Final answer:
Earth maintains its orbit due to the balance of gravitational force from the Sun and its own inertia, acting as a gyroscope that is slowly precessing. The perception of Earth being the center of the solar system is due to our ground-based reference frame.
Step-by-step explanation:
Earth continues to orbit the Sun in a generally circular path primarily because of two forces: gravity and inertia. While gravity, an attractive force between two masses, pulls Earth toward the Sun, Earth's inertia, stemming from its motion and mass, wants to keep it moving in a straight line at a constant speed. This dynamic leads to Earth's nearly circular orbit around the Sun.
Additionally, Earth acts like a gigantic gyroscope with angular momentum along its axis pointing at Polaris, the North Star. However, the Earth is slowly precessing due to the torque exerted by the Sun and the Moon on its nonspherical shape, a cycle that takes about 26,000 years to complete. This precession is separate from the actual orbital path of the Earth around the Sun.
Answering part b of the GRASP CHECK, Earth appears to be the center of the solar system because in our reference frame, celestial bodies like the sun, moon, and planets seem to circle Earth, giving the illusion of a geocentric model.