Wikipedia:Reference desk/Archives/Science/2011 January 2

= January 2 =

Manganese(II) oxide color
Green? This does not seem to correspond with the other manganese(II) compounds' colors. --98.221.179.18 (talk) 01:05, 2 January 2011 (UTC)
 * It's not unusual for transition metal oxides to be a different colour from other compounds. The long-range ionic structure can give rise to new sets of energy levels, and so different electronic transitions (which are the basis of colour). So copper(II) oxide is not blue, for example. Physchim62 (talk) 01:55, 2 January 2011 (UTC)
 * I produced it by reacting manganese(II) sulfate with ammonia and it came out as a very light brown solid that darkened to a yellow-brown solid upon standing. --98.221.179.18 (talk) 02:09, 2 January 2011 (UTC)
 * You will have produced manganese hydroxide which oxidises in air to manganese dioxide. to make the II oxide you will have to heat manganese carbonate is an oxygen free atmosphere. Graeme Bartlett (talk) 22:47, 2 January 2011 (UTC)
 * Ho hum. I don't have an oxygen-free atmosphere. --Chemicalinterest (talk) 12:13, 3 January 2011 (UTC)

I-joist
arent I-joist s a violation of  building code? they are weaker and more prone to water damage than solid wood 2 by 12's  — Preceding unsigned comment added by Tommy35750 (talk • contribs) 01:40, 2 January 2011 (UTC)


 * Our I-joist article is silent on your question, although it states that as of 2005, approximately 50% of all wood light framed floors were framed using I-joists. So I'm guessing they are complaint with building codes. In some countries. Which country are you concerned with (as if I could not guess). Our article also says "The biggest notable difference compared to dimensional lumber is that the I-joist is designed to carry heavy loads over long distances while using less lumber than a dimensional solid wood joist of a size necessary to do the same task". That seems to suggest they are stronger, not weaker, than solid wood. You might want to point us at any source which supports your prejudices. --Tagishsimon (talk) 01:46, 2 January 2011 (UTC)

the article lies and should be changed. by definition any engineered wood is weaker than solid. i joists are basically osb which is not very strong at all. in fact i would like to know where i can report these false advertising claims as they are being told by the manufacturers. im in the usa — Preceding unsigned comment added by Tommy35750 (talk • contribs) 02:02, 2 January 2011 (UTC)


 * If you could provide a reference or two to confirm your assertion, that would help. Certainly, I cannot agree with the statement "by definition any engineered wood is weaker than solid". By whose definition? And wither plywood, for instance? --Tagishsimon (talk) 02:06, 2 January 2011 (UTC)

i am a carpenter — Preceding unsigned comment added by Tommy35750 (talk • contribs) 02:08, 2 January 2011 (UTC)


 * That's nice for you. Now, about those references. --Tagishsimon (talk) 02:10, 2 January 2011 (UTC)


 * Actually I believe that for equivalent weight/size engineered wood is stronger, not weaker. But usually what they do is reduce the weight and size, and keep the strength the same. Ariel. (talk) 02:11, 2 January 2011 (UTC)

try to punch through 2 inch solid wood and then 2 inch osb or particle wood then tell me which is stronger  — Preceding unsigned comment added by Tommy35750 (talk • contribs) 02:18, 2 January 2011 (UTC)


 * Using products in ways not specified for the product is not a good test of the product. From the Oriented strand board article, we learn that "it does have a specific axis of strength". Which implies that it is weak in other axes. So punching through board, when it is designed to be used in compression or tension about a certain axis, is a test of nothing at all. Your 2 inch solid wood is, undoubtedly, stronger in some ways than 2 inch OSB. But if that strength is never to be put to use in its application, then it is wasted. OSB's advantage is that it uses the cheapest wood inputs to provide strength where it is required, and not to provide strength where it is not required. As such, it is less expensive and weights less. And it has other advantages over your solid wood, noted in the I-joist article. --Tagishsimon (talk) 02:27, 2 January 2011 (UTC)

yes it is cheaper. but is is weaker also. in all areas. — Preceding unsigned comment added by Tommy35750 (talk • contribs) 02:29, 2 January 2011 (UTC)


 * Actually Tommy, aaah - nevermind :(  hydnjo (talk) 02:50, 2 January 2011 (UTC)


 * Please see WP:SOURCE to see what we require for "reliable sources". If you cannot provide any, there's no basis for the article to be changed. 90.193.232.239 (talk) 02:52, 2 January 2011 (UTC)


 * Weight for weight, an I-joist will be more efficient at load bearing than a solid joist, for the same reasons as an I-beam is more efficient than a solid steel beam. However, it will have a lower safety factor than a solid joist, so any rules of thumb that are used with solid joists will not necessarily apply to an I-joist. In particular, its tolerance to having holes or channels cut through it will be less than for a solid joist. Quality control during manufacturing and installation is also important. To determine whether I-joists meet your local building codes, you would need to consult a structural engineer who is familiar with those codes - that is not something on which Wikipedia editors can advise you. Gandalf61 (talk) 08:52, 2 January 2011 (UTC)
 * Some I-beams, sold in Europe, have a light metal web, rather than engineered wood. The manufacturers' and major vendors' websites usually carry data about strength. If building in the UK you would need calculations by a structural engineer, and they would take the manufacturer's data and feed it into a computer algorithm. If I-beams were unsuitable for building they would not be licensed in so many countries. Itsmejudith (talk) 11:38, 2 January 2011 (UTC)

there are a lot of new houses going up near where i live and almost all of them are being built with I-joists. they've got a basement and two floors on top of said i-joists. i've been into plenty of these houses when fully built and they all seem at least as structurally stable as my 50yo house build with 2x12 joists. purely anecdotal evidence, but if they're building with them they must comply with code ZigSaw 02:46, 4 January 2011 (UTC)

LASERs for every wave?
Is it theoretically possible to produce a LASER for every wave length? (that means, sound, IR, radio).Quest09 (talk) 11:32, 2 January 2011 (UTC)


 * Yes, although the source will have to vary for example, a GASER (Gamma Amplification by Stimulated Emission of Radiation) is of nuclear origin. A SASER is the sound analogue of a LASER. --Plasmic Physics (talk) 11:55, 2 January 2011 (UTC)


 * Also maser for microwaves.  Sp in ni ng  Spark  14:25, 2 January 2011 (UTC)

The existence of many types of 'LASERs' do not answer the question whether every wave length can be made into a LASER. Quite in contrary, the difficulties to produce a sound LASER points to the contrary direction. Quest09 (talk) 16:21, 2 January 2011 (UTC)


 * Sou can make a tunable laser that covers a range of frequencies rather than having to find a separate single-mode laser for each frequency. Be careful...sound isn't light. "Every wavelength: sound, IR, radio" is a fundamental misunderstanding of many concepts of physics (for example, the frequency of a household microwave oven is in the mid/upper frequency range of human hearing, but is a completely unrelated phenomenon. DMacks (talk) 18:30, 2 January 2011 (UTC)
 * Microwave ovens operate at much higher frequencies than those of audible sound. --Tardis (talk) 16:04, 3 January 2011 (UTC)
 * What exactly are you asking for? A wavelength is a measure of distance between two troughs or crests. Waves include, both accoustic and EMR. A LASER for all waves would be a single LASER for EMR tunable to any frequency, and a single SASER for sound. A LASER for all wavelengths would be a single LASER per wavelength range, which is what I thought was what you meant. --Plasmic Physics (talk) 00:15, 3 January 2011 (UTC)

Note that any given photon can be made to show ANY wavelength desired. You just need to get the right viewpoint (i.e. red/blue shift) so any laser beam can be measured at any wavelength, but you'll need a running start. (This is what makes photons special. It's possible to get any photon down to as close to zero energy as you like, but neutrinos and others will always have a rest mass left over and so can be gotten down as close as you like to zero speed, if not mass.) Hcobb (talk) 02:07, 3 January 2011 (UTC)

Secure flying without sexual harassment
Instead of body scanning or of frisking innocent passengers, couldn't we just put the passenger into a cabin, let air flow through it, and analyze the resulting air? If we found traces of suspicious substances, then we could selectively frisk him. It looks less intrusive than the present practice. Quest09 (talk) 11:52, 2 January 2011 (UTC)


 * That won't work with surgically implanted bombs inside bones. For all we know, Al Qa'ida could have recruited medical experts and performed surgery on volunteer suicide bombers in improvised hospitals in South Waziristan (note that Al Zawahiri is an experienced surgeon). There could be many hundreds of such suicide bombers who live normal lifes for a decade and then, one day, they all board different planes at around the same times and trigger the explosion using mobile phones. Count Iblis (talk) 13:13, 2 January 2011 (UTC)


 * Honestly, I hope you said that ironically, and that no one thinks this is a real threat. Anyway, the present practice of frisking or scanning won't catch them all, however a metal-detector will do the trick, without invading privacy. 83.40.250.126 (talk) 13:28, 2 January 2011 (UTC)


 * Well, I hope that the intelligence services have learned from the liquid explosives threat and start to think about how they would commit terror attacks if they were operating under similar constraints as Al Qa'ida and take measures to close such loopholes, instead of reacting to actual plots. There are many more security experts in the World than there are Al Qa'ida members, so this should be a successful strategy. Count Iblis (talk) 13:41, 2 January 2011 (UTC)


 * Might be that there are more security experts than terrorists, but the latter have at least some advantages: secrecy and the shear number of targets. Quest09 (talk) 15:00, 2 January 2011 (UTC)


 * The security people I know basically do nothing other than try to "think like a terrorist". They are fun people to hang out with, but a little disturbing. --Mr.98 (talk) 19:51, 2 January 2011 (UTC)


 * The current paranoia is entirely whipped up by the security community, who get their kicks (and their considerable salaries) from demonstrating that they have control over normal human beings. They are just as bad as the terrorists – in fact they do more harm to Western countries than Al-Qaeda could ever manage. They shuld be hunted down and put out of any position to do damage, IMHO. Physchim62 (talk) 14:18, 2 January 2011 (UTC)


 * The do not do more harm, unless you consider only economic harm. Quest09 (talk) 15:05, 2 January 2011 (UTC)


 * Arguably, the economic harm caused by the delays at airports and the distress caused by invasive searches is greater than the gain from the very small number of saved lives. It is very rare for the security procedures at airports to actually stop terrorist attacks. Tango (talk) 16:02, 2 January 2011 (UTC)


 * I think you're overgeneralizing a bit. There are some security think tanks and consultancies that are obviously just in it for the hype and the dollar. They get lots of nice headlines and debunking New Yorker articles and Bruce Schneier's wrath and all of that appropriate stuff. But there are also a huge number of people both inside and outside of the government who are really trying to come up with reasonable, well-studied, well-analyzed solutions for the real-world security and political scenario we live in (where losing a few thousand lives once a decade is considered to be too high a cost, even if in economic terms it doesn't amount to much). It's not an easy problem with an easy solution, and saying "it's all security theater" is easy to do when it's not your job and nobody's life depends on what you do or don't do. I used to dismiss it all as overblown before I actually met some of these people and talked to them about some of their concerns. Some are definitely more paranoid than others, but most of them are just trying to take the job seriously within the constraints that actually exist. --Mr.98 (talk) 19:51, 2 January 2011 (UTC)


 * The "military industrial complex" is not merely perpetuating a security-theater. Might I draw your attention to the FFRDCs?  These are neither "think tanks" nor "defense contractors" - they are federally funded research and development centers.  It is the job of an FFRDC to provide the government with an un-biased assessment of the technology and policy claims that are made by a "think tank" or "defense contractor."  These are federally funded non-governmental organizations that are specifically designed so that their funding is not tied to their policy or technology claims; so they can provide unbiased assessments of issues related to (typically) national security.  For a brief time, I worked at one of these agencies, as a staff engineer technical analyst, evaluating "Airborne Survivability."  Part of our job was to think about all the ways to destroy a commercial or military aircraft; and then we had to evaluate technical proposals by various major defense contractors that claimed to "reduce the risk."  Some claims were exaggerated; sometimes costs were overstated; sometimes everything was right on the money and just needed a subject-matter expert to assess the technical details.   Finally, our reports would be written up in a way that a non-technical person (like a congressman or a senator) could understand it.  It was a very stressful work environment; "paranoia" is one way to describe it.  (Down the hall were people who worked in strategic nuclear deterrence, so by comparison, our group was actually pretty relaxed; even "mass destruction" has a spectrum).  Obviously, some policy and technology proposals related to national security are bogus, money-making schemes, or media-generated hype/paranoia; but the Government is neither stupid nor gullible.  (Give some credit to the United States Federal Government - they are more stable than any other organization of that size that has ever existed).  When a technology or policy proposal is actually bogus, it is eventually outed by a lobbyist group, a government agency, or an FFRDC.  At that time, it is up to an elected official to make a policy decision to continue or discontinue funding; if you believe your elected officials are intentionally continuing to fund security theater, your best actions would be to be specific about particular projects that are being funded; then talk to your senator or congressman (there is a link at the top of both pages to help you find your Government representatives).  If you are concerned about current airport security policy, you could, for example, pressure your congressman to demand higher priority for new technology- and policy- studies related to airborne security.  Nimur (talk) 02:02, 3 January 2011 (UTC)


 * There have been such devices designed. They essentially "smell" for explosives. I'm not sure if they are actually in use in any airports, but it wouldn't surprise me if they were. They only work for explosives, though, they won't detect concealed weapons. --Tango (talk) 16:02, 2 January 2011 (UTC)


 * I'm skeptical that explosives can always be smelled, too. If proper controls were used when packing it, there should be no residue on the outside, and a properly sealed glass vial shouldn't leak any odor, either. StuRat (talk) 17:17, 2 January 2011 (UTC)


 * It's not so much "odor" as it is "tiny microscopic particles." I don't know how many parts per million these machines can detect, or the difficulty it would be to defeat them, but the general idea is, if you've been around explosives, it'll probably be on your clothes in some way; if you have a large amount of explosives on you (enough to do real damage), it'll probably be extremely hard to package them in a way that you will be confident that there will be enough leakage to defeat the machine; the amount of packaging necessary is probably enough to add bulk to whatever you are taking, which would probably draw scrutiny in and of itself. A lot of this kind of security is really just about trying to introduce enough uncertainty into the equation that a very serious group would be dissuaded that it was worth their time. Al Qaeda, for example, is actually a very risk-averse organization — they put their resources into plans they think will actually result in "successful" results, and not be P.R. coups for the "bad guys". --Mr.98 (talk) 19:47, 2 January 2011 (UTC)


 * The way to eliminate the sexual harassment aspect of airport security is to use the same system as the Israeli's use, where people trained in human behavior interview each passenger. Those that seem nervous are then given a far more intensive search than the rest.  Yes, it is possible to beat such a system, but it's more difficult to beat than the security measures in place in the US right now.  Why don't we do this ?  It's expensive. StuRat (talk) 18:10, 2 January 2011 (UTC)


 * It's also very slow. It takes long enough to get through airport security as it is. --Tango (talk) 18:22, 2 January 2011 (UTC)


 * Security measures aren't inherently slow, it's all a question of them having enough equipment and guards to do it in a timely manner. If they had enough, then the interviews would only slow people down by the length of the interview, say 5 minutes.  But, of course, having enough guards and equipment makes it quite expensive, so they usually don't, and we get incredibly long lines, as a result. StuRat (talk) 20:47, 2 January 2011 (UTC)


 * A couple of my Mom's students who were afraid of flying were pulled out of line for "a more intensive search" a few years ago for exactly this reason. (I think they were in France, not Israel.) I suspect it did not help their fear of flying one bit. APL (talk) 18:53, 2 January 2011 (UTC)


 * Puffer machines are at use at a number of major airports. They work a lot like you describe.  You step into a little booth and they blow air on you, then they suck the air back up and analyze it. Then the machine goes "Ding!" and you go through and pick up your carry-on and shoes from the x-ray conveyor belt. This usually happens after the metal detector.
 * An somewhat small airport near me has these, but not enough for all the lines. So you can choose whether you get in the two lines with a puffer, or the two lines without a puffer. I asked a guard if it wasn't pointless to have machines on only two of the lines. He said "Well, we'll catch half of them."
 * (I haven't been back in the last couple months to see if they've upgraded to body-scanners, or if they've gotten enough for all the lines.) APL (talk) 18:53, 2 January 2011 (UTC)
 * The guy hiding a bomb gets to choose whether to enter the puffer? /facepalm --
 * I suppose some people think like that. It might also be that the chances of catching a terrorist are equally high through both systems. It doesn't matter much, since the chances of a terrorist trying to blow a plane is also almost 0%.
 * That "catch half of them" statement reminds me of the film "Terminal" where a naive Tom Hanks goes to get his invalid visa stamped everyday because with only two different stamps (denied and accepted), he thinks his chance of success is 50/50. Googlemeister (talk) 15:39, 3 January 2011 (UTC)

Snow as fertiliser ?
Hello, and happy new year. I'm re-reading the Little House in the Prairie books at the moment and I came across a curious occurrence in Chapter 22 of Farmer Boy. I only have the French issue of the book so I can't give an exact quote, but basically what happens is that it's the end of fall, it snows for the first time and in the morning they find six inches or so of snow outside but the soil isn't frozen yet. Almanzo's father is very pleased, he says that snow is "the poor man's fertilizer" and it contains something that will help plants grow if you plough it into the earth. (Poor Royal has to get out in the cold with the horses and plough all the fields for his troubles.) So, is that only country lore or is there a grain of truth in that ? They're located in New York State near the Canadian border (Malone) and the story is set in 1867 so there wouldn't be many industries around sending stuff in the air, would there ? Thank you, have a nice day. 85.169.173.68 (talk) 12:28, 2 January 2011 (UTC)


 * There's a suggested explanation at http://www.weathernotebook.org/transcripts/1999/04/26.html —Preceding unsigned comment added by 86.174.166.79 (talk) 12:45, 2 January 2011 (UTC)


 * I can think of an alternate reason why crops may grow better in years with heavy snowfall. A thick blanket of snow is a good insulator (think of igloos), ensuring that the ground doesn't cool off much below the pre-snowfall temperature.  If there are things in the ground which can't stand freezing, then snow may prevent that.  Certain seeds, bulbs, and roots, lying near the surface, may be vulnerable to frost, as may worms needed to aerate the soil.  So, ground covered in snow may have a better supply of those things, and also water, in the spring, giving the crops a head start that year. StuRat (talk) 17:04, 2 January 2011 (UTC)


 * That is true, but not the answer to the question posed. The poster specifically asked about the value of snow that is ploughed into unfrozen soil; something that wouldn't be done if there were already plants or seeds present.  The original response is correct; precipitation carries with it sulfur compounds and – especially – fixed, bioavailable nitrogen that has been 'washed out' of the air: as much as 12 pounds of nitrogen per acre .  The reason to plough it in instead of waiting for it to melt in the spring is that a rapid thaw may cause much of the mineral benefit to be lost to runoff.  TenOfAllTrades(talk) 17:30, 2 January 2011 (UTC)


 * It's a reason why farmers may have thought that snow made good fertilizer, in that the crops grew better in springs that followed snowy winters. StuRat (talk) 05:54, 4 January 2011 (UTC)


 * The maximum claimed amount of nitrogen in snow (per the cited newspaper article) would be way less than a tenth of the minimum recommended nitrogen application rate. The hypothetical "poor man" would be better advised to save his effort or tractor fuel, (or extra feed for the draft animals) and not make a special plowing to plow under the "valuable" minerals in snow, amounting to 1/3 pound per acre of nitrogen. He would also avoid injury to his neighboring farmers since they won't fall down laughing at him. The snow will melt and soak into the soil, carrying into it the supposed nitrogen and sulfur. It would not run off in a filed which was not equipped with underground tile drains. The "poor farmer" would still have to fertilize the filed to get a worthwhile yield. 24.13.81.21 (talk) 22:35, 2 January 2011 (UTC)


 * Is the feed cost of draft animals significantly higher if they are plowing rather then just standing around? I mean unlike a tractor, a horse or ox needs fuel whether you are using it or not.  Googlemeister (talk) 15:32, 3 January 2011 (UTC)


 * Correct, there's a minimum amount needed to support the animals' basal metabolic rates, plus more when they are working hard. StuRat (talk) 16:05, 3 January 2011 (UTC)


 * I wonder how much of an effect it would have to mix soil with snow that then melts, so that it is full of voids and contains surplus water. Also, 1867 was fairly far into the Industrial Revolution, and before any sort of controls on pollution, and New York would be downwind - I suppose that it is plausible that some unusual substances (even iron?) might be caught this way.
 * I know that farmers sometimes are sometimes proved famously wrong (there's some recent one about methods of rice production in southeast Asia where the International Rice Research Institute reportedly showed them a better way to farm) - still, on average I would think the farmer is more likely to be right than anyone else. Wnt (talk) 17:55, 3 January 2011 (UTC)


 * Interesting discussion, thank you very much everyone ! 85.169.173.68 (talk) 19:18, 4 January 2011 (UTC)

I need a strong argument about throwing away incandescent lights to replace them with CFLs right away.
Someone I know thinks it's wasteful to throw away incandescent bulbs before they're used up, even though I know that it's more wasteful to keep using more energy when the CFLs (or even LED light bulbs) will start saving right away.

Therefore, how do I counter the argument? I once saw that incandescent bulbs were 25¢ each ($1/4-pack) at Wal-Mart, but assume they're 50¢ each.

Assuming 10¢/kWh, how long would a CFL take to save 50¢, thus justify tossing a single incandescent bulb? (How long would an LED take?)

Now, what do you think of my wish to toss out incandescent lights early in order to replace them with the CFL and LED lights? --64.216.111.57 (talk) 12:41, 2 January 2011 (UTC)


 * My CFL's take 23W and my incandescents take 100W. These figures may help. --Chemicalinterest (talk) 12:47, 2 January 2011 (UTC)


 * And using those numbers, with my electric rate (8.75¢/kWh), I'd save .65¢/hour per CFL used versus an incandescent. At that rate, it takes less than 80 hours of use to come out ahead with 50¢ CFLs.  &mdash; Lomn 14:25, 2 January 2011 (UTC)


 * The 25¢ or 50¢ cost of an incandescent bulb is actually irrelevant to the decision of whether to simply discard an incandescent bulb that has already been bought, because the cost of an already-bought bulb is a sunk cost, which should not affect financial decisions. What is important is the prospective cost of buying the CFL bulb.  A CFL bulb costs much more than an incandescent bulb, like around $1.97 per bulb at Walmart. The bulb I linked to uses 26W to replace a 100W incandescent bulb, which at Lomn's 8.75¢/kWh rate saves electricity at the rate of 0.6475¢ per hour of use.  So the $1.97 CFL bulb will pay for itself after 304 hours of use.  So to emphasize the nature of the incandescent bulb's sunk cost, even if you had an unlimited supply of free incandescent bulbs available to you, it would still be cheaper to just throw away all those wasteful incandescent bulbs, as long as you're planning on keeping your light on for at least 304 hours.  Red Act (talk) 16:19, 2 January 2011 (UTC)
 * I don't think that is quite right. You are correct that the cost of the incandescent bulb is irrelevant, since it has already been spent. What you need to do is predict how much longer the incandescent bulb would last. You then take that time divided by the lifetime of a CFL bulb and multiply it by the cost of a CFL bulb. That gives you the cost of switching early. You then work out the energy saving during the time the incandescent bulb would have lasted. If the saving is larger than the cost, it's worth switching. An incandescent bulb has a lifespan of about 1000 hours. Let's assume it's half way through its life, so has 500 hours left. A CFL bulb has a lifespan of about 10,000 hours. Therefore, the cost of replacing the bulb early is $1.97*500/10000=9.85c. The saving is 0.6475c*500=$3.24. The net gain is therefore $3.14, which is positive, so you should switch early. (Assuming the numbers other people have quoted are correct.) --Tango (talk) 17:34, 2 January 2011 (UTC)


 * A few thoughts:


 * 1) Somebody told me that the wattage figures for CFLs are greatly understated, because they omit the electricity used in the ballast. Can anyone confirm this ?  If so, what's the true wattage of CFLs ?


 * 2) There seem to be some sizes of CFL which cost about 10x more, such as those over 100 watt equivalent. So, this will alter the calculations, if you need to replace high wattage incandescents.


 * 3) Certain incandescents just can't be replaced by CFLs. CFLs have problems with cold temps (as in a garage or dog house, where the heat from the incandescent is actually used to keep it warm in winter), dimmer switches, and certain fixtures that require a "bulb" shape.  So, instead of tossing out the incandescents, perhaps the ones which are replaced with CFLs can be saved to replace those, as they burn out.


 * 4) Some incandescents have so little usage, that replacing them may not make sense. You may have one in a utility room or attic that you never enter, for example.


 * 5) The energy "wasted" by incandescents turns into heat. That heat can actually be a good thing in winter, if it provides heat where you need it (presumably you are in the room with the lights on), and thus can turn the thermostat down and cool off the rest of the house.  In summer, however, that's a bad thing.  So, replacing incandescents with CFLs in fall and winter doesn't make as much sense as in spring and summer. StuRat (talk) 16:56, 2 January 2011 (UTC)


 * Regarding StuRat's point #1, apparently this relates to a CFL's power factor. However, I'm seeing contradictory claims about the implications of this issue. Some say this power factor issue results in a CFL drawing more power than its rating ; others say this is bunk . From my cursory and inexpert look at power factor, it seems like the rated wattage correctly reflects how much energy is used and that lower power factors merely make power delivery a bit trickier. I'm sure an expert or a link to an explanation on a clearly reputable website could clear this up. --Allen (talk) 18:30, 2 January 2011 (UTC)
 * I'm not an expert, but it seems to me that the "bunk" website contains some truth and some error - especially the claim that electric motors cancel out CFLs. As far as I know, both are inductive load, and thus have voltage leading current.  It is true that the excess current is returned to the system, but the doubling of power loss in the distribution at a power factor of 0.7 means that a small amount of extra power needs to be supplied unless the factor is corrected.  Switch-mode power supplies also cause problems in the distribution system.  A larger disadvantage of CFLs (in my view) is the fact that the claimed lumen output is only about half as bright as the "equivalent" incandescent to my eyes, so I need twice as many to give the same "comfortable light".  (Perhaps my eyes are just suffering from age!)  There is also the problem that the light output falls rapidly with age.  The future is with LEDs, but I don't find the light from these very comfortable either.  I prefer a wide frequency range in the light output, but I am gradually replacing incandescent with CLF, and LED which is even more efficient.  I also envy Americans for their cheap electricity!    D b f i r s   21:19, 2 January 2011 (UTC)
 * Thanks. A google search for "CFL inductive capacitive" reveals various claims that the CFL load is "inductive", "capacitive", "inductive/capacitive" or neither inductive nor capacitive so much as harmonically distorted. I'm not sure who's right, but it seems to me that Dennis Towne's basic argument doesn't rely on his claim about cancellation. --Allen (talk) 22:45, 2 January 2011 (UTC)
 * I think the capacitor was used to correct the power factor closer to unity on early (inductive) CFLs (I cannot imagine any CFL circuitry that could possibly be capacitative in phase shift), but I agree that modern CFLs use much more complex circuitry more like that of switch-mode power supplies, so the distortion is much more complex than just a phase shift. I also agree that the total savings (including both consumer costs and supplier costs) are at least half, even taking into account all of the disadvantages, so the general argument is valid.    D b f i r s   09:23, 3 January 2011 (UTC)

SInce the heading mentions throwing away, should we be factoring in the real costs of later throwing away CFLs? HiLo48 (talk) 21:36, 2 January 2011 (UTC)


 * There seems to be a case for keeping an incandescent bulb in service rather than throwing it away and advancing the purchase date of a CFL. The CFL cost is likely to be higher than some have stated, unless a government agency is subsidizing them, or a merchant is using them as a loss leader on sale. Some consumers have told me they plan to stockpile 100 watt incandescent bulbs before their sale is outlawed in the USA at the end on 2011. The have a very, very long shelf light, and many people prefer the quality of their illumination and the lessened flicker. CFL recycling presently has a cost of 75 tents to a dollar each, which has to be paid to the recycling company by the merchant or agency accepting the CFL dud. This is often ignored in claims of the savings from switching to CFLs. It is an indirect cost, since few merchants try to make people pay the recycling cost. If they did, most consumers would just hide the dud CFLs in their trash bags. Some prices quoted are for "no name" brand CFLs, of doubtful reliability. A 100 watt equivalent GE CFL drawing 26 actual watts sells for $2.41 each, in a 6 pack from Amazon, while a GE 100 watt soft white incandescent bulb is 50 cents each in a 4 pack. Some prices quoted must include loss leader sales or governmental subsidies. An incandescent bulb can just be thrown away as trash with a massively lower cost for disposal in a landfill. The wattage figures published for CFLs are accurate, The volt amps will be larger than the watts due to the low power factor of the ballast, while an incandescent bulb has a power factor close to 1. Your electric meter records kilowatt hours, not kilovoltamp hours, so you are not charged for the extra apparent power used. A commercial client might have the power factor monitored and have to pay a penalty for a poor power factor, such as if he has large motors in use and does not have adequate power factor correction capacitors in use. A low power factor due to inductive loads (usually due to motors such as air conditioning) causes extra expense to the utility, since they have to have oversized conductors and transformers. Their recourse is to install capacitor banks at substations or on power lines. This has an indirect cost to the consumer in higher electric bills eventually when the utility files for higher rates due to higher operating expenses. 24.13.81.21 (talk) 22:23, 2 January 2011 (UTC)

Dim bulb Q
Do CFL's lose efficiency when they get dimmer with age, or does the wattage go down along with the brightness ? StuRat (talk) 22:54, 2 January 2011 (UTC)


 * The phosphors degrade over time. The result is that the wattage remains about constant but the amount of emitted light goes down.  Dragons flight (talk) 06:55, 3 January 2011 (UTC)

Can some deaf people hear what they see?
I've read that some blind people can see using their tonge. A camera sends electrical signals to nerves in the tongue and the blind person, over time, starts to see pictures. So, the brain is able to process information from one sense as if it arrived via another sense. Also, in case of hearing, visual information can strongly influence what we hear, as the McGurk effect clearly demonstrates, see also this video to check it out for yourself. It thus seems plausible to me that a lipreading deaf person could actually hear what he/she is lipreading, but I have never read about this. Count Iblis (talk) 13:28, 2 January 2011 (UTC)
 * That video is really wierd. If I look at the left image with my left eye and the right image with my right eye, I can hear both words simultaneously.  I recently read of an experiment where images were digitally processed and then "projected" on to the subjects stomach via transducers on the skin.  This was very low resolution, but apparently the subjects could form the image in their brain after a little practice just as if it had come from their eye rather than their stomach.  Sorry, I don't have a link to hand.  Sp in ni  ng  Spark  15:05, 2 January 2011 (UTC)
 * Not exactly the same thing, but you might be interested this paper also.  Sp in ni ng  Spark  15:28, 2 January 2011 (UTC)
 * See this book  Sp in ni ng  Spark  15:40, 2 January 2011 (UTC)


 * Just a few days ago there was an Oliver Sacks column in the New York Times which discusses this a bit, with a specific example of a lip reader who experiences the reading as "hearing": Lip-reading, seeing mouth movements, was immediately transformed for this patient into “hearing” the sounds of speech in her mind. Her brain was converting one mode of sensation into another. In general I suspect that Oliver Sacks books are the kind of thing you'll find interesting, if you find this kind of question interesting... he's full of very interesting and odd examples of how strange our brains can be. --Mr.98 (talk) 19:37, 2 January 2011 (UTC)


 * Possibly linked, I find that when I watch a foreign film with subtitles, I remember it as though I was hearing the characters speak the words in English, and have, however hard I try, almost no recolection of them actually talking in foreign at all, though I remember the tones of voice, the speed and accents and so on, alongside the english translations of the words. 79.74.213.144 (talk) 21:07, 3 January 2011 (UTC)

Thanks a lot everyone for the information! Count Iblis (talk) 00:06, 4 January 2011 (UTC)

What are the lines in this picture?
I'm presuming warning flares fired prior to the explosion itself? Or part of the testing process? Bobby P Chambers (talk) 15:10, 2 January 2011 (UTC)


 * According to this site, "The lines that you see in this and several other photos are vapor trails of sounding rockets. Sounding rockets or smoke flares may be launched just before a device explodes so that their vapor trails may be used to record the passage of the otherwise invisible shock wave." -- 119.31.126.66 (talk) 15:57, 2 January 2011 (UTC)


 * During the original Trinity test of the first atomic bomb, a few high speed photographs of the early explosion captured both the explosion and fireball itself, as well as cable supporting a balloon some distance behind the test. In this series of images, the cable is visible as a slightly slanted line running up the right side of each frame.  It was noted that as the shock wave from the blast passed, the highly-compressed air refracted light from the cable away from the viewer and created an illusory break in the cable.  You can see this effect in the second and third images, where it is marked with an arrow.  Note that the apparent break isn't a real effect on the cable; you can see that between frames that it has moved upwards.  From what I gather, capturing the shock wave in this way was entirely serendipitous, and deliberate smoke trails weren't introduced for this purpose in U.S. nuclear tests until several years later.  (Here's a later example which includes enlargements of the breaks or 'hooks' in the smoke trails. TenOfAllTrades(talk) 16:32, 2 January 2011 (UTC)


 * Note that you can see from this picture what is probably the "correct" viewing angle for those particular rockets. They set out a "grid" on which you can see the propagation of the shock wave. By the time of these photos, the shock wave as almost certainly already passed (it goes through in a few milliseconds, whereas the "mushroom" really starts to form after about a second). --Mr.98 (talk) 16:18, 3 January 2011 (UTC)

Strange Weakless Universe
In the Weakless Universe, how do you get a matter-antimatter imbalance? Also what does chemistry look like if the strange quark is stable? Hcobb (talk) 18:24, 2 January 2011 (UTC)


 * That is an excellent question. I've just looked at the paper proposing the Weakless Universe (linked to in our article) and it doesn't seem to address anti-matter at all. The symmetry violation of the weak interaction is only one proposed explanation for baryon asymmetry, so it's doesn't completely invalidate the idea, but I'm surprised they didn't mention it. As for strange quarks, apparently they would almost all be bound into Lambda-0 particles which could form "hyper-tritium" but would do so only rarely, so the strange quarks are not expected to interact much with anything else and would be a form dark matter. --Tango (talk) 19:56, 2 January 2011 (UTC)


 * As far as I know, the CP violation in the CKM matrix is far too small to explain the matter-antimatter imbalance. That requires unknown physics which (the authors could argue) could just as well be found in the weakless universe. -- BenRG (talk) 01:54, 3 January 2011 (UTC)

Ricocheting cannonball
Can a cannonball ricochet off the water at certain angles? And was this considered or used in 18th century naval warfare? --  T H F S W  (T · C · E) 21:59, 2 January 2011 (UTC)
 * I don't know if it was ever used deliberately, but it is certainly possible for a projectile to ricochet off water, similar to rock skipping. Shooting at water is dangerous however, and ricochets off water can be extremely unpredictable. Not that I haven't fired a gun into a puddle many times, but it is actually a really dumb thing to do. Beeblebrox (talk) 22:07, 2 January 2011 (UTC)
 * But can a large cannonball really bounce off the water right back at the shooter? --  T H F S W  (T · C · E) 22:19, 2 January 2011 (UTC)
 * No (in answer to the direct question). All of the examples given above and below require a low angle of attack, which would not provide an opportunity for the projectile to return to origin directly.  One might be able to imagine a counter-current whirlpool and path with a series of skips, but it seems completely implausible.  -- Scray (talk) 23:18, 2 January 2011 (UTC)
 * The National Park Service states that for Fort Point, San Francisco, "Plans specified that the lowest tier of artillery be as close as possible to water level so cannonballs could ricochet across the water's surface to hit enemy ships at the waterline." Clarityfiend (talk) 22:24, 2 January 2011 (UTC)
 * Preberseeschießen is a competition where you ricochet off water and than hit the target. Now only with .22 Long Rifle is used but in former times also with 8,15x46R. This seem to work. Carl Ramsauer did his phD thesis about the physics.--Stone (talk) 22:33, 2 January 2011 (UTC)
 * The OP may be interested in the Bouncing bomb, which was at over 9000 pounds, considerably heavier than even a cannonball, and was designed to skip off of the water. -- Jayron  32  22:46, 2 January 2011 (UTC)
 * The film about the bouncing bomb,The Dam Busters (film), has Barnes Wallis, the inventor stating that Nelson used the technique, pitching his cannonballs short to make them bounce up at the enemy ship near the waterline. I have seen similar claims in other, not particularly reliable, sources but no Wikipedia article seems to cover it.  Sp in ni  ng  Spark  23:42, 2 January 2011 (UTC)
 * Ricocheting is just like reflecting - it always bounces at the same angle it hit at. Since the surface of water is always horizontal, the only way it could bounce straight back at the shooter would be if you shot straight down (and it wouldn't bounce then anyway, it would just sink). --Tango (talk) 23:55, 2 January 2011 (UTC)
 * The surface of the water is only entirely horizontal if it is dead calm. Waves add an element of uncertainty to any attempt to ricochet off water. I forgot about the dam buster bomb idea of the British in WWII though. I think this is something that has been tried, but results were probably mixed at best. It would be ill-advised if there was any significant wave action, especially considering the possibility of a ricochet striking an allied ship. I say we call up the Mythbusters and have them check it out. Beeblebrox (talk) 00:01, 3 January 2011 (UTC)
 * I actually just submitted this to them, maybe they will test out next season. Beeblebrox (talk) 00:12, 3 January 2011 (UTC)
 * First-hand accounts I've read of the Battle of Trafalgar (in The Mammoth Book Of How It Happened Trafalgar edited by JE Lewis) indicate that they only fired the cannon when they got really close to the enemy ships. So I expect the range of a cannonball would not be enough to ricochet off the water at a shallow enough angle. As the ships were likely to be rolling in the waves, and as there was a delay between lighting the fuze and the cannon firing, then many cannonballs were probably inadvertently fired into the sea. But I cannot think that having a cannon ricocheting would be of any practical use, since even if it worked it would simply reduce the range of the cannon and not have any advantage over a direct hit. Perhaps in the past people would like to make a pleasing analogy with bowling in cricket. I'm not sure if they ever deliberatedly aimed their cannon under the waterline of enemy ships to make them sink, perhaps because they hoped to capture them as 'prizes' where their value would be paid to the captain and crew. I think much of the cannon shots were aimed at the rigging of the ships, in the hope of bringing the masts or sails down and immobilise them. See also Naval artillery in the Age of Sail and cannon. 92.15.31.128 (talk) 12:31, 3 January 2011 (UTC)
 * Going back to Barnes Wallis, this site debunks the idea in the film that Nelson invented the idea, but Wallis did write that "ricochet gunfire was known as early as the 16th century and was used in naval gunnery in the 17th and 18th centuries to extend the effective range".  Sp in ni ng  Spark  17:56, 3 January 2011 (UTC)


 * Although I'm not up to digging out specific quotes (because I'm somewhat ill at the moment), I recall from reading C. S. Forester's (well-researched) Hornblower novels and other Napoleonic naval warfare fiction and factual books that this low-angle ricochet technique was employed when appropriate - usually I believe at more extreme ranges when a higher angled shot would be liable to drop short or pass over the target, and when no other friendly ships were potentially in the line of fire. The main wave-induced uncertainty would be whether the shot would bounce at all (if it happened to hit the face of a wave it might not), and if so at how high an angle; the degree of lateral deflection would I think be quite small. Many British navel gunners were highly skilled and able to allow for ship movement and fuse delay, and it would often have made sense to try to inflict damage at long range when the enemy gunners lacked the expertise to retaliate in kind. 87.81.230.195 (talk) 20:35, 3 January 2011 (UTC)
 * Given how inaccurate the aiming must have been, and the rolling of the ship, then the difference in aim between a ricochet shot and one simply aimed horizontally at the enemy must have been too small to differentiate, so the horizontal shots may have ricocheted by luck, particularly when waves between the two ships would rise or fall unpredictably. Anyone who has been on an ocean like the Atlantic rather than just in the sheltered North Sea will appreciate how big the waves are and how much the ships would be rolling around and going up and down too, making deliberate attempts at ricocheting almost impossible. 92.29.114.99 (talk) 23:39, 3 January 2011 (UTC)
 * Skip bombing was done in WW2, but that's a lot different to 18thC cannonballs. 92.29.114.99 (talk) 00:10, 4 January 2011 (UTC)
 * I found a book called "A Treatise on Naval Gunnery" viewable on Google Books dated 1829 and "with the approbation and approval of the Lords Commissioners of the Admiralty", which examines every aspect of the subject. The auther presents a great mass of theoretical, experimental and anecdotal evidence on how to optimise gunnery, with sources from the Royal, US and French navies; but as far as I can see, there's no mention of bouncing cannon balls off the water. I can only conclude that if it was done, it was done very rarely and without much success. I did only scan through it so I may have missed something. Alansplodge (talk) 15:25, 5 January 2011 (UTC)
 * He discusses ricochet shooting and the conditions under which it might be effective on pages 107-108.  Sp in ni ng  Spark  17:41, 5 January 2011 (UTC)
 * Here is a more modern reference discussing it. It seems it was certainly used, but was not amongst the primary tactics.  Sp in ni ng  Spark  17:51, 5 January 2011 (UTC)
 * The earlier book says "balls will not ricochet upon water, if the angle of incidence be above three or four degrees, and if the water be not tolerably smooth", which cannot have happened very often. 92.15.1.103 (talk) 20:46, 5 January 2011 (UTC)

endocrine disruptor
if someone is exposed to a endocrine disruptor and gets effects from it, are those effects permanent or temporary. — Preceding unsigned comment added by Tommy35750 (talk • contribs) 23:30, 2 January 2011 (UTC)


 * It depends on the effects. For adults it's more likely to be temporary, but it depends on exactly what happened. BTW If you are experiencing a medical issue, then you'll need to go to a doctor, we can't diagnose you. We can mainly help with curiosity or hypothetical cases. Ariel. (talk) 02:26, 3 January 2011 (UTC)