Global Ocean Tides
Why Physics Stack Exchange recommends it
Physics Stack Exchange answerers and commenters link it to show that real ocean tides are complex sloshing, resonant waves shaped by continents and basins, not simple bulges toward and away from the Moon.
Recommended by 2 people across 2 different months, 2021 to 2025.
What it is
A 2m14s NASA animation of global ocean tides built from Topex/Poseidon and Jason satellite altimeter data. It shows tides as rotating and trapped waves across the world's ocean basins, with tidal heights exaggerated, rather than as two simple bulges.
What people said
Recommends mmesser314 · 2023-07 · Physics Stack Exchange · on “Does the Earth experience air resistance?”
@dan - Tides do slow the Earth's rotation. They are more complex than you would expect, and often explained incorrectly. Here are a few videos. From NASA, what the tides really look like - Global Ocean Tides [this video] . From PBS SpaceTime What Physics Teachers Get Wrong About Tides! [LINK] . From CrashCourse, how they slow the Earth - Tides: Crash Course Astronomy #8 [LINK]
Recommends Solomon Slow · 2024-03 · Physics Stack Exchange · on “How can tides even of miniscule magnitude occur in inland lakes?”
Ocean water is flexible enough to allow water from the side where the moon is not located to flow to the other side where the moon is. That's not how tides work. Ocean tides are complicated standing waves [LINK] that slosh about in the world's major ocean basins. [this video] The oscillation is driven [LINK] by the Earth's rotation and gravitational interaction with the Moon at the incredibly low-frequency of just a bit less than two cycles per day. At such a low frequency, the wavelength of the tidal waves is huge. Ocean basins are large enough to contain waves of that length, and they can resonate with that two-cycle-per-day forcing function. Lakes just aren't big enough. The water in the lake
Cites Solomon Slow · 2021-10 · Physics Stack Exchange · on “How does general relativity explain tides?”
P.S.: Water in the Earth's oceans does not "move toward the moon." It experiences a daily cycle of _very small_ changes in its weight as the Earth rotates in the presence of the gravitational attraction from the Moon and Sun. Those cyclic changes constitute a _forcing function_ [LINK] ) that causes the water in the oceans to slosh around in complex ways [this video] . The complexity is due to the shapes of the various ocean basins and bays around the world.
Cites Solomon Slow · 2023-09 · Physics Stack Exchange · on “Tides in lakes attached to the ocean”
Ocean tides are _standing waves_ that the moon and sun excite in Earth's large ocean basins. Lakes just aren't big enough for standing waves of such long periods, and the river connecting the lake to the ocean is too small to let any of the wave energy through. [this video]
Cites Ohm's Lawman · 2025-03 · Physics Stack Exchange · on “If we put a floating ball at a high tide point on the ocean would it roll to low tide (assuming no friction)?”
There is no "high tide point." There are no two "bulges" like your picture shows. There _would_ be if the Earth had no continents, and if the entire globe were covered in deep water, but the continents get in the way of the tidal wave, and make the true situation _much_ more complicated. [this video]
Critical Solomon Slow · 2024-03 · Physics Stack Exchange · on “How to calculate tidal bulge on a shallow, enclosed body of water?”
The moon does not cause any "tidal bulge." The drawings that you have seen that show Earth's oceans "bulging" toward and away from the moon are a lie. They don't show you the shape of the water. What they show is the shape of the _force_ that acts on the water, but how the water responds to that changing force nover time is much more complicated. [this video]