Earth tide

The largest body tide constituents are semi-diurnal, but there are also significant diurnal, semi-annual, and fortnightly contributions.

If, for example the Moon is directly over 90° W (or 90° E), the red areas are centred on the western northern hemisphere, on upper right.

Ocean tides are a consequence of tangent forces (see: equilibrium tide) and the resonance of the same driving forces with water movement periods in ocean basins accumulated over many days, so that their amplitude and timing are quite different and vary over short distances of just a few hundred kilometres.

At first- and third-quarter phases of the moon, lunar and solar tides are perpendicular, and the tidal range is at a minimum.

Finally, fortnightly and semi-annual tides have zonal deformations (constant along a circle of latitude), as the Moon or Sun gravitation is directed alternately away from the northern and southern hemispheres due to tilt.

Since these displacements affect the vertical direction, the east-west and north-south variations are often tabulated in milliarcseconds for astronomical use.

[4][5] The semidiurnal amplitude of terrestrial tides can reach about 55 cm (22 in) at the equator which is important in geodesy using Global Positioning System, very-long-baseline interferometry, and satellite laser ranging measurements.

Among the effects that need to be taken into account are circumference deformation for circular accelerators and also particle-beam energy.

For example, it is due to body tides in the Moon that it is captured into the 1:1 spin-orbit resonance and is always showing us one side.

[citation needed] Body tides in Mercury make it trapped in the 3:2 spin-orbit resonance with the Sun.

[12] For the same reason, it is believed that many of the exoplanets are captured in higher spin-orbit resonances with their host stars.