zlacker

You may have seen diagrams of the tidal force of the Moon on the earth (like this one: https://www.oc.nps.edu/nom/day1/tide_force_diagram.gif).

Intuitively you would think that the tide is being formed because the Moon is "lifting up" the water at the point closest to the Moon. But this contribution is actually very miniscule to the tidal effect. Instead the bulk of the tides are produced about 45 degrees away where the tidal force is parallel to the Earth's surface. This has the effect of dragging the water closer to the tidal bulge.

>>antogn+(OP)
but to develop better intuition, think of the sun's gravity as a field in space and nothing is being dragged anywhere, it's just that wherever you are feels appropriate to where you are and where you are going is the path of least resistance, and the places around you feel the same way, and where you all are in relation to each other (in this field) changes its relative position to everything else.

the water of an incoming tide doesn't feel "i'm being dragged uphill", it feels "hey, the earth is moving underneath me". it's all in freefall all the time.

you don't feel like you are rotating at 1000 mph (1600 kph) but you do feel your weight against the surface of the earth. same with the water, except it feels itself being squeezed by everything around it like you only feel that in the entrance to a crowded venue.

so, the water on the side toward the moon and the water on the side away from the moon would mostly perceive the earth as dropping away or coming closer (if they could perceive anything at all) where they are is always their point of reference

>>antogn+(OP)
Thank you--the diagram you link is a better explanation of whey the tide "bulges up on the sides of the Earth closest to and farthest from the Moon"--the article left this entirely unclear.

In particular, I could understand how two satellites connected by a cable would result in the cable being stretched. But I still find it hard to wrap my mind around the fact that we get a high tide where the Earth's gravity and the Moon's add (the far side of the Earth from the Moon), but we also get a high tide on the opposite side, where the Moon's gravitational pull is subtracted from the Earth's. The centrifugal force is (I think) a much better explanation. (I realize physicists don't consider that a force, but...)

So yes, tides really are weirder than I think.

(The other facts in the article were actually familiar, e.g. the fact that the tides in Hawaii are quite small, because it's not far from an amphidromic point.)

>>mcswel+ds
Tides aren't caused by centrifugal force but by differing gravity. You would be ripped apart by tides falling straight into black hole.

The near part of Earth experiences more gravity from the Moon, the far part less. The Earth moves in the center so the water bulges on the ends. Important part is that the Earth pulls things out their natural orbits.

With circular orbits, gravity and centrifugal force are balanced so could be considered difference on centrifugal force. But that isn't true for all orbits.

>>ianbur+tx
Simple illustration of what you are explaining in 1D. Imagine a simplified Earth:

Water -- Ground -- Water

Now let's add a Moon with gravitational pull. The pull stretches the system, because gravity is stronger the closer you are to the Moon.

Water ---- Ground ---- Water -//- Moon

The water is farther away from the ground on both sides now, since both sides stretched.

>>empiko+aU
so why is left water further away from ground? this example make 0 sense

>>heaven+Nw1
The Earth is being pulled away from that water, just as the water on the right is being pulled away from the Earth.