Question

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Which statement about synchronous rotation is true? (a) It can develop only on moons that are born with slow rotation. (b) It occurs commonly as a result of tidal forces exerted on moons by their parent planets. (c) It can develop only on moons with liquid oceans.

Short answer

(b) Synchronous rotation commonly results from tidal forces exerted by parent planets.

Step-by-step solution

Understand the Question

The question asks which statement about synchronous rotation is true. Synchronous rotation refers to a celestial body's rotational period being equal to its orbital period, resulting in the same face always pointing towards the object it is orbiting.

Analyze Option (a)

Option (a) suggests that synchronous rotation can only develop on moons that are born with slow rotation. While a slow initial rotation can lead to synchronous rotation, it is not the only condition under which synchronous rotation can develop, so this statement is not necessarily true.

Analyze Option (b)

Option (b) states that synchronous rotation commonly occurs as a result of tidal forces exerted on moons by their parent planets. Tidal forces are indeed a common cause of synchronous rotation, as they tend to slow down a moon's rotation rate until it matches the orbital period, causing one side of the moon to face the planet constantly. This statement is true.

Analyze Option (c)

Option (c) claims that synchronous rotation can only develop on moons with liquid oceans. This is incorrect, as the presence of a liquid ocean is not a necessary condition for synchronous rotation to occur. Many moons without oceans also experience synchronous rotation.

Select the Correct Answer

Based on the analysis, option (b) is the correct choice as it accurately reflects the common cause of synchronous rotation.

Key concepts

Tidal Forces

Tidal forces are crucial in understanding synchronous rotation in celestial mechanics. These forces occur due to the gravitational pull between two bodies, such as a planet and its moon.
When a moon orbits a planet, the gravitational force from the planet stretches the moon, creating a tidal bulge. This bulge experiences friction with the moon's rotation, acting like a brake.
Over time, this frictional interaction results in a phenomenon where the moon's rotation slows down until it matches its orbital period. This means that the moon always shows the same face to its parent planet.

• This effect is especially pronounced in moons that are relatively close to their planets.
• Tidal forces are not limited to moons with liquid oceans; solid body friction plays a significant role.

Understanding tidal forces helps us comprehend how bodies in space interact and influence each other's rotations and orbits.

Celestial Mechanics

Celestial mechanics is the branch of astronomy that deals with the movements and gravitational forces of celestial bodies. It explains the fundamental principles behind the motion of planets, moons, and other objects in space.
The principles of celestial mechanics are grounded in Newton's Law of Universal Gravitation and the laws of motion.
These scientific principles describe how massive objects, like planets and moons, exert gravitational force on one another, leading to their predictable orbits and rotations.

• Synchronous rotation is a key concept within celestial mechanics, showcasing the interaction between a moon's rotation and its orbit around a planet.
• By studying these interactions, we gain insights into how planets and their moons maintain stable orbits over vast periods.
• Advancements in celestial mechanics help us predict the movement of celestial bodies, which is essential for space exploration and understanding the universe.

These insights and predictions ultimately aid in exploring the solar system and beyond.

Moon Rotation

Moon rotation, particularly the phenomenon of synchronous rotation, plays a crucial role in our understanding of both our moon and other celestial moons. When a moon is in synchronous rotation, it has the same rotation period as its orbital period.
The consequence is that the moon's same hemisphere always faces its planet. This is exactly what we observe with our Moon and Earth.
Synchronous rotation occurs as a result of tidal locking, influenced heavily by tidal forces from the host planet.

• Moon rotation is not dependent on the presence of water bodies; rather, it is the gravitational interaction that is key.
• This phenomenon is common in the solar system, with many moons of planets like Jupiter and Saturn also being tidally locked.
• Studying moon rotation provides insights into the history and dynamics of the solar system's evolution.

Overall, the study of moon rotation and its effects helps astronomers understand not only the rotation dynamics of moons but also their internal composition and history.