Wikipedia:Reference desk/Archives/Science/2008 July 22

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July 22

vapour adsorption refrigeration system

i want detailed information regarding this non cinventional refrigeration system —Preceding unsigned comment added by 117.98.108.28 (talk) 01:19, 22 July 2008 (UTC)

Try googling "vapor adsorption refrigerator." I found this PDF which seems rather detailed [1] 71.77.4.75 (talk) 01:33, 22 July 2008 (UTC)

We have an article on this: Absorption refrigerator.

Atlant (talk) 12:56, 22 July 2008 (UTC)

The brightest question on the science desk!

One of the joys of having a young child is attempting to field their damnably simple questions. I've gone through the blue sky, the twinkling stars, how tires get made, and what that bug was doing to that other bug, but I'm stumped tonight. What is the most "apparently bright" thing to be seen in the world? We were experimenting with a magnifying glass on a clear sunny day and the question came up if the sun was the brightest thing in the world (yeah, I know, but if it's in the sky, it's part of the world as far as she's concerned...). Now, I don't want to get into quasars and absolute magnitude because that's not what she's looking for. Is there any light she could experience that is brighter than the sun on a clear day? Searches online come up with some interesting homemade flashlights, but they don't specify how bright they are compared to the sun. Matt Deres (talk) 01:26, 22 July 2008 (UTC)

The initial flash of light from a nuclear explosion? You may not want to *actually* show her that one, though... :) --Kurt Shaped Box (talk) 01:35, 22 July 2008 (UTC)

Since people sometimes use welder's helments to view solar eclipses, I'd guess a welding arc and the sun have similar brightness (not that I'd make any recommendations about how to view an eclipse, I'm no expert.) In both cases, UV light is a significant aspect of the problem. --Gerry Ashton (talk) 01:42, 22 July 2008 (UTC)

Some types of arc welding are a good deal brighter than the sun. But that probably doesn't help you, you're not likely to buy an arc welder just for this, and it's not really safe to 'experience' up close anyway.

I think there are some lights designed for film-making that are available pretty cheap that are brighter than the sun at close range. Actually, I'll bet that at close range many photographic flashes appear brighter than the sun. A photographic flash would at least have the virtue be easy and relatively safe to demonstrate. Might be seen as a cop-out, though. APL (talk) 02:20, 22 July 2008 (UTC)

Er, using common sense when it comes to "close range", of course. APL (talk) 02:32, 22 July 2008 (UTC)-

I'd go with a really powerful laser. The amount of light produced isn't all that much, certainly less than a nuclear flash, but if you point it straight at her eye, I imagine far more light would hit her retina than from a nuclear flash. I wouldn't demonstrate that one either, though! --Tango (talk) 01:45, 22 July 2008 (UTC)

Apparent brightness varies dramatically with distance. While our distance to the Sun won't vary all that much, I'd expect any rather bright light to appear brighter than the Sun if you put your eyeball right up to it (not recommended for those who wish to keep their vision). Some particularly bright lights would be search lights. A specific case is the spotlights pointing upwards from the Luxor casino in Las Vegas, which are bright enough to see from 275 miles away. I'd expect that your eyeball would explode from the heat if you put it right up to those lights. StuRat (talk) 01:47, 22 July 2008 (UTC)

Actually, apparent brightness does not vary at all with distance; see my post below. --Bowlhover (talk) 05:45, 22 July 2008 (UTC)

Apparent bightness/apparent luminosity sure does vary with distance, perhaps you were thinking of absolute brightness/absolute luminosity ? The reasons why apparent brightness decreases with distance are that the light spreads out, so that less of it hits your eye at larger distances, and that dust and other particles absorb more light the farther it travels. StuRat (talk) 14:27, 22 July 2008 (UTC)

I was referring to surface brightness, which is what most people mean when they discuss the brightness of a emitter or reflector. --Bowlhover (talk) 08:12, 24 July 2008 (UTC)

Ok, that concept is that the brightness of any given apparent area stays the same, regardless of distance. However, as the total apparent area increases, the total apparent brightness of an object increases (when the distance is reduced). They also seem to have assumed there are no particles to absorb the light, which is a valid approximation in some regions in space, but never valid when looking through the atmosphere (the more atmosphere you look through, the more light will be blocked). So, in short, this method doesn't apply to the question, which was about the total apparent brightness of objects on Earth. StuRat (talk) 13:10, 24 July 2008 (UTC)

All the examples above will suffice as more "apparently bright". Are you just talking visually bright? You might explain spectrum and point out how the sun can burn every part of your body within about 15 minutes - that's pretty hard to beat.

And when you're talking about what's brighter - I hope and am absolutely sure you've explained that we never, never look right at the sun to see how bright it is. The brightness of the sun itself is already past the scale where you only see how bright it is once, so that's the very most important lesson. I'm sure you've explained that, it's worth saying again!

And that said, as far as a light source where you can see ambient light, unlike a laser (any of which can also easily destroy your vision if viewed directly, but cast no ambient light) - an arc-welding flare is a good demonstration of a very bright light cast all around (again, never look at the arc!) and is impressive indoors; a film-projector bulb; a spotlight. Now take anyone of those, look near them in broad daylight - do you see a difference? Likely not. The sun pretty much rules them all.signed byFranamax (talk) 02:56, 22 July 2008 (UTC)

When we were kids, and there were no adults around, we regularly competed to see who could stare at the sun for longest. I have never had any resulting eye problems - I'm already in old age - and wonder whether there is some protective mechanism at work? I think the taboo is wrapped up in a myth that deserves closer scrutiny. 196.2.124.253 (talk) 19:56, 28 July 2008 (UTC)

Lightning flash possibly? I know from experience that burning magnesium wire outdoors (so my eyes were already light adjusted) can be bright enough that I can't look at it directly. 71.77.4.75 (talk) 02:33, 22 July 2008 (UTC)

Those are both good, but if we agree that the sun is bright enough that we can't look at it directly, I interpret this question as "what makes other things look brighter than they do in broad daylight?" Perhaps the best test of this then would be - will this other light source cast a shadow behind something in broad daylight? So if I shine the searchlight or burn the magnesium on one side of a car, without (!) looking at the light source, but just looking at the car, at noon on a clear day, will I see a shadow being cast? Is that a realistic criterion? Franamax (talk) 03:07, 22 July 2008 (UTC)

That makes sense but again distance seems to make it more complicated. I don't remember the shadows clearly but I am pretty sure the light from the burning magnesium was powerful enough at close range to overpower a shadow cast by the sun in broad daylight. I tried to find some videos of burning magnesium in broad daylight. Here is a video of a small ribbon burning (it's enough to cause the auto brightness-senser of the camera to dim). Here is a contains-mild-swearing video of a bunch of adventurous gentlemen burning quite a bit of magnesium in an outdoor oven in midday. 71.77.4.75 (talk) 03:32, 22 July 2008 (UTC)

My thing is not "does it fill in the sun-shadow?", it's more like "does it cast a shadow the other way?" - but we may be talking about the same thing. There's no indication of that in the video by the league of gentleman adventurers, but they missed out on the fact that piping a feed of pure oxygen into the centre of their little pyro-fest would have dramatically enhanced it. If they'd used a little pure O2 in fact, they might have been able to incorporate ambulances into the footage :)

You're right about distance, as are all the above - but the OP is looking for answers for his little girl, and has ruled out distance via quasars not being applicable (and I'd say gamma ray bursters anyway). However I'd say Mg in O2, arc welding and possibly plasma torch welding would be the most accessible real-life demonstrations of comparable light sources. Now compare that with the fact that from 93 million miles away it takes the Sun a half hour to send you to bed feeling bad all over. (Leaving aside nuclear devices, which are best left unexplained until after the talk about sex - at least you can give a realistic reason for the purpose of sex) Franamax (talk) 05:20, 22 July 2008 (UTC)

I don't understand the need to be secretive about the purpose of nuclear weapons. People sometimes don't like each other and they fight to kill. I certainly knew that years before I was taught the details of sex. --Bowlhover (talk) 06:52, 22 July 2008 (UTC)

Just on the surface, that's a difficult subject for a child - 'cause the natural next question is "will someone try to kill me?". But you miss the major benefit of nuclear weapons - it's not to kill, it's to cause massive numbers of hideously wounded casualties, which tie down the resources of the defending power. Sit your young child down and read her Hiroshima by John Hersey. Explain to her how a fallout cloud would make her own hair fall out and how long it would take 'til she started vomiting and trace out on her face where the flesh would be melted to the bone. Were you taught those details when you were seven years old? Franamax (talk) 07:22, 22 July 2008 (UTC)

I never claimed that every single detail about nuclear weapons should be taught to a seven-year-old. In fact, most educated adults don't know how long it would take for nuclear bombs to cause vomiting or exactly where a person's flesh would be melted to the bone. Telling a child that nuclear weapons are used for war, or even that they waste the enemy's resources by killing civilians, requires none of the details you mention. And come on, "will someone try to kill me?" Any form of crime is more of a disconcerting topic than war unless the child's country happens to be in a nuclear war, and you can't possibly say parents don't or shouldn't inform children about crime.

Besides, the major benefit of nuclear weapons isn't forcing the enemy to provide disaster relief. It's either intimidation, or destruction of the enemy's military, economy, AND civilian population, with a focus on the first. --Bowlhover (talk) 08:24, 22 July 2008 (UTC)

Just a note for any casual readers: Do not ever look directly at the Sun; do not ever look directly at a welding arc or plasma arc; do not ever look directly at a projection bulb, especially through a focussing lens; do not ever look at the direct output of a laser of any type; do not ever look at burning magnesium metal. Doing any of these for any significant length of time can cause permanent damage to your vision. In some cases, this can be as little as 1/10th of a second (in some cases less). Use appropriate eye protection. Read instructions, ask experts, take precautions. Don't try to experiment because of something you read on Wikipedia - please! Franamax (talk) 05:33, 22 July 2008 (UTC)

Note that looking at the Sun without optical aid rarely causes permanent eye damage (see Sun#Observation and_eye damage). Burning magnesium is, as I showed below, 1/29th as bright; it is also much smaller than the Sun in angular size. Since burning the metal is a common high school experiment and was done without goggles in my former school, I would be surprised if it's dangerous. --Bowlhover (talk) 06:52, 22 July 2008 (UTC)

It is dangerous, which is why you're told not to look at it directly. The thing is, looking at the sun or a magnesium flare will damage just a part of your retina each time, causing a small permenant area of blindness. Over time you can acquire more of these until it becomes noticable. Don't look directly at the sun, and don't look directly at burning magnesium. 79.66.124.253 (talk) 17:00, 22 July 2008 (UTC)

The brightest light source on Earth or elsewhere is the laser described here, which can output 10^22 watts per square centimetre for a tenth of a trillionth of a second.

The "brightness" of an object, by the most common understanding of the word, is the amount of light emitted per unit of angular area. As distance from a light source increases, both the light's intensity and the source's angular area decrease with the square of the distance. The result is that brightness, termed surface brightness in astronomy, does not depend on the amount of space between the source and the observer. The shadow test is thus inaccurate because it measures irradiation, not the power of light in one unit of angular area.

Burning magnesium is significantly dimmer than the surface of the Sun. According to its article, magnesium's combustion temperature is 2500 K. A calculation using the Stefan-Boltzmann law reveals the Sun's photosphere, at 5778 K, to be 29 times as bright. --Bowlhover (talk) 05:45, 22 July 2008 (UTC)

Part of the lessons of live, i think she was asking for this [2]. Mion (talk) 08:47, 22 July 2008 (UTC)

I guess the article discusss it but looking at the sun directly is usually does not cause permanent damage but can be particularly dangerous during an eclipse where the lack of ambient light means the pupil may not dilate sufficiently. It's also likely to be very dangerous if you have just be given something to dilate the pupil (causing mydriasis), e.g. as part of an eye test or have taken some drug (this includes atropine and amphetamines) or have a disease (e.g. Argyll Robertson pupils, Marcus Gunn pupil, Adie syndrome) or whatever resulting in the condition. All in all, while most people are probably not going to suffer damage from looking at the sun, it's still an incredibly bad idea IMHO. (Note that the reason looking at the sun is not usually dangerous is not because it isn't bright enough to cause damage, it most definitely is, but because your pupils constrict in the bright daylight so don't allow enough light in to cause permanent damage. Also bear in mind that your unlikely to know your eyes are being damaged until it's way too late.) As for burning magnesium, I don't know that much but our own article Magnesium says it's dangerous. My guess is that it can be dangerous particularly if you are close to it, it's a significant amount and lasts a long time. From what I can recall when I was in school, this tended to be a short experiment (under 10 seconds), was usually done by the teahcer (i.e. you were probably resonably far away) and wasn't a great quantity (=smallish flame) likely greatly reducing the risk of harm. I don't see the fact that it's 1/29 as bright as the sun if true as significant as I mentioned already the sun is already way bright enough to damage your eyes. Also from what I can tell the amount of UV light is important too. Nil Einne (talk) 13:29, 22 July 2008 (UTC)

Wow, lots of replies! Thanks guys. Nothing like a six year old's question to get the smart folks thinking. There's a couple of really good suggestions here. The 'cast a shadow' thing sounds like a good one to try, at least to explore the topic (which is probably more important than the answer, even there even is one). The one problem is that I'm not sure it's actually correct. Lots of things can cast opposing shadows on a clear day, even regular flashlights. Maybe I should ignore my own restriction above and try explaining the difference between apparent and absolute magnitude, etc. Less viscerally satisfying, but still good to know. And as for the questions above, she's already aware of her mortality and we've already stayed up a few nights having very impromptu discussions about it. We haven't talked about nuclear war, but she knows about soldiers and war, etc. at least in general, historical sort of sense (Remembrance Day and all). We haven't had an in-depth sex talk yet, but she knows mom and dad somehow put her together inside mom ;-). I try to answer questions on the level they're asked, but I've always felt that if she wants to know, it's my duty to inform her, even if its unpleasant or uncomfortable. Matt Deres (talk) 10:55, 22 July 2008 (UTC)

Going the other way, you can use the shadow trick to show that an incandescent light bulb is less bright than the sun. On a clear day, you can see the shadow of the filament of a (clear) incandescent light bulb even when the bulb is lit. (But a laser still has higher intensity than unfocused sunlght.) Your daughter is already aware that focused sunlight is more intense ("brighter") than unfocused sunlight. -Arch dude (talk) 13:07, 22 July 2008 (UTC)

I have no source for this, but I'd suggest the experience of a strobe light in the dark being the brightest light you could let your daughter safely experience. The contrast from low light to intense flash can be blinding: let her eyes adjust to the dark and give a sudden strobe flash, see what happens. The brightest man made light I can think of (short of a nuke) is the arc on a plasma torch, which can cause severe damage to the retina. --Shaggorama (talk) 14:31, 22 July 2008 (UTC)

Hi. As an aside question, how bright would say, the Hiroshima bomb be in apparent magnitude from say 10km? Thanks. ~AH1^(TCU) 18:34, 22 July 2008 (UTC)

Far too bright. The Trinity test was described as "lighting up the sky like the sun" from a distance of 150 miles. --Carnildo (talk) 21:26, 22 July 2008 (UTC)

Still, you'd probably be close enough to test for yourself whether you really *can* see the bone structure of your hands through your flesh in the light of the flash. In the seconds before your eyes stopped working permanently. --Kurt Shaped Box (talk) 21:32, 22 July 2008 (UTC)

So, how did a butterfly end up being named 'Common Gull'?

Cepora nerissa, FWIW. What's the deal with that, huh? --Kurt Shaped Box (talk) 02:28, 22 July 2008 (UTC)

Quite a few of the butterflies in the genus Cepora seem to include "gull" as part of their common name. [3] I bet the word "Gull" is being used in another sense, perhaps an obsolete definition, place name, or proper name. I tried looking up "cepora" and "nerissa" in latin and greek but came up blank. I thought of the word "Gules" used in heraldry for red but the butterflies of the genus seem to be mostly yellow or white. That still doesn't exclude the possibility of "Gull" being a corruption from another language. I'll think about it some more... 71.77.4.75 (talk) 02:56, 22 July 2008 (UTC)

I got a potential origin idea. From what I can make of using online translators, the word "gul" in Hindi either is or is the first syllable of the word for rose or flower (gulAba?). Someone fluent in Hindi please check me on this. These butterflies seem to be common in India so the connection between the Indian word for flower/rose and the butterfly makes a bit of sense. 71.77.4.75 (talk) 03:08, 22 July 2008 (UTC)

You might have more luck on the language desk, but among the several meanings of gull in the OED is an obsolete adjective meaning "yellow, pale", from the Old Norse (gul-r), Swedish and Danish (gul).--Shantavira|^{feed me} 06:33, 22 July 2008 (UTC)

Do We Reduced Brain Power (Energy Save Mode like a laptop)

When I was struggling to get to sleep last night a thought occured to me. My laptop has 'energy save' mode - and in order to maximise battery-life it does a variety of things, one of which is 'turn-off' some of the processing power (perhaps by only using one of the 'cores') - this prolongs battery-life and allows functioning it a less energy intensive rate. My question is this...Does the human-brain do this ever? Given a time of low-food intake would the brain start 'shutting down' non-essential processing so as to reduce energy use. Would your IQ drop if sufficiently starved of energy (not to the point of no energy of course)? And does the act of thinking consume much more energy than not thinking? E.g. If I sit trying to work out a complicated calculation in my head does it consume more energy than just sitting idly doing nothing? Sorry if this is a daft question but I was struggling to sleep and it then (of course) consumed my thoughts for a while. The thing i'm thinking is they say hunger affects concentration - is this because the brain is working in 'best battery performance' rather than 'best performance' mode (to use my laptop's setting selections)? 194.221.133.226 (talk) 08:07, 22 July 2008 (UTC)

Not knowing exactly how much calories is used by the brain I recall there is no Save Mode for brain activity---it's just that your consciousness varies. We know now better than the Hubbard propaganda that suggested the amount of activity coincides with consciousness or even IQ. Also, the brain gets always the most blood, i.e., when your brain starves the other organs were already starving for some time. Of course I'm simplifying with this but that's the picture. --Ayacop (talk) 09:15, 22 July 2008 (UTC)

Everything you said was correct. The brain does conserve energy during times of starvation (which can include diets), it does use a substantial part of the energy your body uses, and it does use more during mentally challenging activities (like spelling, in my case). StuRat (talk) 13:49, 22 July 2008 (UTC)

Also note that the "nonessential functions" the brain shuts down are sometimes essential after all, such as when operating a vehicle or heavy machinery, where "brain fog" can be fatal. StuRat (talk) 13:53, 22 July 2008 (UTC)

See also Hypoglycemia#Neuroglycopenic_manifestations. --Mark PEA (talk) 14:06, 22 July 2008 (UTC)

I've seen a ref (can't find it now) to the effect that intense mental activity actually increases the carbs burned by the body. I wonder if thermal imaging would show the brain running hotter when doing complicated calculations or memorization, recall, puzzle solving, and such pursuits, compared to just sitting and not thinking about much in particular or in light sleep? Edison (talk) 23:57, 22 July 2008 (UTC)

Not thermal imaging, no, because blood quickly removes the excess heat generated. However, there is a process where radioactive glucose is given to the patient and the more radioactive portions of the brain show where increased brain activity uses more glucose. (I don't think I'll be personally volunteering to have my brain irradiated, however.) StuRat (talk) 07:05, 23 July 2008 (UTC)

When performing a task, more calories are used by people who are less trained or have lower IQs, implying conscious thinking consumes energy. [4] As for energy save mode, metabolism is reduced during starvation, according to this extremely detailed study. --Bowlhover (talk) 08:31, 24 July 2008 (UTC)

I'd conclude from that that learning is what uses the most energy, specifically forming new neural pathways. The "experts" already know how to perform the task, so don't learn anything new by doing so. Those with lower IQ's may learn it, but soon forget and must therefore relearn each time. StuRat (talk) 13:37, 24 July 2008 (UTC)

Doesn't follow. Consider the opposite scenario where pathbuilding cost is much lower than the cost to travel even one 'hop' or a section of path, but costs nonzero time. It need not be that the pathbuilding is expensive: just that the routes *before the direct paths exist* involve more hops, and so are inefficient. DewiMorgan (talk) 16:56, 26 July 2008 (UTC)

Boiling Water at a different tempreture to its boiling point.

Is it possible to boil water at a tempreture of 60 degrees Celcius and if so,why?137.158.152.207 (talk) 08:43, 22 July 2008 (UTC) kirsty

Since I assume this is a homework question, read your textbook or handouts, and if necessary, Boiling_point#Saturation temperature and pressure. If you still don't understand, feel free to ask again and we'll explain. --Bowlhover (talk) 08:55, 22 July 2008 (UTC)

A look at phase diagrams may also be of interest. — Lomn 13:11, 22 July 2008 (UTC)

You can even boil water at room temp by putting it in a sealed syringe and pulling back on the plunger to lower the pressure. StuRat (talk) 13:44, 22 July 2008 (UTC)

I've never seen this demonstration, but I just found this video. It's pretty cool. [5] —Preceding unsigned comment added by APL (talk • contribs) 16:54, 22 July 2008 (UTC)

Is it definitely boiling, as opposed to just having air forced through it (from around the plunger, into the syringe)? --Allen (talk) 17:08, 22 July 2008 (UTC)

Never mind; apparently this works when the syringe is pointed down as well [6]. --Allen (talk) 17:19, 22 July 2008 (UTC)

Also look at how much gas volume is present when the plunger is pushed back in compared to how much gas bubbled when it was pulled back. DMacks (talk) 18:24, 22 July 2008 (UTC)

Good point. So why doesn't the water bubble due to air being forced through it? --Allen (talk) 03:37, 23 July 2008 (UTC)

Er? My observation suggests that air isn't being forced through it (i.e., it's actually boiling). DMacks (talk) 03:54, 23 July 2008 (UTC)

I'm just figuring that a good deal of air has to be getting around the syringe; otherwise they'd be creating a near-perfect vacuum in there, which I'd think one wouldn't be able to pull against so easily. --Allen (talk) 11:49, 23 July 2008 (UTC)

Normal air pressure is around 15 PSI, which would mean only 15 pounds to pull a one inch cross-sectional area syringe (a huge syringe) against a pure vacuum. StuRat (talk) 15:13, 23 July 2008 (UTC)

When the syringe barrel is pushed up, look at how much/little gas space there is: that's exactly how much air has leaked in during the experiment. Note that you cannot (even with a high-vacuum pump) get anything close to a "perfect" vacuum here. You will always have the vapor pressure of the water: as you try to reduce the pressure below the vapor pressure of water, the water vaporizes to keep the pressure at that point. That's exactly what boiling is:) DMacks (talk) 12:51, 23 July 2008 (UTC)

Good points again, both of you. Thanks. --Allen (talk) 15:39, 23 July 2008 (UTC)

You can apply a vacuum pump to a properly constructed container with room temperature water in it and the water boils when the pressure gets low enough. You can even make ice this way. But the oil will need to be changed afterwards. In the 1960's a man testing a prototype American space suit was exposed to near-vacuum in a vacuum chamber when an air hose came loose, and he said the last thing he remembered before blacking out was the strange sensation of the saliva on his tongue boiling. He survived when the chamber was quickly repressurized.(edited to re-add the text the browser windo ate. It oftern happens that I insert text, everything looks fine in the edit window, then when I hit save some of it disappears). Edison (talk) 20:29, 22 July 2008 (UTC)

Edison, your edit seems to be missing some text but I know what your talking about, it can be found in the articleHuman_adaptation_to_space#Unprotected effects. Jdrewitt (talk) 21:50, 22 July 2008 (UTC)

Yes, the article you cited describes the incident. I recently saw a documentary on TV which had the original film or video and audio of the incident. Edison (talk) 23:55, 22 July 2008 (UTC)

We got to see a demonstration of this in my chemistry class. He put a bell jar over a beaker of water and pumped out the air, and the water boiled. It wasn't as cool as the burning methane bubbles, but it was pretty cool. Black Carrot (talk) 05:34, 24 July 2008 (UTC)

Named storm in Atlantic crossing over into Pacific

I am wondering if (a) has the following happened, and (b) if so, how the storm naming has been handled.

Presume a named Tropical Storm or Hurricane has formed in the Atlantic Ocean and is either large enough in either strength or size to cross over the relatively small land mass of Central America and either stay a TS or re-form back into a TS once in the waters of the Pacific Ocean -- would it be given a new name? Thanks. --Jordan 1972 (talk) 18:11, 22 July 2008 (UTC)

Hi. Yes, it has happened. See List of Atlantic hurricanes#Atlantic-Eastern Pacific crossover storms. Sometimes they lose their old name if the old system dissapated, as with Hurricane Dean or Tropical Storm Arthur (2008), but sometimes hyphenation is the answer, for example Hurricane Fifi-Orlene. Thanks. ~AH1^(TCU) 18:29, 22 July 2008 (UTC)

Some say that Hurricane Hattie and Tropical Storms Simone, and Inga were all the same storm that moved from the Atlantic to the Pacific and back to the Atlantic. [7] In 1961 they didn't have the fancy sateliite images that we would like to confirm it, but it is possible. Our article on Hurricane Hattie-Simone is rather confused about the issue, and there don't seem to be any reliable sources confirming that the storm maintained its circulation. The WP:WikiProject Tropical cyclones is actually discussing that storm right now. Plasticup ^T/C 19:42, 24 July 2008 (UTC)

Aphasia only when alone? Or just refusing to talk to oneself?

If a person wants to say a sentence, but can't get the words out, when alone, but can when there is another person providing a stimulus, would this be aphasia, or would it just be a mental block against talking to oneself? In looking at the article on aphasia, it sounds like the disorder is mroe than just the ability to get words out, but on the other hand, intrapersonal communication implies that everyone talks to themselves - or at least has the physical capability to.

So, I guess what I'm getting at is, is aphasia only consistent speechlessness? Or, does there have to be more of a general language problem? Is it possible for a person to develop such a persistent mental block agsinst talking to oneself that they can't speak unless someone else is int he room? (It's just nice to know that it is normal to talk to myself :-) 209.244.187.155 (talk) 18:34, 22 July 2008 (UTC)

According to the article, aphasia is caused by brain damage, so it likely to be consistent. There are other conditions which may be relevant - for example there are children that will only talk to close family and friends and will go completely silent in public. I don't know what that's called, though. What you describe seems to be the opposite of that. --Tango (talk) 20:23, 22 July 2008 (UTC)

Reply to Tango: Selective mutism. --Mark PEA (talk) 23:07, 22 July 2008 (UTC)

Sorry, but we cannot speculate about medical diagnoses here at the Reference Desk, per the guidelines posted at the top of the page. You might wish to discuss this with your physician. Edison (talk) 20:25, 22 July 2008 (UTC)

Find me Alexander Selkirk's physician and I'll ask him. :-) I had read where this real life castaway, who inspired somewhat the story of Robinson Crusoe, had mostly lost the ability to speak after being stranded for 4 years with no human companionship, and wondered if this would have been possible because he simply didn't exercise that while alone. That's where this question came from.

Although, ironically, I found the man's name in the Crusoe article, and read that a fall from a cliff is mentioned (fromt he talk section), which implies if he did lose it, it may have been because of a physical injury after all, and not because of some inhibition agains ttalking to himself that had grown into an inhibition agaisnt speaking, period, unless in the presence of others.

I thought my query would be a little less convoluted without throwing the stuff about Selkirk in there, and Crusoe - especially since I mention I can talk to myself so don't have this problem - but I guess not. And who knows, maybe what I read about Selkirk having lost the ability to speak was wrong, anyway.

Though, now that I look at your answer, Edison, you probably *did* understand it wasn't my problem and that I can talk to myselrf (and do). And, I can understand, perhaps it is best you don't speculate on anyone's medical condition. I imagine the condition of someone 300 years ago would lead to a much higher degree of speculation than you'd ever want to do Wikipedia, even without the legal ramifications. :-)

(And, I should add, now looking at the article on Selkirk that is cited, what I'd heard about his losing his ability to talk may have been quite incorrect anyway.)209.244.30.221 (talk) 21:18, 22 July 2008 (UTC)

Rodent identification

I'm trying to figure out what rodent I just saw in our garage. It was likely a chipmunk, but it looked too large to be so (though the light was off, so it's difficult to tell). Does anyone know how I can find out what rodent species are native to Manitoba? 24.76.161.28 (talk) 19:39, 22 July 2008 (UTC)

http://canadianbiodiversity.mcgill.ca/english/species/mammals/rodentia.htm is a list of rodents found in Canada. Note that clicking on the name of a species usually gives you its distribution map. --Bowlhover (talk) 20:36, 22 July 2008 (UTC)

Heat and tiredness

Why does hot weather and high humidity always tire me out and make me irratable? —Preceding unsigned comment added by 79.76.157.37 (talk) 23:34, 22 July 2008 (UTC)

See Humidity#Effects on human body. PrimeHunter (talk) 23:46, 22 July 2008 (UTC)

I believe this is a protective mechanism. Your body detects that it's overheating, and lowers your metabolic rate to limit heat production to fight this. Lowering your metabolic rate will result in you being sluggish and tired. StuRat (talk) 06:52, 23 July 2008 (UTC)

Shouldn't it rather sweat than make tired? --Ayacop (talk) 16:14, 23 July 2008 (UTC)

Hi. No, that doesn't work when it's humid, as shown by the above link. Sweating usually cools you down by evaporating, but when it's that humid, the sweat can't eveporate, so it just sits there, making you feel hotter. Hope this helps. Thanks. ~AH1^(TCU) 16:34, 23 July 2008 (UTC)

You'll also sweat. Our bodies have multiple cooling methods. In an "emergency situation", it will use every mechanism at it's disposal to cool you down quickly. StuRat (talk) 01:26, 24 July 2008 (UTC)