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The explanation is phenomenal. I particularly like the elevation heat map, which helps me intuitively grasp what is going on.

This raises a question for me though: why do we show the tidal bulge graphic in any educational context? Like OP, the "far bulge" was always the most surprising and difficult-to-grasp part of the image. But this explanation would indicate that the far bulge is almost totally pointless as a concept, given the complexities of the system. Given it's the least intuitive part of the image, it invites additional consideration. But it's all the wrong consideration!

The model would be more useful if it only showed the bulge on the moon side, and excluded the far side bulge. It would still be wildly imprecise, kind of like the orbital model of atoms is wildly imprecise, but at least it would be a slightly more accurate (and useful) initial mental model.

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Bjartr 10 hours ago | parent | next [-]

I expect because without the far bulge, 12 hour tides can't be explained. One bulge would mean 24 hour tides. Not that either explanation is actually correct, but the two bulge explanation matches the obseved periodicity, which is all most people would ever need or care to know about tides these days.

I can't for the life of me understand why graduate level oceanography courses would be teaching it though.

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pcrh 8 hours ago | parent [-]

If the bulges were caused by water being attracted to the moon, there should not be a "far bulge"?

So how was the existence of a far bulge justified?

	▲	Bjartr 4 hours ago \| parent \| next [-]
		It's not justified for any rigorous setting at all. In a layperson setting, it's as justified as saying the speed of light slows down in non-vacuum. It doesn't, but it's a close enough explanation for most people most of the time, and if you squint it's sort of saying the right thing, but missing all of the details. In the same way as the observed speed of light is slower in air, the tides happen every 12 hours. But c doesn't change and there aren't two bulges. It 100% does not, every single photon is moving at the full c speed of light at all times. It's not even that the photons are bouncing around and so they, on average do not make progress as fast. I believe it's a factor of how the moving EM field of the photon nudges particles like electrons a little, whose now moving field results in a lower net wave phase velocity such that observed propagation time is < c, but every photon still moves at exactly c.
	▲	calfuris 5 hours ago \| parent \| prev [-]
		The Moon's gravity isn't just pulling on the water, it's pulling on the Earth as a whole. It's pulling more on the Earth as a whole than on the water on the far side. In the Earth's frame of reference, that looks like it is pushing the water on the far side away a little bit.

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srean 10 hours ago | parent | prev [-]

It's an idealized model, accurate if Earth had only a single all encompassing deep ocean. Idealized models are good pedagogic tools to build corrections upon.

It's similar to depiction of projectile motions as parabola s. The trajectories of artillery shells ar not like that, but helps get started.

	▲	randallsquared 10 hours ago \| parent [-]
		Well, a single all encompassing deep ocean of something in which waves could travel 1600 km/h, since that's one of the major constraints, too.