Wikipedia:Reference desk/Archives/Science/2016 March 22

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March 22

Dust in air: outside vs inside

Can you reduce dust floating around in the air by opening a window or is there as much dust floating around outside as inside? I don't live near any industrial facilities I would expect to be churning out dust. --78.148.107.251 (talk) 08:52, 22 March 2016 (UTC)

I think that would depend very much on what is going on both inside and outside. Outside you will often find pollen as well as dust, and you need to take into account the direction and strength of the wind. Inside dust will depend on how much movement there is to churn it up into the air. The answer will be sometimes yes and sometimes no. Air conditioning can have filters to eliminate or reduce the dust that enters the room. Electrostatic devices on the market claim to be able to reduce the dust in the air of a room. Dbfirs 08:59, 22 March 2016 (UTC)

Depends on weatherconditions and season. On a rainy day the air outside will be near dustfree. In spring and summer you will have weeks when outside air is so filled with Pollen and/or spores you better keep your windows shut unless it is/was raining. --Kharon (talk) 15:37, 22 March 2016 (UTC)

Desert dust floats around in lots of places - especially in dry climates - and not just the Sahara! For example, here in California, that stuff leaves a mess on the windowsills if you leave the windows open, and it accumulates fast.

NASA has studied atmospheric aerosols and found desert dust at altitudes as high as 15,000 feet above sea level. Not only does natural dust make a mess in the house, it also affects global climate!

Our State Government even publishes this fun comic book, Fugitive Dust Control, from the California Air Resources Board. It's not just a nuisance - it's air pollution! A lot of dust is natural, but human activities like farming, construction, and motor vehicle traffic can significantly aggravate it, especially by getting large particulates up to higher altitudes where natural winds can carry them farther and higher.

Last year, the Pulitzer Prize was awarded to Diana Marcum for her photographic series on the "Dust Bowl" that we've been experiencing for the last few years. We finally got some rain and snow in 2016!

Nimur (talk) 16:17, 22 March 2016 (UTC)

A lot depends on local conditions. On average, indoor environments tend to be dustier by 20-50% than outdoor environments. So on the typical day, opening the windows will improve indoor air quality. However, day-to-day air quality can often see outdoor dust levels swing by factors of 2 or 3. On a day when the external air is unusually bad, opening the windows may make things inside worse. You also don't have to live near industrial plants to have bad air outside. Contaminant plumes can travel hundreds of miles when conditions are right. Here are a couple maps to help look up your local air quality right now [1][2][3]. On the other hand, certain indoor activities, including smoking, cooking, and using a fireplace, can rapidly increase the level of indoor particulates. (This is a huge problem in third-world areas that use coal, kerosene, or firewood for cooking and personal heating.) If you have resources and the inclination, the best way to reduce indoor dust is with a HEPA filter, either on a central AC / Heating system or as a stand-alone unit with a fan. The electrostatic devices Dbfirs mentioned tend to be more gimmick than actual benefit. Most of those have a poor flow rates and so take much longer to clean the air than filters, and they also generate small amounts of ozone which can be more annoying than the dust depending on how sensitive you are to ozone. Dragons flight (talk) 17:43, 22 March 2016 (UTC)

Also, it's not just a matter of which is dustier, inside air or outside air, as air passing through a house tends to slow down and drop it's contents. I've noticed that parking in a carport makes my car much dustier than out in the open, for the same reason. So, opening the windows to reduce dust doesn't seem like it would help. On the other hand, opening a window to change the temperature, humidity, and mix of gases inside the house can help a lot, especially with window fans. StuRat (talk) 17:52, 22 March 2016 (UTC)

In some countries there are flyscreens attached to the windows. It's not just a question of dust, insects can get in as well. 78.149.118.97 (talk) 14:29, 23 March 2016 (UTC)

I think a large part of your decision should not just be about the quantity of dust - but rather what it's made of and what the particle sizes are. Most indoor dust is dead human skin cells (and pet dander if you have one or more pets) - but outdoor dust can be fine soil particles, carbon from diesel engines, cement particles, pollen, all sorts of things. We know that the very fine dust produced from diesel engines is really harmful - for example - and pollen is responsible for a bunch of allergies. So it might be that by opening the windows, you reduce the total quantity of dust by hugely reducing the amount of harmless dust and actually increasing the quantity that is harmful. That consideration makes this be a tougher decision than just "how much dust" would suggest - and it depends a lot on whether you have allergies and/or respiratory problems such as asthma. SteveBaker (talk) 14:30, 23 March 2016 (UTC)

Most indoor dust is outdoor dust that came inside: [4][5]. The oft-reported (and rather icky) claim that indoor dust is mostly human skin is simply a myth. Human skin of course contributes, but unless you've got a serious skin condition you aren't going to be the main source of dust in your home. Dragons flight (talk) 14:56, 23 March 2016 (UTC)

Was just discussing this with a friend. I live in Tucson (desert), 150-feet from a main street, you can see the busses sometimes kicking up dust. In addition to diesel there are fine particles of rubber from the car tires. I asked my friend, who has lived in different parts of Tucson, including next door to me if he thought dust was worse here than other parts, he said, "here." Haven't looked on WP yet for articles on dust but thanks, Nimur for the link to Mineral dust, which is a big problem in Green Valley, 30-miles south of Tucson. Raquel Baranow (talk) 14:47, 23 March 2016 (UTC)

• Lets go back to the OP's question and see it if it it makes practical sense to him.... He indicates that he lives outside a industrial area. If he keeps his windows always closed, the air inside may become dryer (unless he is lucky enough to have an old fashion wife that ignore modern frozen veg and instead boils everything on the wood fired range, instead of shoving it all in the microwave). It is better for health to have a reasonable exchange of out side air- especially if he lives in a modern draft free home. The more moist out-side air will neutralize the electro potential of dust, allowing it to settle. Buy a cheap humidity meter – they are actually rubbish and inaccurate but it will make one more aware of the humidity. If ones eyes feel dry or the nose feels not quite right, it becomes obvious that the humidity has dropped too low. So, don't keep your home too dry. Meaning by that the whole family may get colds because their nasal passages have dried up -which happens with British style central heating. If your worried by dust, then take Dbfirs advice. Invest in a air ioniser. Don't by cheap. For one that is any good at all will cost about a hundred Euros but I have one and it was worth it. Finally cat dander. Some people think they have dust problems because visitors wheeze – even though the home owner don't own a cat. Simpler explanation: In your part of the world, don't bother looking for cats. Just get a shot-gun-licence and stay up for a few nights and blast way at any haggises that try to get into you home. Mind you, wear wellys, as their teeth are razor sharp. Don’t take my word for it – talk to your neighbours.. Get one of those critters cornered and their incisor can go the a rubber gumboot like a hot knife though butter. Which is why you never see them (or being allowed ) to kept as domestic pets in England.--Aspro (talk) 21:13, 23 March 2016 (UTC)

'Posting by banned user removed. Fut.Perf. ☼ 08:45, 25 March 2016 (UTC)

I don't think A/C itself cleans the air. However:

1) Central A/C likely has some air filter(s) to clean the air it circulates. Window A/C units may have filters, too, but in either case they require regular cleaning or replacing to do much good.

2) A/C can generate mold (and mold spores) if the condensate isn't properly drained. Or, even worse, Legionnaire's Disease.

Also, can I ask why you've never switch the extractor on ? Only plan to use it if you burn something badly in the oven ? StuRat (talk) 21:47, 23 March 2016 (UTC)

@ 90.215.70.109 have you ever ventured into your attic (the space above the top floor ceilings and the roof tiles) to look at the ventilation ducking? If you don’t have an attic just look in the loft. You may find it goes through a sort of box with a power cable attached before venting outside. If so, that will be your economizer that recovers heat -to reduce your winter fuel bills. --Aspro (talk) 23:30, 23 March 2016 (UTC)

We do have an article on dust. People with specific medical conditions might pay attention to pollen or dust mites. But I am suspicious that there is a lot of hooey put out by people looking to sell noisy equipment. Our ancestors lived in little huts with a fire in the middle and a little hole at the top to let the smoke out, and we've come a long way since then. And for most non-allergy sufferers, an abundance of antigens is just an opportunity to reinforce immunological tolerance. (A wild speculation I favor is that sniffing flowers is a behavioral instinct to induce just that...) Wnt (talk) 23:57, 23 March 2016 (UTC)

Crude ash content of food

Dog food and cat food labels often indicate the proportion of ash in the food. Our article on kimchi says it contains 0.5 g "crude ash" per 100 g. Our article on ash doesn't say anything about what the term means in reference to food. On the website of an animal feed manufacturer [6] it's explained that crude ash refers to the total mineral content of the food. How do we want to accommodate that information at Wikipedia? Should we have an article on crude ash? Should that term redirect to ash? If the latter, then could someone with a better understanding of the issue than me please add the food-science meaning of ash to the article? —Aɴɢʀ (talk) 21:54, 22 March 2016 (UTC)

The idea for reporting crude ash is that it is an easy thing to measure: just burn the dog food and weigh what's left over. That "crude ash" measurement is almost entirely made up of minerals from animal sources, though plant ingredients may contribute some small amount as well. Meat and bone meal is the source of crude ash in many pet foods. We also have articles on bone meal and blood meal that may be relevant. Crude ash could also be mentioned at Food_composition_data. SemanticMantis (talk) 22:10, 22 March 2016 (UTC)

Read this article and come back if you have any questions. --Jayron32 00:50, 23 March 2016 (UTC)

Fascinating... I always wondered this one too. EvergreenFir (talk) Please {{re}} 06:01, 23 March 2016 (UTC)

Thanks Jayron I intended to link that article too. I do think OP has a good point, and that this should be mentioned on WP, but I can't figure out where either... I almost did a quick redirect to Blood and Bone Meal, because that is what the term (mostly) means in pet food, but that would be misleading for e.g the kimchi claim, where the crude ash I think must come from traces of plant minerals and the fish. SemanticMantis (talk) 14:15, 23 March 2016 (UTC)

I think you can redirect the link to mineral nutrient, because that's what ash is. --Jayron32 18:37, 23 March 2016 (UTC)

Good call, I made the redirect and put an (unreferenced) sentence in near the top; a mild overall improvement IMO. Thanks to OP for bringing this up. SemanticMantis (talk) 20:15, 23 March 2016 (UTC)

uranium or plutonium in nuclear weapons

I had a read through a lot of very nice articles. And it feels like am now capable to built operate and recycle a pit myself. But the thing which is missing is: How many of the US or Russian nuclear pits now in "use" are made from uranium and how many are plutonium ones? The W88 states in a drawing it has a plutonium pit, while the article on B61 nuclear bomb does not give the information. For the Russian nukes it is even more complicated but the Megatons to Megawatts Program makes it clear that they use a lot of uranium which is later used in US nuclear power plants. (Us do not use MOX so it must be uranium). I doubt that you can plug a U-pit into a B61 and after a few years rip it out and plug a Pu-pit in. If this is not a crucial military secret which is also possible there should be a number somewhere.--Stone (talk) 22:34, 22 March 2016 (UTC)

I'd be very surprised if this exact info can be tracked down...most US are plutonium though...I'd be surprised if there's anyone in the govt who's even made an exact tally...seriously..68.48.241.158 (talk) 23:09, 22 March 2016 (UTC)

As the pit article you linked says, the fission pits, or "primaries", in all modern nuclear weapons are plutonium. Uranium is used, not in the "primary", but in the "secondary" of most thermonuclear weapons, for the "tamper" around the fusion fuel. When the weapon is detonated, the uranium tamper absorbs neutrons emitted from the primary and the fusion fuel and fissions. See nuclear weapon design for more details. --71.110.8.102 (talk) 00:43, 23 March 2016 (UTC)

The first place I went looking was to the website of the Federation of American Scientists - www.fas.org - specifically, to their publications and reports on weapon proliferation and fissile materials. These guys are a reliable source, in the sense that they're a bunch of science experts who are well-respected - but their data are independently researched, so take it all with a grain of salt (especially if you're in a decision-making role with respect to nuclear policy!)

Here is FAS's rundown of worldwide nuclear weapons and fissile material; here is their summary status of nuclear weapon states and their respective capabilities. They have lots of data - but it's all well-educated estimates. Chances are, some of the exact information about total weapon capabilities and compositions is highly secretive - although, maybe to a lesser extent than people might expect. A large part of Cold War détente was structured around elaborate and detailed reciprocal disclosure, and effective auditing, of the technical capabilities and stockpiles of all nuclear-weapons states. For example, see the details in our article on the historical Strategic Arms Limitation Talks, which started things rolling... and of course, the New START treaty that is active today; and you can just keep reading about progress up to the present day, such as the proposed Fissile Material Cut-off Treaty, and so on.

As an example of public disclosure: the well-known "aircraft boneyard" of the 309th Aerospace Maintenance and Regeneration Group at Davis–Monthan Air Force Base is a grand collection of American nuclear-weapons-capable aircraft, all intentionally laid out in nice rows so that Russian spy satellites can easily photograph them and count them - to ensure we've actually decommissioned the correct number of weapons platforms! There's reciprocity - American spies can inspect Russian demilitarization too, and (many of) their platforms and technologies are all thoroughly laid out in the open in accordance with treaties, so that nobody has to go to nuclear war over any cloak-and-dagger style doubts.

Heck, you can even sign up for a training course taught by the Department of Defense to learn all about nuclear weapons capabilities, and how we cooperate with (mostly) Russian scientists to ensure that everyone's capabilities are well-understood and comply with the spirit and the letter of international laws. Here's a great list of links to websites of the United States Government that may provide information of interest.

Finally, here is Nuclear Risk, the website of recent Turing Award winner (and co-inventor of public-key cryptography) Martin Hellman - who is also a board member of the Federation of American Scientists. He's got links to lots of useful stories and data pages.

Nimur (talk) 05:03, 23 March 2016 (UTC)

If you visit it, you'll also see the planes are cut in very specific ways. There are also 18 old Titan missile silo's where the concret sliding doors are half-open. It allows inspection of the silo without it looking like a launch threat or an operational silo (they use to rank cities in "first strike scenarios, Tucson was high on the list with 18 MIRV silos, and the graveyard. Not all the planes stored are destroyed strategice bomber, most are supposed to be able to be rebuilt. F-4's, F-5's F-111B are all mothballed. B-52's are cut up.). Just north in Pinal county is a CIA facility as wellas a commercial graveyard. Tiny, no tower airport lined with 747's including the NASA 747 used to move the Space Shuttle. Landed their once to see the NASA plane and was escorted away rather quickly to the little restaurant. ) --DHeyward (talk) 16:31, 23 March 2016 (UTC)

I don't think WHAT we have is particularly secretive...in fact, it's probably the exact opposite, as you suggest...but substantial aspects of how the nuke program is operated are secret, I'm quite sure..all I know is plutonium is what we largely use (exclusively use?) for our nukes....it's less expensive than using uranium (though more messy too)..of course plutonium is made from uranium, but whatever..but whether what we have is plutonium based or uranium based makes absolutely no difference to anybody, including potential adversaries, as the effect is the EXACT same... 68.48.241.158 (talk) 14:27, 23 March 2016 (UTC)

On Thermonuclear War - a famous book by Herman Kahn - addresses that point in his very first chapter: it is difficult for most ordinary people to distinguish between, say, a war that leaves 20 million dead, and a war that leaves 40 million dead - but if we depart from our emotional response and dispassionately consider these potentialities rationally, it is clear that one outcome is preferable to the other. In other words, if you subscribe to the theory of absolutist catastrophism, and pretend that all nuclear war is exactly the same... you're giving up a lot in the way of strategic planning. Nimur (talk) 15:06, 23 March 2016 (UTC)

It's more political than strategic. Ask average U.S. person which war was "worse" - Iraq, Vietnam or WWII. These are order of magnitude difference, not even just double. Compare to Rwandan genocide. Or Spanish flu to Ebola. The reality is that the political staging is more consequential. It's why people oppose nuclear energy even though rooftop solar energy will burn more houses down and kill more people. --DHeyward (talk) 16:17, 23 March 2016 (UTC)

'effect being the same' meaning a 1 megaton bomb is a 1 megaton bomb...doesn't matter if explosive force is created via plutonium or uranium..68.48.241.158 (talk) 15:14, 23 March 2016 (UTC)

Sure, if you gloss over important details like the different construction cost per unit of damage; or the different long term health effects due to variations in, say, how much Strontium-90 radioactive fallout is produced... or any of a zillion other confounding factors! Again, just because the harm is so huge as to be "unfathomable," or because some details are uncertain, does not mean that a strategic planner can never distinguish between the effects. Nimur (talk) 15:21, 23 March 2016 (UTC)

but if you're looking for something that breaks it down specifically, like 912 plutonium and 206 uranium or something...I just don't think that's discoverable and would be shocked it it could be dug up somewhere...it is of note, of course, for countries that are attempting to create nukes for the first time as far as intel...as the uranium route and the plutonium route look different etc etc..68.48.241.158 (talk) 15:05, 23 March 2016 (UTC)

Did you read through any of the links I posted? A group of expert researchers do exactly that in the first source I linked: published estimates of the military stocks of plutonium and highly enriched uranium, broken down by nation, and with pages of additional supporting details. Nimur (talk) 15:09, 23 March 2016 (UTC)

he wants a breakdown warhead by warhead, that info is not in that article...and probably nowhere to be found..68.48.241.158 (talk) 15:20, 23 March 2016 (UTC)

A little deeper reading is in order - this is a heavy subject! Status of World Nuclear Forces, which is a free online summary webpage, and cites additional publications with even more detailed breakdown. For example, Russian nuclear forces, 2015 includes your proverbial "warhead-by-warhead breakdown." From the same list of references, here is the famous "Nuclear Notebook" published by the same group of concerned atomic scientists. Nimur (talk) 15:26, 23 March 2016 (UTC)

Shedding some light on why they do it, here is Counting nuclear warheads in the public interest, (2015), a review article about the history of the Bulletin of the Atomic Scientists public disclosures of warhead estimates. Nimur (talk) 15:53, 23 March 2016 (UTC)

idk still don't see it on a quick glance...if it's there then answer his question! you may not be understanding his question, which is very specific...he wants to know how many war heads in each current arsenal derive their explosive force via plutonium or via uranium....he's not asking about size of arsenal, or a breakdown of explosive force within each arsenal...68.48.241.158 (talk) 16:08, 23 March 2016 (UTC)

Some questions aren't answerable "quickly." The data is all there, in painstaking detail, with summary tables and pages of descriptions... anybody who wishes to spend hours poring over it to recategorize it into arbitrarily-defined bins to answer an arbitrarily specific quesiton ("How many are Type A and how many are Type B") may do so. That would be an arduous and boring and ultimately fruitless task - and I'm somebody who enjoys poring over boring data sets recreationally!

Personally, I think it is more productive to simply read what the other experts have written - how they have approached the problem, how they have categorized the warheads ... but if you want to analyze and refactor their efforts - go for it! There is more public information than there is time for a volunteer enthusiast to process all of it.

If it turns out that your categorization of global weapon stockpiles into counts of "uranium pits" and "plutonium pits" is correct, valid, and useful, you can even submit it to peer-review scrutiny and publish it!

Nimur (talk) 16:23, 23 March 2016 (UTC)

it might be possible that ALL in the current US arsenal are plutonium based...idk...68.48.241.158 (talk) 16:13, 23 March 2016 (UTC)

okay just talked to somebody: pretty sure entire arsenal of US and Russia are technically "thermonuclear" devices currently..ie not atomic bombs, and it's complicated as some uranium is used in these devices for primers apparently, but the 'pit' itself for these are always plutonium based...68.48.241.158 (talk) 16:30, 23 March 2016 (UTC)

just noticed btw that 71 answered OP's question right at the beginning of the thread...pehaps why he hasn't been back...missed that post..68.48.241.158 (talk) 18:41, 23 March 2016 (UTC)

I would not be surprised if the primary not even needed to be a fission bomb, just radiation and neutron generator. The secondary can be lead. Spacing and shape and how much radiation pressure and neutron supplied seem key. An actual primary explosion would require spacing to separate sub critical components as well as spacing to allow the radiation and neutrons to spark the fusion process before primary detonated. Some early types did this though I'm not sure that procedure is still used. It would be much safer to have near-critical amounts of radioactive material and the Lithium/Hydrogen matrix encased in a non-neutron supplying medium. Our article describes the russian 50Mt bomb that used lead instead of uranium. 50Mt was half the yield of a uranium secondary but at that point, what's the need? Bring subcritical plutonium together and the heat can melt the radiation barrier (or remove it through other means). --DHeyward (talk) 19:28, 23 March 2016 (UTC)

That is awesome! I ask a question go to bed work a little on my little Mars-GC-MS and when I look here only have to pick a pdf to read. Thanks to all, especially the one IP. It sounds he would be able to go down into the basement of his workplace and count the pits himself ;-). What I wanted to do to write into the plutonium article and the uranium article a short statement like the one given here: most are Pu, U is not used in large quantities.--Stone (talk) 20:33, 23 March 2016 (UTC)

have to be careful though...if talking specifically about the "pit" in modern "thermonuclear" weapons, you're talking about plutonium....looking at the entire weapon itself, however, a significant component is enriched uranium as well...both components are used, and the way it all works together is quite complicated...too complicated for me to understand...if you're talking about more rudimentary "atomic bombs" then you can make a more clear distinction between plutonium kinds and uranium kinds...68.48.241.158 (talk) 20:51, 23 March 2016 (UTC)

Thanks again. I would only use info with reference, the two articles I what to add this are two Featured Articles so it will take some time before I add the statement that both materials are used even in the same warhead, but the pits are moste likely Pu.--Stone (talk) 21:11, 23 March 2016 (UTC)