Wikipedia:Reference desk/Archives/Science/2014 July 7

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July 7

Bird identification

This weekend I was camping in Upstate New York and I saw some birds that I'd like to know more about. I was camping in a hay field and in the mornings there were several birds that were pecking around the field. They weren't there the rest of the day, just the mornings. When I was playing fetch with my dog, and I threw the ball near the birds, the nearest one to my dog would fly near my dog as if trying to scare her away. So, they seem to be at least a little territorial and once I saw that, I stopped throwing it anywhere near the birds.

As far as their appearance goes, they were white and either brown or grey. I didn't want to get very close, so I couldn't be sure about the color. They reminded me a bit of sandpipers in the way they walked. Their beaks were at least an inch long, possibly two. The beak wasn't really long and thin but more triangular. Their backs were brown or grey. The bellies were white. Across the chest coming up from the belly was a horizontal band of the color, then a band of white, and then the neck was colored. And they were larger than sparrows or such but weren't as big as crows.

Any help? Dismas|^(talk) 01:49, 7 July 2014 (UTC)

List of birds of New York may help. --Jayron32 02:01, 7 July 2014 (UTC)

Going through that list, does killdeer work? --Jayron32 02:09, 7 July 2014 (UTC)

Nearly. This image seems to match the color/white/color banding I saw on the chest. Dismas|^(talk) 03:18, 7 July 2014 (UTC)

Note that killdeer are known for diving at animals and people they consider to be a threat, only to veer away at the last moment, in order to drive them away. So, I think that's a match. StuRat (talk) 03:54, 7 July 2014 (UTC)

Thank you, both! Dismas|^(talk) 23:17, 7 July 2014 (UTC)

Dried milk

With the dishwasher temporarily not working, my roommate and I are currently handwashing everything, and sometimes (like now [hangs head]) the dishes pile up for a few days. Of all the dirty dishes that we normally produce, the most difficult to clean are the glasses in which a tiny amount of milk was left to dry out, rather than rinsing it out and leaving a little water behind. Part of this is due to the physical location (it's at the bottom of the glass), but even so, it's far harder to scrape out the dried milk than anything else, as it adheres to the glass with an unusual firmness. Can anyone imagine why? I'm running water into the cup and then using a soap-fortified scouring pad that looks remarkably like this image, if that helps. Nyttend (talk) 02:53, 7 July 2014 (UTC)

When I was very much younger casein glue made from milk was a very effective way to stick things together. That link actually mentions that it is still used in the labelling of bottles, so presumably it works well with glass. Your kitchen may have become a glue factory. HiLo48 (talk) 03:26, 7 July 2014 (UTC)

I don't think it's just milk. Any number of substances that rinse right out with water when wet seem to become well adhered to the cookware once they dry. Consequently, rinsing the dishes immediately saves a heck of a lot of effort later. Also, dishes which lack sharp corners make it easier to wash up. StuRat (talk) 03:49, 7 July 2014 (UTC)

Somewhat OT and I'm not certain this will help in your case but generally speaking if let something which has dried up soak for a while (probably at least 30 minutes) it will be a lot easier to clean up. Re: what StuRat mention, it may not be quite as easy if you hadn't let it dry up, but it's easier than trying to clean it after only a minute or two of soaking. In fact particularly with pots and pans just used for cooking, it may sometimes be easier to clean up after soaking than it is straight away. As for the more general case, beyond just cleaning it up straight away, or at least rinsing out the item, you can always fill it with sufficient water that it's not going to dry up. Nil Einne (talk) 06:13, 7 July 2014 (UTC)

That's my usual approach too. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:22, 7 July 2014 (UTC)

Being rather on the slob side of life, I've found that using very hot water, plenty of soap, and the rough side of a sponge works exceptionally well (even without soaking) - then again, the hot water at my house is very very hot. The simple solution, though, is to rinse out oatmeal, milk, and other things like it ahead of time.Phoenixia1177 (talk) 04:14, 8 July 2014 (UTC)

Is it worth pointing out that the OP actually asked "Why?" HiLo48 (talk) 04:34, 8 July 2014 (UTC)

As in, why does the residue of a liquid cling to the container after the water has evaporated? ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:43, 8 July 2014 (UTC)

I'm not sure if that was addressed to me or the discussion thus far, but it's the same reason that any drying adhesive works. Also relevant: the history section of the Adhesive article mentions casein, Casein Glue, and [1].Phoenixia1177 (talk) 18:57, 8 July 2014 (UTC)

In the case of a liquid in the container that includes anything "sticky" (eg, casein, sugar, gelatine), the sticky component becomes more concentrated as water evaporates. This would be part of the reason why. CBHA (talk) 19:02, 8 July 2014 (UTC)

Level of humidity and comfort/discomfort on the human body

Is there a chart somewhere (on Wikipedia or elsewhere) that breaks down the categories of humidity and the relative comfort to humans? I am referring to the humidity level only. I am not referring to a chart that displays humidity levels alongside actual temperatures (such as the charts located at the article for Heat index). I have looked in Wikipedia and in Google searches and can't seem to find anything. Sometimes, on my local news, the weather report of the meteorologist will include a chart that says something like this: Humidity 50 to 59% = Comfortable; 60 to 69% = Mildly Uncomfortable; 70 to 79% = Extremely Uncomfortable; 80 to 89% = Dangerous. (I just made up those numbers, but the chart would look something like that.) Does anyone know where I can find a chart like this? Thanks. Joseph A. Spadaro (talk) 17:42, 7 July 2014 (UTC)

Any such chart would be very subjective. Some people enjoy high humidity. Some hate it. Some adapt to it, or its absence, over time. And temperature is always relevant to comfort too. HiLo48 (talk) 17:46, 7 July 2014 (UTC)

Relative humidity is very closely tied to air temperature, so you can't have a useful chart without knowing the temperature it was made for. The dew point is a measure of absolute humidity, so it is not related to the air temperature. There is a chart in our dew point article relating the dew point to human comfort. Katie R (talk) 17:54, 7 July 2014 (UTC)

I would speculate your local news was taking a slice through the heat index chart you linked to for the temperature it was expected to be that day. Our heat index chart doesn't break down "mildly uncomfortable" (for 80 degrees all temperatures are in yellow), but I'm sure there are some opinions about that out there. Or, being entertainers, the weather forecasters might just draw the lines ad hoc based on their own preferences. Wnt (talk) 18:47, 7 July 2014 (UTC)

Thanks. Your response confused me. Regarding my local weather report: Why would he do as you suggested? The weather reporter would know the specific local temperature (as you stated), but he would also know the specific local relative humidity as well ... correct? If he knows both values, why would he bother to create that speculative/hypothetical generic chart for other values (that he knows do not even exist today)? That would be akin to him saying something like this: "Today's temperature is 80 degrees F. And today's relative humidity is 52%. Therefore, it will be a relatively comfortable day today. However, if today's relatively humidity was 84% (which it is not), then today would have been very uncomfortable for us" (or something to that effect). Why would he offer hypothetical information like that (via his generic chart), when he knows the exact specific information to offer for the day? Or am I misunderstanding your post? Thanks. Joseph A. Spadaro (talk) 19:33, 7 July 2014 (UTC)

He might have been trying to "educate people about what humidity is". I don't know. It's a TV show for entertainment, there's some creativity involved, and I can't really say what his motivation is. Wnt (talk) 11:32, 8 July 2014 (UTC)

So, if a person knows one statistic (relative humidity) without knowing the other statistic (temperature), there is no general categorization of comfort level? If I saw somewhere that the relative humidity was, say, 75%, that wouldn't tell me anything at all (with regard to comfort level), until and unless I also knew the actual temperature? Is that how this works? Thanks. Joseph A. Spadaro (talk) 19:21, 7 July 2014 (UTC)

Yes, you need both. For me, e.g., 75% humidity at 40F would be chilly, while 75% humidity at 70F would be comfortable, and 75% humidity at 104F would be uncomfortably warm. SemanticMantis (talk) 19:34, 7 July 2014 (UTC)

(edit conflict) Correct. A psychrometric chart can be used to get an idea of the relationship between all the various measures of temperature and humidity, but it can be tough to understand at first. With an air temperature (dry-bulb) of 25 C and 75% RH the chart gives a humidity ratio (measure of absolute humidity) of .015, which a psychometric calculator [2] shows is equivalent to a dewpoint of about 20 C, which out dew point article claims is somewhat uncomfortable for most people. However, with an air temp around 17 or 18 C the ratio is .01 or 14 C dew point, which falls in the comfortable range. Katie R (talk) 19:35, 7 July 2014 (UTC)

Also, notice that the calculator isn't needed - the wet-bulb temperature at 100% RH is the same as the dew point, so that figure can be read right off the chart. It slipped my mind when I first wrote the response. Katie R (talk) 19:42, 7 July 2014 (UTC)

89% here and I'm "mildly uncomfortable" after digging a 3x4x3 foot hole. Three on the UV index. The moon is waxing gibbous. Guess my temperature within three degrees (Celsius) and win a signed copy of "Burnin' Up" by Judas Priest (the only one without a Wiki article). InedibleHulk (talk) 19:54, 7 July 2014 (UTC)

@InedibleHulk:, 25 °C (77 °F). CBWeather, Talk, Seal meat for supper? 01:17, 8 July 2014 (UTC)

Aw, so close! It was 21. Dealer wins. But nobody goes home empty-handed: Here's the never-overplayed "Living After Midnight". InedibleHulk (talk) 01:25, 8 July 2014 (UTC)

Both temperature and wind speed figure into it. As an example, 20 below with low humidity and calm winds can be a lot easier to take than 20 above with high humidity and strong winds. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:36, 7 July 2014 (UTC)

Thanks. So this is the part I am not understanding. I look at my local weather report (or I watch it on the TV news). The weather guy tells me what today's temperature is. The weather guy also tells me what today's relative humidity is. After knowing these two values, I then have to go "dig up" that heat index chart to make sense of what this all means? I can't imagine that the TV weather reporter works on the premise that after he offers his data, his viewers go dig up that heat index chart to make sense of it all. No? Joseph A. Spadaro (talk) 19:43, 7 July 2014 (UTC)

Local weathercasters that I'm familiar with will usually give the heat index as well, especially on a very warm day. As in, "It's 87 but it feels like it's 93." ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:19, 7 July 2014 (UTC)

Is it more likely that the local weather reporter was offering a chart/graphic based on the chart located at the dew point article under the section titled "Relationship to human comfort" (using the second and third columns of that chart)? Maybe the weather reporter was discussing (on his chart) humidity as measured by dew point (in degrees) rather than humidity as measured by relative humidity (in percent). Does that seem more likely? Joseph A. Spadaro (talk) 19:50, 7 July 2014 (UTC)

Yes. I agree with Katie that dew point is a much more useful measure of humidity. I use this site to get the dew point forecast, since my local weather station is similarly useless: [3] (I normally only select the temperature and dew point check boxes). Specifically, I need to know whether to leave my windows open with fans in them at night or not. With a dew point over 70F, forget it, the humidity isn't worth it, I run the A/C all night instead. With a dew point under 60F, it is worth using the fans. Between 60 and 70F, it depends on how hot and humid it is inside.

Now, as to how relative humidity got to be what is reported on weather forecasts, that's a mystery to me. It's just nowhere near as useful as the dew point. Weathermen do provide all sorts of extraneous info, seemingly designed to prove how smart they are, that has nothing to do with how to plan your day. Telling you what it would feel like if we changed the temperature or humidity by a given amount is just one example. StuRat (talk) 20:01, 7 July 2014 (UTC)

As I understand it, the dew point is about as low as the temperature is going to get until the next air mass moves in. Hence it can feel muggy at 70. In the frozen north, as you may have noticed, when the humidity is reasonable you have to scrape the frost off your car in the morning. When it gets to 20 below, there may be no frost to be scraped off. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:22, 7 July 2014 (UTC)

(ec) Not everything a meteorologist discusses is made for telling people what kind of shirt to wear today, though. A landscaper might awake in the morning and look at the RH, for example; near 100% indicates that there's probably quite a bit of dew on the grass, and he should wait before firing up the lawnmower. He could arrive at a similar conclusion by looking at the current DP and temperature, but that's true of many indices a meteorologist provides. In general the DP is much more useful than RH, but I wouldn't assume your local weatherman shows both to boost self-satisfaction... it's just standard as part of any weather broadcast. – Juliancolton | ^Talk 20:25, 7 July 2014 (UTC)

Here the local TV stations rarely tell us the dew point, but tell us the relative humidity religiously, as if it was somehow important. StuRat (talk) 20:59, 7 July 2014 (UTC)

It is religiously important. Humidity's our proverbial scapegoat. If we blamed the sun directly, we'd anger Him. And nobody wants an Angry Sun. InedibleHulk (talk) 21:04, 7 July 2014 (UTC)

Thanks, all. Joseph A. Spadaro (talk) 03:43, 12 July 2014 (UTC)

ZrZn₂

What do we call this compound? It exists, since apparently it's been reported as a possible ferromagnetic superconductor, but that's all I know. I didn't realise that it was possible for such metal-on-metal compounds to exist, and the naming isn't mentioned in IUPAC nomenclature of inorganic chemistry. Nyttend (talk) 23:53, 7 July 2014 (UTC)

Is it not a ceramic, in the same fashion as other metal/semimetal compounds from comparable chemical groups, like hafnium diboride, titanium dioxide, and zirconium diboride? ... or is it an alloy with more metallic-like characteristics? It seems to be a unique material that's somewhere in-between. There are a wide variety of research papers [4] [5] [6] that seem to indicate a diffusive equilibrium of zinc-zirconium, with many possible stoichiometric ratios coexisting. That sounds like an alloy almost by definition.

This paper - The Zn-Zr System (Dutkiewicz 1992) appears to be the grandfather-paper that's commonly cited among all the others. It may be the authoritative reference. Nimur (talk) 01:34, 8 July 2014 (UTC)

The typical term for such a compound is an intermetallic. Mr.Z-man 03:19, 8 July 2014 (UTC)

I'm sorry: I meant "what do we call this specific compound", like how we call NaCl "sodium chloride", not simply "a salt". Nyttend (talk) 04:46, 8 July 2014 (UTC)

Zirconium dizincide - there are other dizincides, as shown here (I've found reference to calcium, copper, magnesium, platinum and sodium versions). Mikenorton (talk) 07:11, 8 July 2014 (UTC)

Or just zirconium zincide, as in this US patent (assuming that's not ZrZn). Mikenorton (talk) 19:59, 8 July 2014 (UTC)