<p>There must be an optimal length of a question, assuming there is a smooth relation between the length of the question and the likelihood of the answer. Clearly, questions of zero length cannot receive valid answers, as there is not enough information to formulate a response. Likewise, infinitely long questions cannot receive an answer, either, because one's lifetime span would run out while reading the question, and one won't be able to apprehend all of the information contained in the question. Let us now apply Rolle's theorem: there must exist a point where the derivative of the likelihood of the answer is zero. The derivative is not identically zero on the positive semi-line, however, since we observe some questions that do get answered, so the probability is strictly positive for some nonzero lengths. By smoothness assumption, one of the critical points with the derivative = 0 must correspond to a global maximum of the probability of receiving a response wrt to a question of a certain length. QED.</p>

<p>(This is an old joke, initially formulated by a physicist Paul Dirac with regards to an optimal distance to admire a female face: from zero distance, you see something like a wall of flesh, and cannot really see anything; at infinity, that's just a small dot, and you can't see anything either, so there must exist an optimal distance. See <a href="http://www.dirac.ch/PaulDirac.html" rel="nofollow">http://www.dirac.ch/PaulDirac.html</a>)</p>
