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The tidal force or tide-generating force is the difference in gravitational attraction between different points in a gravitational field, causing bodies to be pulled unevenly and as a result are being stretched towards the attraction. It is the differential force of gravity, the net between gravitational forces, the derivative of gravitational potential, the gradient of gravitational fields. Therefore tidal forces are a residual force, a secondary effect of gravity, highlighting its spatial elements, making the closer near-side more attracted than the more distant far-side.
This produces a range of tidal phenomena, such as ocean tides. Earth's tides are mainly produced by the relative close gravitational field of the Moon and to a lesser extend by the stronger, but further away gravitational field of the Sun. The ocean on the side of Earth facing the Moon is being pulled by the gravity of the Moon away from Earth's crust, while on the other side of Earth there the crust is being pulled away from the ocean, resulting in Earth being stretched, bulging on both sides, and having opposite high-tides. Tidal forces viewed from Earth, that is from a rotating reference frame, appear as centripedal and centrifugal forces, but are not caused by the rotation.[2]
Further tidal phenomena include solid-earth tides, tidal locking, breaking apart of celestial bodies and formation of ring systems within the Roche limit, and in extreme cases, spaghettification of objects. Tidal forces have also been shown to be fundamentally related to gravitational waves.[3]
In celestial mechanics, the expression tidal force can refer to a situation in which a body or material (for example, tidal water) is mainly under the gravitational influence of a second body (for example, the Earth), but is also perturbed by the gravitational effects of a third body (for example, the Moon). The perturbing force is sometimes in such cases called a tidal force[4] (for example, the perturbing force on the Moon): it is the difference between the force exerted by the third body on the second and the force exerted by the third body on the first.[5]
- ^ "Hubble Views a Cosmic Interaction". nasa.gov. NASA. February 11, 2022. Retrieved 2022-07-09.
- ^ Matsuda, Takuya; Isaka, Hiromu; Boffin, Henri M. J. (2015), Confusion around the tidal force and the centrifugal force, doi:10.48550/ARXIV.1506.04085, retrieved 2025-02-14
- ^ arXiv, Emerging Technology from the (2019-12-14). "Tidal forces carry the mathematical signature of gravitational waves". MIT Technology Review. Retrieved 2023-11-12.
- ^ "On the tidal force", I. N. Avsiuk, in "Soviet Astronomy Letters", vol. 3 (1977), pp. 96–99.
- ^ See p. 509 in "Astronomy: a physical perspective", M. L. Kutner (2003).