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(affect of Moon's gravity on Earth's seas, etc.)

The general term tide refers to the rise and fall of sea level, attributed to the effect of the Moon's gravity, being near enough that the gravitational force on Earth is appreciably different on the regions of the Earth's surface nearer the Moon and further from the Moon. The term is analogously used for the effects of the force of one body's gravity on another nearby body deforming its surface liquids as well as gases (atmosphere) and solids, the solid surface and within. The Earth experiences changes in the atmosphere (atmospheric tide) as well as the level of solid surface from these effects but they are not nearly as noticeable as that on the seas.

The apparent forces due to this difference in the effect of gravity by distance are termed tidal forces, and they have a number of observable astronomical effects.

The apparent forces can be expressed as a field, e.g., in terms of a potential (tidal potential, that may be symbolized by ΦTidal or in context, perhaps ΦT) analogous to gravitational potential, but expressing the difference between the gravitational potential associated with both bodies with that of one of the two.


Referenced by:
atmospheric tide
galactic tide
Love number
Q factor
tidal force
tidal locking