Tide - Wikiparency

# Tide Tides are the ocean's response to the gravitational pull of the [[Moon]] and [[Sun]]. What raises them is not gravity itself but its *difference* across the [[Earth]] — the near side is pulled harder than the centre, the far side less, so the ocean bulges at both ends. That is why most coasts see two high tides a day rather than one — a [[Gravity|gravitational]] gradient, not a pull. ## Microsim — p5.js Sidecar: `Tide.p5.js` · route leaf: `microsim/p5js/Tide__20260910T0400Z`. Built to the Betterfire Standard v0 (single `ARTICLE` constant, HUD title and Wikitube URL, control hints, parameter readout and equation). | Control | Does | |---------|------| | `moon slider` | moon phase around the orbit | | `sun slider` | solar contribution | | `[a]` | animate the orbit | *What to watch:* Walk the Moon around its orbit and the two bulges follow. Bring the Sun into line and the range jumps to spring tide; put it at right angles and it collapses to neaps. ## Two bulges, and the fortnightly beat Because the tidal force falls off as the cube of distance rather than the square, the nearer Moon dominates despite the Sun's vastly greater mass — roughly twice the effect. When the two line up at new and full [[Moon|moon]] their bulges add and tides are large: spring tides. At the quarters they partly cancel: neap tides. The fortnightly alternation is one of the most reliable rhythms in nature and was predicted from [[Newton's_laws_of_motion|Newtonian]] mechanics long before anyone could compute the ocean's actual response. ## Why real tides are not the textbook picture An equilibrium ocean would show a modest, uniform bulge. Real tides are far larger in some places and nearly absent in others because the ocean basins have their own resonant periods, and continents get in the way — the bulges cannot simply travel westward, so instead the tide rotates around amphidromic points — [[Coriolis_force|rotationally]] organised — where the range is almost zero. That is why the Bay of Fundy sees metres and the Mediterranean centimetres — [[Oscillation|resonance]], not latitude. Tidal [[Energy]] dissipated by friction is also the main mixing supply for [[Thermohaline_circulation|deep circulation]], which makes tides part of the ocean's overturning budget rather than a coastal curiosity. **Reads with:** *Introduction to Physical Oceanography (Robert H. Stewart, 2008)* — [OTL record](https://open.umn.edu/opentextbooks/textbooks/introduction-to-physical-oceanography) · [download](https://github.com/introocean/introocean-en/releases/tag/v20200229) · CC BY-NC-SA. Section 7 of the [[PORTAL_Thury_Hydrodynamics_Apex_Spine|Apex Spine]] book shelf. **On the spine:** [[Wind_wave]] · [[Thermohaline_circulation]] · [[Moon]] · [[Coriolis_force]] · [[WT!Thury_Hydrodynamics_Compendium]].  *Linked from the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]], section 34, Waves and tides.*   **Microsim — three.js (Wikitube framework):** *Tide* <div class="wt-sim" data-src="https://wikitube-3d-microsims.netlify.app/thury/Tide.html" data-title="Tide"></div> *Built from `MICROSIM_GUIDE/specs/variants/Tide.json`; part of the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]] set.*  ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Tide) : [Wikitube](https://en.wikitube.io/wiki/Tide) ## Previous hub tags Hubs: `Life_Physics`, `Systems`. Portals: [[PORTAL_Thury_Hydrodynamics_Apex_Spine]], [[PORTAL_WT!Thury_Hydrodynamics_Compendium]], [[PORTAL_Physics]]. --- *Book-section wave · 2026-09-10 · article + p5 microsim shipped together.*