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I've found over the years that some people smell very bad to me. I'm not talking about people who're dirty or flatulent or unwashed or have bad breath or have body odor typically associated with heavy exertion and/or sweating; rather, it seems more that some people's body chemistry creates an odor I find extremely unpleasant. It's difficult to characterize or describe; it smells of nothing but "smelly person". I have also noticed that others often seem not to detect any such an offputting smell from the same people I find smelly, at the same time I find them smelly. What's at work here? Is it akin to the ability (or lack thereof) to taste PTC? 00:04, 17 July 2009 (UTC)
It's mostly to do with what you've been eating, what they've been eating and what you're used to. The compounds in many aromatic substances survive just fine in the body and then get exuded with the various bodily fluids, including the sweat we make almost constantly. Curry, for example, has a very distinctive odour and people that eat a lot of it will tend to exude that smell from their breath and bodies. If you're not used to that because you and your family don't eat lots of curry, then you'll be very aware of the change in odour. It works the other way as well: you may be smelling very strongly of milk, or pepper, or any one of a number of things, but you'd be unaware of it because it's part of your background smell. Matt Deres (talk) 13:16, 17 July 2009 (UTC)[reply]
Let's not overlook the smeller's own nose. If you've got too much X in your system, certain odors will repel you more than the usual person. Vranak (talk) 14:35, 17 July 2009 (UTC)[reply]
Is there any downside to adding Benefiber to Metamucil? Are two types of fiber compatible (one is a guar gum and the other is psyllium husks) --70.167.58.6 (talk) 00:08, 17 July 2009 (UTC)[reply]
I'm afraid we can't give medical advice, but I will point out that, baring very unusual circumstances, you can get plenty of fibre in your diet by just eating plenty of vegetables. --Tango (talk) 00:15, 17 July 2009 (UTC)[reply]
I'm not asking about medical advice. I'm asking if mixing compound A and compound B have a chemical reaction or produce any harmful substances. It's a science question, not a health question. --70.167.58.6 (talk) 12:37, 17 July 2009 (UTC)[reply]
You are asking for advice on dietary supplements. That seems like a health question to me. --Tango (talk) 20:14, 17 July 2009 (UTC)[reply]
Not offering any advice here, but consumption of very high levels of fiber (along with inadequate water, I think) has been known to cause intestinal blockages. ike9898 (talk) 17:35, 17 July 2009 (UTC)[reply]
"I'm asking if mixing compound A and compound B have a chemical reaction or produce any harmful substances." -- It shouldn't, cause neither compound is reactive under normal conditions (they're both mostly cellulose anyway, i.e. sawdust). FWiW
76.21.37.87 (talk) 01:51, 18 July 2009 (UTC)[reply]
is there a simple passive filter that would "round off" the lower-frequency square waves (i.e. low-passing the fundamental of the square waves so they would approximate sine waves) without attenuating the higher frequencies?
the nominal human hearing cut-off of 20kHz would suggest that any periodic wave above 10kHz would sound the same since higher harmonics can't be heard (very well). Is this actually the case? If so, are distortion specs on tweeters above 10kHz worth much?
To the first question, yes — a suitable low-pass filter will attenuate the higher frequencies, leaving the fundamental (and lower harmonics, depending on the filter) essentially intact. Here's a YouTube video demonstrating the principle with square and sawtooth waveforms: [1]. The simple RC circuit shown in our article would serve. TenOfAllTrades(talk) 02:47, 17 July 2009 (UTC)[reply]
I’m not sure if I’m understanding your first question correctly, but if I’m correctly rephrasing it, it sounds like maybe you’re wanting the amplitude of the fundamental frequency on the filter’s output to be higher than the amplitude of the fundamental frequency on the input, due to the presence of the higher frequencies on the input? Like by having the filter somehow phase-shift the higher frequencies such that they’ll contribute to the fundamental frequency on output, rather than just being attenuated? That isn’t possible with a linear passive filter, e.g., any filter consisting of just resistors, capacitors and inductors, but it would be possible to do something like that with a nonlinear passive filter.
It isn’t true that any periodic wave above 10kHz will sound the same. For example, an 11kHz sine wave sounds quite different from a 19kHz sine wave. So if a tweeter attenuates those two frequencies differently, that’s going to make an audible difference. Red Act (talk) 03:35, 17 July 2009 (UTC)[reply]
Sorry. English is a dangerous language in unskilled hands.
The toy can produce a wide tonal range but the (555) oscillator produces square waves. I was wondering if the lower frequencies can be (simply) "sine-ufied" without attenuating the higher ones. I'm guessing not.
What I meant was, since a 15kHz square wave is made up of 15kHz, 30kHz, 45kHz, 60kHz, ... sinusoids and nothing above (nominally) 20kHz can be perceived, that any 15kHz waveform would sound the same as a 15kHz sinusoid. Sounds (haha) too easy.
“Not with a linear passive filter” would be an answer to your first question.
That’s true, a 15kHz sine wave would sound the same as any 15kHz waveform, as long as the 15kHz component of the waveform had the same amplitude and phase as the sine wave. However, your original question number 2 asked if distortion specs were worth much above 10kHz. If a frequency response distortion causes the tweeter to disproportionately attenuate the 15kHz component of a sound, that’s going to be audible. Was the 10kHz a typo, and you meant to say 20kHz? If you meant to say 20kHz, then the answer would be yes.
I’m afraid some audiophile is going to come along and point out that some people can actually detect distortion above 20kHz, and I’m sure that’s true, particularly with younger people. But this discussion is a theoretical one based on the assumption that people can’t hear anything above 20kHz. Red Act (talk) 06:56, 17 July 2009 (UTC)[reply]
To provide a mostly-useless answer to the first question: yes. A Fourier series decomposition of a 15kHz square wave shows that the 15kHz component is already a sine wave. The higher frequencies that you desire not to attenuate are what turn your 15kHz sine wave into a square wave (see the animation in square wave). So, if you really seek to turn a 15kHz square wave into a 15kHz sine wave with all the higher frequencies unattenuated, your passive filter of choice would be … a wire. – 74 08:33, 17 July 2009 (UTC)[reply]
The OP is incorrect in supposing that a 15kHz square wave is made up of 15, 30, 45, 60... kHz sinusoids. A square wave has only odd-multiple harmonics i.e. a 15kHz square wave is made up of 15, 45, 75... kHz sinusoids. (Even multiple harmonics exist only if the wave is rectangular.)
I think the OP questions whether distortion of tones above 10KHz matter, i.e. is easily audible, and the answer is no. (A tweeter could produce harmonics starting at 30kHz due to symmetrical distortion or starting at 20kHz due to asymmetrical distortion. Neither is easy to hear.) A different question is whether the tweeter has level frequency response over its audible range because that affects the reproduction of possible harmonic content of all tones below 10kHz, which includes most music.Cuddlyable3 (talk) 01:29, 19 July 2009 (UTC)[reply]
Here in China the voltage is 220V. I've recently bought a Game Boy Micro which comes with a power cord (not an adaptor) to charge the battery saying it should only be used with 110V.
I'm currently using a stepdown converter, but am wondering if this is really necessary.
Why? Because I see kids all over the place playing JPN Game Boy Advanceds and Game Boy Micros and charging them willy-nilly.
I know that improper voltage can hose appliances... but what does it do (if anything) to batteries?
61.189.63.221 (talk) 03:52, 17 July 2009 (UTC)[reply]
Too high a charge voltage could make the batteries blow up, and also fry the dioderectifier that changes the AC from your socket to the DC needed to charge batteries. Stick to using your stepdown converter at all times.
76.21.37.87 (talk) 04:57, 17 July 2009 (UTC)[reply]
Discuss how theories such as those above [Newton's/Galileo's theories about gravity] develop into laws with time & experimental testing.
Now, this is implying that laws are somehow better or more solid than theories. My understanding is that a law is simply a description of what happens, while a theory is an explanation for observations. How would I answer the homework question? (This is going to be marked, and I have NO way of talking to my teacher about the question at any point before the work is due.) --wj32t/c 04:16, 17 July 2009 (UTC)[reply]
It looks to me like your understanding of the difference between a physical law and a theory is more accurate than your teacher’s! Unfortunately, the “theories develop into laws” idea that they teach at some schools does not mesh well with how those terms are actually used by scientists. My impression is that the “theories develop into laws” idea is just something they teach in like junior high or high school, and isn’t something you’d be likely to encounter in college. I don’t know the best way to explain to your teacher that this wasn’t a very good homework question. Red Act (talk) 04:52, 17 July 2009 (UTC)[reply]
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt to solve the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Thank you. —ScheinwerfermannT·C05:00, 17 July 2009 (UTC)[reply]
Thank you for using HumanBrain(r). HumanBrain(r) is one of the most advanced WetWare(tm) systems available. Please note that the new HumanBrain(r) LanguagePack II(tm) (European Languages/English) is now available. LanguagePack II(tm) adds the ability for semantic analysis beyond simple keyword scanning. LanguagePack II(tm) is a free download for your HumanBrain(r). Installation can take between 5 minutes and 10 years depending on existing programming and specific HumanBrain(r) model employed. --Stephan Schulz (talk) 09:27, 17 July 2009 (UTC)[reply]
Judging from the idea that the development occurs after time and testing, your teacher may be confusing the difference between theories and laws with the difference between hypotheses and theories. Maelin (Talk | Contribs) 05:02, 17 July 2009 (UTC)[reply]
As far as marks are concerned, just give what the teacher expects. Assume a Law to mean something like indesputably proved beyond doubt fact of life, and explain how a theory matures into a "Law" over time through tests by experiments and observation. However, afetr you are marked, do have a discussion with the teacher about this. Rkr1991 (talk) 05:31, 17 July 2009 (UTC)[reply]
Seems like a good idea. Thanks for all the suggestions, everyone. :) --wj32t/c 06:03, 17 July 2009 (UTC)[reply]
It’s kind of intellectually repulsive to intentionally give an incorrect answer, but I think that probably really is the best advice. There’s no point in getting marked down just to prove a point, and actually knowing the right answer is what’s really important, anyway, not whether the teacher acknowledges you for knowing the right answer. It’s also probably best to point the teacher’s mistake out to him quietly, after class, rather than pointing it out to him during class. I pointed out a couple of my high school math teacher’s errors in class right after he made them, and it really made him kind of not like me a little. In my experience, college profs are much less flustered by being corrected in class than high school teachers; in fact, they’ll often thank you for correcting their mistake. Red Act (talk) 11:16, 17 July 2009 (UTC)[reply]
Your should tell your teacher (in a tactful way) that their hypothesis that "theories develop into laws with time & experimental testing" is not supported by the way that these terms are used in the scientific community. As evidence, show your teacher these pages - [2], [3], [4]. Clear consensus is that there is no hierarchy of proof or reliability between theories and laws - the only difference in usage (and it is a very marginal one) is that the term "law" is usually applied to a short and concise statement or principle whereas a "theory" is a larger and more complex body of interrelated concepts with a wider, more general scope.
Maybe I am being cycnical here, but it seems to me that the erroneous idea that "theories develop into laws with time & experimental testing" could be used to set the stage for the bogus "evolution is just a theory" argument. Gandalf61 (talk) 11:28, 17 July 2009 (UTC)[reply]
No, here in Australia we aren't anti-evolution :) --wj32t/c 23:59, 17 July 2009 (UTC)[reply]
Well, I think you can do this right and still get good marks - and since you CLEARLY have a better grasp of this than your teacher, I'm strongly of the opinion that you should stick to the truth no matter what. The trick here is to write the truth - and yet still answer what the question is really seeking for you to explain - which is how a "hypothesis" turns into either a theory or a law with time and experimental testing. This is more work for you - but that's what happens when you stand up for a principle.
I think you need to write two sections:
Firstly, you need to deflect the question into one that you CAN answer. You must explain how the standard dictionary definition of the words "theory" and "law" differ sharply from common scientific usage - look the words up in a dictionary - and quote what it says. I found this, for example. Explain that you are assuming that the word "theory" in the question is being used in the non-scientific sense of the word (As Merriam-Webster puts it "6 a: a hypothesis assumed for the sake of argument or investigation b: an unproved assumption". However, you can't make it sound like this is just your opinion because essays like this aren't about opinion. You also can't make it sound like this is something you heard from a bunch of random guys on the Wikipedia reference desk (which it's not because you already knew it). You are going to have to find some solid references that you can point to that say this - preferably more than one. You need to be able to say that "so-and-so (a highly respected scientist/organisation) said such-and-such (which supports your claim) in such-and-such document (hopefully something your teacher can easily find and read - but at least something respectable...but not Wikipedia - which many teachers hate)". For example, you could quote the American Association for the Advancement of Science here - in the section "Is evolution "just a theory"?" - they say "In detective novels, a "theory" is little more than an educated guess, often based on a few circumstantial facts. In science, the word "theory" means much more. A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter or the germ theory of disease. Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.". This clearly says that a theory is a RESULT of time and experimental testing - not the STARTING POINT for such work. That done and clarified, you can proceed to do the assignment you were given - because you can't use this little misunderstanding to duck out of doing the work!
Now, having established (eg from Merriam-Webster) that the word "hypothesis" would be a better choice, you must proceed to explain how a scientific hypothesis can develop into either a scientific theory OR a law with time and experimental testing...because that's what the homework assignment is all about - and if you don't do it, you won't get a good grade. You've actually increased your workload in the process - because now you need to describe how a THEORY gets made as well as how a LAW comes into being. But it's worth the effort.
I'm 99% certain that your efforts will be rewarded with a decent grade IF you do it like that - subtly and with style and integrity - and not whining at the teacher's incompetence!! On the off-chance that you have an utterly bone-headed teacher (I sure hope not!) - you might ask your teacher to "help you understand" by providing an example of a "theory" that turned into a "law" - we know that there aren't any - so you're on solid ground here - you may have to say "but that wasn't a theory - that was just a hypothesis". If all else fails, you may need to get your parents to appeal the grade to a student councillor or the head of the science department - or the principle...whatever it takes. I had to fight for my son's (correct) answers to bogus questions on many occasions...and every time, we won and he got a good grade in the end. But if you do it right - and back up your assertions with solid references - I'm sure you'll be OK without any fuss whatever.
You're in good company by the way - my personal hero (Richard Feynman) was particularly displeased with these kinds of errors in assignments and school books and took on a personal crusade to try to eradicate them that wound up with him having to write three of the best Physics books in existance - "Feynman's Lectures on Physics". The fight over the teaching of evolution in US schools lies entirely in the misunderstanding (intentional or not) of the word "theory". I applaud your knowledge and your desire to stand by your principles. No matter what, you'll always know that "You were right" - and that's worth more than a grade.
Thinking about this a little, my guess is that the OP’s textbook is correct, which is where the OP got his correct information from, and it’s just the teacher that’s made a mistake. If the textbook matched the teacher, the OP wouldn’t have gotten confused and asked us for a clarification. So pointing the teacher’s mistake out to the teacher might be as simple of a matter as pointing out the pertinent page(s) in the textbook. Red Act (talk) 14:52, 17 July 2009 (UTC)[reply]
Well, the homework is actually taken directly from our science syllabus. Pretty depressing, I know... --wj32t/c 00:01, 18 July 2009 (UTC)[reply]
Also intriguing is Galileo's report, based on experiment, that balls of unequal weight do not only fall at different rates, but that the lighter one initially pulls ahead of the heavier one until the heavier catches up. In the early 1980s the science historian Thomas Settle tried to repeat Galileo's falling-body experiments and, astonishingly, noted the same thing. He suggested that fatigue induced in the hand holding the heavier object tends to cause this hand to let go more slowly, even when the dropper believes the objects are released simultaneously.
I'm a bit confused. Is this actually true, or is the article just saying that Galileo observed it but it's wrong? Why would this (the lighter one being faster at first) happen? --wj32t/c 06:20, 17 July 2009 (UTC)[reply]
If the two objects are mechanically released at precisely the same time in a vacuum chamber, the two objects will fall at exactly the same rate, even initially. The effect of the lighter one falling faster initially only applies to the sloppier situation in which the objects are dropped in air, by hand.
The fatigue hypothesis seems reasonable to me. Another hypothesis that seems reasonable to me is that it isn’t due to fatigue, per se, but that it takes longer for a tightly clenched hand to unclench than a lightly clenched hand, simply due to it involving a greater change in physiological state. Another hypothesis that seems reasonable to me is that when one’s fingers move rapidly out from under something really light, something like the Bernoulli effect will basically cause the feather to get sucked downward slightly. But the latter two hypotheses are purely original research. Red Act (talk) 07:22, 17 July 2009 (UTC)[reply]
Galileo's result is only approximate because he couldn't test it in a vacuum - and air resistance has an effect. But done 'properly' with some kind of mechanical release system in a vacuum, there would be no such effect as our OP describes. SteveBaker (talk) 13:12, 17 July 2009 (UTC)[reply]
Didn't Galileo roll same sized but different weight spheres down an incline, rather than merely dropping things? The effort of holding on an ioncline would not be great. A mechanical release would be an obvious control. Ref checking is indicated. Edison (talk) 14:41, 17 July 2009 (UTC)[reply]
1) how to calibrate and standardise visible spectrophotometer using aquous solutions?
2) which aquous solutions should be used for it? and what should be their concentrations? —Preceding unsigned comment added by Ddrcpan (talk • contribs) 06:56, 17 July 2009 (UTC)[reply]
I believe you calibrate by putting a test tube with distilled water, which will reflect, refract and absorb the minimal amount of light of any liquid, into the machine and taring it so that that whatever is reflected, refracted or absorbed is blanked. DRosenbach(Talk | Contribs) 17:19, 17 July 2009 (UTC)[reply]
Someone else may have asked something similar already, sorry if this is a repost!
I'm going to be observing the solar eclipse next week and I hope to take some footage/pictures, and I'm just wondering how careful I should be. I've got a recent Canon Ixy (Powershot) just so that I can have some sort of video record, and I will be photographing using my Nikon D60 and a 200mm lens. I've never photographed an eclipse before so I'm not really expecting anything spectacular (besides it won't be complete where I live) but I'm mainly concerned for the safety of my cameras! Basically every website I look at warns me that the eclipse could harm the lens/sensors of my digicam, and I guess I need a solar lens? of some sort to protect them, but what exactly am I looking at purchasing here, how much will it set me back, and where can I get one? Also, is it possible to make my own? If anybody knows a site with some easy instructions to make a home-made eclipse glasses, please let me know! And lastly, is it really necessary to use a solar lens for a digicam, or is that just a precaution for when you're getting in really close? Thanks! 210.254.117.186 (talk) 08:31, 17 July 2009 (UTC)[reply]
What do you mean by "getting in really close"? The distance to the sun won't change. I can assure you that taking pictures with a normal digicam without any filter will destroy the sensor of the cam. When there was a total solar eclipse here in germany, where I live, two friends of mine destroyed their cams in this way. NEVER look at the eclipse with your naked eyes, use an appropriate filter! In germany there were special glasses on sale weeks before the eclipse, which were certified to protect human eyes. Normal sunglasses won't do! It might seem that the sun is "dark" enough, but in reality it isn't. You will damage unprepared optical equipment, including your eye, if you point it to the eclipse. There are cases in the literature where people went partially blind from staring into an eclipse, so I'm begging you not to take the risk of loosing your sight. --TheMaster17 (talk) 10:10, 17 July 2009 (UTC)[reply]
I don't know about damaging the sensor - I think that quickly pointing the camera, taking the photo and then pointing it away again should be OK...but perhaps it's not worth the risk. But in any case, the problem is that in a non-total eclipse, the amount of light coming from the sun will overwhelm the sensors and you won't get a decent picture. Digital cameras can only handle so much light before they have hit the maximum number that the sensor can output and everything goes completely white. So I think you could benefit from having a filter of some kind to cut the amount of light down to something reasonable. You could test this by trying to take photos of the un-eclipsed sun...which will be only maybe twice as bright as a half-eclipsed sun. Obviously (I hope!) you understand that staring at the eclipse with unprotected eyes is very dangerous - and looking at it through your camera's optical viewfinder is possibly even more dangerous...especially if you have an optical zoom. By all means line up the shot using the LCD viewfinder if your camera has one...that's entirely safe. I've been saying this a lot recently - but I'll say it one more time. Observing the sun (and even photographing it) can be done very effectively by projecting an image of it through a pinhole into a darkened room. If you have a window facing where the sun will be during the eclipse - you can tape some thin (preferably black) cardboard to the windows to make the room completely dark - and poke a small pinhole into the cardboard to let in some sunlight (this is effectively just a 'pinhole camera'). This will project an image of the sun onto any flat, white surface held up in front of the pinhole - which you can move closer to make a smaller but brighter image or further away for larger and dimmer. You can also make the image brighter - but fuzzier - by slightly enlarging the pinhole - dimmer but sharper by using a finer pinhole. It's easy to experiment. You won't hurt your eyes or your camera by looking at this image. It's very cool (especially now that the sunspots are coming back) and everyone should do this at least once - eclipse or no eclipse! Using a conventional camera with flash turned off and a 'macro' or 'closeup' lens setting if your camera has one - lets you take photos of the projected image that will look really great. Best of all, you can get everything set up and take practice photos of the uneclipsed sun any time to be sure you have everything right for the big day. That's a good idea - because you only have a few minutes to get what you need - and you don't want to be fiddling around getting the camera settings right. Just be sure to do the setup at the same time of day as the maximum amount of totality that's predicted so you'll have the best-facing window for the event. SteveBaker (talk) 12:51, 17 July 2009 (UTC)[reply]
I forgot a piece of pinhole camera advice. To get a really SHARP image - cut a square hole a couple of inches across in your cardboard and tape some aluminium kitchen foil across it. Then punch your pinhole in the foil. It makes a much smaller and more accurate hole for the ultimate in sharpness. SteveBaker (talk) 13:09, 17 July 2009 (UTC)[reply]
Total solar eclipse during totality, March 29, 2006, Sallum, Egypt, Playing with double shadows during an eclipse You can use an ordinary camera to take pictures during a solar eclipse. Be sure to SECURELY mount a piece of #14 welder's glass in front of the camera (Not the side with the display the other side i.e. before the light hits the camera.) I tried a mylar filter last time and was unhappy with the results. (It was expensive but buckled and got me reflections on the images.) Friends used the welder's glass and got awesome pictures. Since your eclipse is not total you don't have to worry about removing/putting on the filter arrangement during the event. That usually makes for more difficult constructions. Build yourself a solid frame or box. Sticky tape or Duck tape are not suitable for this task. Make sure absolutely no light can enter the setup except through the welder's glass. There are many things to observe apart from the sun turning into pac man. See if you can spot double shadows as in my pic. (No the guy was not Aquaman or an alien with extra knuckles between his fingers:-). Have fun, but be safe. --Lisa4edit (talk) 15:40, 17 July 2009 (UTC)[reply]
Thanks Lisa, I'll see if I can find me some welder's glass then and make a little box for it. 210.254.117.186 (talk) 16:12, 17 July 2009 (UTC)[reply]
is there a true difference between regular cables (hdmi, USB, internet) and those made by "boutique cable" manufactures that include gold plated connectors?
puzzles me is that the cable is still copper so would any benefits from the gold connectors be negated by the copper wire?
im looking for scientific reasons (from a metallurgy, engineering perspective) for a difference or lack thereof. Im not looking for an audiophiles perspective, they tend to buy anything if its expensive. seems as though they are victim to the the placebo effect.
EDIT
so it seems that gold plating prevent corrosion, makes sense, but is there any true sound difference between monster cable(and similar cables) and normal priced audio cable.
one of the claims ive heard is that with monster cable you hear "more of the nuances of the music"
Well, for digital signaling, there is no difference. All decent cables that follow the standards are plenty good enough to carry the digital signal. Boutique cables for digital signals are a scam. For analogue transmission, cable quality can make a difference. But even there, gold plating is not going to have a significant difference. If you can hear the difference between decent and overpriced cables, James Randy has ONE MILLION DOLLARS for you.[6] --Stephan Schulz (talk) 11:39, 17 July 2009 (UTC)[reply]
The gold plating isn't actually that expensive - you can get fairly cheap gold plated cables if you want.
The gold plating ensures that the connector will not corrode or rust, but a rust free alloy would do just as well.
There's and additional complication that a junctions between different metals have properties (eg think thermocouple) - which potential could actually degrade the signal - in practice there is not a difference.83.100.250.79 (talk) 11:49, 17 July 2009 (UTC)[reply]
It's probably a good idea to match the platings - ie if a device has tin plated connections then don't use gold plated connectors.83.100.250.79 (talk) 11:55, 17 July 2009 (UTC)[reply]
The theory to gold plated connectors is that gold resists corrosion better than copper, so gold plated connectors can wind up having a lower contact resistance than copper ones, particularly in a damp environment. I have had a 50-year-old copper phone connector corrode to the point that it made for a staticky phone connection, and perhaps that problem wouldn't have occurred had the connector been gold-plated. Of course, digital devices become obsolete way before they’re that old. Red Act (talk) 12:20, 17 July 2009 (UTC)[reply]
Gold plating is most useful on cables you will need to plug and unplug often. Gold is soft and will somewhat lubricate the connection as it slides in and out. For connectors that stay in place for most of their life - that are maybe unplugged when you move house or something...meh - any old cable of the appropriate standard will do. The most ridiculous thing is when audiophiles claim to be able to hear the difference between gold plated cables and the regular kind. Audiophiles have a problem. They are like most of us geeks who love to debate the merits of Linux versus Windows or MINI Cooper's versus Mustangs - to endlessly tweak the object of their joy to get another 1% of performance out of it...except that their field of interest is 'solved'. We can't buy the perfect car or the perfect computer - but we can all have essentially unlimited quantities of perfect (in the sense of 'better than human perception') audio at any time we want from a sub-$100 box that you can buy at any Walmart. There is nothing left to be geeky about...no conceivable reason to rush out and buy this years sexiest $10,000 stereo system beyond the shape of the knobs and the color of the LED's. Sadly, these people retreat into a world of their own where they claim they can tell the difference between two ethernet cables used to connect their PC to their media center (yes, really!) when it's a completely lossless digital connection with error recovery built in at the software level. These people will happily pay $1000 for a set of cables just so they can "one-up" their audiophile buddies. Check out these [7] nut-jobs who sell cables with silver conductors instead of copper at hundreds of dollars for what would normally be a $1 cable. Their advert reads: "These cables allow deeper insight into the textures of the critical mid-range, leading to improved intelligibility of vocals, greater resolution of acoustic spaces around the instruments, more real-sounding instrumental timbres, etc. It’s not only beneficial on acoustic instruments – it also gives greater insight into studio techniques, the timbres of synthesisers and guitars etc. Nuance and emotion in vocal and instrumental performances come to the fore."...completely ridiculous of course. It's actually rather sad. SteveBaker (talk) 12:30, 17 July 2009 (UTC)[reply]
The bullshit related to cables is legendary, but I'd say that nothing can top the $485 wooden volume control knobs they were pushing a few years back: [8]. Alas, these knobs are no longer being sold by the original manufacturer. TenOfAllTrades(talk) 14:16, 17 July 2009 (UTC)[reply]
I have restored telephones and telegraph equipment over 100 years old. Soldered connections still conduct. Tinned connections screwed together generally still conduct. Bare brass or copper may develop surface oxidation which insulates, even though no gross corrosion is seen. A goldplated connection should still work fine after that interval. Ordinary audio connectors, with copper inside and some silvery looking outer conductor (tin?) or the connection of vacuum tube pins in their sockets can become oxidized and noisy after ten years or more. Gold plating would likely help maintain continuity. Edison (talk) 14:39, 17 July 2009 (UTC)[reply]
In general there are some bad cables - in my experience once problem is that caused by metal connector shields (the plugs) - on analogue video I've found these to sometimes give noticeable (really noticable) noise.
Only buy ones with a insulating plastic plug - these are often the cheapest.
one experiment, audiophile listeners could not distinguish between short Monster cables and ordinary coat hangers.
Use your common sense - nothing worth the money raises suspicions.83.100.250.79 (talk) 18:44, 17 July 2009 (UTC)[reply]
I have found that it makes a difference, probably because of oxidation resistance leading to less static etc, plus more expensive cables tending to generally be better-made than the cheapest ones. Cables with gold plated connectors cost a few bucks extra if you shop around and I think it is worth it to do so. I wouldn't get the scammy ones where they charge several times more for a lot of marketing crap. They're basically the same cables. 67.117.147.249 (talk) 00:50, 19 July 2009 (UTC)[reply]
Where and to who would you report a valid UFO Sighting? —Preceding unsigned comment added by Chromagnum (talk • contribs) 11:12, 17 July 2009 (UTC)[reply]
There’s no need to report a UFO sighting, as governmental and scientific organizations will just assume that it’s just yet another natural event that people have gotten overly excited about because they can’t immediately identify it. However, some of these UFO organizations will probably be happy to hear about the “sighting”. The Unidentified flying object article lists some phenomena that might help you make a guess as to what the thing actually was. Red Act (talk) 11:27, 17 July 2009 (UTC)[reply]
If you have a video or at least a picture of the thing, someone here might be able to help you identify it as being ball lightning or a meteor or whatever. Or was it all over too quickly to take a video or picture of it? Red Act (talk) 11:35, 17 July 2009 (UTC)[reply]
A UFO (in the original sense of "any flying object that you can't immediately identify") is a singularly irrelevant event. A UFO (in the more modern sense of "a flying saucer") is essentially certain to be a case of you failing to correctly identify a UFO (in the old sense of the initialism)! In either case is it no more than a passing curiosity. The curious thing about the modern use of "UFO" is that people almost always use in the sense of "A flying object that I've already identified as a flying saucer"...hardly 'Unidentified'! Unidentifiable flying objects might be more interesting! Anyway - as Red Act says - the old 1960's idea that these things had to be reported to the air force or something is long gone. Tell your friends - find a bunch of flying saucer nut-jobs and tell them - but nobody else gives a damn. SteveBaker (talk) 12:02, 17 July 2009 (UTC)[reply]
As my old father used to say (ex-RAF) any FO that is not I is a UFO (or any Flying Object that is not Identified is an Unidentified Flying Object) and it remains a UFO until it becomes I. --TammyMoet (talk) 19:23, 17 July 2009 (UTC)[reply]
My father was ex-RAF too - and he used to say the same thing...I suppose it was something they were taught. SteveBaker (talk) 00:08, 18 July 2009 (UTC)[reply]
I've seen two "flying saucers" recently, and both turned out to be USAF aircraft (one was a Blackhawk chopper, the other one a C-17 Globemaster). 76.21.37.87 (talk) 02:02, 18 July 2009 (UTC)[reply]
I saw a UFO once about 10 years ago, while I was out walking the dogs with my girlfriend one night after dark. A reddish-orange object made a rapid, curved arc through the sky. The UFO remained unidentified for about 5 or 10 seconds – until I got close enough to see that there was a house in that direction, and I saw the person sitting in the second-story window of that house, who I realized had just flicked a still-lit cigarette butt out the window. Red Act (talk) 02:30, 18 July 2009 (UTC)[reply]
I'm working at a hotel and a thermometer in the hot tub broke, leaking some blue, oily substance into the tub. It didn't look anything like mercury but I don't know enough about mercury to know whether it's possible to make it look blue and.. oily. I've heard they often use semiconductors in thermometers although I won't vouch for that.
What do you suppose the liquid substance is? What should I do? Should I clean the tub with water, soap.. should I close it indefinitely? --88.149.11.100 (talk) 12:17, 17 July 2009 (UTC)[reply]
It is an oil, nothing special. Mercury is silver and doesn't in any way behave like an oil. It rolls and, if spilled into a tub, will quickly roll down the drain. Use a cleaner for oils (most kitchen cleaners work well). -- kainaw™ 12:42, 17 July 2009 (UTC)[reply]
Are you sure it's an oil? I didn't know they could be used in thermometers. If you're sure then this should be all right but I would like to get a confirmation just to be sure, nothing personal Kainaw :) --88.149.11.100 (talk) 13:00, 17 July 2009 (UTC)[reply]
There are two common types of thermometers used in this sort of application. The cheap ones use a bimetal strip. Those are usually obvious because they have a dial display. The more expensive ones use an oil. They tend to have a digital display. Even if it is a bimetal strip, an internal lubricant oil is used to keep the strip from sticking to itself. Neither design uses mercury. In fact, it is rare to find mercury in thermometers. If you go look at them in the store, most are digital, many have a red oil, and a couple might have mercury (if you are lucky - I haven't actually seen a mercury one in a long time). Also, if it were mercury, it would behave like mercury. Mercury is very heavy. It quickly goes to the lowest point on any surface. By quickly, I mean that it appears like it has intelligence and is racing towards a destination. In a tub, the lowest point is the drain, so it would quickly roll straight down the drain. -- kainaw™ 13:09, 17 July 2009 (UTC)[reply]
According to Alcohol thermometer, "The liquid used can be pure ethanol or toluene or kerosene or Isoamyl acetate," with an added dye.--Shantavira|feed me 13:11, 17 July 2009 (UTC)[reply]
I've run into mercury thermometers every now and then in labs; but they're generally only used in certain applications where the temperatures get into hundreds of degrees celsius - it's generally not used for more mundane applications because of its now-recognized toxicity. I also agree with Kainaw that if it was mercury, you'd know it - mercury behaves very differently to the other liquids you encounter in everyday life. It was almost certainly some kind of dyed oil or alcohol that may be slightly poisonous but will do nobody any harm if diluted in a tub of water. ~ mazcatalk 13:33, 17 July 2009 (UTC)[reply]
My dad used to show me the mercury from mercury thermometers when I was younger, but it sounds like they're not as common any more. When I think about it it would probably sink if it were mercury but my first thought was to ask- I didn't really want to take any chance with this. Thanks for your helpful answers though :) I cleaned the tub and everything seems to be all right now, I'm more knowledgeable about thermometers now which is never a bad thing ;) User:BiT --88.149.11.100 (talk) 15:39, 17 July 2009 (UTC)[reply]
Please explain what chewing xylitol-containing gum helps with dry mouth? Does the xylitol do something specific? --Reticuli88 (talk) 14:32, 17 July 2009 (UTC)[reply]
This is probably just marketing hype. Xylitol (q.v.) is merely an artificial sweetener. Chewing practically anything (apart from dry foods that absorb water) will stimulate saliva production.--Shantavira|feed me 15:09, 17 July 2009 (UTC)[reply]
(Not entirely hype - see below.)
The sweetness is designed to make you salivate. Xylitol is used because it is sweet, and less likely to have the problems associated with using normal sugar:
One possibility for this is that bacteria that can metabolise are rarer (or don't exist) compared to bacteria which can metabolised sucrose or glucose - reason being that xylitol is a 'new' sugar...83.100.250.79 (talk) 15:33, 17 July 2009 (UTC)[reply]
Xylitol is a sugar alcohol. The cooling effect described in the article may provide added relief. Since Xerostomia includes tooth decay as one of the symptoms. chewing gum with sugar is probably not a good idea. I don't know if the existing bugs have trouble with the "alcohol" portion of the sugar alcohols. Hand sanitizers are made from alcohol gel, but the "sugar" part may counterbalance any antibacterial effect. Lisa4edit (talk) 16:09, 17 July 2009 (UTC)[reply]
Sugar alcohols are not anything like hand sanitizer alcohol. It's not really the sugar alcohol acting like a poison. Cavities are caused by acid producing bacteria. These bacteria can't process Xylitol because it's not food so there isn't "alcohol's antibacterial effect is canceled by the sugar feeding effect".129.64.55.234 (talk) 16:39, 17 July 2009 (UTC)[reply]
Thanks. Do you know how they differ? I had thought the "alcohol" group at the end interferes with some part in the bacteria's membrane. Could you clarify the process and explain why it doesn't do what it does for sugar alcohols? Lisa4edit (talk) 17:50, 17 July 2009 (UTC)[reply]
Think you're just wrong. sugar, cellulose etc all have lots of alcohol groups, and they don't interfere with bacteria as far as I know. You should present some evidence that what you thought is actually true, rather than expecting people to provide responses based something that you haven't provided any evidence to be true.83.100.250.79 (talk) 18:22, 17 July 2009 (UTC)[reply]
looking for information on a type of water-powered hammer[edit]
I saw a type of water-powered hammer used for striking coins. It was water-powered, but not a trip hammer. It consisted of a big beam with a heavy weight on one end (the hammer) and a bucket on the other end. Water poured into the bucket, and when it would get full, it would sink down, lifting up the weight. Then, when it would get to the bottom, the water would pour out of the bucket and the hammer would drop. I thought it might be a trip hammer, but that's based on a cam and a rotating shaft, which this didn't have.
I wouldn't refer to that as a water-powered hammer. I would refer to it as a gravity-powered hammer. It doesn't matter what raises the hammer (water, rocks, a mule...), it is gravity forcing the hammer down to produce the desired result. Unfortunately, Googling for "gravity hammer" will not return any useful results. -- kainaw™ 16:39, 17 July 2009 (UTC)[reply]
The drive is under Water scoop (hydropower). There's no mention on specific names for the tools/equipment driven, though. Lisa4edit (talk) 16:53, 17 July 2009 (UTC)[reply]
When did it become common knowledge among reasonably well-educated people that mercury is highly toxic? When I was a child, a broken thermometer meant *FUN*, since my mother would let my brother and me play with the mercury that came out. Its behavior was so alien (the little spheres coalescing into larger spheres, etc.), that it provided hours of entertainment. Now when I hear of a mercury leak at a school they shut the whole thing down and send in the guys in hazmat suits. Should my mother have known better in the late 1970s? If it matters, she was Rhodesian/Zimbabwean, a nurse, and we lived in Brazil. Thanks. --Sean 23:11, 17 July 2009 (UTC)[reply]
It was already a big deal when a thermometer broke in our house in the late 50s early 60s. People have varying attitudes toward risks. Risk assessment is not just done in the documented orderly way described in out article, but happens in our heads pretty much constantly. Different people and cultures come to different results. We happily take our kids on trips in cars, but cringe or cry child abuse when we see someone hand a machete to a toddler in a stroller. The comparatively delayed and remote risk of mercury poisoning may have paled when compared to more immediate severe risks your mom encountered every day. You may still have fared better than some who made a big fuss, because one method of removal was vacuuming up the mercury, which of course made the problem a whole lot worse. Out of sight and out of mind wasn't out of the air. Lisa4edit (talk) 16:37, 17 July 2009 (UTC)[reply]
Years ago it was common for high school chemistry students to play with mercury, rolling it around in the hand. If a thermometer broke, kids played with the glob of mercury rolling it around on the floor until it disappeared into a crack. If it broke in a kids mouth, they just spat out the mercury and glass fragments. It was claimed (by a family doctor years ago) that the elemental mercury in the thermometer was not in a form easily absorbed by the body. On the Mr. Wizard TV show in the 1950's the kids learning about science were commonly exposed to mercury, as in the electromagnetic "jumping spring" where it was used for electrical contact. The splashing and sparking could have put a fair amount into the air. Many electrical experiments/demonstrations work vastly better with mercury than with brine or just metal to metal contact. It is hard to replicate some of the early electrical work of Michael Faraday without mercury for a friction-free highly conductive electrical connection. Probably in the 1970's some of these science demos became things the kids read about instead of things they saw or did. Likewise mercury manometers were previously used in high school physics and chem labs to measure pressure or to demonstrate barometer function. Perhaps dial or electronic pressure transducers replaced them. It was well known in the 1800's that chronic mercury exposure caused brain damage ("Mad as a hatter") but it was probably assumed that brief exposure did not have lasting effects. Mercury/silver amalgam fillings are still in millions of mouths. When did they stop putting mercury in tooth fillings? Edison (talk) 19:13, 17 July 2009 (UTC)[reply]
When I took high school chemistry in the early 1970s it was still the way Edison describes it. So mercury is toxic; big deal, you won't get enough exposure to matter. Today the attitude is to err much more on the side of caution. --Anon, 19:21 UTC, July 17, 2009.
I found an article from December 1963 about the U.S. Public Health Service banning a toy which contained drops of mercury. It says "If the toy should break and scatter mercury beads in hidden areas the fumes from the element could cause brain damage." A 1960 article behind paywall also cites a toy pulled from the market by authorities because it contained mercury.So I'd say it was "common knowledge among well informed persons " by then. But pretty much ignored by most for years after, like the dangers of smoking or the need to wear seat belts when driving. By 1970 there were numerous stories about the danger of trace amounts of mercury in fish and mercury vapor from spills. In the 1960's the U.S. used more mercury in pesticides than other countries, which were banning it after health problems were noted. Edison (talk) 19:31, 17 July 2009 (UTC)[reply]
In 24 BI (before internet), facts did not spread so easily. Whereas today we can google information on mercury, or other things to find information, back then it was much more difficult. Googlemeister (talk) 19:54, 17 July 2009 (UTC)[reply]
Which date exactly are you using as the start of the internet epoch? As far as I can tell, Unix epoch is the closest thing - the "internet" has no clean event which marks its beginning (first router? first TCP packet? first domain name lookup? first www server? first html render?) Any of these types of events can be counted as the start of the internet. Nimur (talk) 22:18, 17 July 2009 (UTC) [reply]
Your mention of car seats gave me a chuckle, since my mom also put us kids in "car seats" similar to old-skool drive-in trays, where we were just kind of hooked loosely onto the back of the driver's bench seat for reasons not of safety, but of getting a better view out the windshield. :) --Sean 23:11, 17 July 2009 (UTC)[reply]
I played with lawn darts! (Hint: when the other guy throws, it's good to be paying attention.) And had a chemistry set with dozens of poisonous substances. And rode a bicycle hundreds of times and never had a helmet or padded knees and elbows. And speaking of bench seats, remember when as a kid in the back seat you could roll down your window more than an inch and a half? Everybody's afraid of everything now. 69.245.227.37 (talk) 07:25, 18 July 2009 (UTC)[reply]
I also played with a chemistry set that had a whole bunch of poisonous substances, like NaOH pellets, 3M HCl, two different ferrocyanates, and copper sulfate (I remember wondering what copper sulfate tastes like, but my dad told me that it's poison, so I didn't try it). Also, I played with mercury when I was little (and I'm none the worse for it, I must say). And I actually raced my bike, downhill on a busy street, without any helmet (and then braked it with my sneakers, it had a really unreliable coaster brake that didn't always work). And once I rode on a train's rear buffers with a 50-pound pack on my back. And another time I flew over the mountains of Alaska in a tiny little single-engine plane (didn't do any piloting, though). And occasionally I've handled (dilute) HF with my bare hands -- no gloves, no goggles, no nothing! Must I add that I'm into martial arts? Reckless?! No, just taking calculated risks. 76.21.37.87 (talk) 07:58, 18 July 2009 (UTC)[reply]
As far as I know, organic compounds of mercury are highly toxic and accumulate in the brain. Metallic mercury or its ions are still toxic but much less and is a hazard mainly for the kidneys, as good or bad as most heavy metals. Many people living today have mercury in there teeth. Compact fluorescent lamps contain mercury, too. I guess the released amount from a shattered one is in about the order as the vapours from a shattered mercury thermometer. So I wouldn't panic when a thermometer breaks. The other thing is the mercury drop going down the sewer and finally distribute itself to the environment. 93.132.138.254 (talk) 08:22, 18 July 2009 (UTC)[reply]
I agree with you 100% that the hazards of metallic mercury are overrated and that it's not such a big deal if a thermometer or a light tube breaks. But I must warn you that dumping mercury down the sewer is a bad idea cause it'll go into the water and any fishes that swallow some will turn it into methylmercury and get poisoned (maybe even die) and also become poisonous for us people to eat. If I had a mercury thermometer (light tube, Ignitron, whatever) and it broke, I'd just gather up the mercury into a jar and turn it in for toxic waste disposal.
Is the pH of vinegar too high to attempt Fischer esterification with ethanol and vinegar over a hot frying pan? The yield prolly wouldn't be too good, but since what I'm aiming for is flavor detection, an equilibrium product of 0.1% (at room temperature) would do very well.
Or is this something to be done in barrels where you wait for years? John Riemann Soong (talk) 15:25, 17 July 2009 (UTC)[reply]
There is this story on some wikipedia page about a mother warning her kid about lots of things not to do while she's away including not to put jelly beans up his nose. He had never done that so he immediately had to try. So, I won't link the page and I hope you don't want to know this for any unhealthy reasons that came to my mind. Lisa4edit (talk) 16:22, 17 July 2009 (UTC)[reply]
I don't think pH has as much to do with it as Ka which measures the strength of the acid. The acid catalysts listed in Fischer esterification have very low Kas. Maybe you should try it. The reaction takes a long time in aging wines but if there's heat applied, the reaction might speed up and produce just enough for your needs. —Preceding unsigned comment added by Coolotter88 (talk • contribs) 16:57, 17 July 2009 (UTC)[reply]
You actually need to know the equilibrium constant for
Acetic acid + ethanol <> ethyl acetate + water
Acetic acid will promote this reaction - even Ammonium Acetate can promote this type of reaction - however the speed of the reaction may be slow - I recommend a pressure cooker - doing this you will get an equilibrium amount of ethyl acetate - whatever that is - the trick is to have as little water in as possible.83.100.250.79 (talk) 19:25, 17 July 2009 (UTC)[reply]
Is Ka that important? See I thought it was H+ concentration that catalysed the reaction but possibly I guess acid strength would be important to help prevent a reverse reaction even in favourable pH. Also, it's ethanol and vinegar -- common edible solvents -- and I expect the majority of my yield would be my starting reactants (discounting evaporation) -- why would it be dangerous? I mean, I add vinegar to all sorts of ingredients with active essential oils and flavors all the time. If I added something that was pseudohygroscopic -- flour or some kind of starch -- I guess that would help absorb the water? (It would also fry, but hey.) John Riemann Soong (talk) 23:13, 17 July 2009 (UTC)[reply]
How can lidocaine have been identified as the source of a bitter taste, when it comes in a solution of HCl, which is acid? I thought acid is sour and bitterness is associated with alkaline? DRosenbach(Talk | Contribs) 17:15, 17 July 2009 (UTC)[reply]
Nah...didn't provide any insight whatsoever. Was there something in particular you thought this article would do to answer the question? DRosenbach(Talk | Contribs) 19:30, 19 July 2009 (UTC)[reply]
One way: the taste occurs when lidocaine is injected intravenously or subcutaneously. There need be no direct involvement of taste sensory neurons, as there might be if topically applied, and there is no change in pH when injected, as the HCl is quickly dissociated and buffered. - Nunh-huh 21:48, 17 July 2009 (UTC) (Addendum: pH of Lidocaine HCl injectable without epinephrine is about 5.0-7.0 in the bottle).[reply]
What about the pH of lidocaine 1:100K epi? Other than your addendum, your response serves as no real answer to my question. DRosenbach(Talk | Contribs) 19:30, 19 July 2009 (UTC)[reply]
My response is a real answer to your question. Perhaps if you can tell me why you think it is not, I can explain it more clearly. Or perhaps the problem is my understanding of you question, in which case perhaps you can explain it more clearly. The pH of injectable lidocaine with epinephrine is about 3.3-5.0 - Nunh-huh 09:29, 21 July 2009 (UTC)[reply]
The article says it is a salt of Hydrochloric Acid. I'm not sure but I don't think there is any Hydrochloric Acid being injected in your mouth. The slightly less than 7 pH of Lidocaine HCl is probably because HCl is reacted with a weak base. Coolotter88 (talk) 16:52, 20 July 2009 (UTC)[reply]
Hi there!!
I would like to know what material on the moon's surface makes it white. Or is it just the strong light of the sun that makes it so? Please help me out.--Lightfreak (talk) 17:55, 17 July 2009 (UTC)[reply]
The moon is mostly Feldspar which is white. But there are also black rocks too.83.100.250.79 (talk) 18:16, 17 July 2009 (UTC)[reply]
This is an image of the moon showing how bright the bright parts are and how dark the dark parts are (But see comment at (XX))The sliver of moon rock at the air and space museum
The moon is not white; it's black, or more precisely very dark gray. It only reflects about 10% of the light that hits it -- an object you would call white would reflect something more like 90%. If you visit the National Air and Space Museum, they have a slice of moon rock you can touch, and you can see the color.
However, human color perception is relative. An object is judged to be light or dark in comparison to the things around it. This means that when an object is seen against a much darker background, like a light in the sky, it is impossible to see it as having a "dark" color like brown or navy blue or dark gray. You see red or yellow or blue or, in this case, white.
--Anonymous, 19:33 UTC, July 17, 2009.
This picture shows you how appearances can be deceiving with regards to brightness. Vimescarrot (talk) 19:46, 17 July 2009 (UTC)[reply]
You can also visit the article feldspar and look at an image of a lighter moon rock ! 83.100.250.79 (talk) 20:33, 17 July 2009 (UTC)[reply]
(XX) The image caption "showing how bright the bright parts are" is misleading. All large areas of the Moon are black to dark gray, it's just that some parts are even darker than others. The photo was made with an exposure sufficient to show detail on the surface -- the same sort of compensation that our brain does automatically, so it reproduces the way the Moon appears to the eye. If there was a true white object in the photo, large enough to see, it would look grossly overexposed. If the exposure was made correct for the white object, then the image would show how dark the Moon really is. --Anon, 22:48 UTC, July 17, 2009.
And by the way - you are very weird - a picture of a whitish moon is no good, but a picture of someone touching a triangle is. Fucking wierdo.83.100.250.79 (talk) 00:26, 18 July 2009 (UTC)[reply]
So basically, it is the strong light of the sun as well as the dark background that makes it appear white. Thanks!!!--Lightfreak (talk) 11:12, 18 July 2009 (UTC)[reply]
If you ever visit the Exploratorium in San Francisco, California, they have an exhibit that consists of a picture of the moon that has accurate reflectivity. Compared to other objects around it, it looks very dark. But you can flip a switch that isolates the background to darkness and shines a bright light on the moon, and it looks bright, just as it does in real life. The difference is striking. (At least, this exhibit was there several years ago.) -- Coneslayer (talk) 15:42, 20 July 2009 (UTC)[reply]
If you want to know what the color of moon "really', what the colors of planets "really" is very tricky. Human perception changes depending on the enviornmental conditions. We have had this discussion in the past--69.228.145.50 (talk) 00:55, 21 July 2009 (UTC)[reply]
Moon article says there are spherical glass beads in moondust that make it brighter. Jay (talk) 10:40, 22 July 2009 (UTC)[reply]
Somewhere I've seen a recent snapshot of Earth and Moon together as seen by some space-probe; the Moon is brown. —Tamfang (talk) 02:21, 30 July 2009 (UTC)[reply]
Why is chlorophyll green? --Lightfreak (talk) 18:14, 17 July 2009 (UTC)[reply]
Our chlorophyll article has some info about the optical properties. The nature of any molecule is to absorb only certain wavelengths (colors) of light (affected by structure, pi bonds, non-bonded electrons, and metal atoms, among others). The nature of chlorophyll is to absorb several "non-green" colors, so what's left is green. DMacks (talk) 19:38, 17 July 2009 (UTC)[reply]
That still leaves the question of why chlorophyll absorbs those non-green colors and not green. (Why hasn't evolution "tuned" chlorophyll to absorb green light.) Turns out that short wavelength light (the blues and violets) contain a lot of energy, so it makes sense to absorb those. On the other hand, as a blackbody radiator, the sun puts out most of its radiation (number of photons) in the lower wavelength region (the reds, oranges, and yellows), so you'd want to capture that as well. What's left is the stuff in the middle (green), which isn't particularly energetic, nor particularly prevalent. While it would be best to capture those wavelengths too (making plants black), they don't give enough of a benefit to drive evolution to that point. This analysis changes with different the different emission profiles of different stars. I vaguely recall news reports about research which hypothesized what colors plants on extra-solar planets would be, given the above considerations. -- 128.104.112.87 (talk) 19:57, 17 July 2009 (UTC)[reply]
In respect to the many colors of the spectrum, chlorophyll, while being the most prevalent pigmented substance in plant cells, is not the only. Xanthophylls (yellow) and carotenoids (orange/red) also exist -- they are what cause dying leaves to appear other colors besides green once the chlorophyll begins to disappear at the end of the season. All together, they allow leaves to absorb and use light of all colors, albeit in low levels. DRosenbach(Talk | Contribs) 19:35, 19 July 2009 (UTC)[reply]
Actually I believe it's because of the constraint of the photoreceptors, and because chlorophyll evolved in the ocean (and established enzymes are hard to modify), and the ocean provides a color filter of its own. I believe there's an explanation that states that green light in sunlight was actually too intensive in the ocean for it to be useful -- in the sense that it would be overly damaging to the pigment itself, so chlorophyll evolved in a way *not* to absorb too much of it. If you look at http://en.wikipedia.org/wiki/File:Solar_Spectrum.png you can see that sunlight actually has a lot of green light relative to the other wavelengths. John Riemann Soong (talk) 23:08, 17 July 2009 (UTC)[reply]
Per a news story[11], antigovernment protestors in Tehran were "lighting cigarettes and putting them in front of one another's faces to ward off the effects of the tear gas." Is there any merit to this belief? I was told that tear gas effects are worse if you rub the facial skin and especially the eyes, so swim goggles are useful to keep it out of the eyes, and that since it is a powder and not a gas, an N95 respirator mask provides some protection to the lungs, better than a bandanna over the mouth and nose but clearly not as good as a gas mask. I was also told that water to flush the eyes was useful. But what possible protective effect would come from cigarette smoke around the face? Edison (talk) 18:40, 17 July 2009 (UTC)[reply]
Vaseline on the skin is also an old recommendation from demonstration organizers, but about as many sources say it makes the teargas worse, sine the material gets dissolved in the petroleum jelly. Other demonstration organizers in the past recommended vinegar or baking soda[12]. Any reliable sources? Not much useful and referenced info in the Tear gas article. Edison (talk) 18:57, 17 July 2009 (UTC)[reply]
I don't know - but I know that heavy smokers can have a reduced response to some stimulants/allergens (tear gas stimulates a response rather than actually being harfull I think) - eg smoking can stop allergies such as pollen hay fever.. However I think you need to actually smoke some cigarettes for this to work.. Just a guess.83.100.250.79 (talk) 19:21, 17 July 2009 (UTC)[reply]
Conversely, smoking (or smokers...not sure if it's an effect of the smoking at the time or of the result of some long-term response to smoking) reportedly makes one more able to detect cyanide. Not that cyanide is being used on the protesters (I hope!). DMacks (talk) 19:41, 17 July 2009 (UTC)[reply]
WARNING, ANECDOTAL EVIDENCE FOLLOWS I used to be in the United States Air Force. Airborne Battle Management to be exact. Since we were flying around, directly above the battlefield they had us go through the same training the Combat Controllers (the USAF's version of Navy Seals, Army Rangers, etc). This training included frequent trips to the gas chambers. I believe the gas in the chambers was CS gas, but they also used tear gas on us occasionally. I am, and have been for a long time, a heavy smoker. Before I went in, I smoked a cigarette. When I came out, I smoked a ciggarette. My eyes watered. My friends were dripping with mucous.
I'd like to believe I was just a badass, but smoking probably does reduce the effects of the gases.DrewSmithWhat I've done 04:14, 18 July 2009 (UTC)[reply]
It could be that either (a) the cigarette smoke desensitizes the mucous membranes, making them less susceptible to the effects of the tear gas; or (b) the nicotine actually has a toxic effect that is opposite to that of the tear gas, and so acts as an antidote. I'm not really sure about that last part, I got to look it up. BTW, CS gas is tear gas.
Just looked it up -- nicotine does stimulate the sympathetic nervous system, which would tend to suppress tear secretion -- so you could say that it acts like an antidote. FWIW
What does sine (mathematical equations?) got to do with this?174.3.103.39 (talk) 06:11, 18 July 2009 (UTC)[reply]
Where did you see the word "sine"??? 76.21.37.87 (talk) 06:50, 18 July 2009 (UTC)[reply]
It's in Edison's first answer second question above, and is very obviously a trivial mis-type of "since." 87.81.230.195 (talk) 13:52, 18 July 2009 (UTC)[reply]
If you carry a sine in a riot they hit you on the head, besides throwing tear gas. I saw a cop do this, and he was obviously outdoors a lot because he was a tan gent. Edison (talk) 20:02, 18 July 2009 (UTC)[reply]
"If you carry a sine in a riot they hit you on the head, besides throwing tear gas." -- Especially if it's an obtuse sine... :-D 76.21.37.87 (talk) 23:58, 18 July 2009 (UTC)[reply]
"I saw a cop do this, and he was obviously outdoors a lot because he was a tan gent." -- Oh, I get it now (didn't at first)! HAHAHAHAHA! ROFLMAO! 76.21.37.87 (talk) 00:56, 19 July 2009 (UTC)[reply]
Someone should have to cosign before you make such an acutely horrible pun. --Sean 14:18, 20 July 2009 (UTC)[reply]
Why do most airspeed indicators have the unit knots, even when they are not naval aircraft? Why not mph or kmph? Googlemeister (talk) 19:24, 17 July 2009 (UTC)[reply]
See the article Knot (unit), in particular the section on Modern-use. ny156uk (talk) 19:48, 17 July 2009 (UTC)[reply]
Ok, why was it changed from miles to knots? Googlemeister (talk) 19:51, 17 July 2009 (UTC)[reply]
From the article:
...its retention for nautical and aviation use is important for navigational reasons, since the length of a nautical mile is almost identical to a minute of latitude. As a result, distance in nautical miles on a navigational chart can easily be measured by using dividers and the latitude indicators on the side of the chart.
It's not clear to me that it was "changed" from mph, but I don't know the history. Tempshill (talk) 19:56, 17 July 2009 (UTC)[reply]
The article mentions that the US used to use miles and then changed, but that could well be an American aberration. Algebraist 20:34, 17 July 2009 (UTC)[reply]
In an era of cheap calculators and flight control radar, what is the benefit of something being "almost identical to a minute of latitude?" Does that "almost" keep you from smacking into a mountain in the clouds, or "almost" get you to a landing strip on some speck of land in the Pacific before you run out of fuel? It's hard to see why such approximate navigation would be very useful today. Edison (talk) 21:41, 17 July 2009 (UTC)[reply]
Useful? It's useful because it is a functional and standardized measurement of airspeed. Unless you are asking, "why doesn't the worldwide aviation system shift from knots to kph as a measurement of airspeed," which is a different question. Tempshill (talk) 22:15, 17 July 2009 (UTC)[reply]
It's basically just history - the seafaring roots of the nomenclature and the (then) convenience when using maps for long distance travel. Nowadays, it's just something that's way too embedded in expensive physical objects (planes, control towers, etc) and in the brains of their operators to change. Aircraft often remain in service for 30 years - and their pilots are around for a similar amount of time - any change-over period would take decades to achieve. Worse still, it would require approval internationally since aircraft spend a lot of time going from one country to another. They also measure altitude in feet rather than meters. It's hard to imagine what benefit there would be from such a costly and difficult change. SteveBaker (talk) 00:03, 18 July 2009 (UTC)[reply]
I recall reading something years ago about how because of the way your brain is wired, physical pain in the stomach can lead to emotional depression. sounds kinda fishy, but i remembered reading it because i'm profoundly hungover and also a bit bummed out. thanks
70.122.109.186 (talk) 19:55, 17 July 2009 (UTC)[reply]
Any continual pain or illness or disability can lead to depression potentially - but I'm not aware of anything specific about the stomach, and doubt it very much.83.100.250.79 (talk) 20:22, 17 July 2009 (UTC)[reply]
While we can't diagnose your specific condition, you are also asking if this link might be true. I doubt it. The problem (and one reason why we can't give such advice) is that depression can be caused by physical (brain chemicals) or psychological (ill family member, etc.) causes. The latter, of course, being more about the fear of loss, the empty part of your life if that person dies, etc.; yes, there is a "feeling in your gut" that can be related to concern over that family member, but it would be a symptom, not a cause, of depression.
Also, see our article on Memory - what you read might be coming to you in a different form than you read it. Maybe that's why it seems fishy; you're not recalling it the way it was.
Finally, if you are "profoundly hung over" from a drinking binge, for instance, you may be experiencing guilt - and feel you shouldn't have done that. That can cause pain in your gut, too. In which case, I will refer you to the only medical advice on our site."It hurts when I do this." "Then don't do that. :-) Somebody or his brother (talk) 00:11, 18 July 2009 (UTC)[reply]
Nietzsche wrote something to the effect of 'the Holy Spirit resides in the entrails'. I couldn't agree more. Though when you're suffering from indigestion and depression you probably aren't too interested in philosophy. I recommend cutting back on your meat intake until you feel better. It's not trivial to digest, and there are a lot of unscrupulous men out there who will raise profoundly unhealthy animals to be fed to undiscriminating people. It's an evil business sometimes but it's been the way of things for so long that nobody bats an eye. Vranak (talk) 23:58, 18 July 2009 (UTC)[reply]
