Wikipedia:Reference desk/Archives/Science/2012 July 24

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July 24[edit]

volcanos[edit]

Were there ever volcanos in ogemaw county michigan? — Preceding unsigned comment added by 75.219.52.40 (talk) 00:50, 24 July 2012 (UTC)

Yes. --Demiurge1000 (talk) 00:53, 24 July 2012 (UTC)


"Ever" is a long time. There was likely a point near the beginning of the formation of the Earth that the entire planet was molten rock. Starting from that, what counts as a volcano?
DMahalko (talk) 01:10, 24 July 2012 (UTC)
Did "ogemaw county michigan" exist back then? 203.27.72.5 (talk) 08:10, 24 July 2012 (UTC)
It has been proposed [1] that a strongly reflective sequence imaged on COCORP (another article to write) data with a top at about 8km (5 miles) is the lower Keweenawan volcanics (which formed about 1,100 million years ago). So the answer is yes, but a very long time ago. Mikenorton (talk) 12:10, 24 July 2012 (UTC)

latex usage statistics[edit]

I'm looking, please, for statistics on how latex from rubber trees is used: what percentage or vloume goes into, say, tyres, clothing or - particularly - party balloons. I've searched the web and both Wikipedia and reference desk archives, without success. Andy Mabbett (Pigsonthewing); Talk to Andy; Andy's edits 13:37, 24 July 2012 (UTC)

Ansul Fire Suppression Systems[edit]

While at an amusmement park cafeteria, I noticed that the fire suppression system appeared to have been activated at some time and had never been reset; the pull station near the grill looked as if it had been activated. I know what an Ansul pull station should look like because I'm a food service laborer myself. If I'm not mistaken, food service establishments are supposed to shut down pending an inspection after that system has been activated, yet the cafeteria was still serving guests. Obviously, if the facility was operating without a functional suppression system, it poses a serious fire and public safety hazard. So my question is, is there any chance I'm wrong on this? 76.7.95.112 (talk) 14:14, 24 July 2012 (UTC)

I can't judge the chances of you being wrong. But many health departments and fire marshals conduct random inspections of eating establishments. Wouldn't it be far more useful for them to conduct an inspection of a place where there is a reasonable suspicion of a problem rather than a random check? Jc3s5h (talk) 14:44, 24 July 2012 (UTC)
You should report your suspicion to the relevant safety authority. It's no skin off your nose if you're wrong, and the possibility you could save lives if you're right. Rojomoke (talk) 15:48, 24 July 2012 (UTC)
The system may be still functional, as discharge can be triggered automatically be heat sensors etc. Or it may have been completely replaced by another supplier. However, even if this is so, and the pull station is still in situ and inactive, it is a hazard as in an emergency someone might recall the location of the pull station and expect it to work. And if they are sloppy enough to have a disconnected or disable pull station, it s not a good sign that the rest of teh system is maintained. I suggest asking for the duty manager and politely and courteously pointing it out - give him/her a chance to fix it. If you don't get a suitable response, or if it's unchanged after a week, dob them in to the authorities. I wouldn't have too many qualms about dobbing them in, as restaurants, especially fast food restaurants, have a high fire probability, and customers are at risk. Ratbone120.145.168.58 (talk) 15:50, 24 July 2012 (UTC)
You'd think that one of their competitors would have ratted on them already, wouldn't you, all being fair in love, war and business, and all...? --Kurt Shaped Box (talk) 23:29, 24 July 2012 (UTC)
Not at all. Quite apart from the fact that a competitor may not know about it for the same reason the authorities don't know about - they haven't been there - it is not generally wise to rat on your competitors. It's not professional, for several reasons, inluding: it can be seen as unfair competition; it's not wise to throw stones unless you are very sure you don't live in a glass house; it brings down the public's view of the industry (in this case restaurants) generally; it invites retaliation. In any case, in my experience as a building manager over several years, quickie/fast food/snack restaurants, unless run as branch/franchise of a major chain, are run by unqualified people who just don't know any better. That applies to the competitors of any one outlet. Major chains are different as they get good advice from the franchise owner; 5-star & similar quality service restaurants are a very different story - they have managers and executive chefs who are properly qualified and do know what their obligations are. Ratbone124.182.2.27 (talk) 01:33, 25 July 2012 (UTC)

Specific heat capacity[edit]

Does specific heat capacity refer to specific heat at constant volume or constant pressure? Thanks. 82.132.235.213 (talk) 14:38, 24 July 2012 (UTC)

  • For gasses there is a separate specific heat for constant pressure and constant volume. The difference between these is the gas constant R. Tombo7791 (talk) 15:29, 24 July 2012 (UTC)
For gasses, it is equally valid, and in both cases useful, to quote/use/dicuss the specific heat (aka thermal capacity) for both constant volume and constant pressure - the value for constant pressure being greater. The symbols normally used are Cv and Cp. You often find textbooks on reactions however, that only talk about constant pressure, because most chemists carry out reactions at atmospheric pressure, and combustion in many applications is carried out open to the atmosphere. In such cases they may not explicitly state that it is the constant pressure value. So you need to be aware of this.
[Incorrect sentence deleted by Ratbone]
Note that the correct standard term in science is specific heat - there is no need to append the word capacity. In engineering, the term thermal capacity is often used.
Ratbone120.145.168.58 (talk) 15:31, 24 July 2012 (UTC)
I have a problem which gives you specific gas constant, specific heat for air, power of a fan, temperature of the room, dimensions of the room, and the problem requires the temperature to be calculated after a certain time. I assumed e=pt and e=mct is the right equation to use but it doesn't give me the correct answer. Thanks. 176.27.223.180 (talk) 16:03, 24 July 2012 (UTC)
What do you mean by e=mct? that seems wrong
energy=mass x specific heat x change in temperature 176.27.223.180 (talk) 16:49, 24 July 2012 (UTC)
Rooms operate at atmospheric pressure - the pressure does not change. Therefore in your example it is the constant pressure value that is the correct one to use. In practical real world rooms, as the air heats up, some of it will leak out, so that pressure does not change. Be carefull - if this is an assignment question, who ever set it just might have had a sealled room or box in mind. That would be wrong, but, hey, teachers do forget things so as to keep questions simple. You did not provide the specific heat value you were given. The correct Cp value for dry air at 300 K is 1.007 kJ/kg.K and is a reasonable value to use in this case if humidity is not given. Note that specific heat changes somewhat with humidity. It also changes with temperature, but only negliglibly so over any temperature range appropriate to this question. Ratbone124.182.2.27 (talk) 01:50, 25 July 2012 (UTC)

Is there a correlation between incidence of type 1 diabetes and vitiligo?[edit]

Does the data indicate that if you have one, the probability of you having the other is higher than that of someone who doesn't have the one? 20.137.18.53 (talk) 15:13, 24 July 2012 (UTC)

Yes; 2% to 10% of those with T1DM have vitiligo. See PMID 20009114. 207.224.43.139 (talk) 21:10, 28 July 2012 (UTC)

Blood filter[edit]

I was giving blood and commented about the length and complexity of the hoses in the collection bag and the technician started to explain and commented that the pink disk was a filter that he thought was to remove white blood cells (but wasn't sure what it was filtering.) As a filter it makes sense but how would you filter out white blood cells without removing the red cells? Does anyone know about this filter? RJFJR (talk) 15:48, 24 July 2012 (UTC)

It's a process called leukoreduction. They basically use layers of filters to remove anything larger than red blood cells. It isn't a perfect system though because about 10% of the red blood cells are lost in the filtration. Tombo7791 (talk) 16:11, 24 July 2012 (UTC)
(ec) The filter that you saw almost certainly was for leukoreduction. The removal of leukocytes from transfused blood products seems to reduce the incidence of some post-transfusion side effects, as well as potentially reducing the transmission of some diseases. Filtration of leukocytes is actually fairly straightforward. Leukocytes (white blood cells) are appreciably larger than erythrocytes (red blood cells) and other blood components; they are also 'stickier' under some circumstances and can be somewhat selectively adsorbed on to some filter materials. In-line filters work by trapping leukocytes within the pores of the polymer filter material, while allowing the smaller blood components to pass. TenOfAllTrades(talk) 16:15, 24 July 2012 (UTC)
Thank you. I just assumed red blod cells and white blood cells were about the same size. RJFJR (talk) 17:11, 24 July 2012 (UTC)
IMHO, the picture at our White blood cells article seems to support that assumption. They look more spherical rather then disk shaped, but certainly not at a scale that looks like it would filter out.. Maybe there's something more clever then just "size" at work.. Vespine (talk) 22:41, 24 July 2012 (UTC)
This page says that one form of white blood cells are 1/700 the size of red blood cells, so there is a discrepancy here. --TammyMoet (talk) 09:00, 25 July 2012 (UTC)
This page is clearly wrong. Granulocytes, the type of white blood cell the page is talking about, are about 12 micrometers on average in diameter. Red blood cells are around 6 micrometers. From my own experience as biologist I can state that erythrocytes are smaller than all kinds of white blood cells. Size filtration is therefore a simple and effective strategy to reduce the amount of other cells. You can also have a look at leucocyte, where I found a nice table with diameters for the most relevant leucocytes in blood. Btw: There are no mammalian cells (or no cells at all) 1/700 the size of an erythrocyte. Mycoplasma, one of the smallest bacteria and one of the smallest cells known, is 0.1 micrometers in diameter, which is just about 1/60 of an erythrocyte. --TheMaster17 (talk) 11:53, 25 July 2012 (UTC)
In addition to being smaller and less adherent than WBC, RBCs are not nucleated and are easily deformed. -- Scray (talk) 06:02, 27 July 2012 (UTC)

How many quantum fields are there?[edit]

Is there just one quark field, or are there six different quark fields? What about gluons, leptons? Is it accurate to say that fields are more fundamental than particles? Goodbye Galaxy (talk) 15:53, 24 July 2012 (UTC)

There is just one field, I suppose. The different particles are different types of oscillation of the field. As an example, a rope under tension can oscillate up and down as well as side to side; those are two "particles". Diagonal oscillation is a combination of those two basic oscillations. You can also take two other perpendicular directions (diagonals) as the fundamental directions and express everything in terms of those. If the rope is in outer space, those directions are equally good, but if there's a gravitational field in the up-down direction, it breaks the symmetry and the description in terms of up-down and left-right is simpler. This is what happens in the standard model: after symmetry breaking, there are favored directions corresponding to electrons, etc. The symmetry of the gluons isn't broken, though, which is why you'll often hear that there are eight gluons but you'll never see a list of what they are. They are eight different arbitrary directions.
I think it's accurate to say that fields are more fundamental in the standard model, because of nonperturbative effects like the Higgs mechanism (which involves the Higgs field, but not the Higgs boson). -- BenRG (talk) 16:16, 24 July 2012 (UTC)
Counting the number of fields (or particles) is a tricky business. First you have to decide what counts as different fields (or particles) and what doesn't. Add to that the fact that particles and fields are not counted the same way. What BenRG said above is only partially correct. If we make the reasonable assumptions that fields that belong to a given multiplet should be counted only once, than there are 9 quark fields (3 per generation) and 1 gluon field. Each generation has a weak-doublet strong-triplet left handed quark field and 2 weak-singlet strong-triplet right handed quark field for a total of 3 fields (double that to 6 if you decide to count anti-matter separately). Gluons on the other hand are represented by a single weak-singlet strong-octet field (do not double it if you decide to count anti-matter separately since gluons are their own anti-particles but double it to 2 if you decide to count each possible spin state (helicity) separately). So, forgetting about spin states and anti-matter for simplicity (too late), either you say that there are 8 gluon fields and 36 quark fields (12 per generation - 6 for the weak-doublet strong-triplet and 3 for each of the two weak-singlet strong triplets), or you say that there are 9 quark fields and 1 gluon field as previously stated. If counting particles instead of fields than you are really counting mass eigenstates in which case there are 6 quarks and 1 gluon. Dauto (talk) 16:59, 24 July 2012 (UTC)
Interesting. I remember hearing someone (whom I assumed knew what he was talking about) talk of there even being meson fields and proton fields. Is this accurate, or merely easier to comprehend? Goodbye Galaxy (talk) 17:36, 24 July 2012 (UTC)
That can be done, yes, but keep in mind that this is an approximate theory much like newtons gravitation is an approximation for general relativity. It has its domain of application and its limitations. The meson and hadron fields are not introduced in addition to the quarks and gluons. They are introduced instead of them. Dauto (talk) 21:54, 24 July 2012 (UTC)
It can't be wrong to say that there's one field, just as it isn't wrong to say that a hydrogen atom is a single object. It's just terminology. The division of the fermion field(s) into generations doesn't really make sense (what are the three generations of left-handed quarks?). The rest of it is well defined but I'm not convinced it's all that helpful. There was just a thread in which someone complained about the seeming arbitrariness of the SM fields and I mentioned that the gauge fields are SO(10) broken in a certain way and the fermions all fit in one big "hexadecet" of SO(10). Even if SO(10) grand unification doesn't work you can still define the standard model this way, and I think it's nicer (at least it's shorter). Also, I think the mass eigenstates of the neutral kaon system are perfectly good particles and can reasonably be said to be orthogonal vibrations of the quantum field. If you subdivide the field based on the fundamental particles the neutral kaons end up with a second-class status that seems undeserved. -- BenRG (talk) 00:52, 25 July 2012 (UTC)

Why don't constellations move?[edit]

Stars move, but yet constellations are still the same shape. For example, why is the Big Dipper, still the Big Dipper, shouldn't it just be an amorphous jumble of stars by now? 148.168.40.4 (talk) 17:38, 24 July 2012 (UTC)

Stars do move in the sky, just very very slowly, because they are so far away. According to this article, most constellations in our sky should be unrecognizable in about 100,000 years. Goodbye Galaxy (talk) 17:44, 24 July 2012 (UTC)
Simply, the 2,500 yrs that humans have plotted the stars is an insignificant amount of time when relating to the speed and size of the universe. All of the movement that we see from the stars is from the Earth's own motion rather than that of the stars themselves. Tombo7791 (talk) 18:59, 24 July 2012 (UTC)
This website has an indication of how familiar constellations are predicted to change in 50,000 years. --TammyMoet (talk) 19:46, 24 July 2012 (UTC)

The article you want is proper motion. μηδείς (talk) 22:00, 24 July 2012 (UTC)

Urban OS[edit]

What exactly is the urban OS & what are the advantages of it? 176.27.223.180 (talk) 17:44, 24 July 2012 (UTC)

Here's a BBC article on Urban OS; many more references are readily available via search engines. It appears to be a largely-theoretical loosely-defined notion of automating various features of city management (see, from the above article: "this is what Urban OS is providing, this kind of solution to analyse mass data, enter it in a context and perform magical actions."). — Lomn 18:03, 24 July 2012 (UTC)

Why can milk splatter so high?[edit]

Actually I'm sure this doesn't have to do with milk specifically, but when it happens with milk it's more important to clean it up than with water.

When I'm pouring milk from a box with a narrow hole, and especially when it gets interrupted to let air replace it, the milk often splashes higher than any part of the box. I think the milk has potential energy as a function of the head between the glass and the box, which turns into so much kinetic energy when it reaches milk already in the glass, but I always thought that a falling object could never bounce as high as it started because that's all the energy it had (and some of it will have been lost). So how or why does some of my milk splash high enough to land on the top of the box?

80.90.168.44 (talk) 18:08, 24 July 2012 (UTC)

It would be impossible for all of the milk you pour to splash higher than the starting point, but that doesn't prevent the kinetic energy of the whole getting concentrated into a smaller quantity of fluid and thereby causing it to rise higher. Fluid mechanics is a very complex subject and there are lots of strange things that can happen. Looie496 (talk) 18:33, 24 July 2012 (UTC)
For something similar, see Galilean cannon. Whoop whoop pull up Bitching Betty | Averted crashes 18:44, 24 July 2012 (UTC)
Another example is a tsunami, where a large volume of water with a small elevation becomes a smaller volume with more elevation when it hits the shallows. StuRat (talk) 21:20, 24 July 2012 (UTC)
This NPR story may be helpful in seeing what is going on. Looie496 (talk) 18:40, 24 July 2012 (UTC)
Aha, thanks everybody.Tom Haythornthwaite 01:55, 25 July 2012 (UTC)
Resolved

Mallorca sea levels 1 m higher 81,000 years ago than today?[edit]

Ice Age Temperature.png
Ice-core-isotope.png

Hi. I recently came across this article in Nature, which suggests that calcite-dated cave deposits show that sea levels during the height of the last ice age were one metre higher than present, even as data from elsewhere in the world suggest that sea levels should have gone down by several metres around that age. The first thing that came to mind was that the Mediterranean Sea had once been separate from the rest of the Atlantic Ocean prior to an event called the Zanclean flood, but that had been 5.33 million years ago. Could the calcite records somehow be corresponding to a local sea level change as ice sheets covered much of France and freshwater could have flowed into the Sea of Sardinia which at the time would have had little contact with the Atlantic and the rest of the Mediterranean, potentially creating a discrepancy and lag time between the local and global sea levels? I have included the Antarctic and Greeland ice core data for comparison. It appears that EPICA (Dome C) in Antarctica hits a peak almost corresponding directly to 81,000 years BP, while Greenland and Vostok experience a peak at about 84,700 years BP. Interestingly, global ice volume was at a low around the same time period. Basically, is it possible for a local ice age-era melting event around southern France or the Pyrénées mountains to infill the Sea of Sardinia quickly enough that sea levels rise about 10 - 28 metres higher than eustatic (global) sea levels? Finally, why does this image suggest sea levels were up to 9-10 metres higher than today during the Holocene climatic optimum, directly contradicting this image, which shows sea level estimates no more than 4-5 metres higher than today? Disclaimer - most of this information was acquired through pixel analysis. Thanks. ~AH1 (discuss!) 20:12, 24 July 2012 (UTC)

Aside: is the article on climate oscillation accurate? ~AH1 (discuss!) 20:12, 24 July 2012 (UTC)
I don't know where there cave was but this paper suggests that there is modest, but active faulting affecting the island, with one normal fault, the Sencelles fault, having an estimated displacement of 100m during the Pliocene to Quaternary (a 5 million years period), which gives an average of 1 m displacement every 50,000 years. The researchers have probably taken account of this, but it might be relevant. Mikenorton (talk) 20:58, 24 July 2012 (UTC)
Yes this is in an active seismic area, and a 1 meter change in elevation in 80000 years is really nothing extraordinary. GPS readings may not yet have the resolution to determine such a small rate of change. To tell what the sea level was then it would be best to determine this in more stable regions of the earth. Graeme Bartlett (talk) 22:09, 24 July 2012 (UTC)
Let me first note that the primary publication underlying this is a Science paper, http://www.sciencemag.org/content/327/5967/860. All of these issues of tracing sea level fluctuations are tricky, and I don't think the method used in that paper has really been thoroughly validated. Regarding some of the other comments here, sea levels are thought to have been around 120 meters below today's values during the Last Glacial Maximum, around 20,000 years ago, so the differences being discussed here are relatively moderate. Looie496 (talk) 22:39, 24 July 2012 (UTC)

Carbon balance[edit]

I live precisely 2.4 miles (3.9 km) from the recycling centre, and I drive a 1.2 litre Renault Clio. How many aluminium coke cans do I have to take to the recycling centre before I offset the carbon emissions spent getting there in the first place? -- roleplayer 21:17, 24 July 2012 (UTC)

Is that an attempt to ask a real question in a clever way? If so, could you please be less clever? Looie496 (talk) 22:19, 24 July 2012 (UTC)
He is asking us to weigh the carbon cost of driving 8km round-trip vs. recycling an arbitrary amount of pop cans. I.e., how many cans must he recycle just to break even? Consider the clear counter-productivity of driving 8km to recycle one can. From a quick googling, that car is roughly 6L/100km (highway or city I do not know) which gives a ~500mL fuel expenditure estimate. The first decision is whether you're going to look at this as an energy efficiency problem or a pollution minimization problem. The second problem is getting pop can data for either scenario. BigNate37(T) 22:34, 24 July 2012 (UTC)
If you give up the coke and switch to drinking filtered tap water from a reusable bottle then you eliminate this dilemma from your life and you may find that you will sleep better at night. SkyMachine (++) 22:26, 24 July 2012 (UTC)
"The Aluminum Association estimates that the energy saved in recycling a single aluminum can could power a television for 3 hours."[2] So you merely need to convert TV power to Renault Clio power. 207.224.43.139 (talk) 22:35, 24 July 2012 (UTC)

I'll rephrase the question for Looie. "Assume that the fuel used to power the mining, refining and shaping of the aluminum for an aluminum is derived from oil. Assume that my car also burns an oil product. My car consumes an amount of fuel "y" to make a round trip to the recycling center, whereas the de novo creation of an aluminum can ultimately consumes an amount of fuel "x". The number of cans I take with me is "n". For a given value of "y", and a value of "x" that may be provided in a reference, find the "n" for which nx = y. I believe that is as unclever as I could make it. Someguy1221 (talk) 22:38, 24 July 2012 (UTC)

N.B. "Recycling [aluminum cans] consumes 3.5 kilotwatt hours of electricity, one-eighth of that required when using new material." From Aluminum can#Recycling. BigNate37(T) 22:42, 24 July 2012 (UTC)

Wow, reading that statement's source... the article has it wrong. For now, see [3]. I'm going to fix that article. BigNate37(T) 22:45, 24 July 2012 (UTC)

The answer depends heavily on where the power for the aluminium smelter was sourced. If it was hydro or nuclear, then you will have to cart an awful lot more to break even. If it was coal, oil or natural gas it might not be so hard. 203.27.72.5 (talk) 23:07, 24 July 2012 (UTC)

  • Let x be the energy saved by recyling an aluminum can. Then x ≐ ​783.5kW·h (from Aluminum can#Recycling, which I've now fixed)
  • Let y be the energy cost of driving to your recycling centre. I assume you do not employ the first of the three R's by combining the trip with other business. Thus y = Egas(500mL) = 0.5L × 9.7 kW·h/L (from Gasoline#Energy content (high and low heating value))
  • nx = y ⇒ n ≐ ​yx

For which I get ~1.6. Better make it two whole cans, just to be safe. BigNate37(T) 23:20, 24 July 2012 (UTC)

Seems quite low. Is that just considering the fuel burnt, or carbon generated by the life cycle of the car, as well ? StuRat (talk) 23:23, 24 July 2012 (UTC)
It also goes without saying that more cans in a load is better for the environment. StuRat (talk) 23:32, 24 July 2012 (UTC)
At those numbers, an aluminum can would cost something like 60 cents based on California consumer electricity prices. How much does electricity cost aluminum smelters typically? It just seems like a fairly large chunk of the cost of a can of coke. But maybe the smelters get it cheap since they use so much? Someguy1221 (talk) 23:33, 24 July 2012 (UTC)
Well all the links are there, so you can track down the information to see. I only did a cursory check into those figures. I recall seeing 2.5 cents quoted somewhere as the cost of an aluminum can, but that was qualified by a disclaimer. BigNate37(T) 00:47, 25 July 2012 (UTC)
Yes, 60 cents per can can't be right. StuRat (talk) 02:06, 25 July 2012 (UTC)
I've removed the NY Times figure from the article. It's apparently off by at least an order of magnitude (see talk). Manufacturing cost for the aluminum in one can appears to be about 0.2 KwH. Plugging this figure into BigNate37's calculations gives an answer closer to 25 cans. -- Tom N (tcncv) talk/contrib 02:34, 25 July 2012 (UTC)