Comment by vintagedave
3 days ago
I agree, I find those deeply counterintuitive too. For other readers, the tidal explanation I have read is yes, the moon’s gravity pulls on the sea to raise a tide on the side facing the moon. The reason there is a tide on the opposite side is that the moon also pulls on the earth’s solid mass (also water, but the solid part it’s important here), creating displacement that causes the water on the other side to rise. There is a difference in the gravitational acceleration across the diameter of the earth and it’s less on the far side, thus the unequal pull, thus displacement. Since they are orbiting, this gravitational pull doesn’t cause the two (earth and moon) to meet, though.
This is an amateur’s explanation and I’d welcome input from someone with more understanding. For tidal friction, I can’t answer at all, I need to research.
See the PBS SpaceTime explanation hyperlinked-to elsethread and then the Physics StackExchange one. Gravity "pulling on" rock and water differently is a misleading explanation, and really an attempt to tweak an explanation that is bad to start with.
Tidal forces are fictitious forces that are what orbital mechanics look like in the accelerated frame of reference of the thing doing the orbiting. They are not a uniform "pull" in a single direction. That will get you to the idealized Waterworld explanation of PBS SpaceTime. What will get you further is the realization that PBS SpaceTime is almost on-point with the "assume a perfectly spherical cow" joke, which is where the Physics StackExchange explanation comes in, with the reality that the water is moving around and over the rock and that it's a lot more complex.
Which then gets you to Tom Scott and part of Cornwall rising and falling twice per day. (-:
* https://youtube.com/watch?v=lCA0II1sVZA
Thankyou. I will read up on this!