Wikipedia:Reference desk/Archives/Science/2015 December 9

= December 9 =

Eroded teeth
Do teeth which have been eroded by plaque grow back if maintained well and by taking calcium supplements ? — Preceding unsigned comment added by 175.101.24.136 (talk) 08:36, 9 December 2015 (UTC)
 * No. This is not medical advice, merely a statement of the bleeding obvious. Greglocock (talk) 10:33, 9 December 2015 (UTC)


 * Not now, but maybe someday soon. -- Jayron 32 16:07, 9 December 2015 (UTC)


 * Read tooth enamel. Enamel is non-living, so it can't rebuild itself. However, limited demineralization of enamel can be reversed if the local pH stays high enough; fluoride accelerates this, which is why it's in toothpaste and other dental care items. Dental caries is suggested reading as well. --71.119.131.184 (talk) 22:30, 9 December 2015 (UTC)

TianQin planned gravitational wave detector
In a recent blog entry V. T. Toth writes that he is in Guangzhou "on account of a conference about a planned space-borne gravitational wave detector called TianQin." This statement is probably accurate because Toth is a physicist who does astrophysics. Do we have an article about this particular gravitational wave detector? Is it the same as any of the ones mentioned in Gravitational-wave observatory ? &#x2013; b_jonas 11:51, 9 December 2015 (UTC)
 * I don't think we have an article. There is not much written on it yet. see http://arxiv.org/abs/1512.02076 and http://arxiv.org/abs/1510.04754. Graeme Bartlett (talk) 12:25, 9 December 2015 (UTC)
 * Even on Chinese Wikipedia 天琴 is a redirect to the article for the constellation Lyra. Graeme Bartlett (talk) 12:29, 9 December 2015 (UTC)
 * Thank you for the answer and the links. &#x2013; b_jonas 17:02, 9 December 2015 (UTC)
 * Cool, Graeme! How did you find out the correct characters? For all I know, it could have been 天禽 or even 甜芹. ;-) &mdash; Sebastian 19:35, 9 December 2015 (UTC)
 * The footnote says "In Chinese, TianQin means a musical instrument, namely a zither, in space. The TianQin experiment is metaphorically seen as a zither that is being played by the Nature itself through gravitational waves". It can't be that hard to work out the correct characters, even if you don't understand Mandarin. Nil Einne (talk) 20:04, 9 December 2015 (UTC)
 * How I knew the characters, is that the http://www.seminar.net.cn/ link has Chinese and equivalent English text on it. Google translate confirms those two characters have that sound. Also 天 is a clue, meaning sky / heaven. Graeme Bartlett (talk) 20:54, 9 December 2015 (UTC)
 * Thanks, guys. Of course, if I had seen the footnote, I would have reached that same conclusion. My question wasn't meant to express doubt, as the two characters make complete sense and their Pinyin transcription matches. Rather, I just wanted learn from Graeme. &mdash; Sebastian 23:46, 10 December 2015 (UTC)
 * I've created a stub article at TianQin. Feel free to improve.  &#x2013; b_jonas 14:02, 14 December 2015 (UTC)

During prehistoric times, what was the likelihood of growing up to maturity and reproducing for humans?
During prehistoric times, what was the likelihood of growing up to maturity and reproducing for humans? How often did females become pregnant during their lifetimes? How high was the infant mortality? How many individuals of a typical population would survive into adulthood and reproduce? 66.213.29.17 (talk) 19:09, 9 December 2015 (UTC)
 * It's difficult to give a meaningful answer to your questions because nobody was sufficiently developed enough to collect, collate and publish statistics at the time. We can only guess. --TammyMoet (talk) 21:28, 9 December 2015 (UTC)
 * We have an article om Life expectancy which gives our current best estimates over history back to paleolithic times. Vespine (talk) 21:44, 9 December 2015 (UTC)
 * It's true we don't have statistics from prehistory, but that doesn't mean we're just making wild guesses. We can make informed estimates from archaeological evidence. --71.119.131.184 (talk) 22:33, 9 December 2015 (UTC)
 * Do you know what the word prehistoric means? Let me give you a hint. Before any numeric or linguistic recordings were made. 175.45.116.66 (talk) 02:47, 10 December 2015 (UTC)
 * That's rather harsh, 175. I don't know with what accuracy the answer to this question is known, but it is precisely the sort of thing that physical anthropologists try to figure out. -- ToE 04:06, 10 December 2015 (UTC)
 * Just starting with the stats of those humans who still live in prehistoric times, it's possible to start guessing some ballpark numbers. We are not completely at dark here. --Denidi (talk) 18:48, 10 December 2015 (UTC)
 * Bit off topic, but a lot of our knowledge and what we call "established science" is based on indirect evidence. It's nothing unusual. From the chemical composition of the sun to the speed of light in a vacuum, science doesn't really work with "certainties" much (if at all once you get deep enough) All we ever really do is "only guess", but it hasn't stopped science from being the most successful method of obtaining knowledge which is, at the very least useful, even if we don't accept it's "True" for certain. Vespine (talk) 00:01, 11 December 2015 (UTC)