Tide

The tide is the regular rising and falling of the ocean's surface caused by changes in gravitational forces external to the Earth. The main changing gravitational field is due to the Moon while a lesser field is caused by the Sun.

Other tides

In addition to oceanic tides, there are atmospheric tides as well as terrestrial tides (land tides), affecting the rocky mass of the Earth. Atmospheric tides are negligible, drowned by the much more important effects of weather and the solar thermal tides. The Earth's crust, on the other hand, rises and falls imperceptibly in response to the Moon's solicitation. The amplitude of terrestrial tides can reach about 55 cm at the equator (15 cm of which are due to the Sun), and they are nearly in phase with the Moon (the tidal lag is about two hours only) - which means that they reinforce the apparent oceanic tides.

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While negligible for most human activities, terrestrial tides need to be taken in account in the case of some particle physics experimental equipments (Stanford online). For instance, at the CERN or SLAC, the very large particle accelerators are designed while taking terrestrial tides into account for proper operation. Indeed, despite their kilometre-range dimension, centimetric deformations might lead to their malfunctioning as a physics experimental apparatus. Among the effects that need to be taken into account are : circumference deformation for circular accelerators, particle beam energy.

Related Topics:
Particle physics - CERN - SLAC - Particle accelerator

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The first mathematical explanation of tidal forces was given in 1687 by Isaac Newton in the Philosophiae Naturalis Principia Mathematica.

Related Topics:
1687 - Isaac Newton - Philosophiae Naturalis Principia Mathematica

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Yet Lucio Russo, an Italian scholar, in his book Flussi e Riflussi (yet to be published in English) demonstrates that hellenistic Greeks already had understood tides in terms of the gravitational pull of the Moon and the Sun. In particular it emerges that Seleuc of Babylon (2 B.C.) used his gravitational explanation to prove that it was the Earth to revolve around the Sun, not the opposite.

Related Topics:
Greek - Moon - Sun - Seleuc of Babylon - Earth

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Tsunami, the large waves that occur after earthquakes, are sometimes called tidal waves, but have nothing to do with the tides. Other phenomena unrelated to tides but using the word tide are rip tide, storm tide, and hurricane tide. The term tidal wave appears to be disappearing from popular usage.

Related Topics:
Tsunami - Rip tide - Storm tide - Hurricane tide

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