How do inertia and gravity combine to keep Earth in orbit around the sun and the Moon in orbit around Earth and does the Earth rotate but not the Moon?
Yes, the moon rotates, but it does so much more slowly than Earth does. A "moon day" is around 29.53 Earth days. In other words, whereas Earth completes one rotation every 24 hours, the moon experiences a sunrise roughly every 709 hours. The axis of rotation is different from the magnetic poles. This difference creates force for the earth to rotate on its axis. The same is the case with all planets in the Solar System. Moon doesn't have Magnetic field; hence it does not rotate on its axis.Inertia and gravity combine to keep Earth in orbit around the sun and the moon in orbit around the Earth. A combination of gravity and inertia keeps the moon in orbit around the Earth. If there were no gravity, inertia would cause the moon to travel in a straight line. If not for Earth's gravity, inertia would cause the moon to move off through space in a straight line. In the same way, Earth revolves around the sun because the sun's gravity pulls on it while Earth's inertia keeps it moving ahead. As the Sun is very large, it exerts a great gravitational force on Earth. The Moon's inertia keeps it moving forward in its orbit, even though the Earth's gravity is constantly pulling it back. As a result, the Moon follows an elliptical path around Earth. The Moon's gravity also has an effect on Earth. The Moon's gravity pulls on the Earth's oceans, causing tides. The type of force that keeps the Earth in orbit around the Sun is gravity. Gravity is the weakest fundamental force in physics yet the mass of the Sun and the Earth generates enough gravity to keep the Earth anchored in its orbit. A planet orbits the sun at a constant speed due to gravity and inertia. The force of gravity pulls a planet toward the Sun. Inertia keeps a planet moving in a forward direction. When the force of gravity balances a planet's inertia the result is circular motion.