- How do gravitational effects between the Sun and a planet differ at the perihelion and the aphelion positions of the orbit of a planet? __

t perihelion (a planet's closest point to the Sun), the gravitational force between the Sun and the planet is *stronger* than at aphelion (the furthest point). This is a direct consequence of Newton's Law of Universal Gravitation, which states that the force of gravity between two objects is inversely proportional to the square of the distance between their centers. Since the planet is closer to the Sun at perihelion, the denominator in the gravity equation is smaller, resulting in a larger force.<br /><br />While the force of gravity is greater at perihelion, the *speed* of the planet is also greater at this point. This increased speed is a consequence of the conservation of angular momentum. As the planet moves closer to the Sun, it trades gravitational potential energy for kinetic energy, resulting in a higher orbital velocity.<br />