Genady

No, I did not, Yes, I admitted that I don't know the answer. I didn't know it because I didn't think about it in detail. After that, @Markus Hanke and @swansont have answered more specifically.

What do you want to know about the curvature? See Curvature - Wikipedia

The first stop: I think these limits are wrong.

I can't say because: 1) according to my calculations, the solution of the equation is about x=87 degrees 2) it is an angle rather than curvature But first you should check the assumptions leading to this equation.

Hmmmmm... Not sure how that happened. 🤔 Maybe I should blame it on @Genady. He explained how to quote text selections, and I probably quoted the quotation in your post. 😶 Hmmmm... I quoted a quotation several times and it worked fine. Just like this one above, nested in each other. But you need to select the quotation completely. Perhaps if you select it partially it gets messed up.

I am listening to myself playing Aka Tombo on glockenspiel.

An overview here is very interesting (but doesn't include the encounter described in OP): North Sentinel Island: a timeline of the world’s most isolated tribe | Atlas & Boots (atlasandboots.com) PS. Perhaps a good model for humanity if we are ever visited by aliens.

Susskind said in one of his lectures something like, "Who knows what Heisenberg was smoking when he came up with the matrix mechanics."

Correct. (which was the Einstein's interpretation)

His interpretation was hidden variables. Bell came up with the test, after Einstein's death. The test refuted Einstein's interpretation.

Sure. Einstein.

Isn't it the Copenhagen interpretation? Then it's Copenhagen (for me). The non-Copenhagen interpretations seem to try to adjust QM to our classical intuition. It seems to me easier to adjust the intuition to QM.

Then it's Copenhagen (for me). Honestly, I don't understand this reference. Could you explain?

Yep. And proud of it

I don't know. I don't have one.

With so many, how does one pick a favorite?

So, you mean in your OP, "we can intuitively distinguish intuitively wrong from intuitively right definitions"? Also, if they follow from axioms, then they are theorems rather than definitions.

How are they proven without definitions?

If we assume that the "optimum" means maximum amount of light on the wall, and if we stick with the sketched configuration, then I believe my equation above is the answer.

How? Your examples didn't make it clear to me.

Right. OTOH, if it were like in the picture - just as a fantasy - all that would be needed is a flat sheet of aluminum foil curved into a cylinder. Of course, a flat surface like in your earlier post would do, too.

Yes, there really are.

I think it scared them.

No, I mean I don't believe it's a practical problem. Regardless, I gave you the equation above that solves the problem. Is it unsatisfactory? Where in the world the sunlight comes vertically like in the picture? How often does it happen and how long does it last?

I don't believe it.