is the force that keeps planets in orbit around the Sun. The Sun’s gravity pulls on each planet toward it, and as the planet moves forward through space, this inward pull bends the path from a straight line into a curved orbit. The result is a balance: the planet tries to move straight ahead, but gravity continually pulls it inward, creating a stable orbit rather than a fall into the Sun or a fly-off into space. In space there’s almost no air, so friction doesn’t slow the planet down, and normal force isn’t present because there’s no surface contact. Magnetic forces aren’t the driver here, since planetary orbits aren’t governed by magnetic interactions.