Can hypnosis aid in recovery of the memories lost to a blackout drunk? What I've read suggests that they're never properly stored, thus leaving nothing to recall in the first place, but has anyone compared the accuracy of recovered memory to impartial evidence (recordings, etc.)? And if so, what did they find? [[Special:Contributions/71.248.115.187|71.248.115.187]] ([[User talk:71.248.115.187|talk]]) 00:29, 14 October 2012 (UTC)
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I'm looking at different solar panels and I'm really confused. How much power would a 20 watt panel product? Is it enough to run lets say a fan? or a laptop or light bulb?
If I were to hook it up to a used car battery to store the electricity produced, what equipment would I need to lets say charge my phone with the car battery without damaging the phone [by giving it too much electricity, or for to long (overcharging)].
Any help and/or links would be greatly appreciated :-) — Preceding unsigned comment added by 76.87.48.246 (talk) 04:44, 4 October 2012 (UTC)[reply]
20 watts is very little. It could power a CFL bulb equivalent to a 75 watt incandescent light. It probably wouldn't be worth trying to store that little energy. And note that you will get less than 20 watts if it's at an angle to the sunlight, it's overcast, the panel is dusty, or it's old. StuRat (talk) 05:06, 4 October 2012 (UTC)[reply]
Do please confirm that 20 Watts is a rate and not an amount of energy. μηδείς (talk) 05:16, 4 October 2012 (UTC)[reply]
For the purposes of this discussion, the distinction is unimportant (it only becomes important when talking about storing the electricity generated by the panel, and that isn't practical with such a small panel). StuRat (talk) 05:20, 4 October 2012 (UTC)[reply]
The site says:
LiteFuzeLiteFuze 20W Mono-crystalline Solar Panel 20 Watt - High-Efficiency
Maximum Series Fuse 2AbrCells 36 units 125x125 monocrystalline siliconbrNOCT 48 /-2 CbrOperating Temperature -40 C to 85 CbrMax. System Operating Voltage 1000V DCbrCE, CSA, DVE, IEC Certified
So in other words, these portable and small panels are kind of useless except to maybe charge a cell phone?
That sounds like it's 20 watts per cell. 20 watts times 36 units is 720 watts, which is a more useful amount. Can you provide a link to the site, so I can confirm this ? StuRat (talk) 05:26, 4 October 2012 (UTC)[reply]
Unfortunately, that looks like it really is just one 20 watt panel. StuRat (talk) 05:34, 4 October 2012 (UTC)[reply]
Thanks for helping me out :-) — Preceding unsigned comment added by 76.87.48.246 (talk) 05:37, 4 October 2012 (UTC)[reply]
I know my biggest TV (42" plasma) can use 1Kw, my oven uses 2Kw, I've a 20 or so inch lcd monitor that uses up to 54 watts. It can be hard to figure out the wattage of an appliance because it is often written on the retail packaging, but not on the product itself. Maybe like 400 watt rated panels in top sunlight to run a laptop without batteres? Maybe 500, and even more if it is an extreme gaming rig. I am guaging that by what a desktop computer might use, 300 watts or more PSU, 50 watts or more monitor, speakers, router. It wouldn't use 400 watts all the time, but if it wants to run the dvd and hard drive at the same time for a second, it will need the full power available or it will fizzle out or at least not work. My kettle says underneath that it uses between 2520 and 3000 watts which makes it the most power hungry device here. ~ R.T.G 10:56, 4 October 2012 (UTC)[reply]
Laptops are easy to judge - just see what the power supply is rated for. Mine is 90W. I doubt there is anything outside of netbooks that can run off of a 20W panel. One of the Amazon reviews is from somebody using it to run a few small PC fans for greenhouse exhaust. I think that is probably the sort of application this is designed for - running a small load somewhere without easy power access. The greenhouse is perfect because the fans don't need to run as strong or at all when the greenhouse and panel aren't in full sun. 209.131.76.183 (talk) 13:25, 4 October 2012 (UTC)[reply]
Laptop power supply are meant to charge the battery at a reasonable rate (as fast as possible without causing to much heating of the battery. Looking at a random laptop (HP ProBook), it has a 55Wh battery for a maximum battery life of 8.5 hours. Taking a more realistic value of 5.5 hours, it would consume 10W average.
The only problem is whether the battery charging circuity will accept a lower supply current than the 65W adapter it comes with. But when using an old car battery as storage, that doesn't matter, these can supply kilowatts and accept any charge rate. Problem with car batteries is that they aren't meant for deep discharging, they are designed specifically for high peak currents (driving the starter motor). That means they're made with many thin lead plates, and totally discharging them will damage those, resulting in high losses (self-discharge rate). When I left my lights on and didn't use the car for several days, I had to buy a new one, even fully charged it wouldn't start after one day.
The other problem using a car battery: say you have one of 240Ah; that's 120Ah*14V= 3.36kWh; discharge rates for them are 1% to 25% per month according to one website, take 20% as a guess for an old one, that's a loss of 0.74% per day (assuming constant discharge rate), or 25Wh per day, so you'll need more than an hour of maximum power your solar cells can provide just to keep the charge level. That's why a car battery would be too large for a 20W cell.
Also, it would take 168 hours (exactly a week) to fully charge it, or 3.5 days if you limit discharge to 50%. that's theoretical days of 24/24 maximum sunshine, not sure what a solar cell actually delivers per day, Photovoltaic system seems to suggest 5 hours of rated wattage (750W per day for 150W panel), meaning you have only 100Wh per day and the 3.5 days mentioned earlier would in fact be 3.5*24/5=16.8, say 17 days. All this assuming 100% efficiency of charging, real value would be less than 80% imo.
In any case, you'd be better of with lower capacity low loss rechargeable batteries. Low-self-discharge NiMH seems a good option, not the regular NiMH because these have a very high discharge rate (5%-20% first day, 0.5-4% /day after that). Ssscienccce (talk) 16:07, 5 October 2012 (UTC)[reply]
I'm disappointed by StuRat's dismissal of a 20W panel as not providing sufficient power to store; it's all about the applications. Sure, 20 watts isn't enough to drive major appliances, but it's a useful trickle if you're off the grid. Consider devices like this one: a portable 2.5 watt panel that can charge a couple of AA batteries – or a connected USB device – in a few hours of sun. It won't run a refrigerator, but it will give you a reading light, a charged ebook reader, a few minutes of cell-phone usage, a weather report on the radio, or a day of GPS reception when you're out in the wilderness. The usage pattern also matters; bigger batteries and smaller panels can be a reasonable combination if they're used at (for example) a remote cabin that is only used on the weekend: seven days of charging, and only two days of usage.
That said, what you can't do is directly hook a solar panel to a battery and expect good results. You'll need to build or (more likely) buy a charging controller: a device that regulates the voltage supplied to the battery for proper charging (and cuts off the power when the battery is full) and which prevents the slow discharge of the battery through the panel at night. (Some, but not all, panels are wired with a diode in line to prevent this type of discharging.) 12-volt chargers and tools can be connected to the car battery directly, but make sure that there is a suitable fuse or breaker in the line—a short circuit across a car battery can produce hellishly high currents. TenOfAllTrades(talk) 14:11, 4 October 2012 (UTC)[reply]
My point is the lack of return on investment. You are unlikely to be able to buy the solar panel, charging controller, and rechargeable batteries for less than disposable batteries would cost over the lifetime of those devices. The situation changes when the solar panels are scaled up. However, there are situations where such a small solar panel may be useful to directly use the energy produced, like the example given above of powering a ventilation fan (let's say on a shed without electricity service). StuRat (talk) 16:39, 4 October 2012 (UTC)[reply]
One would be wise not to neglect the situations where it's difficult to aquire fresh, charged batteries on a regular basis: hiking in the backwoods, staying in a remote rural cabin, living in a third-world country or war zone where deliveries are infrequent or unreliable. Sometimes it's nice to have the option of a solar charge just in case you forgot to pack batteries, or the power goes out unexpectedly.
As well, I am curious about how you calculated the return on investment in this situation. To do a back-of-the-envelope estimate, the Powerfilm device I mentioned above is selling on Amazon for $72.50 ([1]), including free shipping to the U.S. That charges two NiMH rechargeable batteries (buy four in case of cloudy spells, call that $8 all told) in four hours of sunlight. A quick survey of Amazon puts the cost of name-brand disposable alkaline AA cells at about $0.30 apiece (you'll pay more if you buy them in smaller packages at a bricks and mortar retailer, though). Assuming an average of just four hours sunlight per day, the solar charger saves $0.60 in disposable batteries per day. It pays for its entire $80 purchase price in about four months of continuous usage, or three years of summer weekends. TenOfAllTrades(talk) 20:22, 4 October 2012 (UTC)[reply]
1) That's not the device the OP asked about, which would require the additional purchase of a charging unit.
2) You listed the sale price, so let me compare with the sale price I get on disposable AA batteries, which is 8 for $1, or 12.5 cents each.
3) I don't believe rechargeable batteries hold as much of a charge as disposable batteries, especially after many discharge/recharge cycles.
4) I believe they also tend to discharge faster when sitting on the shelf.
5) The unit you linked to looks rather fragile, with folding electrical connections and such. I'd only use that in a window, which means I wouldn't get full sunlight on it most of the day (moving it from window to window might help). If you left that outside to charge for 4 hours a day for 4 months straight, I'd be very skeptical of it lasting. Also, any wind might blow it over.
6) They didn't mention angling it towards the sunlight. That doesn't look very easy to do with this device.
7) Applications which burn through 2 AA batteries a day, every day, are uncommon. Any application which does this clearly needs larger batteries. StuRat (talk) 04:54, 5 October 2012 (UTC)[reply]
Actually a decent rechargable NiMH cell, especially a LSD one, can provide more charge then disposable cell, with high drain usage patterns or when compared with zinc carbon primary cells both of which I presume is the case here given the mentioned usage patterns and prices. Cell life depends on the type, but again a decent LSD should get at least a few hundred cycles. Even LSDs do discharge faster compared to primary cells, but it isn't that fast and this seems irrelevent if we are talking about using and charging them regularly as seems to be the case here. Nil Einne (talk) 05:13, 5 October 2012 (UTC)[reply]
The batteries I use in my mouse and my camera are rechargeable AA both Duracell and Energiser. As I recall they were touted to last for 1,000 charges at least. That's like 100 bucks each battery at 12c and imagine all the chemical crap that gets flushed out when you are recycling 1,000 batteries... Anyway my batteries were like ten euros or more each for pk of 4 and I'd guesstimate I charge a pair every two days or so. I work that out to last me 8,000 days, or as they say in China, twenty odd years. I think they will be corroded into uselessness by the air before they mechanically pack in. I charge them with a Uniross charger which I believe was cheap and has been used for like 7 or 8 years and couldnt have cost more than 20 euro I think. So around 50 euros+ electricity to replace 8,000 disposeables and even if they are only half as good that's 4,000 which at 12c is about 360 euro. I doubt they'll run €300 in electricity charging and I only have to dispose of them once before starting again. 8,000 AA batteries would measure about 100cm x 30cm x 30cm which is like half a full size wheelie bin and where I live, if you only put bins out every few month's, that will cost you about half of €80 which almost covers the hardware costs to begin with. So, if it is only the electricty I am paying for vs disposeables at about 12c or 8c euro, I'd have to run 250 watts for one hour during the day to be charged 8c. The charger doesn't give wattage rating but I sincerely doubt it runs 250 watts an hour charging all four slots. In fact I know it doesn't because you can get a feel for the wattage of an appliance by the heat it gives out and I estimate a maximum 50 to 100 watts so I'd make an uneducated but careful guess that the rechargeable AAs are more like a fifth or quarter of the cost of the disposeables while the rechargeables are top brands and the disposeables are pound shop (cheapest imports, plastic toys, etc.) But you can't beat a good pound shop all the same. ~ R.T.G 13:59, 5 October 2012 (UTC)[reply]
Have you actually had any rechargeable batteries last 20 years ? I tried them, and they seemed to hold so little charge after a year or so as to be useless. That 1000 charge cycle might just mean it will hold some charge up to then, not enough to be useful. Also, time alone may make them go bad, regardless of charge cycles. StuRat (talk) 23:40, 9 October 2012 (UTC)[reply]
Tool to remove fuel filler cap?
i have bad wrist atrophy from a injury i cant get the gas cap off my car is there any tools that will help me?--Wrk678 (talk) 05:36, 4 October 2012 (UTC)[reply]
Or ask someone to help you. Astronaut (talk) 16:41, 4 October 2012 (UTC)[reply]
You might also want to replace that gas cap with one which is easier to remove. StuRat (talk) 16:44, 4 October 2012 (UTC)[reply]
Would something like one of these help you? - Karenjc 19:22, 4 October 2012 (UTC)[reply]
do they make fuels caps that are easier to open for a honda accord ?--Wrk678 (talk) 11:10, 5 October 2012 (UTC)[reply]
If you have an auto parts store such as a NAPA or Autozone nearby I recommend talking to someone there. They should have replacement gas caps, and you can see if there are any options that should be easier for you. Looking at Amazon, I don't see anything designed to be easy-open, but there several different styles, one of which may be better than the others for you. 209.131.76.183 (talk) 11:42, 5 October 2012 (UTC)[reply]
A gas cap turner, you can order them online, here for example, $15.95. quote: Many of us, especially those with Arthritis or hand injuries, will appreciate this great new tool uses leverage to twist your gas cap open easily and to tighten as well. A tip that may not help with a gas cap (or a bad wrist): when I have trouble with plastic screw caps on bottles, I wrap some double-sided sticky tape around it; gives so much grip you don't have to squeeze, only turn. Ssscienccce (talk) 11:12, 6 October 2012 (UTC)[reply]
A good idea, but I'm not sure it will fit all gas caps, and the lever arm looks too short to help much. StuRat (talk) 00:16, 7 October 2012 (UTC)[reply]
Tastes of the alkali metal halides
NaCl tastes salty. What do the other alkali metal halides (especially the chlorides) taste like? (Obviously, please ignore the more poisonous ones.) Double sharp (talk) 07:31, 4 October 2012 (UTC)[reply]
Necessary properties for an element to be a halogen
What properties (if any) would element 117 have to display for it to be counted as a halogen? Please give sources, if possible, as I need this information for the ununseptium article. Double sharp (talk) 07:33, 4 October 2012 (UTC)[reply]
Well the name suggests that it should form salts. So with an alkali metal you would get a salt. A Uus- ion should be possible. I would also expect 7 electrons in the outer shell. But if the nucleus is too short lived to have that many electrons or react to form compounds, then it is not really a halogen! Graeme Bartlett (talk) 11:08, 4 October 2012 (UTC)[reply]
The problem with these transuranic elements is that you have to make all sorts of relativistic corrections to the usual formulae. Having seven outer shell electrons is the key thing, as I understand it, but working out what the outer shell is is a little tricky - the usual patterns that make the periodic table work start to break down. --Tango (talk) 11:28, 4 October 2012 (UTC)[reply]
Would it have to be a nonmetal to be possibly a halogen? Would it have to show a −1 oxidation state (and must that be the most common oxidation state)? If a halogen must have the −1 state as its most common, Uus would probably not be able to be counted as a halogen, as it is predicted that the +1 and +3 states would be more common. (The inert pair effect would also practically reduce the octet rule to a sextet rule, as the 7s subshell is very stabilised by relativistic effects, so Uus probably can only use 5 electrons for bonding, but would still be one electron short of a full outer shell.) Double sharp (talk) 12:26, 4 October 2012 (UTC)[reply]
Concepts like "metal" and "nonmetal" also make little sense when dealing with large transuranium elements. As noted by several people above, the entire classification system we impose on the Periodic Table (for our own purposes as a heuristic means of understanding trends in properties) starts to break down with these larger elements. On a very simplistic sense, we would expect it to be "halogen-like", but less so than any other halogen; Astatine displays some quite non-Halogen properties, including observed elemental cationic oxidation states. How much less-halogen-like Uus would be is purely speculative as you'd need enough to empirically classify it, which we haven't got yet, and may never get. --Jayron32 13:38, 4 October 2012 (UTC)[reply]
Just to throw my one in there: I expect it to be a brittle, semi-conducting metalloid, with a melting point in the 500/600s, with poor halogenic properties. Plasmic Physics (talk) 21:21, 4 October 2012 (UTC)[reply]
So, what exactly are the halogenic properties? What properties are necessary for an element to be a halogen? Double sharp (talk) 07:44, 5 October 2012 (UTC)[reply]
I'd say a strong oxidant (ability to oxidise water and form an acidic solution), and a diamagnetic, singlet ground state, and of course have an affinity for the -1 state. Plasmic Physics (talk) 09:03, 5 October 2012 (UTC)[reply]
(unindent) "In the 500/600s"? I would think that with the rate of decay which Uus isotopes exhibit that it won't ever cool to a temperature range with significant chemistry (i.e. 100's or low 1000's of degrees). Not only will chemical properties break down with that many shells, but also at that high temperature.
Well, that's because we can't synthesise Uus isotopes with enough neutrons using present technology. There's a dramatic increase of half-life in the Uut isotopes when more neutrons are added. 278113 has a half-life of just 0.34 ms. But 286113 (with eight more neutrons) has a half-life of 19.6 s – 57600 times as long. (It looks like an exponential trend.) Double sharp (talk) 06:02, 9 October 2012 (UTC)[reply]
Using an NPN transistor as a switch - optimal circuit
Over the years, I've come across two circuits designed to use an NPN BJT transistor as a switch (i.e., the transistor is either off or saturated) and I'm curious as to whether or not one is superior (generally speaking).
The first type of circuit places the load and transistor in series; when the transistor is saturated, the load is connected to ground, providing a path for current and turning the load on. This circuit is ubiquitous on the internet; an example is on page 3 of this pdf.
The second type of circuit doesn't seem to be as common (at least on the internet); in its layout, the transistor and the load it controls are in parallel, so the load is off when the transistor is saturated (since, in this condition, the transistor provides a lower resistance path to ground than the load) and on when the transistor is off. An example of this type of circuit is on page 37 of this pdf.
Generally, is one of these two circuit layouts better than the other? With the second circuit, it seems possible that a small current could enter the load when the transistor is on (although in practice I imagine the load impedance would have to be quite low for this to happen), so I suppose the first circuit is more controlled in this respect.
Any thoughts on this would be appreciated. 142.20.133.132 (talk) 14:51, 4 October 2012 (UTC)[reply]
Your second citation doesn't make much sense, as there is no page 37. If you meant what's on page 2-9 Calculation of a Saturated Transistor Circuit, you have misunderstood the intent of this section; Rc is a resistance representing the load, but in accordance with analysis convention, the voltage at the collector is measured with respect to earth.
However, your question about the relative merits of series and parallel switching can still be answered. The most common case is that you want full voltage on the load when on, and zero current when off. That naturally & obviously suggests a switch in series. In the vast majority of cases, the load does not see the full voltage, as the transistor saturates with around 0.3 V accross it, but if necessary (it usually isn't) you can compensate by making the supply volage a bit bigger. The transistor isn't perfect in the off state either - a leakage current still flows. But the leakage is generally negligible in its effect on the load. Very often, the load is inductiove - it's a relay coil, a motor, etc. This presents a problem, when you turn off the current in an inductance, the magnetic energy has nowhere to go, so it creates an inductive kick voltage (known as back EMF), which can easily destroy the transistor. This can be fixed by connecting a diode in parallel with the load, or (less commonly) a resistance or RC circuit, or even just specifying a transistor with a very high voltage rating, or some combination of these methods. Using the diode will slow down the relay release to some extent.
The advantage of using the transistor in parrallel is that the back EMF issue cannot occur, as the magnetic energy is "dumped" in the transistor when the transistor turns on. The voiltage across the transistor cannot exceed the supply voltage. Parallel operation has two major disadvantages: (1) there must be a current limiting resistance in series with the transistor/load combination, and this resistance must dissipate significant power, making the circuit energy inefficient. (2), because the inductance keeps current flowing in the transistor, the relay is very slow to release. However, by using a high supply voltage and a high resistance, the relay operate time can be reduced slightly without exceeding its coil power rating.
Typical times for small relays:-
Series connection - operate 20 mS; release 25 mS; if diode used release 50 to 300 mS;
Parallel connection - operate 15 to 20 mS; release 300 to 1000 mS
Other pros and cons centre around reliability. If the diode fails to open circuit, the circuit will continue to work until the transistor has had enough of the back emf. A technician may replace the faulty transistor but forget to replace the diode. That means the system will fail gain, perhaps within hours or weeks. Correctly designed, the parallel circuit is inherently more reliable, as high transient voltages cannot occur, and there is one less semiconductor. Sometimes, the application requires the system to fail safe or start safe. Failing safe or starting safe may require the load to be energised (or not energised) whenever the power is on, but the input signal to the trasistor is not present (as say a micro-controller chip hasn't booted up yet).
Thanks for the information; that's quite a few interesting factors. I've only ever connected transistors and their controlled loads in series, so it's good to know about the benefits and disadvantages of a parallel layout. (Also, next time I'll be sure to provide both the document page number and the PDF page number when the two differ!) 142.20.133.132 (talk) 15:06, 5 October 2012 (UTC)[reply]
What constitutes a bacterial species?
If species is defined by the ability of individuals in the population that are able to reproduce with each other or amongst themselves, and species evolve over time, then what constitutes a bacterial species? Will the bacterial species keep its name or change its name when it evolves? Can a bacterial species die out? If it dies out but its genes get integrated into a different species somehow, then has a new species evolved, or the living species have evolved and the dead species is dead? 140.254.226.206 (talk) 16:19, 4 October 2012 (UTC)[reply]
A certain measure of genetic difference would be one way to distinguish between species with asexual reproduction. So, after it evolves enough, yes, it becomes a new species and gets a new name. Such species can also die out completely. If a new species evolves as the old one dies out, that situation is no different than sexually reproducing species. StuRat (talk) 16:30, 4 October 2012 (UTC)[reply]
It's probably mentioned in species problem, but I found ring species particularly fascinating when I learned about it. Vespine (talk) 00:41, 5 October 2012 (UTC)[reply]
The species problem article doesn't even discuss the most serious issue that arises with bacteria, which is that they can swap DNA with each other, including, on occasion, with types of bacteria that are quite dissimilar to them. Some biologists have argued, at least semi-seriously, that all bacteria ought to be considered as one single megaspecies. Looie496 (talk) 04:25, 5 October 2012 (UTC)[reply]
As a rule of thumb, two bacteria are generally considered to be in the same species if their 16S rRNA are at least 99% identical. Two bacteria are often in the same genus if the 16S rRNA are at least 94% identical. An official declaration of a new species / genus requires more detail than that, and not all species / genera boundaries meet those criteria, but it is a rough guide that is easy to use because 16S rRNA is universal in bacteria, highly conserved, and frequently used as a means to identify particular bacteria. Dragons flight (talk) 01:22, 5 October 2012 (UTC)[reply]
Presumably, as the SSC's designed energy level was substantially higher than the LHC's (20 TeV to 7 TeV, for protons), and the gain in energy level over Tevatron was a primary reason that the LHC was able to gather its Higgs-related data. — Lomn 18:39, 4 October 2012 (UTC)[reply]
I think they are usually just called dark dune spots (I don't really endorse the redirect to Martian geyser). There are plenty of people working on Martian dunes so you can find quite a lot of journal articles. Sean.hoyland - talk 19:18, 4 October 2012 (UTC)[reply]
Segmented sleep makes the case that before the Industrial Revolution, people would sleep in 2 phases, being awake in the middle of the night. Unfortunately, the amount of research is not overwhelming but some examples sound convincing. I'm wondering if the thesis is right. If so, I'd like to know if animals, in particular primates, also wake up during the night. Joepnl (talk) 21:39, 4 October 2012 (UTC)[reply]
A lot of animals are crepuscular, active in low light and inactive mid-day and mid-night. If I am not tired and go to bed early I sleep segmentedly. I am not a fan of it. I prefer a solid 8 hours. μηδείς (talk) 21:53, 4 October 2012 (UTC)[reply]
My gut reaction is that it is no accident that humans (and other primates) have rods that can make out the landscape by moonlight, and that in times past moonlight would have been expected to have a very direct and practical effect on behavior. I have a suspicion that things like "harvest moon" and "hunter's moon" are more than just poetic phrases, and the articles appear to support that. So I would expect people to be biologically adapted to making a fluid response to the changing lunar cycle. Doing a quick search for primates and moonlight I found [4], which looks like a useful starting point. Wnt (talk) 17:18, 5 October 2012 (UTC)[reply]
October 5
Gibbs free energy change of a hydration of a gas
The hydration energy of the gas is +8.4 kJ/mol, which gives a K of 0.0337 at 298K. How am I supposed to calculate the concentration from the partial pressure of the gas? The equilibrium constant of the hydration reaction is in units of pressure, but 0.0337 is dimensionless. — Preceding unsigned comment added by 71.207.151.227 (talk) 01:32, 5 October 2012 (UTC)[reply]
We'd need more information. The problem must have given you more data, and we'd need that to help you solve the problem. K is, to a first approximation, the ratio of partial pressures. This could be solvable with something like the total pressure. If you can tell us the entire problem, as it is written, perhaps we can help and see where you are being tripped up. --Jayron32 02:16, 5 October 2012 (UTC)[reply]
Is there a theoretical frames-per-second limit to capturing motion?
This is probably a seriously stupid question, but for some reason, it's bugging me. You know that infinity paradox thing (that's the scientific term) for walking across a room, where in order to get there, you have to cross over the halfway point, but before you do that, you have to reach half of half, but before that, you have to reach half of half of half, so forth, down to the molecular level. Obviously, we can walk across a room just fine. So at some point, there really must be some bridge between one side of the half, and the other. If that were somehow filmed with a theoretical highspeed camera, like billions to trillions—maybe more—of frames per second, would we be recording motion on a completely incomprehensible scale? See, I don't even know how to explain it. And the answer is probably just a "no". If I were to film a bullet fired at a wall at a theoretical speed, would I simply end up watching a film (projected at normal speed) of a bullet in perfect stasis for days/weeks/years? Or would we actually see something else? I want to delete this question lol. – Kerαunoςcopia◁galaxies 08:57, 5 October 2012 (UTC)[reply]
You may be interested in the planck length and planck time articles. I don't really understand the concepts myself but it seems there is a minimum length and time for everything that cannot be split into 2 smaller lengths or times. --85.119.27.27 (talk) 09:22, 5 October 2012 (UTC)[reply]
As a practical matter, in extreme slo-mo the individual frames tend to be rather dimly lit. ←Baseball BugsWhat's up, Doc?carrots→ 12:32, 5 October 2012 (UTC)[reply]
If you have eleven minutes to spare, there is a TED video here that demos a trillion frames per second camera - showing a light pulse like a regular high speed camera shows a bullet. They get around the dimming problem mentioned above by imaging the same scene many times. 88.112.36.91 (talk) 12:55, 5 October 2012 (UTC)[reply]
With conventional film, the shorter the exposure time, the more light is needed for each exposure, along with having a film that is designed for short exposure times. There are extreme high-speed cameras in use or in development for phenomena such as lightning strikes - to see how the lightning originates and how it travels. Those types of cameras use lots of individual cameras taking well-timed individual pictures. This is basically taking the Eadward Muybridge approach to an extreme. ←Baseball BugsWhat's up, Doc?carrots→ 13:07, 5 October 2012 (UTC)[reply]
More to the point than Muybridge (not very many frames per second in his original work that I've seen), see Harold Eugene Edgerton, who did amazingly creative and innovative work in high speed motion pictures, using high speed strobes to slow things down. Edison (talk) 21:37, 5 October 2012 (UTC)[reply]
Thank you guys for all the responses! Here I thought I was asking a dumb question and got some seriously cool answers. Planck length, planck time, Zeno's dichtomy paradox, and Raskar's TED talk actually answer my question! Which is, according to the planck length article, most likely unknowable—but I didn't even know that "length" had even been given a name. (As an aside, I'd previously watched two other of Raskar's videos on his "around the corner camera" and this is the first video that actually showed the results. So that was a frustration finally settled.) Thank you!! – Kerαunoςcopia◁galaxies 22:50, 5 October 2012 (UTC)[reply]
I think there is a simpler answer. Light consists of individual photons. Once your frames are so short that each frame records either zero or one photons, there is nothing to be gained by making them shorter. That might seem bizarre, but it actually comes into play in real life when recording very-low-intensity light. Looie496 (talk) 02:34, 6 October 2012 (UTC)[reply]
Sure, it's a real problem for scientific instruments recording either very fast, very small, or very dim events. So-called shot noise is the inherent noise - variation - introduced in measurements or images when you try to collect data or take pictures when you just don't have enough photons to play with. TenOfAllTrades(talk) 03:30, 6 October 2012 (UTC)[reply]
Looie496, that's a great point, although if motion is still occurring between the photons, then my question still stands, just not in regards to being visible, I suppose. The answer I really was looking for was the planck distance. But I appreciate your reply because it's completely true and I hadn't thought of it that way. (I was sort of ignoring the whole "faster fps = dimmer exposure" conversation because I didn't really mean to go in that direction. On the other hand, I had no idea about shot noise, either, so TenOfAllTrades, thanks for that point, and I promise to never be bad and close an answer ever again! :D Seriously, the last two responses may have never happened, so I definitely see everyone's point.) – Kerαunoςcopia◁galaxies 07:27, 7 October 2012 (UTC)[reply]
alcohol
is a 40% 1oz shot of wiskey stronger, the same, or less than 1 beer with 5% alcohol?, also is a "standard" shot 1 or 1 1/2 oz? if someone uses a 1 1/2 oz shot is that stronger than a beer or equivalent to it? --Wrk678 (talk) 11:08, 5 October 2012 (UTC)[reply]
Assuming that by "stronger" you mean "contains more alcohol", we'd need to know the amount of beer. Obviously 1oz of 40% abv whiskey contains as much alcohol as 8oz of 5% abv beer. (assuming the specific gravity of both is not significantly different to that of water). Rojomoke (talk) 12:22, 5 October 2012 (UTC)[reply]
Here in the UK, the smallest beer until recently was the half, which is 10oz. On that basis, even a short beer has more alcohol than a single whisky. Nowadays some pubs offer a smaller beer, a third, which is just under 7oz, and therefore would be less alcohol (at 5%) than the single whisky. However, shots here are not fluid ounces, but either 25ml (single), 40ml (large) or 50ml (double). A fluid ounce is just shy of 30ml. So - assuming a standard Scotch at 40% and a European medium-strong lager at 5% - the amounts of alcohol in order are:
Point of order: most "shots" are 1.5 ounces, as measured by the Jigger. If I got served only 1 ounce of whiskey in a neat shot, I'd think I was being shorted. --Jayron32 17:15, 5 October 2012 (UTC)[reply]
If our article is correct, you may very well often get 'shorted' in much of the US besides Utah. Nil Einne (talk) 09:53, 6 October 2012 (UTC)[reply]
i am referring to a 12 oz beer --Wrk678 (talk) 07:42, 6 October 2012 (UTC)[reply]
This is pretty basic maths, I hope you realise. As it happens, a 12 oz beer contains 17.4 ml alcohol, identical to the 1 1/2 oz whisky. AlexTiefling (talk) 10:26, 6 October 2012 (UTC)[reply]
isint 1 1/2 ounces of whiskey 40 ml, not 17.4 ml?--Wrk678 (talk) 14:49, 6 October 2012 (UTC)[reply]
Whiskey is not pure alcohol--usually under %50. μηδείς (talk) 16:56, 6 October 2012 (UTC)[reply]
Wrk678, you yourself said in your original post that you were taking the whiskey to be 40%, which is a good estimate. Indeed, many whiskies are specifically balanced at 40%. And 1 1/2 oz isn't exactly 40ml of anything - I've been using 1oz = 29ml as a close approximation, since US and UK fl oz are both close to that value, but not identical to it or each other. Thus 1 1/2 oz is approximately (29x1.5) = 43.5ml. And 40% of 43.5 is 17.4. I'm happy to help further, but please at least read what everyone here has written including yourself before asking. Thanks. AlexTiefling (talk) 07:42, 7 October 2012 (UTC)[reply]
Scurvy and scars
I was contemplating scurvy, and specifically the well-publicised symptom whereby old, long-healed wounds reopen when the sufferer is severely deficient in Vitamin C. I was trying to find out the exact mechanism whereby this happens, but without luck. I suspect it has something to do with the composition of the wound tissue - our article Scar says that scar collagen is not laid down in the "random basketweave formation ... found in normal tissue, but "forms a pronounced alignment in a single direction" and is "usually of inferior functional quality to the normal collagen randomised alignment". And I know that collagen has to be replaced regularly, and Vitamin C is essential to its formation. But how does this work in practice? Does all a sufferer's tissue deteriorate, and scars just split - or even dissolve - first because of their "inferior functional quality". Or does scar tissue need more renewal than normal tissue and thus shows signs of damage earlier? Or what? Plus, some sources mention reopening of old fractures as another scurvy symptom, but Scar suggests that bone, unlike soft tissue, heals "without any structural or functional deterioration." So do old breaks recur with scurvy, and if so, what is the mechanism? Thanks. - Karenjc 14:00, 5 October 2012 (UTC)[reply]
I found one paper about it (Disruption of healed scars in scurvy -- the result of a disequilibrium in collagen metabolism. Cohen IK, Keiser HR.; Plast Reconstr Surg. 1976 Feb;57(2):213-5.), but only the abstract is available, and pretty short:
Old scars break open in scorbutic patients because
(1) the rate of collagen degradation is greater in an old scar than it is in normal skin, and
(2) the rate of collagen synthesis is diminished throughout the body in ascorbate deficiency. Ssscienccce (talk) 20:48, 5 October 2012 (UTC)[reply]
I was able to access that paper, and ironically, it's actually a rebuttal to the theory. Well, not the theory itself, but the methods used by those who came up with it. Someguy1221 (talk) 21:03, 5 October 2012 (UTC)[reply]
This is an intriguing question. It makes me wonder, if scurvy can break apart scars entirely, is it possible to reduce them and replace them with more normal tissue? To take advantage of this, some topical compound would be desired, so I cast about for an "ascorbate antagonist" and came up with ethyl-3,4-dihydroxybutyrate, which inhibits it on prolyl hydroxylase. Turns out that if prolyl hydroxylase is inhibited, the collagen chains don't form triple helices and get degraded, and apparently this some effects on cell differentiation and morphogenesis... [5][6][7] However, I didn't find any hits for EDHB and "scar" in a quick search. Certainly collagen deposition is an end point in scarring [8], a lot of things upstream of collagen are involved in scarring, the collagen receptor DDR1 has a role in it, but I didn't yet pull out whether you can actually inhibit the scar by inhibiting the collagen e.g. by genetic means, and at least one collagen causes chronic scarring if knocked out genetically. I should look at this more, I just took one poke at the top of a very big pile of papers about this stuff. Wnt (talk) 02:44, 6 October 2012 (UTC)[reply]
Thanks, all, replies appreciated. As for the bone part of my question, Bone healing plus some other sources lead me to think that the long interval between breakage and "full repair", where remodelling has occured and lamellar bone is restored, gives a window of some years when the healed fracture is still significantly more vulnerable than the surrounding bone to collagen degradation. And if there had been inadequate immobilisation in the early weeks leading to fibrous repair, or poor nutrition during the longer window, the site could well remain more than usually vulnerable to rebreakage due to scurvy. - Karenjc 18:00, 6 October 2012 (UTC)[reply]
Holographic displays
At User_talk:Jimbo_Wales#iPhones_and_editing, our respected founder made the perfectly reasonable comment that editing Wikipedia from a phone would always be difficult due to the small size. But it makes me wonder...
If the sole required accomplishment of a computer-generated holography or other head-up display is to give you the image of a large, flat, decent resolution computer screen a foot and a half from your face, despite the fact that it's projected on some little patch near your eye, how far is that from feasibility? I see from the latter article that what (according to a sympathetic news article) sounds very similar to this is already available for what seems like a niche market of swimmers looking at their lap times.[9] So why don't phones yet have this accessory, so that the entire phone can be used as a keypad and so Wikipedia could be viewed and edited from one pretty much normally? Wnt (talk) 17:09, 5 October 2012 (UTC)[reply]
Does the Nintendo 3DS do what you're asking? If so, it is available on at least one handheld device. --Jayron32 17:13, 5 October 2012 (UTC)[reply]
One thing to note, at least for the "project it onto your eye" case, is that the image will never appear larger than the display, simply due to optics. The technology could still be used to provide a private display that is only readable by the person targeted, but it can never simulate a larger display. See Virtual retinal display. 209.131.76.183 (talk) 17:43, 5 October 2012 (UTC)[reply]
Thanks - I realize now that the reason I wasn't figuring out an answer is that my question didn't make much sense - there's no real need for a holographic technology simply to see a screen; for example you could do it with a very high res mini display and a strong contact lens. I suppose the virtual retinal display works the same way, but reverses the perspective of the focusing/scanning to minimize the equipment involved. A true hologram would allow two people to see the same apparent object, but it would inevitably be small like the "phone" then which doesn't address the main problem. Some quick scanning of the Carmack link turns up stuff around 1:12 about the display (VRD at 1:32, focus/contact lenses at 1:38, his notion of "hyperfocusing" though is bull I think, because he's neglecting the phases of the light; the comments about the Palmer kit at 1:42, $500 with distortion, the practical difficulties in head tracking, sort of explains why I don't see this on the shelf!); apparently moving the display with your head is undesirable. I suppose there's some way to measure head motions and move the projection to compensate, giving it an illusion of reality; seems like the VRD must have to do the same for eye motions because people would never put up with not being able to move their eyes to look at something. Wnt (talk) 18:21, 5 October 2012 (UTC)[reply]
I think there's also a different consideration. On my Android phone, if you use the phone in landscape, they virtual keyboard already takes up most of the screen. Typing is still very difficult compared to a real keyboard. While my phone is a fairly small one by modern standards (3.2" screen) and a large one like the 4.7" will definitely improve matters a fair amount, it will still be a lot more difficult then typing with a real keyboard for size reasons alone. The lack of tactile feedback is of course another problem (there are plans for haptic feedback or something else to try and counter the lack of tactile feedback but these still seem a while away). Even with a larger touchscreen like on an iPad this issue remains (I can say from experience). In fact some people prefer a split iPad virtual keyboard as they find it easy to type with (using thumbs). Remember also that the keyboard is fairly landscape (not including the cursors, numpad etc), hence why in most virtual keyboards are fairly landscape and when used with a phone or tablet, even a widescreen one, tend to still have space above or below (or both). And while the experience with typing with a phone or tablet isn't the same, it's similar enough that most people find it a lot easier to just stick with a layout fairly similar to the normal one at least for the letters/QWERTY. In other words, your assumption that using the entire phone as the keypad is somehow going to make things a lot easier is likely flawed, the phone is simply too small amongst other issues. (There are of course plenty of issues beyond simple typing particularly when needing to deal with markup or when needing to edit what you've already typed, And using in landscape with the keyboard active may make things worse in this regard. But I think the typing issues are enough for first consideration.) I haven't viewed any of the above links, but most sci-fi ideas tend to think of not just some sort of holographic projection or retinal display but a projected or completely virtual keyboard so you aren't limited to the size of your phone or whatever. Nil Einne (talk) 18:48, 5 October 2012 (UTC)[reply]
The keypad issue is serious, but I don't see any obvious reason why there wouldn't be a way to change the shape of the surface enough to provide tactile feedback, even on a dynamic basis. (I'd think someone should come up with a decent "display monitor" for the blind, at which point it could be adapted... off the top of my head, I think of either small projecting pins or else microfluidics and ampullae) More fundamentally, I would think someone should have invented a combinatorial alternative to QWERTY already. Suppose five fingers each hand (no thumb semantics...), so pressing any two fingers gets you one of 25 letters. Pressing any four fingers from a well chosen subset should provide all the extra letters with minimal risk of missed letters. Of course, this implies that the software can tell which finger is which, a creepy notion - one of those perennial questions I've been meaning to ask here is if anyone ever caught Synaptics uploading fingerprint databases to Unknown Agencies, but my feeling is if the NSA doesn't have a full set of every finger put on a laptop keypad in the past 10 years I should eat my hat. Wnt (talk) 19:10, 5 October 2012 (UTC)[reply]
There are tactile displays and chord keyboards. The issue with nonstandard keyboard layouts is getting people to learn to use them. I don't know what's holding back tactile displays, but it's easy to guess (cheap mass production and making them transparent, for starters). -- BenRG (talk) 23:50, 5 October 2012 (UTC)[reply]
Yes in case it wasn't clear what I meant, while you could likely develop something better taking advantage of the whole screen (and there are likely better alternatives out there), this is unlikely to succeed because few people would use it. Even despite the differences and problems, if you're a decent typist the existing knowledge greatly helps in using the virtual keyboard. Getting people to switch to something else is difficult at best. Even the sliding Swype despite the alleged advantages seems to be less popular then the tapping mode and stuff like SwiftKey because most people just find it too annoying to learn to slide. And without taking a side in the great Dvorak Simplified Keyboard debate, I think even most of those who argue it isn't better then QWERTY don't deny that even if it were better many people wouldn't switch simply because they don't want to have to relearn. Nil Einne (talk) 05:14, 6 October 2012 (UTC)[reply]
P.S. I should add that even with a 4.7" phone and with whatever keyboard design/layout you develop and presuming the user is willing to learn it, it's hard to imagine it'll ever be as fast as with a larger keyboard. One possibility is that QWERTY is really so bad that with your fancy layout it'll be be faster but this seems unlikely. The more likely possibility is that your design will be fast enough for most purposes. However even that being the case there's still the editing problems I alluded to earlier. (In fact while perhaps I didn't make this clear, particularly outside commenting without refs, it's likely to be the more significant problem.) This is still a rapidly developing interface area and undoutedly things will get better but the fact of the matter no matter how big your virtual display is, if your input device is still the size of the phone screen it's difficult to imagine it'll ever be that easy. Nil Einne (talk) 05:33, 6 October 2012 (UTC)[reply]
Here's my idea:
1) High-res display glasses (at least 1920x1024 per eye) to provide the display.
2) A pair of VR gloves with tactile feedback on the fingertips.
3) Virtual reality software which will provide a full-sized virtual keyboard on any hard surface, so you can type on it and feel key-clicks as you type.
Can visible light induce an electric current in an antenna?
As visible light is also electromagnetic radiation, can it not induce an electric current in a properly oriented antenna, just like microwaves do? I am kind of aware that the antenna should be approximately the same size of (or comaparable to the) wavelength of the radiation. If this is the problem, if we make microantennas (of the order of micro meters), can we generate electric energy from visible light (I am not talking about the photo voltaic effect) - WikiCheng | Talk 17:50, 5 October 2012 (UTC)[reply]
Yes, in principle one can make antennas that respond to light. However, the feature size of the wires and other components becomes extremely small (e.g. 10 nm) since the size of the entire antenna needs to be comparable to the wavelength of light (e.g. hundreds of nm). Such things are possible with current technology, but still difficult and the resulting antennas are currently only of real interest as a research tool. Each antenna captures only a tiny amount of energy, and so you would need huge arrays for energy generation. All in all, they are simply way too expensive to compete with other light-to-electricity power technologies. For some details, try [10]. Dragons flight (talk) 18:14, 5 October 2012 (UTC)[reply]
Light frequency EM waves will not travel over conductors suitable for much lower frequencies. If I build an antenna to capture some frequency of electromagnetic radiation, say 800 mHz, then the coax or lead-in wires will carry electric current of that same frequency to a receiver. If the antenna picks up much higher frequency microwave radiation, then a dish could focus the energy on a waveguide which could carry it to a receiver. A coax would work well to carry microwave frequency EM radiation. "Light" is just em radiation of a much higher frequency and much shorter wavelength. The question seems to imply that an "antenna for light" would send down from the antenna "electric current" which is not "light." If I used a parabolic reflector or a convex lens to collect light and focus it on a fiber optic cable, a "light pipe" or even a glass rod and convey it down from the collector, it might lose some of its properties, but wouldn't that amount to what the OP requests? That is basically what a Telescope, receiving EM radiation in the 405 THz to 790 THz frequency range. Mirrors and "beam combiners" can be used to combine the signal from multiple telescope mirrors, like combining the multiple units in some V antennas. You just can't make light become electrical current of a much lower frequency which will be picked up by wire antenna elements of a practical size and then be made to travel down conventional antenna wire or coax like a radio or TV signal. Edison (talk) 21:11, 5 October 2012 (UTC)[reply]
You can, however, take advantage of the photoelectric effect, which is a totally different physical process, to convert light-frequency electromagnetic radiation in to an electromotive force, and therefore drive a current down a conductor. The incident photon frees an electron from certain types of material, and a signal can propagate through an attached electrical circuit. The photoelectric process relies on properties of atomic physics, though, and is unlike the ordinary induction of electric current in a radio-frequency antenna. Nimur (talk) 22:16, 5 October 2012 (UTC)[reply]
The interesting here is that you could, in principle, store the electromagnetic fields detected by each antenna as a function of time. So, you would have a visible light telescope that detects light coherently. All the information about objects in any arbitrary direction will be stored this way. To look at some position in the sky at some time in the past, you just have to access the memory and add up the detected fields with the right phase shifts. Count Iblis (talk) 15:42, 6 October 2012 (UTC)[reply]
Absolutely, yes. But, if you work out the physics and mathematics for resolution of an image, you will probably find that your device has similar physical dimensions and properties to a camera. There has been an immense amount of theoretical and applied research in to the subject of wave field imaging, and application of the imaging condition to coherently-sampled time-history measurements. For example, a radio telescope array can be used to synthetically image radio waves; this same algorithm has common application in synthetic aperture RADAR, using a differently-shaped antenna. In a similar way, SONAR can be used to generate an image using coherently-sampled acoustic wave fields. The hand-held medical ultrasound imager uses one (or more) sensors, and performs coherent sampling with multiple samples collected at different times, to generate a single "snapshot" image of a medical subject. The capability of modern computers to fully analyze a three-dimensional wave-field has been increasing, steadily, over the last few decades, so as practical implementation problems are solved, we are getting closer and closer to theoretical limitations governed by wave mechanics. At the end of the day, you can't construct an image if you can't physically resolve the waveform data - which is governed by the mathematics of sampling. Nimur (talk) 17:49, 6 October 2012 (UTC)[reply]
I can visualize pressure inside a liquid pretty easily: water molecules are touching each other and exerting forces on their neighbors. But I'm a little confused about how pressure in a gas works. The gas molecules pass usually through each other, so when people speak of a force by one part of the gas on another, are they speaking about the occasional collision between gas molecules or about some sort of momentum flux due to gas molecules moving through an imaginary surface? 74.15.136.9 (talk) 03:05, 6 October 2012 (UTC)[reply]
It doesn't matter much whether the gas molecules collide or not, though I think the mean free path in typical gases may be shorter than you suppose. Even if they never collided with each other, they'd still collide with the walls of the container (otherwise they'd keep on going and not stay in the container), and thereby exert force on it. Or, with no container, if you have a solid object immersed in the gas, the same arguments apply — the gas molecules collide with the solid object, bounce off it, and thereby exert force on it/transfer momentum to it. --Trovatore (talk) 03:08, 6 October 2012 (UTC)[reply]
Oh, actually I missed that you said "one part of the gas on another". In that case, I suppose it does matter (if the gas molecules really passed freely through the gas at large, they'd just keep moving through it until they hit a solid boundary, and then it wouldn't make much sense to talk about "one part of the gas"). But the article I linked says that under standard conditions (one atmosphere; not sure whether 0 or 25 degrees Celsius) the mean free path is only 68 nanometers. --Trovatore (talk) 03:13, 6 October 2012 (UTC)[reply]
In a cube of 68nm, there would be (I think) (68*10-9)3*6.025*1023*1000/22.4=8457 molecules. But that's if it was 0°C. If that gives any idea... Ssscienccce (talk) 04:23, 6 October 2012 (UTC)[reply]
Not sure just what your point is, but I guess that is a good intuitive guide to what's going on, assuming your figures are right. The cube root of that is about 20, so roughly speaking you're saying a molecule would pass 20 other molecules before bumping into one. --Trovatore (talk) 05:39, 6 October 2012 (UTC)[reply]
Just to get an idea, as you say; maybe I'm a bit obsessive-compulsive when it comes to calculations, judging by the amount of scratch paper riddled with numbers (if that's the right expression) going in the bin every day. Ssscienccce (talk) 07:53, 6 October 2012 (UTC)[reply]
The molecules in a gas do collide with each other, which allows the gas to undergo things like laminar flow and turbulent flow and allows pressure to equilibrate throughout the gas. In situations where the gas molecules do collide with the walls more frequently than with each other (such as small pores), Knudsen diffusion occurs, and the macroscopic notion of pressure breaks down somewhat.--Wikimedes (talk) 07:18, 6 October 2012 (UTC)[reply]
You can work out from the gas laws and kinetic equations and so forth (we did it in high school, I can't give the exact derivation from memory) that on average an individual oxygen or nitrogen molecule in the atmosphere at room temperature travels about 10cm before it hits another air molecule (mean free path mentioned above) and does so while travelling at 1,000 kmph. They may be small, but they are fast, and there's a lot of them. Grokking that should help your intuition. μηδείς (talk) 16:54, 6 October 2012 (UTC)[reply]
I think you're off by about seven orders of magnitude. Maybe you meant nm instead of cm? --Trovatore (talk) 17:48, 6 October 2012 (UTC)[reply]
I may certainly be wrong, I am going on memory from the 80's. But I did mean to say 10cm. Nanometers sounds way too small. I'll see if I can google a result. Hmm, yes, our own article says 68nm. I wonder if I am just remembering the number wrong, or if I have some other result in mind. Well, that should also put my 1,000kmph figure to doubt. μηδείς (talk) 17:52, 6 October 2012 (UTC)[reply]
Physical Chemistry by Atkins 6th edition p.30 gives a typical mean free path for N2 at 1 atm to be about 70nm. It also states that for N2 or O2 at 25C and 1atm the molecules travel at about 350m/s which is 1260km/h, so Medeis' speed is about right.--Wikimedes (talk) 18:30, 6 October 2012 (UTC)[reply]
Indeed, and it's not all that difficult to estimate this from first principles. The Bohr radius is 0.5*10^(-10) meters, so the elastic cross section for hydrogen molecules should be of the order of few times
10^(-20) m^2, let's take this to be 10^(-19) m^2. Then the mean free path L is the average distance a hydrogen molecule needs to travel before collding with another one. This means that within the volume swept out by the cross section of 10^(-20) m^2 over the distance L of 10^(-19) m^2 L , there should be one molecule on average.
The number density of hydrogen molecules at room temperature and a pressure of p = 1 atmosphere is
n = p/(k T) = 2.5*10^(25) m^(-3). So, within the volume of 10^(-20) m^2 L there are 2.5*10^(25) m^(-3)* 10^(-19) m^2 L = 2.5*10^(6) L/m molecules, but L being the mean free path this should equal 1. This means that L = 4*10^(-7) meters. Count Iblis (talk) 19:58, 6 October 2012 (UTC)[reply]
Maybe Medeis was thinking of Rutherford scattering? Alpha particles will travel several centimeters in air before being deflected by a nucleus. Ssscienccce (talk) 08:31, 7 October 2012 (UTC)[reply]
I am afraid we may just have gotten the wrong answer somehow when we did the derivation as a class, since I remember being struck by the results being on a visibly imaginable scale, which 70nm is definitely not. Our chem teacher was on the ball, quite a good mathematician, so I can't see her making such a large error, or letting us remain in one. (I do remember getting a speed of around 1,250 kmph, and I just rounded it down for the example. I think the Rutherford result is a good guess as to what may be confusing me, or the fact that there's on the order of one hydrogen atom per cubic decimeter in deep space.) I'll have to ask some other students of hers if they remember doing the derivation.
I assume that the speed of sound is a result of the speed of the particles derived here? μηδείς (talk) 21:34, 7 October 2012 (UTC)[reply]
What kind of tech advance will we need to have GPS-locatable wedding rings?
That's the one thing you dread the most - losing a wedding ring. Sometimes you forget it in a public restroom, or during a picnic in an open field out there, you forget you took it off and now the field is too big for you to spot it.
That's why I would hope for my and her wedding ring to have a GPS chip, so that once the ring is lost, you go to "ringlo.st" and enter your information, then the GPS satellite tracks the ring down for you.
If anyone's concerned about "powering" the chip, I would hope that piezomechanics allow for kinetic movements to keep it powered up.
A. So how much farther do the necessary components need to miniaturize in order to fit comfortably in a wedding ring?
B. How much might it cost?
C. Would it be waterproof?
D. Are there other issues you'd like to bring up with this hypothetical GPS-locatable wedding ring?
A) I think the electronics are mostly almost small enough already, with a couple exceptions: the battery (which it would need to remain powered when taken off) and the antenna (I would also include the display and keyboard, but presumably this would lack those).
C) I don't see waterproofing it being a major problem.
D) First, it wouldn't be "solid gold" anymore, so would be lighter and not feel like a quality ring. This would also make it more fragile. Finally, putting any type of technology on it means it could become obsolete, let's say if GPS units all switch to different frequencies.
A more reasonable approach which could be taken right now are to put passive RFID tags in them. These don't require a battery, but only work at a short distance, with a scanner you'd carry around. So, it would work great if you lost your ring around the house, but not if you lost it someplace random outside the house. However, the only reasons I can see for taking your wedding ring off outside the house are at a jewelry store when having it cleaned/adjusted, at a clinic for a CAT scan and such, and when engaged in adultery. Hopefully that's few enough places where you could bring the scanner. I don't quite understand why you'd take it off in a public restroom (unless this is where one engages in adultery). :-) StuRat (talk) 15:30, 6 October 2012 (UTC)[reply]
Another reason to take your ring off is when working with some dangerous machinery. I wirk with people in a factory, and some of them remove rings when working because of the danger of having the ring trap in active machinery. Some of them have lost fingers because of rings. 217.158.236.14 (talk) 08:19, 8 October 2012 (UTC)[reply]
As a workaround, could you just buy a fine chain, worn on your neck or attached to your jeans, and put the ring on it whenever you take it off? – b_jonas 19:27, 6 October 2012 (UTC)[reply]
Or just never take it off. My ring has not left my finger in over forty years, and now I cannot physically remove it.--Shantavira|feed me 19:54, 6 October 2012 (UTC)[reply]
I agree that, currently, GPS tracking is infeasible, and probably will be for your lifetime due to power source constraints (unless you are content to replace/recharge the power source rather often). Another unsolicited alternative: get a dozen of these [11], declare them identical in the sense of "wedding ring," and always have a spare if you lose one ;) They also have safety benefits; I know someone who lost his left ring finger because he was wearing his wedding ring... SemanticMantis (talk) 21:16, 6 October 2012 (UTC)[reply]
Good idea. If you must have a silver/gold/platinum/bejeweled wedding ring, keep it in a vault, and wear something disposable from day to day. StuRat (talk) 21:33, 6 October 2012 (UTC)[reply]
Hi, OP here. No one answered how well piezo-recharging would work on rings.
E. Wristwatches are recharged by the kinetic movements of the wearer all the time, so why couldn't rings?
F. Also, if GPS changes to different frequencies, wouldn't the wearers get a mail/email notification letting them know of this, and to get it changed at the local jeweler / electronic store as soon as possible? --70.179.167.78 (talk) 23:41, 6 October 2012 (UTC)[reply]
E) It's not enough to broadcast a signal to a cell phone tower, which is what your system would require (or, even worse, broadcasting to a satellite).
F) Perhaps, but plan on doing this every 5-10 years, as cell phone technology constantly changes. You'd also probably have to replace the guts, as a new frequency might require new electronics and a new antenna. Think about it this way, what 50 year old portable electronic technology is still used today ? Very little, for good reason. See many people with mono AM transistor radios ? StuRat (talk) 00:08, 7 October 2012 (UTC)[reply]
For future navigation I should note that the question on kinetic reclamation (charging by hand movements) is now being archived at Wikipedia:Reference_desk/Archives/Science/2012_October_2 though it is still visible above for now. Wnt (talk) 21:40, 7 October 2012 (UTC)[reply]
It's amazing that nobody has yet pointed out that GPS satellites do not track things. They broadcast a signal that GPS devices use to calculate their location. To make this work, the ring would have to include a GPS tracker and something comparable to a cell phone, so that it could call the owner to give its location. Looie496 (talk) 05:11, 7 October 2012 (UTC)[reply]
I did, in my response to E, above. StuRat (talk) 06:27, 7 October 2012 (UTC)[reply]
What's being described is essentially a cell phone, in that it can be tracked and communicated with (or from) at any time. People of most religions might do without the keypad and the address book, but there would be little savings in omitting the ability to communicate voice since microphones and speakers have become very small. So the question collapses to one of when a cell phone would be possible as a ring. This might depend on some genuinely unknown factors, such as the hazards of terahertz radiation and the feasibility of using it as a routine communications medium (since it could theoretically have a shorter antenna, etc.). Wnt (talk) 21:36, 7 October 2012 (UTC)[reply]
Religions ? StuRat (talk) 21:39, 7 October 2012 (UTC)[reply]
Antenna efficiency drops off very quickly below 1/4 wavelength - a wedding ring is most probably too small to house a GPS receiver antenna large enough to work. Even GPS receivers with full size antennas don't work indoors. It's cellular transmission antenna would be even less efficient though might still be able to work close to a cellular base station, but GPS satellite signals are very weak even outdoors with wide open skies. Roger (talk) 22:00, 7 October 2012 (UTC)[reply]
That's why I mentioned terahertz... though I have a wild suspicion that there's some metamaterial based solution to that problem that will turn up sooner or later if it hasn't already. (by analogy to microscopes beating the diffraction limit) Wnt (talk) 20:47, 8 October 2012 (UTC)[reply]
It would be more feasible to equip your environment with recording video cameras to track your ring's and your own every movement. They could be attached to your clothing or body in case you visit rest rooms. Or you could have movement sensors attached to your hands. Presumably the pattern of movement between your hands is characteristic of pulling the ring off. Then software could alarm you if you step more than a meter away from the ring. All this would be possible with today's accelerometers and cameras. Graeme Bartlett (talk) 23:23, 7 October 2012 (UTC)[reply]
Those don't sound practical, to me. Perhaps the RFID tag and scanner combo could be set up so that you always carry the scanner with you, and an alarm goes off whenever the ring moves out of range (a few yards/meters). StuRat (talk) 21:06, 8 October 2012 (UTC)[reply]
Something I half-remember from a wildlife documentary from years and years ago. It's a frog or toad that lays her eggs and then places them in indentations on her back - and her skin actually grows over and covers the eggs completely. Then the tadpoles develop inside the eggs without hatching, and emerge from her back as fully-formed froglets...
Does this creature sound familiar to anyone? As I say, it was a long time ago that I saw this on TV, so my memory might be playing tricks on me - but I do seem to remember watching this as a kid and being freaked out by the skin part. --Kurt Shaped Box (talk) 23:28, 6 October 2012 (UTC)[reply]
Shudder. That is still as disturbing to me now. --Kurt Shaped Box (talk) 00:05, 7 October 2012 (UTC)[reply]
Well done. I was going to suggest the Midwife toad, but it doesn't really fit the bill. Perhaps someone could add a brief mention of the Surinam Toad to our Frog article? Alansplodge (talk) 00:05, 7 October 2012 (UTC)[reply]
The mere thought of that makes me reach for my backscratcher. StuRat (talk) 04:55, 7 October 2012 (UTC) [reply]
Beautiful! evolution at its best. Richard Avery (talk) 07:19, 7 October 2012 (UTC)[reply]
It reminds me of those pictures that were doing the email rounds a few years ago that purportedly showed some horrible skin disease - but in actuality were elements of lotus seed pods 'shopped onto various body parts. --Kurt Shaped Box (talk) 10:46, 7 October 2012 (UTC)[reply]
There's a general term "marsupial frog" referring to this method of incubation. Wnt (talk) 21:44, 7 October 2012 (UTC)[reply]
Actually the Neobatrachian marsupial frogs have a pouch into which the eggs are deposited, whereas in the unrelated Mesobatrachian Suriname Toad the eggs are laid on the back and the skin of the back swells around them, enclosing each separately. μηδείς (talk) 01:38, 12 October 2012 (UTC)[reply]
October 7
what is the 1D solution for the particle in a box for fermions with spin?
All discussions of fermions in a box seem to involve 3D boxes. But what about 1D boxes? 71.207.151.227 (talk) 01:37, 7 October 2012 (UTC)[reply]
Thanks to uncertainty, you can't pin a good fermion down. Interesting applications have been made using Quantum wire however. Hcobb (talk) 02:08, 7 October 2012 (UTC)[reply]
Pardon me for being ignorant (BSc in something that probably isn't a science...), but is it possible to fit a fermion into a one-dimensional box? Don't they occupy a (small) volume of three-dimensional space? Or does 'box' mean something else entirely in this context? AndyTheGrump (talk) 04:53, 7 October 2012 (UTC)[reply]
AndyTheGrump: I think our Particle in a box page may help clarify. The use of a conceptual/mathematical solution in one dimension makes the math more tractable, with solutions generalizable to higher dimensions. -- Scray (talk) 17:14, 7 October 2012 (UTC)[reply]
It's analogous to the 3D problem. I think you are working directly in the limit of a large volume, otherwise there wouldn't have been a question about this. In that case, you need the density of states. In general, the number of single particle quantum states for a spin 1/s particle in some large volume V and in a volume of momentum space Vp is given as
2 V Vp/h^n, where n is the number of dimensions. The factor 2 is the spin degeneracy, i.e. it takes into account that for each wavefunction in configuration space, you have two independent spin states. Count Iblis (talk) 15:32, 7 October 2012 (UTC)[reply]
Will Santa Claus' house be underwater by 2020?
Will Santa Claus' house be underwater by 2020? And how will scientists explain this to all the children of the world? 220.239.37.244 (talk) 02:16, 7 October 2012 (UTC)[reply]
I suspect that most wise scientists avoid formal discussion and attempts at explanation of Santa's house. HiLo48 (talk) 02:58, 7 October 2012 (UTC)[reply]
Since Santa needed to get a 2nd mortgage to cover Rudolph's alcoholism treatments, his own Weight Watchers membership, and the cost of human growth hormone treatments for all his helpers afflicted by dwarfism, he was unprepared for the collapse in real estate prices. So, yes, his house is already underwater. StuRat (talk) 04:53, 7 October 2012 (UTC)[reply]
It's sad that with mortgages being in the news so much over the last few years, this really was the first definition of "underwater" that came to my mind. However, my thought concerning it was that the mortgage was probably paid off at least a hundred years ago. Eric (EWS23) 08:54, 13 October 2012 (UTC) [reply]
Bear in mind that the underwater period will be during the summer, when he and his fellow kallikantzaroi are working busily deep underground. Wnt (talk) 21:30, 7 October 2012 (UTC)[reply]
No, and, generally, warm-blooded animals can't, since it would be difficult to see beyond their own infrared glow, to see, say, the glow of a mouse in some underbrush. StuRat (talk) 06:08, 7 October 2012 (UTC)[reply]
You're welcome. I'll mark this Q resolved. StuRat (talk) 21:33, 7 October 2012 (UTC)[reply]
Well, resolved, but I'd add this, from our article cat senses: Cats are able to distinguish between blues and violets better than between colours near the red end of the spectrum. - Nunh-huh 22:56, 7 October 2012 (UTC)[reply]
I'm removing the resolved tag; such tags aren't recommended (the recent discussion on the Ref Desk talk page touches on the reasons why). Also, I notice that no one has provided a single source for their statements, which is very disappointing, given that this is a Reference Desk.
Moreover, StuRat's responses are inaccurate and imprecise, at best. There is published literature (some of it, which I've linked below, is both online and free of charge) which reports on the sensitivity of cat's eyes to near-infrared radiation.
Both studies note that the sensitivity of the cat's eye to far-red and infrared radiation is certainly lower than to middle-of-the-visible-spectrum light, but both also demonstrate measurable responses at longer wavelengths. Gekeler et al. go out to 826nm (laser line illumination) and 875nm (IR emitting diode). Speaking from my own personal experience as a mammalian scientist with normal color vision, human beings can certainly see bright sources with wavelengths out into the middle 800's.
Delving a bit further into the question, we can ask what happens at wavelengths that get a bit longer—what happens when you hit 950 or 1000nm (1 micrometer)? Then you start to get stuck by the physical properties of water. Infrared light at 1000nm and longer tends to be strongly absorbed by water, which – inconveniently – is a major component of the vitreous humour that fills the eyeball.
For comparison, that the blackbody emission of a human-body-temperature object peaks way up around 10 micrometers. That's deep, deep into wavelengths strongly absorbed by water (passage through 1 cm of water will absorb 99.9% of infrared light at this wavelength; the eye is essentially opaque to these rays). Forget being blinded by one's own infrared glow—at these wavelengths one is blinded by the opacity of one's own eye. TenOfAllTrades(talk) 02:29, 8 October 2012 (UTC)[reply]
I think it's further worth noting that, at least in snakes, sensation of IR is not done by the eyes, but by specialized "pit" organs. Also, in snakes, there is no specific reception of IR wavelengths. Rather, the pits are structured in a way that crudely focuses radiant heat onto nerve endings that are actually sensing temperature. Someguy1221 (talk) 02:57, 8 October 2012 (UTC)[reply]
It may also be worth pointing out, in regard to StuRat's answer, that infrared is quite a wide spectrum. If, for example, cats were able to see one-micron light, that would be well into the near infrared range by almost anyone's standards, but there would be hardly any glare at all from the cat itself. Presumably Stu was talking about much longer-wave infrared, say around ten microns. --Trovatore (talk) 05:15, 8 October 2012 (UTC)[reply]
My point was that IR detection at useful wavelengths (ones that would allow them to see warm-blooded predators and prey) would be difficult due to their own glow at those frequencies. IR at other frequencies doesn't appear to have any advantage to a cat over visible light. StuRat (talk) 21:12, 8 October 2012 (UTC)[reply]
Cat's and humans use the same proteins and mechanisms to see the longer wavelengths from the visible spectrum, just as most animals, so there will be little difference between them. The ability to capture more light will also help in seeing some near infrared, but I don't think they can see longer wavelengths than humans can (although humans may require higher intensity levels). There doesn't seem to be a protein or other biological mechanism that makes it possible to see much longer wavelengths than 850nm. Porphyropsin might add slightly to the range, but other than that, I don't know any.
In the UV range, there will be much more diversity, since the higher the frequency of the light is, the more chemical and biochemical mechanisms exist that can be influenced by it.
As Someguy1221 points out, the IR vision in snakes is based on temperature sensing, not direct IR vision. The pit organ's reflectivity in the visible spectrum is very high, had it not been, it would also detect visible light, and be useless to the snake I presume. Ssscienccce (talk) 21:12, 8 October 2012 (UTC)[reply]
I've tested my color-vision range with a spectroscope some time ago, and found out that I can see even faint IR sources at wavelengths of up to 800 nm at least (to me, they appear a dark reddish-brown). Does this mean that I'm a cat? ;-) 24.23.196.85 (talk) 02:31, 10 October 2012 (UTC)[reply]
It doesn't have a permanent dipole but its electron density map (why can't I find a basic electron density map of it online?) would be strongly polarised, with the carbonyl oxygens retaining most of the electron density and the carbonyl center being electropositive. Yet why doesn't carbon dioxide remove some of the slightly polar flavor compounds that are found in caffeine (CO2-water partition coefficient at least 0.3?) ? It has some polarity, right, just not dipolarity. 71.207.151.227 (talk) 16:35, 7 October 2012 (UTC)[reply]
This is a quadrupole. This is not what CO2 looks like. No, it has no polarity. A "quadrupole" would look like the pic I am appending. Think of it this way: the two diametrically oppose oxygens are pulling electrons equally from each other across the carbon atom. That creates a roughly equal distribution of electrons across the whole molecule. In general, any molecule which shows perfect VSEPR symmetry (i.e. one of the basic 3 VSEPR shapes: linear, trigonal planar, or tetrahedral) will be perfectly non-polar, so long as every point is the same atom, like CO2 where both atoms attached to the central atom are oxygen. This is true even where there is a large difference in electronegativity among the individual atoms, because those electronegativity differences will, in essence, counteract each other. So even molecules like tetrafluoromethane show the same nonpolar character as methane; CF4 and CH4 have comparable melting and boiling points because they are equally nonpolar, the difference is explainable by differences in London dispersion forces due to the difference in molecule size. --Jayron32 18:46, 7 October 2012 (UTC)[reply]
Apparently the quadrupole moment of carbon dioxide is -4.1 x 10-26 e.s.u.,[12] considerably stronger than that of nitrogen, hydrogen, and methane, which (hopefully) can permit its separation from exhaust by certain three-dimensional porous structures intended to mitigate greenhouse emissions.[13]Wnt (talk) 21:28, 7 October 2012 (UTC)[reply]
Well, there you go. --Jayron32 01:32, 8 October 2012 (UTC)[reply]
Is it wrong to say that we come from the monkey?
Actually, it's from the apes, but maybe the apes came from the monkey, so it's not wrong after all. OsmanRF34 (talk) 22:42, 7 October 2012 (UTC)[reply]
See [14]. We are on a parallel evolutionary path with monkeys, not direct descendents from them. Our common ancestors are all extinct. StuRat (talk) 22:59, 7 October 2012 (UTC)[reply]
Well, even if our common ancestors are extinct, they still could be called 'monkeys.' BTW, I am afraid the graphic you linked to is not the evolutionary perspective, but just the present day classification. OsmanRF34 (talk) 23:32, 7 October 2012 (UTC)[reply]
I would interpret StuRat's linked diagram to mean "yes". While it is true that the early ancestors of monkeys and apes, living at a different time than the present and not being a member of any modern clade, might be called whatever we wish, still, it seems logical to call the single common ancestor of "New World monkeys" (Platyrrhini) and "Old World monkeys" (Catarrhini) a "monkey". The catch there is that "monkey" is not a monophyletic group, since it includes a subgroup of "apes" that by tradition are not called monkeys, and if you're not defining it monophyletically, you can define it a lot of ways - for example, you could define it to include every one of the individual subgroups but not the common ancestor. But I think that's a stretch. Wnt (talk) 00:51, 8 October 2012 (UTC)[reply]
Biologists use precise terminology to avoid getting bogged down in semantic issues like this. A biologist would say that we are descended from animals that belong to the group simiiformes, which includes monkeys and their ancestors. Most biologists when speaking informally would probably apply the term "monkey" to everything in simiiformes, but there is no official rule governing this. Looie496 (talk) 00:50, 8 October 2012 (UTC)[reply]
Apes, including Humans, are Catarrhines. Our common ancestor with the Catarrhine monkeys would be itself considered a catarrhine monkey. Its common ancestor with the platyrrhine monkeys would also be considered a monkey. Yes, we are descended from some animals which, if they were living today, would unambiguously be considered monkeys. μηδείς (talk) 04:10, 8 October 2012 (UTC)[reply]
I am stuck on this physical chemistry question and would really appreciate some help. Here goes the question
Many processes such as the fabrication of integrated circuits are carried out in a vacuum chamber to avoid reaction of the material with oxygen in the atmosphere. It is difficult to routinely lower the pressure in a vacuum chamber below 1.0 * 10^-10 Torr
A) Calculate the molar density at this pressure at 299K
Well this is just simple substitution: P = ρ R T where ρ is the molar density
ρ = P/RT
= 1*10^-10/(299 * 62.36)
= 5.36 * 10^-15
B) What fraction of the gas phase molecules initially present for 1.0 atm in the chamber are present at 1.0 * 10^-10 Torr?
This is the tricky part. I know that PV = nRT and when you lower the pressure from 1.0 atm (760 torr) to 1.0 * 10^-10 torr, and assuming that V and T are held constant, n is lowered as well. Since molar density is defined to be the number of moles over volume
State 1 = 760 torr
ρ1 = n1/V = P1/RT = 0.0407
State 2 = 1.0 * 10^-10 torr
ρ2 = n2/V = 5.36 * 10^-15
The ratio of n1 to n2 can be calculated by dividing ρ1 by ρ2 which equates to 1.32 * 10^-13.
The online homework system is telling me that my answer is wrong and I am just trying to figure out what I did wrong. Any help is appreciated! Thanks in advance! — Preceding unsigned comment added by 169.232.236.95 (talk) 23:03, 7 October 2012 (UTC)[reply]
I worked it out without looking at your method, and got the same answer as you (1.322 x 10-13). Does the online system give you their numerical answer? If you can post that, we might be able to spot a mistake they made. Ratbone124.178.60.218 (talk) 00:25, 8 October 2012 (UTC)[reply]
Remembering a similar problem with a computer program checking answers some time ago, maybe you should try giving the answer as 10-10/760 or 10-11/76 instead of the rounded off result. Ssscienccce (talk) 21:32, 8 October 2012 (UTC)[reply]
I've never seen an automatic physics or chemistry homework checker that wanted a raw fraction when asking for something that can be solved as a numerical value. As far as rounding though, I have seen several that only accept an answer as "correct" if it is the proper number of significant figures (as well as numerically correct obviously). DMacks (talk) 21:46, 8 October 2012 (UTC)[reply]
It turns out that the program accepts the fraction 10^-10/760. I think it was a significant figure issue. Thank you all! — Preceding unsigned comment added by 169.232.236.127 (talk) 22:40, 8 October 2012 (UTC)[reply]
Credit to StuRat who taught me. @DMacks: Maybe the programs are getting better? I remember how much my teachers disapproved of rounded off results when the answer could be presented by a short, simple expression like a fraction or square root. Ssscienccce (talk) 08:24, 10 October 2012 (UTC)[reply]
They probably are. All secondary school students (in the UK) these days tend to have calculators which are capable of giving answers as fractions and even surds. You have to be more cunning about testing for true understanding, where you used to have the lazy option of simply requiring exact answers (when calculators would only give a decimal approximation). It causes me a moment of wonder, every so often, that they all carry these little things that display such answers.. 86.159.77.170 (talk) 19:47, 11 October 2012 (UTC)[reply]
October 8
Accuracy of forward looking economic statements
There are many cases were businessmen, economists, and similar people have to predict what the market is going to look like for their product weeks, months, or even years in advance. For example, farmers hope to plant crops that will give them a good profit come harvest time. Or alternatively, a book publisher tries to predict demand when deciding on the size of a print run. In some cases there are robust futures markets to help, in other cases in-depth business studies might be undertaken, but often such predictive judgments seems to boil down to some expert's personal opinion. I'm looking for materials I might read reviewing the successes and failures of such forward looking economic statements. For example, when experts predict that the GDP will increase over the next 12 months, how often are they right? Do the target prices set by stock market analysts have predictive value? Etc. Also, I would like to read about cases where detailed mathematical modeling has been applied to economic problems, and where such models have tended to do well or poorly. Thanks for your help. Dragons flight (talk) 11:29, 8 October 2012 (UTC)[reply]
I have no answer to the general question, nor, unfortunately, references. But one of the first scientific meetings I attended (back in 199X as a student) was a local meeting of machine learning researchers. Two or three groups had tried to predict stock prices from past performance, and their analysis seems to agree that the past data has essentially no predictive value. I don't know if that is still the state of the art, and I know even less how this applies to more macroscopic questions. --Stephan Schulz (talk) 12:04, 8 October 2012 (UTC)[reply]
I recall reading a review of a book on just this subject... I believe it was this one. The book's conclusion, and the conclusion of many other studies, is that experts have a positively lousy track record for accurately predicting the future broadly. You might check out the book, though. --Mr.98 (talk) 14:59, 8 October 2012 (UTC)[reply]
A well-received book with a similar theme is The Black Swan (as well as the author's earlier book Fooled by Randomness). They're not going to have comprehensive data about what you seek, but rather selected examples to further the author's argument (basically that predictions of the future are worthless). Buddy431 (talk) 23:01, 8 October 2012 (UTC)[reply]
At one stage in my career, I worked in the planning group of a large governemnt department, making decisions on the provision on capital infrastructure. This involved working out the Net Present Value (see http://en.wikipedia.org/wiki/Net_present_value), and applying Jacobson Provisoning Theory. JPV is a mathematical theory that tells you what size increments to install to meet a requirement that grows over time in order to minimise the cost, for example the provision of hospital beds in a city whose population is growing. You could build in one big project that meets growth requirments for twenty years and get econoimies of scale, or build say every two years another ward. JPV tells you which costs less. Much infrastructure can only be planned on a long term basis, 10 or 20 years.
The point is, both NPV and JPV require a prediction of demand growth, interest rates, and inflation in order to make any sense. We used to get a yearly report from Treasury that predicted these things. Generally, they gave upper and lower limits at a certain level of confidence, for intervals 1, 2, 5, 10, and 20 years out. Experience showed that their predictions within thse limits were very good, with certain exceptions I will describe below. Naturally the limits got broader as the time frame increased. My experience is Australian, but if Australia could do it, other advanced countries can too. These reports were not made public when published, but would be available from National Archives.
Economic predictions released to the media by certain "experts" are far far less reliable, as they don't have the resources, and often use cheap data of dubious value, such as the number of job adverts printed in morning newspapers.
Treasury ecomonic predictions generally made an assumption that the government of the day would remain "competent", and say something like "we expect the politicians to take this reasonable option, or possibly that option, and factored this in when estimating the upper and lower limits." Mostly, Australia has had "competent" governments - the sort where the political leaders took advice from the public service. An example from Australia is the Menzies Govt (conservative) in the 1950's and 1960's. At other times we've had "incompetent" govts, where political leaders assume the public service is not to be trusted. This can lead to reform, but makes new economic predictions very difficult, and existing predictions incorrect. The 1970's Witlam Govt (Labor) is an example. More recently, we've had political leaders that intelligently challenge the advice from the public service. The Keating Govt (Labor) is an example. This is the best form of government in all respects and allows reasonably good economic predictions.
Things like war breaking out, oil crises, can ruin any prediction.
It's more difficult now than it used to be. Today's politicians don't have the intellect of earlier leaders, and tend to go more on ideology than on facts or reasonable inference. Also, economies used to be quite regional, but economies are now strongly linked globally. For example, Australia and the USA used to be largely industrial - with large numbers of folk employed in factory production of all kinds. This makes things controllable. Nowadays, factory production is not the great employer - the service industries are. This makes things unstable. Education standards are falling. As less well educated thinkers enter the workforce, things will get even more unstable.
This (article starting on p.38) is from 2001, but I'd be surprised if much has changed in the forecasting game. Zoonoses (talk) 05:55, 10 October 2012 (UTC)[reply]
See Efficient-market hypothesis. This theory, which has had a lot of holes poked in it but still is considered to have a large element of truth in it, says that as soon as any information relevant to the appropriate price of a particular stock, or to the level of the stock market as a whole, becomes available, it is instantly incorporated into the stock price; any trades that take place after the info becomes available will take place at the newly appropriate price. So no one can beat the market unless they can obtain or predict new information before it becomes generally available to stock traders. In the absense of insider trading, this is tough, though lots of investment advisors are in the business of trying to do it. But studies show that none of them consistently beat the market -- at any given time, someone is beating the market, but later on it's someone else who's beating the market. So the answer is no, stock market forecasts and forecasts of individual stock prices are no better than throwing darts at a dart board, and the above is the theoretical reason for that. The classic book on this is Burton Malkiel's A Random Walk Down Wall Street. Of course an infinite amount has been argued this way and that way about these ideas over the years, such as questioning why the market as a whole didn't see the recent financial crisis coming (in which case the bubble would never have been allowed to grow in the first place, and therefore there would have been no bubble to burst).
A claim often repeated on the internet is that the Great Pyramid at Giza could not be reproduced with today's technology. It is aligned to true north with a greater degree of accuracy than any modern building and we could not match or better it. The quality and accuracy of the stonework is beyond anything that could be done today, even with today's modern tools and equipment.
I just cannot believe that this is true. The sort of website this appears on is usually to do with the paranormal and that fact that the pyramids must have been built by Alien's etc - yet it even appears on some more "reputable" sites.
Another claim is that Giza is located at the precise geographical centre of the earth's landmass and the chances of the pyramid being located there are billions to one. I have researched and debunked this particular gem - how do you find the centre of the surface of the sphere???? — Preceding unsigned comment added by 195.188.208.251 (talk) 11:52, 8 October 2012 (UTC)[reply]
That last one is more appropriate to the math desk, I guess. However, the claim is not "the center of the surface of the sphere", but "the center of the landmass". Land is distributed unevenly over the surface of the earth, so there is an asymmetry that can be used to define a "center" (of course, for most definitions there would be two, one on either side of the earth). Given that there are plenty degrees of freedom for defining "land" (what about floodplains? Do mountains count more than plains? What about the dead sea?) and "center", it's probably easy to come up with a formula that places the pyramids (well, one point in their vicinity) in the center. --Stephan Schulz (talk) 12:31, 8 October 2012 (UTC)[reply]
I found [15] which indicates that the center of mass of the upper layer of the Earth is displaced 29.0 km toward 15.4 N, 150 E ... which looks like the middle of Mariana Trench. Am I reading this backwards? Admittedly I haven't figured out quite what I'm really reading about here as of just yet... they even talk about a "magnetic center". Wnt (talk) 14:46, 8 October 2012 (UTC)[reply]
Presumably, they mean "land area", as in areas where the land and is above sea level. The center of that should be above the equator. If you neglect the Americas, it should be further East. So, perhaps, including the Americas, that might bring it back into Africa. However, the Earth, being round, brings up the question as to whether a pocket of land near the opposite side draws the center of mass towards it, on whichever side is closest, weighted 100% for that area, or whether the area weighting is reduced to account for it "pulling from both sides". You can also find the CG point in 3D, putting it near the Earth's center, then project it back up to the surface, normal to the nearest surface. This seems like the best approach, to me. StuRat (talk) 19:40, 8 October 2012 (UTC)[reply]
Where do you slice open the earth and how do you spread it out on a flat surface to define the center of any subset of it? --Jayron32 19:44, 8 October 2012 (UTC)Edit: Stu made a clarifying point here which renders my question somewhat silly. When he originally made his statements, it was unclear what he was defining. It's clear now, and my question is now moot. --Jayron32 19:48, 8 October 2012 (UTC)[reply]
(ec with Jayron's addition above) I don't think you need to. Aside from the method I listed above, another would be to try every point on the surface of Earth, and for that point find the weighted great circle distance to each bit of land. I could easily write such a program, if I had a file with, say, each square kilometer's longitude and latitude numbers, along with the percentage of land above water (smaller resolutions would make the program really slow). You would want to first look at large intervals, let's say a point every 30 degrees of longitude and latitude, then look at a smaller interval, say a point every 10 degrees of longitude or latitude, around the previous best result, etc., until you get an answer of sufficient accuracy. StuRat (talk) 19:53, 8 October 2012 (UTC)[reply]
Our article Great Pyramid of Giza gives numbers for the precision of its construction. The sides of the base are over 230 meters long and have an average error of 58mm. The base is horizontal and flat to within 15mm. The finished base has an average alignment error (from true north) at the corners of 12 seconds of arc. Those numbers are very impressive for such an huge and ancient construction, but I can't see why we wouldn't be capable of reaching the same accuracy today. I can't find good references for the tolerances of large modern buildings, probably because the accuracy in placement and construction simply isn't noteworthy. 209.131.76.183 (talk) 14:55, 8 October 2012 (UTC)[reply]
For what it's worth, most modern construction uses a tolerance of about 1/4" in 10 ft (less than 1 cm in 3 m), non-cumulative, for everyday work, and greater accuracy can be attained at extra cost, bearing in mind that settlement, thermal expansion and loading can and will have effects (though the latter two are probably inapplicable for a pyramid). I don't see the challenge of layout to the observed standards as beyond the means of an early civilization which chooses to devote the appropriate resources. Acroterion(talk) 15:06, 8 October 2012 (UTC)[reply]
We can compare that to the Channel Tunnel. The length of each bore is 50.45 km (per that article). The Institution of Civil Engineers' book The Channel Tunnel (ISBN 9780727719225) p54 says the two bores for the service tunnels (the first to meet) were off by "4mm vertically and 15mm horizontally". -- Finlay McWalterჷTalk 15:10, 8 October 2012 (UTC)[reply]
And here is a very relevant article that was linked in the discussion: Geographical centre of Earth. It mentions Giza and some of the historical claims about the location. 209.131.76.183 (talk) 11:43, 9 October 2012 (UTC)[reply]
The precision of construction is remarkable, but not unearthly. I should note that Thuban was, in 2787 BC, quite a reliable pole star, less than 2.5 arc-minutes away from true north. But by 200 years later it would have been a full degree from the pole, so presumably the people laying the lines of stones would have had to watch its circling quite carefully to come within 4 arc-minutes. I wonder if, at the time, they derided their efforts as a sloppy job, wistfully remembering the stories of the constant pole-star of a bygone age? I assume they had a choice of many stars to watch coming up from the east to use to align the sides going in that direction. The levelling is another question - if it rained on the base of the pyramid, how accurately could you level it based on which way it flows? (Though the Sahara was apparently 'as dry as it is today' by 3400 BC, so maybe they had to flood it by hand?) Wnt (talk) 16:54, 10 October 2012 (UTC)[reply]
Aviation-related question on the humanities desk.
I'm taking the liberty to cross-post, because there may be someone knowledgeable here, who does not usually read the humanities desk. The question is Bob Hoover anectote - Urban legend? If someone has information relevant to the question, please answer at the humanities desk. Thank you. --NorwegianBluetalk 12:23, 8 October 2012 (UTC)[reply]
de-salting urine
In the lab where I work, we sometimes do thin-layer chromatography on urines. Part of the prep is to "de-salt" the urines by adding propan-2-ol to a small amount of the urine, and then freezing these preparations for at least one hour before using them. What I would like to know is:
what does it mean to "de-salt" urine? What's happening?
How does propan-2-ol achieve this? What are its properties that make it work?
Why is the freezing necessary?
I have a decent understanding of chemistry and so replies hopefully don't need to be dumbed down too much! Thank you. Sternenjägerin (talk) 18:00, 8 October 2012 (UTC)[reply]
Desalting is used in DNA extraction techniques. Here and here are very short explanations of why and how it is done. Does that help? --Jayron32 18:10, 8 October 2012 (UTC)[reply]
Found an even better one. This page explains why salt, freezing, and isopropanol are all used in preparation of a DNA sample. I assume most of these techniques are used for Gel electrophoresis rather than TLC, but there is likely a similar rationale. --Jayron32 18:14, 8 October 2012 (UTC)[reply]
It would be easier to answer this if I knew what compound(s) you were trying to isolate. There are many different reasons that could come up. From [16] I see that one reason is that during liquid-liquid extraction, stable emulsions can occur, which "might be overcome by either an increase of the phase ratio (organic/aqueous), or saturation with neutral salts, or freezing of the aqueous phase, or the application of supported LLE (adsorption of the aqueous phase on diatomaceous earth before extraction with water immiscible organic solvent)." Extractions of this type are a bit of an art, devised by trial and error, usually by frustrated postdocs or grad students who will do whatever comes to mind trying to get a procedure to work this week rather than next, which will then be followed religiously (by which I mean, by rote and without critical thought) by what may be literal generations of future researchers. (If you think I'm kidding, you should search "rubidium chloride" sometime) [17]
If the above source is the application you're thinking of, then its role there is very different from in DNA extraction. For DNA, the idea is that when you have a less polar solvent, the highly charged phosphates that make up the DNA backbone will find some nice positive ion someplace to snuggle up with, and bring it out of solution in big white lumps. The excess salt is simply washed out with 70% ethanol later on, because the DNA is huge and won't dissolve in ethanol, especially once you've compressed it up against the wall of a centrifuge tube at high g-forces, but the salt can. But for resolving the emulsion, you're trying to make it so that the bits of aqueous and of organic in a mixture will fuse together. (Actually, emulsions aren't a topic that I understand very well; but you can see from this much that it must be different from what you do to DNA) Wnt (talk) 05:55, 9 October 2012 (UTC)[reply]
Thanks for the answers so far. I had a look at the links provided by Jayron and they didn't really help, because DNA extraction is a very different thing. The TLC I'm doing is for sugars in urine; glucose, sucrose, fructose and such. I'm aware that this is quite a common application, but most of what I've found on the web assumes a basic level of understanding, or just says, "this is what works" without making an explanation as to why. I know that desalting helps give clearer streaks, less 'clumpy' interference I suppose, but wondered if there were also other reasons, perhaps dropping out of solution some compounds that would coelute. I also wondered if propan-2-ol does some deproteinising as well (based on the sometimes rather large pellets after centrifuging). Sternenjägerin (talk) 07:06, 9 October 2012 (UTC)[reply]
Without more details, it's hard to guess what's going on. First hit I got for "desalting urine TLC" mentions drying the urine first (evaporating off the water). There's a huge difference between a salt-sugar-isopropanol mixture with water and one without. Salt will separate a water-isopropanol solution, salt solubility in water and in isopropanol decreases at lower temperatures, freezing water will drive out salt, freezing a water-isopropanol mixture is fractional freezing; Sugars dissolve in isopropanol, salt to a lesser extend. All these may play a role, but without more information, I can only guess. Freezing for at least one hour doesn't make much sense imo, not much can happen when everything is frozen. Slow freezing, partial freezing and cooling down a liquid on the other hand have many uses. If we're talking about a waterless mixture, you may drive out the remaining salt by lowering the temperature and with it the solubility, a better alternative to using cold isopropanol in the first place because that would make the dissolution of the sugars unacceptably slow and you'd get water condensation from the air. Ssscienccce (talk) 13:22, 10 October 2012 (UTC)[reply]
If you can link any of those things you found on the Web that detail the basic procedure it will be a lot easier to figure out what they're talking about. Wnt (talk) 16:36, 10 October 2012 (UTC)[reply]
cells
if a cell under goes cell division every minute how many cells will you have after five minute? — Preceding unsigned comment added by 69.121.183.37 (talk) 19:43, 8 October 2012 (UTC)[reply]
This sounds like part of a homework problem on exponential growth. Is there anything in particular about the problem that you are having trouble understanding? 209.131.76.183 (talk) 19:51, 8 October 2012 (UTC)[reply]
You formula is (C)2i, where "C" is the number of cells initially, and "i" is the number of time increments, with doubling occurring at each time increment. However, note that doubling at that rate can't happen for long, as soon the resources the cells need will be used up and they may also poison (or eat) each other. StuRat (talk) 22:15, 8 October 2012 (UTC)[reply]
Doubling at that rate can't happen at all. Looie496 (talk) 00:57, 9 October 2012 (UTC)[reply]
What if the petri dish or whatever they're in is being supplied with nutrients and toxins are being removed somehow? ←Baseball BugsWhat's up, Doc?carrots→ 03:51, 9 October 2012 (UTC)[reply]
You could keep it going a bit longer that way, but soon the petri dish would overflow, as would the barrels, vats, and tanks you moved them to next. StuRat (talk) 03:58, 9 October 2012 (UTC)[reply]
Correct. If we double the population with each cycle, we end up with over a thousand times the initial population in 10 cycles, a million times in 20 cycles, a billion times in 30 cycles, a trillion times in 40 cycles, etc. StuRat (talk) 21:22, 12 October 2012 (UTC)[reply]
Depends on how long a minute is. You can still calculate 2^x based on a given x. The question seems to be at about a fourth or at the most fifth grade level. μηδείς (talk) 02:48, 9 October 2012 (UTC)[reply]
Bugs & Stu, I am fairly certain Looie meant doubling can't happen at the rate of a minute because mitosis takes on the order of an hour to repeat; one source says (without specifying if they mean time to occur or to repeat) of 8 minutes in a fly embryo and 20 minutes in bacteria. (Hence my cryptic remark as to depends how long a minute is.) Also, the early stages of cell division in human embryos don't include growth, so the many-celled embryo when it implants is the same size as the egg when it is fertilized. μηδείς (talk) 01:48, 12 October 2012 (UTC)[reply]
Unknown flower on Japanese woodcut
This Iwasaki Tsunemasa woodcut is from the Kew site but without ID. Anyone know what it is? It looks like some sort of Peony, but I'd like to be sure. Perhaps someone who reads Japanese...... Thanks Paul venter (talk) 20:38, 8 October 2012 (UTC)[reply]
To save others the trouble, neither TinEye nor Google reverse-image-search yields much of interest for this image, bar its Kew page and some mirrors and Pinterest-pins of it. It seems that the name Honzo Zufu simply means "plants illustrated" (the name of the work from which this illustration comes), and Kew (et al.) simply calls it "blue flowers". -- Finlay McWalterჷTalk 22:23, 8 October 2012 (UTC)[reply]
That sounds cool, how does one do a reverse image search? (BTW, a google search for blue flower is also pointless, and yields mostly falsified images.) μηδείς (talk) 01:47, 9 October 2012 (UTC)[reply]
That's quite cool. I would consider giving you a proper star, if it wouldn't get me excommunicated. I am wondering if perhaps we (1) alread do have a page with a list of resources like http://www.tineye.com/ and http://books.google.com/ngrams/ or (2) if wwe should create one? μηδείς (talk) 02:46, 9 October 2012 (UTC)[reply]
Google also allows a reverse image search, go to Google Images[18] and click on the camera icon. Nil Einne (talk) 06:12, 9 October 2012 (UTC)[reply]
Thanks to both, I figured there had to be something like that. μηδείς (talk) 18:06, 9 October 2012 (UTC)[reply]
Given this hasn't been answered I posted it to the lang desk. μηδείς (talk) 03:44, 10 October 2012 (UTC)[reply]
No luck at the language desk, thanks to Kagetora. It does look somewhat like a peony, but according to our article they are red, yellow or white. Also, the little yellow heads make it look like a member of the Compositae, but peonies are in the Saxifragales. Peonies do have yellow anthers, but they are elongate, not spherical. μηδείς (talk) 06:28, 10 October 2012 (UTC)[reply]
It might still be enlightening to know what the Japanese inscription says. The images at look pretty similar. The blue colour is just artistic licence. Peonies used to be Ranunculaceae and the image does shout that out. Paul venter (talk) 20:46, 10 October 2012 (UTC)[reply]
I don't think you can suggest the blue color is just artistic license, given the book is a medicinal, and the text according to Kagetora's comment at the lang desk mentions the blue color. Also, the leaves as depicted are sessile and simple, while the peony's are petiolated and compound. μηδείς (talk) 02:27, 11 October 2012 (UTC)[reply]
KägeTorä interprets it as 'purple' rather than 'blue' - so perhaps the blue colour was more of a printer's gremlin than a colour that reflected reality - herbals get that a lot. Paul venter (talk) 06:13, 11 October 2012 (UTC)[reply]
(Yes, my previous post said "blue color' before KageTora had offered his reading of murasaki as purple.)
Japanese splits up color space slightly differently from English. The term aoi covers a range including colors we consider blue and green. That murasaki is usually translated as purple doesn't necessarily mean it doesn't also cover indigo, which is the word I would use to describe this flower's color if I wanted to be more specific than blue. (Indeed, ROYGBIV has the two colors indigo and violet that overlap in the purple range, while Russian, for example, doesn't even have a single basic word that covers the blue range in the English sense. It has голубой, (goluboi) light blue, and синий, (sinii) (darker) blue, which are considered separate basic colors in the way we consider green and yellow separate basic colors.) μηδείς (talk) 17:01, 11 October 2012 (UTC)[reply]
That is all truly interesting - if only we knew what the flower was! Paul venter (talk) 17:19, 11 October 2012 (UTC)[reply]
My expert on NE N. Am. plants agrees with my opinion that it looks like a member of the compositae but has no better guess. The big problem is that we can't see into the center diagnostic part of the flower to tell if the yellow things are sexual parts (anthers) as they would be if it were a peony, or actually little separate flower heads in a big composite like they would be in a daisy or a mum. The leaves, which are depicted as simple, dentate, opposite and sessile, rule out a peony.μηδείς (talk) 01:20, 12 October 2012 (UTC)[reply]
I asked at a forum in Japan and got this database link. See this image. It's a different version, but the description is same. 千葉 is Chiba. 鋸 is a saw or this might be Mount Nokogiri (Chiba). 紫 is purple. The sentence could be "Found purple one at Mount Nokogiri, Chiba" or "Found saw-purple one in Chiba". 紫色淡紫色ノ物 means "Purple and pale purple colored one". The other flowers on the pages before and after are poppies. Someone in the forum said it was P. somniferum var paeoniflorum. The Japanese name of the flower is 牡丹芥子/peony poppy. I'll call u-tokyo and asked for details. If they are kind and answer my questions, I'll post the information here. Oda Mari (talk) 05:30, 12 October 2012 (UTC)[reply]
I had found a database at National Diet Library before I asked at the forum, but could not find the image as there were too many images. As I knew which volume to look up, I found this one, the same version of ours. I noticed the description was different. It says 鋸歯/serrate leaf. I think this description is the correct one. This page says it's piony poppy. The flower is definitely P. somniferum var paeoniflorum. According to the description of the book, it's not wood block print, but a manuscript (1844). As for u-tokyo, I have to e-mail for inquiries, but I don't think the inquiry is needed anymore. Oda Mari (talk) 08:17, 12 October 2012 (UTC)[reply]
Lovely bit of detective work! Poppies before and after our plate surely clinch the ID. Thank you for the effort and interest! Do wish I could read Japanese! Paul venter (talk) 09:08, 12 October 2012 (UTC)[reply]
Ah, yes, brilliant, it is quite obvious from the leaves and petals it's a poppy. The little yellow spheres inside the flower are quite inaccurate depictions of the ring of elongate yellow anthers. But still very interesting. μηδείς (talk) 17:46, 12 October 2012 (UTC)[reply]
Artistic licence, perhaps, and the ability to read Japanese........Paul venter (talk) 21:25, 12 October 2012 (UTC)[reply]
PSYCHOLOGY AND SCIENCE BREAKTHROUGH QUESTION
this is half psychology and half science breakthrough question. the psychology question follows.
is it possible to build time viewing machine to very distant past by finding a shorter path light takes around massive objects and following short cut catch up with it and view very distant path through powrful megascopes?
secondly isn't your opinion of the science validity of this question greatly improved by reference to this stupid meme - http://www.quickmeme.com/meme/3r8eie/ - which is far less useful, as it does not describe how someone might get the distant past image back to earth to view. whereas, finding a tortuous light path that ends up near us is much more likely.
followup question:
- is anything shiny enough and millions of lightyears away to reflect even a single photon from earth back to earth, today? if so, then is even a single photon hitting earth on average of once per year that shows earth from the dinosaur era? — Preceding unsigned comment added by 80.98.245.172 (talk) 21:59, 8 October 2012 (UTC)[reply]
Warning: Many consider using all uppercase letters here to be a capital offense. StuRat (talk) 22:06, 8 October 2012 (UTC) [reply]
A photon would be not so much reflected by a mirror as deflected around a massive object, like a black hole. It's possible a few "dinosaur photons" from long ago might return to Earth, however, the problem is the signal to noise ratio. That is, how would we know which photons are from dinosaur Earth, versus the huge number of photons from other sources ? And, even if we could identify them all, I doubt that there would be enough to see anything from them. StuRat (talk) 22:10, 8 October 2012 (UTC)[reply]
(ec)First, please don't post in all caps; it is the internet equivalent of shouting and is generally harder to read (I have altered the text to lowercase). For the first question, yes, in principle, a telescope can act as a "time viewing machine", and if you throw out engineering limitations, a telescope plus a distant mirror could let you observe Earth millions of years ago. However, you can't see anything prior to the point when the mirror was constructed, so unless we find giant space mirrors floating around, we can't actually see anything on Earth before now (though we could allow our descendants to see us now, or as soon as we build said mirror). A gravitational lens could, in principle, act as such a mirror, but there are no suitable candidates (plus all those engineering limitations re-emerge as soon as you want to talk about actually doing something). For the last, there is no super-shiny space mirror out there, so far as we know, but it wouldn't be unreasonable to expect photons to return after some arbitrary number of usual reflections, etc -- though anything meaningful will be long-since lost in the noise. — Lomn 22:16, 8 October 2012 (UTC)[reply]
Quibble: You could view things reflected from Earth, at twice the age of the distant mirror, all engineering considerations aside. StuRat (talk) 22:24, 8 October 2012 (UTC)[reply]
Since the Apollo moon landing program, scientists have been able to see backward about 2.6 seconds at least so far as determining that a laser beam was transmitted to bounce off the [[Lunar Laser Ranging experiment] installed then on the Moon. In principle, if not in practice, if a flat mirror many kilometers in diameter were built on the Moon, couldn't we see images of what happened 2.6 seconds ago? A large enough mirror on the Moon might allow a Hubble quality scope in near Earth orbit to see an object 400 meters across on the Earth 2.6 seconds ago, judging by an article on aiming Hubble at the Moon, and doubling the distance.. I expect the cost of such a mirror to provide even 400 meter resolution of events 2.6 seconds ago would be staggering, but (again only in principle) couldn't a mirror farther away allow a 1 hour or 1 day (or any particular period) retrospective view of Earth? How big would the mirror have to be for the system to function? Would making the mirror concave like a long focal length telescope mirror help? A quick calc implies that with Hubble, if the mirror were 1000 times the Moon's distance, it could see 2600 seconds (43 minutes) into the past, but the resolution would only be 400 km. A bigger telescope could improve the resolution. Just sending the telescope to the remote point to look back at Earth would likely be cheaper than putting a giant plane or convex mirror far from Earth. A more practical way to view our past (fuzzily) is when a distant spacecraft looks back at Earth , like Pale Blue Dot when Voyager 1 took a picture (if a pixel is a picture) and sent back an image of how the Earth looked 11 or so hours earlier. If we built a humongous and impractical mirror in space to reflect back light to a nearby star, it would in principle let them see themselves as they were, if they built an impractically large telescope. Such reciprocity would get around the need to wait eons for our own space telescope to get lightyears away from Earth. Edison (talk) 00:28, 9 October 2012 (UTC)[reply]
October 9
Yearly hours of sunlight at different latitudes
Do I understand rightly that all locations worldwide receive an equal number of hours of sunlight in a year? I'm ignoring clouds for the moment, along with shade from mountains and other factors that vary from place to place at the same latitude. I found this discussion, but (1) I can only read part of the page; and (2) the guy who drew the diagram seems to be saying that night and day are also equal, and I know that's wrong because the Sun is a disc, not a point. Nyttend (talk) 02:46, 9 October 2012 (UTC)[reply]
It's almost true. If the Earth's orbit around the sun was a perfect circle, every point on Earth would see the sun exactly 50% of the time, averaged over the whole year. But the Earth's orbit is actually slightly elliptical, so there are small differences. I am ignoring the disk-shape of the sun -- that's a very small factor, along with some others such as the curvature of the Earth. Looie496 (talk) 04:11, 9 October 2012 (UTC)[reply]
Also note that this doesn't mean every place on Earth receives the same magnitude of sunlight, as, near the poles, the Sun is always low on the horizon, and hits at a shallow angle, after going through more atmosphere. So, a solar panel at the poles is not very useful, compared with the equator. StuRat (talk) 04:16, 9 October 2012 (UTC)[reply]
lightning
Does lightning go through closed windows? Is it safe to be on a computer during lightning? If lightning strikes a body of water, how far away does it travel? — Preceding unsigned comment added by 173.22.168.103 (talk) 02:49, 9 October 2012 (UTC)[reply]
Our Lightning strike article may be of help here. Regarding your particular questions, though glass is a good insulator, the window frame and surrounding structure will probably not be, I doubt that shutting the window will reduce the risk, but you are almost certainly safer inside a building than outside. As for computers, anything connected to the electricity mains or to a phone line has a chance of being zapped by a strike outside being conducted through the wires - though it is probably more likely to damage the computer than the user. As for lightning strikes onto water, I'm not sure. In any case, though lightning is dangerous, there are precautions that can be taken, and fatalities are relatively rare. AndyTheGrump (talk) 03:50, 9 October 2012 (UTC)[reply]
The danger of being on a computer is mainly to the computer. If your computer is plugged into a power strip with a surge protector, there shouldn't be much risk, though. If your computer isn't plugged into a power strip, it ought to be, if you value your computer.
I don't think a urgesurge protector would do much good if your house was struck by lightning, but that's rare, as was previously said. StuRat (talk) 04:17, 9 October 2012 (UTC)[reply]
Lightning could strike a pole-mounted transformer that leads to your house. A while ago, some contractors were working near such a transformer. An accident caused the transformer to short out, sending a surge down the line and into my friend's house. It fused the switchboard and power outlets, and basically destroyed everything that was plugged into a power outlet, regardless of whether it was switched on or off. I don't think that a surge protector would have made a hair breadth's difference in this case. Plasmic Physics (talk) 11:23, 9 October 2012 (UTC)[reply]
The one thing that people should avoid seems to be the old landline telephone. According to this, on average one American dies each year from a lighting strike on his telephone line. Non-lethal effects include ruptured ear drums and electric burns. Running the telephone wires on utility poles instead of under the ground may be a risk factor. Ssscienccce (talk) 14:02, 10 October 2012 (UTC)[reply]
While it is in the sense that the pole is more likely to be struck directly, underground lines are at just as much of a risk in the same way that underground plumbing can transmit lightning (it's also best to avoid taking showers/baths during thunderstorms). Ks0stm(T•C•G•E) 03:34, 11 October 2012 (UTC)[reply]
I was thinking that once it went underground, the voltage would be lowered considerably, making it less likely to travel through the air again from phone to person. With plumbing people can be in direct contact with both drain and water pipe. Mains voltage would be enough to kill them. Ssscienccce (talk) 04:15, 13 October 2012 (UTC)[reply]
If I am here and I am then being on the Earth I'm traveling +- 1000mph. Traveling around the Sun I'm traveling +- (way fast) On through the Milky Way and so forth to the outer limits. Then where are we? Where are we going and how fast? Shalom, Tim Jagoe — Preceding unsigned comment added by 108.249.61.251 (talk) 02:52, 9 October 2012 (UTC)[reply]
"where are we?" Relative to where? Neither position or speed have any absolute value. They can only be expressed in relation to something else. AndyTheGrump (talk) 03:35, 9 October 2012 (UTC)[reply]
Andy's point is the entire point of the various "Theories of Relativity", especially Special relativity, but even it's predecessors Galilean invariance and Newton's third law or its sequel General relativity. All of these theories basically have the same principle: there is no privileged frame of reference. That is, there is no point in the universe which can be considered to be "standing still" against which we measure the motion of other objects, except in a purely arbitrary sense: we define "still" generally from where we, as an observer, is standing, but that choice is arbitrary, and the laws of motion are the same if another frame were to be chosen. Or to put it simply, if I say that I am standing still and you are moving, that is completely identical to claiming that you are standing still and I am moving. --Jayron32 04:18, 9 October 2012 (UTC)[reply]
We are moving at approximately 370km/s relative to CMB. manya (talk) 04:37, 9 October 2012 (UTC)[reply]
domestic cats like killing
Since cats have traditionally been useful for keeping down rode.t numbers it seems likely that we would have encouraged wanton killing. But what'a with them leaving dead animals on the doorstep or similar place for us to find. Are they giving us the food, or simply frequently happen to drop it there by coincidence.
Is it possible that we have encouraged the trait of bringing us food much the way it would bring its own kittens food? Its the only way I can see that they would get anything out of it — Preceding unsigned comment added by 149.135.146.109 (talk) 03:17, 9 October 2012 (UTC)[reply]
If you read Cat#Hunting_and_feeding it has some good information on "presentation of dead animals to owners" as you describe. There's also some links, via the footnotes, to other sources on the behavior, but I think the salient point made in the Wikipedia article is "One poorly understood element of cat hunting behavior is the presentation of prey to human owners." (bold mine) In other words, science hasn't got a firm grasp on explaining the behavior in a conclusive way. I'm sure a dozen people after me will present some unreferenced folky explanation on what cats are doing when they do this, but perhaps someone will come along with some solid references that contradict the Wikipedia article to say that this is "poorly understood". --Jayron32 03:27, 9 October 2012 (UTC)[reply]
Jackson Galaxy might know. For the rest of us, it's pretty obvious that the cat is bringing a present to its owner. Cats aren't pack animals like dogs are, but they do have a sense of a "pecking order". ←Baseball BugsWhat's up, Doc?carrots→ 03:48, 9 October 2012 (UTC)[reply]
And in steps Bugs with an unsourced 'explanation' ;-) Actually, I've heard another, entirely contradictory 'unverifiable explanation' - that cats, having never seen humans catch mice, assume that they are kittens in this respect, and need to be taught how to do it - hence their predilection for bringing home live specimens for us to practice on. The truth is though, that we don't know. If I remember correctly Wittgenstein said that 'if lions could speak, we couldn't understand them' or something to that effect. Felines are different from us, and trying to understand their behaviour in terms of 'why' rather than 'what' may be a futile endeavour... AndyTheGrump (talk) 03:58, 9 October 2012 (UTC)[reply]
Unless you own a cat yourself and watch Jackson Galaxy's TV series, keep your grumpy trap shut. ←Baseball BugsWhat's up, Doc?carrots→ 02:30, 10 October 2012 (UTC)[reply]
I wonder if we selected for it, it if wild cats will do it inately. I wasn't aware that wild cats are very sociable. Even if they are more social creatures than I realised, presenting an alpha with food is quite an advanced social tool! The idea that cats see their owners as a mixture of mother and kitten seemed mire plausible but I was merely hypothesized with no evidence. — Preceding unsigned comment added by 149.135.146.89 (talk) 04:03, 9 October 2012 (UTC)[reply]
I'll go with Bugs here. Specifically, cats exhibit behavioral neoteny, meaning we have selected for cats which maintain kitten-like qualities into adulthood. This is even more true when we have them neutered. Their owners take the role of mother (regardless of gender), unlike with dogs, where the owner is the pack leader. As such, bringing home caught prey to their mother is a way to demonstrate their value and gain approval. I also suspect that people, in the past, have been more wiling to allow a successful hunter to live with them, as that shows the cat is "doing it's job" to keep down the rodent population (very important for those with grain stores). StuRat (talk) 04:11, 9 October 2012 (UTC)[reply]
I'd agree with neoteny being a factor in the domestication of most animals - I'm not entirely sure how true it is of cats though, in that their 'domestication' as pets seems to be relatively recent, and there may have been little selective pressure to change behaviour beyond a willingness to hang around where the humans are - because that is where the mice are to be found. AndyTheGrump (talk) 04:19, 9 October 2012 (UTC)[reply]
But "adult" cat behaviors, which we've now largely bred out of them, would involve them hissing and scratching and biting us, and would get them thrown out into the cold quite fast, if not outright killed. Domestic cats have been around for thousands of generations, which is enough for selection pressures to work their magic. StuRat (talk) 04:27, 9 October 2012 (UTC)[reply]
I haven't tried to work out the answer yet, but I should point out that the African wildcat is what will display evolutionarily sensible behavior; the actions of domestic cats, as pointed out above, may be different. Wildly speculating (which I shouldn't do because there's probably an answer to this one) I'm prone to compare this to the various sorts of gun dogs, pointers and setters and retrievers, which I've seen explained plausibly as caused by a defect in the natural hunting instinct at various points in the process, from the moment the prey is first sighted to the point where it is about to be devoured. Wnt (talk) 06:03, 9 October 2012 (UTC)[reply]
As a long time cat owner (40+ yrs), I suspect that the cats leave the dead animals not as a gift, or as food but the place we find the animal is where the cat got bored of playing with it or eating it and wandered off. 217.158.236.14 (talk) 09:22, 9 October 2012 (UTC)[reply]
Weirdly enough, I just received this in my email: a comic from The Oatmeal. Anyway, it sources a National Geographic and University of Georgia project, called Kitty Cams Project, which studies domestic cats when they're away from the prying eyes of their human owners. I can't vouch for its legitimacy, but there we go. – Kerαunoςcopia◁galaxies 09:37, 9 October 2012 (UTC)[reply]
On a somewhat similar point, I would say you're somewhat lucky when all you find is half of a dead animal (or whatever), far worse when your cat brings in a bird, gets feathers and possibly blood everywhere while playing with it for many minutes while it (the bird) screeches only to get bored of it and leave the half dead bird somewhere and you have to decide whether to kill the half dead bird or let it die naturally. You can of course try to save the bird but unless you're either willing to play the vet bills everytime it happens or continually bother volunteer bird rescue groups there's a fair chance the bird will die anyway, particularly once the cat learns you'll take the bird off it. Worse still when your cat brings in a live mouse or rat, only to find 10 minutes later the cat desperately searching for the mouse or rat. Anyway to get back to the original question, I think this sort of thing highlights why we need to be careful with evolutionary explanations, logically playing with your food to the extent you may lose it is not advantageous particularly when your primary benefit to humans was in catching vermin. Even if this behavior has increased in recent times as catching vermin has become less important and neutering more common, is the fact this behavior still exists reflective of the fact it's not easy to breed out without either negatively affecting learning, other desirable behaviours, or simply suggestive as with most cases, it's likely fairly complicated? Nil Einne (talk) 12:48, 9 October 2012 (UTC)[reply]
That seems of questionable relevence if you don't live in the US. Nil Einne (talk) 03:38, 10 October 2012 (UTC)[reply]
What would be the evolutionary pressure which would breed this behavior out of cats ? How many people would neuter or kill their cat because it did that ? StuRat (talk) 21:49, 9 October 2012 (UTC)[reply]
If I had to take a wild guess (a flagrant Just-so story) I would speculate that a cat that efficiently catches and eats the mouse will get filled up and stop bothering them, but one which plays with it and forgets it will keep going after more. And such a cat, maybe, would get a reputation as a "good mouser" and be preferentially bred. (Leaving the remains where the owners could see probably wouldn't have hurt either) Wnt (talk) 22:56, 9 October 2012 (UTC)[reply]
Another possibility, equally unreferenced but in my opinion more plausible: Cats that "practice" hunting when game is plentiful are more likely to be able to feed themselves when it's not. So if they're not particularly hungry, they "play" with the mousie to hone their reflexes (and may not even eat it at the end).
This one is even somewhat testable — see if hungry cats are less likely to play with their food, and whether cats that engage in this sort of practice become more skilled. --Trovatore (talk) 08:33, 10 October 2012 (UTC)[reply]
This may indeed be more convincing than my scenario, especially when I remember that carnivores tend to be scavengers as well - in the wild, a rotten mouse stashed in a "safe" place might still be food in the future. Wnt (talk) 16:13, 10 October 2012 (UTC)[reply]
As Jackson Galaxy often explains, cats are hard-wired to hunt and kill. That basic fact explains a lot about their behavior. I saw a story recently where some outdoors cats were equipped with small cameras so that observers could see what they were up to. It turns out they were killing a lot more prey than people generally assumed. ←Baseball BugsWhat's up, Doc?carrots→ 02:30, 10 October 2012 (UTC)[reply]
I think it's quite likely in the past when cats were not really seen as pets as such, a cat which keeps losing vermin (particularly if it brings them from further away) rather then killing them would find itself out of favour of any humans it tries to live near them. Whether it would be killed or simply thrown out or have to leave because of the human reaction is largely a moot point; it's very unlikely neutering comes in to it much, remember we are talking about hundreds or thousands of years in the past and when cats weren't seen as pets much. Wnt does have a point that it's not clear whether what the cat was doing would have been appreciated as such. Although it's also worth considering from a results POV, while no one was doing scientific experiments, if humans found the vermin level has not decreased much or perhaps even increased they're far less likely to see a reason to keep cats around then if they found them significantly decreased. And if the neighbours cat (or an old cat) seems to have been far more effective this could also affect the chance of the cat being kept. Of course even lost vermin may die from the injuries, but they generally have a more effective immune system then birds. In fact, it's even possible there would be greater evolutionary pressure on this sort of behaviour for quite a while then stuff like biting. If a cat is helping with the vermin population even if it doesn't really let humans handle it this could easily be more successful then on which does not help with the vermin population but lets humans handle it. In any case, it does demonstrate the point you need to take care when considering evolutionary explainations. Nil Einne (talk) 03:23, 10 October 2012 (UTC)[reply]
Yeah, I don't think we'll get to any real answer unless we come up with more observations on the behavior of Felis silvestris lybica. Wnt (talk) 16:13, 10 October 2012 (UTC) -- hmm, while I didn't see anything naturalistic about it on NCBI, I did stumble across a commercial photo stock image of European Felis silvestris playing with prey. Unfortunately the author isn't credited that I see, so asking him would be a paper chase ... still, there must be people contactable somewhere who have observed these cats in the wild or in zoo-like conditions who can tell us if they play with prey like domestic cats. (though we should be careful of assumptions based on little evidence but presumed resemblance) Wnt (talk) 16:22, 10 October 2012 (UTC)[reply]
I am not quite sure what the mystery is here. Domestic cats are usually not starving. So if they do catch prey, why wouldn't they bring it back to the den just like wild cats do, either to eat later or share with the family? I am allergic to cats. So perhaps I am missing out on their being some other behavior that needs explaining, like the cat pawing you with a bird in his mouth, or doing a little end-zone dance to get your attention? μηδείς (talk) 17:14, 10 October 2012 (UTC)[reply]
They do a strange twitching thing when stalking prey. I attribute this to the effects of adrenaline flooding their system as they try to keep still. StuRat (talk) 15:47, 11 October 2012 (UTC)[reply]
Yes. Cats are instinctive hunters. It doesn't much matter if they're hungry or not. They do what they do because it's programmed in them. ←Baseball BugsWhat's up, Doc?carrots→ 05:12, 11 October 2012 (UTC)[reply]
Scale of eyes
Our eyes detect light and we can determine size and scale. If there were beings whose heads were as big as the sun would their eyes be able to see as detailed as ours? The same amount of photons would be shining on them?GeeBIGS (talk) 05:21, 9 October 2012 (UTC)[reply]
They probably could not see things as small as we can. We can't make out items as finely as a spider can. I think the issue is that larger lenses cause larger distortions, making it more difficult to focus on smaller objects. Now, what I'm unsure of is if our eyes could be much better for viewing small objects, if there was evolutionary pressure for them to be so. I'm quite nearsighted myself, and, without contact lenses, I can make out very tiny objects, like the individual dots on a printed picture, but only if my eye is within a few inches (that's too close for binocular vision to work). So, perhaps a nearsighted Sun-sized creature could see more detail at very close range, but not at the distances of planets. StuRat (talk) 06:55, 9 October 2012 (UTC)[reply]
I'll second Stu's experience regarding distortion. I as well can make out small details without my contacts; they distort my close vision for the sake of giving me decent distance vision. Optical aberration has some details which may help as well. --Jayron32 18:18, 9 October 2012 (UTC)[reply]
I don't really understand the question. Is it asking whether a head exactly like ours except scaled up to the size of the sun would be able to see things a fraction of an inch in size? Or whether it would be able to see things that are scaled up to an equal degree? Looie496 (talk) 18:50, 9 October 2012 (UTC)[reply]
I took it the first way. StuRat (talk) 21:41, 9 October 2012 (UTC)[reply]
The first way. Stu you seem to contradict yourself, could you please clarify?GeeBIGS (talk) 00:09, 10 October 2012 (UTC)[reply]
That is, "whether a head exactly like ours except scaled up to the size of the Sun would be able to see things a fraction of an inch in size". To that I say no, although they could see smaller things close up (but not that small), than if focused on distant planets. StuRat (talk) 00:44, 10 October 2012 (UTC)[reply]
If you simply scale up everything in the eye, there's no way it could detect tiny things, because scaling up the photoreceptor cells in the retina would mean they would have vastly larger receptive fields. Looie496 (talk) 02:05, 10 October 2012 (UTC)[reply]
Is it possible to wire to a spiders brain and see through its eyes like a spy camera?GeeBIGS (talk) 04:30, 10 October 2012 (UTC)[reply]
I don't know, but it would be simpler to mount a camera on the spider. We have cameras that fit into the human bloodstream, so a large spider would easily be able to carry one. Nyttend (talk) 20:08, 10 October 2012 (UTC)[reply]
I suspect that a spider is extremely nearsighted, as they need to see their prey when they approach it, not things on the other side of the room. So, it would be useless as a spy camera. StuRat (talk) 15:43, 11 October 2012 (UTC)[reply]
Can anyone do this?
Does anyone know how to put his little toe on the second toe?
I can't, at present, but perhaps could if I exercised those muscles. StuRat (talk) 07:17, 9 October 2012 (UTC)[reply]
Ha, what a neat trick! but aren't you counting from the wrong end, it crosses the 4th toe surely. I'm off to practice that. Richard Avery (talk) 14:00, 9 October 2012 (UTC)[reply]
I couldn't, but I have small, stubby toes. My wife could do what's in that video easily. She's got toes she could play piano with. People have different feet. --Jayron32 16:52, 9 October 2012 (UTC)[reply]
My toes are quite long, but they don't move like that, at least not on their own. Presumably this is because the muscles needed to do such movements aren't well developed in my little toes. StuRat (talk) 21:40, 9 October 2012 (UTC)[reply]
Some muscular control is also innate and not that trainable. Some people can curl their tongue and others cannot; some people can wiggle their ears and others cannot. I don't know that there's an explanation or mechanism as to why not, but tongue rolling or tongue curling (two different tongue movements) is one of those "you can do it or you can't" things, and I'm not sure it is trainable. Our article on tongue rollings states that it is an "intrinsic" property of the musculature of the tongue, but also says that it has no demonstrated genetic component. I'm not sure how to resolve that in my mind (if something is inborn, but not genetic, what does that mean?!?) but it isn't a trainable skill. --Jayron32 21:58, 9 October 2012 (UTC)[reply]
You'll want to apply to study prana-bindu muscle technique which allows one "to bend the last joint in her little toe while remaining otherwise motionless" at a Bene Gesserit school. μηδείς (talk) 02:27, 10 October 2012 (UTC)[reply]
Nah, I'm already the Kwisatz-Haderach, so it's pretty pointless messing around with amateur stuff like that. --Jayron32 04:29, 10 October 2012 (UTC)[reply]
I am pleased to note that not merely do we have an article on Kwisatz Haderach, but it leads me to the actual basis of this in the Kefitzat Haderech. (Though it fails to connect this with the story of Al-Buraq, which would be more appropriate to the novel's Islamic theme) Wnt (talk) 16:33, 10 October 2012 (UTC)[reply]
Oh, that's brilliant. I knew that Bene Gesserits were the daughters of the Jesuits (under whom Herbert studied) but didn't know this too had a real-world antecedent. The novel is far more ecumenical (Orange Catholic, Zen-Sunni) than just Muslim. There are even real live Jews in Heretics and/or Chapterhouse. μηδείς (talk) 02:20, 11 October 2012 (UTC)[reply]
Real image?
What is this substance? The image is in a science section, so I'm guessing it something real but would like to know what. Thanks. Dismas|(talk) 11:03, 9 October 2012 (UTC)[reply]
That link takes me to a mosaic of 24 images. Which one are you talking about? Rojomoke (talk) 12:39, 9 October 2012 (UTC)[reply]
if you mean the first image, with the animation, I believe I've seen it before in videos of a Japanese guy making miniature, fake food. It came in a kit that you had to mix all the bits together, then form the food. It's called "Konapun". — Preceding unsigned comment added by 217.158.236.14 (talk) 12:59, 9 October 2012 (UTC)[reply]
Sorry. I thought it would be a direct link. I'm talking about the 14th image. I get a grid of images four across. In which case I'm talking about the second column, fourth image down. The two hemispheres. Dismas|(talk) 14:08, 9 October 2012 (UTC)[reply]
It is a computer animation. I believe it to be made with Autodesk 3ds Max. I don't know what it is supposed to be achieving.217.158.236.14 (talk) 14:13, 9 October 2012 (UTC)[reply]
Okay, thanks. I wasn't sure what with the poor quality of the image. Dismas|(talk) 20:56, 9 October 2012 (UTC)[reply]
Resolved
Microwave oven question
At my place of work, our (very old) microwave oven is acting strange recently. Sometimes, the turntable will begin turning and the microwave sound like it is running when the door is opened (after having stopped/not been in use). Some of my coworkers are wondering: Could a microwave oven that's on while the door is open be dangerous, perhaps leaking radiation? If so, is it an amount of radiation to be worried about? Thanks! -- 143.85.199.242 (talk) 19:34, 9 October 2012 (UTC)[reply]
Don't even think about it any further, just trash the oven immediately. Roger (talk) 20:03, 9 October 2012 (UTC)[reply]
And unplug it until you can have it serviced or disposed of. On the plus side, if it's just an issue of the door switch sticking closed, that ought to be easy and cheap to fix. Just cleaning the switch might do it. StuRat (talk) 20:27, 9 October 2012 (UTC)[reply]
Ugn, not even worth considering, bin it and get a replacement, it's a potential health hazard. Tell them either buy a new unit for $150 or risk a law suit.Vespine (talk) 23:12, 9 October 2012 (UTC)[reply]
$150 would be a premium version. The cheap one you linked to runs $30-$40 in the US. I actually prefer the cheap ones, though, as it's much quicker to turn two dials than to navigate through menus to try to get the darned thing to turn on. One thing I'd prefer, though, is if they don't have those levers you have to hit to get them to open. Those can stop working if they get dirty. I prefer a big handle you can yank open. StuRat (talk) 01:14, 10 October 2012 (UTC)[reply]
Most decent microwaves with digital controls have a 1 minute or similar button meaning there's no need to navigate any menus. In fact most don't have menus for normal usage, even if you don't want to use the 1 minute button, simply push the buttons for the time and push start. One big advantage with fancier microwaves is you can get one with an inverter meaning you have less problems when using it at non full power. Nil Einne (talk) 03:44, 10 October 2012 (UTC)[reply]
You've hit on a pet peeve of mine. To get the quality item, I often have to accept unwanted electronics. For example, I'm fine with manual adjustments on my car seat, except that I'm often limited to just forward/back and maybe tilt. If I want additional degrees of freedom, like an up/down control, then I not only must accept those additional features being controlled by motors, but the basic features, as well. StuRat (talk) 06:56, 10 October 2012 (UTC) [reply]
Can human nature evolve, and if it does evolve, can humans understand earlier humans thoughts millions of years from now?
Can human nature evolve, and if it can and does evolve, can humans understand earlier humans thoughts and motives and desires millions of years from now? 140.254.226.212 (talk) 19:38, 9 October 2012 (UTC)[reply]
Please see the top of the page where it states "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." This isn't the correct venue. --Jayron32 19:41, 9 October 2012 (UTC)[reply]
I'm not sure what Jayron's problem with this Q is, looks perfectly valid to me:
1) Can human nature evolve ? Yes, personalities, willingness to cooperate with others, tendency towards violence, etc., are all aspects of human nature with genetic components. As such, they can evolve just like any other attribute, provided there is sufficient evolutionary selection pressure for them to do so. This means that the ability of people to survive and reproduce must be affected by these attributes.
2) As far as future human's understanding us, I don't see a problem there, as long as we leave behind records of our motivations. It's a bit harder when archeologists look at ancient humans, who lacked writing. You can get some clues, though, such as whether they buried the dead with important items or just tossed them into a hole. StuRat (talk) 20:26, 9 October 2012 (UTC)[reply]
Yes, all we need to do is preserve Wikipedia, including all of the historic versions of the pages. There is then a continuous link from the present to the far future, making it easy to decipher ancient texts. Count Iblis (talk) 20:43, 9 October 2012 (UTC)[reply]
The second question is indeed unanswerable. To illustrate, it is possible that future humans will be exactly like present humans, by accident or design, in which case they can understand. But it is also possible that future humans will live in a dictatorship so appalling that the mere conception of being "free" causes one of them to immediately fall over dead by genetic design, in which case they cannot understand. Wnt (talk) 23:20, 9 October 2012 (UTC)[reply]
To give a less ridiculous scenario, humans and chimps are separated by "millions of years". Can you understand a chimp's thoughts and desires, and do you think a chimp could understand ours? The Aztecs are separated from us by 600 years; they considered it an honor for their living, beating hearts to be ripped out of their chests and sacrificed to the gods. Do you understand them? The Taliban are living in our own time, and they think shooting a 14-year-old girl in the head is OK. Do you understand them? (I do understand the Taliban's motivations, but many people don't; they resort to idiotic cop-outs like "they're just evil", "they're just crazy", or "the devil made them do it", which is essentially equivalent to saying "I can't understand X; therefore, nobody alive today can understand X, and nobody who will ever be born will understand X") --140.180.242.9 (talk) 22:30, 10 October 2012 (UTC)[reply]
I understand the Taliban's motivation as far as wanting everyone who disagrees with them to be afraid to speak up. However, they don't seem to have considered the negative PR implications of murdering children. Not the way to broaden their base of support. StuRat (talk) 15:39, 11 October 2012 (UTC)[reply]
Genetic bottleneck from the KT and Permian mass extinctions
Can one calculate that there were mass extinctions about 65 and 250 million years ago using only the data from genomes of modern animals? Count Iblis (talk) 20:36, 9 October 2012 (UTC)[reply]
I think in principle it should be possible: the signature would show up as large numbers of species-pairs having their last common ancestor around 65 or 250 million years ago. To make it work, though, techniques for genetic dating would have to be improved, and the genomes of a lot more species would need to be sequenced. Note that this not the sort of bottleneck that is normally discussed -- the normal kind is where the number of individuals in a species becomes very low for some period of time. The technique for detecting that is quite different from the one I just gave. Looie496 (talk) 21:50, 9 October 2012 (UTC)[reply]
The method you are referring to is the molecular clock. The problem you'd run into, besides its general inaccuracy, is that few lineages date to the boundary itself. The Galloanserae date to well before the KT boundary, and songbirds to maybe 15 million years after. This paper shows most placental orders predating KT.[19] And there is no common protein or gene that evolved at, was selected by, or which links all the survivors of those events. I'd be surprised, if you knew what you were looking for, and had huge resources, if some statistical correlations couldn't be teased out of the data. But the chances of stumbling across such an event unless you already knew what you were looking for based on other evidence? μηδείς (talk) 02:24, 10 October 2012 (UTC)[reply]
DermaWand®
I've watched an informercial selling a dermatological device which claims to do all sorts of wonderful things for your skin, including reversing signs of ageing. Not that I'm in the least interested in using this device, but it does raise some questions. In the informercial, it was noted that during opperation, the device produces a scent associated with an electical storm, which can only mean ozone. Ozone is highly oxidising, which has the opposite effect of rejuvenation. What is really going on, is the effect of skin exposure to ozone negligible, is it cummulative, is it longterm. This reminds me of Venetian ceruse, on account it it causing a positive feedback loop: using it damages your skin, the more your skin was damaged, the more you used it to cover up the damaged skin. Plasmic Physics (talk) 00:28, 10 October 2012 (UTC)[reply]
I wouldn't expect ozone to have much effect on your skin, since it's covered with a layer of dead skin. An exception would be for someone who just had a seriously chemical peel. Your lungs, on the other hand, could be damaged by a high concentration of ozone. StuRat (talk) 00:41, 10 October 2012 (UTC)[reply]
Hmmm, let's begin by trying to find out what it is. "DermaWand is a condensed version of the exact same technology found in large commercial high frequency machines used by skin care specialists all over the world for 40 years ... stimulates and rejuvenates by sending out a gentle stream of low level micro-current impulses up to 168,000 cycles per second, imitating hundreds of tiny fingers that massage your skin ... helps improve circulation bringing oxygen and vital nutrients to your skin's surface. The gentle micro current also has a thermal effect on the skin s surface, helping the skin look more toned and tight, smoothing out the appearance of fine lines and wrinkles. Plus DermaWand oxygenates by giving off enriched oxygen that cleanses and purifies, helping breathe new life into your skin's surface. "[20]
Hunting for "high-frequency" "skin" "dermatologist" on Google yielded [21]"investigated the skin rejuvenation effect of dual-frequency ultrasound, with frequencies of 3 and 10 MHz, which has the ability to modulate both MMPs and HSPs. It was shown that such waves can significantly improve different visual appearances of ageing skin. This safe, non-invasive method yields results that are not as marked as those shown by injecting of fillers, but can be successfully used by subjects with a broad spectrum of visual skin ageing problems, which have to be treated simultaneously." This in the open access but never heard of before by me Journal of Cosmetics, Dermatological Sciences and Applications, so I'll present this more as a statement of their POV than as fact until I know more. The most applicable source from their introduction is something from Med Hypotheses [22] which... is less than persuasive. But the way the data is presented, measuring skin a week after the last of 8-12 biweekly treatments, and the data they present, suggesting at least a short-term improvement, doesn't look unreasonable. Now the question is whether we can find enough evidence to inform us about this treatment's effect in any longer term... Wnt (talk) 00:43, 10 October 2012 (UTC)[reply]
To my surprise, there's more about this at NCBI: [23], PMID 21332912, PMID 21284234, PMID 21283035, PMID 20115948, PMID 19204844. Some of the references later on the list (older) sound more serious. I'm mixing two different high-frequency treatments - radio frequency and ultrasound - because I'm still not sure which the "wand" is, if either. The gist appears to be to heat the skin, damage collagen fibers, have larger new filaments reform to produce a tighter/less wrinkled look. There might be something to this; there's not much of a theoretical reason why you can't rejuvenate wrinkled skin because there's probably only recent cultural selection against it. Wnt (talk) 00:54, 10 October 2012 (UTC)[reply]
There's an "Ozone Cleansing Beauty Device (personal high frequency)" marketed with all kinds of claims "a versatile handheld esthetic tool that uses ozone / o3 which has three oxygen atoms that is power to sterilize, detoxify, deodorize and whiten your skin.Ozone Cleansing Beauty Device gives you a refreshed feeling and has a powerful function for reducing inflammation, reducing pain, balancing the pH of the skin. Moist importantly, Ozone Cleansing Beauty Device's high frequency current has an antiseptic effect on the skin that will detoxify bacteria caused by acne breakouts". Maybe the same circuit inside but aimed at a different audience? Ssscienccce (talk) 14:58, 10 October 2012 (UTC)[reply]
Depends what you mean by shelf life. If you leave one on the shelf for 3 years it'll be flat as tack, but roughly 80% of them will survive and will be usable after recharging. Greglocock (talk) 01:06, 10 October 2012 (UTC)[reply]
...provided they don't freeze and split open. StuRat (talk) 01:08, 10 October 2012 (UTC)[reply]
The shelf life is strongly dependent on temperature. It's hard to get good data, but there are two mechanisms that lead to reduced performance while on the shelf: gradual deterioration and self discharge. When any lead acid battery is substantially discharged, it's capacity sharply drops from then on. The general rule of thumb is that both gradual deterioration and self discharge double in rate for each 10 degrees C increase in temperature. The impact of self discharge can be eliminated by recharging - once each 3 months is the recommedation. If this is not done, expect the battery to be ruined within a year at ordinary sorts of mediteranian climate temperatures. However, there is another life-affecting mechanism - batteries will only last a certain number of charge-discharge cycles.
How long the battery will last does indeed depend on just what you mean by shelf life. My comments above are applicable to defining end of service life as the capacity reduced to 80% of rated value.
The following discussion has been closed. Please do not modify it.
(All this discussion really belongs on a talk page, not here, but you have no screen name and a dynamic I/P, so you have no talk page to post to. You should have posted any criticism of me on my talk page, not here, so this discussion could take place off the Ref Desk. I've moved it there now: User_talk:StuRat#Detroit_weather.) StuRat (talk) 19:09, 10 October 2012 (UTC)[reply]
The shelf-life will vary depending on the battery and the conditions it is exposed to. If your bettery is well-marked (some cheap ones aren't) you should be able to look up the manufacturer, and they may have a data sheet available. It will outline things like discharge rate over time, effects of different charging voltages and cycles, and expected lifetime under different conditions. 209.131.76.183 (talk) 13:52, 10 October 2012 (UTC)[reply]
They are by Werker. I don't have a way to recharge them, at present. Bubba73You talkin' to me? 01:26, 11 October 2012 (UTC)[reply]
Amphetamine good for children, bad for adults?
According to a recent NYT article, doctors are now considering amphetamines as good for all kids in low-income, poorly funded school districts, not just some special group who show the "reverse effect" or whatever. [24] But although I still remember it as the new drug that some kids at college used to stay up on finals week, methamphetamine is more demonized than ever, an addictive scourge that leaves people batshit crazy, worn out and used up, missing teeth. Is there any way to make sense out of this, to say whether amphetamines are good or bad, or explain when they're good and when they're bad? Is it age of the user, impurities in the preparation, or is the explanation actual, literal transsubstantiation at the tip of a Licensed Doctor's pen? Wnt (talk) 01:10, 10 October 2012 (UTC)[reply]
Yes, there is a way to make sense of it. The brains of children are neurochemically different in some ways from the brains of adults -- in particular the dopamine system, which is targeted by drugs like amphetamine and Adderall, seems to be more active in children. Basically if you see an adult who is addicted to amphetamine or another dopamine agonist, that adult will act in a number of ways like a five-year-old: impulsive, hyperactive, etc. So it is plausible that drugs that act on the dopamine system will have different effects on children than on adults. I'm not asserting that it is true, just that it is plausible. Looie496 (talk) 01:59, 10 October 2012 (UTC)[reply]
(edit conflic with above) I don't think we need to theorize about differences between child and adult brains. There are plenty of adults who are prescribed amphetamines too. The issue's very similar to the recreational abuse of other prescription drugs (vicodin, etc.). A trained medical professional can decide when it is likely that the benefits of a given drug will outweigh the potential costs, and can proscribe the dosing. When taken recreationally, people often take more than a doctor would proscribe, on a less regular schedule, and don't monitor for potential side effects. Though demonized as a recreational drug, Methamphetamine can be prescribed. As I understand it there are some issues with dependence, but the side effects aren't particularly bad when taken in a controlled manner. As you suggest, it probably helps that it's being made by drug companies instead of gangsters (residual hydroiodic acid isn't particularly good for you). The infamous meth mouth, while probably partly due to the drug itself (similar effects are seen to a much lesser extent in people prescribed amphetamines), is probably more a result of the poor diet and dental hygiene of most meth addicts. Buddy431 (talk) 02:10, 10 October 2012 (UTC)[reply]
And that's not to say that there aren't side effects that can occur when amphetamines are taken under a doctor's supervision: cardiac problems, possible psychosis, etc. There are some countries where amphetamines are illegal under all circumstances. Canada briefly banned Adderall in 2005 due to possible risk of sudden death from cardiac events. But again, when taken at therapeutic doses, especially under the eye of a doctor, these side effects can be monitored, and at least in theory, the benefits of the drug will outweigh the risks. Canada later allowed it to be prescribed again, figuring that the benefits to many people with ADHD outweighed the slight cardiac risks. Buddy431 (talk) 02:32, 10 October 2012 (UTC)[reply]
Wouldn't kids be more at risk of addiction than adults, precisely because their dopamine system is more active? 24.23.196.85 (talk) 03:19, 10 October 2012 (UTC)[reply]
Most amphetamines - including methamphetamine in many of its common forms - are Schedule II Controlled Substances in the United States. This means that, according to 21 USC § 812[25], "The drug or other substance has a currently accepted medical use in treatment in the United States or a currently accepted medical use with severe restrictions." This specific legislation has been in effect for several decades, and the classification of methamphetamine has not changed in a very long time (1970, and 1971 in other forms). So, there's nothing to be confused about: methamphetamine is widely recognized as a very seriously potentially harmful controlled substance that also has certain useful medical properties. There's no conundrum. In fact, if you read any of the literature promoted by the Department of Justice's Drug Enforcement Agency, it's actually fairly progressive in its stance: these drugs are controlled because they have potential to do harm. The Methamphetamine fact-sheet states clearly: "it has a high potential for abuse and limited medical use. It is available only through a prescription that cannot be refilled. Today there is only one legal meth product, Desoxyn®. It is currently marketed in 5-milligram tablets and has very limited use in the treatment of obesity and attention deficit hyperactivity disorder (ADHD)." Note the critical distinction between illegal and controlled. And even these two descriptions have absolutely nothing to do with whether the substance is good or bad. If you need help differentiating good from bad, chances are very high that you will never get an answer from the DEA, or from a doctor, or from the reference desk. Perhaps you should consult our article on the philosophical analysis of good and evil. Nimur (talk) 03:37, 10 October 2012 (UTC)[reply]
This is a well-written and respectable answer ... except that it conflicts with the initial article saying that it is now being used on kids without ADHD. Wnt (talk) 16:26, 10 October 2012 (UTC)[reply]
The article Attention Disorder or Not, Pills to Help in School, mentions Adderall. Adderall is not methamphetamine. According to the United States Food and Drug Administration's Adderall (R) CII fact-sheet, "ADDERALL® is indicated for the treatment of Attention Deficit Hyperactivity Disorder (ADHD) and Narcolepsy." In other words, it may apply to medical treatment for "kids without ADHD." In fact, only a qualified medical professional would know whether it is applicable; and only a qualified legal professional would know whether it is legal; but you can peruse the many pages of public information made available by the FDA and by the drug vendor to inform your own opinion about it. Now, whether I would personally trust a doctor who prescribes this medication is a moot point; (I wouldn't); but again, despite a bit of journalistic sensationalism, there's no clear indication that the medication is being used or marketed in a way contrary to applicable regulations or medical need. We have articles on Risperdal and Clonidine, the other medications mentioned in the New York Times article; and the FDA provides fact-sheets for each, as well. Nimur (talk) 17:29, 10 October 2012 (UTC)[reply]
I'm not asking a sophisticated medical or legal question here. What I'm thinking is that, except for very heavy users, recreational users of methamphetamine or amphetamine (I haven't seen any indication they work differently, though there's another possibility) are not consuming more overall than those prescribed the drug on a daily basis. The kids often are free not to take the drug as prescribed, but to grind it up and snort it, possibly in binges for tests or for recreation. [26] So I don't see any difference, except in a religious sense, between the use of the drug as purchased illegally on the street and as used by at least a significant fraction of the kids to which it is medically prescribed. So to put it bluntly I would expect that, if half the stories about meth heads are true, that we would have kids on the prescription setting up guns and tripwires in their school lockers to guard against CIA agents pilfering their stash. There's something about all this that just doesn't fit, unless there's some important but unaccounted factor like an impurity in the street drug, or somebody is seriously lying about some aspect of how the drug is affecting some group of people, or if it's only dangerous when used at more than a critical (large) dosage, etc. Wnt (talk) 19:22, 10 October 2012 (UTC)[reply]
Why do you believe that someone recreationally taking meth or amphetamine is not taking more than prescribed? The term "Meth Head" indicates someone who is addicted, has built up a tolerance, who might be taking 60+ mg a pop (typical prescribed does is in the range of 20 mg/day, probably taken in two doses, or before meals if for weight control). A recreational user is also more likely to inject it, smoke it, or snort it, whereas someone prescribed an amphetamine will be taking it orally (and thus getting more of it in the system quickly). If they inject it, they are often doing so with a used needle, giving themselves HIV, Hep. C, etc. Street drugs are notorious for being cut with fillers, which are often not harmless. The production of street meth is often not done very carefully, and might have leftover byproducts, which certainly aren't harmless (Phosphorus, Hydroiodic acid, etc.) Buddy431 (talk) 20:09, 10 October 2012 (UTC)[reply]
Both of you are essentially stating your estimation of a descriptive point, namely how much meth is typically consumed by a recreational user, as fact. How about some real facts? I would be curious to know whether there is such a thing as a controlled recreational user, someone who knows his limit and stops, and if so how common such a thing is. Are there any reliable data on that? (I concede that there might very well not be any good data on it; such people, if they exist, presumably stay under the radar of law enforcement and of addiction treatment facilities.) --Trovatore (talk) 20:13, 10 October 2012 (UTC)[reply]
I estimated my typical "street dose" from this probably unreliable source. If we look at the slightly more reliable PBS FAQ, it suggests a "hit" of about a quarter gram, which, if it's 50-70% pure, is quite a bit higher than my estimation. The point remains that it's significantly higher than what a doctor would prescribe. Buddy431 (talk) 20:37, 10 October 2012 (UTC)[reply]
Uncle Fester (not the most reliable source) recommends a maximum dose of 50mg a day, maximum 5 days a week in one of his books; but if a topic about daily dosage on a drug forum can be trusted, most meth heads would be taking 200 to 500 mg. If used to enhance productivity the Erdős way, 10 to 30mg would be sufficient.
Given the mechanism of action, tolerance will build up rapidly, at least for the stimulant effects. Hallucinations and psychosis are likely to develop, in experiments they were able to induce hallucinations in all test subjects by increasing the dosage. The difference between the effects of small and large doses could be related to the type of vesicles involved; at low doses, the large vesicles release dopamine, at large doses also the small vesicles start releasing.
Phosphorus and hydroiodic acid are unlikely adulterants, especially HI would never survive the acid/base extraction. Iodine salts may be present, and chloro-ephedrine has been found in street meth. Red phosphorus isn't especially toxic, otherwise match boxes and matchbooks would come with health warnings, the striking surface is 50% phosphorus.
Most of this comes from sources that aren't necessarily WP:RSMED, so... Ssscienccce (talk) 00:47, 12 October 2012 (UTC)[reply]
Hmmmm, this source [27] says that "an average dose of meth is about a quarter of a gram. Because of ice’s intensity, smaller doses provide bigger highs; a gram of ice can provide 10 to 25 hits (doses) of meth. Heavy meth users take three or more grams of meth at a time." Apparently purity is a really major factor in trying to understand what the dose is... Wnt (talk) 03:35, 12 October 2012 (UTC)[reply]
October 10
Awareness of the link between sex and reproduction
At what point in our evolution did humans become aware of the link between having sex and reproduction? Given the time interval between the two, it doesn't seem that the former would necessarily imply the latter. Do chimps know? Chris (talk) 10:38, 10 October 2012 (UTC)[reply]
The females would probably have been aware some time before the males. Double sharp (talk) 11:22, 10 October 2012 (UTC)[reply]
The ability to "be aware" or "be self aware" is not an easy thing to define, and it depends on how you work out your terms. Sentience and Sapience and Self-awareness and Theory of mind are all at least tangentally related to answering the question, and some directly required. Even for chimps, there's a major problem with answering the question, which is you'd need to be able to ask them to get direct evidence of that level of knowledge. The only way to infer without directly asking is to assert that a certain level of self-awareness and sapience is necessary to make that connection, and then we get into the thorny problem of defining those terms. --Jayron32 12:26, 10 October 2012 (UTC)[reply]
Assuming that chimps are sentient but also have very limited communication skills, the only way a chimp could know about this link is if she made the connection herself. This is less likely to happen for a chimp than for a person. (1) I wonder if there are case studies of pregnant young women who didn't know the connection. If so, that would suggest that maybe human individuals in general only know the connection because it is culturally learned (and originally culturally discovered); in that case, chimps without high-level language would not be able to have it as part of their culture. (2) I wonder what/when is the first mention of the link in recorded writing. If that first mention came long after the advent of writing about the human condition, that might suggest that humans didn't know it at first, until it was discovered and disseminated into the culture. That strikes me as a long shot, though -- I would guess that even if the knowledge is not innate in each human, still society would have discovered it before writing was invented. Duoduoduo (talk) 15:10, 10 October 2012 (UTC)[reply]
Regarding the second question, even the oldest recorded stories (e.g. Egyptian mythology, see Osiris myth) make that link, and I don't doubt it was known even in prehistory. - Lindert (talk) 16:13, 10 October 2012 (UTC)[reply]
I read an article, which I'm struggling to find, which suggested that the connection likely came after the domestication of animals. It's a much clearer connection in say, a dog, which only comes into heat in certain times of year, rather than a human where we're fucking each other pretty constantly. Here's an interesting reply, with at least some research. It appears that aborigine Australians (who do not have domesticated animals until European contact) may have been unaware of the connection between sex and pregnancy. It's hard to sort through how much they were "really" ignorant, but anyways, it suggests that it's not as obvious as some of us might think. There's a couple other interesting resources linked on that page. Anyways, we'll probably never know for sure when the connection was made, but there's been some speculation among scientists (and others). Buddy431 (talk) 19:52, 10 October 2012 (UTC)[reply]
Here's the original column I read. Sadly unreferenced, but certainly plausible. Buddy431 (talk) 19:55, 10 October 2012 (UTC)[reply]
Well, the problem here is that the knowledge was obviously gained prehistorically. Things such as the triple goddess cult, with king stag celebrations and so forth imply knowledge of the link between sex and reproduction. One of the funniest criticisms I have ever heard of Christianity was a fellow student insisting to me that first-century Jews didn't know the link between sex and pregnancy, so the stories of the immaculate conception and Jesus's birth to the Virgin Mary had to be late middle-age forgeries! As if the people of ancient and classical times were cavemen. μηδείς (talk) 20:03, 10 October 2012 (UTC)[reply]
It was certainly prehistoric for some people, but evidently not for everyone (Australian aborigines, etc.) And just to be pedantic, the immaculate conception is a Catholic Dogma, and probably didn't really develop until the 7th century or so, and wasn't really officially sanctioned until the 15th century. Buddy431 (talk) 21:22, 10 October 2012 (UTC)[reply]
What? The Australian aborigines never developed writing. All of their history prior to European colonialism is prehistory. --140.180.242.9 (talk) 22:41, 10 October 2012 (UTC)[reply]
And then Europeans came (so it was no longer prehistoric), and documented this belief into the early 20th century. The connection, at least if the sources I cite are to believed, is not due to the development of writing but of domestic animals. Buddy431 (talk) 23:01, 10 October 2012 (UTC)[reply]
And not to be pedantic, but immaculate conception and the virgin birth of Jesus aren't the same thing (as is mentioned in the first few lines of the article you linked) Or does original sin have something to do with this?[The Ip directly above isn't me]Phoenixia1177 (talk) 22:45, 10 October 2012 (UTC)[reply]
That's not even remotely pedantic. The VB is the dogma that Mary gave birth to Jesus but remained a virgin. The IC is the dogma that Mary herself was born without original sin (which is supposed to be be why she was a suitable human mother for Jesus in the first place). The two events occurred at least 15 years apart. But I've come across astounding confusion about these dogmas, even in the minds of polymaths like Barry Jones (whose birthday it happens to be today, Thursday 11th here. Happy Birthday, Mr Jones). On page 495 of his Dictionary of World Biography (2nd ed. 1996), he states, in reference to Mary: The doctrine of her Perpetual Virginity (i.e. that she had no natural children) was adopted by the Council of Chalcedon in 451. Her Immaculate Conception (i.e. that she was the subject of a virgin birth) was proclaimed in 1854 by Pope Pius IX .... Both of his i.e.'s, which I've highlighted, are completely wrong. He may have corrected these gross errors in later editions. -- Jack of Oz[Talk] 23:18, 10 October 2012 (UTC)[reply]
The person who presented the argument and I were both raised Catholic, so yes, we knew the doctrines were separate, and that's why I mentioned them both. His point in all seriousness was that people didn't know that conception resulted from sex until the renaissance or so, so that the doctrines couldn't possibly date back to early Christianity. The consensus in the class, including the history teacher, was that he was right that it was not known at the time of Jesus that sex was necessary for conception. That's simply absurd, whether or not it is true (which i believe it is) that Mary's immaculate conception was a later doctrine. Virgin birth myths predate Christianity. They obviously require the knowledge that sex is necessary for conception, since there would otherwise be nothing remarkable about a virgin birth, would there? Still makes me laugh to remember this. It is very striking if you study classical history how modern the ancients were in their science, philosophy, and even political corruption. Yet it is incredible how many people do think the ancients were basically cavemen in togas. μηδείς (talk) 02:08, 11 October 2012 (UTC)[reply]
Goodness gracious: it's patently ridiculous to believe that people 2000 years ago living in the Levant didn't know that sex made babies. I mean, as long as people have been breeding animals it is plain that people have known that sex makes babies. Anywhere with settled agriculture or animal herding should know that sex makes babies, and any claims that they didn't is so patently stupid as to deny the need to refute it further than that. --Jayron32 02:18, 11 October 2012 (UTC)[reply]
Why would the average person know whether the Levant domesticated animals 2000 years ago? Large parts of the world didn't, like much of Africa and all of the Americas. The average person might know some ancient history, so they might know about Greece, Rome, Persia, Mesopotamia, China, the Indus valley, etc. But Judah/Israel was an insignificant backwater for almost all of history, and it's not inconceivable to take an entire world history class without hearing anything about it. --140.180.242.9 (talk) 02:57, 11 October 2012 (UTC)[reply]
If the average legally competent Westerner doesn't know that they had domesticated animals in the Mid East at the time of Caesar and Christ it's time we shut down wikipedia as hopeless. All indications are that the Amerinds who colonized the New World and brought the dog with them would have been aware of the connection back in 13,000 BC, as would all the Neolithic peoples of the Old World, at least those that were pastoral nomads and kept dogs, and presumably the New Guinea highlanders who farmed at least 7,000 years ago if not much earlier. μηδείς (talk) 03:13, 11 October 2012 (UTC)[reply]
If such people are basing their understanding of the situation on the Bible, discussions of Pastoralism are rife throughout the bible. Heck, Christian symbolism (the lamb, the shephard, the use of the word "Pastor") is filled with references to sheep herding. Sorry, it's just not feasible that someone can have read any meaningful part of the Bible and not have noticed that discussions of domesticated animals are all over it. Which is not to say that you aren't correct about stupidity in certain people, but that those people exist doesn't mean we need to accept that level of ignorance as normative. --Jayron32 03:42, 11 October 2012 (UTC)[reply]
And just to prove that anyone with familiarity with the Bible should have also known that people living at the time the Bible describes understood the sex-baby connection, see Genesis 16:1-4 (from the New King James Version): "See now, the Lord has restrained me from bearing children. Please, go in to my maid; perhaps I shall obtain children by her." in v.2 and "So he went in to Hagar, and she conceived." in v. 4 Other translations use other euphemisms for sex here (the NIV uses "sleep with", as does the paraphrase "The Message"), but the Douay Rheims and all King James derivatives use "go in to her" as in enter her. As in, they're talking about the nookie here. So it is patently unacceptable that someone involved in religious education in any form of Christianity or Judaism could have thought that people living at the Birth of Jesus didn't know that sex made babies. The Abraham story is one of the oldest in the Bible, both in terms of its setting and authorship: if it's that plain in there, I just don't know what else I would say to someone who claimed otherwise. --Jayron32 04:56, 11 October 2012 (UTC)[reply]
There's also something in there about Adam "knowing" Eve and conceiving children. The ancients didn't know about the microscopic specifics, of course, but they understood from observation that it took both a male and female, and also that the probability of conception was related to the menstrual cycle. To the minds of the ancients, the male had to "plant a seed" in the female to make a baby sprout. Hence the terms "sperm" and "semen", Greek and Latin respectively, which both mean "seed". ←Baseball BugsWhat's up, Doc?carrots→ 11:54, 11 October 2012 (UTC)[reply]
And the Hebrew for seed זרע which is used for both semen and for offspring/descendants. - Lindert (talk) 12:45, 11 October 2012 (UTC)[reply]
Actually, the text in Genesis 4 is may be more explicit than "knowing", that's among the English language euphemisms used in some translations, but you can tell by comparing various translations that many consider the phrase to unambiguously refer to sex. Douay Rheims American: "And Adam knew Eve his wife: who conceived and brought forth Cain", Complete Jewish Bible: "The man had sexual relations with Havah his wife; she conceived", English Standard Version (a King James derivative): "Now Adam knew Eve his wife, and she conceived and bore Cain", New International Version: "Adam made love to his wife Eve, and she became pregnant and gave birth to Cain", Orthodox Jewish Bible, "And HaAdam knew Chavah (Eve) his isha; and she conceived, and bore Kayin (Cain),". I even pulled up some non-English translations, this Spanish version says "El *hombre se unió a su mujer Eva, y ella concibió y dio a luz a Caín" using the "se unió a" or "unites himself with", a different sense entirely than "to know" or "to make love". This French version says "L'homme s'unit à Eve, sa femme; elle devint enceinte et donna naissance à Caïn.", using the same phrase "s'unit à". If anyone reads Hebrew, I would be curious as to what the exact word was used here in the original text. Many of these translations use euphemisms for sex which were most common at the time when the translation was fixed ("knew" in pre-20th century translation, "made love" in more modern ones) so I would be curious as to what the exact word was in Hebrew and what that word is translated to outside of this specific context. --Jayron32 13:44, 11 October 2012 (UTC)[reply]
I know a little bit of Hebrew, and the word used for intercourse in Genesis 4 does indeed literally mean 'to know'. For example, in Genesis 3, the snake says to Eve 'Ye shall be as gods, knowing good and evil' and likewise 'they knew that they were naked' etc. The same verb ידע is used in all these places. I don't think the euphemism arose in English actually, on the contrary, this manner of speaking was not common in English at the time, it was copied from Hebrew. The reason that many modern translations use 'make love' etc. is because they recognize that 'knowing' in this sense is not actually good English, while older translations like the KJV were much more concerned with translating word for word, and so ended up using expressions that were quite strange and uncommon in the English language. On the matter of it being explicit: it was certainly readily understood, just like 'sleeping with someone' does not literally mean what it infers, but that does not make it ambiguous. - Lindert (talk) 14:03, 11 October 2012 (UTC)[reply]
Interesting. So the euphemism exists in the original Hebrew. Thank you for that insight! What about Genesis 16:1-4 then? Does the Hebrew there say "know" or does it say "go in to" as the translations seem to use? --Jayron32 20:07, 11 October 2012 (UTC)[reply]
The verb used in Genesis 16:2&4 is בוא (bo), and means literally to come/go in. Genesis 7:1 'come thou and all thy house into the ark' uses the same Hebrew construction (i.e. -בוא אל) as Genesis 16:4 'And he went in unto Hagar'. - Lindert (talk) 22:02, 11 October 2012 (UTC)[reply]
It makes sense that the euphemism of 'know' for 'have sex' originated in Hebrew because the same euphemism exists in French and Spanish (and I assume other languages connected to historically Christian societies), viz. conocer and connaitre respectively This is sounding more like a question for the Humanities desk; didn't someone already ask this question a few months ago? 24.92.74.238 (talk) 02:29, 12 October 2012 (UTC)[reply]
Isn't that what the Stones sang on Ed Sullivan, "Let's get to know each other..."? μηδείς (talk) 03:28, 12 October 2012 (UTC)[reply]
Promoters are located near the genes they transcribe, on the same strand and upstream (towards the 5' region of the anti-sense strand).
How promoters could be located at upstream in anti-sense strand. Because it is the template strand for transcription. Trascription initiates from 3' end in anti-sense strand. So, promoter should be at 3' (towards downstream region) site of the gene in anti-sense strand. — Preceding unsigned comment added by 117.212.219.234 (talk) 11:25, 10 October 2012 (UTC)[reply]
The wording is clumsy. Promoters are 5' to the gene, with "5'" and "3'" defined by the strand encoding the gene. -- Scray (talk) 13:10, 10 October 2012 (UTC)[reply]
Defining which strand it's on seems kind of pointless to me. The promoter is as much on the sense strand as it is on the antisense strand. But there is simply not a simple way to describe a promoter. Promoter elements can be located far upstream from the gene start site, or even downstream, inside other genes, and promoters can overlap one another. One of my professor's from college loved to ask at the beginning of every genetics class he taught, "what is a promoter" (or alternatively, "what is a gene"). Someguy1221 (talk) 23:14, 10 October 2012 (UTC)[reply]
Promoters can include enhancer elements that can be distant and not upstream, but the core+proximal promoter is 5' of the coding region, near the transcription start site on the sense strand. "Typical" always has exceptions, but this description is quite consistent. -- Scray (talk) 05:27, 11 October 2012 (UTC)[reply]
The classic exception would be with RNA polymerase III; but usually when people start talking about genes and promoters they're thinking about RNA polymerase II, which handles a huge variety of the "interesting" genes. In any case, there just about has to be something recognizable about some sequence not extremely far from the start of transcription, or else how does it know where to start? At least, I can't really think of a good counterexample offhand, though specific elements like TATA can be absent. Wnt (talk) 01:16, 12 October 2012 (UTC)[reply]
This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. Discuss -- Scray (talk) 17:15, 10 October 2012 (UTC)[reply]
This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. Discuss -- Scray (talk) 17:15, 10 October 2012 (UTC)--~~~~[reply]
baseball hat
is there any way to tell if a baseball hat has a cardboard or plastic bill before you wash it and have it fall apart? --Wrk678 (talk) 18:22, 10 October 2012 (UTC)[reply]
You could try sticking a pin through the bill. Plastic presumably will offer more resistance to penetration than cardboard. However, what is your plan if you can't wash it ? Then you have a dirty, unwashable hat. You really need to make this determination before you buy it, to avoid this dilemma later. StuRat (talk) 19:24, 10 October 2012 (UTC)[reply]
Dry cleaning would be an option. A quick test with a piece of cardboard shows no immediate problems. Not that that proves anything... Ssscienccce (talk) 08:19, 11 October 2012 (UTC)[reply]
You might also check the tag inside the cap and see if it has any washing instructions. ←Baseball BugsWhat's up, Doc?carrots→ 04:47, 11 October 2012 (UTC)[reply]
First environmental science program(me)(s)
I was wondering which college or university established the first environmental science degree program. Googling, I can find a few programs claiming to "one of the first," but no definitive answer. With several ways to define the question, I'd be interested in (1) the first undergraduate program; (2) the first graduate program; (3) the first program in the US; and (4) the first program outside of the US. --BDD (talk) 19:27, 10 October 2012 (UTC)[reply]
It should be noted, however, that much of sanitary engineering originated as an overt attempt to make people's environment more livable. The entire justification for building the London sewerage system was to improve London's environment; to make it more livable. Of course, most people don't start caring about the Environment until they realize that their environment is becoming harmful to them, but selfish preservation is still one of the primary motivating factors in human action. --Jayron32 16:00, 11 October 2012 (UTC)[reply]
Agreed. Most mainstream environmental movements are still about making life better for humans, although there are a few bizarre movements that call for people to go extinct in order to preserve "Mother Earth". StuRat (talk) 21:34, 12 October 2012 (UTC)[reply]
Note also that "environmental science" means different things to different people. Two important branches are (1) the study of how man's actvities affect the environment, and (2) what things man has to do to cope with what the environment provides. Item (1) has attracted much attention in recent years, but item (2) has been studied for much longer, probably at least 100 years or so. For example, Murdoch University in Australia http://en.wikipedia.org/wiki/Murdoch_University has always had (since the University was established in 1975) courses and research in what they call "environmental science" - these have included such things such as novel types of air-conditioning and energy-efficient buildings. Wickwack124.178.43.122 (talk) 00:58, 11 October 2012 (UTC)[reply]
Earth-Moon Recession
I understood that our Moon is receding from Earth about 38 mm/year due to tidal effects. However I was curious to compare this result with metric expansion of space by assuming it applies to Earth Moon system as well. When applying Hubble's law, I found this would give about 29 mm/year. Can this be just an incident?--Almuhammedi (talk) 19:32, 10 October 2012 (UTC)[reply]
Presumably you mean to ask if it's a coincidence ? StuRat (talk) 19:33, 10 October 2012 (UTC)[reply]
The metric expansion of space only applies to objects that are not bound to each other by gravity. The earth-moon system is bound by gravity, so it is not affected. --Jayron32 19:42, 10 October 2012 (UTC)[reply]
It is just a coincidence, and the metric expansion of space is not applicable within gravitationally-bound systems; it only applies well above the scale of galaxies. By way of evidence, consider that the magnitude of Earth-Moon tidal acceleration is impacted by the nature of Earth's oceans, which can play no role whatsoever in Hubble's law. — Lomn 19:47, 10 October 2012 (UTC)[reply]
What Jayron said. μηδείς (talk) 20:05, 10 October 2012 (UTC)[reply]
The metric expansion of space does not "expand" bound systems. But I always wondered: It shows up as the cosmological constant in Einsteins equations. Shouldn't it also show up in Newtons equations (as an extremely small modification, of course)? In other words, shouldn't the attraction between two bodies be ever so slightly smaller thanks to it than it would be without it? --Stephan Schulz (talk) 07:25, 11 October 2012 (UTC)[reply]
Well, that makes sense, because we say that "gravitationally bound systems aren't expanding away from each other", but that's a tautology: what it really means is that systems whose force of gravity is strong enough to overcome the metric expansion of space don't recede from each other. Neither the metric expansion of space nor gravity every stops working, its just that they counteract each other so if gravity is strong enough, the net effect is that the objects don't move away from each other. But gravity doesn't have any extinction; it decreases in strength via the Inverse-square law, but it should never drop to zero for any finite (but arbitrarily large) distance. Thus, everything in the universe is subject to "metric expansion", but you only see objects moving away from each other if the objects are sufficiently far apart already as to be under such a weak influence of each other's gravity that the metric expansion becomes the greater effect. --Jayron32 15:57, 11 October 2012 (UTC)[reply]
Your comment is confusing some things. By the "metric expansion of space" you really mean changes in the cosmological scale factor. The evolution of that scale factor is driven by three processes, inertia, gravity, and dark energy. Most of the expansion we talk about is really the Hubble flow which is a purely inertial process. Specifically, galaxies expand from each other because at the moment of the big bang the primordial universe was imparted with momentum that is still resulting in expansion today. It is like watching the debris from a bomb going off. At the moment of the explosion, a large impulse is imparted to everything, but afterwards the debris continues flying apart without the need for any additional forces. If we could magically turn off gravity and dark energy, the universe would continue to expand. The second process governing the scale factor is gravity. On cosmological scales the sole effect of gravity is to slow the expansion of the scale factor. In a universe with sufficient mass, gravity would eventually win and the expansion would reverse itself leading to a contraction and eventually a big crunch. We do not appear to live in such a universe. However, in the absence of dark energy all you need to consider is gravity and the initial momentum in order to understand the evolution of everything. In order for a system to become gravitationally bound, it must have already shed whatever momentum existed that would have initially had its constituent parts tending to fly apart. Gravitationally bound systems aren't affected by Hubble flow, simply because they have already overcome it in order to form in the first place. In the pure Hubble flow regime there is no any additional force creating expansion, hence gravitationally bound systems would be completely unaffected by Hubble flow. Dark energy is the third wrinkle to the story. On cosmological scales it imparts a force that tends to increase the scale factor. If we assume dark energy takes the form of a cosmological constant, then it can be modeled in the classical limit as a force directly proportional to distance, i.e. , where the proportionality constant is . For some concrete numbers, the force of the Sun on the Earth is 3.5×1022 N, compared to the dark energy "force" between the Sun and Earth of 0.8 N. In the classical limit, dark energy is always exerting a force, but the magnitude of that force is trivial until you get to cosmologically large distances. Unlike the Hubble flow, which is a passive inertial process baked in at the Big Bang, dark energy is an active process associated with a new force law and one which can create additional expansion. Dragons flight (talk) 20:56, 11 October 2012 (UTC)[reply]
Yes, I was trying to refer to the positive outward pressure exerted by so-called "dark energy" which is real and active, and as you note insignificant in all but the biggest cases, and not the passive "Hubble flow" which is just the residual momentum of the initial Big Bang. --Jayron32 21:41, 11 October 2012 (UTC)[reply]
I'm more like my mother than my father
Through nondisjunction, it should be possible, perhaps inevitable, that some child will inherit two copies of some chromosome from one parent, and zero copies of the same from the other parent. Are there any documented cases of such a thing? Thanks. Someguy1221 (talk) 22:28, 10 October 2012 (UTC)[reply]
Hello, I have a small project for a class where I have to find an example of a genetically modified organism, investigate its basis, and give it's pros and cons. However, "the example must be a viable organism, not a plasmid, vector etc". I am limited to GMOs dealing with viral gene therapy.
However, my understanding of viral gene therapy is that genes are inserted into the virus, which is allowed to replicate in other organism to it's benefit (e.g. cancer killing proteins). Doesn't this therefore qualify the virus as a vector (but equally a GMO)? And thus, is not allowed to be chosen as a topic? Many thanks 93.186.23.80 (talk) 00:40, 11 October 2012 (UTC)[reply]
A virus is not usually considered to be an organism; see our organism article. Looie496 (talk) 00:55, 11 October 2012 (UTC)[reply]
See the first sentence here. Viral vectors (e.g. retroviruses) can be used to create stable recombinants, a process sometimes called "pharming". The product, not the vector, is a GMO. -- Scray (talk) 01:28, 11 October 2012 (UTC)[reply]
excluding genetically engineered plasmids and vectors (which are produced by the truckload on a daily basis in research labs) "viable organisms" are not restricted to just viral gene therapy. Many crops are now genetically engineered (e.g. see golden rice) The links at the very bottom of that page may also help you. Many genetically engineered animals are used to study the effects of various diseases, drugs and developmental processes. Good luck and have fun.Staticd (talk) 06:07, 13 October 2012 (UTC)[reply]
Morphine in World War 2
In WW2, US soldiers and flyers carried a "syrette" with a metal tube like that for toothpaste containing 0.5 grain of morphine tartrate, connected to a hypodermic needle for administering the drug subcutaneously to a wounded soldier, with no additional dose to be given for 2 hours. 1)(A question for better understanding of historical medical practice, not a request for medical advice:) Is that equivalent to a modern dose of 32.4 milligrams of morphine? drugs.com says that a typical subcutaneous dose for an adult would be only "2.5 to 20 mg every 3 to 4 hours as needed " 2)In the 1977 movie "The Deep," divers find the wreck of "The Goliath," a ship which sank while carrying medical supplies to Europe in WW2, (based on some historical WW2 ship called the Constellation) and the presence of thousands of little glass ampules of liquid morphine excites the interest of criminals. Did Europeans (Brits, French and other non-Axis forces) inject their wounded from single-doseglass ampules (or perhaps at aid stations from multi-dose vials) with separate syringes, or were they supplied by 1940 with syrettes like US forces? (Or were they just expected to tough it out with a stiff upper lip and no morphine?) Thanks! Edison (talk) 03:11, 11 October 2012 (UTC)[reply]
1) that's the correct equivalency; that's a big dose. -- Scray (talk) 04:42, 11 October 2012 (UTC)[reply]
So big, in fact, that a second such dose would have been rapidly fatal (as the GIs themselves used to say, "One for pain and two for eternity"). Which is why the medics would put a big "M" on the wounded man's forehead after giving him morphine (as seen in war movies like Pearl Harbor, Saving Private Ryan, etc.) to make sure nobody else gave him a second dose by mistake. 24.23.196.85 (talk) 06:39, 11 October 2012 (UTC)[reply]
So when it says "0.5 grain," that is the effective dose of morphine, and whether it is in a "tartrate" of a "sulphate" compound is irrelevant? This website says the tartrate is only 87% as potent per mass: [31] . This table has some conversion tables, but when someone gets "morphine" from a doctor or paramedic today, what chemical form is it likely to be? On the web, some sites say that the dose from these same syrettes is only 16 milligrams: ]http://armymedical.tpub.com/md0913/md09130102.htm]. Is that just plain wrong? Question 3)Finally, were these military syrettes stolen or diverted and sold by criminals to civilian drug addicts in WW2 as an alternative to heroin, or would they have been converted to heroin or "cut" with something before being sold to addicts by criminals? Thanks. Edison (talk) 15:43, 11 October 2012 (UTC)[reply]
Tartrate ion has molecular mass of 148.07 daltons, sulfate ion has a mass of 96.06 daltons, and morphine has a molecular mass of 285.34 in neutral form. I think that one hydrogen ion is added to the alkaloid nitrogen in the morpholinium salt (286.35), which means that half a sulfate or tartrate should be needed per morpholinium to balance the charge. That gets us 334.38 for the sulfate (half the molecular weight) and 360.39 ([32]) for the tartrate for the same amount of morphine. However, as listed in the table in the morphine article, the actual drugs are hydrates. (This is an example of why Wikipedia shouldn't be taken as medical advice - I very nearly answered according to the non-hydrated weight, which would, at least hopefully, be technically accurate but quite irrelevant to your historical scenario. Not to mention the stupid mistakes I made in the math trying to calculate per morpholinium rather than per molecular weight, which, in retrospect, was probably not the best way to avoid errors!) The sulfate gets 5 H20 (5 x 18.01528 = 90.0764) (half that per morpholinium) and the tartrate gets 3 H20 (54.04584) making the final weights per morpholinium 379.42 (sulfate) and 387.42 [33] (tartrate). Our article lists them as equal to 0.75 (sulfate) and 0.74 (tartrate) the free base weight of morphine (285.34), which agrees within the level of error in the table. (0.7520, 0.7365). Wnt (talk) 17:58, 11 October 2012 (UTC)[reply]
There are some errors in that table, it has Morphine phosphate (7 H2O) and Morphine phosphate (1/2 H2O) listed with the same freebase conversion factor. I'm not sure if the 0.5 grain would include the hydrate part. I've looked at pictures of the box these came in and it doesn't mention the hydrate. Don't know what the practice was then, but nowadays the dosage applies to the ingredient as it is written. Like 60 mg pseudo-ephedrine HCl, but dexedrine 5mg dextro-amphetamine (without the H2SO4) Ssscienccce (talk) 23:08, 11 October 2012 (UTC)[reply]
I found Medical Services of the Royal Australian Navy who presumably followed Royal Navy practice. "...the question of morphia administration was of great importance . Methods used before the war consisted of individual injections by the medical officers or possibly senior sick-berth ratings, using either tablets of morphine sulphate or hydrochloride in bulk solution from rubber-capped bottles. In addition, Wildey's syringe which enabled four or five doses to be given by the one full syringe was available in some ships. Obviously, however, it would be of considerable advantage in a ship, with its numerous isolated compartments, to have a foolproof syringe which would enable anyone, if the need arose, to give a correct dose to himself or to another. Hence the appearance of a self-giving syringe known as " tubunic " ampoule or syrette. Supplies of this article were very difficult to obtain but finally became available. Three types were used in the R.A.N.: the first from the United Kingdom, the second from the United States, and the third made in Australia . They were not extensively used and on the whole they proved a disappointment, by reason of the frequent collapse of the soft metal container or the blockage or breakage of the needle. The American article appeared to be the best." (p.25) So the US version seems to have been ahead of the game, but not available to Commonwealth forces until late in the war. I found a reference in The British Army 1939-45 (3): The Far East, By Martin Brayley about the Chindit columns that operated in the Burmese jungle behind Japanese lines; "Although it was never spoken of, it is clear that the helpless were often given a merciful overdose of morphine before being abandoned." (p.34) Alansplodge (talk) 17:51, 11 October 2012 (UTC)[reply]
A further reference that partly answers your question about British use in 1940 is in 56th Infantry Brigade and D-Day: An Independent Infantry Brigade, By Andrew Holborn, which includes the account of one soldier in France in January 1940; "Shrapnel (from a Stuka's bomb) hit me and I had a big red "X" on my forehead because I had been given morphine." (p.13) Alansplodge (talk) 18:07, 11 October 2012 (UTC)[reply]
Thanks. Sounds like various allied forces were well supplied with morphine either in large vials for medical officers to administer or with syrettes. I could not find general US or Brit book on field hospital practice in WW2, but did find some brief booklets for frontline medics. Question 4)Any suggestions as to a WW2 vintage handbook for British military surgeons or physicians which would identify other drugs they used in hospital or aid stations in the combat zone which would have had a ready market for pushers to sell to addicts or other illicit civilian users? Edison (talk) 20:43, 11 October 2012 (UTC)[reply]
October 11
depth of voice and time of day
Why is my voice so much deeper in the mornings, not to mention when I have a cold? I've checked, and it's not my imagination. I've been out of bed for only a little while, and I'm half an octave lower than last night. IBE (talk) 09:27, 11 October 2012 (UTC)[reply]
This is a possible medical condition. We don't give medical advice here, so see a doctor. Floda 120.145.20.231 (talk) 12:59, 11 October 2012 (UTC)[reply]
I think I have a fair idea of the rules. It would be a strange medical condition. It is a fairly common observation in the case of a cold that the voice drops a fair bit. I used myself to show that I had double checked that it wasn't my imagination. IBE (talk) 13:39, 11 October 2012 (UTC)[reply]
Googling for the lower morning voice portion finds a lot of singing sites that primarily suggest that your vocal chords are, after a night of disuse, relatively slack and thickened (analogous to taking the tension out of a guitar string). I have anecdotally observed similar effects when I have a cold, but I don't know what the relevant mechanism there would be. — Lomn 14:26, 11 October 2012 (UTC)[reply]
There's some discussion of this on the Straight Dope Forum, where the consensus seems to be that the voice is lower during a cold mainly because of swelling of the vocal cords. AndrewWTaylor (talk) 15:21, 11 October 2012 (UTC)[reply]
Just personal experience, but the phlegm coating the vocal chords seems to play a role in lowering the lowest attainable pitch, since a good rinse immediately raises it bu a couple of notes.Would a vibrating sting of a certain length and tension sound a lower pitch it it had more mass per unit length? The phlegm or coating could provide that extra mass. Edison (talk) 15:47, 11 October 2012 (UTC)[reply]
It would, that's why guitar strings are different thicknesses. The note a string sounds is a combination of its thickness, composition, length, and tension. They all play a factor. --Jayron32 15:52, 11 October 2012 (UTC)[reply]
Searching the web for morning deep voice finds some discussion suggesting that in the morning you are unaffected by the day's mental stresses (don't we all get whiny when we get stressed), and gravity hasn't been shaping your height and your vocal cords. 88.112.36.91 (talk) 16:42, 11 October 2012 (UTC)[reply]
The gravity one is quite interesting: I thought of this, but gravity should shrink your neck (well, slightly) making it a bit thicker, and hence your voice slightly deeper. But I like the whiny voice suggestion. IBE (talk) 17:19, 11 October 2012 (UTC)[reply]
Chemical Equilibrium Expression
I have a series of chemical reactions for which I'm trying to develop an equilibrium expression.
(1) A <> B + C
(2) (x)*B <> D
(3) (y)*D <> D
(4) D + A <> B + C
My intuitions says that:
K = K1([B][C])/(A + K4*D*A) + K2(D)/(([B]^x)+ K3([D]^y))
But I can't find a good set of rules to derive this. Thanks for any help that can be offered. — Preceding unsigned comment added by 134.20.11.89 (talk) 15:50, 11 October 2012 (UTC)[reply]
This must be obvious but I'm missing the meaning. If A<> B+C then how can D+A <>B+C? What does (y)*D <> D mean? Wnt (talk) 01:00, 12 October 2012 (UTC)[reply]
Not addressing the question itself, but for the benefit of clarity to everyone else, I assume "<>" is the equilibrium sign, which can be displayed directly on WP using the {{eqm}} template. So "A ⇌ B + C" displays as "A ⇌ B + C". DMacks (talk) 01:09, 12 October 2012 (UTC)[reply]
October 12
Dot product and cross product
We know "Work = Force x Displacement", where "Work" is scalar quantity and both "Force" and "Displacement" are vector quantity. This means dot product of vectors is scalar quantity. We also know that cross product of vectors is a vector quantity. Suppose, we are given "Power = Force x velocity". Here, both "Force" and "Velocity" are vector quantity and we have to find whether "Power" is scalar or vector quantity. It becomes easy if we have idea that "Force x velocity" is dot product or cross product. My question is how to recognize the given product of vectors is dot product or cross product. Please, also give me some examples where cross product of vectors is a vector quantity. Sunny Singh (DAV) (talk) 12:28, 12 October 2012 (UTC)[reply]
Any quantity is a vector if it is directionally dependent. Does a concept like "power" or "work" have a directional component? If so, it is a vector. If the value doesn't depend on the direction, it is a scalar. --Jayron32 12:44, 12 October 2012 (UTC)[reply]
Question, is there a difference between simple multiplication and the cross product? Plasmic Physics (talk) 12:51, 12 October 2012 (UTC)[reply]
We don't just arbitrarily multiply vectors and then try to figure out what formula to use. We use mathematical formalism to make a simple calculation about a physical quantity we care about. A dot product of two vectors represents the physically meaningful concept of projection. Loosely stated, this calculation measures how "similar" two vectors are; or how closely aligned they are; and it is scaled by the magnitude of each vector. We can also normalize if we are concerned only with geometry, and not magnitude. We often use the scalar result of a dot product to scale another vector, if that represents some physical, useful quantity. The cross-product is a little more unusual, because its physical interpretation is somewhat less intuitive; but simply put, a cross product guarantees orthogonality. There are many situations in physics where that property of vectors has physical meaning - like when we're calculating properties in rotating reference frames; or calculating interactions with magnetic fields, spinning objects, and fluid or particle ensembles. My point is, you decide which calculation you need entirely based on the physics; not just based on arbitrary combinations of your input variables. Nimur (talk) 14:25, 12 October 2012 (UTC)[reply]
Nimur's point is what I was going after, but in less eloquent terms as he puts it. Mathematics is a tool in these cases used to elucidate the physics, not the other way around. The physics of a situation drives what mathemetics we use to help explain it. If a physical quantity has a direction, vector mathematics is used to describe it. If a physical quantity is directionless, scalar mathematics is used to describe it. The question first to be asked when trying to decide whether a quantity is scalar or vector should be "does this physical property depend on direction." --Jayron32 16:13, 12 October 2012 (UTC)[reply]
Torque is an example where the cross product is used. The result of the applied force will be a rotation around an axis perpendicular to the force and the lever. Lorentz force is another example: the force on a charged particle in a magnetic field is perpendicular to the direction of the field and to the direction it's moving in (the velocity vector). For a charged particle in an electric field on the other hand, the force will be in the direction of the field. Angular velocity can also be represented as a vector, and the cross product is used here too. One way to decide whether dot or cross product should be used is considering two cases, one with both vectors in the same direction, the other with perpendicular directions. If the result should be maximum for the first and zero for the second, then you would probably use the dot product; in the opposite case, the cross product. Ssscienccce (talk) 10:55, 13 October 2012 (UTC)[reply]
Two questions for project
Does anyone know what structural settings bending folds are most likely to be found in? What about buckling folds? This will be useful in identifying where different structures formed. Thanks.~~--- Anon — Preceding unsigned comment added by 99.146.124.35 (talk) 12:46, 12 October 2012 (UTC)[reply]
From my previous question I realized that malaria was present in Europe some centuries ago, but now it has been eradicated. How could be possible that malaria mosquitoes specifically disappear but that you still get mosquitoes in Europe? What's the difference between one kind and the other? Gorgeop (talk) 14:12, 12 October 2012 (UTC)[reply]
Is genetic resistance to malaria perhaps what you are looking for? Mosquitos are not born with malaria, they need to ingest it from an infected host to be able to pass it on. If a strong resistance to malaria removes the disease from the population, then no amount of vectors will matter since there is no disease to pass on. Livewireo (talk) 14:42, 12 October 2012 (UTC)[reply]
Malaria eradication was very much intentional. We have an article National Malaria Eradication Program for the U.S. - not sure if we have the equivalent for Europe. History of malaria makes an extraordinary claim indeed, that Anopheles gambiae got loose in South America, caused the worst malaria epidemic ever seen in the New World, but was then completely exterminated by eradication efforts within a few years. Which, I have to say, seems more ambitious than programs against invasive species tend to be today, even if they had to use Paris Green (and ordinary Pyrethrum) to do it according to our article - and it was done in northeast Brazil! (Apparently this was just before DDT was discovered to be an insecticide ... not sure if it played a role; certainly it did in other efforts) Of course, those were also the days when "draining the pestilential swamps" was seen as a positive thing. Wnt (talk) 14:59, 12 October 2012 (UTC)[reply]
Generally speaking the major way to eliminate malaria was to drastically decrease mosquito populations (vector control). Historically this was achieved by drainage and later pesticides. By driving down the number of mosquitos for an extended period of time, you can decrease the amount of overall malaria in the ecosystem to basically zero levels, because the malaria parasite cannot reproduce without mosquitos. You will never really get rid of all of the mosquitos, and their populations will rebound, over time, but without the malaria parasites. Mosquito monitoring and control is no doubt still in effect (in the United States, the Centers for Disease Control and Prevention does this); if all mosquito control efforts stopped tomorrow, over time malaria would likely return to Europe and other places it has been "eradicated" from. --Mr.98 (talk) 14:59, 12 October 2012 (UTC)[reply]
See The history of malaria in England which says that locally transmitted malaria was finally eradicated from the UK in the 1950s, which is surprisingly late. We still have mosquitoes though. Alansplodge (talk) 18:03, 12 October 2012 (UTC)[reply]
Malaria is transmitted by Anopheles gambiae mosquitos and these are not like other mosquitos that are still extant in Europe. It's easier to eradicate this species, since they are not able to "hibernate", therefore, you just have to hit them hard once during the winter, when they are more prone to be eradicated. The eggs that they lay won't be dormant for months and hatch when it's hot again. Summary: it was easier to get rid from malaria transmitting mosquitos in Europe, but others are more resilient. OsmanRF34 (talk) 19:52, 12 October 2012 (UTC)[reply]
The parasite needs certain species of mosquitoes to reproduce and human or animal hosts to spread. Mosquitoes don't live long and will feed only a few times before they die. For the parasite to spread, you need infected persons (or other secondary hosts if the mosquito is a species that feeds on animals as well) in whom the parasite has had time to infect the blood cells, a mosquito of the right species has to bite him and get infected, the parasite needs time to reproduce in the mosquito and then the mosquito has to feed on another person before it dies. Infected people will eventually be diagnosed and treated, so when the infection rate is low, the number of hosts will decrease steadily. Ssscienccce (talk) 12:05, 13 October 2012 (UTC)[reply]
Volume of naphtha
How many British Thermal Units of naphtha can fit into one cubic foot or cubic meter? I have a figure with a specific number of BTUs, and I'm trying to figure out its total volume, so I went to Wolfram Alpha, but all I got was "BTUIT (IT British thermal units) and ft3 (cubic feet) are not compatible." 2001:18E8:2:1020:749C:5B76:1D8E:3D22 (talk) 14:24, 12 October 2012 (UTC)[reply]
Well our article has a density down as "750-785 kg/m3" - with that you can work from a measure of BTU per kg, though actually a direct statement of BTU per volume might be more accurate. (This won't be perfectly accurate in any case because with that much of a density range there must be some variation in composition) Wnt (talk) 15:12, 12 October 2012 (UTC)[reply]
NG-based FT naphtha "higher heating value" - 119,740 btu/gal; 20,488 btu/lb; 47.654 MJ/kg; density 2,651
"[1] The lower heating value (also known as net calorific value) of a fuel is defined as the amount of heat released by combusting a specified quantity (initially at 25°C) and returning the temperature of the combustion products to 150°C, which assumes the latent heat of vaporization of water in the reaction products is not recovered. The LHV are the useful calorific values in boiler combustion plants and are frequently used in Europe.
"The higher heating value (also known as gross calorific value or gross energy) of a fuel is defined as the amount of heat released by a specified quantity (initially at 25°C) once it is combusted and the products have returned to a temperature of 25°C, which takes into account the latent heat of vaporization of water in the combustion products. The HHV are derived only under laboratory conditions, and are frequently used in the US for solid fuels."
I'll leave it to you to double check all these numbers agree with each other. Wnt (talk) 15:20, 12 October 2012 (UTC)[reply]
Engineering and technical books usually distinguish between the LHV and HHV, as, usually but not always, the LHV is what matters to an engineer. However, it is common in college science texts to just quote a single value without stating which it is, and when they do that, it's the HHV, as it is the HHV that is measured in a simple bomb calorimeter. Ratbone124.178.45.41 (talk) 15:58, 12 October 2012 (UTC)[reply]
Note that the way you asked this Q implies that a BTU is a unit of volume. Instead, I suggest that this would be a clearer Q: "How many British Thermal Units can be generated by burning the naphtha which can fit into one cubic foot or cubic meter ?". StuRat (talk) 18:45, 12 October 2012 (UTC)[reply]
Hmm, perhaps I misunderstood what a BTU is. I thought it was the amount of gas (or whatever other fuel) needed to produce a certain amount of thermal energy? 2001:18E8:2:1020:749C:5B76:1D8E:3D22 (talk) 20:41, 12 October 2012 (UTC)[reply]
Actually, a British Thermal Unit is a unit of energy. Devices having nothing to do with flammable materials, like an electrical air conditioner, are also rated in BTUs: [35]. StuRat (talk) 21:14, 12 October 2012 (UTC)[reply]
DUTASTERIDE/ASPARTAME combined side effects
many articles give detailed side effects of DUTASTERIDE and many articles give detailed side effects of ASPARTAME, but no article gives effect of both these taken together.
If an article could be given on this topic of a pointer to the sites where this could be found would be good.
Thanks — Preceding unsigned comment added by 117.223.102.73 (talk) 16:25, 12 October 2012 (UTC)[reply]
I added a title. StuRat (talk) 18:42, 12 October 2012 (UTC) [reply]
Unless this has been studied to see if the combined side effects are worse than just the total of each, there is unlikely to be any such article. And, unfortunately, the number of combinations of two substances is too large for every combo to be studied. StuRat (talk) 19:04, 12 October 2012 (UTC)[reply]
Don't hold your breath for such an article when this search provides zero results. -- Scray (talk) 19:59, 12 October 2012 (UTC)[reply]
Indeed you have discovered the Achilles heel of "safe chemicals" and drugs in general. One may be reliably safe in tests, but two in combination can be a different matter. The classic example of this is melamine, which is pretty much safe to contaminate/adulterate foods with ... until it meets up with cyanuric acid to form big plates of melamine cyanurate that concentrate and clog up the kidneys.
That said, the odds of any given interaction are, well, "probably very low". And because dutasteride resembles a steroid and aspartame resembles a small peptide, their interactions shouldn't be all that different from interactions of other chemicals within the body ... unless they are. Wnt (talk) 19:51, 13 October 2012 (UTC)[reply]
Is it possible that someone studying our civilization 30,000 years from now differentiates caucasoid, mongoloid, and negroid the same way we differentiate neanderthal, sapien and denisavan? As different species due to the relatively narrow geneome that would exist at the future time?165.212.189.187 (talk) 18:51, 12 October 2012 (UTC)[reply]
I doubt it. A species is defined in sexually reproducing organisms as any group which can reproduce to produce fertile offspring. Clearly this is the case with all humans (even extinct Neanderthals). StuRat (talk) 18:55, 12 October 2012 (UTC)[reply]
No. While the members of a race have certain genetic similarities not shared with other races, they do not form monophyletic groups and cannot be classed as subspecies. See race and genetics for more information. Someguy1221 (talk) 18:56, 12 October 2012 (UTC)[reply]
Yes, those skeleton types are easily distinguishable, as are others. The "there is no race" POV is based on cultural and ethical, not skeletal arguments. μηδείς (talk) 20:00, 12 October 2012 (UTC)[reply]
I can differentiate tall people from short people based on skeletal morphometry, too (and height has a substantial genetic component); however, the question was about species. Differences in skeletal morphometry do not define species. -- Scray (talk) 20:13, 12 October 2012 (UTC)[reply]
Indeed. Of course there is such a thing as race. But it is not a biologically well-defined concept. I think Medeis has it backwards. The ways that we define races are cultural, and not scientific. The scientific perspective is that the concept of human races (as culturally defined) is not biologically useful or meaningful (e.g. as Someguy1221 describes), not that "there is no race." See Race_(human_classification)SemanticMantis (talk) 20:27, 12 October 2012 (UTC)[reply]
The question is whether different races could be considered to be different species, not whether different races exist. StuRat (talk) 20:19, 12 October 2012 (UTC)[reply]
I don't think the OP is arguing in a technical sense that they are separate species, he seems to be using the terms loosely. It is unlikely that future scientists would describe the races as species, since they would see unmistakable signs of interbreeding and intergradation. But the current general types will still be distinguishable to them in skeletons of our age. The differences are much more distinct than just height, white people aren't just black people with light skin. Scientists can and do distinguish negroid type skeletons from caucasoids and mongoloids and so forth all the time. Distinctions politicians and layman make may or may not correspond. Whatever it is that semanticmantis wants exactly to deny it is up to him to describe clearly. Just to say biologist, anthropologists, and other scientists don't make distinctions of race is either false, overly-vague, or a wish. μηδείς (talk) 01:47, 13 October 2012 (UTC)[reply]
Medeis, no is arguing that you can't classify people as being members of a race, nor does interbreeding and integration have anything to do with it. Rather, race simply has no meaning in cladistics, except as a geo-phenotypically defined paraphyletic grouping. Identifying a person as mongoloid carries about as much taxonomic information as pointing out that a dog is black and fluffy. Someguy1221 (talk) 02:00, 13 October 2012 (UTC)[reply]
Well, seriously, no. Telling me someone is a caucasoid tells me a lot more about what to expect about his skeleton and other statistically likely things than does telling me he's black and fluffy. Perhaps the term terrier would be more closely analogous to a "race" than black and fluffy? As for cladistics not applying to races, that will be a surprise to population geneticists and linguistic classifiers [36] for example. I am not interested in this debate, denying the reality of race is a facile way of claiming scientific sophistication. What is important is what is affirmed, not what is denied. We will see if the OP clarifies his statement. μηδείς (talk) 02:19, 13 October 2012 (UTC)[reply]
The graph doesn't refute either of us. You can take literally any group of living things and construct a phylogeny. I don't know how they constructed theirs, so I can't comment on it. I'm not saying that scientists have not worked with racial classifications in phylogeny, I'm trying to say it's not useful. In layman's terms, the group of people described as "mongoloid" does not include all living descendants of the group's most recent common ancestor, by far. In other words, there are people who genetically belong to the mongoloid classification as much as anyone who is phenotypically mongoloid does. There are even people who are phenotypically mongoloid who genetically fit in better with some other racial classification. So going back to my very first comment, the races are paraphyletic groups. If you knew any taxonomy aside from what you randomly googled, you'd know that no taxonomist would ever intentionally construct a paraphyletic group. For the most part, they only exist because many classifications were conceived before sequencing existed (some newer ones exist because species were ordered in a phylogeny before detailed sequencing was done at all). But I will give you one thing, I went too far when I said race is meaningless to cladistics. It has meaning, but I maintain that "mongoloid" is as much a species/subspecies/any-monophyletic-group as "black fluffy dog". Someguy1221 (talk) 03:38, 13 October 2012 (UTC)[reply]
It's also true that there are monophyletic groups that almost contain all of a given race. This is why cladograms like the one you showed, as well as the ones in our own article on the subject, are so easy to make. Someguy1221 (talk) 03:41, 13 October 2012 (UTC)[reply]
Have a look at this [37] recent assessment of human phylogeny. As depicted in the first figure, human races started varying around, oh, 150,000 years ago. That's a long, long time, but it's nothing compared to the 500,000 years separating us from Neanderthals. Remember - Neanderthals persisted until very recent times (relative to that) so they were a new species. Of course, long ago, there was a time when sapiens and neanderthal were brothers in the same family, and there's a time when any two brothers today, or any two races, could be the prototype of a new species. But the races need not be the prototypes for the split - it is just as possible that a single mixed-race population subsequently divides (the nerds of all races at your local high school launch off into space...). Wnt (talk) 22:57, 12 October 2012 (UTC)[reply]
Actually the biggest distinction among current humans is between Bushmen/Pygmies and everybody else. But even there the level of genetic similarity is much higher than between Neanderthals and Modern Man. Regarding Denisova Man, all we have from them is exactly one finger bone, one toe bone, and one tooth, so pretty much everything we can say about them comes from genetics. Looie496 (talk) 23:02, 12 October 2012 (UTC)[reply]
Despite all the pointless arguing, nobody has hit the main point. No, future scientists will not classify today's humans as separate species, because what counts as a species isn't defined based on currently-living humans. The most common definition of "species" is "a group of organisms capable of interbreeding and producing fertile offspring." There is no question that today's humans can interbreed and produce fertile offspring. Therefore, unless scientists decide to redefine species, today's humans are and forever will be the same species. --140.180.242.9 (talk) 10:38, 13 October 2012 (UTC)[reply]
I'm no expert, but a little searching provided some references that address your questions: [38][39][40] -- Scray (talk) 12:12, 13 October 2012 (UTC)[reply]
Physical process at work when airing out some smokey clothes?
I went to a social event last night that featured a great deal of smoking. Not a smoker, I was annoyed that my suit reeked of cigarettes when I got home. Without giving it much consideration, I hung my suit outside to "air out" overnight. Then I realized I have no idea what is literally happening during this process, meanwhile the outcome is assumed. What happens to the cigarette scent? The particulates don't just magically jump off my suit, do they? Why does it freshen? The Masked Booby (talk) 01:08, 13 October 2012 (UTC)[reply]
Liquid components can evaporate, solids can either sublimate or be blown off. UV light from the sun may also cause chemical reactions, and other scents (like in pollen) may be deposited on the clothes and then disguise the smoke smell. StuRat (talk) 01:14, 13 October 2012 (UTC)[reply]
The word you are looking for is adsorption, the process by which gases and liquids come to cling to surfaces. There is a thermodynamic equilibrium between adsorption sites and adsorbents in the air. In smoky air, the amount attached to clothing will increase until the adsorption sites are more or less saturated. In clean air, the adsorption sites will slowly and spontaneously release the molecules they have been holding. This causes a lingering odor even after the clothing is removed from the smoky environment. The odor dissipates once all the attached molecules have released from the clothing and had a chance to drift away. When possible, washing the clothing is also generally effective at removing adsorbed odors. Dragons flight (talk) 05:06, 13 October 2012 (UTC)[reply]
Also notice that the reason to hang it outside isn't just to deodorize it, but also to prevent the odor from being deposited on other objects inside. StuRat (talk) 06:30, 13 October 2012 (UTC)[reply]
Why inorganic and + (plus sign)
I am confused why we classify CO and CO2 as inorganic compound even when both contain carbon. My another question is - While reading newspapers I always see + {sign} and some small colorful circles at the bottom of each page, where there is no text. I think these + and small circles have some importance, but I don't know what is that importance. Sunny Singh (DAV) (talk) 09:02, 13 October 2012 (UTC)[reply]
CO2 is also commonly created by organic processes, such as eukaryotic respiration. If you have a room full of chemical scientists, you'll be assured to have more definitions of the term organic than there are people in the room. Plasmic Physics (talk) 12:12, 13 October 2012 (UTC)[reply]
Personally, I prefer to define "organic molecules" as a molecule that contains both hydrogen and carbon, without exception. Plasmic Physics (talk) 12:15, 13 October 2012 (UTC)[reply]
That's probably too rigid. I don't think that any chemist I know would classify Mirex as "inorganic", and certainly PTFE would be counted as organic as well, despite not having any hydrogens. - As Graeme points out below, the reason for the organic/inorganic split is the initial belief in vitalism, where the distinction between organic and inorganic wasn't based on atom composition, but on the (erroneous) belief that the materials that made up life had some "élan vital" that made them different from inorganic ones. The "contains carbon" was a post-hoc rationalization for the split. - Personally, my definition of "organic" is more along the lines of "contains carbon, except for a few historical exceptions". The "contains both hydrogen and carbon" might be okay if you altered it to "contains either carbon-hydrogen or carbon-carbon bonds". (As Plasmic Physics says: more definitions than people in the room). -- 205.175.124.30 (talk) 21:14, 13 October 2012 (UTC)[reply]
I know it's just an opinion, but based on vitalism, it seems silly that as a synthetic polymer applied to frying pans, PTFE is considered organic by most chemists. Likewise, Mirex just doesn't exactly scream organic either. Plasmic Physics (talk) 00:02, 14 October 2012 (UTC)[reply]
I added a title, but what is the question ? StuRat (talk) 09:34, 13 October 2012 (UTC)[reply]
I removed your heading, StuRat. Digrpat was answering the second question asked by Sunny Singh— the "+ {sign} and some small colorful circles" are registration marks. Deor (talk) 10:14, 13 October 2012 (UTC)[reply]
OK, thanks, I thought it was a new, misplaced Q. StuRat (talk) 10:24, 13 October 2012 (UTC) [reply]
The organic substances were originally though to be made only by living things, and there were other carbon containing moleculed like hydrogen cyanide or ammonium carbonate or calcium carbide that were classed as inorganic too. Eventually people figured out how to make organic urea and the distinction was blurred. Graeme Bartlett (talk) 12:14, 13 October 2012 (UTC)[reply]
Visual imagination of birth-blind people
Redirect me if this question was asked earlier, but can birth-blind people approximately imagine their daily surroundings, such as apartment they live in? Also, how much correct is a blind person's imagination, can (s)he describe for example a beautiful woman based on clues of his/her life experience?--176.241.247.17 (talk) 09:05, 13 October 2012 (UTC)[reply]
People who are congenitally blind have special skills in mentally-mapping spatial relationships they determine by feel PMID 17368576 and PMID 8124943, but some imagery functions are impaired PMID 11496156 and they don't construct detailed visual mental images in the same way that sighted people do (which can be a hindrance or an advantage, depending on the situation) PMID 16556565. "Beautiful", of course, is at least as much cultural as it is biological. -- Scray (talk) 11:48, 13 October 2012 (UTC)[reply]
Getting an oversized Disk though a circular hole in a bendable material ....
If you have a solid disk (eg like a CD) and you want to get it through a circular hole (eg to get it into a sealed plastic bag) (The plastic is bendable but not stretchable, the disk is rigid) you dont have to have the hole diameter as large as the disk. I know I have tried it.
If you bend the plastic along the diameter of the hole and flex it you can pass through through the hole the larger size diameter disk.
If the whole was infinitely 'flexible' (like a circular piece of string) it could be pulled to make a slit; then, if the circular hole had diameter 'd', clearly the disk could be oversized to a diameter d x pi/2 (approx 1.5d).
But the paper or plastic cannot be moved to give a slit shape... Probably the maximum opening depends upon the 'flexibility of the material with the hole cut into it...
... is there any maths of written in for on this!!??
(The problem has practical purpose as I want to get a flange through a hole into a sealed plastic gas collection bag, link this internal flange to an external flange fitted with a tube to give a gas tight seal - to get a tube for my gas collection bag to get it fit for purpose!)
Thanks email redacted— Preceding unsigned comment added by 78.145.76.1 (talk) 11:08, 13 October 2012 (UTC)[reply]
If the opening of the container is flexible, then we could think about the problem as the circumference of the cross-section of the curved disc (you describe it as rigid, but it can be flexed), which would have as upper bound the cross-section of the flat disc (if d is diameter of the disc and x is the thickness, it would be 2d+2x, but x << d so it's approximately 2d). Curving the disc will, conceptually, shorten one side. Assuming that the disc cannot be curled to overlap, the minimum would be d (with the disc curled around to make a cylinder; obviously, the latter isn't easy with a CD). So, I think the opening needed is bounded by d..~2d, and depends on the flexibility of the disc. -- Scray (talk) 11:35, 13 October 2012 (UTC)[reply]
Scray, I think you are confusing the flexible plastic of the bag with the rigid plastic of the disc. The disc is rigid. The only reason OP can't stretch the hole into an arbitrarily narrow slit is that the material has a finite Young's modulus that resists bending. If the material were perfectly flexible but inelastic, like very fine chain mail, then you could perform the feat. It only seems impossible because the force required increases to infinity as you approach the ideal slit shape - a bit like trying to straighten a clothes line by pulling on the ends. Maths can help you only by telling you how much force it would take to deform the sheet to a given slit shape. --Heron (talk) 15:40, 13 October 2012 (UTC)[reply]
The material has to be stretchable to some degree for that to work. If it isn't stretchable at all, the only thing you can do with it is fold it, and that isn't helpful. Looie496 (talk) 15:28, 13 October 2012 (UTC)[reply]
Agreed, given the constraints of a disk that wont bend at all and plastic that won't stretch at all, the slit in the plastic would need to be as wide as the disk. As far as getting a gas-tight seal, you could try a resealable bag. Those aren't quite a perfect seal, so you might need to add some tape around the edges and corners. You could also use shrink-fit plastic, which shrinks when heated with a blow-dryer. But, again, you may need to use tape to seal up any leaks. And, of course, plastic bags won't hold much pressure, in any case, and will slowly leak small molecules, no matter how well sealed they are. StuRat (talk) 20:54, 13 October 2012 (UTC)[reply]
Hmmm, I'm not absolutely sure that you couldn't expand the slit at all at one point by some deformation of the plastic around the hole that did not involve stretching. That sounds like a non-trivial math problem to me... Wnt (talk) 23:44, 13 October 2012 (UTC)[reply]
Perhaps there's some difference in how we are using the term "stretching". All materials can undergo both elastic and plastic deformation, to some degree, except for a theoretically "perfectly rigid solid" (these don't exist in real life, but crystals come close). Elastic deformation is when a material deforms and then returns to it's original shape. Plastic deformation is when a material deforms but does not return to it's original shape. As the name implies, soft (thermo)plastics tend to have great deal of plastic deformation, but still do have some elastic deformation. I am calling both types of deformation "stretching". Perhaps the OP is not including elastic deformation. In this case, it would be possible to elastically deform some plastics enough to allow a CD to be inserted, and then have the slit reduce back down to the original size. If you make the bag out of an elastic material, you could use a much smaller slit. StuRat (talk) 00:12, 14 October 2012 (UTC)[reply]
Turret milling machine or Universal milling machine..?
Hi I am going to start a new workshop and want to buy milling machine but I want to know which machine will be suitable for me turret milling machine or universal milling machine. My use of machine will be producing flat surface on small jobs of normally 100 X 200 mm. — Preceding unsigned comment added by 14.140.235.82 (talk) 14:02, 13 October 2012 (UTC)[reply]
What will best suit your needs depends on a multitude of factors that we cannot know. Budget? Is this for a new hobby or some sort of small business? What are you going to machine - mild steel, aluminium, special alloys? Plastic? To what accuracy? Do you intend to machine something occaisonally or all day long every day? One would guess from the question that you are a beginner/hobbyist. As such, rather than ask us, a better approach would be to get hold of one or two good trades or hobby level books on machine metal working. Even better, subscribe to journals such as Model Engineer's Workshop for a year or so - you'll learn a lot. Then, join a local hobby engineering group or make contact with an interested tradesman, perhaps someone retired. You question is the sort best dicussed at length with a knowledgable person face to face rather than posting a question to an internet forum. If the highest accuracy is not required, and you only want to do this occaisonally, a better first purchase would be a good pedestal drill. You can fit a low cost X-Y table and milling cutters on a pedestal drill and do quite usefull work at the fraction of the cost of a proper milling machine. However, if your ultimate aim is certainly to end up doing work of professional standard, you should select a machine on the basis of easy upgrade to CNC. Don't forget also, that flat surfaces can be done quickly and very satisfactorily on a lathe, and a lathe can do a lot that a milling machine cannot do. Thats's why there's a lot more hobbyists and small shops that own a lathe as their only machining tool than there are hobbyists and shops that own a milling machine. Are you going to work in plasic, or can the things you want to make be done in plastic? If so, 3D printing is now the way to go. Ratbone60.228.235.209 (talk) 15:24, 13 October 2012 (UTC)[reply]
Europa from Io
Having read the articles about Extraterrestrial skies and Apparent retrograde motion, here's what I'm wondering:
What would Europa's path look like for an observer sitting at Io's antijovian point? It will return to the same position after two Ionian days, and there will be some sort of retrograde motion, but apart from that, I can't really visualize it.
Retrograde motion only appears when you look at something closer to the center than you are -- not the case here. The motion is quite simple. Let's start with the two moons aligned: Europa appears then at the zenith. For about a day, Europa drops toward the horizon. For about two days it is absent. Then it appears on the opposite horizon, and takes another day to climb back to the zenith. (The motion of Io as seen from Europa is much more complicated.) Looie496 (talk) 15:41, 13 October 2012 (UTC)[reply]
Actually, as I think about it, the apparent motion of Io as seen from Europa is not complicated either. You simply see it revolving around the central planet which remains fixed in the sky -- the apparent speed of revolution is exactly half of the true speed. Looie496 (talk) 17:09, 13 October 2012 (UTC)[reply]
Could you clarify what you mean by "Retrograde motion only appears when you look at something closer to the center than you are", Looie. It's the planets that are farther from the Sun than Earth that appear to have periods of retrograde motion (from our perspective); Mercury and Venus don't. Deor (talk) 22:30, 13 October 2012 (UTC)[reply]
Well, we actually have a sextuple bond article, and it's totally news to me. The diagram in the article makes it look like 5 d orbitals and one s orbital are involved. Searching for "sd5 hybridization" and molybdenum turned up [41], which says it is found in HC(triple bond)MoH3; but I've never heard of sp3 hybridized carbon, say, using all four bonds to interact in a two-atom molecule ... but that's not really quite the same. Hmmm. It should be very interesting to hear a serious inorganic chemist comment on this one. Wnt (talk) 20:26, 13 October 2012 (UTC)[reply]
I'm thinking your list of molecules may be hard to define. For example, grab a lump of elemental metal, any metal, in vacuum. Ta-da, instant "molecule", with a bazillion atoms "bound together" to some degree or other. One can argue that fullerenes fall, very loosely, into this category.
Also, I'm not really aware of a [C=C=C=C=C=C=] ring (benzene contains hydrogen, of course). Diamonds are another type of very very large molecule. Wnt (talk) 20:30, 13 October 2012 (UTC)[reply]
Could you clarify the question, i.e. criteria for inclusion? For example, do you include Boron as you do because of Cs2B12H12? If so, that's not really in elemental form, right? Same goes for benzene, as Wnt asks. If you include these, then do all of the atoms of the same element need to be contiguous? I find the "elemental" version of the question interesting, but then the list you gave must be edited. -- Scray (talk) 20:41, 13 October 2012 (UTC)[reply]
Also, do they have to be neutral? If you type "boron clusters" into NCBI you'll get a lot of references; some discuss anions, however. See [42] and [43] for example. I get the feeling (not sure though) that you can pretty much blast boron into any size fragment you like; I suppose this is true of most elements, unless smaller compounds (like N2) are strongly preferred. Wnt (talk) 20:45, 13 October 2012 (UTC)[reply]
Do they have to be stable, or do you also consider at high pressure or other special conditions, high-energy states, and short-lived species? Nature is crazy...she gives us tetraoxygen and octaoxygen. DMacks (talk) 21:32, 13 October 2012 (UTC)[reply]
"The current price per package of tasonermin (Beromun 4 vials 1 mg) is EUR11,813.54. "
Come on! How can 4 mg cost that much? If they are protected by patents, is there a black market somewhere for this? It seems economically more attractive to produce such kind of things, being at 2.5 millions/gram than any other illegal drug. OsmanRF34 (talk) 22:33, 13 October 2012 (UTC)[reply]
Monopoly prices are absolutely arbitrary. (For a shining example of contemporary medical ethics, see Colcrys.) Nonetheless, four milligrams of highly purified, active human protein is not something that is really that easy to cook up in a lab. Note that a specific protein, unlike cocaine, isn't something that you can mix up with gasoline and salt and shake out of solution - you have to baby it through the isolation process to avoid protein denaturation. A misfolded protein wouldn't work - I'm guessing it might even trigger some damaging autoimmune response. I'm not that well versed in business to pull out the commercial details from the company, but my feeling is that if you got a graduate student to whip something up in a week in a basement laboratory, it would cost a substantial fraction of the price, and many bad things could happen.
That said, I can picture alternatives and workarounds. Notably, TNF-alpha can be induced by things like gram (-) endotoxin [44], which is undoubtedly vastly cheaper and more available, though that of course can (will) induce other cytokines in a different pattern than the purified cytokine. From [45] note also that diet affects TNF-alpha production - more omega-3 fatty acids lead to less production in blisters. (I suspect that "dry" cupping therapy is a practice which will be reexamined in the near future, for this and some other reasons e.g. thymosin - the fluid produced by blisters is a who's who of potentially therapeutic proteins, though in other cases they are undesirable. Maybe that's nuts, but then again, I was the only person I knew in the 90s who was soft on Lamarckism :) ) But there are many, many ways to get TNF-alpha production to increase, and I probably haven't thought of the best here. My guess, in short, is that a black market in purified TNF-alpha is not very feasible. Wnt (talk) 23:24, 13 October 2012 (UTC)[reply]
October 14
Hypnosis and alcohol blackouts
Can hypnosis aid in recovery of the memories lost to a blackout drunk? What I've read suggests that they're never properly stored, thus leaving nothing to recall in the first place, but has anyone compared the accuracy of recovered memory to impartial evidence (recordings, etc.)? And if so, what did they find? 71.248.115.187 (talk) 00:29, 14 October 2012 (UTC)[reply]
Thank you Double sharp (talk) 11:07, 4 October 2012 (UTC)
Resolved
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