Wikipedia:Reference desk/Archives/Science/2018 February 20

= February 20 =

Gone today hair tomorrow
I used to have no hair on top of my head. Over the last few months it has started growing again. What could be the reason?80.2.21.79 (talk) 00:07, 20 February 2018 (UTC)
 * We don't do medical advice, which makes it rather difficult to get into the most probable causes relating to diet and medication (or maybe even your life partner's medication). We also don't know what life stage you're in.
 * As such, the only plausible answer we can give is faeries. Be sure to leave eggs under your bed for at least a month to thank them.  Ian.thomson (talk) 01:01, 20 February 2018 (UTC)
 * Especially the hairy fairies. ←Baseball Bugs What's up, Doc? carrots→ 04:59, 20 February 2018 (UTC)


 * It might be useful to sanitize and resubmit the question: ask whether your specific kind of hair loss (I mean, its medical name, if you know it) can be transient or is prone to spontaneous remission, but only as a matter of general knowledge.  AFAIK hair loss is alopecia by definition rather than diagnosis, but I could be wrong; there are several types described in that article.  Meanwhile, your title happened to match the first review I found searching for alopecia remission, though it doesn't address your specific question much, so here's the link. Wnt (talk) 12:33, 20 February 2018 (UTC)


 * Was that male pattern baldness, or a different type of alopecia? Hormones can affect hair loss in MPB andless sun exposure can change how we see the hair (thinner are almost invisible. --Hofhof (talk) 01:51, 21 February 2018 (UTC)


 * I knew of a case where a child had a cat which would snuggle up next to her when she was sleeping and pull out hairs from one spot on her head, resulting in a little bald spot. It was not painful enough to wake her up. The giveaway was the blond hairballs. Hair fashions which involve pulling the hair tightly into dreads, braids, a manbun or hair clip can cause some hair to be pulled out. See Traction alopecia. Some people develop a "nervous habit" of winding some hair around a finger and holding on to it. So, temporary localized baldness could have a mechanical cause.Not implying that you have dreads or a cat. Edison (talk) 16:04, 21 February 2018 (UTC)


 * This user's other contribs have had to do with Mary and Virgin Births. Perhaps the Holy Spirit came upon him in the night? μηδείς (talk) 16:38, 21 February 2018 (UTC)


 * Are you kidding me??? This is not the place to persecute an IP address for its religious beliefs.  We're here to answer good questions, not do creepy cyberbullying. Wnt (talk) 12:36, 22 February 2018 (UTC)


 * Good point Wnt. That user is a repeat offender, frequently harassing questioners, against established policy-- WP:BITE. Sorry OP. SemanticMantis (talk) 19:33, 22 February 2018 (UTC)


 * Pointing out that the good faith of an IP user who wants to talk about miraculous conception (which he seems to doubt) and miraculous hair regrowth is dubious is in no way "persecuting someone for his religious faith". That's laughable, and it's not my fault if you want to feed the trolling. μηδείς (talk) 20:46, 22 February 2018 (UTC)

Asking for an operator
Is there any operator whose commutator with the square root of Hamiltonian is a constant? i.e. $$ [ \sqrt{H}, \alpha] = constant $$ or $$ [ \sqrt{-H}, \alpha] = constant $$ depending on Hamiltonian is either positive or negative.Sayan Ghosh 04:13, 20 February 2018 (UTC) — Preceding unsigned comment added by Sayan19ghosh99 (talk • contribs)
 * This question should have been asked on the Math Desk. Edison (talk) 15:15, 20 February 2018 (UTC)
 * Moving. μηδείς (talk) 15:44, 20 February 2018 (UTC)