In a comment on another question, I saw the movie Interstellar mentioned. And I immediately thought about the scene in which some members of the discovery team had landed on a planet circling the black hole Gargantua. They landed in a thin layer of water on which a huge spiked wave (assumed to be 1200 meters high; see here) appeared. Remember?
I can't imagine this to be true. Of course, there are tidal forces exerted by the black hole. And maybe there are more waves due to multipole tidal forces. Let's assume that the planet is not yet tidally locked to Gargantua. Can these waves actually exist? Can gravity be "concentrated" in such a small region? Or: Was Kip Thorne right in asserting that this wave(s?) can actually exist? Is general relativity essential for understanding this effect, if it indeed exists?
Of course, the huge waves could be used cinematically to give a feel for tidal effects, but then why Kip Thorne writes these spiked waves can actually exist. Or was he referring only to the height of the waves, and not to their spiky Nature?
In the picture, a small water wave is depicted. I think this wave is a tsunami on earth. So these huge waves are possible. They even can grow to 500 meters high! See the comment below by @Azur. Or see here. Of course. When a big meteorite hits the earth, huge waves will be produced. But these are easy to understand. What is difficult to understand is that spiky waves emerge due to a tidal effect.
