Wikipedia:Reference desk/Archives/Science/2012 February 26

= February 26 =

Molality calculation
A mass of 168 g of manganese dibromide is dissolved in 225 g of water. What is the molality of the solution — Preceding unsigned comment added by Nanceninja (talk • contribs) 02:28, 26 February 2012 (UTC)


 * Please see Molality and Molar mass. If you still have trouble with this homework problem, show us your work so far, and point out where you are stuck. -- ToE 02:45, 26 February 2012 (UTC) (I also shortened the title of this section.)


 * ..., and is manganese dibromide a synonym for Manganese(II) bromide, MnBr2? -- ToE 02:49, 26 February 2012 (UTC)


 * ... apparently so (NIST MML). I went ahead and created the redirect: manganese dibromide. If a chem-head tells me it's wrong, I'll speedy WP:G7 it. -- ToE 05:26, 26 February 2012 (UTC)

Lightning in Hawai'i
A friend of mine who lives in Hawai'i says that he rarely sees lightning there. Is there data to support this and if it's true that there is little lightning there, what's the cause? Dismas |(talk) 07:56, 26 February 2012 (UTC)


 * There are very few lightning storms over the ocean and Pacific islands in general. Quoting from NASA, The ocean surface doesn't warm up as much as land does during the day because of water's higher heat capacity. Heating of low-lying air is crucial for storm formation, so the oceans don't experience as many thunderstorms. The Hawaiian islands are presumably small enough that the weather there is more ocean-like than land-like. Someguy1221 (talk) 10:12, 26 February 2012 (UTC)
 * The areas of the world that see the most lightning (I'm going to use Florida, USA, which is the state with the most annual lightning strikes, as an example) experience it so often because they are prone in their respective warm seasons to produce localized "garden variety"-type storm cells—Someguy's link describes the upwards motion needed to initiate convective weather activity. Synoptic weather events (large-scale low pressure systems, cold fronts, tropical cyclones) can also produce lightning, but because they occur much less often in a given location, regions where pop-up thunderstorm cells are rare have to rely on these synoptic systems for their fill of electric storms. This is the case for Hawaii, but interestingly, due to the tropical environment surrounding the islands, storm systems that are capable of producing lightning there often go all-out; see here, for example, which discusses such events as 21,000 lightning strikes in five hours. Juliancolton (talk) 20:24, 27 February 2012 (UTC)

How do they measure genetic proximity for unrelated individuals?
In Steven Pinker's The Blank Slate, there is a fairly lengthy discussion of the contribution of genetics, family environment, and "unique" environment to an individual's personality and abilities. The contribution of each is measured according to its role in explaining the variance: more fully, the proportion of variance of the response variable of the sample that is attributable to that characteristic. Note that the three contributions add to 1 (the third is determined by subtraction, I think). I can make easy sense of this when we are dealing with measures that vary continuously, which would include the response variables, since personality measures can be made continuous. But surely the same has to apply for the independent variables, or else we need a categorical variable for each individual. How do they measure, in particular, genetic proximity as an independent variable? I know there are measures of consanguinity, like the coefficient of relationship, but you can only measure a small handful of people on the same scale like this. Furthermore, this is only defined by relationship, not in any absolute sense, so what reference point do you use? What do you do when you are using a large sample of unrelated people? For that matter, how do they measure the family environment? Is it just two categories, "same" and "different"? IBE (talk) 22:17, 26 February 2012 (UTC)


 * I'm having a little trouble parsing your question (which is probably why nobody else has answered it, as well), but to your basic question of isolating genetic relatedness as an independent variable, isn't the answer to this simply by using twin studies? --Mr.98 (talk) 22:35, 27 February 2012 (UTC)


 * Is that what the OP was on about? My first reaction was "Eh? wot?  wot langwidge is dis?".  My second reaction was:  This is some kind of joke ripping us off, or the OP just likes the sound of his own words.  Wickwack121.215.46.219 (talk) 00:25, 28 February 2012 (UTC)


 * Twin studies does give a good overview from what I can tell. The language of my post, imho, is that of mathematics, expressed in words, by someone who doesn't fully understand the concepts involved, hence the question. I also claim to be way ahead of my time, which is why Wickwack can't understand me ;). As for the maths, I can understand when it's presented, but I'm used to one type of study (simple regression, from my undergrad days), and I could see that twin studies didn't fit that particular mould. Twin_studies has the main particulars, so I'll get my head around that and then I'll ask stuff again if still needed. Thanks for the link - I should have checked first, but I'm not used to finding such good details on methodologies, even knowing the WHAA.. principle. IBE (talk) 04:29, 28 February 2012 (UTC)