Question

planets often have moons that orbit them as the planets themselves move in orbit around the sun. which statement best constructs an explanation for this observable phenomenon?
a. objects with mass, like the sun, planets, and moon, exert gravitational force on other objects
b. space objects require an object around which to revolve or could remain in the solar system
c. larger objects always revolve around small objects (like moons, planets, and the sun)
d. planets are mostly empty space

Explanation:

• Option A: According to Newton's law of universal gravitation, every object with mass exerts a gravitational force on other objects. The Sun's gravitational force keeps planets in orbit around it, and a planet's gravitational force keeps its moons in orbit around it. This option provides a valid physical principle (gravitational force due to mass) that explains the observed orbital motions.
• Option B: Space objects do not "require" an object to revolve around to remain in the Solar System. For example, comets can orbit the Sun without orbiting a planet first. This statement is incorrect.
• Option C: In our Solar System, smaller objects (like moons) revolve around larger objects (like planets), and planets revolve around the even larger Sun. The statement "larger objects always revolve around small objects" is the opposite of what is observed in celestial mechanics.
• Option D: The fact that planets are mostly empty space has no direct relation to why moons orbit planets and planets orbit the Sun. This is an irrelevant statement for explaining the orbital phenomena.

Answer:

A. Objects with mass, like the Sun, planets, and moon, exert gravitational force on other objects