Rotation and revolution are terms used in the context of celestial bodies, such as planets and moons, to describe their movements. Here are five main differences between rotation and revolution:
Definition:
Rotation: Rotation refers to the spinning motion of a celestial body around its own axis. The axis is an imaginary line passing through the body’s center, and rotation results in day and night cycles as different parts of the body are exposed to sunlight.
Revolution: Revolution refers to the orbital motion of a celestial body around another body, typically around a star (e.g., a planet orbiting a star). The path followed by the celestial body in its orbit is an elliptical or nearly circular trajectory.
Axis of Rotation:
Rotation: The axis of rotation is an imaginary line passing through the center of the celestial body. Earth, for example, rotates around its axis, which is inclined at an angle relative to its orbital plane.
Revolution: The axis of revolution is the line around which a celestial body orbits another body. For Earth, this is an imaginary line perpendicular to the orbital plane.
Time Scale:
Rotation: The time it takes for a celestial body to complete one full rotation on its axis is known as its rotational period or day. For Earth, this is approximately 24 hours.
Revolution: The time it takes for a celestial body to complete one full orbit around another body is known as its orbital period or year. For Earth, this is approximately 365.25 days.
Effects on Day and Night:
Rotation: Rotation causes the alternation of day and night. As a celestial body rotates, different parts of its surface are exposed to sunlight, resulting in the cycle of day (sunlit) and night (shadowed).
Revolution: Revolution does not directly cause day and night. Instead, it influences the changing seasons due to variations in the angle and intensity of sunlight received by different parts of the celestial body during its orbit.
Observable Motion:
Rotation: The motion of rotation is observable as the spinning or axial rotation of a celestial body. It is responsible for phenomena like the apparent movement of the Sun across the sky and the changing positions of stars during the night.
Revolution: The motion of revolution is observable in the changing positions of a celestial body in the sky relative to background stars or other celestial objects. It is responsible for the annual motion of the Sun along the ecliptic and the changing positions of planets.
In summary, rotation refers to the spinning motion of a celestial body around its own axis, leading to day and night cycles, while revolution involves the orbital motion of a celestial body around another body, resulting in changes in its position in the sky over time. Both rotation and revolution are fundamental motions that contribute to the dynamic behaviour of celestial bodies in the universe.