Wikipedia:Reference desk archive/Science/2006 July 15

From Wikipedia, the free encyclopedia

Humanities Science Mathematics Computing/IT Language Miscellaneous Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions at one of the pages linked to above. This will insure that your question is answered more quickly.

< July 14 Science desk archive July 16 >


Contents

[edit] Bruises

What are some causes of unexplained brusising besides leukimia? 172.131.228.28 02:48, 15 July 2006 (UTC)

  • Unnoticed or unrecalled bumps are the most common (e.g., no pediatrician pays attention to children's bruises between the knees and ankles because all kids have them)
  • Low levels of platelets due to other reasons besides leukemia, such as idiopathic thrombocytopenic purpura
  • Abnormal platelet function, as in thrombasthenia
  • Skin fragility, as in Cushing syndrome
  • Scurvy

alteripse 03:19, 15 July 2006 (UTC)

An abusive relationship. There are creams, though, that'll clear that right up. A restraining order's good to. Black Carrot 04:54, 17 July 2006 (UTC)
Excellent addition. alteripse 00:51, 20 July 2006 (UTC)
An accident while sleep waking.
Phone wakes you up, it is not right by the bed, you trip or bump into furniture in transit, not really remember it happening later.
Any number of accidents that happen when you busy with something else, you say "oh damn" because you hurt yourself, but forget about it because of what you busy with, then later notice the hurt, but have forgotten the situation that caused it to happen. User:AlMac|(talk) 12:41, 21 July 2006 (UTC)

[edit] Megalosaurus name

Why isn't the name of Megalosaurus corrected to Scrotum humanum because that name came to name it first? It it censoring?--Sonjaaa 05:46, 15 July 2006 (UTC)

Our article on Megalosaurus answers this question.-gadfium 06:08, 15 July 2006 (UTC)

So they thought the original name was a joke? How insulting! I think we need to honour the name that has priority, even if it's silly.--Sonjaaa 15:08, 15 July 2006 (UTC)

Yeah. "The Cornwell bone was described again by Richard Brookes in 1763. He named it Scrotum humanum based on its similar appearance to a pair of human testicles (although this name theoretically has priority, subsequent authors have chosen to treat it as a joke, rather than as a serious attempt to propose a scientific name or possibly not compliant with binomial nomenclature but rather with the old, descriptive approach)." --Proficient 18:08, 15 July 2006 (UTC)
I wonder what it is about genitalia that provokes such ridicule and mirth. Their importance is surely self-evident. JackofOz 03:40, 16 July 2006 (UTC)
Really? Do you really wonder? Black Carrot 04:54, 17 July 2006 (UTC)
Yes I do. We all know about the social stigmatisation of sex-related things, which is often turned into ridicule. But why does it have to be that way? If you're going to name something after a body part, why is an elbow or an ear OK, but a dick is not? JackofOz 23:10, 17 July 2006 (UTC)

[edit] LOAD Vs FORCE

hey ppl. can ne one tell me de relation connectin force nd load...... i know that force is directly proportional to load and also that load usually refers to mass or kilograms but then why is it so????


pressure = force/area = newton/meter^2

stress = load/area = newton/meter^2

according to which force and load are considered in terms of newton y ? where ? and how ? has the load of unit "kilograms" become newton ????????

I think you need to forget about the physics and start on your English, buddy =D. No homework help here. Good luck. --mboverload@ 06:05, 15 July 2006 (UTC)
Not having a perfect command of the English language is no reason not to ask a question (although the questioneer could be a bit more careful about typos) and it doesn't look like a homework question (although it may be inspired by one).
The quantities Force and Load are both expressed in the unit Newton because they are basically the same thing. Kilogram is the unit for mass. Only when two masses are attracted to each other is a force excerted, expressed in Newton. A special case is when one of those masses is the Earth, in which case objects with the same mass always have the same weight, with that weight being 9.8 m/s² times the mass. I think this answers your questions. Follow the links for more info. DirkvdM

[edit] Reflexes/Conditioning

First off, my apologies about the subject. They were the closest things I could find to what I describe, but I'm rather certain neither are quite it.

In any case, upon being touched I've noticed that I often have what seems like a reflex action (it's definitely not a voluntary action) to move to defend myself -- not striking the other person or anything, but quickly moving away or moving an arm between me and them. It only happens when the touch is unexpected. Handshaking, when I can see that I am going to be touched or even, perhaps, simply hearing that someone is very close could mitigate the response. My question is what causes this? At first I was thinking a reflex but it is not learned nor exhibited in all humans. Perhaps an example of classical conditioning, save that it's not conditioned. Finally, I was thinking maybe something related to sensory overload, though that may be quite a stretch.

So does anyone have any better possibilities and links for further reading? Thanks.

If this only occurs when the touch is unexpected, one guess is that you're a bit like a cat. They can be so concentrated on something that you can easily approach and startle them. Does this sound familiar? If you're also cool, that would make you a cool cat. :) DirkvdM 10:23, 15 July 2006 (UTC)
Interesting idea, and I'm not opposed to being a cool cat. However, with cats it seems as though the phenomenon is not limited to just touch. I know I've startled my own cat a number of times with just sound, even when he was fully awake. Nor would I say that deep concentration is absolutely necessary, on my part, for the reaction to manifest. Still, do you have any idea on why this is with cats? Perhaps something to do with their more acute senses, though the cat article does not mention anything specifically related.
In nature, cats are prey for many animals. Prey animals tend to be more skittish than the rest, as this helps them survive and pass on their genes. StuRat 19:01, 15 July 2006 (UTC)
Ah. Unfortunately that rather rules out the "cat hypothesis" here; since, in cats, the behavior is due to genetics or evolved behavior, at least, whereas in humans (I am rather sure) it is not.
No need to compare the questioner to a cat; the startle reaction is normal in humans. The article describes a reaction very much like the one the questioner described. The stimulus could be a touch as easily as an auditory or visual stimulus. --Ginkgo100 talk · contribs · e@ 22:24, 15 July 2006 (UTC)
Thank you Ginkgo100, that is exactly what I was looking for. I may have to update the startle reaction article a bit too. A simple google search ("startle response" actually turns up a lot more relevant data) brings up all kinds of information on causes et cetera -- thanks again!

[edit] "Universal resonator"

I'd like to build a little device for a science fair project about resonance. It should be able to automatically detect the resonant frequency of whatever it's placed on (a metal bar, plaque, etc) and apply a force accordingly. Shouldn't be a difficult circuit, but I've been having issues with what parts I'd need, and Googling for it hasn't helped because I don't have the right keywords. Any clue? I'm pretty sure it's been done before and there must be blueprins available online. Thanks! - Anon

Let's see, you need to decide if it will be an analog or digital circuit. Then you'd need:
  • A speaker which can make sounds at a range of frequencies, where the frequency is provided as either an analog or digital signal.
  • A microphone which can return the volume level as either an analog or digital signal.
  • A processor which can control the speaker frequency, initially running thru the full range of frequencies, and record the maximum microphone volume level, then set the speaker to that frequency.
  • Power sources for all devices. StuRat 18:41, 15 July 2006 (UTC)
Wouldn't it be easier with something mechanical, and not acoustic, device? Say a vibration motor of some kind? -- Anon
I wouldn't expect that to be as easy to find as a speaker. StuRat 23:52, 15 July 2006 (UTC)
The problem is not the speaker, it's the complex digital circuit. I'd suppose a non-acoustic approach would be a simpler device. 201.48.113.246 03:12, 16 July 2006 (UTC)
There would be all sorts of overtones (and background noise), so the circuit would require some Fourier analysis to pick out the dominant frequency. Something mechanical might be better. I'm thinking about a vertical string (or at an angle) with a little (light) ring on it. The string could go through different tensions and stabilise (somehow?) at the right frequency. The ring would then wiggle upwards and settle at the first node, giving an indication of the frequency. Of course the tension of the string could also be used, but then you'd have to calibrate that (try different frequencies and see what tension that corresponds with) and it seems a less accurate. DirkvdM 10:10, 16 July 2006 (UTC)

[edit] Mobile Display technology

Any idea how do mobile phones having swivel screen technology transfer all the picture information through the swivel hinge?is it somewhatlike the tv co axial cable?

I suspect a flexible wire is used, which makes it have a limited life. An extremely short range transmission could work, too, but would be more susceptible to interference. StuRat 18:28, 15 July 2006 (UTC)
The swivel is hollow and carries many small wires. --mboverload@ 11:39, 24 July 2006 (UTC)

[edit] radiation of energy from black holes

We detect the radiation of energy from black holes,as they release it in the form of a beam.Does that mean we ONLY detect the ones aligned in the earth direction,but not in the other directions?

Yes, of course, this is true of everything. Our eyes only detect the release of sunlight energy that hits our eyes, for example. Note that the energy detected from a black hole comes from outside the black hole's event horizon, as energy inside the black hole can't escape (except small amounts by Hawking radiation). StuRat 14:27, 15 July 2006 (UTC)
Then how do we know that what we're seeing is a black hole? DirkvdM 08:54, 16 July 2006 (UTC)
We don't. What we do know, however, is that it matches a popular model for a black hole. Of course we don't see the beams from every black hole, but if we can see one we can make guesses as to how many we can't see. Confusing Manifestation 10:31, 16 July 2006 (UTC)
OP: it might be helpful to realize that you are probably not talking about the radiation from the black hole itself, but rather EM radiation from an accretion disk surrounding it or from the double jet associated with many black holes (which is fed by the disk, not the hole itself). If you were lucky enough to find an "inactive" black hole with no accretion disk, perhaps wandering through interstellar space, if you were very close to it, you'd notice of course the strong gravitational field, and optically speaking you'd see a dark disk (surrounded by a thin halo of smeared starlight) moving against the background stars. This disk is not the event horizon (r=2m) but corresponds roughly to r=3m. Oh dear, this probably sounds very confusing, doesn't it? I'm too lazy to draw a picture illustrating this "strong lensing" effect, so I probably shouldn't have said anything at all... oh well... For physics students, you can figure out what I'm talking about from what you read about null geodesics in Chrandrasekhar, Mathematical Theory of Black Holes. ---CH 03:03, 24 July 2006 (UTC)

[edit] Microwave Arcing

Why do metals arc when placed in the microwave?

See here. I can't be bothered rephrasing it, sorry.  Killfest2  14:04, 15 July 2006 (UTC)

[edit] Plank constant

We know that E=hv.But what about two rays of same frequency but diferent amplitute??

Two "rays" of same frequency are made of [photon]]s of the same energy. If one ray is more intense than the other one, it has an higher number of photon moving. This question is strictly connected to the failing of the explanation of the Photoelectric effect with the classic theory and the need of a newer theory 8the quantum theory). AnyFile 17:35, 15 July 2006 (UTC)

[edit] Spleen

What is a spleen and where is it located?Thank you.

Did you try looking at spleen? - Nunh-huh 14:43, 15 July 2006 (UTC)
Indeed. Spleen unsurprisingly has the answer. --Proficient 18:10, 15 July 2006 (UTC)
You don't say. Spleen has that information? Well, who'd have thought it? That a description of what a spleen is would show up in the spleen article. I'm shocked and astounded. Black Carrot 04:49, 17 July 2006 (UTC)

[edit] Vaccine trial length.

There is a vaccine I am interested in. A phase 1 clinical safety trial of this vaccine is planned for the fourth quarter of 2006. If all goes well with this trial and all the other stages of the vaccine trials that a vaccine goes through, how long will it be before people can get it?

I've looked through wikipedia and found only vague answers so far. So, if anyone could tell me the typical time this process takes, they would be very helpful.

---OOPSIE- 15:00, 15 July 2006 (UTC)

There are so many variables that would affect the time, it's pretty meaningless to estimate the time. A wild-ass guess would be 5 years or so if everything goes right. You can see more about the FDA vaccine approval process here. - Nunh-huh 15:10, 15 July 2006 (UTC)

It varies enormously. A safety trial simply means that in a relatively small number of people there is no immediately detectable harm. The bigger challenge is the efficacy and benefit/risk trial. The length depends on the number of people in the trial and how high their risk of the infection and how easy it is to prove they were protected. An example of a "quick" trial would be against a common disease that affected 20% of people in a narrow age range and caused unmistakeable, serious manifestations and there was no good treatment. It would be easy to recruit people and easy to detect the benefit, and approval might happen as quickly as 4-5 years. An example of this type of disease was bronchiolitis caused by respiratory syncytial virus. At the opposite end was cervical papillomavirus, which is currently a topic of controversy in the US and has been in development status for a long time. alteripse 15:14, 15 July 2006 (UTC)

[edit] new article

I would like a critic on submitting this article into your encyclopedia. Galactic Geologic Interval is most conveniently accessible on: http://www.astronomy.com/ASY/CS/forums/1/303875/ShowPost.aspx#303875 It is an assimilation of published datum. —Preceding unsigned comment added by 66.229.133.55 (talk • contribs) 15:57, July 15, 2006

Forgive my criticism, but a critic gives a critique. StuRat 18:23, 15 July 2006 (UTC)
It's not just our encyclopedia, it's yours too. Simply 'submitting the article' might violate copyright. You might use it as a source, but only if it is a trustworthy or reputable source, and I don't get the impression it is. DirkvdM 09:01, 16 July 2006 (UTC).

morbas:I am the author, copyright is no issue.

Looks like a lot of speculation with no real evidence or support. Not very believable either. Seems like just another crack-pot theory.

morbas: Reply to any issues can be had on Astronomy user forums.

Definitely looks like a crackpot theory. But I would suggest you publish your "theory" in a peer reviewd scientific journal. Otherwise it will never be accepted by anyone in the scientific community.

morbas: Is this for emphasis? Also check your spelling.

[edit] Carborised match-stick

Hi! Can you give a precise explanation, why the word 'CARBORISED' is used in some match-boxes? Pupunwiki 17:33, 15 July 2006 (UTC)

Hi, these links suggest carborising matches allows them to be "extinguished with a single puff" leaving "no after glow". I'm not sure what the process involves or whether it is related to carburization though. Rockpocket 18:56, 15 July 2006 (UTC)
If anyone finds out, perhaps they could add it to the otherwise quite comprehensive match article.--Shantavira 09:24, 16 July 2006 (UTC)

[edit] 12 bee lifetimes to make one teaspoon of honey?

I recently read in a magazine that it takes twelve bee lifetimes to make one teaspoon of honey. Is this true?

I did go and buy a jar of honey after reading this, as it would be churlish to ignore somethings life's work.

I wonder what the equivalent would be in human lifetimes work. How many, for example, human lifetimes did it take to build the Eiffel Tower? What about other well-known human artifacts? How many human lifetimes to put a man on the moon?

--81.104.12.4 23:21, 15 July 2006 (UTC)

Apollo is generally cited as 15 billion man-hours. (that's about $9 per man-hour involved, using an inflation-adjusted figure, so it sanity-checks). Call the average human working (as in, paid work) lifetime 20 to 65, forty-five years, at fifty weeks a year, 2250 weeks, then forty hours a week... 90,000 man-hours in a lifetime. This gives you something like 170,000 human lifetimes to put a man on the moon.
Running through those figures again, $15/hr is probably closer to an accurate figure, which knocks you down to nine billion man-hours, or about 100,000 working lifetimes; those 100,000 also would have got you twenty men on the moon (the last three shots were effectively paid for...), not one, but otherwise it's a decent back-of-the-envelope figure. Shimgray | talk | 23:34, 15 July 2006 (UTC)
"fifty weeks a year" - I feel sorry for Americans only getting two weeks holiday (or vacation as you say in American English) as in the Uk the norm is six weeks holday, and even more in other parts of Europe. --81.104.12.4 23:42, 15 July 2006 (UTC)
Woah. Europe has it easy. :P --Proficient 00:29, 16 July 2006 (UTC)
We focus less on making money and more on enjoying it once we have it. DirkvdM 09:06, 16 July 2006 (UTC)
Yeah, fifty weeks is high, but then again this was the US in the 1960s. Also bear in mind I didn't factor in the effects of working overtime, so it's a wash. Shimgray | talk | 13:47, 16 July 2006 (UTC)
Someone like me has to pop up and say that teachers have it even easier. I'm one week into my 8-week summer holiday...G N Frykman 08:14, 16 July 2006 (UTC)
yep and when we get back we can look forwards to 2 weeks off half term , two weeks off christmas, one week off half term 2 - 3 weeks off easter and one week off half term. OTOH the time spent at work is pretty full on, far more so than most other jobs. Theresa Knott | Taste the Korn 08:24, 16 July 2006 (UTC)
Right, and how much to you get paid? So, per hour, how close does it come to evening out? Black Carrot 04:48, 17 July 2006 (UTC)
Teacher's always complain about being low paid But I think they are paid and average sort of wage. In the UK £20 000 to £40 000 for a teacher is about the norm - more for senior management positions. Whether it's close to evening out depends on the school and how long you've been doing the job. In the first year - now way, not for anyone. But in later years in a good school for a well organised teacher it gets considerably easier so that the holidays more than compensate for the term times. Of course the best thing about the job is the warm fuzzy feeling you get when a kid does well. Theresa Knott | Taste the Korn 20:36, 17 July 2006 (UTC)
  1. When counting lifetimes involved in building something, don't forget the workers who died in industrial accidents while on that job.
  2. While teachers pay is below the average of other professions, their pension plans are more generous, unless wiped out by the Wall Street Scandals. At retirement, their income from pension is more than 1/2 what they were paid while working, plus they may work as a teacher in another state, as a part time substitute, without any reduction in pension. Thus somone who was a full time teacher in some big city close to US state line, can work 1-2 days a week across state line just after retirement, and be earning as much or more than when they were full time. This is not available to other professions. User:AlMac|(talk) 12:51, 21 July 2006 (UTC)

[edit] How many square feet of wheat field to make one 800g loaf of bread?

I walked through a ripe field of wheat recently. After removing stalks and husks, it seemed you would'nt get much flour from a wheat ear. Hence my question please. --81.104.12.4 23:37, 15 July 2006 (UTC)

Modern farming should yield in the range of 30-40 bushels per acre. About 45 pounds of flour are extracted from each bushel of milled wheat.EricR 23:52, 15 July 2006 (UTC)
The 5 pound sack of whole wheat flour in my cupboard contains about 75 1/4 cup servings. EricR 23:57, 15 July 2006 (UTC)

According to this recipe, 6 cups makes 2 loaves (3 cups = 1 loaf). According to this, 4 3/8 cups of flour is 125 grams; so 3 cups is 85.7 grams. 85.7 grams is 0.188 pounds. As Eric said above, one acre produces 35 bushels * 45 pounds/bushel = 1575 pounds of wheat. Thus, one loaf requires 0.00011936 acres (about 5 square feet). Raul654 00:10, 16 July 2006 (UTC)

But then you'd be walking around on square feet. And five of them, no less. DirkvdM 09:09, 16 July 2006 (UTC)
I think you've mis-read that website (recipesource.com), Raul - it says that 1 cup is 4 3/8 ounces or 125 grams, so three cups is 375g (which still seems a bit low for a loaf, but does sanity check.) Each acre should yield 1575lb of flour, so if we take the traditional 1lb loaf (to make the sums easier) we therefore need 1/1575th of an acre, which is 27.7 square feet or 2.6 square metres, double those for a 2lb (900g) loaf. For the questioner's 800g (1.76lb) loaf, I get that 4.5m² or 48.8 square feet are needed. Those areas are larger than I would have expected, but I can't see any error. -- AJR | Talk 19:08, 16 July 2006 (UTC)
An area of wheat as big as a large kitchen, to make just one loaf of bread? No wonder there's so much starvation in developing nations. JackofOz 01:51, 17 July 2006 (UTC)
If you think that's scary, work out how much area of land it takes to make a steak. DJ Clayworth 17:44, 19 July 2006 (UTC)
Actually, I'd really like to see that. The amount of energy lost at each trophic level is obviously quite large, but all I've ever seen in terms of an actual number is something like 99% loss, which is almost surely a guess or estimate. If the 99% guess is correct (it's probably on that order of magnitude, at least), then a 16oz steak would require about 2,600m² - about half an American football field. If the loss is more like only 90%, then that obviously only requires 260m². Unless I've messed my elementary school math again.  :) Matt Deres 02:59, 24 July 2006 (UTC)

Thank you for the replies, but you forget that loaves are made with flour and water. They are not completely dry when you eat them. I would try to calculate it myself except I don't understand all these "cups". Its odd that you still use Imperial measures in the US, while the Motherland has been using metric for decades.

If you need metric, they provided it. It's an estimate though, since cups are a unit of volume and grams are a unit of mass. To be honest, I think they answered your question as asked. The other ingredients of the loaf probably won't take up any space in your wheat field. Matt Deres 02:59, 24 July 2006 (UTC)

[edit] Optimum size of grid in trellis fence to reduce traffic noise?

I'm thinking of putting up a trellis fence in my back garden, to mark the line between the cut lawn and the uncut meadow-style grass.

At the end of the long garden is a busy road. I recall from schoolboy studies that sound could cancel itself out (to some expent) by interference by passing through the grid of the trellis.

What would be the optimum size of the grid to best reduce the traffic noise? By size I mean the distance between the wooden laths that would make up the trellis grid. --81.104.12.4 23:50, 15 July 2006 (UTC)

If you are using the trellis as a diffraction grating then it wouldn't cancel the noise out. The interference pattern would be a pattern of dots where in some directions he noise would be reduced ( destructive interference) and in others it would be increased (constructive interference) the exact directions would depend on the frequency of the sound waves. But here's the rub. Noise is a whole range of frequencies. I cannot see how this could possibly work, but perhaps I am missing something? Theresa Knott | Taste the Korn 08:40, 16 July 2006 (UTC)

I was thinking the same. But one important source of noise is the profile edges on the tyre hitting the road, causing a hum. If all the tyres have the same distance between the profile grooves and all cars drive at the same speed, this might still work (to some extent). Suppose 50 km/h and a distance of 5 cm between the grooves. That would make for a frequency of 1 million per hour, which is roughly 300 Hz. Sounds about right. I haven't a clue, though, how that would translate to a grid size for the trellis. DirkvdM 09:20, 16 July 2006 (UTC)
But then you'd still have the same problem of alternating regions of constructive and destructive interference (see the images on diffraction. I'd wager a solid wall might work better to just reflect the sound. Digfarenough 16:38, 16 July 2006 (UTC)
But a wall would be ugly (or might). Plants, however, seem to be quite good at this too. So just let something climb the trellis that grows very fast. DirkvdM 19:00, 16 July 2006 (UTC)

Thank you for your replies. But think about an analogy with a radio telescope. The reflector they use is often (or perhaps always) a metal grid rather than solid metal, presumably because it reflects the radio waves almost as well as solid metal. I expect there is some relationship between the wavelength of the radio source and the size of the grid. By analogy, a wooden grid made the correct size for the sound wavelength could be as effective as a solid wall. The problem is, what is the best relationship between wavelength and lath spacing?

I now see that this article Diffraction grating suggests that the lath spacing should be about the same length as the sound wavelength, whatever that is. Perhaps it would be best to design for the high-frequency noise components in the hope that such a grid would also serve lower frequencies.
What you want is a kind of sonic crystal — we don't seem to have an article on the subject, but you can google for it. Some relevant links I found include [1], [2] and, for a more lighthearted treatment, [3]. —Ilmari Karonen (talk) 02:48, 21 July 2006 (UTC)