tidal deformation

Tidal deformation refers to the stretching and squeezing of celestial bodies due to gravitational forces from other astronomical bodies. For Earth, this primarily involves the gravitational pull of the Moon and the Sun, causing both its oceans and solid crust to deform.123

These deformations create "Earth tides," similar to ocean tides, with measurable vertical movements of the solid Earth's surface, typically less than a foot. The gravitational forces cause bulges on the sides of a celestial body facing towards and away from the other body. This process also leads to tidal evolution, where energy dissipation from these deformations can alter the rotation rates of bodies and the orbits of satellites. For example, tidal interactions are responsible for Earth's slowing rotation and the Moon's gradually expanding orbit.12