Wikipedia:Reference desk/Archives/Science/2010 October 4

= October 4 =

SI: The Logical System?
In my chemistry textbook the SI (or metric) is referred to as the 'logical system of measurement'. But how logical is it, really? Far more than the wretched English system (or so I've been told since kindergarten), but not as logical as they could be. The different unprefixed units do not coincide: a gram is intuitively "small" whilst a litre and a metre are intuitively "middle-sized" or even "somewhat large". So my question is: when the French scientists were inventing the SI, why didn't they make 1 m3 = 1 l, which would also be 1 kg of some common substance (most likely water)? Wouldn't this be more logical? Thanks. 24.92.78.167 (talk) 00:44, 4 October 2010 (UTC)
 * A partial answer is that they were chosen to be at least within an order of magnitude to the traditional units being used in Europe at the time. For example a Liter is pretty close to both a french pint and a french litron.    I'm sure this made it a lot easier for people to adopt the new units.  (The french pint is almost double the American pint, in case you were wondering.)
 * This system was originally designed to simplify trade, not specifically science, so it was built around the needs of whatever merchants needed the most. APL (talk) 01:15, 4 October 2010 (UTC)


 * I agree with APL's answer, with the exception that the litre is not an SI unit, though it is commonly used with other SI units. -- Scray (talk) 03:48, 4 October 2010 (UTC)
 * Ah, you're right. Stupid of me. ... ... Still, it is a metric system unit. So I still feel justified in using it in a discussion about the origins of SI units.  APL (talk) 04:34, 4 October 2010 (UTC)


 * What is logical to one person is not logical to another. Consequently I think it would be impossible to contrive a system of units that would be universally considered logical.  For example, if one cubic metre was equivalent to one litre, and one litre was about the size of the present litre, the metre would be only one tenth of its present size &mdash; one new metre would be equal to the present decimetre.  This might be logical to scientists working on a small scale in laboratories, but it is unlikely to be logical to sailors and travellers who would find a day's journey measured in numbers ten times greater than the present numbers.  A man can walk ten or twenty kilometres during the course of a day's work.  He is unlikely to find it logical if he found himself walking one or two hundred kilometres in a day's work.  Dolphin  ( t ) 05:43, 4 October 2010 (UTC)
 * Only because he is accustomed to 100 km being a very large distance... Googlemeister (talk) 13:42, 4 October 2010 (UTC)


 * It's worth remembering the gram is not the SI base unit of mass. The kilogram is. This is generally accepted as an unfortunate artifact of history. For some history see (surprisingly I couldn't see much coverage of this in our articles). Nil Einne (talk) 05:55, 4 October 2010 (UTC)
 * I think the explanation for why such a small size was chosen for the gram must be that the prefixes for scaling originally ran only from milli- (1/1,000) to kilo (1,000). If the kilogram had been named the gram, there would have been no names available for any units smaller than what we actually call a gram -- and presumably these were needed even then in fields like chemistry and medicine.  --Anonymous, 06:44 UTC, October 4, 2010.
 * Our Grave (unit) article does discuss this, but perhaps some of it should be folded back into the kilogram article. CS Miller (talk) 11:27, 4 October 2010 (UTC)
 * Thanks. I thought I remembered reading something before but didn't find anything in the obvious places so decided I remembered wrong. I skimmed too vast so missed the mention of grave in kilogram. Nil Einne (talk) 13:57, 4 October 2010 (UTC)


 * I think "logical" here just refers to the ease of conversion between measures. If you want something "more logical", you can have a look at Planck units, but I doubt those are convenient for everyday use... Jørgen (talk) 07:19, 4 October 2010 (UTC)


 * Offtopic, but do people really walk 10 or 20 km during a day's work? --Chemicalinterest (talk) 11:22, 4 October 2010 (UTC)
 * I wrote A man can walk ten or twenty kilometres during the course of a day's work. Your question is off-topic.  Dolphin  ( t ) 11:25, 4 October 2010 (UTC)
 * 10-20 is easy for some professions. I used to do that much in one shift.  I used to know one woman who, if she didn't do something like 50 miles in a week, would make it up on the weekends.  She rarely had to do any "extra" walking on the weekends to get to that figure.   Additionally, some mail carriers probably do at least that.  Dismas |(talk) 11:50, 4 October 2010 (UTC)


 * The SI and the metric system in general is logical only insofar as all base units can be converted to any other by multiplying or dividing by a multiple of ten. Math becomes trivial when all you have to do it move a decimal point.  As with any system, it needs to balance its usability from a mathematical perspective, and from a practical perspective.  A measurement system isn't very useful if every measurement in it requires really huge or really tiny numbers.  There are some base metric units which suffer from this problem, the pascal is an impractically small unit of pressure, which is why we use bar or kilopascal.  Grams are impractical when weighing anything large (like, say, you), so we use kilograms in SI.  See also cgs system for details on a related system of measurement for small items.  See also Planck units for a system which is mathematically practical, in the sense that ALL of the five major universal constants are defined as "1", but which is not very usable on a daily life since it requires the units themselves to be impractically tiny.-- Jayron  32  16:13, 4 October 2010 (UTC)


 * If you are measuring in a way that requires lots of halving and doubling it would be more logical to have a base more easily halved and doubled into whole numbers than base-10. Inches (12) and yards (32) are easily to halve into simple fractions than base-10 SI units. At least, I've always found that to be the case. Somehow it seems easier to quickly grasp what 1/16th is over 0.0625. And five 16ths is obviously 5/16, while 5 * 0.0625 is... um, er... hmm. Pfly (talk) 11:25, 5 October 2010 (UTC)


 * "Wretched English system"? I think you mean wretched American system, as England has been largley metric for decades. 92.29.115.43 (talk) 18:33, 5 October 2010 (UTC)


 * But the wretched Americans inherited the wretched system from the wretched English, and give discredit where discredit is due. Edison (talk) 18:56, 5 October 2010 (UTC)
 * The Americans could have chosen to go metric decades or perhaps even centuries ago, so its their own fault. I recall some planetary probe went wrong as a result. 92.29.127.126 (talk) 19:46, 6 October 2010 (UTC)

HIV infection
Why is it that if an adult gets the saliva of an HIV infected person in his/her mouth by kissing, he/she will most likely not get infected. But if a child drinks breast milk of a mother with HIV, he/she will probably get infected. Doesn't the virus get destroyed in the stomach? —Preceding unsigned comment added by 76.169.33.234 (talk) 02:15, 4 October 2010 (UTC)
 * There are several factors involved. It is possible for a child to be infected from breast milk, but most maternal infection occurs during childbirth. In any case, the probability of a child being infected by an HIV-positive mother is only about 25%, even with natural childbirth, and cesarian section lowers that figure dramatically. Breast milk may or may not contain more virus than saliva, I don't know, but the length of exposure during breast feeding is far longer than for most kissing. The virus does get destroyed by the stomach – infection in these cases is thought to be through small wounds in the mouth. Physchim62 (talk) 02:43, 4 October 2010 (UTC)


 * (to the OP)I think you're overstating the risk from breastfeeding: 6 weeks of breastfeeding for children of HIV-positive mothers in Zimbabwe carries about 5-10% risk of infection . It is true that breastfeeding is much riskier than kissing, so it's worth discussing, as follows.


 * Saliva contains very low levels of HIV, when it's present at all: in one study on HIV levels in a variety of fluids taken from people with HIV, only about 5% of parotid saliva specimens contained detectable HIV RNA, and even when detected the mean viral load was only about 200 copies/mL fluid (estimated from figure 1). When one considers the volume of saliva exchanged, we're talking about a very small amount of virus.  If we (over-)estimate 10 mL of saliva exchange, that's about 2000 copies of HIV in the 5% of the time that it can be detected (i.e. on average, there would be close to zero per exposure).  There are quite a few papers documenting antiviral properties of saliva (e.g., , reviewed in ).  Whatever the reason,  kissing is considered not to be risky for HIV transmission if blood is not transmitted.


 * Breast milk contains much more HIV, with levels over a 6-week period in one recent study averaging 1.8 log10 (63 copies/mL).  A baby ingests about 100 mL of breast milk in a feeding, which would mean that more than 5000 copies of HIV are ingested per meal.  As that report summarizes, there are many things that are not explained about the transmission of HIV by breast milk, including the paradox that exclusive breastfeeding seems to carry a lower risk of HIV trasmission than mixed feeding (breast and bottle feeding).  It's easy to make guesses as to why this might be true, but the answer is not known.  -- Scray (talk) 03:43, 4 October 2010 (UTC)


 * So would the small chance of infection from breast milk happen because a cut in the mouth? —Preceding unsigned comment added by 76.169.33.234 (talk) 09:05, 4 October 2010 (UTC)


 * I was always under the impression that HIV cases in children were mostly caused by crossing of the virus to the baby via the placenta? I'm not sure why breast milk would be any more significant than any other fluid in carrying HIV; assuming no cut, why doesn't the virus just break down in the stomach? Regards, --— Cyclonenim | Chat 10:42, 4 October 2010 (UTC)
 * If the virus could cross the placenta, infection rates of children would be 100% (or as near as makes no difference), and you wouldn't see an advantage for cesarian sections. Physchim62 (talk) 10:46, 4 October 2010 (UTC)
 * Fair enough, as I said it was just an impression I was under. Clearly I was mistaken. I'm sure it does cross in certain cases though, right? Regards, --— Cyclonenim | Chat 12:52, 4 October 2010 (UTC)
 * Yes, HIV is listed in the "other infections" category of the TORCH complex of perinatal infections than sometimes cross the placenta, so it's not 100% sure. However, my impression was that the main route of infection was through abrasion during natural childbirth: you don't need a bleeding cut for the viraus to gain access to the bloodstream. Physchim62 (talk) 13:53, 4 October 2010 (UTC)
 * Bear in mind that the baby's digestive system is designed to allow intact proteins (antibodies) into the body as a method of passive immunity. To quote from one source, 'At birth gastric pH ranges from 6 - 8 due to residual amniotic fluid in the stomach. (Amniotic fluid is regularly swallowed during intrauterine life.) Gastric pH then falls to a pH of 1.5 to 3 within 24 to 48 hours after birth but during the first week of life returns to neutrality. Gastric pH then decreases gradually to adult values after approximately 2 years of age (range 3-7 yrs). This higher pH which normally occurs during this time is referred to as a "relative achlorhydria".'  According to  the virus does enter via the gastrointestinal tract, though the exact cell type was unknown as of 1999.  Due to a lack of inspiration on search terms I haven't tracked down the pH needed to kill HIV, aside from one curious advocate of using lemon as a contraceptive and antimicrobial, who claims lemon pH (which adults but not babies will have in the stomach) kills HIV in two minutes. Wnt (talk) 16:22, 4 October 2010 (UTC)

Pre-positioned nuclear weapons
What is the probability that small, well-hidden nuclear weapons have already been strategically pre-positioned in urban centers around the world by one or more nuclear-weapons-capable nations? Wiki Dao &#9775;  (talk)  03:26, 4 October 2010 (UTC)

Further consideration
For one of the factors in this assessment, let's say there are only five nations at present with the acknowledge-able technological capacity to easily produce enough such weapons to suit their strategic interests: US, Russia, UK, France, and China. And let's say each of these five could produce "many" should doing so indeed suit those interests. So it is coming down to how advantageous this strategy would be for at least those five nations. Does anyone have any sourced indications of how likely it is for that to be advantageous in that way...? Wiki Dao &#9775;  (talk)  19:27, 4 October 2010 (UTC)

Relevance
What real-world relevance might there be of a well-reasoned, reliable answer to this question? (Which, again, is: what is the probability that at least one nuclear-weapons capable state has already pre-placed nuclear weapons in strategic sites around the world?)

One such issue of relevance has already been mentioned: what would be the impact of the value of this probability on a cost-benefit analysis of an (expensive!) missile defense program...? Wiki Dao &#9775;  (talk)  22:48, 5 October 2010 (UTC)

What is in this picture of Mars?
In this picture of Mars, what are the things in the foreground that look like bricks? Part of the probe?? Bubba73 You talkin' to me? 04:09, 4 October 2010 (UTC)
 * Look like solar panels to me. So, yes, part of the probe.  Dismas |(talk) 04:13, 4 October 2010 (UTC)
 * Yep, see this image from the Opportunity rover article. Dismas |(talk) 04:16, 4 October 2010 (UTC)

thanks Bubba73 You talkin' to me? 04:44, 4 October 2010 (UTC)


 * Also, note that the image is distorted from its "true" shape because it is a stitched panorama. We also have a section on panorama stitch projection geometry.  Because the spacecraft's frame is at the bottom portion of the image and is in the near field of the camera, it suffers from severe geometric distortion when merged to a single panorama image.  Nimur (talk) 19:55, 4 October 2010 (UTC)

Jellyfish - bubbles in the top part
The other day I got to see some jellyfish up close. They had some air bubbles in their top part. Why is this? Do they take in some air to adjust some buoyancy? Bubba73 You talkin' to me? 05:27, 4 October 2010 (UTC)
 * Are you sure it was air? Ariel. (talk) 08:11, 4 October 2010 (UTC)


 * It sure looked like bubbles of some sort of gas. I got a good look, but I didn't have my camera. Bubba73 You talkin' to me? 14:36, 4 October 2010 (UTC)
 * I saw bubbles in a dead jellyfish on the beach, and assumed it to be outgassing from decay. --Sean 14:39, 4 October 2010 (UTC)


 * These were alive. There is a "CoastFest" here each year, and they had them.  If they have them again next year maybe I can get a photo.  Bubba73 You talkin' to me? 14:45, 4 October 2010 (UTC)
 * Here is an interesting blurb about Jellyfish Lake: "SCUBA is prohibited because the air bubbles exhaled by divers can become trapped in tissue pockets of the jellyfish, air-lifting them to and pinning them against the surface, until the trapped bubbles eventually force their way through the delicate tissue, leaving a nasty wound." --Sean 16:36, 4 October 2010 (UTC)
 * Any jellyfish on the beach comes up through the surf... Wnt (talk) 17:24, 4 October 2010 (UTC)


 * These jellyfish were captured the day before, so perhaps they were out of the air long enough to get some of it in. Still, I would like to know more.  Bubba73 You talkin' to me? 18:38, 4 October 2010 (UTC)


 * Was the jelly fish anything like the one seen in the article Portuguese Man o' War? The bubble is their for flotation. 67.78.137.62 (talk) 18:45, 4 October 2010 (UTC)


 * No, they were much smaller and didn't have the tentacles, more like File:Moon jelly - adult (rev2).jpg and File:Palau stingless jellyfish.jpg. But if that one has bubbles, then maybe these do too.  Bubba73 You talkin' to me? 18:56, 4 October 2010 (UTC)

Is toxoplasmosis a cause for discrimination?
Today for some reason I decided to invent a new kind of discrimination. According to one study, "latent" toxoplasmosis infection is associated with a 2.5-fold increased risk of traffic accidents - a bit less than the 3.2-fold increased risk for a blood alcohol level of 0.08. As detailed in the article, infection has been tentatively blamed for various psychological situations.

Now one of the most bizarre forms of discrimination in the world occurs in Japan (see Blood types in Japanese culture), where type A is dubbed "fastidious" and type B "wild" etc. Now one study put the toxoplasmosis exposure rate there in 1987 at 28% in males, 16% in females, associated with consumption of raw meat. Relevance? Well, there are reports of blood type B being associated with toxoplasmosis infection ; we also have some references to Rh negative or to a lesser degree Rh homozygous positive being more vulnerable to effects on reaction time (see Rh blood group system). So perhaps there's actually a certain grain of truth to this preposterous pseudo-science, though it's not exactly a proved point.

The meat of the matter is really, what is the ethical thing to do? The first publication talks about a million people dying in traffic accidents because of toxoplasmosis infection. Can you justify discrimination against them? Do you talk about increasing the role of treatment, if treatment helps? Is it a public health issue or a private matter? Then there is the effect on pregnancy. And despite decades of teaching that people with HIV aren't dangerous, some of them are infected with high titers of this... there's a can of worms for you. Anyway, I thought I'd throw this up for discussion and see what comes out. Wnt (talk) 07:51, 4 October 2010 (UTC)


 * In the intro at the top it says:The reference desk does not answer requests for opinions or predictions about future events. Do not start a debate; please seek an internet forum instead.--Aspro (talk) 09:32, 4 October 2010 (UTC)


 * hmmm, I was thinking of this more as an ethics question. Wnt (talk) 16:01, 4 October 2010 (UTC)


 * Fascinating tidbit on toxoplasmosis and car accidents. Is it ethical for insurance companies to charge more to insure 16 year old males than 40 year old females? Your toxo example just seems like a specific case, nothing makes it much different than discrimination based on diabetes, heart disease, etc. The public health / private concern issue interesting, but it extends to much more than just toxo status.SemanticMantis (talk) 18:47, 4 October 2010 (UTC)

Dissimilarities between cell lines and genome databases
I'm just wondering whether there is a risk, when planning genetic experiments based on information gained from genomic databases, that the sequence in your particular cell-line(s) or animal strains varies from the sequence in the database. Is it not prudent to sequence your cell-lines or animals for the region of interest first? I think it is but don't want to risk making a tit of myself by suggesting it to my supervisor if I'm wrong. --129.215.5.255 (talk) 11:09, 4 October 2010 (UTC)


 * It depends entirely on what experiment you are doing. If you are working with human cells, you should assume that your cell line of interest will not be identical to the "reference genome sequence" (which is really just a patchwork of several different individuals).  However, that may not matter at all.  If you are working with an inbred mouse strain, there may be slight differences in your particular sub-line of the inbred strain, but chances are it will be exceedingly close to the reference genome for that strain, since by definition mice from an inbred strain are homozygous at every position of the genome and identical to each other.  We might be able to give a more specific answer if we know the specifics of your experimental set-up. --- Medical geneticist (talk) 12:26, 4 October 2010 (UTC)

Disrupting a gene by inserting a marker - how to express the marker?
If you disrupt a gene by inserting another gene into it and want to use the inserted gene as a marker for the disruption of the original endogenous gene, you could try an IRES. I understand that idea reasonably well. What I don't understand quite so well is the idea of using "splice acceptor" sites, either side of the inserted gene. Would they not just lead to the splicing-out of your marker message, stopping it from being expressed as protein and rendering it useless? Or is the idea that the original gene's message is spliced out, leaving the marker's message to be translated? But this would only work if the endogenous gene had corresponding splice acceptor and donator sites, right? If the "endogenous" gene was actually a stably-inserted GFP gene, it wouldn't have any such sites, making the strategy flawed, right? 129.215.47.59 (talk) 13:45, 4 October 2010 (UTC)


 * We'd need more detail about your construct and target. From the talk of IRES and splice acceptors I assume you're describing a more or less random scheme for inserting the marker rather than a knockout by homologous recombination.  So the construct may be designed to work under a variety of contingencies, with some features unnecessary in some situations.  If it lands 5' to the coding sequence, you don't need an IRES and a 5' splice acceptor should be ignored, and translation begins with your marker.  If it lands in an exon midway in the gene, it needs stop codons and then an IRES to (partially) knock out the gene and express the marker, but it doesn't need a 5' splice acceptor.  If it lands in an intron midway in the gene, it needs a strong splice acceptor to hopefully divert the mRNA into your construct, then it needs a stop codon, then it needs an IRES.  If it lands in a 5' intron, it needs a strong splice acceptor, but the IRES isn't necessary because it's the first methionine the ribosome sees.  If I understand you right, that is... Wnt (talk) 16:41, 4 October 2010 (UTC)


 * Sorry for not specifying, but the idea was indeed to use homologous recombination, so the location of the disruption would be controlled. The target gene is GFP which was inserted earlier so there are no introns. Doesn't a splice acceptor require a splice donor to function? 178.98.12.16 (talk) 19:12, 4 October 2010 (UTC)


 * I'd assume so.... though there could easily be something I didn't think of. For example, there are genes contained entirely within other genes, and perhaps the right splice acceptor could work with a surrounding functional gene.  I have to say, I'm surprised to hear of someone going through all the trouble of a knockout in order to disrupt a GFP transgene — so surprised I could be way off base here. Wnt (talk) 02:19, 5 October 2010 (UTC)

Six volt automotive systems
Do we not have an article on the history of automotive electrical systems? I want to know why six volts used to be the standard and why things got changed to twelve. Also why the systems went from positive ground to negative. 155.42.86.171 (talk) 14:36, 4 October 2010 (UTC)
 * Nothing in car battery, starter motor, or any "auto* elec*" article:( DMacks (talk) 14:40, 4 October 2010 (UTC)


 * Our automotive battery article says: "In the past some cars had 'positive ground'. Such vehicles were found to suffer worse body corrosion and, sometimes, blocked radiators due to deposition of metal sludge.", but with no citation. I don't know about the 6V vs. 12V question. Bigger is better? --Sean 14:42, 4 October 2010 (UTC)


 * That is a bit of an oversight. Cars with 6 volt do get passing mentioned in the Jump start (vehicle).  I don't know of any cars built after the war that still had six volts but I dare say there may have been some Soviet and Asian made cars  still being built. Its asking a bit much for an electic 6 volt starter motor to turn automobile engines as they got larger in size and many budget cars did not have starter motors at all. The amount of copper needed for the leads and windings would have also added to the overall cost. Old aircraft had magnetos for energising their  ignition systems and hand swung starting only,  so there is no reason why they did not  have 6 volts as well..--Aspro (talk) 17:54, 4 October 2010 (UTC)


 * Didn't some volvos have 24-volt electrics? -- Q Chris (talk) 14:59, 4 October 2010 (UTC)


 * I suspect that in the early days of motor vehicles with small engines (by modern standards) the optimum was the 6V battery and 6V generator (or dynamo). With the progression to larger engines, the advent of diodes for current rectification and therefore use of alternators rather than generators, the optimum was a larger 12V battery (twice as many cells as a 6V) and 12V alternators and starter motors.  (Alternators are more robust than generators with their commutator systems, so alternators can turn at faster speeds than generators, producing higher output voltage without the need for more copper.)
 * The Volkswagen Beetle was manufactured with the 6V electrical system until about the early 1970s. These days, many vehicles with even larger engines, such as trucks, have 24V systems reinforcing the notion that the heavier the engine and the greater the demand for electrical services such as headlights, the more the optimum system progresses towards higher voltage.  Dolphin  ( t ) 21:54, 4 October 2010 (UTC)


 * I actually owned a 6V Volkswagen back in the 1970s. For whatever reason, it was quite easy to run down the battery, especially in cold weather, and I developed a habit of parking on hills whenever I had the chance. Looie496 (talk) 22:21, 4 October 2010 (UTC)
 * A 6 volt battery was adequate to crank the starter for a small engine and to run the headlights and taillight. A 6 volt battery was basically cheaper to manufacture because it only needed three (versus six) lead acid cells. Later batteries also had to run a fan for the heater or air conditioner and more lights, as well as a loud ghetto-blasting sound system.  Edison (talk) 01:29, 5 October 2010 (UTC)


 * A number of us have written about smaller and larger engines. I suspect that compression ratio is more significant than engine power.  Older engines operated on low-octane fuel.  They had low compression ratio engines, some even with a hand crank for manual starting when things got tough &mdash; great if there isn't a convenient hill around.  Modern engines use higher octane fuel and have higher compression ratios requiring more cranking effort to start.  Dolphin  ( t ) 01:41, 5 October 2010 (UTC)
 * Compression ratio and age wasn't the factor in the UK. Insurance and  road tax and was based on cubic capacity and rated  horse power. Therefore, cheap Fords and Morris's used 'Regular' grade for their low compression, low power engines. Mid price range cars used 'Premium' grade and little sports cars with short stroke engines,  used 'Super' grade for their higher compression. A Tourer on the other hand, might look sporty but tended to  have long stroke, mid  compression engines, so that they just ate up the miles effortlessly, hence the name, because one would buy one for touring. All cars and lorries back then, had starting handles, even Rolls Royce. Although it does gets harder as the ratio goes up, the overriding reason for introduction of electric starters in cars was for pure convenience.--Aspro (talk) 18:26, 5 October 2010 (UTC)


 * I remember the 6-volt VW. In the early 70s I was jumping one off with my 12-volt Pontiac. I didn't know about the 6V.  I clamped down the jumper cables, and smoke started coming out!  My car seemed to have electical problems after that.  Bubba73 You talkin' to me? 01:46, 5 October 2010 (UTC)

calculating odds
Scientifically, what are the odds that Apple's touch devices, like the iPhone, iPod touch, and iPad, are just hoaxes and do not exist in any working form in the supposed form factor and with the supposed method of interaction? (That any photo or video of someone using one must be computer generated, or photo/video edited, or really just taken of someone pretending to use a simple plastic prop like an actor on the set of star trek in the nineties?)93.186.31.238 (talk) 15:02, 4 October 2010 (UTC)


 * The odds are greater than 59million to 1 against for the iPhone alone. There are about 59million iPhones identified as being sold.  So, at least one person touched the iPhone and was willing to pay for it (so it must be real).  Then, you have one guy who claims (without having first-hand knowledge of the device) that it is not real.  So, the claim is that each of those 59million sales is a hoax and all of the millions of people involved in purchasing, setting up, and using the iPhone are part of the hoax.  Not only part of it, but they are spending their own money to become part of the hoax.  Further, not a single person has exposed the hoax. --  k a i n a w &trade; 15:19, 4 October 2010 (UTC)
 * There wouldn't need to be 59million plants. I doubt anyone is going around counting iPhone users. APL (talk) 15:49, 4 October 2010 (UTC)


 * You might as well assert that reality is all a dream and we're all figments of your imagination. There's no way to calculate "odds" on something like that. Either the entire world as you know it is a big lie for really no purpose other than to deceive you (because presumably everyone who owns these things has to be in on the hoax), or it's not a hoax. --Mr.98 (talk) 15:43, 4 October 2010 (UTC)


 * You could easily verify the reality of the iPhone products by walking into your local Apple store and asking if you could try one. (I've seen several of them myself, but, of course, I could be lying.)
 * Until you attempt that experiment, I'm not sure how the odds would be calculated. There's far too many unknown factors. (How much would it cost to hire large numbers of fake users, reviewers, advertising, etc? What is the purpose of the deception? How much is Apple willing to invest? How likely are other groups (Like Consumer Reports, for example) to go along with the hoax?)  There's no obvious way to calculate any of these factors.
 * In a situation like this, a scientist wouldn't really bother with probability, he would concern himself with how to make an experiment that tests the hypothesis. If the scientist goes to the Apple store and is successfully able to purchase a real working iPad, well, then the theory is disproved. Ipads are real.
 * It becomes far more interesting if the scientist goes to the apple store and it's been closed for some reason, then he drives to the next closest apple store, and that's also mysteriously closed! Now the scientist has some evidence. He doesn't have proof that Apple is a hoax, but he has a weird anomaly. He could figure out the odds that the first two stores he tests are closed by coincidence. Then he could use probability theory to determine the odds that Apple stores are intentionally being closed for some mysterious reason.
 * That's still a long way off from answering your question, of course. APL (talk) 15:49, 4 October 2010 (UTC)
 * P.S. I like to imagine that our hypothetical scientist would perform his "Going to the Apple Store to buy an iPad" experiment while wearing a lab coat and safety goggles. APL (talk) 15:52, 4 October 2010 (UTC)
 * S/he would have to complete a 14-page research ethics approval form first.Itsmejudith (talk) 16:01, 4 October 2010 (UTC)
 * Am I the only one to find the question funny given who owns the IP the OP is using? Nil Einne (talk) 16:31, 4 October 2010 (UTC)
 * HAHA! That is hilarious. APL (talk) 16:42, 4 October 2010 (UTC)

I think the concept of "odds" does not exist for this question. Odds applies to random events, an iPhone existing, or not existing is not a random event. Ariel. (talk) 19:16, 4 October 2010 (UTC)
 * According to Bayesian probability, random just means unknown. It's not as if all the probability laws wouldn't work in a chaotic but deterministic universe. As for figuring it out, I figure the most likely explanation other than those products existing is you hallucinating. I don't know what the probability of that is offhand, and there's always the chance that you just hallucinated the evidence that hallucination is rare, which wouldn't be all that unlikely if hallucination wasn't all that unlikely. — DanielLC 23:28, 4 October 2010 (UTC)
 * I believe (INAStatistician) that it's meaningless to calculate odds without some set of underlying assumptions (then you add in your defined unknowns). Given the depth of a conspiracy required to create the illusion of iP{hone,ad,od}s existing, there's not a whole lot you can rely on if they don't.  We're brains in vats overseen by reptilian humanoids which were created by HAARP?  Sure, we can throw that in.  Paul (Stansifer) 23:56, 4 October 2010 (UTC)
 * Apparently, there is maybe about a 1/3 chance of something like that being the case, Paul. Apologies for trotting this paper out again for a third time around here now, but see .  Wiki Dao  &#9775;  (talk)  02:25, 5 October 2010 (UTC)
 * I skimmed the original paper, and I didn't see the wild claim about 33% probability. However, in the summary published in New Scientist he says "...we don’t have much specific information to tell us which of the three propositions might be true. In this situation, it might be reasonable to distribute our credence roughly evenly between them.", which totally bogus.  To see why, observe that you can use this principle to convince Bostrom of any probability.  For example, if you break up the "humanity goes extinct" choice into "humanity goes extinct on a Monday", "humanity goes extinct on a Tuesday", and so on, and ask him to choose, he'll say now that there's a 7/9ths probability of humanity going extinct on some day of the week, and 1/9th for each of the other possibilities.  Which is silly, since we know it The Hitchhiker's Guide to the Galaxy.  The trouble is that you can't use probability to turn a lack of information into a number.  Paul (Stansifer) 18:56, 6 October 2010 (UTC)
 * Indeed. It is clear that the author of that paper is speculating odds, and not calculating odds. I suspect he is overly-trained in philosophical rumination and under-trained in the hard quantitative sciences.  When a chemist or physicist lays down statistical predictions, they do so for specifically controlled circumstances, not any old thing that pops into their head.  Nimur (talk) 21:08, 6 October 2010 (UTC)
 * Yes, by "1/3" I was referring to the last lines of the paper,"'In the dark forest of our current ignorance, it seems sensible to apportion one's credence roughly evenly between (1),(2), and (3).'"and then,"'Unless we are now living in a simulation, our descendants will almost certainly never run an ancestor-simulation'"which is also interesting.
 * Bostrom seems too experienced a philosopher to be easily fooled by the old "surprise test next week" trick (he's sure to have read W. V. Quine, of course;). I'll give some thought to your point when I get a chance, though, and perhaps respond more specifically.  The paper is worth considering more carefully in the meantime, though.  Wiki Dao  &#9775;  (talk)  19:39, 6 October 2010 (UTC)


 * If you're a Bayesian statistician, then you need to assign some sort of Prior probability before you can do a study to better refine your probability. I suppose you could look at how many other, similar electronic devices have turned out to be complete hoaxes.  I'm not sure what sort of data you would collect to refine your distribution though... Maybe go to an Apple store, as APL suggested.  I Am Not A Statistition either, but it does bring up some interesting statistical points.  How is it appropriate to come up with prior probabilities?  Is it appropriate at all to try to assign prior probabilities in all cases?  These are questions that are routinely debated in the statistics departments of major universities, and while this question is trivial (in my opinion), it does provoke deeper thought about the proper way to do statistics. Buddy431 (talk) 02:23, 5 October 2010 (UTC)


 * Toy shops sell toy imitation phones that look real at first sight. That means there is a finite probability that a phone that you see someone holding is a fake. The Apple devices mentioned can go wrong and not be worth repairing so there is a also a finite probability of encountering one that is no better than a hoax. Where is your proof that Star Trek is not real and just a conspiracy of actors with plastic props? Cuddlyable3 (talk) 20:28, 6 October 2010 (UTC)

Soil PH 8.3
my soil contains a ph of 8.3 .which plant is suitable to grow in my soil? —Preceding unsigned comment added by 117.254.150.111 (talk) 15:44, 4 October 2010 (UTC)
 * It contains a ph? Why don't you just remove the ph? :) 129.215.5.255 (talk) 15:47, 4 October 2010 (UTC)
 * Please don't make fun of posters' grammar. First, many posters are not native English speakers, and second, it's rude regardless. APL (talk) 15:59, 4 October 2010 (UTC)
 * Hey 129.215: There's no need to berate people for their grammar errors. To 117.254: The articles Soil pH and Alkali soils have some background.  Depending on where you live, large "home centers" or "gardening centers" like Home Depot often sell treatments to correct soil pH problems.  -- Jayron  32  16:01, 4 October 2010 (UTC)


 * It would help to know were you live. If the pH is high because you live in the desert will require different plants to if you live on chalky soil in some cold climate. 8.3 is also a bit high, could it be due to ash or some other contaminate being disposed there?--Aspro (talk) 16:20, 4 October 2010 (UTC)


 * I'll berate Jayron32's grammar by saying that berate is not the most accurate word when a little emoticon was added to the comment. --Chemicalinterest (talk) 16:51, 4 October 2010 (UTC)


 * High ph means that plants struggle to absorb essential elements such as iron, manganese, zinc and phosphorus. You are likely to get yellowing of the leaves of most plants.  Adding aluminum sulphate or peat moss or manure or just plain sulphur is often recommended to lower the ph.  Vegetables such as spinach, asparagus, carrots, cabbage and celery can tolerate ph up to 8 or so.  Meadow flowers can often cope with high ph, but I don't know of many garden plants that can cope with 8.3.  Is all of your soil such a high ph?  Has someone been dumping lime on the soil?    D b f i r s   17:00, 4 October 2010 (UTC)
 * For what it's worth, the OP's IP number geo-locates to New Delhi. Where about in India are you? Do you want native plants? Do you get bad monsoons? CS Miller (talk) 18:27, 4 October 2010 (UTC)


 * Then it is probably just something known a canker (Kanker) which frequently forms naturally in hot dry climates (well, hotter than the one I live in) which lie in a alkaline soil area. The colder Chilean potash mines might be an exception... but then again, they were laid down along time ago and they might have been nearer to the equator then. Yeah, forget I mentioned that.  Think that the inquirer would be better off seeking out a New Delhi horticultural organisation for a list of plants (herbs/flowers/food crops/fruit trees etc.) that favours local conditions. Also, green manure, dug back in,  will ferment and so  produce CO2 that will help to acidify the soil and improve its structure, enabling a greater range of  horticultural options to choose from. Our article Alkali soils has a fuller explanation. A local New Delhi organization will be able to provide much better advice that we can here, because the OP is living in a small local area of alkaline soil were he would benefit more from  local know-how.--Aspro (talk) 21:22, 4 October 2010 (UTC)

I have no reason to question the OP:s ph-value but be aware that some cheep ph-meters are rather inacurate. I has one that can be of by more than one unit. --Gr8xoz (talk) 21:40, 4 October 2010 (UTC)

Stinky refrigerator
Our small storage refrigerator broke recently and some meat inside it rotted. Now the whole thing stinks. What is the best way to deodorize the refrigerator compartment? Note: There was only meat, milk, and water jugs in the refrigerator. There was no food that needed to be saved. Thanks, Chemicalinterest (talk) 15:46, 4 October 2010 (UTC)
 * I've noticed sliced lemon used to deodorise a fridge. Otherwise, you can get a spray product that is a combination of Flash(tm) and Febreeze(tm) which might do the trick. --129.215.5.255 (talk) 15:49, 4 October 2010 (UTC)
 * Two common substances to deodorize a fridge are activated charcoal and baking soda. There are a multitude of little containers which you can hang in the fridge to get the smell out. Or, you can just spread some baking soda on a dish and see if that does the trick. It may take a few days to see if it works, depending on the severity of the stench. -- Jayron  32  15:58, 4 October 2010 (UTC)
 * (editconflict) Bicarbonate of soda is traditionally used to clean fridges and I think it could deodorise it to an extent. Itsmejudith (talk) 15:59, 4 October 2010 (UTC)


 * Check under the fridge as well (in the drain pan). It is possible that some stinkyness got in there. --  k a i n a w &trade; 16:11, 4 October 2010 (UTC)


 * Peroxide bleach for the first thorough clean. Plenty of baking soda (half a cup) and water for the next wash. Air it, to let the odours disperse. Don't expect miracles over just one night. Put a bowl of backing soda and water inside to continue to absorbers the smell. Finally get one of the charcoal fridge absorbers.--Aspro (talk) 16:14, 4 October 2010 (UTC)


 * My experience is that the metal in the fridge is quite easy to deodorize; any of the washing mechanisms noted above will work. The problems lie in the plastic bit: racks, bins and door liners. If the smell persists beyond all your best effort, you might need to replace these elements. Bielle  (talk) 16:21, 4 October 2010 (UTC)


 * I used hypochlorite bleach and will see whether that works. We did drain the drainpan. It is mostly plastic. Thanks for the suggestions. --Chemicalinterest (talk) 16:50, 4 October 2010 (UTC)


 * There was a similar question here: Reference desk/Archives/Science/2010 June 28. Ariel. (talk) 20:05, 4 October 2010 (UTC)


 * Vanilla essence has worked for me in the past. There are even commercially available products containing it if you want to spend the money, but raiding your pantry is cheaper. Just put some on a damp cloth and wipe all the surfaces.  Certainly a lot more food friendly than hypochlorite!  Matto  paedia  Say G'Day!  10:36, 5 October 2010 (UTC)

Storing Cr2032 Batteries
I have a bunch of lithium cr2032 Button cell batteries for a project, they are in packaging that is overly secure, a pain in the ass to get open, and then not at all secure once opened. I want to repackage them so that they are easier to access. My worry is that I should not dump them all into a tupperware container or a plastic bag, as they might overheat when the terminals are touching in a big group. Is this a valid fear? Any ideas on an easy way to keep 300 of them separate? Beach drifter (talk) 18:34, 4 October 2010 (UTC)


 * Just curious. What use do you have for 300 Cr2032 batteries.(I just use a good pair of beefy scissors)--Aspro (talk) 18:48, 4 October 2010 (UTC)
 * This + This. Beach drifter (talk) 19:03, 4 October 2010 (UTC)
 * Parafilm? Wnt (talk) 18:49, 4 October 2010 (UTC)

Yes it's a valid fear. Take a long piece of tape and stick each one on it. Stick it negative side (the "inner" metal side) down. I would use packing tape and do two rows. Regular scotch tape will probably not be strong enough. Ariel. (talk) 19:22, 4 October 2010 (UTC)


 * I would take a long sheet of plastic wrap. Cover one half of it with batteries, leaving about 1/4 inch of space between each battery. Fold the other half of plastic wrap over the batteries. Fold up the sandwich and shove it in a box. --Chemicalinterest (talk) 20:08, 4 October 2010 (UTC)

DO NOT stack them in a tube or a similar configuration without insulating spacers. This was my first idea that pooped up in my head but the next second I realized that the voltage end to end would be 900V!!! --Gr8xoz (talk) 20:47, 4 October 2010 (UTC)


 * Yes, that would be so much voltage, although the stack will be 96 cm long. Did you know the first two numbers on a battery indicate its diameter in mm. So CR2032 are 20 mm. The 32 stands for how many 1/10mm it is thick. So it is 3.2 mm thick. --Chemicalinterest (talk) 23:05, 4 October 2010 (UTC)
 * Interesting. What does "CR" stand for? 92.29.115.43 (talk) 18:58, 5 October 2010 (UTC)
 * From CR2032 battery: C means that it is a lithium electrode and R that it is round. Beach drifter (talk) 19:25, 5 October 2010 (UTC)
 * Stack them in a plastic tube with the bottom end sealed. Or to be fancy, stack them in a plastic tube with the top end sealed and a little trapdoor at the bottom to use as a dispenser. Cuddlyable3 (talk) 20:00, 6 October 2010 (UTC)

Passage of Time
If the earth's velocity through space is not constant then doesn't that imply that time as we perceive it is not consistent throughout our lifetime? Or if the earth increases (via radiation from the sun and meteorites) or decreases (via sending probes and satellites into space) in mass then doesn't that also affect how we perceive time? So one minute when I was 3 could vary in length from one minute when I was 25? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:55, 4 October 2010 (UTC)
 * How would you know? You can only measure time by comparing to something else. But yes, if mass changes, time does too. Speed does it too, but in a more complicated way. Ariel. (talk) 20:06, 4 October 2010 (UTC)


 * No, a minute is by definition a unit of time so, by definition, two minute long events have the same duration regardless to where in the universe you happen to be. 67.78.137.62 (talk) 20:07, 4 October 2010 (UTC)
 * I do not think it is that simple, there are two aspects of this:


 * Previously seconds and minutes was defined in terms of the rotation and orbit of earth, depending on the timescale used compensations for this is still introduced, e.g. leap seconds (61 s in some minutes).


 * Relativistic effects, if the earth change speed or mass the time on earth will get an other “speed” relative to the rest of the universe. The local “length” of one minute on earth is still exactly the same and all processes is affected in the same way.
 * --Gr8xoz (talk) 20:40, 4 October 2010 (UTC)

Time is relative. —Preceding unsigned comment added by 165.212.189.187 (talk) 20:18, 4 October 2010 (UTC)


 * Yes, time ir relative, but a minute is a minute is a minute. Here's an analogy: Two runers are coming down a curve on the road. The outside runner has a longer distance to go to the final line than the inside runner just because he is on the outside track. Distance is relative! And yet, a meter is still a meter. 67.78.137.62 (talk) 20:35, 4 October 2010 (UTC)
 * That is a bad analogy. A minute measured inside Earth's gravity well will not be the same duration as a minute measured outside of Earth's gravity. If you're standing next to the earthbound clock you will observe that the spacebound clock is running too fast. If you're standing floating next to the spacebound clock you will observe the earthbound clock running too slowly.
 * I am 67.78.137.62 above. I am a physics professor and know all about relative time. The problem is not with my answer, but instead with the question asked. The length of a minute doesn't get any longer or shorter. Read my analogy again and see if you understand it this time. It is quite instructive. 174.58.107.143 (talk) 04:34, 5 October 2010 (UTC)
 * I agree, it's a good (and close) analogy. The elapsed time as measured by your wristwatch (which is also the rate at which you think, age, etc.) is the length of your worldline in spacetime. If you only care about clocks that are near Earth's surface then it doesn't matter how Earth is moving relative to the rest of the universe, for the same reason that if you only care about the relative distance traveled by the runners, it doesn't matter how the track is oriented relative to the north pole or the Moon. Though Earth's motion doesn't matter, its rotation (around its own axis) does, because a helical curve is longer than a straight line pointing in the same direction. Gravitational effects can be included in the analogy too. If you imagine that the race course is extremely long and both tracks run east-west, the runner farther from the equator will have less distance to travel; that's (closely) analogous to gravitational time dilation. Furthermore, if the runners ignore the tracks and run in a straight line (great circle), they will veer toward the equator. That's analogous to the gravitational force. -- BenRG (talk) 07:27, 5 October 2010 (UTC)
 * Similarly, if you were floating in space watching clocks on earth, you would observe that time is running slower on Earth now than it did twenty-two years ago. (That is to say that the minutes appear longer.) This is because the Earth has gotten heavier.
 * (For those of us stuck here on Earth for the whole time, there is no observable change, because we slow down just as much as our clocks do.
 * All of these effects are incredibly tiny because the Earth just isn't heavy enough to cause really dramatic time dilation.
 * Here is an article Gravitational_time_dilation. APL (talk) 20:44, 4 October 2010 (UTC)
 * Another thing to check out: Twin paradox. --- cymru lass (hit me up)⁄(background check) 23:46, 4 October 2010 (UTC)
 * The difference in the passage of time between years is too small to be of any effect with current measuring technology. On the other hand, the change in "clock speed" over any given year is significant: basically, if you think of someone floating in space way above the Solar System and observing clocks on Earth then, to the space observer, Earth clocks run slowest in January and fastest in June. This is because the Earth is closest to the Sun, and moving fastest along its orbit, in January. Physchim62 (talk) 02:04, 5 October 2010 (UTC)

How fast would you have to be going to get to Jupiter in a year?
Let's say Jupiter is right above, like, you can fly directly at it, so it will take you one year to get there. How fast would you have to go to get there? In miles per hour, preferably. Thank you!-- Editor510  drop us a line, mate  20:46, 4 October 2010 (UTC)
 * I assume that you're postulating that Jupiter and Earth are in alignment relative to the Sun, so that the distance between the two is the difference between the average orbital radii, and that you're looking for an average speed? If so, the orbital information may be found at Jupiter and Earth (semi-major axis is what you want), and you can do the math from there.  Acroterion  (talk)  20:53, 4 October 2010 (UTC)
 * I got roughly 20km/sec, which is roughly equal to 45,000 mph. I could not tell you when the window for that trip would be though.  Googlemeister (talk) 20:56, 4 October 2010 (UTC)
 * It's a bit trickier than that, since Jupiter is moving, so you need to aim for where it is going to be in one year, and arrive at that time. Aiming for the average distance from the sun between Jupiter and Earth is meaningless, since, depending on the time of year for each planet, you could be off by a factor of two or more.  You need to know a) what day you plan to leave Earth and b) where Jupiter will be when you get there.  Simply aiming for Jupiter's orbit means that you may sit around and wait for several years before Jupiter comes by and picks you up, a very inefficient way of doing it.  It would probably take a bit of calculus (simple calculus, but calculus none the less) to calculate the travel time between two co-moving bodies.  -- Jayron  32  20:59, 4 October 2010 (UTC)
 * Oh no, it's for a hard science fiction story, so, I think Googlemeister's answer handles everything. -- Editor510  drop us a line, mate  21:01, 4 October 2010 (UTC)
 * If it is a true hard science fiction story i think you want a more realistic mission profile, to travel in a straight line at constant speed is ridiculously inefficient since you will need to compensate for the suns gravity, and the speed of the earth and then you need to match the speed of Jupiter. A god place to get this type of info is, in this case the sub-pages and  are relevant. --Gr8xoz (talk) 21:29, 4 October 2010 (UTC)
 * For hard hard SF, see Hohmann transfer orbit. --Stephan Schulz (talk) 21:36, 4 October 2010 (UTC)
 * And consider whether your space-program would prefer a Hohmann orbit, or a minimum energy transfer orbit, or some other orbit profile. The most practical orbit is an engineering tradeoff; it has to do with how long you want to provide life support; how much radiation shielding you want to provide for the astronauts; whether you can afford to put a lot of mass into low-earth-orbit; how the mass (i.e., fuel) is expended throughout the orbit profile. For example, if you want to reach Jupiter in a hurry, you arrive at the planet traveling very fast.  Then you must spend a lot of fuel to slow down ("capture").  So this means you have to carry a lot of fuel with you, i.e. a larger spacecraft - which exponentially increases the mass you had to take to low-earth orbit.  On the other hand, you can design a "direct descent" orbit scheduled to arrive at Jupiter with zero velocity relative to the planet; but it will take dramatically longer to arrive, and your engineering burden is much harder (because you have fewer opportunities for trajectory correction maneuvers if you aren't carrying fuel with you).  Such engineering tradeoffs are easy to work out in science fiction, because you don't have to worry about a budget.  Nimur (talk) 22:30, 4 October 2010 (UTC)
 * (5-1)AU * 93e6 miles/AU / 365.24 days/year / 24 hours/day = 42 438 miles/hour, AU is the Astronomical Unit, the distance from sun to earth, Jupiter is as closest 5 AU from the sun. This asumes that you move in a stright line and time it so you arive at the same time as jupiter. ofcurse this is not a realistic way to travle to jupiter. —Preceding unsigned comment added by Gr8xoz (talk • contribs) 21:04, 4 October 2010 (UTC)
 * Thank you, but, as you can see, I posted a meaning I got the answer I wanted. No mission profile is needed, but I appreciate the help. :)-- Editor510   drop us a line, mate  21:38, 4 October 2010 (UTC)
 * The OP doesn't specify whether you need to arrive at Jupiter alive or squashed. Check this information about g-force before planning your trip. Cuddlyable3 (talk) 19:49, 6 October 2010 (UTC)
 * Not an issue. He could accelerate to (and from) 42,438mph in just over half an hour at 1g acceleration.  APL (talk) 21:09, 6 October 2010 (UTC)