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.
Hi, there was a question once at Colour of water about why the water in the pool in the image at the right looks equally blue regardless of whether one is looking through a few centimetres (at the edge of the pool) or several feet (in the centre of the pool). "Common sense" would suggest that the more water you looked through, the bluer it would be. AFAIK, no satisfactory answer was ever provided. Does anyone have an explanation? 86.171.43.156 (talk)
Water is very faintly blue (or blue-green, in the case of sea water). So, a small amount of it will appear clear, unless blue dye has been added or something blue is behind it, like the bottom of the pool painted blue. In your example, the water in the bucket certainly doesn't look as blue. StuRat (talk) 03:00, 9 April 2013 (UTC)[reply]
I don't see how any of that answers the question. Why does the water in the bucket look much less blue than the same thickness of water at the side of the pool? (We take it on trust that the pool is tiled throughout with the same white tiles as are visible around the edge.) Why does the deepness of the blue not reduce dramatically at the sides of the pool where you are looking through an increasingly small distance of water? 86.171.43.156 (talk) 03:35, 9 April 2013 (UTC)[reply]
I think they're saying that there is a point near the wall where you are only looking through as much water as is in the bucket, yet it looks far more blue. I suspect the answer is simple scattering. The water in the pool is all scattering the blue reflected off the bottom of the pool. Since the bucket is opaque and white, it will look far more clear. Vespine (talk) 04:05, 9 April 2013 (UTC)[reply]
(ec) I think I understand. He was assuming that the light 6 inches below the waterline shines straight in 6 inches, hits the edge of the pool, then reflects right back out of the pool, just as it does in the bucket. However, most of the light that hits 6 inches below the waterline is reflected downwards to the bottom of the pool, while other light reflects back up from the bottom of the pool, hits that spot 6 inches below the waterline, and back out again. Thus, this light has traveled through a lot more than 1 foot of water total, and had the redder waves absorbed, leaving a distinctly bluish tint.
I think it's because your pool has a blue liner and your bucket is white. Also, if you ever look at a large swimming pool with a diving-depth deep-end it is noticeably bluer. There are also effects from disinfectants in the water, especially pools, depending on what you use. Some municipal water supplies have a greenish tint for this reason. Shadowjams (talk) 14:05, 9 April 2013 (UTC)[reply]
As I mentioned above, "we take it on trust that the pool is tiled throughout with the same white tiles as are visible around the edge". If that is not the case then all bets are off. 86.128.0.95 (talk) 17:23, 9 April 2013 (UTC) Also, the effects of tints in the water do not seem relevant to the question of why the water looks very blue right to the edge of the pool, or why the bucket (assuming it is the same water as is in the pool) is much less blue than when looking through equivalent distance of water at the edge of the pool.[reply]
I agree it seems a bit odd that you can't see any trace of the tile divisions below the waterline, but I still believe that the tiling (or, probably, imitation tiling) stretches down into the pool. What do other people think? 86.128.0.95 (talk) 17:55, 9 April 2013 (UTC)[reply]
Well, we're questioning the very premise of your question, and now you're trying to fiat a basic premise of the facts. I do think water in fact will scatter more light the more of it light has to go through, and I don't think that your picture is comparing apples to apples. We're surprisingly good at answering the question "why does this thing that doesn't happen happen" here at the reference desk, but you may have stumped even us this time. Shadowjams (talk) 21:43, 9 April 2013 (UTC)[reply]
If the pool has a blue liner then the whole purpose of the photo is destroyed, and the caption "Water in an indoor swimming pool appears blue against a white background, right up to the waterline. The same water inside a floating white bucket appears only slightly blue." is a deception. There seems no reason for someone to do that, which is why I take it on trust, though I cannot prove it, that the pool does not have such a liner. 86.128.0.95 (talk) 22:35, 9 April 2013 (UTC)[reply]
I think the question has been answered- more blue photons are trapped in the water medium and scattered in the pool. May I suggest the OP do some real life experiments :) Ap-uk (talk) 22:37, 9 April 2013 (UTC)[reply]
Here's an experiment you can do that I think is related (I discovered this accidentally). Take a basic white porcelain sink, with nothing in it, and fill it with a few inches of water. Then put your hand into the water. When you do, you will see (probably) that the water appears to take on a reddish tinge -- the entire pool of water, even far away from your hand. Looie496 (talk) 22:54, 9 April 2013 (UTC)[reply]
It seemed to me that Looie was pulling our legs. But, as I was about to wash the dishes, I tried this (in a regular stainless steel kitchen sink). No such red tinge occurred, of course. But what happens if a dispersant is added? It happens that I have an expired box of dispersible piroxicam (a painkiller you mix with water and drink). I stirred in several tablets until the plug was a bit hard to see. Then put a red object in. Still no red tinge!. Just a red blur around the object. I reckon StuRat has the key to it - the pool in the picture has the tiles below the water blue in colour (except for the upper three rows), just like many pools I've seen. Wickwack 124.182.36.200 (talk) 23:51, 9 April 2013 (UTC)[reply]
Of course the danger of any experiment is that it may fail if the conditions are varied. I just tried it again with my bathroom sink, and it works as described. The water in the sink appears to have a slight bluish tinge when there is nothing in it; when I put my hand in the tinge becomes reddish. Looie496 (talk) 01:49, 10 April 2013 (UTC)[reply]
I've seen this happen, but it does need to be a situation (like a shiny white sink) where your hand is very much the dominant colour, which reflects back. And it usually works best in sunny conditions. 86.161.209.128 (talk) 08:28, 10 April 2013 (UTC)[reply]
Couple things to note:
The picture has been edited/processed after capture; no information is given about what color the ambient lighting had and what processing was done to the picture.
The pool probably had a blue liner, which is quite common. (I've seen big fish tanks that measure a few feet across. I don't remember seeing any noticeable blueness when looking through the tanks sideway.)
The bucket may not be that opaque. The little blueness in the water inside the bucket may be the blue reflected light in the pool showing through.
Mus musculus anatomy and behavior, plus trap physics
Some few minutes ago, I heard the snap of the mousetrap in the kitchen, and I went out soon enough that the mouse was still twitching and its tail still moving around. This prompted a few questions in my mind that I've not been able to answer with a Google search:
Why does a trapped mouse twitch? Is it something neurological that's comparable to what causes a chicken to move uncontrollably after being beheaded?
What does a healthy Mus musculus do with its tail in daily life? Balance? I've only ever seen the species (1) in traps, or (2) running around on my floors, seemingly not using its tail.
Why do traps often flip upside down when set off by a mouse? Is the spring so powerful that its momentum forces the trap to go upside down, or is there some other explanation?
1) All animals may twitch shortly after death, including humans. The muscle cells remain alive, and have energy, for some time, but only receive random nerve impulses, so move randomly. If you apply an electric current, you can cause the twitching yourself. This is the basis for the fictional idea that you can bring the dead back to life with a lot of electricity, as in Frankenstein.
2) Yes, balance. You'd need some high speed film to see it using it as a counterbalance during quick turns, etc.
Agreed with Stu. But if you suspect the mouse is still alive, put it in a plastic bag and step on it to put it out of its misery. μηδείς (talk) 11:31, 9 April 2013 (UTC)[reply]
After reading the "orbital debris" article, and a lot of the references, I just can't quite understand why so much stuff stays there.
(1)Surely whenever there's a collision between objects, or even a close pass, they must both end up with a change in velocity that would eventually de-orbit them?
(2)Is a "Graveyard orbit" one that is slowly decaying away from Earth? or is it just a stable orbit that's out of the way above the valuable stuff?
(3)How big would an orbiting object have to be to actually attract other objects to itself by gravity?
I hope someone can help me with this, thanks in advance. 122.108.189.192 (talk) 07:34, 9 April 2013 (UTC)[reply]
If they collide they just get orbits which aren't so circular in general. Reducing the speed of an object that is in a circular orbit puts it into a more elliptical orbit but whatever happens unless it encounters drag from the atmosphere it eventually gets back to where it started (ignoring other gravity effects, pressure from sunlight solar wind, magnetism etc.). For low earth ones that means they will probably decay faster but for higher ones it simply means you have an expanding cloud of debris. The graveyard orbit is just one that's out of the way, I don't think of it as a complete solution myself. The stuff up there is too small and far away from each other for gravitation to have an effect that matters. Dmcq (talk) 08:19, 9 April 2013 (UTC)[reply]
There is no minimum size an object has to be to attract other objects. However, the gravitational attraction of small objects is very easily overcome by other forces. In particular tidal forces prevent the formation of bodies by gravity inside the Roche limit. SpinningSpark11:19, 9 April 2013 (UTC)[reply]
Over time, collisions will cause objects to either go into low enough orbits that atmospheric drag causes them to re-enter and burn up, or go into high enough orbits that they stop colliding with things. However, collisions in orbit are actually very rare - it would take centuries (at least) for what is up there to clean itself up through collisions.
Graveyard orbits are just high enough orbits to be out of the way. They are potentially still a problem if you want to go through that orbit (to get to geostationary orbit, for example) or if two things in graveyard orbits collide and some of the parts get knocked into orbits that cross low earth orbit (although, the further out you go the more room there is, so such collisions are unlikely).
See Hill sphere for details of stable orbits around satellites. For objects in low earth orbit, the object would have to be denser that any naturally occuring materials for anything to orbit them (it isn't enough for an object to be very massive, it needs to be small too or orbits around it have to be too large to avoid colliding with it). There will still be an effect from gravity even if there isn't a stable orbit possible, but for any realistic satellite it won't be a measurable effect. --Tango (talk) 11:26, 9 April 2013 (UTC)[reply]
By the way, graveyard orbits for (former) geostationary satellites are only a little bit above the geostationary altitude. Because the Moon is slowing down Earth's rotation, we will have a problem again in 30 or 40 million years or so, when the geostationary height will be higher up due to the slower rotation of the Earth. But I don't know how stable the satellite's orbit is over such a timescale. Icek (talk) 14:37, 9 April 2013 (UTC)[reply]
I agree that it's fake. However, I think it's time-lapse photography (as opposed to being edited with the glass of water replacing the glass of ice). The utility room or garage where the demo takes place must be cold enough to freeze the water over several hours. Note that it is possible to freeze water instantly, if you can make it into a supercooled liquid first (why does that link lead to an article on glass blowing ?). Or, of course, you can also just cool it very quickly, say by dumping dry ice into it (stand back !). StuRat (talk) 14:26, 9 April 2013 (UTC)[reply]
"Demonstaratio" = a method of evaluating the effectiveness of any demonstration = (time audience spends staring at demonstration) / (time audience spends staring out the window). :-) StuRat (talk) 15:44, 9 April 2013 (UTC)[reply]
Sure, supercooled water will freeze suddenly like that - but adding the salt would have been enough to add the necessary "nucleation sites" and to cause it to freeze even faster than the demo purported to show. So we know that it wasn't super-cooled. Even if this was super-cooled water, all of the nonsense with the lighter and the straw would be superfluous - and because salt actually lowers the freezing point of water, it would make matters harder. So the odds are good that this was done in a very cold garage over many hours. The clue that this is such a simple fake is that the lighting in the background of the room and on the table changes rapidly as the ice forms - clearly indicating that this is a speeded-up video and light through some window is changing due to the sun moving across the sky. So, yeah - it's another boring YouTube fake...yawn. It's becoming *so* common for people to make these science-looking demos - and easily more than half of them are obvious fakes like this one - it's really childish and it's annoying because it un-educates gullible people - making them even more stupid than they were at the outset! SteveBaker (talk) 16:14, 9 April 2013 (UTC)[reply]
when i grew up in canada, it would get so cold the words would freeze as they came out of your mouth, and you had to collect them and carry them inside and thaw them out by the fire to find out what the other guy said. Gzuckier (talk) 19:12, 9 April 2013 (UTC)[reply]
It isn't supercooled ice or supercooled water, it's supersaturated solution of potassium acetate or sodium acetate. That is, there are no camera tricks, its just that someone gave a bogus explanation to a real video. I've done this demonstration a hundred times in chemistry class, though I didn't pretend what was happening was ice. See this video which largely mimics exactly what is showed above, except that it gives the actual, correct chemical explanation. --Jayron3221:52, 9 April 2013 (UTC)[reply]
I'd have thought if that were so the crystals that were dropped into it would have acted as nucleation centres but nothing happened. I think the more obvious explanation above as indicated by the lights changing is the more probable. Dmcq (talk) 22:50, 9 April 2013 (UTC)[reply]
Well, it's ok to get a rough idea. If the OP is interested in actual details, PubMed is far better. The is a lot of circumstantial evidence for a link. Current thinking seems to revolve around various different aspects of diabetes, or more accurately metabolic syndrome. 1) Vascular damage 2)Metabolic damage due to hyperglycaemia, 3)Low level systemic inflammation and 4) The effects of high insulin levels on Amyloid β deposition. Now, the first three of these are definitely risk factors for developing neurodegenerative diseases, but whether they specifically promote Alzheimer's is still an open question. The last is a very interesting, possible direct causal link. Interestingly, Alzheimer's may cause central insulin resistance as well, so there may be an interaction both ways. Fgf10 (talk) 20:36, 9 April 2013 (UTC)[reply]
There's an idea floating around that Alzheimers should be considered "Type 3 Diabetes". [4][5][6] The last is a scientific article. Pull quote: "We conclude that the term “type 3 diabetes” accurately reflects the fact that AD represents a form of diabetes that selectively involves the brain and has molecular and biochemical features that overlap with both type 1 diabetes mellitus and T2DM." -- 205.175.124.30 (talk) 21:43, 9 April 2013 (UTC)[reply]
Is it true that Homo sapiens idaltu is younger than Homo sapiens sapiens?
According to several Wikipedia articles, including both Anatomically modern humans and Homo sapiens idaltu, yes. The earliest Homo sapiens sapiens fossils are believed to be dated to ~ 195,000 years ago, while the earliest Homo sapiens idaltu are dated to ~ 160,000 years ago. Of course, that's just what we know, it's possible that either or both of those dates could be pushed back if new fossils are found, but it appears, based on the (admitedly very limited) data we have right now, the oldest known Homo sapiens sapiens is older than the oldest known Homo sapiens idaltu. --Jayron3221:57, 9 April 2013 (UTC)[reply]
Well, the article makes it more muddy than that. There are oldest HSS fossil is still older than the oldest HSI fossil (which would then require a time machine for the latter to be an ancestor of the former); analysis of features seems to point to HSI being older than HSS, but until we have that "smoking gun" of an HSI fossil which is older than 195,000 years, then that is just conjecture. On the basic chronology of the fossils we have, the oldest HSS is older than the oldest HSI. Other questions in this vein remain open. --Jayron3222:26, 9 April 2013 (UTC)[reply]
Archaic features doesn't imply ancestral. It could just have changed less since the most recent common ancestor. --Tango (talk) 11:38, 10 April 2013 (UTC)[reply]
A scan of the recent literature indicates that the classification of idaltu as a separate subspecies is not well established. Pretty much every recent discussion uses qualifiers like "proposed" or "suggested" or "purported". Looie496 (talk) 22:42, 9 April 2013 (UTC)[reply]
Does it make sense to speak of subspecies being older or younger than each other? The split from one species into two subspecies happened at a particular (impossible to really define) time, so both are the same age. The only way they could be different ages is if there is a third subspecies involved (either they both split off from that third subspecies at different times, or the first split was into, say, HSS and HSX and then HSI split off from HSX and HSX died out. Is there a proposed third subspecies "inbetween" HSS and HSI? --Tango (talk) 11:38, 10 April 2013 (UTC)[reply]
Worry about ranges based on one specimen relies on the rather nave (in the academic sense) assumption that fossil attestation is a perfect reflection of time range. You are looking at what is a statistical sample with fossils, not a complete record. No palaeontologist believes that the first or last found fossil of a species is the first or last actual individual of a species. There are a slew of dinosaur species the last specimen of which was found a million or half a million years before the KT event and none after. That doesn't mean that dinosaurs started going extinct in anticipation of Chixulub. When only half-a-dozen specimens of a species that existed for 5 million years are known, it's highly improbable any of them will date to that species first or last decade of existence. μηδείς (talk) 17:24, 10 April 2013 (UTC)[reply]
Is this a conspiracy theory?
Is there any truth to the story that someone once invented a method of fully recharging standard alkaline batteries - but that Big Battery bought up the rights to the technology and have been sitting on it for years?
Someone mentioned this to me recently, but it sounded to me like a variation on the old 'the oil companies are intentionally keeping the water-powered car down' or 'the major pharmaceutical companies already know the cure for cancer but there's more profit for them in keeping people on chemotherapy for years, so they don't tell anyone' BS, so I was sceptical.
There's nothing new about recharging dry cells - alkaline or regular carbon-zinc. Hobby electronics magazines now and then publish the details on how to do it - generally using a pulsed and/or periodically reversed current. The trouble is, it just isn't cost effective. Just about every type of cell (primary or secondary) has a finite life: The lifetime is determined by the fact that a given cell type has a certain approximate number of charge/discharge cycles that it can tolerate. Cells in general deteriorate while held at full charge by trickle changing as well. With dry cells the change/dicharge lietime is very short. You may only get 2 or 3 cycles before the capacity drops to a very low value. Another factor is that dry cells are designed to be leakproof, but under normal use only. If you recharge, you will likely get leakage, damaging your battery powered eqipment.
As a general principle, you can assume that the idea that big companies conceal usefull things is complete nonsense. If it works and is cost effective, somebody somewhere will let the cat out of the bag. In countries that have a strong patent regime, you generally can only patent a manufacturing process or implementation - you cannot patent a function. For example, if I invent a novel and very simple circuit to pulse-charge a battery, I could patent it. That will (in theory anyway) stop you from copying my circuit. But if you invent a completely different circuit that does exactly the same thing, and market it, my patent is not infringed, and there's absoulutely nothing I can do about you. You've rendered my patent useless. What the circuit does, ie pulse charging, cannot be patented. Patents and other forms of rights are just simply not observed in many countries anyway - especially Asian (except Japan & Korea) and communist countries. Communism fundamentally has a problem with any sort of intelectual property.
Stanford's Grid Storage project is reportedly working on batteries that should last 30 or 40 years, but that's not without recharging (they are thinking of these as rechargeables that can go through >40,000 cycles without deteriorating). I can see that being easily misinterpreted as a battery that lasts 40 years period. Someguy1221 (talk) 04:33, 10 April 2013 (UTC)[reply]
Nickel-iron batteries, a very old rechargeable technology, last a very long time, typically 4 to 10 times the life of a lead-acid under similar conditions, but they are very expensive - that's why you don't see much of them. Wickwack 124.182.36.200 (talk) 04:46, 10 April 2013 (UTC)[reply]
What do you mean by 'bought the rights'? 1 There was a patent on the technology and they bought it? 2 Or they paid the inventor to shut up forever? If it was 1, the patent will be published someday and it will also expire. So the company would lose its opportunity cost of exploiting the idea. If it was 2 we won't ever know. OsmanRF34 (talk) 12:25, 10 April 2013 (UTC)[reply]
Technically if the patent exists it is already published; patents aren't secret (except in the cases of national security). Adding just to Wickwack's answer, this sort of statement also misunderstands the nature of invention, which is rarely a "one guy figures out the only way to do it and nobody else would have been able to copy him." In truth, big companies have huge industrial R&D labs, all in competition with each other, and they are all working in the same fields and reading the same literature and checking out all the new patents (and even patent applications) that come out. So the idea that one guy would do this and could be silenced... it's not likely. There have been a few cases of people discovering things really out of left field that were not really in line with what others in their line of work were doing, but they are the exception, not the rule. Invention has not really been about lone geniuses for over a century now. --Mr.98 (talk) 12:44, 10 April 2013 (UTC)[reply]
It's not a cover-up. Alkaline battery rechargers are commonplace! Just do a Google search on "buy alkaline battery charger" and you'll see dozens of them for sale for around $25 - even on Amazon.com! The reason they aren't popular is that they don't really work very well - and for most people, they aren't cost-effective. Sure, you can get *SOME* charge into a dead disposable battery - but not much. It'll go dead again much more quickly than it originally took to drain it. Also, the alkaline batteries will tend to leak - and the more times you try to recharge it, the worse these effects get.
Whether these things are cost-effective is difficult to say. Let's suppose you use 80 disposable AA's per year.
Right now, Duracel AA's cost $5 for 8 batteries - so if you just toss out your batteries, it'll cost you $50 per year.
If recharge your AA's once and then throw them away to avoid the leakage problems - and let's suppose each one gets back only half of it's original charge when you recharge it. This contraption cuts your battery purchases by 1/3rd. Now you only need 52 batteries - so you spent $25 for the charger and $33 for batteries ($58) instead of $50 on batteries alone...so you don't quite break even in the first year of use. So that battery usage rate, you'll break even after around 13 or 14 months...it's not a terrible investment.
Duracel rechargeable batteries cost $8 for four...$2 each. If you buy 8 of them, plus a charger (they are less complicated than alkaline battery rechargers - I see them for $8) - you can fully recharge each battery ten times - then you spent $16 for a year's worth of batteries and $8 for the charger instead of $50 (alkalines) or $58 (alkalines plus recharger) - and you break even after only 6 months! Much, MUCH better than with alkaline battery rechargers.
HOWEVER: The actual math depends critically on the number of batteries you need SIMULTANEOUSLY. If you only need 1 battery - but you replace it 80 times in a year - then using a rechargable battery is MASSIVELY the best choice. The initial outlay on battery and charger is $10 and you save $40 in the first year alone! But if you have enough gizmos that you need 80 batteries at once - and each one is only replaced once a year - then you can't possibly use rechargables - you spend $160 on batteries and $8 for the recharger! It would take over three years to break even!! Recharging your alkalines in that scenario would definitely be worthwhile.
... and it's not a new idea. I was recharging carbon-zinc batteries fifty years ago, but with very limited success. They worked for a short time in low-current applications, but I never succeeded in restoring anywhere near half the original charge. Dbfirs18:20, 10 April 2013 (UTC)[reply]
Say I have a Orange. I know that the orange color is due to the orange photons not been absorbed into the fruit as energy.
However I had thought that the mechanism of interaction of the non orange photons was one in which the molecules at the surface of the fruit vibrate in various modes and are turned into a kind of kinetic energy. Now I read in the "color of water" article that electrons can also be involved. Is this correct and can more detail be given on this mechanism which I am assuming does not rely on electrons being promoted to higher shells? Ap-uk (talk) 22:58, 9 April 2013 (UTC)[reply]
Visible light pretty much all falls in the range of electron transitions - that is, saying "the molecules at the surface of the fruit vibrate in various modes" to absorb certain colors is not typically correct, as the the rotation and translational movement of the molecule as a whole fall in the microwave and infrared regions of the spectrum, respectively (see microwave spectroscopy and infrared spectroscopy for details). Thus the "non-orange" photons are mostly being absorbed by the electron transitions. The article electromagnetic absorption by water indicates that in the case of water, there are no electronic transitions in the visible region, but it does have absorption in the visible region due to overtones from the infrared vibrational bands. These absorb most strongly at, for example, 2662 nm, but there is weak absorbance at frequency multiples, e.g. 1331 nm and 665.5 nm, some of which fall in the red-orange-yellow end of the spectrum, resulting in a very pale (because of weak absorbance) blue color. - 71.35.98.207 (talk) 17:08, 10 April 2013 (UTC)[reply]
I guess what confuses me is that if the electrons are promoted due to the photons moving them them to a higher shell then why do they not re-emit the light? Ap-uk (talk) 17:43, 10 April 2013 (UTC)[reply]
I thought quanta was a specific packet of energy, why should energy be "lost"? I don't think my oranges glow in the dark though ;) Ap-uk (talk) 20:27, 10 April 2013 (UTC)[reply]
A key thing to remember about light interacting with matter is that there are rules: momentum and energy both need to be conserved at the same time. So for example a fast-moving electron, all by itself, can't emit a photon - heck, in its frame of reference it is at rest. The same applies in reverse, so you can't just absorb a photon into an isolated electron and move it. The interaction has to be more complicated - photons can push two things apart, for example, which allows its large amount of energy to be taken up by a target while transmitting just its very small amount of momentum. For example, pushing an electron in an atom into a higher energy level. But if the electron can find other ways to slip back down in energy - by knocking into other atoms, for example - then it doesn't have to give the photon back intact. You can argue that eventually it "makes change" in photons - assuming the system stays at the same temperature, eventually all the energy taken up in big visible photons will be given back in low energy blackbody radiation, which at room temperature is infrared. Wnt (talk) 23:32, 10 April 2013 (UTC)[reply]
Can anybody help me find some information about the environment of Overlook, Portland, Oregon aka Swan Island prior to the industrialization of the 20th century and after it to the present day? Like flora and fauna. If not something about island ecosystems in the lower reaches of the Willamette River where it meets the Columbia. Again very specific, so I don't care anything about the ecosystem of Oregon in general only that specific region and if not only region similar to it on the islands of the lower reaches of the Willamette River where it meets the Columbia.--170.140.214.104 (talk) 16:20, 10 April 2013 (UTC)[reply]
Searching with the term "Columbia River Estuary" might help a little. The Columbia River Estuary reaches to Bonneville on the Columbia and Willamette Falls on the Willamette, and as a topic of study tends to focus on the ecology (present and historic) of the rivers and their many islands, wetlands, floodplains. I didn't search very hard, but some possible leads: This page, [7], the slides of some presentation, says the Willamette River was much shallower, with broader wetlands along it, and that apparently the main channel went east of Swan Island instead of west as it does today (the east channel is now just an inlet/lagoon). One of the slides shows the Swan Island area's bathymetry in 1888 and 2001, another changes in "off channel habitat". It also mentions (as do many other sources) how dam building on both rivers has radically altered the river flow (flow seasonality and freshet magnitudes are greatly reduced now—that is, water flow and river levels used to change dramatically over the course of the year, but now they don't much). And this page, [8], which among other things describes historical conditions at various sites around the Willamette-Columbia confluence. As with other sources, it mentions the historic abundance of Sagittaria latifolia (wapato) on the river islands around what's now Portland. Another thing you could do is look for sources on other islands in the area that are more likely to the kind of info you want. Sauvie Island comes to mind as one for which there's likely to be a lot of info. We have a few excellent/featured pages about wetlands and small streams in the Portland area, like Columbia Slough, Johnson Creek (Willamette River), and Tryon Creek. While these pages might not answer your questions directly, they might help give a general sense of things, and their reference sections might have useful sources to check. Pfly (talk) 08:05, 11 April 2013 (UTC)[reply]
well this is not very general but it technically does meet the requirements: the laser light–generated using a commercial laser–ionizes a small area of water, which superheats, creating an explosion of steam that generates pulses of sound waves at about 220 decibels.Gzuckier (talk) 20:02, 10 April 2013 (UTC)[reply]
The problem which you would need to overcome is that light is electromagnetic while sound is kinetic. I also doubt hooking up a speaker to a solar cell would produce any audible tone, unless you also hooking up a tone generator. Or, maybe you could put a fan in front of the solar cell so that it is covered and exposed at an audible frequency. but then you're still not really getting "light into sound", you're generating a tone using sunlight as the "carrier wave". In a more convoluted way, we turn light into sound when we speak :) Vespine (talk) 00:49, 11 April 2013 (UTC)[reply]
A cat placed into a sunbeam will often purr. I know, I know, not right. But what I'm trying to get at here is that the transformation of electromagnetic energy into acoustic energy is probably only accomplished through some sort of complicated intermediary, such a large biological organism. For non-biological approaches, maybe something like the crack of a melting iceberg? Again, not exactly what you're asking for. --Mr.98 (talk) 01:14, 11 April 2013 (UTC)[reply]
The simplest way I can imagine to go from light to sound would be a material with albedo that changes depending on temperature. As it heats up, it gets more reflective. This causes it to absorb less light energy and cool down. Once it is cooler it is less reflective and able to warm up more again. Then you would have to find a way to make the interaction happen quickly enough that the thermal expansion/contraction creates an audible noise. The overall system would need to be underdamped to be able to sustain the oscillation, and I'm not sure if that is possible. 38.111.64.107 (talk) 13:52, 12 April 2013 (UTC)[reply]
Bed bug feeding frequency
Every few days I wake up with a bite and I'm wondering whether I might have bed bugs. At some point I also had a rash around my jaw which I attributed to acne. I don't know when that was though. I'm wondering how long bed bugs could go without nutrition? If I go home (I'm a student), how long should I stay away to ensure bed bugs have all died? I haven't noticed any other signs though. It might be something else biting me. Playful spider perhaps. --2.97.27.107 (talk) 21:12, 10 April 2013 (UTC)[reply]
Have a look at Bedbug#Feeding_habits. It explains they prefer to feed every 5-10 days, but in some circumstances can last much longer, up to a year. As far as I know, adaptation to rare feeding is common in blood suckers, with some ticks and fleas reliably going several months without a fresh blood meal. Also note that bedbugs can "share" their meals, by piercing the stomachs of their peers and stealing their meal. If that sounds bad, it's just the start. Bedbugs also procreate though traumatic insemination! SemanticMantis (talk) 22:28, 10 April 2013 (UTC)[reply]
Unfortunately, if your bed bugs were mature and have laid eggs, you can't just wait for the adults to die. The eggs could be in the seams of your clothing, or your luggage, or anywhere in your bedroom. Have a look at the Bed bug article for other evidence to look out for before you take drastic measures. I hope the cause is something less persistent. Dbfirs08:23, 11 April 2013 (UTC)[reply]
hi there, I was wondering if there was a technique which would produce the synthesis (rather than the sequencing) of a specific strand of DNA with a known sequence? Presumably using its base nucleotides? Does it work? Would it work?
could you set up a basic but high yield automated process to carry out protein synthesis from the amino acids, even for longer & more sophisticated proteins?
I'm already familiar with PCR, selecting existing sequences or alleiles for amplification or expression invitro - I'm interested in synthesising very long strands or sequences which may not be found in nature.
Not only can it be done, it is regularly done these days. If you Google "gene synthesis" you can find companies that will do it for you over the internet. Like gene sequencing, the price has dropped dramatically over the past 10 years, though it is still relatively more expensive than sequencing. --Mr.98 (talk) 23:50, 10 April 2013 (UTC)[reply]
Rabies-like symptoms in ducks
A friend of mine was pursued by an aggressive duck apparently intent on attacking, in a manner described as being reminiscent of rabies. Only mammals have rabies, though; can any diseases cause rabies-like symptoms in ducks? הסרפד (call me Hasirpad) (formerly R——bo) 22:52, 10 April 2013 (UTC)[reply]
Not only mammals can get rabies, it can infect any warm blooded animal, including birds, however apparently birds have only been infected in experiments and not found in the wild. I saw a video on YouTube of a pelican eating a seagull and the explanation someone gave is that there is a rabies like disease that pelicans can get, so maybe it wasn't rabies, but something rabies like. In Australia, there is no actual rabies virus in the wild, but we are warned about fruit bats in particular because they can carry rabies like diseases. I just did a quick Google and it appears to be this Australian bat lyssavirus: closely related to rabies. Maybe there's something similar in birds. Vespine (talk) 23:51, 10 April 2013 (UTC)[reply]
Having said that, I also think you don't need rabies or any rabies like disease to explain an aggressive duck, maybe it was just an aggressive duck? There are plenty of aggressive dogs and most don't have rabies too. Vespine (talk) 23:53, 10 April 2013 (UTC)[reply]
Once, when sitting on the ground in a public park, I was mobbed by ducks that wanted my White Castle hamburgers. Deor (talk) 00:29, 11 April 2013 (UTC)[reply]
More or less. While I was fighting some of them off with my left hand, others managed to snatch a burger from my right hand. At that point, I gave up.Deor (talk) 10:44, 11 April 2013 (UTC)[reply]
Yes, land and waterfowl will nest in public parks. Yes, they can be very aggressive, especially given they nest on the ground. Swans have killed people and there are stories of rapes. Turkey attacks were a big item in NJ last summer in various municipalities. A girlfriend of mine was terrified of ducks, and she would murmur "the ducks... the ducks..." like the ending of Apocalypse Now. My younger sisters went to the Schuykill to feed the ducks popcorn and were attacked and bitten and left in tears. Male ducks gang up on and rape females, sometimes drowning them in the process. Remember, these little monsters are just velociraptors with beaks instead of teeth. μηδείς (talk) 17:45, 11 April 2013 (UTC)[reply]
perhaps you're right, whether it would be milliseconds or microseconds or days or what. I wondered if rapid rotation would play a role. But subatomic particles that decay in microseconds or less are still of interest in physics. i've also heard that very small black holes don't eat much, so i'm not convinced by the mere fact of of a LOT of [fluid or otherwise] mass pressing in on a black hole inside a neutron star would for sure cause it to take in all the neutron star's mass. If the black hole were small enough, i thought the "black hole evaporation" tendency could be roughly cancelled by the ready availability of mass inside the star.{to keep the black hole going, yet have the neutron star containing it exist for a "long" period of time}76.218.104.120 (talk) 12:28, 11 April 2013 (UTC)[reply]
Black hole evaporation ius one of those unproven ideas like gravitons, string theory, branes, etc. Much may be written but far less proof exists. Rmhermen (talk) 12:57, 11 April 2013 (UTC)[reply]
Thought I would check those intuitive answers with a back of an envelope, non-relativistic, much hand waving calculation. Assume that the rate of growth of the black hole is limited by area of its event horizon, the speed of light and the density of the surrounding material. Then in a "best case" scenario (or worst case from the POV of the neutron star) we have
where r0 is the initial radius of the black hole. If rt is much greater than r0 then we have
Taking a typical density at the centre of a neutron star to be 1018 kg/m3, then I make the time taken for the black hole to absorb the whole star to be of the order of 0.2 metre seconds divided by the initial radius of the black hole. For a millimetre sized black hole, this gives a timescale of minutes rather than milliseconds. Gandalf61 (talk) 13:16, 11 April 2013 (UTC)[reply]
Your calculation neglects the (very important) fact that the density around the black hole would not remain constant during the collapse. Dauto (talk) 15:59, 11 April 2013 (UTC)[reply]
Haven't looked up the paper yet, but I'd just point out a possibly very important consideration: All that mass going into the black hole is going to be accompanied by a truly spectacular release of energy. Maybe enough to blast away part of the neutron star? Don't know; it's not like I can solve the equations (or even formulate them) in my head. Does the paper take that into account? --Trovatore (talk) 16:19, 11 April 2013 (UTC)[reply]
Well, I hate trivial soundbite answers because they are so facile and uninformative. I didn't know that a black hole could absorb something as massive as a neutron star in milliseconds. Now I know that (a) yes it can and (b) the scenario has been studied in detail. So I have learned something. Gandalf61 (talk) 09:04, 12 April 2013 (UTC)[reply]
With respect to the OP, it doesn't matter whether you learned something does it now? Giving a concise answer takes priority over divergent exploration of related notions. Its only fair to first answer the OP's question, before endulging in such a manner of discussion. Plasmic Physics (talk) 09:40, 12 April 2013 (UTC)[reply]
Well, I certainly don't think the OP learned anything from your trite "Not indefinitely" response, beyond the fact that you couldn't be bothered to take their question seriously. Thanks to the further discussion, we know how long it takes for the neutron star to collapse, and we have an source for that information. Gandalf61 (talk) 10:34, 12 April 2013 (UTC)[reply]
Actually I learned a lot from all of you and I appreciate both Gandalf's and Plasma's help! I'll admit I did press for a yes or no which in past inquiries I have not always gotten, due to a delightful tendency(No sarcasm here, it's not just delightful, it's also educational)of refdeskers to go off on tangents. -Rich199.33.32.40 (talk) 21:42, 12 April 2013 (UTC)[reply]
8th dimensional space
so i was looking at 8th dimensional space page the quantum entanglement and alternate realities i need help to see if i am right
so pretty much 8th dimension is saying there our many universe like ours but different at the same time and if one were to get to one of these many dimensions it would cause a tear in space causing a new reality and if one travels though many tears it cause confusion in the universe meaning the quantum entanglement if my idea of what these are are wrong let me know plases — Preceding unsigned comment added by 99.12.149.156 (talk) 03:36, 11 April 2013 (UTC)[reply]
There is some confusion here. The word "dimension" has two meanings:
In the sense of "eight dimensional universe", the meaning is like "three dimensional universe" - we'd be talking about a universe where there are more directions you could move in than just the north-south, east-west and up-down that we are normally aware of.
In the sense of "travelling between dimensions" - we're talking about "parallel universes".
Generally, scientists only use the first of those two meanings. The two meanings of the word are not connected or related in any way.
When we are considering quantum entanglement and things like certain interpretations of the Schrondinger's Cat thought experiment - then we are talking about parallel universes...not extra spatial dimensions. "Tears" that allow you to move between parallel universes are in the realms of speculation and science fiction. As far as I know, there is no evidence that they might exist from mainstream physics...quite the contrary in fact...there is reason to assume that they'd be fundamentally walled off from each other.
When we're talking about "extra dimensions" in ideas such as string theory - then we're talking about "directions you can move in".
You're basically stuck in this universe - and whether there are others (due to quantum effects, for example) is an undecided question.
There is one more scientific usage of the term "dimensionality" - the usage in the sense of degrees of freedom in a generalized coordinate system. For example, if we are describing an n-body simulation, it is common to call this a n dimensional problem, (or even more accurately, a 6-n dimensional problem, for example, accounting for velocity and position of each object in conventional dimensions x, y, and z; by extension, you can add one dimension to each degree of freedom in the problem). When we generalize a coordinate system, we can apply constraints based on physical law, and reduce the complexity of the problem to a lower dimension.
In this usage of the term, it is frequently helpful to understand the distinction between the rank and the size of a problem-space. A problem can be n-dimensional, but modeled with extra dimensions; this is called "degeneracy", and it can be helpful for practical purposes, even if it adds no new information. Nimur (talk) 21:07, 11 April 2013 (UTC)[reply]
I recently bonded some rubber like swim fin material to itself and a glass fiber and resin material using a high quality cyanoacrylate with the manufacturer's 'filler' powder for plastics and rubber. Initially the bond seemed to hold but failed after several 20-30 minute uses on a swim fin in a chlorinated swimming pool. I am thinking that the bond may have been effected by residual chlorine compounds left on the surface prior to bonding. Other uses of the bonding product yielded exceptional results on similar rubber like materials where chlorine was not involved. Are there known adverse effects to bonding where chlorine compounds are present? What other chemical conditions might adversely affect bonding? Suggestions?
I don't see anything out there about reactions with chlorine - just about the only thing that I see might be that cyanoacrylate doesn't stick well to glass - so perhaps the glass fiber material is the cause here. That sounds like a bit of a stretch to me - but it's all I could find. SteveBaker (talk) 15:43, 11 April 2013 (UTC)[reply]
can you examine to see what failed? i.e. did the glue come loose from the rubber, or from the fiber/resin, or did the glue stick to both but deteriorate itself? my experience with cyanoacrylates and rubber is that it works very well (I use it to patch pinprick holes in bike tire tubes) but that hasn't involved immersion. re chlorinated compounds, stuff like chloroform is a good solvent for many plastics but whether that exists in enough concentration in a pool and/or whether it would attack acryclics, I don't know. Gzuckier (talk) 16:49, 12 April 2013 (UTC)[reply]
Perception of pain, which part of the brain is the gatekeeper?
I've always wondered how people can exert so much control over their perception of pain. If the stimulus is the same, the same sensory neurons fire and in the end the same regions in the brain get stimulated to an equal degree, then how is it possible to change your perception of pain, between the same stimuli? When I am on an operating table, unconscious, does my " body " still feel pain, even though I don't " know " that it is there? Can the part of my brain that is conscious effectively act as a signal limiter? Who is the gatekeeper? Has any research been done on this? 137.224.239.102 (talk) 08:45, 11 April 2013 (UTC)[reply]
Many aspects of pain are still very mysterious to us, and the answers to the questions really aren't known with any clarity. Part of the difficulty is that what we call pain is actually a mixture of several aspects -- Ronald Melzack identifies three that he calls "sensory-discriminative" (sense of the intensity, location, quality and duration of the pain), "affective-motivational" (unpleasantness and urge to escape the unpleasantness), and "cognitive-evaluative" (cognitions such as appraisal, cultural values, distraction and hypnotic suggestion). (Note: I've copied that from our pain article, which is worth reading.) Each aspect is implemented by a different brain system, and differently affected by brain manipulations. We are only beginning to understand the systems and their interactions. One thing that is clear is that there is a lot of "top-down" circuitry that allows higher brain levels to modulate signals at lower levels, even down to the spinal cord. Looie496 (talk) 15:42, 11 April 2013 (UTC)[reply]
Read:Dutch courage. Alcohol can depress some parts of the brain (as can some other drugs) that usually inhibit some forms of action. People that show the quality of having great will-power often have a low level of fear. Amphetamines were taken by the hand-full by American pilots during the second world war, because they did not only keep them alert but made them feel immortal and fearless, yet people may not survive very long with just that attribute. I think therefore, you may be asking about the type of will-power that brings successes. That requires a blend of other attributes. In that respect, I haven't come across any drugs that can have any long term benefit. Before anybody else steps in and pontificates, I'm not including Entheogens because these require the individual to also intellectualize (e. i., WORK) on seeking out whatever understanding they can glean from their experimental voyages. Will-power proper, I think, is a product of clear thought. Trying to think and carry out a plan of action whilst one's brain is under the influence of supposed artificial enhancements -will not achieve this. --Aspro (talk) 20:33, 11 April 2013 (UTC)[reply]
The question is ill-formed. There are various reasons besides akrasia that people lack the will power to do things--fear; lethargy; craving; compulsion. There are all sorts of drugs to treat anxiety, hunger, tiredness, OCD. So the broad answer is yes, drugs from caffeine and alcohol, to cigarettes and amphetamines, to xanax and zoloft all effect the mind. μηδείς (talk) 21:51, 11 April 2013 (UTC)[reply]
It's a good question, Medeis is being too glib about it. Although we usually think of willpower as a good thing... however it's probably better characterized as drive. In most mammal's evolution pleasure (or avoiding pain) and drive were yolked together, but in some instances, and especially when you start having fun with various plants, those two are distinct. There is a lot of really nuanced research on the subject... and then there's breathless articles comparing a book/movie to real life that center around modafinil. But also testosterone, amphetamines, and all sorts of other psycho active drugs affect motivation. It's quite complicated. Shadowjams (talk) 14:59, 12 April 2013 (UTC)[reply]
The basic problem here is that the concept of willpower is essentially dualistic. In terms of the "ghost in the machine" metaphor, willpower is the degree to which the ghost exercises control over the machine. But whenever one tries to understand dualistic concepts in biological terms, one runs into unsolvable boggles. Looie496 (talk) 15:37, 12 April 2013 (UTC)[reply]
Exactly, the question is based on the false assumption that there's some one thing called willpower and that a certain drug can turn its knob up higher. There are all sorts of reasons why one might fail to achieve a goal one has in mind. μηδείς (talk) 17:21, 12 April 2013 (UTC)[reply]
Launching yourself from lying on the ground to upright position using only your arms muscles
Are there people who can do this? I've seen people do so-called Muay Thai push-ups, so it seems to me that it is possible. It would require more strength than you need to do the Muay Thai push-ups, but then there are people who can do hundreds of these in a row. However, I've never seen or heard about people who can launch themselves up from lying to standing position using a push-up move. Count Iblis (talk) 19:17, 11 April 2013 (UTC)[reply]
I agree it looks suspicious. For example, just before the young man gives a big push to get up to the vertical, the bottom of his T-shirt rides upwards a couple of inches for no apparent reason. Now if the whole thing were actually performed in reverse and then played backwards, I can imagine the bottom of the T-shirt riding upwards as he fell forwards and downwards, and then extending to its proper position after he came to rest. Dolphin(t)08:16, 12 April 2013 (UTC)[reply]
It's beyond "suspicious"...it's an obvious fake, and a very poor one at that. YouTube demonstrations of any kind have to be viewed with deep suspicion - there are *FAR* more fakes than there are real demonstrations. SteveBaker (talk) 16:36, 12 April 2013 (UTC)[reply]
Since the article said white dwarf can be 0.17, do the white dwarf dwarf being 0.17 actually exist currently, or is it just the estimation of the stars did not yet come off the main sequence. Is this true alot of white dwarf are binary stars, can 0.5 solar mass white dwarfs? is it more common for white dwarf to be single star system, or binary star system? Is white dwarf all the exact same size on single star system/non-binary star ssytem? or the Solar mass determined by white dwarf has to determine exactly how big the white dwarf has to be?--69.226.42.134 (talk) 00:36, 12 April 2013 (UTC)[reply]
I struggle to see how a very small white dwarf (such of 0.17 solar masses) could form other than from a small red dwarf collapsing. Red dwarf stars live for a very long time, so none of them are dead yet. That would suggest there are no very small white dwarf stars. A lot of stars are in binary systems and they will generally remain in those systems when they die, so yes it is true that a lot of white dwarfs are in binary systems - I don't know if it is more than half, though. The size of a white dwarf is determined by the size of the star that formed it. In a binary system, there might be some transfer of matter between the stars that can change things. In a non-binary system, there obviously won't be. Does that answer most of your questions? I found them a little hard to understand... --Tango (talk) 11:43, 12 April 2013 (UTC)[reply]
Stars loose a substantial fraction of their original mass when they go through the late stage of red giant/Asymptotic giant branch and planetary nebula stage, so the white dwarf may end up much lighter than the original star. With that said, I have to say I don't really know what the lightest white dwarfs masses are. Dauto (talk) 19:09, 12 April 2013 (UTC)[reply]
Are the falcons, parrots, and sparrowsreally the closest relatives of one another, as people say? If so, who evolved from whom in this taxonomy? And also, if the falcons and the passerines are so closely related, which of the passerines are the most closely related to the falcons? (I'm guessing it would be the swallows, based on purely morphological info, but I can't be sure). Oh, and are the whippoorwills more closely related to the swifts, or to the owls? 24.23.196.85 (talk) 05:50, 12 April 2013 (UTC)[reply]
None of those groups evolved from another of them. Their most recent common ancestor was a member of neoaves but not of any of those groups (according to our articles). All falconiformes are equally closely related to all passerines. Regardless of which falcon and which passerine you pick, you get the same ancestral species as their most recent common ancestor. And according to our articles, whippoorwills are more closely related to swifts than to owls. Looie496 (talk) 06:43, 12 April 2013 (UTC)[reply]
(EC) You may be thinking of discussion surrounding some recent studies like [11][12][13][14]. You should be able to read both studies (the former may require free registration) and although they may be a little difficult for someone without a biological background to properly understand, you should get some idea and should also be able to view the various trees shown and seek help here to understand the parts which are confusing. The 2008 study (first 2 links) in particular was and is I believe regarded as fairly significant, you should be able to find a fair amount of discussion of it in blogs and other such sources, although looking for the better ones may be difficult, I think [15] is okay. As mentioned in our article Evolution of birds#Classification of modern species, this is still an area of some flux (as with quite a lot of taxonomy, particularly given the increasing ease of genomic analysis) and the 2008 study is obviously only about 5 years old although I don't know specifically how well the relationship between the species you mention is supported. I would note statements like 'who evolved from whom in this taxonomy' should generally be avoided when talking about extant species as neither extant species is going to be the same as the ancestral species. Similarly for statements like 'which of the passerines are the most closely related to the falcons' as most likely they all have the same most recent ancestral species. Nil Einne (talk) 06:51, 12 April 2013 (UTC)[reply]
Thanks! Maybe I should have put the question about "who evolved from whom" another way: which of the three orders (falcons, parrots and passerines) is the closest to their common ancestor, and which is the most distant? 24.23.196.85 (talk) 01:06, 13 April 2013 (UTC)[reply]
Most evolutionary biologists would consider them all to be equally distant from the common ancestor. That's because the usual way of measuring distance is time since the split. There are other possible measures, for example disparity between genomes (which can vary because there is some variability in rates of mutation). Even for that you would probably find that they are all at nearly the same distance, and it would be quite difficult to find out which is closest. Looie496 (talk) 02:19, 13 April 2013 (UTC)[reply]
I assumed the caption above was for the picture above--but please look at the hands (and the snout) and tell me if that looks like any great ape you've ever seen. The thing has effing flippers. Or am I missing something? μηδείς (talk) 12:59, 12 April 2013 (UTC)[reply]
A Google search provides images of chimp skeletons (also orangutans and gibbons). The hands in OP's picture are in the foreground and the phalanges of the left hand are splayed, which makes the hands appear larger, but the relative size does seem to be typical of a chimppanzee. The snout length and nasal opening do appear different than in other images of chimpanzee skeletons, but these are the only images I've seen recently, so I'm far from expert.--Wikimedes (talk) 19:39, 12 April 2013 (UTC)[reply]
So in other words the chimp is standing with his hands toward the camera, like this? I suppose that would explain the otherwise apparently freakish proportions. μηδείς (talk) 19:57, 12 April 2013 (UTC)[reply]
I suggested two types of motion, which are both wrong (now I know): random teleportation; and they exist everywhere at one in the form of an electronic fog, the mass and charge density profile of which is described by the schrodinger equation. Plasmic Physics (talk) 12:40, 12 April 2013 (UTC)[reply]
Periodicity figures strongly in quantum mechanical treatments of particle motion (basically to prevent particles from interfering with themselves), see for example particle in a box. Atomic_orbital#Orbitals_table has drawings of the shapes of probability distributions of single electrons of different energy levels orbiting a nucleus.--Wikimedes (talk) 19:13, 12 April 2013 (UTC)[reply]
Invasive species
Humans have invaded the entire planet, each and every continent, oceans, destroying all ecosystems and making other species extinct. They why humans are not considered invasive species? --Yoglti (talk) 16:53, 12 April 2013 (UTC)[reply]
the idea of invasive species is a matter of point of view, really. it's not like the biosphere of the earth is defined or has a defined goal. one species piggy backs on another and ends up in a new area and does well. doesn't matter if it's in the bilge of a ship or the large intestine of a dinosaur. but as far as being responsible for extinctions, we are definitely number one, i would guess Gzuckier (talk) 20:01, 12 April 2013 (UTC)[reply]
If knowledge, memories, thoughts, are just connections made in our brains, does that mean that knowlede has limits? I mean its possible that we might not even comprehend all there is to know about the universe?203.112.82.128 (talk) 17:52, 12 April 2013 (UTC)[reply]
Yes, you can only store a finite amount of information in your brain. You can't even know the exact state of your own brain, because that would require at least the full brain capacity while a lot of that is already in use to perform essential functions. Count Iblis (talk) 17:56, 12 April 2013 (UTC)[reply]
yeah, after studying a lot of philosophical basics lately (The Great Courses, better than my college humanities requirement) i've come to doubt not only that humanity is capable of understanding the underlying reality of the universe, but that there even is an underlying reality; as well as that humanity is capable of understanding the functions of "mind" as distinct from brain. Gzuckier (talk) 20:07, 12 April 2013 (UTC)[reply]
However, with the invention of writing, it became possible to store knowledge outside the brain. And, with the internet, we can now potentially quickly access all knowledge we have accumulated. Wikipedia, of course, plays an important role in all of this.
I like to think of knowledge like a program and data. The data can be stored outside the brain, with the brain just holding the program to use that knowledge. For example, say I want to determine the volume of a sphere. I access the data externally, to get the formula to calculate it. The formula is V = 4πr3/3. Now I use the program in my brain to determine that r means the radius and π means ≈3.14159 (or I look that up, if I don't know it already). I then use the program in my brain to tell me how to multiply, divide, and cube numbers, probably using a calculator. This is a very simple example, but we can potential solve much more complex problems in this manner. StuRat (talk) 20:21, 12 April 2013 (UTC)[reply]
I apologize but i think im looking for a different answer and its my fault because i didnt formulate my question well. What im trying to get into is, say a coin, there is only heads and tails, so there is just two outcome if you flip a coin, now go to our brains, there is just limited number of combination of connections in our brain right? Now my question is, given that the method on how we understand things are just one combinations of our connections in our brains, is it possible that there are certain data in our universe that we will never understand simply because its something that needs to be a set of connection that our brain is not capable of doing? for example, back to the coin, is there a data that niether heads nor tails can understand? Im not a native english speaker so please try to understand and thanks in advance. 203.112.82.1 (talk) 22:01, 12 April 2013 (UTC)[reply]
but that's the question; how is information stored in the brain? it's definitely not the way it is in computers. to me it seems to be more diffuse; i.e., you can forget what your grandmother looked like, but you won't forget that you had a grandmother, or that your grandfather was married, or that your mother had a mother, or what a grandmother is in general. it's like every concept/meme has a bunch of loose ends that tangle up with the loose ends of other concepts, somehow, in such a way that much of the structure assembles itself from what it connects to. as if you have a grandmother-shaped region in your model of the world, and even if you've forgotten or never had the memory of your senses in reference to your grandmother to fill in the hole, that grandmother-region still must exist and be referred to as grandmother by the rest of your mental world. so, what are the limitation of something like that in terms of finite number of neurons and synapses? well, you certainly can't know everything about the universe in perfect detail, i.e. the state of every subatomic particle, but that might be as much an effect of the finite amount of time you have to investigate than of your storage. Gzuckier (talk) 01:14, 13 April 2013 (UTC)[reply]
Tangentially related to this discussion are concepts like the Bekenstein bound and Bremermann's limit. The math and physics there is pretty dense, but the concept is sound: there has to be an upper limit to the amount of information we can store about anything, and how well we can retrieve it. We can't know the entire universe, because to store information about the entire universe would require an entity at least as large as the universe and separate from it. The entire field which deals with quantifying information, including its storage and retrieval, is known as Information theory, which in part deals with the very question of how much information can be stored in a given medium. For example, the theoretical maximum amount of information stored in your brain is constrained by the number of cells and synapses in your brain. Now, this theoretical limit is probably orders of magnitude more than the functional limit, but it's a starting point, and indeed, is a subject which is well studied and explored, if you have the time to research it and the ability to weed through some fairly arcane mathematics. --Jayron3205:30, 13 April 2013 (UTC)[reply]
Stud finders
Looking at the reviews of stud finders on Amazon, all of them have mixed reactions. Some people say they work as they should and others say they don't. I'd like a stud finder but would like one on which I can rely. Are some people just using them wrongly? Some people say they're inconsistent. --2.97.27.107 (talk) 17:54, 12 April 2013 (UTC)[reply]
They are many types of walls and a few types of stud finders. Most work fairly well on modern drywall (plasterboard)-type walls. But on my old over-an-inch thick plaster/gravel/horsehair on metal lath walls, none ever work. Rmhermen (talk) 19:05, 12 April 2013 (UTC)[reply]
I've tried out maybe 4 or 5 different types over the years, both the magnetic (looks for nails) kind or the electronic (capacitance I assume) kind, not any of them worked any better than just pounding on the wall and listening for the change in sound. Gzuckier (talk) 20:09, 12 April 2013 (UTC)[reply]
Drilling exploratory holes with a really thin drill bit is another strategy, the idea being that the holes are so tiny you can patch or cover them easily and they will never be noticed by most observers. HiLo48 (talk) 23:05, 12 April 2013 (UTC)[reply]
Studs are also spaced a standard distance apart, usually, so once you've found one, a ruler is usually helpful. In most houses, electrical outlets and switches are required to be in junction boxes which are bolted to a stud. In the United States, the standard is 16 inches center-to-center between studs. So, if you start at the wall switch, find the stud it is attached to, then measure off 16 inches, you should find another stud. And so on. --Jayron3203:55, 13 April 2013 (UTC)[reply]
Upon eclipsing a population of 1,500, a number considered to be the minimum required for the survival of a race, Angam Day was declared.
Does a race really need a minimum population of 1,500 to survive? If true, why? If false, how many people does a race need to avoid extinction? Thank you in advance. --190.19.69.254 (talk) 04:33, 13 April 2013 (UTC)[reply]
Hmmmm. That's a pretty ugly part of that article. I would much prefer that the term ethnic group had been used throughout. Race is an unclear word with unfortunate connotations. The article Nauruan people, linked from Angam Day, avoids the term race completely. I note that the claim of 1,500 being the minimum number for a race to survive is unsourced. That's not good, and only makes things worse. I went hunting and couldn't find a source myself. You've got me thinking about what we should do with the article. HiLo48 (talk) 04:54, 13 April 2013 (UTC)[reply]
Reads like unmitigated bullshit to me. What makes an ethnic group (or race) a distinct unit is a shared culture. I'm not sure there's any arbitrary lower or upper limit on that, merely that the group has a certain level of cultural cohesion and distinctiveness, and I certainly can't find any literature that indicates that there's some official or "scientific" or whatever reason that would indicate that 1500 is some magic number. --Jayron3205:00, 13 April 2013 (UTC)[reply]
The article clearly states that the number 1500 came from Brigadier General Griffith, the Australian administrator. It does not claim that the number has any deeper validity. It doesn't cite a source for that, but I don't see anything implausible about it. Looie496 (talk) 05:17, 13 April 2013 (UTC)[reply]
The article makes that assertion, but that assertion (nor the quote from Griffith) has any sources to support it. The big issue is if Griffith said directly, "if the Nauruans were to survive as a race, the population should be no less than 1,500.", then we would need to put quotes around that, as I have done, and provide a footnote to make it clear where the quote comes from. Without sources, the statement really shouldn't stand, however. --Jayron3205:22, 13 April 2013 (UTC)[reply]
Seasonality of human hair growth
My friend, in her early seventies, is convinced that her hair grows more quickly in the Spring and more slowly in the Winter. Her evidence for this is the much shorter length of time it takes for white roots to appear after she has dyed her hair. (I have no reason to doubt her eyesight.) This sounds like folklore to me but I can find nothing to indicate that anyone has ever studied the matter. Thank you for your help. — Preceding unsigned comment added by 109.12.63.61 (talk) 07:24, 13 April 2013 (UTC)[reply]
This is an interesting question, as it is one of the few topics on which I think the written word does not match reality. If you google (google "rate of hair growth") or search in textbooks, you find almost all estimates lie in two categories: Those which say hair grows at a constant rate of 0.5 inch (13 mm) per month no matter what (the Wiki article human hair growth is one example), and those that say it varies depending on age, health, intake of certain vitamins, race, and a few other minor factors and is between 7 mm and 20 mm per month, which seems much more likely. What seems difficult to find is any refrence that says it varies depending on where on the head it grows from, and there's no reference that says it is seasonal, depite the fact that it most definitely IS seasonal for other mammals. Hairdressors are taught that it grows at a constant rate.
However, in my experience, it grows considerably faster on the back of my head and neck, and a lot slower on the top of my head. It also grows quite a bit faster in autum and slowly during winter. This is reflected in when I need to go to the hairdressor. I'm also in my seventies. I'm sure that it grew faster when I was younger, but suspect that the variation in growth rate was hidden when I had a younger thicker hair.
In my experience, cutting hair very short and cutting frequently casues it to react by growing faster. However hairdressors are taught that that is a fallacy. I had a friendly argument about it once with a hairdressor friend, so I experimented over a two year period, keeping records. I was right. However, I live in a hot climate, and cutting hair short probably raises skin temperature. If I lived in a cold climate, it may well be that cutting hair short would lower the skin temperature and therefore the growth rate. This suggests a conflict between two factors: skin able to grow hair faster when it is warm during warm weather, and the evolved capability of mammals to grow a thick winter coat in time for winter.
Don't fret too much. It grows so slowly on top, and so thinly, it might as well not bother. But I still need to have it cut from time to time. Wickwack 121.215.67.60 (talk) 08:54, 13 April 2013 (UTC)[reply]
![[9]](http://www.goldfinity.com/images/Classic%20Box%20Chain.jpg){kind=link}
![[12]](http://www.sciencemag.org/content/320/5884/1763/F4.large.jpg){kind=link}
Resolved