The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
We will not do your homework here. Try searching for the answers yourself by typing a key word or phrase (hint: "antibiotics") in the search box near the top left of this page. -- Tcncv (talk) 03:58, 29 October 2008 (UTC)[reply]
Please do not post in ALL CAPS because it is the equivalent of shouting. See the article Antibiotics which discusses side effects and misuses. For "who discovered antibiotics and how" see the History section of Antibiotics as well as Timeline of antibiotics and read about the various antibiotics, who discovered them , how, and when. Questions of "who discovered" something are often subjects of debate. There are many tentative and ultimately abandoned experiments before someone gets it right and comes up with a practical product. Edison (talk) 05:24, 29 October 2008 (UTC)[reply]
Well it was asked on another desk - and I suppose you could say it was answered (there were replies to the question) - but we didn't come up with any satisfactory (yet alone 'compehensive') answer...which is a shame - because I'd quite like to know too. However, I doubt there are many people who respond on the Science desk who don't also patrol the miscellaneous desk - so I doubt we'll get any further here. SteveBaker (talk) 17:23, 29 October 2008 (UTC)[reply]
I for one do not stalk the misc desk. Just because you seem to think you know everything, doesn't mean you can make such generalisations. With regards to the answer, Dmcq's answer actually sounds quite reasonable. Jdrewitt (talk) 07:52, 31 October 2008 (UTC)[reply]
The only reference I can really find that could back up Dmcq's answer is a manual of engineering written by Professor Thomas E. French of the Ohio State University in 1911, the full text of which is available here in which he describes how to use the French curve. I can't find any concrete evidence that they are named after him though. Jdrewitt (talk) 18:29, 1 November 2008 (UTC)[reply]
Posting this here because it's the closest RD topic to engineering...
The bridge pictured to the side was badly damaged in flooding this summer, as is obvious; but how properly should the bridge be described? Destroyed, because obviously it can't be used? Or damaged, because 2/3 of the bridge is still there? I'm loth to use "destroyed" because most of it is there; "damaged", because that's not specific enough (after all, minor vandalism to a bridge can legitimately make it "damaged"); "washed out", because (at least to me) that conveys less than this bridge has sustained; and "irreperably damaged" because (aside from the fact that I probably spelled it wrongly) I suppose the state could come along and fix it back up again, so such a pronouncement would be crystalballish and perhaps OR-ish. What's the most accurate term of these, or is there a better? Nyttend (talk) 14:09, 29 October 2008 (UTC)[reply]
If you want to be more descriptive or specific then you'll need to think about phrases like "damaged by having one of three spans destroyed". Incidentally, I think you really needed the language desk because your problem is not one of engineering but of words - but hey, who's worrying. 86.4.187.55 (talk) 14:35, 29 October 2008 (UTC)[reply]
To say that the remaining 2/3s are "functional" is not necessarily accurate either. Any structure that has had a partial collapse may have other non-visible structural problems elsewhere. I would not assume that the standing pieces are "undamaged", they are just "less damaged" than the collapsed span. Nimur (talk) 17:05, 29 October 2008 (UTC)[reply]
Truly - this is neither a science nor an engineering question - it's linguistic - and it belongs on the language desk. I suppose - if forced to describe it - I'd say that one span was destroyed and the other two appear intact. "Damaged" works for me too - and since we didn't say how damaged, there is indeed considerable ambiguity between a small scratch on the commemorative plaque at one end of the scale - and just a small amount of the bridge remaining at the other. So "heavily damaged" might be a better choice. I suppose we really need a word like "incapacitated" ... "non-functional" maybe? But it's not science - nor yet engineering.
To quote (my hero)Richard Feynman who is talking about a walk through the park with his father when he was just a little kid:
" `See that bird?’ he says. ‘It’s a Spencer’s warbler. (I knew he didn’t know the real name.) ‘Well, in Italian, it’s a Chutto Lapittida. In Portuguese, it’s a Bom da Peida. In Chinese it’s a Chung-long-tah, and in Japanese it’s a Katano Takeda. You can know the name of that bird in all the languages of the world, but when you’re finished, you’ll know absolutely nothing whatever about the bird. You’ll only know about humans in different places, and what they call the bird. So let’s look at the bird and see what it’s doing - that’s what counts!' "
So - who cares whether the bridge is "damaged" or "destroyed"? That tells you nothing about the state of the bridge - but only how humans perceive it to be. The real issue - is how much will it cost to repair - and do we want to do that? SteveBaker (talk) 17:20, 29 October 2008 (UTC)[reply]
The reason I ask is that it's notable (on the National Register of Historic Places) and I think I'm going to write an article on it soon; and I was guessing that there might be some sort of specific term used to describe it for use in the article. The article will include this photo, so I'll not need just words. Nyttend (talk) 20:34, 29 October 2008 (UTC)[reply]
One of the more common ways of differentiating between "damaged" and "destroyed" is "Is it cheaper to repair it, or to tear it down and build a replacement?" If it's cheaper to repair, it's been damaged. If it's cheaper to replace, it's been destroyed. --Carnildo (talk) 23:35, 29 October 2008 (UTC)[reply]
But that dichotomy is rooted in the originally designed/intended function, not the thing itself. "The thing" is only damaged, not destroyed, until it's completely reduced to rubble. Rendered unusable as intended and unable to be repaired to such a state ≠ demolished. DMacks (talk) 01:34, 30 October 2008 (UTC)[reply]
Technically - I suppose - general relativity is SLIGHTLY involved - but that's a really silly, misleading and quite utterly useless answer.
For all practical purposes, the answer is "No". Straightforward gravity - per Sir Isaac Newton - suffice to explain the tides without mentioning general relativity. Science has known how tides work perfectly well - and has been able to calculate their properties for a hundred years before Einstein.
The gravity of the moon decreases with the square of the distance from it. Hence, the gravity on the side of the earth nearest the moon is slightly greater than over the rest of the planet - so water is pulled harder towards the moon on that side. It's actually a bit more complicated than that because there are actually TWO high tides - one on the side nearest the moon - and another on the side furthest from it. This is because the earth-moon system rotate around a common center of gravity that's not at the center of the earth - but a bit closer to the moon. If you imagine this pair of large objects spinning around a point somewhere between their centers - than you'll see that the part of the earth that's furthest from the moon is subject to some centrifugal force (yes, I know there is no such thing as centrifugal force - it's a handy shorthand and I have no compunctions in using the term in casual explanations). That centrifugal force throws the water on the side OPPOSITE to the moon outwards - hence there are TWO tidal bulges - one that is strongest when the moon is overhead - and the other that's strongest when the moon is directly below your feet. The daily rotation of the earth places the moon overhead and beneath the ground roughly twice per day - so the high tides are roughly 12 hours apart. In fact - because the entire earth-moon system rotates around it's center once a month, that means that there is actually one extra pair of tides every lunar month - so the interval isn't quite 12 hours. To throw some more complexity into the mix - the sun's gravity also produces tides - although not so strongly as the moon. So you get smaller solar tides added to the lunar ones. The combination of the two means that the strongest tides are when the sun and moon are close together in the sky at midday - or close together underground at midnight.
None of that explanation requires reference to general relativity - but doubtless there are TINY, MINISCULE effects due to relativity - which would be much too small to measure against the other properties of the ocean that can cause the tidal changes to be either more or less than you'd expect (eg the shape of the coastline - or the slight changes in the temperature of the water between summer and winter).
Hence the best answer to your question is a resounding "No" - although some pedants might like to say otherwise. To the pedants...please don't let pedantry get in the way of a clear and useful answer to a simple question.
Actually, the question was "Does the theory of general relativity explain ocean tides?" not "Is Newtonian physics good enough to explain ocean tides.". Anyway, it's all good. :) 12.10.248.51 (talk) 20:18, 29 October 2008 (UTC)[reply]
I don't understand your centrifugal-force explanation of the tide on the far side, and I think it's incorrect. The tide on the far side happens for the same reason as the tide on the near side: because things nearer the Moon are pulled more strongly. The water nearest the Moon gets pulled more than the Earth, so it separates slightly from the Earth; the water farthest from the Moon gets pulled less than the Earth, so it separates slightly from the Earth.
I'd never argue that general relativity is needed to explain the tides, but I might argue that the "philosophical framework" of general relativity is better for understanding the tides. In general relativity the gross acceleration of gravity is fictitious, just like the centrifugal force. When you're weightless, you're weightless; a gravitational acceleration you can't feel doesn't exist. The real gravitational field, i.e. what's left when you subtract out the fictitious part, turns out to be exactly the tidal force. (Not quite true, but close enough. I don't want to be pedantic...) The tidal force tries to "spaghettify" you, by stretching you parallel to the direction of the gravitating body and squeezing you in the perpendicular directions. So in general relativity it's very simple: the Earth is in freefall, and there's a tidal-force contribution from the Moon and another from the Sun. They both spaghettify the water, which is why they cause two high tides on opposite sides of the Earth and a ring of low tides in between. (Or would, anyway, if not for all the confounding factors mentioned in the tide article.) -- BenRG (talk) 23:36, 29 October 2008 (UTC)[reply]
The viscosity of sea water affects tides. It slows down the flow of sea water into the high tide regions on both sides of the earth. This makes high tides lower and low tides higher. Also, land masses deflect tidal current, causing variations in tidal height and timing. See "Tide" in Wikipedia.
Glassmaking kiln explosions?
Hi - I'm writing a scene where I need a disastrous explosion of a kiln in a sixteenth century glassmaking workshop - was such a thing possible? - if so, how?
The glassmakers of Wimpole Street were the best in the business - they've been commissioned to make an enormous glass snowglobe for a rich nobleman - it's a wedding present for his new wife who comes from Sweden and misses the snow terribly. It's 3 gallons of water enclosed in a two foot sphere of inch-thick glass - soon to be engraved with the nobleman's vows to his new wife (just as soon as they get that Swedish translator in). It's held in an delicate, ornately carved wooden frame that's perfectly weighted so the enormous globe is easy to turn over to make the snow fall. The glass blowers have been struggling to make it for months - there have been many attempts and many failures. It's the hardest thing they've ever had to produce. But finally they have something so perfectly round and amazingly clear that nobody has seen the likes of it before. They fill it up with water and fake snow (maybe some kind of wax-based concoction) and their top glass-guy is melting a small disk of glass into the very top to invisibly block the hole that they used to fill it through. His apprentice looks on at the most impressive object they've ever made - realising that he'll never again be in the presence of something so beautiful - despite it's deceptive simplicity. The glass plug is in place and is cooling off nicely when the klutzy apprentice rests his hand atop the globe. It's still pretty hot and he recoils in pain...trips and falls against the ornately carved (but flimsy) wooden frame. The frame snaps and the globe rolls slowly and ponderously towards the furnace while everyone looks on in horror - they don't have time to make another before the wedding day. They are all frozen to the spot as the globe wobbles on the edge of the kiln...then falls in. It doesn't break - the glass is too thick. But it's too hot inside the kiln and the globe is FAR too heavy to lift out with the tools they have. Try as they may, they can't get it back out again. The glass on the outside won't get hot enough to melt because the water inside is absorbing the heat and keeping it under 100 degC...until the water boils...then KABOOOOOOM!!!!! Glass, fake snow, steam and white-hot coals from the kiln go everywhere - most of the building is levelled by the explosion. The only person to survive (inevitably) is the klutzy apprentice who "learns a valuable lesson".
The big problem with that is that snowglobes weren't invented until the 1800's sometime...so no good for you. But maybe you can come up with something similar? SteveBaker (talk) 20:29, 29 October 2008 (UTC)[reply]
The glass makers may have used Sulphur (or brimstone) as pigmentation in the glass. To form a glass you need to rapidly quench a melt. So the Sulphur will need to be heated to above its melting point. Since Sulphur burns easily in air, it will have to be sealed in a container with the other glass constituents to prevent exposure to air. The vapour pressure of Sulphur is very high and so it is quite likely the container would explode! Since molten Sulphur is extremely flammable there will be quite an explosion and resulting fire. Jdrewitt (talk) 21:39, 29 October 2008 (UTC)[reply]
But sulphur boils at 444 degC - but glass doesn't melt until 1500 degC. How are you going to get even liquid sulphur into the liquid glass if it boils before you can get it in there? As our article Glass_production#Colors says - the Sulphur is added in the form of "iron polysulphides". It can't just be pure sulphur...no way! iron sulphides melt at temperatures similar to the glass - so they aren't going to do anything exciting in the kiln. SteveBaker (talk) 03:06, 30 October 2008 (UTC)[reply]
Sorry but you are incorrect. I have made plenty of chalcogenide glasses using pure elemental sulphur. I have also had a few ampoules explode! The fact that Sulphur boils at 444 degC is irrelevant, since once it has been melted it will react with the other glass constituents. These don't necessarily have to be in the liquid-state. Also, you mention "glass" melts at 1500 degC. This is a complete fallacy. It depends what glass composition you are talking about! Many glasses have melting temperatures much much lower than the temperature you are talking about. Jdrewitt (talk) 13:39, 30 October 2008 (UTC)[reply]
Just to clarify, the glass constituents, including elemental Sulphur are sealed in a container and heated, this could be done through a series of furnaces at different temperatures so to gradually raise the temperature. However, since the vapour pressure of Sulphur is very high, the pressure is too much and the container explodes, exposing the molten Sulphur to air, and any the other constituents. The Sulphur immediately ignites and destroys the glass workshop. Jdrewitt (talk) 08:02, 31 October 2008 (UTC)[reply]
Oh man, I'm already picking apart Steve's sphere explosion theory on his talk page. Do I have to go after this one too? Sigh. What size pressure vessel and how much elemental sulphur are they using? What other components are in the sealed vessel? When will people learn the simple answer - snow-globe technology was developed by the Picts and suppressed by the Knights Templar until Charles Dickens rediscovered it when he found The Pickwick Papers in a Welsh barrow. Franamax (talk) 09:23, 31 October 2008 (UTC)[reply]
Sorry but I'm not sure whether you're being flippant or serious. Which part of the theory do you disagree with. I don't expect you would need too much elemental sulphur to produce some nice colours. But it would need to be heated in a vessel since otherwise it would just react with the air. Other glass constituents? Well that depends what they are making but lets just go for a silica based glass but this is really not very important since its the vapour pressure of sulphur which will produce the explosion. I have made some sulphide glasses up to 3 g sealed in ampoules. If these are heated too quickly, the vapour pressure of the sulphur causes the ampoules to explode, violently. I have witnessed this and was glad I had appropriate shielding in place. Scaling this to an industrial scale and can easily envisage a large scale explosion. Jdrewitt (talk) 10:15, 31 October 2008 (UTC)[reply]
I'm being both flippant and serious, as usual. We're talking 160 lb. or so of glass, so it's going to be a lot of sulphur anyway. This glass needs to be extracted as a melt though, and shaped into a globe, right? - so it has to be an openable container at the very least. But why would you use a sealed container anyway - unless you knew you had to contain vapour pressure during the melt process, in which case you would use a freakin' big cast iron lid, because you already knew what happened when you did it with 3g of sulphur? Questions along that line is where I would start, then I would look at the vapour containment efficiency of the openable container to estimate at what point it would start venting gas. Then I'd go back to what you already said about how as the sulphur vapourized, it would begin reacting with the other solid components, and I would wonder about why the Renaissance glassmakers would be trying to use elemental sulphur instead of compounds with a better melt compatibility. I don't doubt what you're saying about vapour pressure of heated sulphur though, nor its reactivity - just trying to figure out how the glassmakers got killed. Franamax (talk) 10:35, 31 October 2008 (UTC)[reply]
Where does it say the glass makers are trying to make a globe? That was just SteveBaker's suggestion - which by the way I'm not very impressed with (but I think my impression is tainted by the fact that he told everyone that you can't make glass using elemental sulphur when you/I clearly can!) But anyway, I was thinking along the lines that they just want to make some coloured glass for some reason - any reason, the OP didn't specify. So they would heat up the consituents in their container to the melting point of Sulphur. When I speak of vapour pressure, I mean at its melting point. Sulphur has a very high vapour pressure at its melting point, see the article on Vapor_pressure to see what I mean. I'll try and find an article that actually states the vapour pressure of Sulphur. So anyway, the majority of Sulphur is still molten and will react with the other constituents while still molten. The reason I thought they might use elemental Sulphur is purely because I think it would be readily available. Jdrewitt (talk) 10:53, 31 October 2008 (UTC)[reply]
Oh yes, and the reason you need to contain the glass constituents is to prevent the sulphur reacting with the air. It would just burn if left in the open. Jdrewitt (talk) 11:05, 31 October 2008 (UTC)[reply]
(e/c) You're indented under the snow-globe, so I thought it was the same story :) There's still the issue of the need for an openable container, if they wanted to shape the glass - so what is the failure mode of the container? Now using elemental sulphur is a possibility, but wouldn't they then throw the sulphur into the melt at full temp? Some (or most) would burn off, but the molten part could be mixed in. Or heat the sulphur to molten in a container that could off-gas, then add the molten sulphur to the melt? But to get a uniform mix in the melt, seems to me it would be more practical to use a compound with a higher melt point, so as to be more compatible with the process. These are practical people after all. I'll go with your story, you just need to flesh it out a bit :) Personally, I think the easiest way to go is that rain built up on the roof, which collapsed and dumped cold water into the kiln - if we're talking 1500 C, that should make a nice mess. Franamax (talk) 11:24, 31 October 2008 (UTC)[reply]
And wouldn't you heap the other components on top of the sulphur to prevent it being exposed to air? And maybe heap some lime on top, or ash, or whatever will segregate from the melt, either top or bottom, to prevent air exposure during the melting process? Franamax (talk) 11:24, 31 October 2008 (UTC)[reply]
Many of your points are valid but I really don't care enough to make any further comment :) It's not my story after all, I agree it needs fleshing out but the OP can do that themself! I have provided a possible cause of an explosion in a glass making workshop and am not saying its the best explanation but it is possible nonetheless. Your water explanation would indeed be disastrous also. Jdrewitt (talk) 13:15, 31 October 2008 (UTC) P.S. I have adjusted the indentation of these posts.[reply]
Well, we've killed these people three different ways now, I guess that's enough - and the OP is happy. Another RefDesk question successfully beaten unto death! :) Franamax (talk) 13:37, 31 October 2008 (UTC)[reply]
See "Shattered" by Dick Francis [3] for a hint about what unannealed glass can do. An explosion involves potential energy suddenly released. Edison (talk) 04:31, 30 October 2008 (UTC)[reply]
I agree annealed glass can be very dangerous, but the OP is asking for an accident inside the kiln, which will be before the glass has been made. Maybe there is a chance that something could go wrong in the annealing kiln though, maybe if it is heated too quickly or something? Jdrewitt (talk) 10:21, 31 October 2008 (UTC)[reply]
Wouldn't a glassmaking workshop have a large supply of coal on hand? Perhaps they get careless with it, and somehow their coal store fills with explosive coal dust? This seems like rather a stretch. APL (talk) 05:14, 30 October 2008 (UTC)[reply]
Not sure about exploding, but you might be interested to know that in 1291 the city of Venice forced their famous glassmakers to move their workshops to the island of Murano because they feared the dangers of fire in their mostly wooden city.
All great stuff - I'm extremely grateful for the detail everyone - Steve Baker's story's fantastic - I might try a variation on that - not a snowglobe, but another waterfilled glass sphere - I love the sulphur and rain ideas too - will keep them for future use - thanks, all Adambrowne666 (talk) 11:39, 31 October 2008 (UTC)[reply]
If you're seriously going to go with it - you should probably take a spin over to my talk: page where User:Franamax and I were engaging in some side-discussions on the subject. It's certain that I didn't do any kind of math (bad, bad, bad!) in proposing the idea - and I got a lot wrong that Franamax can help to correct. A two foot sphere would contain around 20 gallons of water - not three - so we might want to go with a smaller sphere in order to give it a chance to explode before they can put out the fire in the kiln. Franamax has some convincing math that shows the kinds of pressure it would take to rupture a 1" thick sphere - and in retrospect, that may be WAY too thick. But I'm convinced that some variation on the numbers would correctly produce the kind of situation you need...at least to the degree necessary to convince 99% of the readers of your work! The business of snow globes not being invented for another 200 years is actually a nice thing you could weave into the story. These guys invented the snow globe - but the explosion resulting from the disaster kills all but the young apprentice - so the idea for making such things (along with the not-inconsiderable technology needed to make one this big) would have been lost in the explosion...not to be re-invented for another 200 years. So it's at least a consistent story - if not historically accurate. SteveBaker (talk) 18:45, 31 October 2008 (UTC)[reply]
Maximum visual acuity
In conventional optometry you increase visual acuity by correcting the curvature of the cornea, or by using glasses to bend the light in a similar manner. The upper limit on the visual acuity provided by these methods seems to be the exactness of the lens and the precision of the prescription, but I am wondering whether there is an upper-bound imposed by the density of receptors on the retina. Ignoring changes in the shape of the eye and assuming a perfect lens, what is the limit of human visual acuity? PlasticupT/C22:21, 29 October 2008 (UTC)[reply]
We have around 120 million 'rod' cells (and a lot fewer cones) so we can resolve brightness (but not color) at roughly 11,000 x 11,000 pixels - that's pretty amazingly good (consider that we think a 10 megapixel camera is pretty nifty - but we have two 120 megapixel devices in our heads!) - but we can actually do even better than that. The eyeball never stays precisely still - it's always moving around a teeny-tiny bit. This means that each of those 120 million detectors is able to sweep over a small area around the point it's nominally aimed at. By noticing how the brightness changes over time as the eyeball wobbles, we can get even more precision. The precise resolution is hard to deduce since it depends on complicated aspects of how the data is compressed and encoded in the layers of cells behind the retina and down the optic nerve. However, within a roughly 50x50 degree region that we can take in with a single glance - so we can resolve better than 16 arc-seconds when the lens is good. Color resolution is not so good - 4.5 million cone cells. But they are more concentrated in the center of the retina - perhaps 2,000x2,000 pixels. A pretty standard 4 Megapixel camera can do color about as well as we can - but our huge lead in brightness precision wipes that out in terms of image sharpness. SteveBaker (talk) 02:29, 1 November 2008 (UTC)[reply]
Proving that the moon exists to doubters
Is there a simple experiment that can be carried out at home, requiring no complex/expensive scientific equipment, that can conclusively prove that the moon, our moon, is in fact a genuine, bona-fide moon (in the 'celestial body' sense) - and not a man-made construct, floating above us, at most a couple of hundred miles away? --Kurt Shaped Box (talk) 22:34, 29 October 2008 (UTC)[reply]
Proof is a mathematical concept, there is no such thing in science. All you can do is collect evidence to support or oppose a theory. You then pick the theory that is most likely given the evidence. The fact that there is documented evidence of the moon existing before we developed the technology to create anything that would look like that is pretty conclusive. If anyone truly believes that the moon isn't real then they are basing their belief on something other than reason so no reasoned argument will ever persuade them. --Tango (talk) 23:15, 29 October 2008 (UTC)[reply]
If the moon were only a couple of hundred miles above the Earth, what are the chances that it would pass over your house every night? If you ever take a vacation you will notice that the moon is visible from all over the planet, and must therefore be very far away. PlasticupT/C23:19, 29 October 2008 (UTC)[reply]
That logic only works if you assume the Earth is large and round. ;-) But yeah, the fact the moon looks the same from two widely seperated vantage points is an argument for it being a great distance away. Dragons flight (talk) 23:26, 29 October 2008 (UTC)[reply]
The fact that it can be seen simultaneously by people in different places would take care of that objection -- and incidentally also provides a proof that the Earth is not flat, because which way up you see the Moon depends on your latitude. However, this really falls outside of the category of household experiments, because it requires long-distance communications. --Anonymous, 05:52 UTC, October 30, 2008.
I was going to give the parallax answer, but Theresa beat me to it. On the other hand, you don't even need that measurement to determine that the Moon is very far from the Earth. The equipment-free solution is to go outside and look up at the Moon. Wait five minutes, and look up at the Moon again. Notice how it's in the same place relative to the background stars? Any small body in low Earth orbit would have swept across the entire sky in that time. (For comparison, the International Space Station, orbiting at an altitude of rougly 400 km, completes one orbit of the Earth about every ninety minutes. Most folks would notice pretty readily if the Moon rose and set eight times over the course of a single evening.)
For more precision, one could use a camera to take pictures of the Moon on consecutive evenings. Measuring the movement of the Moon between images against the background stars would allow you to calculate its orbital period, and from that its altitude.
That only proves that the fusion reactors and anti-grav drives on the lunar station are able to keep it moving in such a way that it looks like it is far away. Dragons flight (talk) 23:59, 29 October 2008 (UTC)[reply]
My point, which obviously escaped you, is that if someone is already engaging in fantastical thinking to disbelieve in the moon then they are likely to invoke similar nonsense to counter any proof one might offer. Dragons flight (talk) 00:07, 30 October 2008 (UTC)[reply]
Probably the easiest proof that the Moon is large and far away is that the apparent size does not change over the course of the night. If the Moon is only 500 miles up and 4.3 miles across, then (assuming the Earth is 8000 miles in diameter) the apparent size should be about five times larger when the Moon's overhead than when it's on the horizon. Incidentally, this works regardless of if the Earth is flat or round, and doesn't require that either Einstein's or Newton's law of gravity be correct. --Carnildo (talk) 23:46, 29 October 2008 (UTC)[reply]
Tides. It takes a monumental amount of force to move a bajillion tons of water 10' vertically upwards. If the moon isn't really a chunk of matter 1/6th the size of the earth - then how do the tides happen precisely in sync with that white circle up there in the sky? So - no fancy hardware. A measuring stick - a beach and someone to watch where the "moon" is in the sky when the tide is at it's highest. QED. SteveBaker (talk) 02:44, 30 October 2008 (UTC)[reply]
1/6?! It's over 1/4 of the Earth's size by diameter, and under 1/80 by mass. --Anonymous, 05:53 UTC, October 30, 2008.
If the Moon's orbiting the Earth once per month at an altitude of 500 miles, you can't assume that gravity is behaving according to Newton, so the tides aren't proof of anything. --Carnildo (talk) 08:25, 30 October 2008 (UTC)[reply]
Occam's razor doesn't tell you to ignore evidence. In this case the evidence is overwhelming. Let me cut and paste:
“
THE MOON: RIDICULOUS LIBERAL MYTH
It amazes me that so many allegedly "educated" people have fallen so quickly and so hard for a fraudulent fabrication of such laughable proportions. The very idea that a gigantic ball of rock happens to orbit our planet, showing itself in neat, four-week cycles -- with the same side facing us all the time -- is ludicrous. Furthermore, it is an insult to common sense and a damnable affront to intellectual honesty and integrity. That people actually believe it is evidence that the liberals have wrested the last vestiges of control of our public school system from decent, God-fearing Americans (as if any further evidence was needed! Daddy's Roommate? God Almighty!)
Documentaries such as Enemy of the State have accurately portrayed the elaborate, byzantine network of surveillance satellites that the liberals have sent into space to spy on law-abiding Americans. Equipped with technology developed by Handgun Control, Inc., these satellites have the ability to detect firearms from hundreds of kilometers up. That's right, neighbors .. the next time you're out in the backyard exercising your Second Amendment rights, the liberals will see it! These satellites are sensitive enough to tell the difference between a Colt .45 and a .38 Special! And when they detect you with a firearm, their computers cross-reference the address to figure out your name, and then an enormous database housed at Berkeley is updated with information about you.
Of course, this all works fine during the day, but what about at night? Even the liberals can't control the rotation of the Earth to prevent nightfall from setting in (only Joshua was able to ask for that particular favor!) That's where the "moon" comes in. Powered by nuclear reactors, the "moon" is nothing more than an enormous balloon, emitting trillions of candlepower of gun-revealing light. Piloted by key members of the liberal community, the "moon" is strategically moved across the country, pointing out those who dare to make use of their God-given rights at night!
Yes, I know this probably sounds paranoid and preposterous, but consider this. Despite what the revisionist historians tell you, there is no mention of the "moon" anywhere in literature or historical documents -- anywhere -- before 1950. That is when it was initially launched. When President Josef Kennedy, at the State of the Union address, proclaimed "We choose to go to the moon", he may as well have said "We choose to go to the weather balloon." The subsequent faking of a "moon" landing on national TV was the first step in a long history of the erosion of our constitutional rights by leftists in this country. No longer can we hide from our government when the sun goes down.
Wow - so "The moving Moon went up the sky, And no where did abide: Softly she was going up, And a star or two beside." (Samuel Taylor Coleridge, The Rime of the Ancient Mariner) must refer to the launching of the "moon" - and since it's claimed (in those Liberal "public schools") that Coleridge died 120 years before the "moon" was launched in 1950 - we have proof that the school system is covering up for "big government". Since he's also claiming that one or two of the stars were launched on the same day - we have to wonder what other things are being looked at?! But "When I consider thy heavens, the work of thy fingers, the 'moon and the stars, which thou hast ordained..." comes from Psalm 8:3-4. This means that they even rewrote bits of the Bible! Is there no depths to which they will not sink? If we can't trust the bible then maybe the Theory of Evolution is true too! Where does the rabbit hole end? SteveBaker (talk) 18:27, 31 October 2008 (UTC)[reply]
This is siad to be Venus true color is it close to white with faint yellow. If I was orbiting Jupiter will the planet look like a pearl, always playing with color. Seen from Saturn's low magnitude will Saturn still be around blueish silver if I was orbiting planet. If I was far away from the planet, it will look darker, if I was clser to planet, it looks brighter. if I was orbit one foot away from Uranus, it's methane gas will still give glows of violet color since it's magnitude is 5. For Neptune, it would be essentially dim, since the magnitude is 8, I beleive I will still see a dark indigo color when I am orbiting the planet since it have little light far away, for Pluto, and it's other dwarfs, the surface will look black, even if I stad on it--Freewayguy00:27, 30 October 2008 (UTC)[reply]
We discussed this stuff in some detail in your earlier question about Uranus's color. But what you are saying here is bogus. The 'magnitude' of an object depends on it's size as well as it's brightness. When you are up close to it - the size is irrelevant - so comparing the magnitude of these objects and using that to estimate surface brightness is pretty much meaningless. To do this right - compare the albedo divided square of the range of each of the objects from the sun. Do the comparison with the same numbers calculated for the Earth and you'll have a better idea of relative brightnesses from close to the planet. Both sets of data are available in the standardized info-boxes in the articles about each planet. SteveBaker (talk) 04:18, 30 October 2008 (UTC)[reply]
I don't think that you would see Pluto as black when you are on the surface, in the same way that the moon does not look black from earth, but a moon rock does when you have it on earth, and on the moon surface it looks bright grey. Pluto seems to be mostly an apricot colour. The light at Pluto may not be as dark as you think, instead it would be like an incandescent bulb, dim but still good enough to see colour. For Venus you are right it look white, you can see it with your own eyes. Graeme Bartlett (talk) 06:25, 30 October 2008 (UTC)[reply]
I've been to the moon-rock 'vault' at the NASA space center in Houston (it's open to visitors most days). You can see the actual moon rocks (LOTS of them!) in normal room lighting - and there is even one moon rock there that you can actually touch (although the surface of it is so covered with grease and dead human skin cells...I'm not sure you are actually getting in contact with it)! Those rocks are emphatically NOT black - they are mid-grey with very little color to them. So they match more or less what the moon looks like in the sky - with an albedo of 0.1 or so.
But here is the problem (and we talked about it before when the same OP asked about the color of Uranus): Human vision is a crappy way to measure brightness and color. We have eyes that adapt to the dark and to the very bright. So when you see Venus in a dark sky, it looks impossibly bright. But your dark-adapted eyes have shut down all of your color sensors and really wound up the "brightness" controls. So you can really only see in black and white and the fairly dim dot that is Venus is overloading the few 'pixels' in your retina because it's soaked in rhodopsin and the iris is wide open. This means that the light-sensitive cells that Venus impacts simply report "Ouch! Too bright!" and not much else. The atmosphere here on Earth is also scattering blue light due to the Raleigh and Mei scattering mechanisms...that leaches blue out of the image and further distorts any chance of getting good color information from distant objects. (Especially Venus which is only ever visible near the horizon where the atmospheric color distortions are greatest). Hence, Venus LOOKS white to the naked eye - an slightly yellowish in a telescope. When we fly a spacecraft up next to it or use the Hubble telescope - we don't have any of those annoying human visual wierdnesses - and the planet looks yellow.
So our OP asks "What color is it "really"?" - is it white or yellow?
Well, that's an utterly meaningless question. Humans can't even see yellow light properly - we don't have sensors for yellow light. We only notice it at all because it slightly stimulates our red and green sensors and we've decided to label that "red-and-green-together" sensation using the word "Yellow". However, small amounts of pure red and pure green light (such as you'd see in a photo of Venus on your computer screen) also appear "Yellow" - but for different reasons. If you stare for 30 seconds at a picture of the US (or British) flag - then look quickly over at a sheet of white paper, the paper "looks" like it has an orange and cyan flag hovering over it because our eyes have color-adapted to the strong reds and blues in the flag and take a few seconds to recover. So in orbit about Venus, our eyes would adapt to the colors and start to wash them out. So what we see and how the universe truly is are very different things - photos (either on photographic prints, or in CMYK magazine prints or RGB computer screens) have nothing like the range of colors that the planet actually has or that our eyes could potentially resolve (you simply cannot reproduce a really strong "cherry red" on a TV or computer screen for example). When NASA design a space probe - they need to capture specific data to determine chemical compositions, etc. So they may well decide to use a true yellow filter on their camera (so it really can tell the difference between a mixture or red and green light - which would appear dark - versus true yellow light - which would pass through the filter and look bright). So even the photo we took with a satellite is hopelessly "wrong" compared to what we'd see with our own eyes or with a more traditional RGB camera. Then it would depend on whether we needed to be dark-adapted to see it (in which case it would all be pretty much monochromatic) - or whether our eyes were overloaded by the brightness (in which case everything pretty much looks white). Hence it doesn't make a whole lot of sense to be asking about the "real" color of objects in space - where the lighting is so very different from here on Earth where our vision system evolved.
If you have two cars - an orange one and blue one. Park them out in the street. In daylight - they look orange and blue. At night (in the dark) they look light blue-ish grey and dark blue-ish grey. At night under sodium street lights - they look orange and black. At night under moonlight they look orange and blue again. If you have a weak-green sensor because you are mildly color-blind then the orange car looks red. If you have cataract surgery and lose the filtering ability of your corneas - then if the paint used on the orange car happens to be strongly reflective of UV for some reason and the blue car not so much so - and they both look to be different shades of blue in strong sunlight - but revert to orange and blue on cloudy days. If you stand 20 miles away from the cars and look at them through binoculars with the sun behind your back, the blue car looks darker than it did before and the orange car looks more pale - perhaps, almost yellow-ish. If you do the same thing with the sun in front of you then the blue car still looks darker but the orange car still looks even more intensely orange. What color are the cars "really"? Well, it's a meaningless question. By convention, we humans say that they are orange and blue because we have decided that normal daylight vision is what we're going to use to label the colors...but in space, there is no "normal daylight" - so that labelling scheme fails.
Hence questions about the "real" colors of planets are not ones we could (or should) answer - it falls into the realms of predictions and speculations. We should leave it up to the astronomers to create spectrograms of the light and print graphs in journals...or we should send a poet/artist along in a capsule to write movingly about the things he/she sees there and paint pictures that speak to us of the color impressions that person got.
Good answer, but a major mistake in there. We don't have red, green, and blue sensors in our eyes. The wavelength response of the three cone types is something like what's shown in this picture. The L (long wavelength) cone's peak sensitivity is actually in the yellow-green range, and it's as sensitive to blue-cyan frequencies as it is to red. But when reproducing colors we want to be able to stimulate the S, M, and L cones as independently as possible, and red (which stimulates L much more than M) is better for that than yellow (which stimulates L and M about equally). Blue stimulates S almost exclusively, and green preferentially stimulates M. Thus monochromatic red, green, and blue are useful for reproducing color. They're not good for capturing color, though. Monochromatic red, green, and blue filters throw away most of the spectral information that you need to determine the correct cone stimulus levels in the first place. To capture the perceived color reliably you need to use filters that match the cone response curves. Once you have the SML stimulus information you can derive from it the RGB intensities that will most accurately reproduce that stimulus. Of course, there are tons of details. The curves are somewhat different on different parts of the retina. Real cameras don't use the right curves. The eye compensates for ambient lighting so that white objects still look white even when illuminated by colored light, but this process doesn't work when you're viewing the photographs later in different lighting conditions. No set of three primaries can reproduce all SML stimulus triples, and on top of that the primaries used on typical computer monitors are highly suboptimal.
But the number one problem with making true-color astronomical images is not the difficulty, it's the pointlessness of it. There's nothing magical about human color vision. The particular cone types we evolved served us well in the environment we evolved in (I think the red-yellow-green distinction helps in finding ripe fruit). They're meaningless on Mars. True-color images aren't interesting to look at, and they aren't any more true to life than false-color images. Compare this false-color image and this "true-color" image. (I put "true-color" in quotes because the filters they used don't match the human cones, so the color calibration involves a certain amount of guesswork.) Our eyes don't do a good job of seeing what's interesting in these exotic environments, and it's ridiculous to copy their limitations in our technology when we can do better. That's what technology is for. -- BenRG (talk) 00:11, 31 October 2008 (UTC)[reply]
I would argue that "true color" images are "More true to life" than the false color ones. Imagine I sent my handy digital camera to Mars, snapped it a few pictures and brought it back to Earth. When I reviewed the images, the colors on the screen that I observed with my eyes would at least roughly match the colors I would have observed had I gone to Mars myself instead of sending my camera.
I completely grant that true color images are not nearly as scientifically useful. And perhaps even not worth the money required to capture accurately. But it's disingenuous to claim that there isn't an element of truth in true color images that a false color image lacks. There is a very real, common desire to know what faraway places would be like "if I were there". To satisfy this (rather unscientific) desire you need to know what things look like to human vision under natural lighting. (And perhaps what they would look like under what us earthlings would consider a white flashlight.) APL (talk) 18:41, 31 October 2008 (UTC)[reply]
Yeah, you're right. I suppose the images could even have scientific value as a preview of what future Mars colonists would see out their windows every day. I don't know whether your digital camera would reproduce the Martian colors accurately; I think they're calibrated for typical Terran lighting conditions. NASA's true-color images were made very carefully if this page is to be believed—they took all the data they had available (six frequencies), guessed the rest of the visible spectrum by cubic interpolation, then derived the XYZ coordinates from that and converted to sRGB or something closely resembling it. Reading that gives me more confidence in the accuracy of the colors. Some of the other descriptions I'd read gave the impression that they just took the blue, green, and infrared data and stuck it in the blue, green, and red channels and called it true color. -- BenRG (talk) 22:50, 31 October 2008 (UTC)[reply]
Jupiter's Great Red Spot On Earth
I've searched a lot of places but can't find anything that helps me answer...
Say that our planet was an Earth-sized Jupiter. (I.E. we're Jupiter, but not Jupiter-sized.) How big would The Great Red Spot be on here? -WarthogDemon01:16, 30 October 2008 (UTC)[reply]
Let's do a little math. According to our article on Jupiter, the great red spot varries in size, covering an area of 24–40,000 km × 12–14,000 km. Using the formula for the area of an ellipse (pi*a*b) we get an area of 9.04x109 - 1.7x1010 km2. The surface area of Jupiter, according to the article is 6.21796×1010 km2. Thus, at the smaller end of the scale, the red spot covers 14-27% of its surface. Given that Earth's land is about 29.2% of its surface, the great red spot would cover somewhere between 1/2 and all of the Earth's land area. As a further reference point, the Atlantic Ocean is 22% of Earth's surface area, which falls in the mid-point of the estimated sizes of the Great Red Spot. Thus, if transcribed onto Earth, it would be roughly the size of the Atlantic Ocean.
Someone can check my math on this, but it seems about right... --Jayron32.talk.contribs02:07, 30 October 2008 (UTC)[reply]
Something must have gone wrong with the maths there. The Red Spot can't cover anywhere near 27% of Jupiter's surface, the picture on the Jupiter article shows that it covers a much smaller proportion (less than 5% I would argue by looking at the picture). According to Jupiter, the radius of the planet is 11 times larger than the radius of earth. From Atmosphere of Jupiter, the Red Spot's "dimensions are 24–40,000 km west–to–east and 12–14,000 km south–to–north." Divide them by 11 and you have the approximate equivalent. - Akamad (talk) 02:13, 30 October 2008 (UTC)[reply]
I double checked the maths, and the calculations are correct. There must be a problem with the numbers I used then; either the dimmensions of the Great Spot are too large, or the surface area given is too small. And divide by 11 wont work. If jupiter is 11 times larger, than its surface area is 112 times larger, so we would need to divide by 121. Dividing by 121 gives an Earth-scaled area of the great red spot as: 7.47x107 - 1.40x108 km2. Since Earth's surface area is given as: 5.10x108 in our article on Earth, that gives us an overall ratio of 14.6% - 27.4%, or the same thing I got by calculating it the other way. --Jayron32.talk.contribs02:30, 30 October 2008 (UTC)[reply]
Sorry I meant divide the 24 - 40000 km by 11 and divide the 12 - 14000 km by 11 too. So you are dividing the area by 121. I think the problem in the maths was that you used 24000 km and 12000 km in the Pi*A*B equation. The numbers used should be half that (12000 and 6000) since the equation refers to the distance from the middle. See http://www.math.hmc.edu/funfacts/ffiles/10006.3.shtml. - Akamad (talk) 02:36, 30 October 2008 (UTC)[reply]
(I wrote this during and edit conflicted with above. We had the same thought at the same time) I assumed that a and b in the ellipse area equation were the major and minor DIAMETERS of the ellipse. Its not. Its the major and minor RADII of the ellipse. My answers were thus off by a factor of 4. Thus, the actual % area is 3.65% - 6.85%. Since the surface area of the earth is 5.10x108 km2, that gives us an "Earth-scaled" size of 18,615,000 - 34,935,000 km2. North America covers an area of 24,709,000 km2 , which falls dead in the middle of this range. Thus, the Great Red Spot is roughly the size of North America, scaled to Earth's dimmensions. --Jayron32.talk.contribs02:39, 30 October 2008 (UTC)[reply]
OK - move aside - let a professional through here. OMFG! This answer is a train wreck!
Great_Red_Spot#Great_Red_Spot says "Its dimensions are 24–40,000 km west–to–east and 12–14,000 km south–to–north." - so diameters - not radii. Jupiter has a radius of 71,500 km. Earth has a radius of 6,380 km - so to convert dimensions on Jupiter to "Earth scale" you've gotta multiply by 6380/71500 which is 0.09 - or for mental arithmetic: Divide Jupiter-linear-dimensions by 11 to get Earth-linear-dimensions. So an "Earth scale" spot is 2,200 to 3,600km by 1100km to 1300km. Since there are big error bars in the original data for the spot size - let's cheat and pretend it's a rectangle of the smaller size...that way we avoid all of the ikky ellipse math stuff. So the area is roughly 2200x1100 = 2.4 million square kilometers.
Now - for comparisons: According to List_of_continents#Area_and_population, North America covers 24 million square kilometers - so I don't know how you arrived at "the size of North America"...that's wrong by a factor of 10! (Which is bloody obvious if you compare a picture of Jupiter and Earth scaled to similar sizes!)....so a third the size of Australia...or Texas plus Alaska...or somewhere between Sudan and Algeria...the drainage area of the Black Sea...I dunno.
The image (at right) was made by taking two NASA photos - one of Earth, the other of Jupiter. I resized the two images to be identical in size - then overlaid one onto the other. Finally I erased all of Jupiter EXCEPT the red spot. So - here is an image of what the OP is imagining. Notice in the top of the image we have Africa. The red spot looks to be maybe four times the area of Madagascar - which is half a million square kilometers - so two million seems about right (although it's a pretty fuzzy "spot" - so there is plenty of room for error)...anyway - it's NOTHING LIKE the size of North America.
The original question described a counterfactual situation ("we're Jupiter, but not Jupiter-sized"). In answering, we have to figure out what exactly that means. To me the obvious interpretation is that the relevant linear dimensions are reduced in the same proportion, as if making a scale model. That's what Steve did. The initial derailment that started the train wreck earlier was to try working with areas, which of course vary as the square of the linear dimensions. --Anonymous, 06:00:00 UTC, October 30.00000 :-), 2008.
Yes - it's a very common error to assume that since "A is 1/11th the diameter of B" that "The area of A is 1/11th of B" (when in fact it's the SQUARE of the linear dimensions - so A is 1/121th the area of B) and that "The volume of A is 1/11th of B" (when it's really the CUBE of the linear dimensions - so A is 1/1331th the volume of B). If I had $1 for every time I'd seen that mistake made I'd have...well, actually, maybe just enough for lunch today. The trouble is that the word "size" is vague - so you hear things like "Jupiter is 11 times bigger than the Earth" and "Jupiter is 1300 times bigger than the Earth" - both of which are true in some fuzzy-thinking way. That's why I was so careful to say "Divide Jupiter-linear-dimensions by 11 to get Earth-linear-dimensions." in my answer. SteveBaker (talk) 13:12, 30 October 2008 (UTC)[reply]
The trouble is, physics isn't scale-invariant, so it's really hopeless to conceive of an "Earth-sized Jupiter". The physics that formed and sustains the Red Spot, whatever it is, wouldn't form a scale-model Red Spot on an Earth-sized planet. I don't think an Earth-sized gas "giant" can exist in any case since it wouldn't have enough self-gravity to hold it together. So the only way to understand this question is as a visualization aid: to get a feel for the size of the Red Spot, scale it down to something more familiar. Personally, though, I find these comparisons singularly unhelpful. (As the saying goes, there is so much sand in Northern Africa that if it were spread out it would completely cover the Sahara desert.) -- BenRG (talk) 12:58, 30 October 2008 (UTC)[reply]
Yeah, I was curious about a size comparison. I understand how a Great Red Spot couldn't exist on Earth. (Though hurricane speeds can get pretty close to the same wind speeds.) And plus, if I put my question further and said what if we had the Great Red Spot composed of the same materials, it wouldn't last long: hydrogen-rich storm in an oxygen-rich atmosphere? Nope, nope, nope. :) -WarthogDemon16:46, 30 October 2008 (UTC)[reply]
That's true - but sometimes it helps people to bring vast or tiny things to "human scales" in order to think about them. Saying that the spot is "big" isn't helpful - and saying that it's 40,000 km across when Jupiter itself is the largest planet in the solar system doesn't give you a feeling for it either. But knowing that (compared to the size of the planet) it's like a third the size of Australia really gives you the strong idea that this is a really big thing. On the other hand - compared to the size of the planet - it's not that much bigger than the "great white spots" we get a couple of dozen times a year here on Earth. (We call them hurricanes and cyclones). Those can be up to 1000km in diameter - which (proportionate to the size of the planet) is only about half the size of the Great Red Spot. What's different about our hurricanes is that they can't sustain themselves over land - so they inevitably fizzle out after a week or two. Jupiter has no land masses - so there is really nothing to stop the spot from staying pretty much together for (at least) hundreds of years - we don't know whether it's truly a permanent feature. The Great Dark Spot on Neptunes southern hemisphere was a similar kind of storm - and it fizzled out sometime between 1989 and 1994, to be replaced by another one in Neptune's northern hemisphere. Saturn has shown similar features (eg Dragon Storm (astronomy)). SteveBaker (talk) 13:12, 30 October 2008 (UTC)[reply]
Well, that probably depends on the size of the alien more than the size of the planet. People have occasionally speculated that the Giant Red Spot IS an alien! But since Jupiter has no solid surface - anything living there must live in a gaseous environment - so it has to complete it's entire life-cycle flying or floating or something. The most likely form of such creatures would be massive solar-powered gas-bags floating around - and they could easily need to be very large indeed. So perhaps the spot doesn't seem all that big to them after all. SteveBaker (talk) 00:39, 31 October 2008 (UTC)[reply]
LANDFILLS - why are garbage cells covered with a layer of soil?
Having read the landfill page, I see that individual cells are covered with a layer of soil or in some cases another material. Innumerable other google-found webpages explaining landfills mention the same process. However, I can find no direct explanation as to WHY this is done?
Thank you.
To trap all that rubbish in a contained way. It will reduce smell, reduce vermin and scavengers, stop plastic bags blowing in the wind, and speed decay. Graeme Bartlett (talk) 06:08, 30 October 2008 (UTC)[reply]
To close the top is sometimes done to prevent rain water going in. The water will be contaminated and has a chance to reach ground water. Other possibility is air thight closing to collect the natural gas from decomposition within the landfill. You also get rid of the smell and the animals lifing in an open landfill (rats seagulls).--Stone (talk) 11:15, 30 October 2008 (UTC)[reply]
Also, gas (methane) from the landfill is sometimes collected for use as a fuel...the soil helps to trap this in. The main reason is to keep smells and litter in and vermin outGaryReggae (talk) 12:59, 30 October 2008 (UTC)[reply]
I'm the original poster, and I wanted to say thank you. :-)
The decomposing organic matter produces methane, and if the landfill is not adequately vented by perforated pipes driven through it or other means, the methane can work its way through the ground and come out in people's basements. Sealing the top of the landfill might increase the likelihood of this. Edison (talk) 19:14, 30 October 2008 (UTC)[reply]
Careful Steve! When the landfill is ultimately covered and landscaped, then yes grass can grow (although you want to be careful with trees due to the roots). But just covering each cell with soil is done at the end of each day as the landfill develops, for all the reasons given above. You're likely to be putting another layer of rubbish on top of that soil tomorrow, so there's no time for grass yet! 79.66.32.150 (talk) 21:12, 30 October 2008 (UTC)[reply]
This one has me stump
How the hell do you even go about solving problems like this. By the way I have not looked at the answer.
Ah! I think I got it. It's a trick question. There is a measuring device. It is called the water or the water level. Using the water level as a measuring device, measure out half the volume of water in the cylinder. 122.107.157.9 (talk) 11:07, 30 October 2008 (UTC)[reply]
Did you understand what Dmcq was saying? You still need to know a way to measure exactly half. You can't just eyeball it from the glass when it's level. If you don't get it, read his statement more carefully and think Nil Einne (talk) 12:31, 30 October 2008 (UTC)[reply]
As you very slowly pour the water out, there will come a point when the surface of the water just touches the bottom of the glass (and also just the lip of the glass on the opposite side) - at that moment - it's exactly half-full....like this:
That's one way to solve it. Another would be to completely fill the glass, and then get an identical glass and pour the water from the full one to the empty one until they both have equal amounts. --Russoc4 (talk) 19:59, 30 October 2008 (UTC)[reply]
Or you could get REALLY crazy. You could put the glass into a larger sealed container whose overall volume would allow the evaporation of the water to proceed until the vapor pressure of the water and partial pressure of the water vapor in the larger container were in equilibrium. Per the ideal gas law, you would only need to know the initial amount of water in the container you started with, and as long as you maintain a constant temperature, you make the volume larger container such a size as to allow exactly 1/2 of the original volume of water to evaporate. Its a whole bunch of algebra, but its certainly doable... --Jayron32.talk.contribs20:13, 30 October 2008 (UTC)[reply]
There's not much to measure really. Just maintain a constant temperature, and the ratio of the size of the larger, air-tight container should be some ratio of the size of the smaller, water filled cylander. This ratio is dependent ONLY on temperature and nothing else, so as long as you maintain a constant temperature, there is some ratio of large box/smaller cylander which will cause exactly 1/2 of the water to evaporate. You don't even need to know the volume of the smaller cylander; you just need to build a box that has a volume that is some number of times larger than that cylander. Here, let me work it out for you. At, say, 25oC, the vapor pressure of water, using this site: [5] to calculate, is 0.0312 atm. Now, once the partial pressure water vapor in the air is equal to this pressure, the water stops evaporating. So, lets assume, to make the calculations easier, that our cylander is 1 liter. So, we want 500 mL of water to evaporate. The density of water being 1 g/mL that makes this water have a mass of 500 grams. Divide by the molar mass of water (18 grams/mole) to give us 500/18 = 27.8 moles of water vapor. Now, by the ideal gas law, PV=nRT or for our purposes V=nRT/P, where V is the volume of the box we need, n=27.8 (moles of water vapor), R = .08206 L*atm/mol*K (the Gas constant), T = 298 K (25oC), and P = .0312 atm. Solve and you get V = 21789 liters. Now, the ratio of the amount of water to the size of the box should be constant, since less water would need a proprotionally smaller box, while all the other numbers remain constant. So as long as the box is exactly 21789 times the size of the cylinder of water, and assuming of course the air in the box was fully dry (leave a dessicant in there for a few days, then remove it right before putting the cyilnder in it), once the system equilibrates, the cylinder will be EXACTLY 1/2 empty. Oh, and for our 1-liter example, it IS a pretty big box. There are 1000 liters in a cubic meter, so the box is 21.789 cubic meters, or if a perfect cube would be 2.79 meters to a side, or about the size of the average bathroom. To answer your question, the ONLY measurement you need to make is the temperature. The ratio of the volumes is ONLY depedndent on this number. Once you know that ratio of volumes, you can simply create a box that is that much bigger than the cylinder. I never said it was an EASY solution, from a practical standpoint, but who cares about being practical. Plus, unlike the "tip the glass to the diagonal" solution, this one doesn't have the pesky meniscus problem. --Jayron32.talk.contribs02:43, 31 October 2008 (UTC)[reply]
All of these ideas (apart from my 'tip the glass' suggestion) fail miserably because the problem states that you don't have a measuring device of any kind. If you are going to argue that getting the temperature just right in a particularly-dimensioned box doesn't constitute using "a measuring device" then I might as well say "I'll just take a second glass of exactly half the height of the original but of the same diameter, fill it to the brim and carefully pour the contents into the first glass" - which is vastly easier and gets you to the correct answer much more realistically. But I'd argue that the terms of the question say you have a glass - and water - and absolutely nothing else of known dimensions or other definite properties - since anything like that confers the ability to measure. If you're allowed to invent your own devices to help - then there are easier and more direct ways. SteveBaker (talk) 18:17, 31 October 2008 (UTC)[reply]
Oh, you are entirely right. I was just having fun coming up with the most rediculous and esoteric way to remove half of the water from the glass. Your method of using the diagonal of the glass is, of course, the only scrupulously correct way. My solution had an air of Rube Goldberg to it, and I was just goofing. --Jayron32.talk.contribs19:02, 31 October 2008 (UTC)[reply]
There is a tradition at some US college or other that every year the following question is always asked on their 1st year general science term paper: "Given an accurate barometer, how do you determine the height of a tall building?" - the "correct" answer is obvious - but there has come a tradition of awarding extra marks for "other" answers. So, for example, one may climb to the top of the building, drop the accurate barometer over the edge and count the number of seconds for it to hit the ground - and thus determine the height. Or one could tie the barometer onto a length of string and use it as a pendulum - and by accurately timing a large number of swings, determine the variation in the force of gravity at the top and bottom of the building - and thereby determine it's height. However, the neatest solution is that you take the barometer to the custodian and say "I'll give you this beautiful (and highly accurate) barometer, if you'll tell me the height of the building". SteveBaker (talk) 02:07, 1 November 2008 (UTC)[reply]
On a pedantic level, visual perception when tilting the cylindrical container certainly is a conceptual measuring device. Clearly, you are - visually - measuring the property of the surface of the liquid in relation to the side walls / bottom of the cylinder.
I added a subject header to your post. You may want to take time to read the guidelines if you want to receive a better response. You also should sign your post Nil Einne (talk) 12:31, 30 October 2008 (UTC)[reply]
There are three basic types of rock:
"Sedimentary" rocks (like sandstone and chalk) form as layers of mud and other 'stuff' accumulate at the bottoms of lakes and oceans ("sediments"). Over millions of years, enough layers build up that the weight of all of that stuff pressing down on the lower layers compresses them into rocks. Since the sands and other silts that make up sedimentary rocks came from older rocks that had been eroded by wind, rain, rivers, etc - it's often the case that pebbles and other small bits of other rocks get mixed up into the sedimentary rocks.
"Igneous" (volcanic) rocks form when lava or ash comes out of a volcano. As it cools, it turns into various kinds of rock. Sometimes, small bits of other rocks that got crushed up by the volcano end up mixed into the igneous rock.
"Metamorphic" rocks are formed when igneous or sedimentary rocks are crushed under yet more pressure from rocks in layers above them changes their form or composition (they change...or "metamorphose"). Some of the chemicals in a rock may get washed away by water flowing through them - and some rocks may have small voids and bubbles filled in by stuff deposited by flowing water. Some rocks get heated up by lava or by being so far underground - those undergo all sorts of chemical changes.
See also Rock cycle for more info. Rocks are mostly various forms of silica and other silicon-containing compounds, though there are some other components that make for some sharp differences. The relative amounts of silica to other components will determine the differences between the rocks. --Jayron32.talk.contribs13:04, 30 October 2008 (UTC)[reply]
Some rocks contain metals, either in a pure form like gold or in combination with oxygen or other substances like hematite(which contains iron), and these are called Ore. Edison (talk) 19:12, 30 October 2008 (UTC)[reply]
Mathematics
A delivery boy collected 5.35 pesos part in 5 centavo coins, 8 part in centavo coins. If the number of 5 centavo coins were 7 more than one-half the no. of 10 centavo coins, how many 5 centavo coins?
There is a mathematics reference desk located at Wikipedia:Reference desk/Mathematics, but if you post the question there you are going to get the same response I am going to tell you. Wikipedia is not here to do your homework for you. If you need help finding information, we can point you towards articles (like Currency of Mexico, which contains info on pesos and centavos. But seriously, you can push the buttons on your calculator by yourself... --Jayron32.talk.contribs15:37, 30 October 2008 (UTC)[reply]
There is a standard method for this kind of question. Assign letters to all your unknowns (number of each type of coin) and then rewrite the problem as equations. You can then solve those equations to get the answer. --Tango (talk) 16:29, 30 October 2008 (UTC)[reply]
There is probably something wrong in the way you have rewritten/translated your problem, or else there is something wrong in the problem itself. As written, it's not solvable. The first sentence mentions five-centavo coins and centavo coins (i.e. one-centavo coins). The second sentence mentions ten-centavo coins and five-centavo coins. So you say you have three unknowns, but as far as I can see, you have only provided information for writing two equations. You need as many equations as you have unknowns. Also, the meaning of the first sentence is not clear. I don't understand what you mean by "8 part in centavo coins". However, if the first sentence should be "A delivery boy collected 5.35 pesos, partly in five-centavo coins, partly in ten-centavo coins", the problem can be solved as Tango suggested, by letting x be the number of five centavo coins, and y be the number of ten-centavo coins. I'll help you along by showing how you make the second sentence into an equation:
If the number of five-centavo coins were 7 more than one-half the number of ten-centavo coins
Just substitute x and y for the number of five- and ten-centavo coins:
If x were 7 more than one-half of y
Then replace the remaining words with numbers and the mathematical operators (= + - * / etc) that have the same meaning as the words:
x = 7 + 0.5 * y
Do the same thing with the first piece of information. Now you have two equations with two unknowns. Solve these, then you know the value of x and y. The answer to the question, "how many 5 centavo coins?", is the value of x. --NorwegianBluetalk22:44, 30 October 2008 (UTC)[reply]
My question is why women who are menstruating easily get or feel electrocuted once they simply touch a door knob or any thing that is made of metal?
That sounds unlikely to me. I can't see any reason for it. The chance of getting static shocks depends on what you're wearing (particularly your shoes), what kind of floor you walk on and also the weather (dry air doesn't conduct as well as humid air, so you can build up a charge easier). I can't see why it would depend on whether or not your menstruating. I guess it's possible that some women like to wear big fluffy jumpers when menstruating and that's what causes it, but that's about it. --Tango (talk) 18:22, 30 October 2008 (UTC)[reply]
It may be possible menstruating women are more sensitive to the sort of thing for some reason. But I agree with you it seems unlikely and there's no evidence so far to suggest otherwise. Nil Einne (talk) 12:46, 31 October 2008 (UTC)[reply]
Pay attention to the pi-bonding and the location of the hydrogen atoms in 3D space, and what effect that has on the strength of the C-H bond. Remember that an acid is any substance that easily loses an H+ ion, and that will be directly related to the strength of that C-H bond (i.e. the weaker the bond, the better acid it is). Another factor is the relative stability of the resulting carboanion (i.e. if you lose an H+ as an acid, you will leave behind a C- ion; and the pi-molecular orbitals in the triple bond system has an effect on the stability of that carboanion. --Jayron32.talk.contribs18:19, 30 October 2008 (UTC)[reply]
This page here: [6] also contains lots of good info on the reactivity of alkynes (the class of compounds that acetylene is the smallest member). Read closely the section titled "Acidity of Terminal Alkynes". --Jayron32.talk.contribs18:23, 30 October 2008 (UTC)[reply]
An sp hybridized carbon also has a higher electronegativity than sp2 and sp3, making the resulting carbanion relatively stable. --Russoc4 (talk) 20:01, 30 October 2008 (UTC)[reply]
"three-day malaria": would it call brain damage?
Hello. I'm playing Merlie Ryan in an adaptation of Carson McCuller's Ballad of the Sad Cafe. Merlie is known as "Crazy Merlie", and is generally the village idiot. In the book, it says he has the "three-day malaria", which means for two days he's dull and cross, then on the third day he livens up and has an idea or two, mostly foolish.
The entry for malaria says it can cause brain damage if you get it when you're young, so I'm assuming that's why he's foolish. But the play lasts for about 8 years. Could he have malaria the whole time? I thought you'd get better or get dead. And is it right that it might have caused some sort of cognitive problem? In the play he seems to be uninhibited, as if his sense of social appropriateness is missing. Might that come from the disease?
Slightly rambling question there, but I'd be grateful for any light anyone can shed on the effects of the disease.
(ec) Well, "three-day malaria" is "tertian malaria", which is that caused by Plasmodium vivax. The three-day cycle corresponds to the release of the merozoites from the liver and their invasion of red blood cells. Vivax malaria is not as bad as other forms of malaria, and is seldom fatal. The usual treatment is with chloroquine, which was developed in the 1930s -and was acknowledged as first line therapy since 1946 - I'm not cure if The Ballad of the Sad Cafe is explicitly set after this. But chloroquine alone doesn't cure the disease; to wipe out the liver infection primaquine is necessary, and this became available in the late 1940s, and wouldn't be widely available until after that, and so probably wouldn't figure in "Sad Cafe" published in 1951. So Merlie definitely would be expected to suffer from a chronic form of malaria that would last years and years. I don't think Merlie's foolishness is necessarily attributable to his malaria, though. But in answer to your specific question, absolutely he could have malaria the whole time. But no, people with malaria are not noted for being socially inappropriate in the way that, say, drunks, are. The brain damage in those who have it seems to result in cognitive difficulties: trouble in memory, in concentration, and learning. You could play Merlie as not caring much about social niceties because of his preoccupation with his own suffering; you could play him as unable to concentrate, with a short attention span; you could play him as mentally "slow". BTW, today we think of malaria as a disease of travellers, because it's been eradicated in the U.S. now, but in Merlie's time could certainly have been acquired here. - Nunh-huh21:28, 30 October 2008 (UTC)[reply]
Thanks for the prompt replies! We have set it finishing in 1945, so none of the treatments mentioned would be available to him. And it's useful to know that he could have suffered for the whole time without actually dying. "Unable to concentrate" seems to match most with my impressions of the character, but it's the way she links the three-day cycle of the disease with his activity and behaviour that confuses me - two days cross and dull, then livens up on the third to have a few foolish ideas. I thought at first this was a poetic way of saying he had some form of bipolar condition, but given that three-day malaria is a genuine thing, this seems less likely. Maybe having a fever involves less time shivering in bed than it does in my imagination, or maybe it's feverish in the sense of a feverish imagination.
78.86.213.238 (talk) 22:45, 30 October 2008 (UTC)[reply]
Well, it would certainly be fever in the sense of increased body temperature, but not all fevers involve shivering in bed or cold sweats. In 1945, he would probably have been taking quinine, which is not terribly effective (especially as it had to be made from cinchona bark rather than synthesized in 1945) but would have given some relief. - Nunh-huh01:14, 31 October 2008 (UTC)[reply]
There were some experiments with using malaria as a way to create fever and control syphilis, specifically neurosyphilis. The idea was that since malaria was a known quantity and would produce a fever that could be controlled by use of quinine, the patient would avoid the worst symptoms of the syphilis in exchange for the discomforts of malaria. Before you get too excited about the character's possible lurid past, the disease can be congenital (passed from mother to child). SDY (talk) 09:35, 2 November 2008 (UTC)[reply]
I caught a weasel in my house!
Well, its either a weasel or a ferrit (I thought it was a rat at first when I found it rummaging in my upturned kitchen bin and I was going to brain it with a claw hammer). The RSPCA man can't come to pick it up until tomorrow. I've put it in a cat carrier with some straw and given it water but what do I feed it? Sunflower seeds? Nuts? Hay? Carrots? They're similar to rabbits and other small rodents aren't they? --84.64.99.103 (talk) 21:54, 30 October 2008 (UTC)[reply]
It could also be a Stoat. You might not want to keep a ferret in the house - they REALLY, REALLY STINK! Anyway - it won't die if it goes without food for 24 hours - and you know it just ate when you caught it. You aren't doing it any favors by getting it used to getting free handouts from humans - so you should probably avoid giving it anything at all. So long as it has water and fresh air - it'll be fine. SteveBaker (talk) 00:28, 31 October 2008 (UTC)[reply]
Depending on where you live, it could also be a fisher cat or any other of a number of mustelids. Still, they are pretty much requisite carnivors, like a cat, so if you threw some hambuger or something in there, it should be fine. Cat food would probably work too... --Jayron32.talk.contribs02:23, 31 October 2008 (UTC)[reply]
Why not just let it go in the local woods where it can find its own food? I mean, unless it's injured I'd think the reason to call the RSPCA would be to catch it, which you took care of on your own, so why not release it on your own as well? --Shaggorama (talk) 05:58, 31 October 2008 (UTC)[reply]
Sorry, I should've made it clear. I'm quite sure that it's someone's pet. It's very tame. Either that or it's ill and weak (looks okay though). I fed it some beef last night and I gave it some cat food this morning. The guy is coming by to pick it up later. —Preceding unsigned comment added by 90.241.161.187 (talk) 11:54, 31 October 2008 (UTC)[reply]
I realize you boys are fisher-ing for laughs here, but if your dad told you were funny, he must'a lied. Frankly, you otter be ashamed at your stoatally stinky puns, but I'll stop badgering you now that I've skunked you. Matt Deres (talk) 14:05, 1 November 2008 (UTC)[reply]
Just a quick update. The mustelid I found turned out to be a ferret and was definitely an escaped pet. She was only a youngster too. She had a few ticks and was a bit skinny but otherwise seemed to be in reasonable health on first inspection. She's been taken to the animal shelter and all being well, will be rehomed if they can't find her original owner (apparently, they don't have much of a problem rehoming ferrets). --84.64.31.41 (talk) 17:19, 1 November 2008 (UTC)[reply]
I don't know exactly, but my initial guess is that ibuprofen might induce higher concentrations of the enzyme that metabolizes atenolol, therefore reducing the effectiveness of atenolol, assuming the parent compound is the active one. --Russoc4 (talk) 00:07, 31 October 2008 (UTC)[reply]
I'm pretty sure that atenolol is renally cleared, so that's not it. Also, ibuprofen reduces GFR (at moderate concentrations), which would be expected to reduce renal clearance (and increase atenolol concentration, all other things being equal). My guess is that the renal effects of ibuprofen would generally raise blood pressure, and that would counterbalance atenolol's effect. If there's a more direct mechanism, that would be interesting. --Scray (talk) 02:24, 31 October 2008 (UTC)[reply]
I had a further look around and found somewhere that it's an antagonistic effect due to NSAID-induced inhibition of renal prostaglandins, sodium and fluid retention. Thanks. —Cyclonenim (talk · contribs · email) 10:31, 31 October 2008 (UTC)[reply]
Yes, ibuprofen and other NSAIDs block prostanglandin synthesis, including PGE2. By the way, you know that beta-blockers are no longer recommended as treatment for hypertension? Axl¤[Talk]11:13, 31 October 2008 (UTC)[reply]
The problem was initially flagged by this classic paper in the Lancet. Beta-blockers will reduce blood pressure equally well, but they do not prevent the undesirable outcome: stroke, as effectively. There have been several other papers showing similar findings. Here is the Cochrane review. The NICE guideline states "the cost-effect analysis... [supports] the clinical data in that beta-blockers are the class of drug least favoured, and CCBs and thiazide-type diuretics appear the most cost-effective choices in most scenarios". Beta-blockers are now fourth-line treatment. Axl¤[Talk]11:37, 31 October 2008 (UTC)[reply]
That's 4th line as a a sole agent, I think most UK doctors would demote slightly further given that as multiple drugs are introduced, so patient's would typically already be on bendroflumethiazide... and thiazides in conjunction with atenolol is diabetogenic which I understood was final issue (on background of above cited findings of less good outcomes) - so likely alternative would be of an alpha blocker... but that's to digress away from avoiding NSAIDs in hypertensive patients, but also relevant to mention is that long term NSAIDs may cause deterioration in kidney function... David RubenTalk02:21, 2 November 2008 (UTC)[reply]
preventing liver spots?
i'm 23 and my hands look fine, but I wouldn't like to have liver spots all over them when I'm 76. Do you think I can do anything (daily) or avoid doing something so I won't get them eventually?
My textbook says concentration of pure solids and liquids is taken as unity.But no explanation is given as to why.Can some1 please why is it taken so?
"Concentration" in what sort of units? If you are asking about %, it should make some sense that a pure sample of some chemical X is "100% X" based on the standard meaning of percent ("X is what fraction of the whole?"). But for concentrations that aren't just "fractional of the whole", it's clearly a false statement: 1 g of water is 1/18 mole and has a volume of 1 mL, so it most certainly does not have a molarity of 1 mol/mL. DMacks (talk) 23:58, 30 October 2008 (UTC)[reply]
It is because 1 part in 1 is that pure substance. And 0 parts in 1 of anything else. In reality what you may call pure sugar for example will have air between the crystals, and the density of the bulk material may be below that of a pure uniform crystal. They would be saying the concentration of H2O in water is 1 and the concentration of NaCl (or anything else) in pure water is 0. Graeme Bartlett (talk) 00:03, 31 October 2008 (UTC)[reply]
Actually, the above is not really the reason. It sounds good, but it doesn't get to the heart of the problem. The one could certainly calculate the "concentration" of a pure solid. It would merely be the density (grams/liter) divided by the molar mass (grams/mol). You would get mol/liter, which is of course concentration. After all, we can and do use concentrations of pure gases, and their calculation can be done essentially the same way. The same problems where a pure gas concentration is used as calculated, the pure solid concentration is treated as unity. This is not the same thing as being equal to one, but we'll get to that in a minute. The question is "Why do you need to know the concentration?". For the problems I am guessing you are doing, you are probably working in kinetics and equilibrium, that is the problems are largely dependent on the rate of reaction. The rate of a chemical reaction is dependent on the number of collisions occuring between the reactants. In gases and aqueous solutions, the reactants are spread out over a large space, so how often they colide is a direct function of how close together they are packed. If you double the number of molecules of a gas or an aqueous solution in a given space, the number of collisions doubles as well, because the molecules are forced closer together. Thus, changes in amounts effect changes in rate. Now, here's the thing with pure solids and pure liquids. They are condensed phases, which means that the molecules are already touching essentially. If you, say, double the number of molecules of a pure liquid, you don't effect the rate at which those molecules collide since those molecules can't be forced closer together. Thus, for questions that involve rates of reaction, the amounts of condensed phases don't affect the rate of the reaction. In our calculations, we ignore these amounts because they don't change the outcome. Ignoring them is the same as multiplying by 1 (since multiplying by 1 doesn't do anything at all). So we say that we treat them as "unity", but we could just as easily say we ignore them all together, because they don't affect the outcome. When you do an equilibrium calculation, well, the equilibrium is just a situation where the rates of the forward and reverse reactions are equal. Since equilibrium is determined by rate, and solids and liquids don't effect rate anyways, we can ignore these here too... --Jayron32.talk.contribs02:18, 31 October 2008 (UTC)[reply]
Having been a chemistry teacher for 10 years, I think I am fairly qualified to make these assumptions. The only type of situations where one finds the statement "treat the concentrations of solids and liquids as unity" is in the kinteics and equilibrium chapters of your standard general chemistry textbook. Its the particular phrasing he used, and that he mentioned that it came from his textbook that cued me in on the kinds of problems he was working out. Trust me on this, he's working out rate law and equilibrium problems. --Jayron32.talk.contribs03:26, 31 October 2008 (UTC)[reply]
Yup. The real problem is when they think that context doesn't matter, which is why I led with that caveat. Otherwise they get into my chemistry class and tell me "the concentration of water is 1" or "solvents don't have a concentration themselves" because that's what they were told, not knowing what the heck it actually means:( DMacks (talk) 04:04, 31 October 2008 (UTC)[reply]
When working with reaction rate and equilibrium-type problems, you're not actually using the concentration of the substance, you are using the Activity (chemistry). This isn't an absolute measure, it's a dimensionless relative measure. Usually, the reference concentration is taken to be 1 mol/L, so that the activities match exactly with the concentration. However, this is not always the case, and very concentrated solutions can have activities which differ numerically from their molar concentration. In the case of solids, the activity doesn't change when increasing the amount of undissolved material. Thus the activities are constant, and are effectively rolled into the rate constant or equilibrium constant. The same thing happens with rates and equilibria in aqueous solution: the amount of water in most solutions is near constant (~55 M), and varies very little from one aqueous reaction to another, and is defined as unity. If you happened to be working in a solution where the concentration of water was significantly different from a normal aqueous solution (e.g. in a highly concentrated alcohol in water mix) you would have to explicitly account for the water concentration, and would have to use rate and equilibrium constants which account for this. -- 128.104.112.72 (talk) 15:51, 31 October 2008 (UTC)[reply]
October 31
Why is space so big?
I mean, isnt the distance just....overwhelming? You cant wrap your mind around it! Just think about how big a light year is. The distance that light travels in a freakin' year, that's what! That's 11,600,000 miles in just one minute! ....Wow Wow Wow...When we say that something is millions of light years away, I just...can't comprehend it.--Sunburned Baby (talk) 02:56, 31 October 2008 (UTC)[reply]
Space is so big because its been around for a long time. If we consider that the availible evidence tells us that the universe is expanding, and since we know about how fast it IS expanding and about how long it has been expanding, we get an estimate for how big the whole thing is. And the answer is REALLY FREAKING HUGE. No shit. I used to teach an Earth Science class, and for the astronomy unit, I would take the kids out to the football field to map out the solar system. If you put the sun at one goal (endzone or soccer goal, its about the same size) and put pluto/neptune at the other goal/endzone, then on that scale the sun is the size of a Quarter coin, and the earth is about the size of a speck of sand. And that's ONLY our solar system, which if scaled to such a size so that the galaxy could fit on a football field, the entire solar system would be a speck of sand. And if we put our galaxy on a football field scaled to teh size of our local group of galaxies, it would be a speck of sand, and so on and so on. Feeling insiginficant yet? --Jayron32.talk.contribs03:14, 31 October 2008 (UTC)[reply]
I never know whether saying "the volume of the observable universe is around 3×1080 cubic meters" makes the size seem more or less comprehendable. At least I can actually consider how immense that is, rather than saying "larger than I can imagine", but then I have troubles imagining 1080. DMacks (talk) 04:11, 31 October 2008 (UTC)[reply]
Often when one gets a question like this it makes sense to invoke the anthropic principle and assert that if it weren't just so then life as we know it wouldn't be here to observe it. However I'm not sure if that is the case here. What if instead of being 3×108 m/s, the speed of light were only 3×104 m/s ? The visible universe would be 1/10000 the diameter it is now, but would it really matter? We'd expect our new universe to have room for ~1 galaxy, but who needs the other galaxies anyway? Satellite communication might suck, and microchips wouldn't be as speedy, but does life as we know it really require such a large c?
As far as I can tell, the answer would appear to be no. Are there any really fundemental downsides to envisioning a universe with a much slower speed of light (and hence a universe that grows much more slowly)? Dragons flight (talk) 04:28, 31 October 2008 (UTC)[reply]
The point is that the processes that created our galaxy require a universe with more than just our galaxy. Our galaxy exists only because the processes that create galaxies require a universe which is pretty much exactly the size it is now, with a fundamental speed of light equal to exactly what it does in our universe. If the laws were not so, the conditions would not exist to create the Universe as it is, with us studying it. Its not just about whether or not we could survive in a 1-galaxy universe with a slower speed of light; we could, its that such a universe could not have come into being in such a manner as to create the necessary conditions for life to exist. The Anthropic Principle is a bit of a tautology, but a useful one. --Jayron32.talk.contribs04:45, 31 October 2008 (UTC)[reply]
That's merely an assertion, not an explanation. What about the big bang and structure formation requires lots of space? Galaxies nucleate from primordial density fluctuations that would presumably still exist. The necessary mass only comes from a sphere ~10 times wider than the ultimate disk of the galaxy itself. I don't see any reason all that other distant mass is actually necessary to forming a galaxy. As best I can tell, the dynamics of galaxy formation don't require the universe to be huge. Dragons flight (talk) 05:06, 31 October 2008 (UTC)[reply]
Having a small speed of light would also affect speed of gravity, and a galaxy may not form as big as we know it. Then you may find a lack of heavy elements needed to make planets and humans. We also need plenty of space to make a cold background in the sky, so that solar energy can drive life on earth. Graeme Bartlett (talk) 05:36, 31 October 2008 (UTC)[reply]
Look man, space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space. Listen: When confronted by the sheer enormity of space, better minds than the ones responsible for this reference desk have faltered. Some invite you to consider for a moment a peanut in Reading and a small walnut in Johannesburg, and other dizzying concepts. The simple truth is that interstellar distances will not fit into the human imagination. :) --Shaggorama (talk) 05:51, 31 October 2008 (UTC)[reply]
I can easily envision space being much much much bigger say a googleplex times as wide or maybe another power or two than that. Why is it so small relative to us? Perhaps it just couldn't be any smaller. Dmcq (talk) 09:06, 31 October 2008 (UTC)[reply]
Big can be looked at in other ways too: which is more, stars in the Milky Way or cells in a single human brain? stars in the Universe or bacteria in the oceans? Franamax (talk) 09:33, 31 October 2008 (UTC)[reply]
My very quick research shows there are about 2-4 times as many stars in our galaxy as there are neurons in the human brain (I don't know about other cells). I have no idea how many bacteria there are in the oceans, though... --Tango (talk) 17:22, 31 October 2008 (UTC)[reply]
You need to be careful when considering what would happen if a physical constant were different. All the constants are interrelated, so if you're changing the speed of light you're going to have to change some others as well. What would happen will depend on which ones you change and in what way. There is a way of doing it (I don't remember the details) that results in pretty much no observable change at all because it results in atoms being 10,000 times smaller, and therefore everything else is 10,000 times smaller (that doesn't follow exactly, but I think the conclusion is still correct) so the time it takes for light to get from A to B is unchanged since A and B are just closer together. --Tango (talk) 10:43, 31 October 2008 (UTC)[reply]
"Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams88.211.96.3 (talk) 11:25, 31 October 2008 (UTC)[reply]
Which seems fairly complete. In the absence of faster-than-light technology, which seems unlikely to say the least, humans are just not really going to get very far as a species in space. Look upon "we'll colonize space!" proposals with a gimlet eye unless someone suggests a really plausible explanation of how we'd get significant numbers of people (e.g. significant breeding populations) anywhere useful within the lifetimes of those traveling. --98.217.8.46 (talk) 13:26, 31 October 2008 (UTC)[reply]
I believe the trick is NOT to try to do it in the lifetimes of the people inside. We need huge, landscaped, spinning (for artificial gravity) mini-worlds made from hollowed out objects from the 'belt - each with LARGE populations (thousands of people at a minimum). Power will have to be from fusion sources to keep the fuel supply compact enough - and the progress from one star to the next has to be expected to take thousands of years. It seems inevitable that such habitats will be needed in the future - and once there are enough of them in solar-orbit - it's only a matter of time until one of them takes on the trip. If you are living your life in such a place anyway - it may not make much difference to you whether you are orbiting the sun - or heading off to Alpha Centauri with no hope of arriving during your lifetime.
An alternative (which is perhaps more likely to be of interest and I'm fairly sure will happen in the next 100 years) is the "scan your brain - produce an exact software simulation of it - then die". "You" will continue to exist with all of your thoughts and memories intact inside a computer somewhere - presumably with some kind of robotic body with robotic senses. You feel like you are still "you" and your family and friends can easily tell it's still you - and you behave pretty much like any other human - albeit in that robotic body. Now we can do a couple of interesting things:
Shoot a small, unmanned probe to the next star. It's small - it gets there in 100 years and proceeds to drop off some handy robots. When it arrives, we transmit a colony of humans by radio or laser communications to the probe and thence to the robots. Elapsed journey time is at the speed of light - but to the traveller it would seem instantaneous. When you arrive, you live out your life in a robotic body - and if you want to return - you simply transmit yourself back again as another radio signal and you're home again in the blink of an eye. The travel time is still at the speed of light - so it's gonna take 4 years to go and 4 years to come back from Alpha Centauri - but 8 or 9 years away is not so terrible if you don't have to endure the journey.
Using a very small probe - shoot a computer and a robot body to the nearest star. But have the computer's clock rate be adjustable. When there is nothing much happening, it executes one instruction every second - when there is an emergency - or at the start and end of the journey - it runs at a few teraflops. Your brain can 'fast-forwards' through the boring parts and consume almost no energy - and zero other resources. When you arrive, you ramp the clock up to full speed and download yourself into the robotic body to do whatever exploration you fancy. Sure - it takes hundreds of years to get there and to get back again - but you won't die of old age and you won't get bored.
Once you can 'fast forward' your life through the boring bits and have your thoughts and memories transmitted and reconstructed at the speed of light - you can live as long as you want to - and there are a LOT of interesting possibilities.
A wonderful Star Trek-like solution, but the humans you imagine have little to do with any humans I have ever seen. Make a big dome, put a few thousand humans inside it, wait a few weeks and they'll be in a state of civil war, disrepair, disaster. I don't see us getting off this planet in any major way. The human race will, at some point, go extinct—of that there cannot be any question. Once you accept that it just becomes a question of when and where. --98.217.8.46 (talk) 21:12, 31 October 2008 (UTC)[reply]
There are plenty of remote groups of humans with populations under 1000 who manage just fine. The Pitcairn Islands had a rough start - but they survived and thrive today with almost no contact with the outside world and only just barely enough genetic diversity to keep going. I don't see the need for passimism in that regard. As for the "humanity" of the humans I imagine - well, I think what matters is our intellects - and what I suggest would preserve that in the purest way possible. You might think we couldn't survive that - yet wikipedians talk via the clunkiest links - form friendships - and seem in every way "human" - even though we rarely meet face to face. If my brain was merely simulated on a big computer - I don't see how you could possibly tell. SteveBaker (talk) 01:48, 1 November 2008 (UTC)[reply]
Sure, they have their problems - it's inevitable. But recall that I was responding to: "wait a few weeks and they'll be in a state of civil war, disrepair, disaster"...and after 200 years, the Pitcairns are not only NOT in a state of civil war, disrepair OR disaster - but they actually have a legal system, a school and so forth. I don't pretend that a community of a thousand humans heading off for a thousand years in the direction of Alpha Centauri wouldn't have problems - sure, there will be criminals, there will be horrible divisions about matters of policy - but they can deal with that if they have no alternative - and the Pitcairn Islanders are about as close to that situation as I can easily find information about. But small tribes out in the Amazon have also been found who have been more-or-less cut off from other humans for centuries and are doing OK. SteveBaker (talk) 17:41, 1 November 2008 (UTC)[reply]
This can't be allowed to pass unnoticed : "If [SteveBaker's] brain was merely simulated on a big computer - I don't see how you could possibly tell."APL (talk) 16:58, 1 November 2008 (UTC)[reply]
Photons and Phonons
In special relativity, light are waves, and the inertia of objects increase as the velocity of objects increase toward the speed of light. sound are also waves, so do the inertia of objects increase as their velocity increases towards the speed of sound? —Preceding unsigned comment added by Superwj5 (talk • contribs) 12:14, 31 October 2008 (UTC)[reply]
Short answer, no. You get interesting aerodynamic effects as you approach and pass the speed of sound (sonic booms, etc), but nothing relativistic. While light and sound are both waves, they are very different things - sound is compression waves in a medium (air, usually), light doesn't have a medium, it's just self-propagating electric and magnetic fields. Light is a fundamental feature of the universe, sound is just a consequence of vibrations in matter. --Tango (talk) 13:19, 31 October 2008 (UTC)[reply]
Bosenova
Does anybody even have any evidence what Bosenovae really are? Or at least some possibilities and guesses? I think they might have entered an unknown interaction and changed into sparticles, bosinos or dark matter or perhaps the magnetic field stuck some of the atoms into their Schwarchild radius in quantum gravity and Hawking radiated into other stuff? Do you have any idea what it is? —Preceding unsigned comment added by Superwj5 (talk • contribs) 12:22, 31 October 2008 (UTC)[reply]
Apart from what the Bosenova article says, no people don't know exactly. But you'll find proposed theories on it if you search arxiv.org and scholar.google.com. For instance, Phys. Rev. Lett. 89, 180403 (2002) Mean-Field Theory of Feshbach-Resonant Interactions in 85Rb Condensates implies 'rogue dissociation. For a definition, see arXiv:physics/0607075v1 but simply put the atoms in the bose einstein condensate spontaneously turns into molecules, which are then repelled. This process is more likely at certain densities than others. EverGreg (talk) 14:34, 31 October 2008 (UTC)[reply]
The basic principle will work - you throw something out the back you'll get an equal and opposite reaction pushing the rocket forwards. However, resistance from the water would make an underwater rocket extremely inefficient, probably to the point of being useless. The same is true of air, to a lesser extent, rockets are significantly more efficient in a vacuum than in the atmosphere. That's one of the reasons for taking off vertically and then going sideways to enter orbit, rather than taking off diagonally to start with - you spend less time in the atmosphere. Propulsion underwater usually involves taking in water from the front and expelling it out the back (eg. using a propeller), that turns out to be far more efficient that expelling rocket exhaust out the back. --Tango (talk) 16:37, 31 October 2008 (UTC)[reply]
Yeah, what are you guys talking about? Rockets work just fine under water. They just don't move as fast. Missiles are routinely launched from submarines underwater, and you can fire a fireworks rocket or Estes model rocket into a swimming pool and observe that it still works. ~Amatulić (talk) 21:01, 31 October 2008 (UTC)[reply]
Sure - the distinguishing difference between a rocket and a jet is that a rocket contains it's own oxidizer. Hence it likely burns just fine underwater. Gasses still shoot out of the back pretty quickly - and Newton's laws guarantee that if something shoots out of the back - it WILL go forwards. The only question is thrust-versus-drag ratios that will affect your accelleration and top speed underwater. SteveBaker (talk) 01:37, 1 November 2008 (UTC)[reply]
How to select motor rating for pure electric vehicle
(moved from Village pump).
If i want to replace a 150cc IC engine base two wheeler with an electric vehicle run by a direct drive motor what rating of motor will i have to use??? Is there a direct relation between cc and kW of the machine??? Any help please??? —Preceding unsigned comment added by LifestyleBangalore (talk • contribs) 16:38, 31 October 2008 (UTC)[reply]
Try to find an equivalent horsepower or kW rating. The cc number for an engine tells you very little about the power it can produce these days. It's a bit more complex than that though - electric motors have spectacular low-end torque - so you can get really great 0-60 times with a fairly wimpy little motor - but then find that your top speed sucks. That may not matter if you do lots of in-town driving and very little freeway - but it's easy to be fooled by those kinds of numbers. Also, without a gearbox, you need a very flat torque curve across the entire RPM range - electric motors are pretty good at that - but some are much better than others. SteveBaker (talk) 18:03, 31 October 2008 (UTC)[reply]
They're usually referred to as "Office Partitions". A google search will get you loads of suppliers sites, and an image search lets you see the variety on offer. Fribbler (talk) 18:26, 31 October 2008 (UTC)[reply]
Not all open office dividers are "cubicles". My office is a donut design. The elevators, plumbing, and main cabling are in the middle. Offices are around the outside windows. They are divided using full-height walls and doors that appear to be real fixed walls. The advantage is that the maintenance people can move walls around to enlarge or divide offices as needed. -- kainaw™21:11, 31 October 2008 (UTC)[reply]
"Oh look, see, its not a square office, so your not a mindless paper-pushing drone like those people who have to work in cubicles. See, you mean something as an individual cuz you work in a round building!". Industrial psychology writ large... --Jayron32.talk.contribs02:35, 1 November 2008 (UTC)[reply]
Is that worse than: We took out all the cubicle walls so you can see your coworkers all the time and have no privacy at all because who needs privacy when we're all one big happy family. -- kainaw™16:58, 1 November 2008 (UTC)[reply]
My perception of quality-of-life at the workplace has been largely independent of the various office layouts I have experienced. With large offices containing dozens or hundreds of employees with individual preferences, it will be hard to maximize the layout-to-happiness quotient (first you have to find some way to measure that). I tend to think that a lot of employees complain about all office layouts, and have no real motive other than whining. Nimur (talk) 18:30, 3 November 2008 (UTC)[reply]
In sci-fi, whenever there is an EMP everyone runs around frantically turning everything off. Does that actually help? If so, how? My understanding of the relevant physics suggests it wouldn't (and the unreliable sources I've found via google tend to agree), does anyone know for sure? --Tango (talk) 22:15, 31 October 2008 (UTC)[reply]
That makes as much sense as space ships executing banked turns in weightless vacuum, or having high-current power lines running behind display panels so they emit showers of sparks when something bad happens.
No, turning things off after an EMP event accomplishes nothing. It may help to power-off stuff before the pulse. In my industry, we can incorporate nuclear event detectors that cause critical equipment to switch off automatically, to protect them from EMP, and the equipment itself is designed to be "hardened" against such events in the first place. ~Amatulić (talk)
Sorry, I should have said "whenever there is *going to be* an EMP", obviously turning things off after they've been fried isn't going to help. --Tango (talk) 22:48, 31 October 2008 (UTC)[reply]
I think the OP is asking, "does EMP only affect things that are turned on in the first place". I mean, does turning things off change anything if they are not hardened to EMP in the first place? --98.217.8.46 (talk) 22:51, 31 October 2008 (UTC)[reply]
There is absolutely no doubt that EMP is "real". In the early 1960s, computers used clunky 'Ferrite core memory' technology. You could literally see the individual bits as little grey donuts threaded on wires. One interesting thing about core memory is that it's magnetic - and if you turn your computer off and back on again, it doesn't wipe the memory as happens with "DRAM" technology. As core memory became obsolete, the very last application of it was in military aircraft that were designed to deploy nuclear payloads. After they dropped "the bomb" - and turned around to get the heck out of there - the aircraft stood a chance of catching the EMP from it's own weapon. Hence they used core storage in their flight computers - so that the computer could be turned off and rebooted without losing a beat.
What an EMP does is to induce voltages in metal objects in its path. If you are close enough - and the geometry of the metal is just right - that voltage may be large enough to disrupt or destroy the circuit. Whether turning it off helps has to depend on an awful lot of things. Let's imagine some delicate piece of electronics with two LONG wires going off to a switch and a battery. If the wires lie in one pattern then the voltage will be induced between the battery/switch and the electronics - and both ends of the wire that contact the electronics could be at the same voltage - the electronics themselves might be small enough to to pick up any significant voltage at all. In that case, the electronics are probably undamaged. If we imagine another situation where two wires lead out of the electronics in opposite directions then the induced voltage could be large and fry the electronics instantly. If the switch happens to be up close to the electronics - and breaks the physical connection between the long wires and the electronics - then sure - turning it off beforehand ought to reduce the risk...but it's certainly not going to ensure it'll be undamaged. Turning the switch off AFTER the pulse has passed is obviously pointless though.
So - if you know an EMP is coming - I guess you should turn off anything you can get to in time - there is no guarantee it'll help - but then there is no guarantee that an EMP will destroy everything electronic/electrical anyway.
So the key thing is not so much to have things switched off as to have them unplugged (or otherwise isolated from the long wires), so if you have a laptop running off its battery, it's not going to matter whether it's on or off? --Tango (talk) 01:54, 1 November 2008 (UTC)[reply]
Yes exactly. Most things plugged into the power grid will likely be fried - an EMP crossing those mile-long power lines (or even the shorter ones that go into your house) induces one heck of a voltage. The longer the conductor, the more voltage induced for a given EMP. I think the "magic number" is 30 inches (76 cm) for nuke-level EMPs to damage sensitive electronics. Not sure what era's electronics that was for though. ArakunemTalk14:47, 1 November 2008 (UTC)[reply]
I'd like a little more information about aneurysms that I couldn't find in the article. First, what ages can get them? Can you even have them from birth? I know the article did mention men have a higher risk than young women, but would it still be reasonable for a teenage girl to have an aneurysm? Also, if they burst, does it always lead to death? Thanks for the help! 71.13.209.44 (talk) 22:40, 31 October 2008 (UTC)[reply]
Aneurysms can be present from any age, as far as I'm aware. I read a case study of a 1-month year old male who had one, so it is possible, but the risk increases significantly with age and aneurysms in paediatric patients are rare. If you're asking about teenage girls having aneurysms, and you are that teenage girl, I strongly suggest you seek the help of a doctor. It is possible for a teenage girl to have an aneurysm, but again, it'd be rare at such a young age. If an aneursym ruptures, a lot of factors can determine the outcome. Where was the aneurysm? Aneurysms in the brain feature high mortality rates, same with the aorta (this one in particular is incredibly high without prompt medical treatment). However, they do not always lead to death —Cyclonenim (talk · contribs · email) 23:15, 31 October 2008 (UTC)[reply]
I'm wondering if chimpanzees and apes/gorillas have menstrual periods like humans, or if they have an egg already ready and waiting, and if that is the case, do the females go into "heat" like cats and dogs?Cindycat (talk) 00:47, 1 November 2008 (UTC)[reply]
Its a good question. We have three articles on Chimps: Chimpanzee, which covers the genus Pan in general, and the two species of chimpanzee: the Common Chimpanzee and the Bonobo or pygmy chimpanzee. Chimpanzee females of both species exhibit what is called "genital swelling", an engorgement of the vulva, which is an indication of being ready to mate. Common Chimpanzees only exhibit this during fertile periods, while the Bonobo female is pretty much in a state of constant sexual readiness, regardless of fertility. However, our articles coverage on Chimpanzee sexual physiology is lacking, and I am not much of a zoologist, so I will have to defer to a more expert person beyond that. As far as Great Apes beyond the Chimps, well, 3 genus (Chimp, Gorilla, and Orangutan), 6 species, and about a dozen or so subspecies of Great Ape, and our articles there don't expand much on this either. --Jayron32.talk.contribs02:30, 1 November 2008 (UTC)[reply]
This seems to be the best answer that the internet has to offer. Accordingly, only great apes would appear to have true menstrual flows, though many mammals have cycles where the uterine wall becomes receptive to implantation. In non-apes, that tissue is usually reabsorbed if no pregnancy occurs, with little or no overt blood loss. In a few species, blood loss is observed during ovulation (as distinct from menstruation). Dragons flight (talk) 05:27, 3 November 2008 (UTC)[reply]
When was the speed of sound broken (by man made object)
I think our OP merely means that while Yeager is widely credited to be the first person to break the sound barrier - his plane was not the first man-made object to go supersonic. SteveBaker (talk) 13:22, 4 November 2008 (UTC)[reply]
Can anyone give me suggestions or give me tips and things to look out for? I am building a ROV with a constraint of using these materials provided to me:
2 24" PVC pipes
10 L-joints
10 T-joints
3 motor mounts
The tethered ROV will be dropped and launched in a 50x25m pool. The ROV will pick up a metallic object using an electromagnet and will drop it on a target elsewhere in the pool. --hello, i'm a member | talk to me!04:15, 1 November 2008 (UTC)[reply]
Well - clearly you can take 4 L-joints and 4 straight bits and make a rectangle. Do that twice and you have two rectangles. You can cut each of the straight bits in two and insert the 'top bar' of a T into the middle of each side of each rectangle. Now, use four more straight bits to connect together the verticals of the T's to make a cube. Fix on your motor mounts (I have no idea how - without a picture, it's hard to know - but you have two more T's and two more L's to make more structure if you need to make that mounting go more smoothely. I presume you have a way to control the speeds of the motors - and if you only have 3 motor mounts - then you probably only have 3 motors. I would put two on two sides of the ROV - pointing backwards - and one on the bottom - pointing downwards. By driving the bottom motor forwards or backwards - you can make the ROV rise or sink - by using the other two motors together - you can go forwards or backwards - and by driving one forwards and the other backwards, you'll be able to spin on the spot. The most important thing (IMHO) is to weigh your motors, batteries, electronics and other on-board stuff to figure out how much pipe you need to make the thing only JUST float. You can measure the outside diameter of the pipe and figure out how much water it displaces and make sure that your total displacement is slightly more than the weight of the machine itself. You don't want it to float too well because if you do, the "up/down" motor won't be powerful enough to make it sink. If you don't make it float well enough - then if something fails (and it will), it won't just naturally float to the surface. You're unlikely to get this exactly right the first time - so aim to make it float a bit more strongly at first - and you can always shorten the tubes to shave off a bit of bouyancy before you finally glue the whole thing together. SteveBaker (talk) 17:19, 1 November 2008 (UTC)[reply]
Without knowing what kind of attachment point you have - or the size of the thing you're trying to pick up - it's hard to know - but you need to be sure that the object doesn't unbalance the ROV when you pick it up because you don't have enough motors in the design to correct things if it ends up being (say) pointed downwards at 45 degrees. Your bouyancy calculations have to be a compromise between being neutrally bouyant WITH the object attached and WITHOUT the object being attached. If the object is very small/light then that may not matter at all - but if it's big and heavy compared to the ROV then it'll matter a lot. Ideally - you'd like the electromagnet to be at the bottom - in the center of the craft so it won't get unbalanced - but sadly, that's also where you'd like the vertical thruster to be - and they can't both be there! Can you let the electromagnet dangle on a wire a foot or so below the craft? That would be the simplest thing - and the end of the wire could then be pretty central to the ROV without disturbing the thrust from the vertical motor. There must be other parts allowed in the design - because your list doesn't include the motors or the propellors or the means to control them - you must be allowed things like cable-ties or electrical tape - and I'm sure you can use those to hold the electromagnet - or it's wires - to the structure. The critical thing that I'm trying to impart here is the vital necessity of the thing being slightly (but only slightly) positively bouyant - and being balanced, both when stationary and when thrusting and both with and without the load it has to carry. A little positive bouyancy is good because you'll be able to easily retrieve it when (not if!) it fails during testing - yet too much positive bouyancy will prevent the thing from being able to dive when the downward-pointing thruster is activated. Since your only source of bouyancy is the tubular structure of the ROV itself, you need to calculate that stuff up-front (don't guess!) and be prepared to tweak the lengths of the tubes until it floats absolutely how you want it to. Since you have limited amounts of tube - you need to start with them being a little longer than your calculations suggest so that you can cut them down as needed (you can shorten a tube - but you can't lengthen it again!)...make small adjustments until you home in on the perfect bouyancy. Similarly, the craft will be more stable if the weight is below the center-line (ie the center of gravity is below the center of bouyancy). In order to turn, you want the two thrust motors to be as far apart as you can make them horizontally - but as close to the center of bouyancy as possible so it'll drive smoothly forwards and backwards without pitching up or down. SteveBaker (talk) 15:44, 2 November 2008 (UTC)[reply]
Mechanical Puzzle
This has been bugging me. Say we have two identical cylinders A and B, with their axes parallel and set up to spin freely. Then gear them together so that B always spins through three times the angle A does. Procure a long strip of stretchy material (rubber band or something) and attach one end to A. Wrap it around A repeatedly, keeping a bit of tension so it doesn't slip off, and when you get to the end stretch it out and attached the loose end to B. Now, spin B to wind the rubber band off of A. Once it's wrapped around B, it will be three times as stretched out as it was when it was wrapped around A. So, if you let go, will it unwind? If so, with how much force? Black Carrot (talk) 07:39, 1 November 2008 (UTC)[reply]
Yes, it'll unwind with the same force as it was wound up. Just put on wheels, a seat steering and brake and you've got yourself a green vehicle for when fuel prices go up again :) Dmcq (talk) 10:23, 1 November 2008 (UTC)[reply]
OK - I agree - it'll unwind with approximately the force you used to wind it up - minus the losses due to overcoming friction. We can't calculate the force because you didn't tell us the properties of the rubber or the frictional forces involved. But before we all get too excited, think about this: It would work better (as an energy storage device) if B span 10 times as fast as A...100 times as fast...INFINITELY FASTER. So A stays exactly still and B rotates freely. The 'A' end of the rubber is simply fixed in space and winds around B as required. Well, that's exactly what a clockwork motor does. To do get the best out of real rubber, you need to understand that the force required to stetch is gets drastically more as the rubber gets close to its breaking point. So as your device gives up its energy, it produces most of it all in a rush at the start - then kinda fizzles out. The fix for that is to make the cylinders taper so that they wind around the biggest diameter at the start - and then to progressively narrower parts of the cylinder. This makes it easier to wind the thing and to provide a nice even power output for a given input. SteveBaker (talk) 16:49, 1 November 2008 (UTC)[reply]
I'm going out on a limb here, but I'm pretty sure that doesn't make any sense. The point of this setup is that only a small section of the rubber band is being adjusted at any time, and the rest is sitting still. The friction of the band against itself and the band against the cylinders requires that. The part that is being adjusted is only stretched out a small amount, well within the tolerance of this material. It's very different from holding one of the cylinders fixed and removing the gears, and there should be no loss of speed near the end. Black Carrot (talk) 19:11, 1 November 2008 (UTC)[reply]
In my read of this, the band will just unwind itself. It appears that the band is wrapped around A just enough to hold it there. Then, it is wound around B until it is "off of A". So, it is no longer attached to A. It is just wound around B. You end up with one end touching B and most of the band wound tightly around B. There is a free end now dangling. Before you even let go of the contraption, the band should quickly unwind itself off B. -- kainaw™02:51, 2 November 2008 (UTC)[reply]
Well, you don't really need relativity to do that - good old Newton does just fine. The radius depends on the mass of the black hole - and a rough way to calculate it is the mass of the black hole divided by the mass of our sun multiplied by 3 (in kilometers). You can calculate it exactly: Use the mass to calculate escape velocity as a function of distance: v2=G.M/r and note that at the Schwarzschild radius, the escape velocity is the speed of light. So the radius is G.M/c2 (G is the universal gravitational constant). SteveBaker (talk) 16:27, 1 November 2008 (UTC)[reply]
You've missed out a 2. Newton's laws work even better if you get them right! ;) It's v2=2G.M/r and the Schwarzschild radius is 2GM/c2. --Tango (talk) 17:09, 1 November 2008 (UTC)[reply]
Update: Ah, here's what it says: Note that although the result is correct, general relativity must be used to properly derive the Schwarzschild radius. It is only a coincidence that Newtonian physics produces the same result.Mac Davis (talk) 00:44, 2 November 2008 (UTC)[reply]
Newtonian physics is an approximation that only holds under certain circumstances. Near a black hole isn't one of those circumstances, it just happens that the correction term is zero in this case by coincidence. An example of a very similar calculation where the coincidence doesn't work is when you look at orbits around a black hole. Using the same approach we could determine that the closest you can have a stable orbit around a black hole would be where the orbital velocity is the speed of light. Orbital velocity (for an object of negligible mass in a circular orbit) is , that would give a radius of , half the Schwarzschild radius (so you could have a stable orbit within the event horizon, but couldn't escape). General relativity, however, gives a last stable orbit a 1.5 times the Schwarzschild radius (I won't do the derivation here, mainly because it would take me too long to remember it), a completely different answer. So Newtonian physics gives the right answer to one question and the wrong answer to another very similar question - that's a pretty good reason to call the correct answer a coincidence. --Tango (talk) 01:43, 2 November 2008 (UTC)[reply]
I know that the Schwarzschild radius can be derived from Newton's laws and how, but my question is how in General Relativity!!!------The Successor of Physics 14:40, 3 November 2008 (UTC)
UK digital tv switchover
I have a friend who is keen to keep her old black-and-white television through the digital switchover as the licence is so much cheaper. Of course this tv doesn't have a scart socket, but apparently all she needs is a (Freeview) set-top box with an RF output rather than (or as well as) the usual scart. The official site lists several models of box that have this, but a couple of hours of searching brings up few on-line suppliers that have any of them in their catalogue, and none of those actually have any of those models in stock. Does anyone know for sure that these boxes are actually available? Or does anyone know of a gizmo that can convert the scart signal to RF for the aerial socket on the back of the television?--Shantavira|feed me14:05, 1 November 2008 (UTC)[reply]
One possibility is to find a VCR with a scart socket for input and an aerial socket for output.
It seems like all you need is a simple format adaptor for the jacks, these sort of gizmos are widely availible in the U.S. at Radio Shack stores, which are somewhat ubiquitous (its hard to find a strip mall built in the last 30 years withOUT a Radio Shack). Whatever the UK equivalent electronics store is will likely have sales people who may be able to match you up with the right equipment. It is likely a $5.00 adaptor will make it so that ANY digital converter box will make her TV work just fine... --Jayron32.talk.contribs15:50, 1 November 2008 (UTC)[reply]
Holy crap that is an awful piece of junk. this was designed by the French. No wonder the French designed it. How did this become industry standard? In the U.S., we have relatively simple-to-work-with AV connectors, including RCA connectors and Coaxial cable and the like. The different sorts of connectors generally interconvert with a simple adaptor. No wonder this is a problem in the U.K. Ugh... --Jayron32.talk.contribs16:55, 1 November 2008 (UTC)[reply]
Thanks, and yes, scart plugs are dreadful things. They have to be wiggled vigorously in and wiggled vigorously out. Anyway, I think the UK equivalent to Radio Shack is Maplin Electronics. I get lots of stuff there but I haven't been able to find a scart-RF converter there so I assumed they weren't possible. If anyone can show me a product code for such a thing I'd be grateful.--Shantavira|feed me18:05, 1 November 2008 (UTC)[reply]
What's truly impressive about the gargantuan SCART plug is that they are an absolute bitch to plug in - really tough to pull out - yet somehow they manage to spontaneously fall out without any provocation whatever. SteveBaker (talk) 18:15, 1 November 2008 (UTC)[reply]
Anyone who hates SCART will read this and think "Crickey! That's just the part of the iceberg above the water". They are truly a disgusting invention, I wish we could switch over to something else. —Cyclonenim (talk · contribs · email) 18:54, 1 November 2008 (UTC)[reply]
Scart isn't that bad really IMO, I find they rarely come out accidently and aren't that hard to connect and disconnect (certianly less hassle than the FIVE phono plugs two of which are often the same color that are needed for component video and audio). And it's simple for the user, one standard cable between thier TV and the peice of AV equipment and job done.
And yes you CAN get scart to RF converters (e.g. http://www.maplin.co.uk/module.aspx?moduleno=33050 ) but they aren't cheap (partly because just like a composite to RF adaptor for the US they need active electronics. partly because they are an item that few people need since AV equipment kept the RF outputs for many years after new TVs got scart inputs) it will almost certainly be cheaper and easier to get a freeview box with RF output built in (such as one of those linked on that freeview.co.uk page the guy above mentioned).
From my U.S. perspective, the problem with SCART seems to be that its using a sledgehammer to do a Ball-peen hammer job. I mean, what is the need for a 21-pin connector for AV equipment. In the U.S., surround-sound, High def home theaters are run using 5 cables: 1 video and 4 audio channels, and RCA or RF cables work fine for these applications. Even more modern standards, like S-video use at most 9 pins for 2-way video communication. Seriously, whoever decided that was a good idea needs to be given a good stern talking to... --Jayron32.talk.contribs00:52, 2 November 2008 (UTC)[reply]
S-video isn't that great is it? It's only Y/C. SCART supports RGB while admitedly YPbPr is now becoming more popular, I presume it seemed a fine idea at the time. And none of those provide data signalling. Personally I've never used SCART other then with adapters (I've had devices with SCART output but no SCART TVs) but it seems fine to me, provided all devices have them. Definitely simpler then 3 cables for video which is needed for component/RGB in most other cases + at least 1 audio for mono direction (x2 if you want bi directional=8 cables). Incidentally my experience with adapters is similar to anon. They aren't that hard to plug in. They aren't that secure either mind you but then again, nor is svideo and at least the pins are a lot more difficult to damage (unlike svideo) Nil Einne (talk) 07:59, 2 November 2008 (UTC)[reply]
But that's half the problem - SOME SCART devices support RGB - some support component - but some don't - and a few support both standards on the same connections with switches or menu options to configure them - so when you connect two gizmo's together, you have no clue whether it'll work - and no clue what form of video they'll be exchanging if they DO work. The cables themselves often leave out conductors in an effort to make them more flexible - resulting in cables that don't work when you connect them between devices that (against all odds) would have worked had all of the necessary wires been there. Separate cables at least let you SEE what's connected to what. A 21 wire connection might just about be bearable ordinarily - but because these are analog video signals, they have to be coaxially shielded - resulting in either monsterously thick cables - or cables that invite noisy connections - or cables with missing conductors. But my main complaint is the sheer mechanical ineptitude of the design and the overall chunkiness of the thing. Try fitting a SCART plug onto the side of a sexxy slimline laptop! When I lived in the UK, I used to need to push my TV up against the wall to save space - but the scart plug itself is over an inch deep - it has a stiff strain relief behind that - which adds another inch - and the cable itself needs about a 3" arc to bend through 90 degrees - so my TV has to be SIX INCHES from the wall! Compare to my US TV which has a recessed panel with the connections on it and the thin cables and short connectors are such that the TV can go right back against the wall with no gap at all. I dare not think of the ugliness of a flat panel TV with SCART connections! SteveBaker (talk) 15:26, 2 November 2008 (UTC)[reply]
According to the SCART article, the vast majority of modern devices do support RGB. Some also support component (but since it was a later addition it's not required nor should be expected). I don't know whether talking about laptops or flat panel TVs is fair, after all, these things were invented in the 1977 (and was the first standard evidentally). It's not as if 25 pin serial or parallel connectors are fun and they are new (I think) then SCART. If you want to argue that SCART is outdated and should die, I would agree, but then I don't find that S-video + audio or three component + 2 audio x 2 (okay that isn't quite fair since RGB isn't bidirectional) for is great either. Ultimately everything is moving to digital, or should provided the studios don't go too nuts about copy protection so all of these nasty cables will die but I personally having used them all to some extent don't find either of them that great, they each have their advantages and disadvantages. I think a lot of people do find SCART a lot easier then the large multitude of cables you otherwise need despite the other issues that can arise. Perhaps alternatives would have been better but I suspect until recently definitely, the advantages were probably minimal to not make it worth such a confusing switch. Even now, it seems most don't consider it worth it [7]Nil Einne (talk) 14:38, 3 November 2008 (UTC) Nil Einne (talk) 14:19, 3 November 2008 (UTC)[reply]
Frankly, at this point, 10GHz Ethernet would be a great standard...in fact, I'd like everything to support that - my toaster, my MP3 player, my doorbell - and TV, radio, etc...everything. SteveBaker (talk) 19:19, 3 November 2008 (UTC)[reply]
Glaciation during an ice age - source of the ice?
Hi. I'm wondering, during a glacial period, where does the ice actually come from? This seems like an obvious question, but right now I have two opposing ideas, and I could not find information on Wikipedia or the Internet. When an ice age begins, is the expansion of the glaciers caused by extra snow piling over time after being evaporated from the ocean? Or, could some of the ice be frozen from the surface of the ocean, increasing ice mass near the shore and reducing sea level? Or, is it a combination of both? It seems that nowadays, glaciers retreat because of warmth and sublimation, and they grow because of extra snow deposited on it. However, for the glaciers to grow quickly, the snow would need very high evaporation rates from the ocean, but isn't that supposed to happen during warm periods, not cold ones? I know Snowball Earth was supposed to have been started when extra rain washing the carbon dioxide out of the atmosphere (could that happen in a globally-warmed world?), but Pleistocene ice ages are supposed to be started by cold weather from Milakovich cycles, not rain washing the CO2 away? If the freezing of the ocean adding to the ice pack as a negative feedback occured, does that mean the ice pack could have left some brackish water behind while it melted, buried in the deepest regions of the Great Lakes? What is the current scientific view on where the ice came from? Thanks. ~AH1(TCU)17:05, 1 November 2008 (UTC)[reply]
Take a look at the glacier article. Definitely formed from snow under high pressure. Sea-ice is different, it is much thinner than glaciers and is saline, unlike glacial ice which produces fresh water. SpinningSpark18:30, 1 November 2008 (UTC)[reply]
Actually, sea ice is mostly fresh too. When water freezes, the ice crystals don't have space for salt molecules, so the salt stays behind in the increasingly salty liquid phase. If freezing is fast it is possible for the salt to be trapped in the frozen ice, as pockets of brine surrounded by freshwater ice. Over time, though, if subjected to thermal cycling or pressure (say from a thick layer of ice) the brine pockets merge and eventually are expelled from the ice. The increase in salinity due to brine rejection from freezing ice is one of the driving forces behind the thermohaline circulation (see also polar ice packs for more info). -- 128.104.112.72 (talk) 19:43, 1 November 2008 (UTC)[reply]
Type of ammunition ?
I found an old rifle shell (the bullet had been fired). The bottom is stamped "1907" and it appears generally identical to an 8 mm Mauser shell except for one unusual feature. Unlike an ordinary rifle shell that necks down once (where the bullet is joined to the shell), this shell necks down twice and appears to be made to be joined to a bullet 4 mm in diameter. The shell was found in an area where the French and German armies squared off during World War II, and a couple of 1930-s era 8 mm Mauser shells were nearby. Anybody know what kind of ammunition this might be ? --91.32.103.137 (talk) 18:40, 1 November 2008 (UTC)[reply]
A bit similar, but the second "neck" on the shell I have is 15 mm long. I wondered if it is some kind of a blank round but from what I can find the Germans were using crimped blank rounds, at least in World War II. —Preceding unsigned comment added by 91.32.105.90 (talk) 11:02, 2 November 2008 (UTC)[reply]
My Chemistry teacher is having my class make potential elements and describe their properties. Most of the properties should be based on the typical behavior in the group we put them in-the group I've chosen is the Noble Gases. My question: how many elements would be in the currently non-existent periods 8 and up? Is it 18 or 32? I'm mainly confused over whether such periods would have a collection similar to the Lanthanides and the Actinides.71.34.48.41 (talk) 19:58, 1 November 2008 (UTC)[reply]
There are some embedded assumptions about the filling order of f and g shells that we really have no way to test. So the placement of superactinides and the like on those extended charts may not really reflect their chemistry. Of course on the other hand, if those atoms can be created at all they are probably are so unstable that they would never have any demonstrable chemistry anyway. Dragons flight (talk) 23:20, 1 November 2008 (UTC)[reply]
On the other hand, there are some hypothesis that some huge elements (the atomic number 132 sticks in my head for some reason) may become significantly more stable than their lighter counterparts, having half-lives that may make it possible to do some real chemistry with them. However, for the purpose of this educational activity, being scrupulously correct is probably not all that important. The idea is to gain a fuller understanding for the importance behind the organization of the period table in order to predict "hypothetical" undiscovered elements, much in the way that Mendeleev used his table to predict the properties of the as-yet-undiscovered elements such as Gallium and Germanium. Sometimes, the importance of teaching this lesson requires that we fudge the real facts, especially at the high school level. See Mendeleev's predicted elements for more info on this... --Jayron32.talk.contribs00:44, 2 November 2008 (UTC)[reply]
According to this article from Nature, the average velocity of the 1s electron is (Z/137)*c. This to me implies that while it may be possible to create a stable nucleus of high atomic weight, it's not possible to have an actual atom (i.e. populated electron shells) above Z=136. Also, as that point is approached, relativistic contraction of the orbital sizes (and possibly relativistic increase in mass?) would radically alter the chemistry, so assuming that properties will remain similar as you go down the column of the periodic table might not be safe. Franamax (talk) 08:14, 2 November 2008 (UTC)[reply]
I haven't read the article, but is that formula actually expected to hold for heavy atoms? Isn't it more likely that a derivation including relativity (which is easier said than done) would just result in a different formula (which reduces to that one in the non-relativistic case)? --Tango (talk) 13:42, 2 November 2008 (UTC)[reply]
Well gee, the paper is titled Relativistic effects in homogeneous gold catalysis, so you'd think they may have used relativistic physics, wouldn't you? The box where "Relativistic effects" is explained has "In 1928 Dirac developed a new equation..." and goes on to use that equation. The example they use is Hg, where the 1s electron is at 58% of c. I can send a copy of the paper, drop me an email. Franamax (talk) 20:50, 2 November 2008 (UTC)[reply]
Alright, thanks. I could also use help with finding a basic chemical property that a noble gas might have, but I know that's pushing the "We don't do your homework" policy. 71.34.48.41 (talk) 18:15, 2 November 2008 (UTC)[reply]
Why aren't there better batteries for portable devices?
How far away are we from having really good, long-lasting batteries for our cell phones, iPods, laptops, etc? Batteries that will last through--I don't know--maybe a day, two days or a week of continuous use. Has there been any progress in this area?--69.114.164.38 (talk) 21:41, 1 November 2008 (UTC)[reply]
I think we are quite along way form that. Recently memory as decreased in size and cost, unfortunately this is not possible for batteries. Batteries use a chemical reaction to work; trying to improve this is extremely hard.
Inductive charging allows for an electronic device to be charging with out an electronic connection - the electronic device just has to sit on the charger. This will probably be integrated into tables so your battery will be charging when you’re using you laptop or other electronic device.
Although I say it is hard to improve batteries, there have been great developments for batteries. We don't notice these improvements because we are taking more and more power from the batteries, for example a laptop 5 years ago might have had a 2 hour battery-life, now a new laptop might also have a 2 hour battery-life but now it has to run many more power-intensive programs, WiFi, bluetooth etc.
W.i.k.i.p.e.d.i.a - Reference desk guy (talk) 22:00, 1 November 2008 (UTC)[reply]
We do keep hearing of batteries that can be formed like plastics, so the casing of the unit could also be its power supply. But these keep not appearing in commercial products, so seem to be yet another futurologists' pipedream. —Preceding unsigned comment added by DewiMorgan (talk • contribs) 02:58, 2 November 2008 (UTC)[reply]
Indeed a simple mobile phone has an excellent battery life (particularly standby), and some people prefer them. For those of us who do like (and use) a colour screen, data connection, camera, music etc of course it's not going to last that long. 1 or more days of continous use is a bit unresonable though we're not talking about Moore's law here, I don't think it's likely battery capacity doubles every 18 months Nil Einne (talk) 08:14, 2 November 2008 (UTC)[reply]
I remember reading an article within the last year or so about some new form of batter that would last years. Unfortunately, that's all I can remember. 67.184.14.87 (talk) 10:39, 2 November 2008 (UTC)[reply]
I very much doubt that's always the case. I'm not even sure it's often the case - why do you ask? What makes you think that's the case? --Tango (talk) 22:11, 1 November 2008 (UTC)[reply]
Body temperature varies during the day, in a regular pattern, both in healthy humans and in humans suffering from a viral infection. Temperature usually goes up in the afternoon, but not at night. Fever article has some information. --Dr Dima (talk) 23:16, 1 November 2008 (UTC)[reply]
Well,the reason I asked is that I have a flu and during the day I always have life 37.2 or something on those measures, but at night it usually goes up to 38.5. —Preceding unsigned comment added by 87.116.154.181 (talk) 23:41, 1 November 2008 (UTC)[reply]
Are you taking paracetamol or anything similar? If so, that ought to lower your fever, in which case when you take the drugs will affect when your fever is at its worst. If you take the drugs as soon as you get up and then regularly during the day, but don't take any at night, that would probably explain what you're seeing. Of course, if the unexplained changes in body temperature persist, you should seek professional medical advice - it could be indicative of something serious (I don't know of any such things, but I haven't spent 6 years in med school, so I can't say for certain that it isn't something serious). --Tango (talk) 23:45, 1 November 2008 (UTC)[reply]
Well, it's simply not true that when you have influenza "body temperature always goes up during the night and you feel worse then during the day": that's the way you're experiencing, but when the diurnal variation of the symptoms of influenza were studied, it was found that 'the average temperature increased during this illness and ... nasal secretion and the temperature increase were greatest in the early morning'. I suppose this might be interpreted as the temperature "going up" during the night. Part of the reason for differences might be that your normal diurnal variation may be different from other peoples. But most people, apparently, have the greatest temperature and worst symptoms in the morning. [9] - Nunh-huh01:56, 2 November 2008 (UTC)[reply]
your nervous syztem winds down the sympathetic system and fires up the parasympathetic system at night, as you go into rest mode and out of active mode. as a result, your attention is shifted to your internal stimuli, rather than external stimuli in the world. sick people tend to feel more miserable at night. Gzuckier (talk) 16:55, 3 November 2008 (UTC)[reply]
Using cat litter to defuse potency of medicines/pills
Recently, going through my now deceased great aunt's things, her daughter had to dispose of the numerous medicines she was on. (She had cancer if this helps.) She bought cat littler, and put the pills in the cat litter to remove their potency.
I'd never heard of this before. My questions: 1. Why does this work? From reading the article about what it does to the feces, I gather there's some sort of chemical reaction, but am not sure what. And, 2. Is this something that can be done with any medicine? Or just the anti-cancer stuff? Would it work on every kind of drug; could the police place illegal drugs in kitty littlr before disposing of it once it's been used as evidence? (now that I think about it, I would guess they do; they have to do something to it.)Somebody or his brother (talk) 22:30, 1 November 2008 (UTC)[reply]
Cat litter should have negligible impact on most dry, solid medications. Cat litter is sometimes recommended as a way to process liquid medications though. This has more to do with turning the liquids into an unpalatable solid than with actually breaking down the medication. Dragons flight (talk) 23:10, 1 November 2008 (UTC)[reply]
Indeed, pharmacies must have procedures on hand to dispose of expired medications; they would probably add your great aunts pills to the next batch that goes out. I would really recommend that you do that. Attempting to dispose of these on your own is dangerous, and homespun methods of "reducing their potency" seem like a bad idea as well... --Jayron32.talk.contribs00:37, 2 November 2008 (UTC)[reply]
The US Office of National Drug Control Policy recommends: "Mixing prescription drugs with an undesirable substance, such as used coffee grounds or kitty litter, and putting them in impermeable, non-descript containers, such as empty cans or sealable bags, will further ensure the drugs are not diverted." [10] I think that should be read as "such as used ... kitty litter" - the kitty litter isn't there to do anything to the drugs, it's there to make them unappealing enough to discourage junkies from snagging discarded drugs from the trash and abusing them. Slightly nutty and paranoid, sure, but that's drug control policies these days. -- 128.104.112.72 (talk) 01:11, 2 November 2008 (UTC)[reply]
If memory serves, the official advice in the UK is to take all expired or unneeded drugs to a pharmacy to be disposed of. That page seems to suggest that some pharmacies in the US won't take them. The UK system seems better to me - far simpler (a list of drugs that need to be flushed down the toilet is far too confusing for anyone to actually follow it). --Tango (talk) 01:48, 2 November 2008 (UTC)[reply]
If you let people flush them down the toilet, some news idiot with a need for a story will get someone to do an analysis of the water. Then, they'll find something like 1 part per trillion of Prozac in the water and the next morning's headline will be "City Water is Full of Prescription Drugs including Prozac!" -- kainaw™02:33, 2 November 2008 (UTC)[reply]
Actually drugs flushed down toilets appears to be a genuine concern [11]. Also this version of the guidelines 128 mentioned don't say anything about junkies. They talk about pets and children. This one does however [12]. In any case, I agree with Tango. I don't know why the US doesn't just follow what's done in the UK, NZ, Australia [13][14], and large parts of Canada [15] and get pharmacies to deal with expired drugs. (IIRC, last time this came up the consensus was few pharmcies in the US would deal with expired medication and from Googling this appears to be the case) Nil Einne (talk) 07:45, 2 November 2008 (UTC)[reply]
Just speculating, but it may have something to do with the way the DEA tracks scheduled (controlled) drugs. If they expect a "chain of custody" and a full account of all drugs received or distributed, having "stuff somebody brought in" would create discrepancies in the records. For things that don't have addict issues, it's probably set at a state level by a board of pharmacy how they keep track of things. Some references that might be interesting: [ONDCP's recommendations], [rules for a state (Oregon) board of pharmacy]. Just from the standpoint of process control, bringing the medications back into the pharmacy creates a burden of making sure that they don't get mixed up with prescriptions to be issued. Creating opportunities for medication errors is considered harmful. SDY (talk) 10:02, 2 November 2008 (UTC)[reply]
Surely a pharmcy has to keep good track of their medications anyway don't they? It's not as if they have all their medication in one big tin and choose whatever looks good (at least I hope it's not). So it seems to me it doesn't make that much more problem. After all, giving someone warfarin instead of vitamin K tablets is already serious enough. Even if you're talking about the same drugs, I presume pharmcies still often have to keep track of probably more then one quantity of the drug with different expiry dates. In other words, it may add a small risk and yes that risk may be catatrophic, but surely it's only minute unless the pharmcy already has shit systems anyway in which case you have other things to worry about. Drug control wise, sure it does add another element to deal with but are dodgy pharmcies really such a problem in the US. Here the greater concern is with people robbing pharmacies from what I can tell. Nil Einne (talk) 15:01, 3 November 2008 (UTC)[reply]
If you believe that junkie won't consume drugs because they have to weed through cat poop and piss to get them, well, you are sorely mistaken. Drug adicts often do far worse to get a "fix" and, for the kind of person who will hunt through the landfill to get drugs, a little shit and piss is not going to stop them... --Jayron32.talk.contribs02:41, 2 November 2008 (UTC)[reply]
Try our article titled Carboniferous period which contains lots of good information. The first reference at the bottom of the article is a link to a journal article titled "Atmospheric Oxygen, Giant Paleozoic Insects and the Evolution of Aerial Locomotor Performance." You could follow that link, or any of the other references, should our article not contain the information you are seeking. As an alternate source, may I suggest that you look in the textbook that your teacher gave you at the start of the class, or perhaps you could review the notes you wrote down the day that your teacher discussed this in class. Cheers! --Jayron32.talk.contribs00:35, 2 November 2008 (UTC)[reply]
The question is then: What caused the low oxygen content of the current atmosphere? Who burnt so much coal and where is the resulting CO2 (presumably in carbonates)? Maybe subduction and vulcanism (how does coal react in the asthenosphere?). Icek (talk) 14:06, 2 November 2008 (UTC)[reply]
Coal has only been burnt in significant quantities since the industrial revolution, I doubt that's had any noticeable effect on oxygen levels. My guess would be simply an increase in animal life (with the resulting CO2 being dissolved in oceans, stored in carbonates, fossilised, etc.). --Tango (talk) 16:06, 2 November 2008 (UTC)[reply]
No, large-scale burning of coal probably happened in the Permian and many people now think the PETM was coal related as well. Coal can be ignited in situ by volcanism, or where it intersects the surface by wildfires/lightning. Even today, underground coal fires probably represent a few percent or carbon emission, and some coal fires, like Australia's Burning Mountain, have persisted for thousands of years. Though biological processes for dealing with lignin were surely necessary, much of the fall of atmospheric oxygen is thought to be connected to the erosion and oxidation (either by burning or by microbial consumption) of Carboniferous organic deposits during the Permian. Lower sea levels (drying out swampy areas and exposing recently buried organics) and higher volcanism in the Permian helped make that possible.
Oh, and yes scientists do measure the small decline in atmospheric oxygen (ususally expressed as the O2/N2 ratio) since the onset of the anthropogenic burning of fossil carbon. Since the atmosphere is 20% oxygen, the loss of a fraction of 1% isn't a big deal so far. Dragons flight (talk) 16:59, 2 November 2008 (UTC)[reply]
There was natural burning of coal, yes. Since the question was "who" I assumed it was just asking about human burning. --Tango (talk) 18:33, 2 November 2008 (UTC)[reply]
That wasn't the question, though. The question was what caused the high oxygen content during that time period. I think a fair interpretation of that question is "Why were the oxygen levels higher then than they are now?" --Tango (talk) 16:59, 3 November 2008 (UTC)[reply]
Just to clarify: I am pursuing this for my own interests, and my question is "Why was there more oxygen during the carboniferous than now?" —Preceding unsigned comment added by 24.77.21.240 (talk) 02:50, 4 November 2008 (UTC)[reply]
Geography buffs needed...
<removed> This is not a question. The reference desk does not appreciate being spammed with advertising - even if you're advertising a Wikipedia project. SteveBaker (talk) 15:01, 2 November 2008 (UTC)[reply]
Lovebirds and loneliness
Whilst it's a total myth that Lovebirds will wither and die if kept alone, I was wondering if long-term isolation in these birds is any more psychologically damaging than it is for other species, considering the extremely close social bonds they form and their super-affectionate natures. Anyone know? I'm just thinking about a particular male Peach-faced Lovebird that lives alone in a 30m x 30m aviary at a bird collection near where I live (actually, he *is* the bird collection at present!). --Kurt Shaped Box (talk) 01:44, 2 November 2008 (UTC)[reply]
Actually, most animals, if kept alone and unsocialized, general develop serious psychological problems, often referred to as Stereotypy. The sort of things where you see caged birds plucking all their feather's out, or bears in a zoo repeatedly pacing a small path despite having a large enclosure, are usually the result of the psychological damage done to social animals when they are kept in isolation for extended periods of time. --Jayron32.talk.contribs02:35, 2 November 2008 (UTC)[reply]
Yeah, I'm (mostly) aware of all the above. I was wondering if Lovebirds specifically were any more susceptible to these problems, given that their entire raison d'être seems to be to stand as close as physically possible to other Lovebirds and snuggle. --Kurt Shaped Box (talk) 21:51, 2 November 2008 (UTC)[reply]
Well, if intervention is required, Christmas is coming up and you might like to give it a present/expand the collection. Maybe it would simply enjoy company in the form of other types of birds instead of rattling around in 302 metres by itself. Is there foliage/rocks, landscaping there as well? Give out a few hints perhaps, in the interest of plumage preservation at least... Julia Rossi (talk) 22:40, 2 November 2008 (UTC)[reply]
Yep, I was actually considering making a donation to enable them to buy some more lovebirds. They used to have loads of them in that enclosure but a combination of financial problems, disease, a lack of hens and the passage of time has significantly reduced the numbers. They've only got three Cockatiels now, in a (different) aviary built for 30 or more (their Zebra Finches are breeding like Zebra Finches, however).
FWIW, the Lovebird looks okay physically and seemed quite content to fly around and swing/gnaw on branches (the aviary has several trees and shrubs within). He comes to the bars and tweets whenever anyone approaches, so I guess that he's feeling somewhat lonely... --Kurt Shaped Box (talk) 22:58, 2 November 2008 (UTC)[reply]
Birds often interact with a mirror in thae cage. If they were humans, they might spend hours editing Wikipedia for a simulation of human interaction. Edison (talk) 03:50, 3 November 2008 (UTC)[reply]
According to PH#Explanation, it is possible to have a substance with a pH greater than 14 (or less than 0), it's just unusual. There is nothing in the definition that creates an absolute maximum at 14. --Tango (talk) 02:12, 2 November 2008 (UTC)[reply]
Lots of solutions, not all that unusual, have pH's larger than 14 or less than 0. Also, it should be noted that substances can't have a pH, since pH is only measureable as a function of how the substance acts while in a water solution. pH is something which is a function of both of the substance and the concentration of that substance in water. I can, for example, create a solution of Acetic acid which has a lower pH (and this is more acidic) than a solution of Hydrochloric acid, even though acetic acid is a weaker acid than is hydrochloric (it has a higher pKa, or acid dissociation constant, than does hydrochloric).
Nope, pKa is the negative logarithm of the Ka. Thus acids with lower Ka's produce MORE hydronium ions in solution, and thus are more acidic. Lower pKa = higher Ka = more acidic... pKa is often more convenient to work with than Ka because it is then on the same logarithmic scale as is pH... --Jayron32.talk.contribs18:21, 2 November 2008 (UTC)[reply]
If there are many different gases in earths atmosphere why do they not seperate? Sediments seperate over time but gases don't seem to. Oxygen is heavier that nitrogen so why should it be mixed? —Preceding unsigned comment added by 202.154.155.124 (talk) 06:42, 2 November 2008 (UTC)[reply]
Perhaps it is due to air currents and air turbulence. Air currents are caused by air temperature differences that result from the sun striking the earth more obliquely toward the poles. Near the equator the warm air rises and returns toward the poles at a high altitude. This has a mixing effect for the gases. Also, mountains, hills, trees, and friction with the ground, all create air turbulence near the ground. Uneven heating of the air over land, sea, desert,and vegetation, also enters into it, causing air currents and mixing. As for sediment, the sedimentary particles have a greater specific gravity than water, resulting in their tendency to settle on the bottom. However, turbulence in rivers causes muddy waters all along the river's course. When the relatively still sea is reached, the particles may settle to create a delta. If there is no delta at the mouth of a muddy river, it is because coastal currents sweep the sediment away. —Preceding unsigned comment added by 98.17.34.3 (talk) 13:59, 2 November 2008 (UTC)[reply]
Gases diffuse into each other readily (technically each one effuses), which leads to mixing even if there weren't externally-driven air currents, because all molecules are always in a state of motion. Actually *all* things do this, but Graham's law explains that lighter particles do so more rapidly. Remember that gases move as individual molecules instead of solids (large aggregates of molecules). Once mixed, there is usually some intermolecular attraction that helps keep them mixed and mixing is favored by the increased entropy. Some mixtures of gases do separate, but it requires that they have a relatively large difference in molecular mass and do not have much if any intermolecular attraction. DMacks (talk) 18:32, 2 November 2008 (UTC)[reply]
For all practical purposes, diffusion is irrelevant to the atmosphere. Atmospheric mixing is totally dominated by wind and turbulence, which is also the reason that the atmosphere stays mixed. Dragons flight (talk) 18:44, 2 November 2008 (UTC)[reply]
So if you take a bit of air and put it in a special container, shielding fully from any turbulence (a kind of perfect container on earth at 1G with no movement in the ground, and fully sealed), will it seperate in layers of different gases after a long period? If yes, do we know how long? --Lgriot (talk) 01:26, 3 November 2008 (UTC)[reply]
For containers of practical sizes and gases at room temperature, there will be a small partial separation: i.e. a little more of the heavy gases at the bottom and little more of the light gases at the top. The diffusion time scale in absolutely still air will be , where l is the characteristic length of the system. After a few times the diffusion time scale one would expect the air to have separated to the degree it is able, but it would not be a big effect. Plugging in large length scales will show how diffusion is so much slower than wind and turbulence when it comes to rearranging air. Dragons flight (talk) 01:48, 3 November 2008 (UTC)[reply]
What is the "characteristic length of the system"? Sorry I am only a curious layman ... Would that be the height in most containers (say a cylinder standing upright)? Also would l be expressed in centimetres like the volume? BTW, I had assumed s is a number of seconds, but now it seems it doesn't make sense, since the number of seconds is what we are trying to find out, so it can't be on the right of the formula. --Lgriot (talk) 00:30, 4 November 2008 (UTC)[reply]
The cm and s in that formula are "centimeter" and "second", not some count of them. l is the original length over which the gases are mixed and can be expressed in whatever units you like, but you have to divide by the units. I personally find it confusing to make the units be part of using the formula rather than part of writing it, but if it helps you can read that formula as "the number of seconds in the characteristic time of stratification is 5 times the square of the number of centimeters long the system is". --Tardis (talk) 03:20, 4 November 2008 (UTC)[reply]
Stops people from hanging around talking to you for too long. Freshens up the armpits. (And makes things de-licious) Ooh, ooh, roast and put on toast! Franamax (talk) 08:22, 3 November 2008 (UTC)[reply]
I am studying a scientific degree at the moment but I also have a keen interest in Association Football. Are there any sources of information I can use to find scientific studies of association football, like pubmed for medicine? I am particularly looking for statistical evidences and scientific tactical analyses, or anything like this. Donek (talk) 14:39, 2 November 2008 (UTC)[reply]
Efficacy of multi-sensory room.
I wanted to ask if there are any studies about the effect of these very expensive rooms on children with special needs especially those that approach the vegetable side. My gut feeling about it is that it is an expensive those of hope for the parents but I would like to educate my opinion if possible, thanks.Bastard Soap (talk) 17:02, 2 November 2008 (UTC)[reply]
Discovering intelligent extraterrestrial life
I recall reading somewhere that based off an estimation of the Drake equation and the amount of signals analyzed by SETI, there was a year by which we could hypothetically discover intelligent extraterrestrial life. Does anybody have this figure? Thanks in advance.
QWERTY | Dvorak17:22, 2 November 2008 (UTC)[reply]
Estimates of the parameters for the Drake equation vary enormously, so any such time estimate is going to be very approximate (and it's just a statistical expectation, not an actual prediction). --Tango (talk) 18:42, 2 November 2008 (UTC)[reply]
In principle - that ought to be a prediction we could make. The Drake equation(s) (there are several variations on the original idea) are a correct statement of how many alien civilisations ought to be 'out there'. All of the variations basically involve multiplying together between half a dozen and a dozen numbers. The trouble it that most of those numbers have HUGE error bars on them. When you multiply numbers with doubt associated with them - the amount of doubt goes up rapidly. Our article points out that any answer between 0.05 and 5,000 civilisations per galaxy is reasonable given 'educated guesses' for the values of the terms that we don't know.
There are terms in the Drake equation like "The number of years between a civilisation starting to broadcast messages to the stars and it's eventual downfall". We have no clue what that number is. Humans are not really capable of broadcasting that far - so the value for that term in the equation might be anywhere between zero and a hundred million years and we have no way to get a more accurate estimate. Since so many of the terms in the Drake equation are as hard to pin down as that one, any use of the resulting number to predict how long SETI might take is similarly vague.
Worst still, (as it's always worth-while pointing out), if you took the most powerful radio transmitter mankind has ever built and put it on the star that's nearest to our sun - SETI's equipment would not be sensitive enough to detect it. The nearest star is only 4 light years away - and radio waves get weaker as a function of the square of the distance. So if there were (say) just a couple of other civilisations in our 100,000 light-years-wide galaxy, then they could easily be 40,000 light years away - using transmitters like ours and producing a signal 100 million times weaker than SETI can detect! So it's perfectly possible that SETI simply isn't sensitive enough to pick up any of the messages that 5,000 alien species are screaming at us every day and from every direction in the sky!
It's also possible that we're somehow searching in the wrong manner. If the aliens habitually use 'spread-spectrum' radio techniques - or communicate with lasers rather than radio waves - then the radio-based SETI search will never find them.
There's no way to get any sort of accurate estimate since we have no idea how common life is, let alone intelligent life. The only thing we can for certain is that in our own solor system, there is only one planet with intelligent life. I'm not sure if it's fair to count Earth because if we didn't exist, we wouldn't even be here to ask the question. Once you exclude Earth, the number of known intelligent civilizations is zero, which puts the result of the Drake equation at zero. We may very well be alone in the universe. 67.184.14.87 (talk) 23:01, 2 November 2008 (UTC)[reply]
I think it's FAR too soon to assert that we are the only intelligent species in the solar system. There is plenty of scope for creatures living in the deep oceans under the ice of Europa - or on Titan. The only thing we know for sure is that if they ARE intelligent, they either cannot or choose not to transmit powerful, distinct radio signals at us and they do not build huge, visible cities. If a civilisation of water-dwelling creatures lived on Europa, they would be unable to see the sky or the stars because of tens of kilometers of ice over their heads. They would perhaps not have invented telescopes - never have realised that there is anything above the ice - and certainly never have tried to transmit message through it. That doesn't mean they couldn't be intelligent and have a rich and interesting society.
That's the problem with the Drake equation - we don't know the very first thing about what is or is not possible in terms of life...let alone intelligent life...let alone intelligent life with big-assed radio transmitters and a curiosity about life elsewhere. SteveBaker (talk) 19:15, 3 November 2008 (UTC)[reply]
I'm not sure about "sound" but every other fluid that comes to mind is more viscous at lower temperatures. You could try the Viscosity article, but it is simply an atrocious violation of WP:MTAA. SDY (talk) 20:32, 2 November 2008 (UTC)[reply]
Well, there's a reason I put "viscous" in scare quotes. I'm not saying it is necessarily actually more viscous by the scientific definition, just that when you pour just-boiled water from a tea kettle into a teacup, the sound the water makes is somehow "thicker" than if you pour cold water in. —Angr21:10, 2 November 2008 (UTC)[reply]
I guess so, yeah. I'm sorry I'm not being very scientific about my description; I was hoping this was such a well-known phenomenon everyone else would know what I was talking about. Am I the only person here who has noticed for his entire life that very hot water sounds different when it pours than cold water? —Angr21:58, 2 November 2008 (UTC)[reply]
Pouring very hot water into a container brings the liquid into contact with a (microscopically) rough surface, encouraging the formation of bubbles of water vapour. The formation and rapid collapse of these bubbles probably alters the sound. (I'm not sure that density differences in the liquid could account for the change in sound; water is only about 3% less dense at 95°C than at 4°C.) TenOfAllTrades(talk) 23:31, 2 November 2008 (UTC)[reply]
This thought actually occurred to me the other day and with a bit of Googling I found out that water is actually less viscous at higher temperatures, so the sound it makes is different. One source claimed the viscosity fell of particularly quickly close to boiling point, but our Viscosity article seems to suggest a linear relationship. Either way, my understanding is that it's this decrease in viscosity that results in the difference in sound between pouring hot water and pouring cold water. Maelin (Talk | Contribs) 01:49, 3 November 2008 (UTC)[reply]
Okay, then it's just my subjective impression that hot water sounds "thicker" even though actually it's less viscous. It makes sense that water that's about to become steam would be less viscous than water that's about to become ice. —Angr06:25, 3 November 2008 (UTC)[reply]
What type of AC motor is in the ZENN? Is it a wound rotor, squirrel cage, synchronous or switched reluctance motor? I believe the motor is made by Advanced Motor & Drives, p/n ACX-2043. --jcmaco (talk) 20:58, 2 November 2008 (UTC)[reply]
According to your link at environmentalmotors, it's a "3 Phase AC motor by Advanced Motors & Drives -- ACX 2043". That's an interesting method, since it's powered by a DC battery / ultracapacitor. I'm not sure why someone would build a 3-phase inverter into the powerline, rather than use a straight DC motor. We had a thread a little while ago here about why lawnmowers rectify single-phase AC to DC - and I wasn't all that clear on why they did that either. I made a small chase, because I had thought that AC motors developed more torque than DC, but my ship ran onto the rock of hard numbers. AM&D claims their designs to provide exceptional torque.
In any event, the AM&D website discusses their "standard AC motors" and various brush features. This sounds to me very much like a wound rotor. The site also prominently invites you to make direct contact, so that may be the best way to go.
The ZENN website may have info but I bailed out of it - someone decided that the best paradigm for web users used to clicking through pages was to introduce the concept of a "book" that you have to click-hold-drag the pages of, just so you could read their wonderful story, like Daddy used to tell you. OMG that's bad!
Is there a simple way to convert a phenol group to a phenyl bromide? For a general example, can toluene be converted to bromobenzene? For a more specific example, can p-hydroxyaniline be converted to p-bromoaniline? Somehow I think that it's not possible, especially with an NH2 group activating the benzene ring, but I was just wondering. --Russoc4 (talk) 21:54, 2 November 2008 (UTC)[reply]
Larock lists a dozen refs for "ArOH→ArX", all involving things that could be considered strong electrophiles/Lewis acids. Looks like lots involve transiently deriving the OH into a leaving group, not sure if they formally would go by addition–elimination or elimination–addition. Your question is kinda weird though…there's no phenol in toluene (did you mean "phenyl"?) and where did the methyl of toluene go in the bromobenzene you expect to get? But for the very specific case you mention, wonder if reduction to aniline then very simple p-selective electrophilic aromatic substitution to get the halogen? DMacks (talk) 02:06, 4 November 2008 (UTC)[reply]
Library scanner things
When entering or leaving the library, when I walk through those things that scan to see if you're stealing books, and I'm wearing my iPod, there is a sudden intense squealing in my ears. If I take the earphones out of my ears before passing through, then put them back in on the other side, I hear no such thing. What causes this? Is it in any way damaging to my iPod? Cherry Red Toenails (talk) 22:56, 2 November 2008 (UTC)[reply]
I'd be more worried about your ears then your iPod. If you did want to worry about some object that isn't part of you, I'd worry more about the earphones Nil Einne (talk) 11:27, 3 November 2008 (UTC)[reply]
I didn't ask about my ears for fear of bringing down the "NO MEDICAL ADVICE" vultures. =P I thought asking about the iPod might give me a clue though. And I figured it was some kind of electromagnetic thing, but wasn't sure what. The article you suggested helped though, thanks. Cherry Red Toenails (talk) 16:32, 3 November 2008 (UTC)[reply]
I don't think you need any medical advice beyond common sense - if the sound hurts your ears, take the earphones out before going through. If it doesn't hurt, then it probably isn't any worse than all the other loud noises you are exposed to on a regular basis, especially since it lasts a fraction of a second. --Tango (talk) 16:38, 3 November 2008 (UTC)[reply]
if it is that loud, i would worry about generating high voltage/currents in circuits such that the ipod isn't designed for, possibly frying something in the Ipod; but if it didn't actually fry it, then i'd stop worrying. Gzuckier (talk) 17:07, 3 November 2008 (UTC)[reply]
In case of a very high ferritin value (900+) for a long period of time (year+),not due to iron overload (ruled out by transferrin/iron), is there a list of possible diseases?
I understand high ferritin+ESR+CRP is a "nonspecific inflammation", but is there a protocol for treating this?
Mathityahu (talk) 00:34, 3 November 2008 (UTC)[reply]
I once read, while studying for my music degree, that there is a rare condition that precludes an individual from the ability to sing. I cannot recall the name of that condition and would like to know what it is so that I can research it and learn more. I believe, for the most part, that if you can talk you can sing and would like to research this "rare condition" further. My clouded memory gives me the word "amesia" for the, but I cannot find that word in Wikipedia or any other dictionary that I have checked, so assume it is probably
not the correct word. Does anyone know more? I have hit a dead end in my research on the web.Kschwacog (talk) 01:18, 3 November 2008 (UTC)[reply]
Note that amusia is an inability to mentally process music, not really a physical problem with the voice that precludes the ability to sing. Being monotone could be a result of amusia (the person can't hear notes, so doesn't produce them). It is also a result of lack of voice control - with many possible causes. A rather famous example is Julie Andrews. After throat surgery, she claimed to have lost the ability to sing. -- kainaw™03:09, 3 November 2008 (UTC)[reply]
I was half expecting that the one-word answer to "not being able to sing" would be "Franamax". In fact, I'd propose it as an alternate definition... Franamax (talk) 07:46, 3 November 2008 (UTC)[reply]
Franamax has raised the issue of someone who knowingly can't sing (taking you at your word here). Does an "amusia" type realise the problem, ie, can hear music but can't sing it? Hope you know what i mean. Sorry Kainaw, you got it and variations. Julia Rossi (talk) 10:32, 3 November 2008 (UTC)[reply]
Our article on Tone deafness notes, "Being tone deaf is having difficulty or being unable to correctly hear relative differences between notes; however, in common usage, it refers to a person's inability to reproduce them accurately. The latter inability is most often caused by lack of musical training or education and not actual tone deafness." In colloquial usage, the inability to reproduce musical tones is often called "tone deafness"; though this colloquial usage is generally unrelated to the real medical condition called amusia. --Jayron32.talk.contribs17:14, 3 November 2008 (UTC)[reply]
'Intensity' of dreams
Why is it that dreams are far more intense/realistic/emotional than real life? ie why can you experience far more pleasure/fear/happiness in dreams than in waking life?--GreenSpigot (talk) 02:26, 3 November 2008 (UTC)[reply]
(edcon)For some of us, it's the opposite though this[16] in the article says anxiety is a common feature of dreams. That could also depend on age and development, and personality. Julia Rossi (talk) 03:00, 3 November 2008 (UTC)[reply]
It is not a given or accepted conclusion that dreams are in fact more intense, realistic, or emotional than real life. In the rare cases when dreams are remembered in detail, they may be related to the day's actual experiences, as those experiences are related to previous experiences and desires. Edison (talk) 03:46, 3 November 2008 (UTC)[reply]
I haven't remembered a dream in quite a few years, and even the one I did remember then was quite prosaic and uninteresting. So I'd have to dispute your assumption, maybe for some they are bright and vivid but for others they aren't. Dmcq (talk) 13:03, 4 November 2008 (UTC)[reply]
cognitive power of a feline
a domesticated cat sees a kitchen counter. It knows to get on that counter it must jump. Once the cat is on the counter can it determine that BECAUSE it jumped it is on the counter? Thanks, 32.149.68.21 (talk) 03:16, 3 November 2008 (UTC)[reply]
My cat won't jump on the counter normally. However, if he smells ham, he jumps on the counter and eats the ham (until required to stop). I'm not able to say whether he KNOWS he is on the counter BECAUSE he knows he jumped or BECAUSE he knows he is now able to eat the ham. He certainly know that jumping on the counter is a prerequisite to eating ham. CBHA (talk) 04:28, 3 November 2008 (UTC)[reply]
The question is unanswerable, because we have no way to "see" into a cat's cognitive processes. What allows us to understand what Humans are thinking is that they can tell us. Language allows one to describe ones own thought processes. As yet, no cat has ever explained their behavior to us... --Jayron32.talk.contribs13:29, 3 November 2008 (UTC)[reply]
Oh, that's easy. "Wild" water that you find always tastes better than the domesticated water your human puts out for you. Every cat knows that. —Angr15:42, 3 November 2008 (UTC)[reply]
Seeing my black cat curled up on a black blanket, I wonder whether anyone has experimented to see whether cats are aware of their own color and the availability of camouflage, e.g. by letting black cats and white cats choose favorite spots in a room whose walls and floor are half white and half black. —Tamfang (talk) 17:15, 3 November 2008 (UTC)[reply]
That's strange. The cats I've had usually prefer spots where they are the least camouflaged, so that the hair they leave behind is maximally visible. In other words, black cats should prefer white sofas and rugs, and vice versa. —Angr18:42, 3 November 2008 (UTC)[reply]
Yes - but that's just their natural tendency to wish to modify their environment. Rolling around on a white rug while shedding fur is a sure way to convert the annoyingly contrasty rug into something that's a PERFECT match for one's own fur - and therefore a great place to be camoflaged. SteveBaker (talk) 18:58, 3 November 2008 (UTC)[reply]
Or it could be that they are "marking their territory" which would show a preference for non-camoflaged backgrounds... The better the contrast, the more their fur is likely to stand out, and announce to the world "This is my territory, and all the females you find here belong to ME". That could be a good genetic survival strategy in and of itself, no? --Jayron32.talk.contribs06:00, 4 November 2008 (UTC)[reply]
Do lizards lay eggs from which baby lizards hatch, or do lizards give birth to live babies, or do some approach the question of reproduction one way and some the other? CBHA (talk) 03:44, 3 November 2008 (UTC)[reply]
How many video game references can you find in the Arecibo message?
How many video game references can you find in the Arecibo message? In the middle, there's a blue and white guitar from Guitar Hero. Below that is the human in Berzerk. Finally, at the bottom is one of the space invaders. 67.184.14.87 (talk) 04:15, 3 November 2008 (UTC)[reply]
The red dude who has fallen into a hole in the white platform is from Lode Runner--that makes it only 10 years impossible to be what it actually represents instead of 30:)DMacks (talk) 05:35, 3 November 2008 (UTC)[reply]
I have been given an assignment. 8 point electrical charges are placed at the corners of a cube and another point electrical charge is placed at the centre of the sphere. I have to experimentally show that the 9th electric charge will not be in stable equilibrium. I have a theoretical explanation for that using Gauss's law. To do it experimentally, I thought I will use charged (conducting)spheres as point charges. I can charge a sphere using induction method. Is there any other way to charge a sphere?Please help. Also, suggest some ways to place the spheres at the corners of a cube. —Preceding unsigned comment added by 210.212.187.69 (talk) 04:28, 3 November 2008 (UTC)[reply]
without having the gumption to work on it, my instinct is to start with 1/rsquared being countered by the cosine of the angle between the middle point and the corner point and the middle point and the center of the side. i have no idea whether that will get you the right answer or even in the general direction of the right answer. Gzuckier (talk) 17:13, 3 November 2008 (UTC)[reply]
Ahh, you're talking about electrical charges. When the original question opened with setting charges at the corners of a cube, I thought y'all were trying to blast your way into a vault or something. (How can the charge in the center of the sphere be unstable if you're going to blow the whole thing to smithereens anyway.....)
This will sound weird, but what do you mean by "seen"? You can see DNA with the naked eye if you have enough, but it would just be some whitish goo. On the chromosome article, you can see a micrograph of chromosomes, which we know are each a double strand (essentially 2 molecules of DNA, with some other structural components) but all you can see is their overall shape. To see evidence of the helix or base-pairs, I think you'd need X-ray crystallography or a similar "not direct visualization" technique. DMacks (talk) 06:14, 3 November 2008 (UTC)[reply]
Let me rephrase it, are there microscopes that can magnify until the DNA looks like the way it's pictured in illustrations? DahiJynnuByzzuf (talk •
Again, it depends how detailed an illustration you mean (sort-of-elongated-thing, helix, ladder-rungs, actual sugars and bases and atoms, etc.). If you mean a specific type, would be helpful for us to be able to see "what you really mean" specifically (maybe a URL or image from a wikipedia page?). See above where I gave several answers for several levels of detail. DMacks (talk) 09:30, 3 November 2008 (UTC)[reply]
An ordinary light microscope can't possibly 'see' things that are smaller than roughly the wavelength of the light they are using...which is around 500 nanometers. A DNA molecule is around 2 nanometers wide - each "rung" in the ladder is only 0.2 nanometers long - but there are 200 million of them in just one chromosome. So an entire chromosome is 200,000 nanometers long - but only 2 nanometers wide. So clearly, you can't see the molecule as a little twisted ladder in a light microscope - but DNA molecules are twisted and coiled many times over - so an entire DNA molecule ought to be just about visible in the best light microscope you could imagine. However, in a 'typical' light microscope - you won't see a thing.
A 'transmission' electron microscope (TEM) uses teeny-tiny electrons instead of big fat light waves - so a really good one can just about see things about 1 nanometer across. Most are not that good. So even in the best TEM won't see enough detail to see a spiral ladder. At best, you get a two-pixel wide spiral with rungs that are far too small to see.
A 'scanning' electron microscope (SEM) can see individual atoms - but only under special circumstances - such as when they are in 'bulk' form. Picking out a single strand of DNA is not the kind of thing they do well.
Someone suggested their gelatine balls. Whatever the case, the person is either bullshitting or confused. Going by the comments, I'm really not sure but leaning towards bullshitting Nil Einne (talk) 10:54, 3 November 2008 (UTC)[reply]
Actually considering how many people are repeating the same thing, I'm guessing this is some sort of dumb joke aimed at people who don't know chemistry hoping to get them to waste time and make a fool of themselves by looking for calcium bicarbonate. The premise is nonsensical anyway. How can you claim they are water balls when you dumb so much crap into the water to get the balls? Nil Einne (talk) 13:18, 3 November 2008 (UTC)[reply]
Why do lovebirds cuddle up to each other?
Is it only the bird that they're in a relationship with that they cuddle up to or do lovebirds just like to get close to each other in general? --90.240.85.78 (talk) 08:18, 3 November 2008 (UTC)[reply]
Well, not clear but the article says, Lovebirds "are a social and affectionate small parrot," happy to preen their favourite (human) people and "the name Lovebird stems from these parrots' strong, monogamous pair bonding and the long periods of time in which paired birds will spend [sitting] beside one another." Small flocks a speciality too. So it looks like they are socially friendly but cuddly to close companions. Julia Rossi (talk) 10:42, 3 November 2008 (UTC)[reply]
Why do plants use chlorophyll which is a green pigment? Wouldn't it be more useful to use a red pigment so that red light, which is of a high wavelength and thus low energy, is the only light not used? Taking it further, couldn't they use a black pigment? Are there any reasons or theories for why chlorophyll is used? --RMFan1 (talk) 12:03, 3 November 2008 (UTC)[reply]
With evolution it's always very difficult to answer 'why'. It could be just chance. Remember evolution doesn't have a set goal or intelligence. It doesn't know what's best. These speculations [23][24] may interest you. This Yahoo answer [25] is rather good too IMHO. My gut feeling is it would be difficult for a pigment to absorb the entire spectrum (it's obviously possible but it's not so easy for it to happen by pure chance). Very likely, any change to absorb more in the green area would reduce absorption in the blue region which will likely make the plant less efficient. You could use a different pigment (and plants do have different pigments) but this adds another layer of complexity and cost to the plant (remember as well the pigment may compete against the existing pigments to some extent) so unless the tradeoff with having this new pigment makes up for itself, it's not likely to survive. But particularly if this new pigment arises late in the game, your existing pigments are already good enough that it's not easy for this new pigment to provide an advantage to the plant. Remember as well that you need to use the energy effectively, if your just absorbing it but not converting it to chemical energy you just end up with a hot plant. However this is just idle speculation, it's one of the many things we will probably never know why Nil Einne (talk) 13:08, 3 November 2008 (UTC)[reply]
The photoelectric effect implies that chemical reactions involving light can't just use any frequency it likes. If the energy needed to liberate an electron equals say, the yellow wavelength, no amount of red light will do. Similarly, blue light might excite electrons at other places in the process that should not have been excited, ruining the chemical reaction. When taking efficiency of the process into account or what building blocks it requires, chlorophyll might come out on top. (Chlorophyll by the way comes in different types that absorbs different wavelengths) The issue is not settled though, according to [27] which speculates that chlorophyll might have been a historical accident from when algae competed against green-absorbing organisms in the ocean. EverGreg (talk) 14:03, 3 November 2008 (UTC)[reply]
Our article on earthworms has some sentances about this, in the "anatomy" section. There is also a bit in the section "Locomotion and importance to soil". Also, the earthworm article contains links to many more articles about specific families of Earthworms; there is may be more details in those articles if you do some snooping around... --Jayron32.talk.contribs17:06, 3 November 2008 (UTC)[reply]
Preventing inbreeding among critically endangered animals
I read,via a featured yahoo article (here [28]), about the rare sighting and photographing of a Far Eastern Leopard (i.e., the Amur Leopard) wherein concern was expressed on the matter of probable genetic defects arising due to inbreeding among the critically low population of Amur leopards. What methods could/do the scientists use to prevent these defects when attempting to revive the population of a critically endangered species?--Leif edling (talk) 17:19, 3 November 2008 (UTC)[reply]
You could do selective breeding and perhaps some sort of 'genetic compatibility testing' (similar to the way Genetic testing is sometimes used to test for compatibility of couples in some small ethnic groups e.g. [29]). If you want to go ever further, you could use in vitro fertilisation coupled with preimplantation genetic diagnosis. Trouble is, these methods are rather labour intensive (particularly if the population is over a resonable large range) and require you to regularly interfere in the wild population (not something you want to do when there are few members left). In particular, the first method requires you to either intefere in mate choice somehow or to use artifical insemination (and hope other males, e.g. the female leopards well mate, don't kill the offspring or more successfully inseminate the female then you). The second method, presuming you don't want to subject the female to prolonged captivity, requires you to capture the female several times and hope the female doesn't get inseminated before you extract the unfertilised eggs (actually I wonder if you might have no choice but to hold the female, at least for a few days when she nears her period of fertility). Also, presuming you follow the system used in humans of using more embryons then would normally occur to increase the odds, you run the risk of killing the female unless you find a way to interfere in her giving birth if necessary (which carries its own risks). Even then, I suspect you'd still likely have low odds of success requiring you to repeat the process several times. Plus there's still the problem of how males will react (edit: I see from the article there are only 20-30 left in the wild, I presume then they are largely solitary, if the male mate doesn't hang around at all then this shouldn't be an issue). I've never heard of anyone seriously propose these methods except perhaps for breeding captive animals (perhaps for the eventual reintroduction into the wild). I believe the Chinese are doing some stuff with Pandas, but that's more about actually getting them to breed I think and only with ones in cativity. In any case, our best bet is to just prevent this happening in the first place (yes I know this doesn't help with the Amurs). Nil Einne (talk) 17:50, 3 November 2008 (UTC)[reply]
N.B. These problems will be lessened somewhat if you capture and hold your subjects in captivity rather then allowing them to stay in the wild, but this brings its own problems and is likely to be extremely controversial. Also, I read in the Amur Leopard article that there are existing Amur leopards in captivity and these would likely already be selectively bred but I doubt there's much support for bringing any of the wild specimens into play. The only (remote) possibility IMHO is males could be tranquilised and sperm samples taken and this used with the ones already in captivity. Nil Einne (talk) 17:54, 3 November 2008 (UTC)[reply]
Also, captive breeding programs can introduce problems when there is TOO much "genetic diversity" in the breeding population. C.f.orangutans. Early captive breeding programs focused on genetic diversity by interbreeding different populations of orangutan; later genetic studies showed that these populations were likely seperate species, so it called into question the viability of the "crossbreed" orangutans; the different populations were likely different enough to be uniquely adapted to their seperate environments, and it was determined that releasing the hybrid orangutans back into the wild was too risky. The population of orangs at the National Zoo in Washington, D.C. consist of these hybrids; they are currently part of the National Zoo's primate language lab... --Jayron32.talk.contribs02:17, 4 November 2008 (UTC)[reply]
Is there a difference between emperical evidence and observational evidence?
In some countries, you are told not to give blood if you take illegal drugs, even those that are smoked or taken orally. If you take such drugs nasally or intravenously, most countries will have rules that say you shouldn't donate blood. I'm not aware of any country where blood centers test the blood for THC or other drugs. --NorwegianBluetalk19:02, 3 November 2008 (UTC)[reply]
This says it's acceptable, at this particular institution, "as long as you are not under the influence of marijuana at the time of donation". It may well vary at other centres both nationally and internationally. —Cyclonenim (talk · contribs · email) 19:04, 3 November 2008 (UTC)[reply]
I was just reading about how leap seconds are added to the UTC time because Earth's rotation is slowing down. Has this been happening since the Big Bang or does it increase and decrease in cycles? If not a cycle, wouldn't Earth eventually stop rotating? Elfalem (talk) 20:16, 3 November 2008 (UTC)[reply]
Currently the spin rate changes due to friction of tides. The angular momentum is transferred to the moon. This slowing probably started when the moon was created and would have been happening ever since. The Moon would once have been much closer to the earth, with a day only lasting a few hours. Eventually when the day is as long as a lunar month the moon and earth will be tidally locked and there will be no more effect from this. The sun however also causes tides that slows down the earth's spin too. Graeme Bartlett (talk) 20:40, 3 November 2008 (UTC)[reply]
As for "stop rotating", it depends on what your frame of reference is. Consider the moon which, being tidally locked, is a useful illustration of what Earth would eventually act like. To an Earth-bound observer, the moon appears not to rotate (only one face is ever shown). However, if you were to take an extraterrestrial top-down viewpoint, you'd see that the moon actually has one rotation per orbital revolution. The Earth is likewise moving towards such an end state. — Lomn20:54, 3 November 2008 (UTC)[reply]
Actually, I think most of the slowdown is due to post-glacial rebound, the land that was weighed down by glaciers is rebounding which moves mass away from the centre of rotation. Just like putting your arms out while spinning on the spot, that slows down the rotation. Tidal friction does slow the Earth's rotation, but very slowly. --Tango (talk) 21:22, 3 November 2008 (UTC)[reply]
I've done some calculations (feel free to check my maths) - the current rate of slowing is around 1.7ms per century. Even rounding to to 2ms per century in the approx 5 billion years life of the Sun the earth will only have lost just over 50% of it's rotational speed (my calculations give a result of a day of 52 hours or so) - so no, the earth will not 'stop' rotating in it's lifetime - it will be swallowed by the Sun before that. Exxolon (talk) 00:08, 4 November 2008 (UTC)[reply]
Hmm - further calculations. Currently the earth takes 86,400 seconds to rotate one revolution. At the 1.7ms slowdown per century my calculations indicate it will take over 5 TRILLION years for the earth to stop rotating. Exxolon (talk) 14:15, 4 November 2008 (UTC)[reply]
Leap-seconds are subtle. We don't need them because "earth is slowing down." We need them because earth has alraedy slowed down since the date at which we defined the second. If the earth were to suddenly quit slowing down and remain at its current rotational rate, we would still need leap seconds: as a clock, earth is running a bit slow. To keep in sync, we need about one leap second every 18 months. Since earth continues to slow down, leap seconds will become more frequent. -Arch dude (talk) 14:46, 4 November 2008 (UTC)[reply]
The universe is 13.8 billion years old. The Earth is 4.5 billion years old. I think it's safe to say that the Earth has not been slowing down since the big bang. — DanielLC16:21, 4 November 2008 (UTC)[reply]
Are there any legitimate scientific alternatives to evolution?
Are there any legitimate alternative scientific explanations to evolution? For example, for the causes of global warming, solar variation is a legitimate alternative scientific hypothesis. Are there anything similar alternatives to evolution? 216.239.234.196 (talk) 20:48, 3 November 2008 (UTC)[reply]
I don't like to respond to one question by asking another but I think it important in this case to ask: What do you mean by "legitimate?
For example, do you mean:
It seemed plausible when first considered, but did not stand up to serious scrutiny?
It seems plausible even after serious consideration, but has been shown to be incorrect?
It is a thoroughly "respectable" theory that has not been disproven, and provides as good an explanation of the known facts?
The question is akin to asking "Are there any legitimate alternative scientific explanations to the motion of the sun in the sky?" Sure, at one point in history, people believed that the sun moved around the earth. Evolution is such a basic concept, it is no less accepted than is the heliocentric solar system is. --Jayron32.talk.contribs21:31, 3 November 2008 (UTC)[reply]
A key point to make about evolution is that it isn't just a way of explaining observations, it's a logical consequence of life as we know it. If you have lifeforms that reproduce in a way that has a possibility of random mutations (which we do, there's no real doubt about that bit), then evolution is going to happen, it's obvious. The only question is whether or not evolution is sufficient to explain the variety and complexity of the lifeforms we observe. As for alternative answers to that question, I've never heard of any that would qualify as scientific (ie. falsifiable, fit observations and aren't so extremely complicated and unlikely that Occam's Razor rejects them without a second thought). --Tango (talk) 21:32, 3 November 2008 (UTC)[reply]
(I'm the OP on a different PC) If it helps, if you look the global warming article, it states:
"Some other hypotheses departing from the consensus view have been suggested to explain most of the temperature increase. One such hypothesis proposes that warming may be the result of variations in solar activity."
I'm pretty sure the answer is "no". There are variations on the theory, but I don't think anyone has suggested anything significantly different that is actually based on science. --Tango (talk) 22:47, 3 November 2008 (UTC)[reply]
It depends on how you define evolution. Lamarckism is a form of evolution, but it is very different from Darwin's inheritance with variation/survival of the fittest. It's also thoroughly refuted (but, in a certain sense, nice - if you father worked out, you get to be stronger ;-). But no, in modern biology there is no competing theory to evolution, and I'd expect that all new theories would be refinements, not replacements, of evolution. --Stephan Schulz (talk) 23:03, 3 November 2008 (UTC)[reply]
Let's put it this way. There is a lot of variety to life on earth and a fossil record which seems to imply some sort of shared descent. The best scientific explanation of that is some form of evolution—currently evolution by natural selection as articulated by the modern synthesis is the chief candidate for that, but that is relatively recent (1930s; before that Darwinism was thought to have been a dead-end when it comes to the specific mechanism of evolution). Are there other explanations? The only two that any people have put out is some form of special creation (a supernaturalistic intervention) or that extraterrestrials have somehow seeded the planet and manipulated the gene pool (a naturalistic invention). Neither of these theories are scientific as neither are testable, though one could imagine a world in which the latter became possible to test (aliens arrive, thank us for all the hard work). --98.217.8.46 (talk) 02:00, 4 November 2008 (UTC)[reply]
Once you get your head around evolution - you rapidly realise that there is no way it cannot happen. If there is:
Occasional variation in the genetic makeup of individuals...
...that is passed on from parent to child organism...
...and which influences the ability of the organism to produce offspring...
...then there is no way for there NOT to be evolution.
Since all of those things are demonstrably true - then there simply MUST be evolutionary change. The only questions for which an alternative theory might be postulated is whether evolution actually accounts for all of the variation we see - (it seems that it does) and whether it provides some kind of mechanism for how life appeared from non-living things (maybe...maybe not...the jury is still out on that one). But there can't be reasonable doubt about whether things evolve - it's really simple to demonstrate in a laboratory - it happens every day with things like drug-resistant diseases and rats that become immune to rat poison. Now that we've recognised the mechanism happening in life-forms, we can now see it appearing in other settings - the idea that 'memes' are evolving ideas that pass from brain to brain along various communications channels - changing as that happens is an interesting variation on the idea. I would argue that the current financial crisis is the consequence of businesses evolving more and more tightly tuned business practices over the course of time without the pressure of legal limitations to force them to evolve in ways we'd like. You can even argue that (for example) dogs have "evolved" to be suitable pets for humans because our selective breeding of them is merely another influence on their ability to reproduce. It doesn't matter whether aliens manipulated our genes - the aliens had to have evolved at some point (or the meta-aliens who created the aliens...or...). Even if creationism/intelligent-design (a seriously whacked-out theory if ever there was one) turned out to be true - evolution must ALSO be true - because we can see it in action - we can make it happen whenever we choose to do so - and it behaves as we would predict it should when we do those experiments. Hence creationism/ID could only ever be a supplement to the theory of evolution - it can't replace it. SteveBaker (talk) 05:14, 4 November 2008 (UTC)[reply]
You may compare the situation to physics. We have Einsteins theory of gravitation and then there's legitimate alternative theories on gravitation. But there's no alternative to gravitation. In biology there's lots of theories that go beyond school-book texts on evolution and some of them even conflict between each other, such as, genetic drift, Terry Deacons ideas about the Bengalese finch, the theory of punctuated equilibrium, even an almost-lamarckism theory on how certain traits are being transferred, but all of these incorporate darwin's theories. This is a common situation in science, compare for instance with how Newton's laws of gravity is included in Einstein's theory. EverGreg (talk) 09:20, 4 November 2008 (UTC)[reply]
Mesoscaphe
The noted oceanographer and submersible designer Jacques Piccard recently passed away. In the Wikipedia article on him he is credited with the design of the bathyscaphe Trieste. He is also credited with the design of the mesoscaphe Ben Franklin (PX-15) and commanded the mission in 1969. There is no reference or link to "mesoscaphe" in Wikipedia. What is a "mesoscaphe" and how is it difference from a bathyscaphe?
Garybirk (talk) 20:58, 3 November 2008 (UTC)[reply]
One would assume that the mesoscaphe was so called because it was designed for exploration at levels not as deep as those reachable by a bathyscaphe. Bathy- comes from the Greek word for "deep"; meso- from the Greek word for "middle." Deor (talk) 23:10, 3 November 2008 (UTC)[reply]
I don't know any way of working this out, but for some reason I imagine even if you filled the whole car with helium, it would not lift. I imagine the mass of the car is too great. —Cyclonenim (talk · contribs · email) 21:49, 3 November 2008 (UTC)[reply]
Helium, at standard temperature and pressure, has a density of 0.1786 g/L. The density of air (again at STP) is 1.2754 g/L. Consequently, you get about 1.1 grams of lift per liter of helium. Assuming a 1000kg car, you'd need about 900 000 liters of helium -- a spherical balloon some 12 meters in diameter (and that's ignoring the mass of the balloon and other associated hardware). — Lomn21:56, 3 November 2008 (UTC)[reply]
FYI, what you typed rendered as 4/(3pi)*12^3 -- pi is on the wrong side of 4/3, and you cubed the diameter rather than the radius. — Lomn14:23, 4 November 2008 (UTC)[reply]
So if you want to REALLY be sure to do it, just make the balloon 12.5 meters. BTW, the calculation can be seen empirically with such objects as blimps. Compare the size of the balloon to the size of the car it is carrying. I am sure that the balloon in a blimp is more than adequate (i.e. its SO big that it contains MUCH more helium than needed) but it does give you an idea of scale... --Jayron32.talk.contribs03:49, 4 November 2008 (UTC)[reply]
observing the dead cat
Forgive me if I'm interpreting this wrong..
The article says the cat "is placed in a sealed box shielded against environmentally induced quantum decoherence".. but isn't the question moot because it's impossible to shield against quantum decoherence? If the cat dies then its mass is concentrated closer to the bottom of the box than if it were standing up.. so light will gravitationally lens around the box slightly differently.. 71.176.167.123 (talk) 22:52, 3 November 2008 (UTC)[reply]
That's an interesting introduction bringing gravity into the problem. If there was a proper theory that combined quantum mechanics and gravitation then one would probably be able to have a superposition where he mass was at the bottom and where the mass was in the middle. I don't think it works out very well at present though - have to hand over to someone who knows more about that. (An applied mathematician considering milk production: consider a spherical cow...) Dmcq (talk) 23:08, 3 November 2008 (UTC)[reply]
Schrödinger's cat, like many thought experiments, involve assumptions to get the point across. Maxwell's demon, for example, assumes the existence of a massless door that requires no energy to open and close. You do have a novel way of determining the position of the cat through gravitational lensing, but this still tells you nothing about the living state, only whether the cat is standing up or lying down. For the purpose of this experiment, assume the box is too cramped for the cat to move. ~Amatulić (talk) 23:11, 3 November 2008 (UTC)[reply]
See Spherical cow. The origin of the term is supposed to be that people from agriculture went to someone from the physics department at the University of Illinois to see if the folks there could help with a problem of decreasing milk production [30]. Edison (talk) 04:02, 4 November 2008 (UTC)[reply]
Essentially, if you put the 50% killing mechanism and a cat, into an impossible magic box. Something impossible happens to the cat. Perhaps not as shocking as Schrodinger meant it to be, but it's still useful as a thought experiment and teaching tool. APL (talk) 14:07, 4 November 2008 (UTC)[reply]
I remember reading an article on here where they pointed out that a small gravitational effect can be masked by the quantum effects on the scale, or something to that effect. I doubt it would do much at that scale, but that's only one of the reasons the quantum waveform would collapse if this thought experiment were actually carried out. — DanielLC16:14, 4 November 2008 (UTC)[reply]
November 4
Religion, sci-fi and the brain
Has there been any study into whether reading science fiction or fantasy releases neurochemicals, or activates areas of the brain, associated with religious or spiritual experience, and if so whether the extent to which this so is correlated with the reader's opinion of the work? NeonMerlin03:59, 4 November 2008 (UTC)[reply]
Thermodynamics
We already know that the temperature of something gives off different color. For example, a blacksmith can just look at the color of a horseshoe and tell how hot it is. It can be yellow or red or even white if it is really really really hot. We can also look at our sun and make intelligent guesses. My question is, is it possible to heat up something soooooo much that it might actually become black?69.224.117.143 (talk) 05:04, 4 November 2008 (UTC)[reply]
Black isn't a color of light something can emit, it's the absence of light. A horseshoe can certainly be heated up until it's black...room temperature (although it's actually still emitting light, just too far infrared to see. See black body to understand how the color of incandescence corresponds to temperature. DMacks (talk) 05:16, 4 November 2008 (UTC)[reply]
So what you're probably thinking is that as the temperature rises - so the color shifts up the spectrum from infrared - through red, yellow, blue and then off into ultraviolet - so that the object would once again appear black? If that's what you're thinking then this sentence from black body should help: "So, as temperature increases, the glow color changes from red to yellow to white to blue. Even as the peak wavelength moves into the ultra-violet, enough radiation continues to be emitted in the blue wavelengths that the body will continue to appear blue. It will never become invisible — indeed, the radiation of visible light increases monotonically with temperature.". So while the PEAK of the radiation may well be off into the ultraviolet - you still see increasing amounts of visible light - so the object just continues to get more and more brightly white - even as the UV is invisibly frying your skin. This is evident because (for example) as you heat a piece of iron, it goes from red to yellow to white. It doesn't ever glow green. That's because the red and yellow light didn't go away as the frequency of the peak shifted upwards - so that even when there is a noticable amount of green light being generated - there is enough red still present to make it look yellow - and as the peak shifts towards blue, there is still enough red and green to make it look white.
Functional Group effects on the acidity of a compound
What effects do funcational groups alcohol, carboxylic acids and halogens, as well as the number of hydrocarbons have on the acididyt of a compound.
How can you identify, given the structural formaula, which compound is most/least acidic.
Generally, the presense of electron-withdrawing groups will tend to weaken the C-H bond at neighboring carbon atoms (the so-called "alpha" position), thereby making those positions slightly more acidic. For compounds such as Acetylacetone aka 2,4-pentadione, the hydrogens on the carbon between the carboxyl groups are sufficiently acidic enough to be removed by sodium hydroxide; most C-H bonds are unaffected by NaOH... Although, you should probably do your own homework... --Jayron32.talk.contribs06:13, 4 November 2008 (UTC)[reply]
Robo-thugs
In the North Hollywood shootout, 17 cops and civilians were shot but not a single one was killed. Is it a "thankful" side-effect by the bad guys' use of armor-piercing rounds? I mean anti-personnel rounds (e.g., hollow-point bullets) may shatter upon impact and blow up inside the human body. Armor-piercing rounds may create clean-cut wounds that are less damaging. -- Toytoy (talk) 07:39, 4 November 2008 (UTC)[reply]
I've no idea about ones that blow-up inside the body but anything that goes through will presumably leave a pretty hefty exit-wound, and will potentially cause plenty of damage. I suspect that a key factor would've been the speed with which the victims of the gunshots were treated (were ambulances on stand-by at the scene for example), along with perhaps a bit of luck regarding the placement of the wound on the body. 194.221.133.226 (talk) 11:20, 4 November 2008 (UTC)[reply]
Not an expert on bullet wounds, but I'm using the resources at hand here. The article on ballistic trauma says that rifles typically do more damage than hand-guns, although hollow-point bullets are more damaging than full metal jackets. There are many factors involved, however, as already mentioned. The police acted quickly and effectively in this case, and many people were hit through cover by armor-piercing bullets, which may or may not have reduced the severity of wounds; people in cover would also be hit by ricochets, again at lower velocity, or in bodily extremities. Looking at typical shootouts, such as 1986 FBI Miami shootout or Tyler courthouse shooting, once fire has been returned, fatal shots by criminals (even from rifle or carbine) were typically from very close range. The lesson being that unless you have a clear shot at a stationary target, it's surprisingly hard to shoot someone dead (assuming medical care is on hand).--Maltelauridsbrigge (talk) 16:03, 4 November 2008 (UTC)[reply]
(ec)Armor-piercing rounds definitely do less damage than hollow points or heavier, slower moving slugs like a .45. AP rounds pass through the human body and hardly slow down, while a hollow point breaks up and delivers all of its energy into the target. I'd say the AP rounds helped but it was really just incredible luck that no one got hit in a vital organ and quick respone by emergency services.-- Mad031683 (talk) 16:08, 4 November 2008 (UTC)[reply]
environmental issues
why is there a need to reorient the values that people hold concern the environment based on the development of environmental ethics on a social perspective? —Preceding unsigned comment added by 121.97.4.2 (talk) 08:21, 4 November 2008 (UTC)[reply]
Just out of personal curiosity - assuming hypothetically that Abraham was a real person who lived 1800 BC and really had 8 sons (sadly there's no record of daughters), would pretty much everyone in the western world be descended from him? Is there a way to calculate something like this? —Preceding unsigned comment added by Vultur (talk • contribs) 09:26, 4 November 2008 (UTC)[reply]
Surprisingly, possibly yes. Some native American populations have been fairly isolated (as have native Australian ones - what is "the western world" for you?). But there are some gene flow models that make a most recent common ancestor somewhere between the 6th and the 1st millenia BCE plausible. With an extremely naive approach, 1800 BCE is about 1300 generations ago, so you could have up to 2130 (1.361e39) ancestors. Compare that to the world population of maybe 40 million (4e6) back in 1800 BCE, and you can get an impression of how much intermixing of lineages has taken place. You might want to look at our articles on Y-chromosomal Adam and Mitochondrial Eve, as well, although these deal with much more limited lines of descent. Another interesting point is the Ghengis Khan Effect, which gives an idea of how fast a gene can spread. --Stephan Schulz (talk) 10:14, 4 November 2008 (UTC)[reply]
Do fairness creams really work?
Is there any scientific evidence to the efficacy of fairness creams? I am asking this because there is a barrage of fairness creams being introduced into the market for men as well as women where I live and I want to know if these companies are all just taking the consumers for a ride. I don't need one myself, but I am curious if they work at all, given that it is a massive industry. I looked but I couldn't find any information on the skin pigmentation article. Thanks. 124.30.235.62 (talk) 10:31, 4 November 2008 (UTC)[reply]
Thanks! I read that. So it looks like there is some scientific basis to skin whitening products. That's good to know, I suspected the compnaies were selling just wuga wuga to the people :P 125.21.165.158 (talk) 11:53, 4 November 2008 (UTC)[reply]
So, that would be the real challenege, wouldn't it. The person to do that would be the first in the history of the world. Tell me, what are some possible tracks I could pursue? Are some fields of inquiry inherently more ridiculous than others? What are some quite ridiculous real Nobel prizes that have been given -- I'm thinking of Kissinger's Nobel Peace Prize! —Preceding unsigned comment added by 82.124.209.97 (talk) 13:24, 4 November 2008 (UTC)[reply]
Might be tough. Even assuming you could get a Nobel for a silly enough topic, AIR tends to choose rather obscure bits of research for award. A nobel prize winning contribution might be too high-profile to make effective comedy. APL (talk) 14:11, 4 November 2008 (UTC)[reply]
I think you'd have to go the other way: get Ig for something silly, then find it's actually based on a groundbreaking and novel principle that gets extended into a Nobel. Like what if this year's soda/sperm result led to discovery of a whole new cell-surface receptor class that 1) happened to be responsible for the soda effect and also 2) were responsible for various parts of the sperm/egg fusion process? DMacks (talk) 16:41, 4 November 2008 (UTC)[reply]
Suspensions
I'm looking for examples of commercial situations where there is a need to keep solid particles suspended in a water-based solution. The only two I've come up with so far is Drilling mud and hydroseeding. I'm not interested in food applications. My thanks if you can think of any. ike9898 (talk) 15:14, 4 November 2008 (UTC)[reply]
Could someone give me a brief overview of functional morphology and its purposes? The best resource I can find online is [31] which doesn't go into much detail. 81.154.63.120 (talk) 17:57, 4 November 2008 (UTC)[reply]
