Which minimal length English sentence describes the set of all primes smaller than 100?
You can use numerals as well.
Which minimal length English sentence describes the set of all primes smaller than 100?
You can use numerals as well.
The one I talked about before, but it is very obscure, even unknown on the whole World Wide Web.
We have two equal stars, A and B. Then we have a planet called X in the orbit around A, and a planet called Y around the star B.
Everything else equal, except for the rotation speed of both planets. Planet X rotates 20% faster than planet Y. The question is, which planet has a higher average surface temperature.
Edit: See discussion:
http://lesswrong.com/r/discussion/lw/p1m/open_thread_may_22_may_28_2017/dsis
Long ago, I invented a problem which solution looks like this:
The problem was to place a complete set of white chess pieces on the chessboard such that the number of bonds between them is maximal. Here you see that the king protects 8 neighboring pieces and the pawn in the top line covers no piece. The number of all protections is 53 and it can’t be done any better. (You may notice a pawn in the first line and those bishops are of the same color, but that’s fine.)
If you now add 40 more queens and rearrange all those 56 pieces, then there will be at most 338 bonds in total. We call that number B – the maximal bonding number for the set F. For all the white pieces it’s 53, for 2 knights only it’s 2, and so on.
We have a set F with bonding number B1. And a proper subset F’ with the bonding number B2. B1 is equal to B2. Which set is that?
In other words, for which set you can remove one or more pieces and the maximal binding number remains the same as it was initially.
There is a trivial solution of any single piece and the empty set, but as always, we want a nontrivial solution.
Some, at least, are worth mentioning. How good they really are is debatable. But I generally like most of those, described below.
Imagine, that you are an intelligent bird with a 360 degrees, panoramic view, flying over a plane equipped with orthogonal x and y axis, clearly visible and – what a coincidence – intersecting just 10 meters beneath you.
I argue, that due to the well-known phenomenon of the geometrical perspective, you see in a distance the line which goes North, parallel to the line which goes West. In fact, every direction seems parallel to all other three directions.
Is that right, and why it’s right? How could this be?