Tides Explained: Why Two a Day, Spring Tides, Tidal Bores and the Bay of Fundy

The Moon cannot lift the ocean. Its tide-raising pull is only about one nine-millionth of Earth's gravity, far too weak to raise water against it. And yet, twice a day, whole bays drain and fill again. In the Bay of Fundy the water climbs more than 15 metres, while in the middle of some seas there are points where the tide barely rises at all. This video follows the hidden mechanism behind the tide, step by step, with a cutaway or a map for each part. What you'll learn: The sideways pull: why the Moon's pull on the sea matters only along the surface, and why "the Moon lifts the ocean like a magnet" is the wrong picture. The second bulge: why there is a high tide on the side of Earth facing away from the Moon, why it is not flung out by Earth's spin, why high tides come about 12 hours 25 minutes apart and about 50 minutes later each day, and why the bulges run slightly ahead of the Moon. Spring and neap tides: why the Sun pulls on Earth about 175 times harder than the Moon but raises a tide less than half as big, why spring tides have nothing to do with the season, what a king tide is, and how a storm surge on top of a high tide becomes a storm tide. One tide or two: semidiurnal, mixed and diurnal tides, from the east coast of North America to the Pacific coast and the Gulf of Mexico, and how the Moon's tilt makes one high tide tall and the next one small. Tides without tides: why continents break the two-bulge picture, how the tide becomes a huge wave swinging around each ocean basin, and what amphidromic points are. Resonance: why the Bay of Fundy and the Gulf of Maine slosh with a natural period of about 13 hours, and why that makes their tides some of the largest on Earth. Tidal bores: why a single wave marches upstream on rivers like the Qiantang in China and the Severn in England, why the river runs backwards behind it, and how dredging erased the Seine's bore. The tidal brake: how tidal friction lengthens Earth's day, why the Moon drifts about 3.8 cm farther away every year, what 400-million-year-old corals tell us about shorter days, and why the Moon always shows us one face. More waves and water on this channel: "Ocean Wave Types Explained: From Swell to Rogue Waves and Hidden Internal Waves", and our storm surge episode for what happens when a storm lands on a high tide. Chapters: 0:00 Tides 0:31 Sideways Pull 1:37 Second Bulge 3:05 Spring and Neap 4:31 One Tide or Two 5:37 Tides Without Tides 6:56 Resonance 7:59 Tidal Bores 9:03 Tidal Brake 10:11 Tides Main sources: NOAA National Ocean Service: Tides and Water Levels tutorial; What is a spring tide?; Perigean spring tide; What is a King Tide?; Where is the highest tide? NOAA CO-OPS: Our Restless Tides (the tide-raising forces and the tractive force) NOAA National Hurricane Center: Storm Surge Overview NASA Science: Tides; Tidal Locking; F. Espenak (NASA GSFC), Secular Acceleration of the Moon R.H. Stewart, Introduction to Physical Oceanography, Texas A&M University, chapter 17 P. Webb, Introduction to Oceanography, Roger Williams University, chapter 11 J. Bosboom and M.J.F. Stive, Coastal Dynamics, TU Delft Open, section 3.8.2 Amphidromic Systems R. Nave, HyperPhysics (Georgia State University): Tides M. Berry (2015), Chasing the Silver Dragon: the physics of tidal bores, Physics World C. Garrett (1972), Tidal Resonance in the Bay of Fundy and Gulf of Maine, Nature 238 G.D. Egbert and R.D. Ray (2000), Significant dissipation of tidal energy in the deep ocean, Nature 405 Fundy Ocean Research Centre for Energy (FORCE): Tides UK National Tidal and Sea Level Facility: Tidal river bores; H. Chanson, University of Queensland: Tidal bores Digital Atlas of Ancient Life (Paleontological Research Institution) and The Field Museum: J.W. Wells (1963) and fossil coral growth lines Illustrations are AI-generated; narration is synthetic. Diagrams are simplified and not to scale, and the tidal bulges are hugely exaggerated; realistic scenes are illustrations, not photographs of any real place or event. #Tides #TidesExplained #HowTidesWork #SpringTide #NeapTide #KingTide #TidalBore #BayOfFundy #Moon #Oceanography #EarthScience #OceanScience #ScienceExplained #Physics