Which force primarily keeps planets in orbit around the Sun?

Which force primarily keeps planets in orbit around the Sun?

• A. Friction
• B. Magnetic attraction
• C. Electromagnetic force
• D. Gravity

Answer: (D)

Gravity is the force that keeps planets in orbit around the Sun. The Sun’s great mass pulls on each planet, bending the planet’s forward motion into a curved path. If a planet moves fast enough, gravity pulls it in but it doesn’t let it fall straight into the Sun, so it stays in an orbit. In space there’s very little friction, so there isn’t a force to slow the planet down and pull it inward in the way friction would. The other forces mentioned—friction would actually prevent a stable orbit by slowing and eventually dragging objects inward, and magnetic or electromagnetic forces are not the main influence on planets since they’re largely neutral and these forces act differently at planetary scales. Gravity is the dominant force that keeps planets circling the Sun.

Gravity is the force that keeps planets in orbit around the Sun. The Sun’s great mass pulls on each planet, bending the planet’s forward motion into a curved path. If a planet moves fast enough, gravity pulls it in but it doesn’t let it fall straight into the Sun, so it stays in an orbit. In space there’s very little friction, so there isn’t a force to slow the planet down and pull it inward in the way friction would. The other forces mentioned—friction would actually prevent a stable orbit by slowing and eventually dragging objects inward, and magnetic or electromagnetic forces are not the main influence on planets since they’re largely neutral and these forces act differently at planetary scales. Gravity is the dominant force that keeps planets circling the Sun.