Explain what occurs during tidal friction?
During tidal friction, the gravitational forces exerted by the moon or the sun on Earth, or other celestial bodies on each other, cause a deformation or bulge on these bodies. This deformation creates a tidal bulge, leading to the phenomenon of tides.
To understand tidal friction, let's start with the basic concept of tidal forces. Tidal forces arise due to the differential gravitational pull on an object from another body across its diameter. The strength of these tidal forces depends on the mass and distance between the two bodies. Gravity weakens with distance, so the side of the object closer to the other body experiences a stronger gravitational pull, while the side farther away experiences a weaker pull.
Now, when an object, such as Earth, is subjected to tidal forces from the moon or the sun, these forces induce tidal bulges. One bulge is formed on the side of the object facing the other body (the "direct" or "sublunar" bulge), and another bulge forms on the opposite side (the "opposite" or "antipodal" bulge).
As Earth rotates, the tidal bulges move around the planet, causing the daily occurrence of two high tides and two low tides. This continuous movement of tidal bulges creates a frictional force between the ocean water and the seabed, or between Earth's solid parts. This friction converts the kinetic energy of the rotating Earth-moon system into heat and dissipates it.
The dissipation of energy through tidal friction leads to several consequences. First, it decelerates the rotation of the Earth, causing the length of a day to gradually increase over geologic timescales. During the past billion years, the length of a day has increased by about 2 milliseconds.
Secondly, tidal friction leads to a transfer of angular momentum from the Earth's rotation to the moon's orbit, causing the moon to gradually move farther away from the Earth. This phenomenon is known as lunar or tidal acceleration.
In summary, tidal friction refers to the dissipative effects caused by the continuous movement of tidal bulges on a rotating body. These effects include the deceleration of Earth's rotation and the gradual increase in the distance between the Earth and the moon.