102,863
edits
Changes
From Nordan Symposia
Jump to navigationJump to searchCreated page with 'File:lighterstill.jpgright|frame ==Etymology== [http://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Mid...'
[[File:lighterstill.jpg]][[File:Ocean_Tides.jpg|right|frame]]
==Etymology==
[http://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English], time, from [http://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] tīd; akin to Old High German zīt time and perhaps to [[Greek]] daiesthai to divide
*Date: before [http://www.wikipedia.org/wiki/11th_Century 12th century]
==Definitions==
*1 a obsolete : a [[space]] of [[time]] : period
:b : a fit or opportune time : [[opportunity]]
:c : an ecclesiastical anniversary or festival; also : its season —usually used in combination <Eastertide>
*2 a (1) : the alternate rising and falling of the [[surface]] of the ocean and of water bodies (as gulfs and bays) [[connected]] with the ocean that occurs usually twice a day and is the result of differing [[gravitational]] forces exerted at [[different]] parts of the [[earth]] by another [[body]] (as the [[moon]] or [[sun]]) (2) : a less marked rising and falling of an inland body of water (3) : a periodic [[movement]] in the [[earth]]'s crust caused by the same [[forces]] that produce ocean tides (4) : a periodic distortion on one [[celestial]] body caused by the [[gravitational]] [[attraction]] of another (5) : one of the periodic movements of the [[atmosphere]] resembling those of the ocean and produced by [[gravitation]] or diurnal temperature changes
:b : flood tide 1
*3 a : something that fluctuates like the tides of the sea <the tide of [[public]] [[opinion]]>
:b : a surging movement of a [[group]] <a tide of opportunists>
*4 a : a [[flowing]] stream : current
:b : the waters of the ocean
:c : the overflow of a flooding stream
==Description==
'''Tides''' are the rise and fall of sea levels caused by the combined [[effects]] of the [[gravitational]] [[forces]] exerted by the [[Moon]] and the [[Sun]] and the rotation of the [[Earth]]. The tides occur with a period of approximately 12.5 hours and with an [[amplitude]] that is [[influenced]] by the alignment of the sun and moon and the shape of the [http://en.wikipedia.org/wiki/Bathymetry near-shore bottom].
Most coastal areas [[experience]] two daily high (and two low) tides. One of these high tides is at the point on the [[earth]] which is closest to the [[moon]]. The other high tide is at the [[opposite]] point on the [[earth]]. This is because at the point right "under" the [[Moon]] (the sub-lunar point), the water is at its closest to the Moon, so it [[experiences]] stronger [[gravity]] and is raised. On the opposite side of the Earth (the antipodal point), the water is at its farthest from the moon, so it is pulled less; at this point the Earth moves more toward the Moon than the water does—causing that water to "rise" ([[relative]] to the [[Earth]]) as well. In between the sub-lunar and antipodal points, the [[force]] on the water is diagonal or transverse to the sub-lunar/antipodal [[axis]] (and always towards that axis), resulting in low tide.
The [[sun]] also exerts a (less powerful) [[gravitational]] [[attraction]] on the [[earth]] which results in a secondary tidal effect. When the earth, [[moon]] and [[sun]] are approximately aligned these two tidal effects reinforce one another (resulting in higher highs and lower lows). This alignment occurs approximately twice a month (around the [http://en.wikipedia.org/wiki/Full_moon full] and [http://en.wikipedia.org/wiki/New_moon new moon]). These recurring, extreme tides are termed [http://en.wikipedia.org/wiki/Spring_tide spring tides]. The opposite, most moderate tides are termed [http://en.wikipedia.org/wiki/Neap_tide neap tides].
Tide [[prediction]] is important for coastal [[navigation]]. The [http://en.wikipedia.org/wiki/Intertidal_zone intertidal zone], the strip of seashore that high tide submerges and low tide exposes, is an important [http://en.wikipedia.org/wiki/Tide#Intertidal_ecology ecological product] of ocean tides.
While tides are usually the largest [[source]] of short-term sea-level fluctuations, sea levels are also subject to [[forces]] such as wind and barometric pressure changes, resulting in [http://en.wikipedia.org/wiki/Storm_surge storm surges], especially in shallow seas and near coasts.
Tidal [[phenomena]] are not [[limited]] to the oceans, but can occur in other [[systems]] whenever a [[gravitational]] field that varies in [[time and space]] is present. For example, the solid part of the Earth is affected by tides.[http://en.wikipedia.org/wiki/Tide]
[[Category: Earth Science]]
==Etymology==
[http://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English], time, from [http://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] tīd; akin to Old High German zīt time and perhaps to [[Greek]] daiesthai to divide
*Date: before [http://www.wikipedia.org/wiki/11th_Century 12th century]
==Definitions==
*1 a obsolete : a [[space]] of [[time]] : period
:b : a fit or opportune time : [[opportunity]]
:c : an ecclesiastical anniversary or festival; also : its season —usually used in combination <Eastertide>
*2 a (1) : the alternate rising and falling of the [[surface]] of the ocean and of water bodies (as gulfs and bays) [[connected]] with the ocean that occurs usually twice a day and is the result of differing [[gravitational]] forces exerted at [[different]] parts of the [[earth]] by another [[body]] (as the [[moon]] or [[sun]]) (2) : a less marked rising and falling of an inland body of water (3) : a periodic [[movement]] in the [[earth]]'s crust caused by the same [[forces]] that produce ocean tides (4) : a periodic distortion on one [[celestial]] body caused by the [[gravitational]] [[attraction]] of another (5) : one of the periodic movements of the [[atmosphere]] resembling those of the ocean and produced by [[gravitation]] or diurnal temperature changes
:b : flood tide 1
*3 a : something that fluctuates like the tides of the sea <the tide of [[public]] [[opinion]]>
:b : a surging movement of a [[group]] <a tide of opportunists>
*4 a : a [[flowing]] stream : current
:b : the waters of the ocean
:c : the overflow of a flooding stream
==Description==
'''Tides''' are the rise and fall of sea levels caused by the combined [[effects]] of the [[gravitational]] [[forces]] exerted by the [[Moon]] and the [[Sun]] and the rotation of the [[Earth]]. The tides occur with a period of approximately 12.5 hours and with an [[amplitude]] that is [[influenced]] by the alignment of the sun and moon and the shape of the [http://en.wikipedia.org/wiki/Bathymetry near-shore bottom].
Most coastal areas [[experience]] two daily high (and two low) tides. One of these high tides is at the point on the [[earth]] which is closest to the [[moon]]. The other high tide is at the [[opposite]] point on the [[earth]]. This is because at the point right "under" the [[Moon]] (the sub-lunar point), the water is at its closest to the Moon, so it [[experiences]] stronger [[gravity]] and is raised. On the opposite side of the Earth (the antipodal point), the water is at its farthest from the moon, so it is pulled less; at this point the Earth moves more toward the Moon than the water does—causing that water to "rise" ([[relative]] to the [[Earth]]) as well. In between the sub-lunar and antipodal points, the [[force]] on the water is diagonal or transverse to the sub-lunar/antipodal [[axis]] (and always towards that axis), resulting in low tide.
The [[sun]] also exerts a (less powerful) [[gravitational]] [[attraction]] on the [[earth]] which results in a secondary tidal effect. When the earth, [[moon]] and [[sun]] are approximately aligned these two tidal effects reinforce one another (resulting in higher highs and lower lows). This alignment occurs approximately twice a month (around the [http://en.wikipedia.org/wiki/Full_moon full] and [http://en.wikipedia.org/wiki/New_moon new moon]). These recurring, extreme tides are termed [http://en.wikipedia.org/wiki/Spring_tide spring tides]. The opposite, most moderate tides are termed [http://en.wikipedia.org/wiki/Neap_tide neap tides].
Tide [[prediction]] is important for coastal [[navigation]]. The [http://en.wikipedia.org/wiki/Intertidal_zone intertidal zone], the strip of seashore that high tide submerges and low tide exposes, is an important [http://en.wikipedia.org/wiki/Tide#Intertidal_ecology ecological product] of ocean tides.
While tides are usually the largest [[source]] of short-term sea-level fluctuations, sea levels are also subject to [[forces]] such as wind and barometric pressure changes, resulting in [http://en.wikipedia.org/wiki/Storm_surge storm surges], especially in shallow seas and near coasts.
Tidal [[phenomena]] are not [[limited]] to the oceans, but can occur in other [[systems]] whenever a [[gravitational]] field that varies in [[time and space]] is present. For example, the solid part of the Earth is affected by tides.[http://en.wikipedia.org/wiki/Tide]
[[Category: Earth Science]]
