Editing Tide (section)

=== Range variation: springs and neaps ===
{{further|Tidal range}}
[[File:Tide schematic.svg|thumb|left|alt=Spring tide: the Sun, moon, and earth form a straight line. Neap tide: the Sun, moon, and earth form a right angle.|The types of tides]]

{{anchor|springtide|Spring}}The semi-diurnal range (the difference in height between high and low waters over about half a day) varies in a two-week cycle. Approximately twice a month, around [[new moon]] and [[full moon]] when the Sun, Moon, and Earth form a line (a configuration known as a [[syzygy (astronomy)|syzygy]]<ref>{{Cite book |title=Mathematical astronomy in Copernicus's De revolutionibus |volume=1 |first1=Noel M. |last1=Swerdlow |first2=Otto |last2=Neugebauer |publisher=Springer-Verlag |date=1984 |isbn=0-387-90939-7 |page=76 |url=https://books.google.com/books?id=4YDvAAAAMAAJ&q=Syzygy |via=[[Google Books]] |access-date=2020-11-22 |archive-date=2023-09-16 |archive-url=https://web.archive.org/web/20230916153030/https://books.google.com/books?id=4YDvAAAAMAAJ&q=Syzygy |url-status=live }}</ref>), the [[tidal force]] due to the Sun reinforces that due to the Moon. The tide's range is then at its maximum; this is called the '''spring tide'''. It is not named after [[Spring (season)|the season]], but, like that word, derives from the meaning "jump, burst forth, rise", as in a natural [[Spring (hydrosphere)|spring]]. 
Spring tides are sometimes referred to as ''syzygy tides''.<ref name="Harris1981">{{cite book |last=Harris |first=D.L. |title=Tides and Tidal Datums in the United States |publisher=[[United States Army Corps of Engineers]], Coastal Engineering Research Center |series=Special report (Coastal Engineering Research Center (U.S.))) |year=1981 |url=https://books.google.com/books?id=kbIse3HQ74wC&pg=PA32 |access-date=2021-08-24 |page=32 |via=[[Google Books]] |archive-date=2023-09-16 |archive-url=https://web.archive.org/web/20230916153028/https://books.google.com/books?id=kbIse3HQ74wC&pg=PA32 |url-status=live }}</ref>

{{anchor|Neap}}When the Moon is at [[Gibbous|first quarter]] or third quarter, the Sun and Moon are separated by 90° when viewed from the Earth (in [[quadrature (astronomy)|quadrature]]), and the solar tidal force partially cancels the Moon's tidal force. At these points in the lunar cycle, the tide's range is at its minimum; this is called the '''neap tide''', or '''neaps'''. "Neap" is an Anglo-Saxon word meaning "without the power", as in ''forðganges nip'' (forth-going without-the-power).<ref>{{cite OED2|neap²}} Old English (example given from AD 469: ''forðganges nip'' – without the power of advancing). The Danish ''niptid'' is probably from the English. The English term neap-flood (from which neap tide comes) seems to have been in common use by AD 725.</ref>
Neap tides are sometimes referred to as ''quadrature tides''.<ref name="Harris1981"/>

Spring tides result in high waters that are higher than average, low waters that are lower than average, "[[slack water]]" time that is shorter than average, and stronger tidal currents than average. Neaps result in less extreme tidal conditions. There is about a seven-day interval between springs and neaps.

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<gallery class="center">
File:High tide sun moon same side beginning.png|''Spring tide:'' Sun and Moon on the same side (0°)
File:Low tide sun moon 90 degrees.png|''Neap tide:'' Sun and Moon at 90°
File:High tide sun moon opposite side.png|''Spring tide:'' Sun and Moon at opposite sides (180°)
File:Low tide sun moon 270 degrees.png|''Neap tide:'' Sun and Moon at 270°
File:High tide sun moon same side end.png|''Spring tide:'' Sun and Moon at the same side (cycle restarts)
</gallery>
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