Wikipedia:Reference desk/Archives/Science/2016 September 7

= September 7 =

Life expectancy and dead parents
How good of a predictor of your own life expectancy is the age of death of your biological parents, and specifically the parent of the same gender, when those deaths are from natural causes ? StuRat (talk) 00:51, 7 September 2016 (UTC)


 * It's not a great predictor, but there is a correlation. For instance, if your parents died in their 40s of natural causes, you will likely die by your early 60s. But if at least one parent makes it past 80, you'll probably reach your 70s . If you really look at the numbers in their data, you see the trend, but yeah, really horrible predictor. Even twin studies don't show excellent correlation . Someguy1221 (talk) 01:31, 7 September 2016 (UTC)


 * All my relatives on my mother's side save two cousins are dead, from 50-70. All my relatives on my Fathers side are alive or at least reached almost 90, if not their early hundreds.  Since their lifestyles were very similar, anecdotally, I assume it was genetics.


 * The outliers were my sister at 20 (one of thos athletes who drops dead), my father's niece who died the same way as my sister at 24, and my mother's nephew who died at 50 from side effects of a pituitary condition, (They had to induce puberty with hormones at age 18.)


 * On my father's side, he is the youngest of his brothers and their wives, himself at almost 80. Many of his female relatives lived into their 90's if not later. See Howard Foundation. μηδείς (talk) 18:36, 7 September 2016 (UTC)


 * Harry Caray lived a lot longer than his son Skip Caray did. ←Baseball Bugs What's up, Doc? carrots→ 20:39, 7 September 2016 (UTC)


 * See also The Link between Parental and Offspring Longevity (2011) which says: "There is strong evidence that individuals with longer lived parents exhibit lower mortality risk. Furthermore, we find that behavior variables explain between 30 and 40 percent of the total effect of parental age on offspring longevity. Even after controlling for health and behavioral variables of the offspring, parental age of death has a substantial impact on the survival of the adult offspring".  Alansplodge (talk) 18:13, 8 September 2016 (UTC)


 * I should also have mentioned Winston Churchill who died at 90, even though he expected to die at an age like 50, closer to that of his father's. I suspect Winston's refusal to take visitors while clothed may have been revenent. μηδείς (talk) 03:08, 9 September 2016 (UTC)

What species of spider?


Can anyone identify this species of spider? It is in coastal Georgia, US. It is nocturnal. Bubba73 You talkin' to me? 03:00, 7 September 2016 (UTC)


 * My guess is that it's some kind of wolf spider based on the size, shape, and web style. There are several species of wolf spider endemic to the Southeastern U.S. and they typically build large webs at night over open spaces; often hanging from a tree branch.  It is not uncommon to blunder into one hanging at about head-height with a large web blocking your path under a tree.  It also looks superficially like a Araneus cavaticus, a type of orb-weaver spider or "writing spider", but those have distinctive markings on the web you don't see on yours.   -- Jayron 32 13:58, 7 September 2016 (UTC)
 * I don't know what it is, but I'm pretty sure it's not a wolf spider, at least not in the sense of family Lycosidae, though you may call other things wolf spiders. Lycodsidae are hunting spiders, like the tarantula, salticids, or lynx spiders. According to our article, they "are opportunistic hunters pouncing upon prey as they find it or even chasing it over short distances. Some will wait for passing prey in or near the mouth of a burrow." Here is a guide to identifying wolf spiders. I don't think any of the key features match up.  "Except for those in the genus Sosippus, wolf spiders do not spin webs"  (and I'm fairly sure this is not a funnel-type web that Sosippus weave).
 * Some sort of orb weaver was my guess. Reddit's "what's this bug?" is usually better than we are at getting arthropods down to genus/species ID. Unlike here, they have many regular readers with specific entomological/arachnological training. SemanticMantis (talk) 16:38, 7 September 2016 (UTC)


 * Yes, definitely an orb weaver, and not a wolf. Unfortunately I am temporarily using a 16 y/o Mac, so my browsing capability is too poor to be of use other than at level.  Gotta love'm spiders. μηδείς (talk) 18:22, 7 September 2016 (UTC)


 * Neoscona crucifera is a possibility, particularly considering the cruciform marking on the abdomen. Deor (talk) 19:02, 7 September 2016 (UTC)


 * It looks a lot like that. I have a better photo of it with an ntoumbed insect that I want to upload, but it will be good to know the species.  Bubba73 You talkin' to me? 22:43, 7 September 2016 (UTC)

I've added two better photos. Do they help? Bubba73 You talkin' to me? 02:10, 8 September 2016 (UTC)
 * It does look like the N. crucifera mentioned above. Here  are more pics and an ID guide. For future reference, a clear look at the eyes is pretty helpful for getting spiders in the right family. SemanticMantis (talk) 13:38, 8 September 2016 (UTC)


 * I can probably get a good face-on photo in a day or two. Bubba73 You talkin' to me? 17:37, 8 September 2016 (UTC)
 * Is File:Spider with entombed insect.jpg (which you just uploaded) the same guy? &#x2013; b_jonas 22:44, 10 September 2016 (UTC)


 * Yes, it is the same one, a day later. And I got my new macro lens today, but the web is gone. Bubba73 You talkin' to me? 23:54, 10 September 2016 (UTC)

Name of U1.11 (large quasar group)
Why is U1.11 called U1.11? The article says "It is at redshift 1.11, hence its name" - but I don't understand what that means. As far as I could find out, it has a redshift of about z=1.2?

It seems a shame that the article on one of the biggest things in the entire universe is so poorly written; maybe someone can help make it more clear? — Preceding unsigned comment added by 86.20.193.222 (talk) 03:03, 7 September 2016 (UTC)


 * As the Universe expands, light is redshifted because of the Doppler effect. Redshift means that the light is shifted towards the red end of the spectrum.  By Hubble's Law the amount of redshift is proportional to the distance to the object.  Bubba73 You talkin' to me? 05:06, 7 September 2016 (UTC)


 * As near as I can understand it, when discovered the members of this extended object (a 'cluster' of quasars) were initially measured to have an average distance of Z=1.11. Later, more members of it were observed, altering the average z to 1.28, but this does not alter the original assigned name.
 * Objects discovered by a given survey or study are often named by a letter or letters relating to that survey plus a set of co-ordinates (or a distance, as in this case where that is the more significant factor, and such objects are so few that another with the same measurement is unlikely to be found). Sometimes the same object appears in more than one survey and winds up with more than one catalogue name: see Large quasar group. From one of the linked scientific papers, "the ‘U’ refers to a connected unit of quasars". {The poster formerly known as 87.81.230.195} 90.202.211.191 (talk) 16:58, 7 September 2016 (UTC)
 * Not that multiple names is unusual of course. To OP it's completely expected for intergalactic/interstellar objects to have more than one catalog name unless they're very obscure (as some quasars are). For example the Whirlpool Galaxy, the c. 14th brightest galaxy as seen from Earth, is M51, M51A, NGC 5194, UGC 8493, IRAS 13277+4727, 4C 47.36A, 6C 132748+472801, 7C 132753.10+473032.00, 2MASX J13295269+4711429, BD+47 2063, KPG 379a, GB1 1327+475, GB6 B1327+4727, 87GB 132747.8+472723, Z 246-8, 1RXS J132953.8+471143, APG 85, ISOSS J13299+4714, TC 827, KHG 1-C 5, B3 1327+474C, UZC J132952.1+471144, LEDA 47404, VV 403, BWE 1327+4727, MCG+08-25-012, WB 1327+4727, WN B1327.8+4727, 2XMM J132952.5+471144, XMMU J132952.9+471140, PSCz Q13277+4727, IRAS F13277+4727, RX J1329.8+4711, PLX 3084 etc. Sagittarian Milky Way (talk) 21:02, 7 September 2016 (UTC)

OK, thanks - I guess that makes sense, that the readings were altered later. I'm just a bit surprised, because it's not like 1.11 is anywhere remotely close to 1.28, I mean... it's about 15% out, which seems like a huge difference. (I'm not quite clear about how z relates to distance/time, but I think it's a few million light-years) 86.20.193.222 (talk) 01:39, 8 September 2016 (UTC)
 * These Large quasar groups are very large, and because of their distance quite hard to see and measure. It doesn't seem surprising to me that the researchers first managed to define part (what they thought was all) of this group and calculated a z of 1.11, and then later managed to identify more distant members that shifted the overall average z by a sizeable percentage: it could even turn out that what were thought to be two separate LQGs are actually parts of one even larger one. Also, this is ongoing research which only a relative handful of the world's astronomers are working on (and likely not full time, but in parallel with other studies), so refinements, revisions and updates concerning LQGs are likely to occur over years rather than months. {The poster formerly known as 87.81.230.195} 90.202.211.191 (talk) 18:36, 8 September 2016 (UTC)

Numbers 80 to 85 in Ancient Calendrical Computations
Have any of the numbers from 80 to 85 ever been employed by ancient populations in their various calendrical computations ? Would it help if I were to tell you that this number was divided into four almost-equal parts of roughly twenty elements each ? (This is a follow-up to my previous question). — 79.113.197.62 (talk) 20:35, 7 September 2016 (UTC)


 * There are ancient 84 year Easter cycles. Ancient enough that Christianity was still illegal. No idea if that had 4 almost equal subcycles (though this seems to made of 4 19 year moon cycles plus 1 less accurate 8 year moon cycle, 84 was surely chosen because the calendar and days of the week repeat every 28 years FOREVER!!!!!!!  (until the Gregorian calendar 's invented because doing that for 23,000 years makes Christmas in summer) Sagittarian Milky Way (talk) 21:25, 7 September 2016 (UTC)
 * Unfortunately, the pre-Christian Indo-European civilization I am investigating had six day weeks, five per month. Nevertheless, it is not completely out of the question that they probably borrowed such a lunar cycle from neighboring cultures, which had a seven day week. — 79.113.197.62 (talk) 22:42, 7 September 2016 (UTC)
 * Where were the 5 or 6 extra days in a year put? Sagittarian Milky Way (talk) 23:31, 7 September 2016 (UTC)
 * Apparently, they weren't. At least not in an usual year. The presence of intercalary months is not excluded, though. — 79.113.197.62 (talk) 23:37, 7 September 2016 (UTC)
 * Remnants of that 84 - year cycle lingered on until the nineteenth century.  It was used in parts of Britain and Ireland until the tenth century.   The mnemonic for finding the displacement of the start of the lunar month relevant to the Julian calendar month became a nursery rhyme which was chanted by Irish children. 80.44.92.185 (talk) 10:47, 9 September 2016 (UTC)
 * For what purpose did "the Pre - Christian Indo - European civilisation" divide 80 - 85 into "four almost-equal parts of roughly twenty elements each"?  The epact (difference between the lunar and solar years) normally increments by eleven days annually in the Gregorian calendar.   After 6,840 years it has increased by 75,570 (complete 30s are always cast out).   Had it increased by eleven every year the total increment would have been 75,240 days.   The difference (330 days) is accounted for by the saltus lunae (one - day jump) and secular adjustments.   On average, therefore, the adjustment comes every 6840/330 years, or once every 20.73 years. 80.44.94.57 (talk) 12:24, 9 September 2016 (UTC)
 * You seem to imply that the difference between the solar and lunar years is $$11+\frac{330}{6840}=11+\frac{11}{228}$$ days. Since the length of a lunation is 29.530589 days, this would yield a year length of more than $$12\cdot29.530589+11+\frac{11}{228}=365.{\color{red}4^+},$$ which is way too large. — 79.113.253.61 (talk) 16:25, 9 September 2016 (UTC)