Wikipedia:Reference desk/Archives/Science/2014 January 9

= January 9 =

Water
What is the weight of (i) fresh water and, (ii) sea water - per cubic meter at say, 20 degrees c? Then, how many more times denser are these when compared with air? 202.53.237.198 (talk) 09:38, 9 January 2014 (UTC)
 * See the pages Properties of water, Seawater and Density of air. Answer: fresh water 998 kg/m3, sea water 1020-1029 kg/m3 and air 1.20 kg/m3, so water is roughly between 830 and 860 times heavier than air. - Lindert (talk) 10:08, 9 January 2014 (UTC)
 * Obviously those numbers are a little inexact because the density of air depends on temperature and pressure and also on humidity - so it varies quite a bit from place to place, from day to day and depending on the altitude that you measure it at.  Sea water also varies in salinity (saltiness) depending on where you are and the depth at which you sample it - so the density can be quite variable...for example, there is a lot less salt in regions of the ocean when you're closer to the outlet of a large freshwater river or the outflow of a melting glacier.  The density of water also changes quite a bit with temperature. SteveBaker (talk) 13:28, 9 January 2014 (UTC)

video of experiment in chemistry
Hi,

I'm looking for a tube or video of experiment in chemistry that can be preformed in high schools.

Does anyone have any idea?

Thank you. — Preceding unsigned comment added by 87.68.151.162 (talk) 17:20, 9 January 2014 (UTC)
 * Have you tried going to youtube.com and searching for "high school chemistry experiments"? Rojomoke (talk) 20:02, 9 January 2014 (UTC)
 * A search for "experiment in chemistry" turned up http://www.youtube.com/user/koen2all who has a bunch. Richard-of-Earth (talk) 20:50, 9 January 2014 (UTC)
 * Clock reactions are always nice to see. Exploding nitrogen triiodide is spectacular, and doesn't require any chemistry skills, just dump iodine in household ammonia, wait, filter, and dry. Silvering, elephant toothpaste, ... Youtube has lots of examples of all these. And with a list of suggestions next to every video, you should have plenty to choose from.   Ssscienccce  (talk) 06:19, 10 January 2014 (UTC)


 * I have to strongly warn you about "science" videos on YouTube - there is a massive culture there of people who fake these kinds of videos to produce "amazing effects you can do in your kitchen" types of thing - and a horrifyingly vast percentage of them are complete nonsense.  We get people coming here asking us to explain them (or bust them) all the time - and quite often now we just take one look at the fact that it came from YouTube and not even bother to try to figure it out because we know that it's overwhelmingly likely to be bullshit.


 * My instinct with YouTube science videos is to assume that they are faked until it's proven that they aren't.  Honestly, I'd be looking for old videos from "Bill Nye the Science Guy" or something.
 * SteveBaker (talk) 14:32, 10 January 2014 (UTC)
 * Better yet, all I know about science I learned by watching Look Around You videos. ~:71.20.250.51 (talk) 03:19, 11 January 2014 (UTC)


 * As long as you know what the experiment is that you want to do, and how it is supposed to work, YouTube is still a great resource. For example, there are lots of high school paper chromatography experiments on there.  You can look at pigments in leaves, or - here's a fun one - see if you can prove which kind of pen was used to draw a line by running the unknown black line against a few different types of known black pens.  (I don't know if they have that, nor am I even 100% sure of the outcome (depends on the inks involved) but they have paper chromatography of pens at least) Wnt (talk) 19:56, 11 January 2014 (UTC)


 * A great way to make those kinds of experiments more fun for kids is to give them a reason WHY they'd want to know that. Dream up some kind of a mystery thriller that they have to solve in a CSI-miami style - maybe someone in school stole the classroom's pet gerbil and wrote a ransom note - there are three suspects and now you have to test all of their black pens to see if any of them match the ink on the note...something like that.  (Hint: The teacher did it and the gerbil was in the store-cupboard all along!)  Invisible inks are also fun things for that kind of thing (milk and lemon juice make great invisible inks).  Maybe you could even make a multi-stage "who dunnit" using a variety of scientific techniques to lead the class to the answer - breaking a simple code using letter frequencies, that kind of thing.  Teaching math and science without the kids knowing WHY you'd ever need to know it is much harder than making it so they want to learn. SteveBaker (talk) 15:27, 12 January 2014 (UTC)

help finding articles mentioned on wiki page
This Wikipedia page mentions some articles that my boss would like to read.

Supraorbital ridge

The articles are not in the reference list at the end of the page. They are not in the external links or further reading sections either.

Any idea how I would find the titles or journals, if not the actual articles, that are mentioned on the page?

130.132.173.15 (talk) 20:48, 9 January 2014 (UTC)


 * Footnote-referencing gets complicated on the ref-desks. Often clearer to just link to the WP article directly: Supraorbital ridge. DMacks (talk) 21:37, 9 January 2014 (UTC) I made that change. Looie496 (talk) 16:57, 10 January 2014 (UTC)
 * I added a note on Talk:Supraorbital ridge asking for help. Each article has a talkpage to help discuss/coordinate edits, so maybe someone who watches that article will be able to provide the missing information. Or if someone here has it, please add it there. DMacks (talk) 21:43, 9 January 2014 (UTC)
 * The article is in part based on an old (public domain) edition of Gray's Anatomy, so that is probably where those references are cited. The most recent PD version (from 1918) is online here Rojomoke (talk) 21:44, 9 January 2014 (UTC)


 * In the Further reading section, there are DOI links to online copies of the journal articles. Usually, you can view the summary but need to pay to read the entire article. ~E:71.20.250.51 (talk) 22:02, 9 January 2014 (UTC)


 * When you see weird shrapnel on Wikipedia articles, always click the History tab. Click "500" so you have some room to work in, and hunt around until where the shrapnel turns up, and by trial and error you can hit the revision (There's also a tool WP:Wikiblame but I forget where the link is)  Anyway I quickly came up with  which says it is text taken from another article (for Endo and a few others - let me know if that isn't all of them) and also has a citation list. Wnt (talk) 22:11, 9 January 2014 (UTC)
 * That would be WP:WikiBlame (cap 'B') 71.20.250.51 (talk) 22:32, 9 January 2014 (UTC)


 * I got to work on the last section and found many of the references; my feeling is that the ones missing are probably better replaced with some later references that come up on search. It looks like Google Scholar is a good search for this topic - just go to scholar.google.com and put in "supraorbital", one of the author names mentioned, and optionally a year, and you'll come up with plenty, including less dated references.  I'm afraid I'd have to get more interested in the science to finish the job, though... maybe someone else could lend a hand with this fascinating task? :) Wnt (talk) 23:03, 9 January 2014 (UTC)

Science of romantic relationships between ethnic groups
Is there any scientific evidence to suggest whether there is either a genetic based or environmental based preference for romantic relationships? Traditionally, people fell in love with their race but as different ethnic groups became integrated into multicultural societies, it seems that there are more inter-racial relationships than ever before. However, is there still a tendency to find the same race more attractive due to generics? Clover345 (talk) 22:13, 9 January 2014 (UTC)


 * Yes, there was a study in the 70's that showed sexual selection can be based on novelty. This encourages outbreeding, which leads to hybrid vigor.  A quick search at google for novelty "sexual selection" brought up the very study in guppies I had remembered from the 70's. μηδείς (talk) 23:05, 9 January 2014 (UTC)


 * See also Claus Wedekind. There is significant evidence women prefer men whose sweat indicates they are as genetically unrelated in regard to their immune-system genes as possible. μηδείς (talk) 23:09, 9 January 2014 (UTC)
 * That would be MHC, see specifically Major_Histocompatibility_Complex_and_Sexual_Selection. As far as I know, MHC types can be the same between rather distantly related people, as well as different between rather closely related people. SemanticMantis (talk) 23:16, 9 January 2014 (UTC)
 * The first part of your question your comment about "traditionally" is simple: more racial integration will increase the chances of interracial relationship. After all, you couldn't very well have married a Chinese person as a white person if there weren't any Chinese people around to marry (such as is the case for me). Mingmingla (talk) 03:31, 10 January 2014 (UTC)
 * Also, cultural taboos against interracial relationships prevented people from mingling with those from other races until quite recently. Enforced racial segregation was still commonplace in the USA until the 1970's - and even after it was abolished, the taboo lingered on and only slowly diminished - it still hasn't completely vanished even today.   The taboo doesn't come from the people falling in love with people from other races - it comes from those around them who didn't happen to feel that attraction.  So even though we may be wired to seek genetic diversity - that instinct is easily suppressed by the greater instinct to not have the crap beaten out of you by KKK members! SteveBaker (talk) 14:27, 10 January 2014 (UTC)
 * What makes you think that "we" (i.e. the majority of people) are "wired to seek genetic diversity"? As a matter of fact, many studies indicate that for most people, the opposite is the case -- they instinctively find people most like themselves to be more attractive (although of course there's a significant minority who prefer people of other races).  Which makes perfect sense in the context of human evolution: during the prehistoric period (which encompasses most of the time when humans existed as a species, and which was when almost all of human evolution took place), and even as late as the early Bronze Age, the various tribes were isolated from one another and their only contact was through warfare -- which created a strong selection pressure for the instinctive preference for genetic similarity, because people who were attracted to those within the tribe and hostile to outsiders were more likely to defend themselves against invaders and survive, whereas those who were attracted to outsiders were the ones who would get killed, enslaved, raped, etc. 2601:9:3200:467:6109:95AD:B0F7:600D (talk) 01:41, 11 January 2014 (UTC)
 * Actually, I don't believe we're wired to seek diversity - or at least that we're wired to seek a certain amount of diversity (so we're not attracted to siblings) but otherwise prefer similarity. (I said "even though we may be wired...").  I've seen many studies to the effect that we seek people who are likely to have large numbers of identical genes to ours in order to increase the chances of those genes being passed on to offspring.  This is called homophily - and we have an article about that. This story references several papers that say that we seek out friends who are genetically similar - and that on average our friends share the same amount of genetic similarity as fourth cousins.
 * Furthermore - even if we were wired for diversity, the genes of someone from a different race aren't significiantly more diverse than people from our own race (check out our article: Race and genetics) - so this argument kinda falls to the ground for that reason too. SteveBaker (talk) 02:22, 11 January 2014 (UTC)


 * Can you provide any references, IP 2601? I know from experience as a person of nordic/slavic descent, I have largely been attracted to males and, especially, females of hispanic descent.  Is there evidence in favor of or against this? μηδείς (talk) 02:11, 11 January 2014 (UTC)


 * I actually can't provide the reference because it's been a long time since I've seen it cited, and I forgot the name of the study. I could look it up, but it will take a while.  Anyway, nobody denies that there is a significant minority of people who are attracted to those of other races (if there wasn't, then there'd be no interracial marriages at all) -- so your experience is perfectly reasonable, even though it doesn't fit with the "majority" experience.  67.169.83.209 (talk) 02:57, 13 January 2014 (UTC)


 * (Wild hypothesis): I am suspicious that people may have a narrowly defined "target recogition" that is retrained and expanded only in the presence of pheromone, and that this accounts for racial barriers to feelings of attraction. But I haven't seen any research at all to back that up. Wnt (talk) 14:42, 11 January 2014 (UTC)


 * My own hypothesis is that this has to do more with the "hard-wired" aspects of human psychology (and in particular with novelty-seeking behavior) than anything else. (In fact, the study I mentioned earlier -- whose title I forgot -- had also concluded that novelty-seeking had a strong positive correlation with interracial attraction.) 67.169.83.209 (talk) 02:57, 13 January 2014 (UTC)