Wikipedia:Reference desk/Archives/Science/2010 April 10

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April 10

Flower unknown

What flower is this? --Tyw7  (Talk • Contributions)   Changing the world one edit at a time! 00:08, 10 April 2010 (UTC)

Well, it looks to me like the picture title is correct in calling them Bluebells. To my eye they look very similar to the picture in the Hyacinthoides article. Looie496 (talk) 05:14, 10 April 2010 (UTC)

I agree, it looks like a bluebell. 78.146.60.36 (talk) 10:12, 12 April 2010 (UTC)

onion skin layers

Is the core of the melted or even the solid part of the Earth's core layered somewhat like an onion with heavier elements occupying deeper layers and if so could layers consisting of radioactive isotopes release massive amount of energy from decay or fission in instances of mass beyond the critical mass so as to be responsible for the giant blob of lava that surfaced beneath Siberia 250 million years ago and destroyed the atmosphere and made most things go extinct? 71.100.3.207 (talk) 00:35, 10 April 2010 (UTC)

No. It gets continually mixed up by thermal convection, so radioactive isotopes never get nearly that concentrated. Thermal convection also occasionally brings up hot magma to near the surface, causing volcanism of various degrees. StuRat (talk) 00:41, 10 April 2010 (UTC)

The georeactor hypothesis posits that there is such a natural fission reactor of concentrated heavy elements in the core of the Earth. This is generally considered unlikely by nearly all Earth scientists. Dragons flight (talk) 03:11, 10 April 2010 (UTC)

However, the Earth's crust does have layers that are not necessarily organized by mass, see stratum. ~AH1^(TCU) 03:18, 10 April 2010 (UTC)

Hijacking the question somewhat, does this extinction event have an article? Vimescarrot (talk) 08:53, 10 April 2010 (UTC)

http://en.wikipedia.org/wiki/Siberian_Traps. —Preceding unsigned comment added by 66.133.196.152 (talk) 09:11, 10 April 2010 (UTC)

Thanks. Vimescarrot (talk) 11:43, 10 April 2010 (UTC)

Note that forming a critical mass is difficult even under ideal conditions. Mixing up even just pure amounts of uranium ore will not result in an explosion, ever. There are, however, evidence of localized natural nuclear fission reactors—see Oklo. But they could not explode. --Mr.98 (talk) 14:40, 10 April 2010 (UTC)

Food additives

Why do they add so many artificial chemicals to food? If you look at a food label, often up to half of the ingredients (sometimes even more) will be things with long chemical names which are mostly incomprehensible to anyone without serious chemistry background. Why can't they just stop using them, instead using only the real, natural ingredients? --70.129.184.122 (talk) 00:51, 10 April 2010 (UTC)

They can, and some companies do, like Breyer's Ice Cream. However, most consumers don't seem to care, so most companies don't care, either. Also note that some of those "long chemical names" are just vitamins and such, but a few really are as nasty as they sound. StuRat (talk) 00:57, 10 April 2010 (UTC)

You're wrong that they don't care. It's just that, for obvious reasons, the price is much lower when more than half of your concoction is industrially produced chemistry sourced from giant vats rather than hard to harvest individual pieces of whatever. So it's just that some people care more about the price. 82.113.121.36 (talk) 02:39, 10 April 2010 (UTC)

What are "real, natural ingredients"? With the exception of some raw fruits and vegetables, we rarely eat things in their natural form. Many things are cooked which alters its chemistry, dramatically in some cases. Items like sugar and wheat flour are highly processed derivatives used in forms that have few similarities to the plants they came from. Many of the complicated chemical-sounding ingredients are like sugar and flour in that they are highly processed food derivatives. Others, like the baking soda used in much baking, are generally created in chemical vats because is is cheaper and more uniform to produce it that way than to extract it from natural analogs. Highly processed ingredients have advantages for bulk food manufacturers because using these ingredients provide more uniformity and avoid variations that can occur with natural products like fruits and vegetables. In many cases the processing also kills or removes potential pathogens like bacteria that may hide in unprocessed foods. Often highly processed foods last longer, can be produced in greater quantities, and are less likely to spread disease than traditional foods (though in some cases the ingredients are later found to have other problems like causing cancer or affecting hormone levels). On the other hand processing also runs the risk of excluding natural substances present in raw foods whose value may not have been recognized. And of course, many people seem to feel natural foods taste better, even though many of the additives are also there in attempts to affect taste or texture. Dragons flight (talk) 03:08, 10 April 2010 (UTC)

The original poster didn't give any reason why companies would want to make such a change. Every ingredient in a product is there for a reason -- it contributes to the flavor or the color or the texture or it improves the shelf life or whatever. --Anonymous, 03:05 UTC, April 10, 2010.

See also trans fat, sodium benzoate and monosodium glutamate. ~AH1^(TCU) 03:15, 10 April 2010 (UTC)

To answer the original OP's question without perjorative, the reasons why chemical additives are added to foods are many. If we isolate them into types of additives, you can get the following sorts of categories:

• Chemically identical, but manufactured versions of, natural compounds (generally things like artificial flavors and vitamins and things like that)
• Completely unnatural additives which improve the appearance or texture or flavor of food (things like emuslifiers, artificial colors, artificial sweeteners etc. etc.)
• Compounds designed to preserve shelf life of foods.

That's probably covers most of the bases. The first category is there for two purposes. Making flavors in a giant vat is cheaper than extracting the same flavors from natural sources. And vitamins are often added back into heavily processed foods because the processing tends to remove them. For example, white bread is enriched because the germ and bran contain most of the vitamins in grain. Low-fat milk (but not whole) has added Vitamin A, because vitamin A is fat soluble, and in removing the fat, lots of vitamin A is removed, so it has to be added back. The second category covers making food look or taste more appealing. Cheerios are kinda boring looking, but man the kiddies really prefer the Froot Loops with all of those wild colors. The third category is probably the most important. Ever buy a loaf of fresh made bread? It goes green in about 4 days, and that's in the winter. On a humid summer day, you're lucky to keep it until tomorrow. Ever wonder why bakeries practically give away "day old" bread for free? Cuz in another day or two it starts to go. Now, ever wonder why factory-made bread can keep for like 2 weeks? Most of those unpronouncable chemicals are why. So, if you will go through a loaf of bread in a day or two, the fresh bread is fine. But if you are like most families, and your gonna make like 2 sandwiches a day with it, then having a loaf go bad a few days after you buy it is wasteful and inconvenient. Not saying these are all good reasons to have all of these chemicals, but they are the reasons nonetheless. --Jayron32 04:50, 10 April 2010 (UTC)

I feel that I should point out that natural does not necessarily equal good, and unnatural does not necessarily equal bad. Most crop plants have been artificially selected for all sorts of traits, which is a good thing, because most of the time it is not to a plant's advantage to be eaten (excepting certain kinds of fruit), therefore many plants tend to be poisonous, distasteful, or nutritionally poor in their "natural" forms - would you like to eat natural maize? (the one on the left). What I do agree with is that companies don't always make it clear what the food additives they are using actually are - which is a problem, since some are very bad for you (trans fats), whereas some are actually good for you (E300, aka vitamin C). 131.111.185.75 (talk) 09:04, 10 April 2010 (UTC)

The natural maize on the left in the pic just looks like it hasn't grown any corn, yet. StuRat (talk) 12:24, 10 April 2010 (UTC)

Does that mean you'd like to eat it? Do note that that's about as good as it gets. It doesn't 'grow' any 'corn' Nil Einne (talk) 15:59, 10 April 2010 (UTC)

Isn't the corn the seed ? How can it reproduce if it doesn't grow any seed ? StuRat (talk) 16:37, 10 April 2010 (UTC)

What do you mean? That is the seed you're seeing. Haven't you ever seen grass seed before? Edit: Perhaps [1] & [2] will help Nil Einne (talk) 16:44, 10 April 2010 (UTC)

The middle pic seemed to show both corn and the green things, which I took to be what grows into the corn. So, you're saying that the left pic is fully fertile even without growing any corn ? Ok, I see. StuRat (talk) 17:15, 10 April 2010 (UTC)

Urgh. Stu, just see Teosinte, which is the wild ancestor of Maize. The entire fruiting portion of the teosinte plant is about a centimeter in size, while you know how big an ear of corn is. The point is that, through hundreds of years of selective breeding, mesoamerican farmers were able to produce modern Maize from Teosinte. They are the same species of plant, but careful breeding (i.e. unnatural processes) created the modern food plant. Maize may itself be one of the most important food crops in all of history, and if we asked for people to live solely on "natural" or "wild" foods, i.e. taking the natural foods movement ad absurdum to its ultimate conclusion, it seems fair to say that the entirety of civilization could not survive. That is the point of what is being said above. --Jayron32 18:48, 10 April 2010 (UTC)

I don't know how you would separate natural selection from artificial, in the case of early humans. If they ate the better food, and their feces thus contained seeds that grew more of that food, and it therefore spread, is that natural or artificial ? StuRat (talk) 21:04, 10 April 2010 (UTC)

That isn't how teosinte became maize. It was selectively bred by deliberate human intention. The same way that a wolf became a chihuahua. That's the point. Neoluddites who don't want anything "artificial" or "manmade" in their food should keep in mind that almost nothing we eat isn't manmade; that all of our food exists because humans deliberately made it that way; there's almost nothing in the Western diet which is "natural". --Jayron32 03:56, 11 April 2010 (UTC)

Not all artificial chemicals are harmful. The benzoates and propionates are preservatives. They are harmful in large quantitities. Silicon dioxide is added to prevent clumping. It is another form of sand, which is harmless. Alum and sodium aluminum sulfate are leavening agents found in baking powder. Sulfates are used to make a better texture. Those are a few of the classes. --Cheminterest (talk) 19:48, 14 April 2010 (UTC)

Paddle is moving and stationary at the same time: parallel universes????

What would the paddle look like when it is "moving and stationary at the same time?" What is the upper limit on mass or size for this claimed effect to apply? [3]. Edison (talk) 02:19, 10 April 2010 (UTC)

You might want to read this. The actual paper is here. Not having read it yet, I gather they put a fairly large object into a superposition of the ground state and the first excited vibrational state. I don't know what's new or interesting about that. I thought phonons in solids were old hat. -- BenRG (talk) 04:37, 10 April 2010 (UTC)

"Here we use conventional cryogenic refrigeration to cool a mechanical mode to its quantum ground state. We achieve this by using a micromechanical resonator with an isolated mechanical mode near 6 GHz, which we term a microwave-frequency 'quantum drum', whose ground state is reached for temperatures below ~0.1 K." So they cooled a tiny object below 0.1 K, which because of its special resonant properties happens to leave it in the ground state with high probability. Meh. More interesting is that they can transfer the vibrational states to and from a separate qubit (|ground〉 ↔ |0〉 and |first-excited〉 ↔ |1〉, or something like that), and do measurements on the qubit. So I guess they are actually measuring the superposition state—they're not just doing an energy measurement and then claiming for no good reason that the system was in an energy superposition before the measurement, as I had cynically assumed.

Anyway, it looks like an interesting paper but it has approximately nothing to do with that Fox News article. There's no theoretical size/mass limit for this kind of thing—any object left in a perfect vacuum for long enough will eventually radiate all its energy and end up in a ground state—but practically speaking you're limited by refrigeration technology, about which I know very little. These low-energy vibrational modes are basically Fourier modes, and superposition is basically... superposition. If you decompose a wave in a solid into Fourier components and it's a sum of more than one, that's a superposition of those modes. Your intuition from classical wave mechanics won't lead you too far astray here. What makes this system interesting is that it's almost not in a superposition of energy modes. -- BenRG (talk) 08:34, 10 April 2010 (UTC)

If the object is in superposition - and you "observe" it - doesn't it just collapse into either one or the other state? If so, then the answer to the first part of the OP's question ("What would the paddle look like...?") is that it will appear to (boringly) either vibrate or not vibrate. Schrödinger's cat explains this. The whole point of the cat thought-experiment is that there is no upper size limit on this kind of thing - and the argument that the (typically sensationalist) FoxNews article makes for this being a proof of the parallel worlds hypothesis is that the entire universe is in superposition as a result of this. If you accept that interpretation (and it seems like the best choice to me, personally) - then this isn't really big news. There are many interpretations of the 'meaning' of superposition - this experiment doesn't 'prove' any one or another - so the Copenhagen interpretation could still be the correct one. So (surprise, surprise), the FoxNews article is incorrect. SteveBaker (talk) 12:26, 10 April 2010 (UTC)

"They report, we decide." Thanks. Edison (talk) 12:51, 10 April 2010 (UTC)

For some strange reason, macroscopic superpositions in momentum space are not considered to be interesting Count Iblis (talk) 21:15, 10 April 2010 (UTC)

Brain simulations

Does Henry Markram publish his source code (not that I could run it)? If so, where? I think I once saw an (open source maybe?) project that tries to simulate a single neuron. Can anyone point me to that? 74.14.108.102 (talk) 04:34, 10 April 2010 (UTC)

Source code for what project? He's been involved in a bunch of things. And there have been literally thousands of projects simulating single neurons, with dozens at least based on open source code. The NEURON simulator developed by Michael Hines is one of the most widely used; see the NEURON site for more info. If that doesn't meet your needs, you'll probably have to be a little more specific about what you want to do in order to get a more useful answer. Regards, Looie496 (talk) 05:02, 10 April 2010 (UTC)

Thanks for the link. As for Henry Markram, i guess I would be interested in anything he does, but the Blue Brain Project (an article which I now see mentions the NEURON simulator) is the one I've heard of. 70.26.154.114 (talk) 19:01, 10 April 2010 (UTC)

Chrome plating

what type of metel is used under the Chrome plating for bathroom faucets? is it nickel? if so wouldent deep scratches or pits expose the nickel and cause dermatitis? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 04:38, 10 April 2010 (UTC)

What makes you think metallic nickel causes dermatitis? You've prob'ly shaved with nickel-plated razors on a regular basis (either your face, or your legs and armpits, depending on your gender -- though based on your user name, I think you prob'ly shave your face rather than your legs). Anyway, in both these cases, the skin comes into direct contact with the nickel plating on the blade, and in most people it doesn't cause any problems (or else they would've had to stop using nickel plating for the razor blades). 24.23.197.43 (talk) 06:04, 10 April 2010 (UTC)

Just checked out the nickel article -- it says that only those people who happen to have sensitivity to nickel can develop dermatitis from it (and that's only a small percentage of the population). The vast majority (including me) have no problems whatsoever with nickel. 24.23.197.43 (talk) 06:10, 10 April 2010 (UTC)

In some cases, or course, "Chrome plating" is real chrome, also a possible cause of allergic reactions, but when it is nickel (often satin or brushed), it is no more dangerous than handling cupro-nickel coins. People who have a serious allergy to nickel should probably choose an alternative finish - perhaps gold? Dbfirs 06:34, 10 April 2010 (UTC)

In most cases copper is used as a intermediat layer before the chromium is plated onto the material. Nickel is also used sometime. The direct deposition on bras seems not to work properly. Your kitchen wear, cutlery, pots and pans made from stainless steel are 8 to 10% nickel. You touch it every day and you have no problem with it so you will have no problem with your bathroom faucets. One point were it is different is with cheap jewlery or rivets in jeans, these materials are normaly plated with gold, chromium or other metals and there nickel is used as intermediat layer. This stuff is in contact with your skin for hours and with a little bit of sweat nickel can be set free and cause problems.--Stone (talk) 08:40, 10 April 2010 (UTC)

Now I have an image of a pointy, chrome-plated bra; makes me think of Wagner operas with fat women. StuRat (talk) 12:18, 10 April 2010 (UTC)

Atkins diet for small children

I was surprised when, years ago, I learned that the average adult human and late adolescent can subsist quite well on few to no carbohydrates. Does this extend to small children (disclaimer: I am not seeking advice on putting a small child on a diet). From a physiological perspective, do small children, babies or pregnant women have any nutritional need for carbohydrates that can not, in a healthy manner, be fulfilled by converting fat and protein? Thanks. Someguy1221 (talk) 06:26, 10 April 2010 (UTC)

Being a long-term dieter (now retired), I can say with some certainty that every diet has included a requirement for a multi-vitamin tablet daily, even the Atkins diet required this. As an example, a high-fat diet would not supply any vitamin C, which is vital to consume as the human body doesn't manufacture it. So if adults need nutrients which are not available on a low-carb diet, then it would make sense that all humans would, and especially those in the groups you mention. --TammyMoet (talk) 08:15, 10 April 2010 (UTC)

You really shouldn't put small children on any kind of a diet without consulting a doctor...especially a radical diet like Atkins. You can do great harm (including long-term harm) by screwing with a childs' nutrition. SteveBaker (talk) 12:06, 10 April 2010 (UTC)

See ketogenic diet. A no carb diet can be done carefully for certain serious disorders (usually intractable seizures), but growth needs to be monitored. The purpose of a no-carb diet is to turn off insulin, but remember that for children insulin is a growth hormone. Extremely low insulin levels for prolonged periods during the adolescent growth spurt can blunt growth and cost height. alteripse (talk) 14:26, 10 April 2010 (UTC)

I'm a nutritionist and SteveBaker is right, you should NOT put a child on any kind of a abnormal diet (like atkins or "the zone") without consulting with a medical doctor or a registered dietitian.--FUNKAMATIC ~talk 03:05, 14 April 2010 (UTC)

Unknown Caterpillars

Are these Ochrogaster lunifer?

Hi there, I added a pic to Ochrogaster_lunifer of the cluster of Caterpillars. I'm now having doubts about the correctness of my identification as the pic I took seems to show blacker Caterpillars than the other pics in the article. This was near the Porongorup National Park, in the south west of Western Australia. Any thoughts? Thanks. SeanMack (talk) 10:41, 10 April 2010 (UTC)

A Google images search on "Ochrogaster lunifer" turned up pictures of both the very light colored and almost-black colored caterpillars...so on that (somewhat 'iffy') evidence, I'd suspect your photos are OK. On the other hand, this website says that the adult moths come in more than one color and says that "...the variety of colour forms suggests that there may be more than one species present in Australia." - and I suppose that this variation could easily extend to the caterpillars too. It links to this abstract on interscience which is highly relevant to this question. I would say, based on that article, that Ochrogaster lunifer should really be two separate species - which are presently mis-characterized as one. But one paper may not be enough to cause a re-characterization - and that makes it hard to know what to say in the Wikipedia article. I strongly suggest you take this discussion to the Talk: page for the Wikipedia article. SteveBaker (talk) 12:02, 10 April 2010 (UTC)

Lepidoptera has almost the most amount of species of any other order in the world so identifying them to species, even if you're a Ph.D. that exclusively studies their genus, may be a mistake. It may be easy to do this for carnivorous mammals or conifers, but it just something you can't do with Lepidopterans and other specious insect orders.--FUNKAMATIC ~talk 03:11, 14 April 2010 (UTC)

Bird deads, causes unknown

Hi all,

I'm in Brampton, Ontario, and three birds have died with no visible cause of death. On Thursday morning, we found a North American Robin in the backyard, and this morning, a male and a female yellow-bellied sapsucker in our driveway, literally lined up next to each other.

• there's no mosquitoes at all, so it's not West Nile,
• it likely wasn't a bird of prey or cat, there's no visible signs of trauma, and the spines seem solid, not cracked,
• all were found far enough away from windows, that it's unlikely that they hit.

I've contacted the Ontario Ministry of Environment, via email, to see if they're concerned. What would it be? There's always the option of a neighbour setting out poison, but is there anything else? -- Zanimum (talk) 13:00, 10 April 2010 (UTC)

Bird flu ? StuRat (talk) 13:06, 10 April 2010 (UTC)

That's what we're worried of, but there's no reports yet in Canada. -- Zanimum (talk) 14:18, 10 April 2010 (UTC)

I've heard of birds and other animals eating fermented fruit and dying as a result of the intoxication. Beach drifter (talk) 13:38, 10 April 2010 (UTC)

Would this include fruit in open compost containers. Our are closed, but others might have open ones. While we've had above seasonal temperatures in the area, we're back down to just above freezing, no fruits are in season -- the buds haven't even opened yet. Only parsnips could be in the ground currently. -- Zanimum (talk) 14:18, 10 April 2010 (UTC)

I would say that intoxication is an unlikely explanation. Diseases are easily spread between birds, and some are fatal (to birds, not to humans). Your suggestion of carelessness with rat poison seems a possibility. Dbfirs 19:38, 10 April 2010 (UTC)

We cannot provide epidemiological or public health advice, naturally. A die off like you describe is what we saw when West Nile came though, although you claim "no mosquitoes." It sounds abnormal for that many birds in a small area to be found dead without physical trauma, and you might wish to contact the local health department in addition to the environmental folks you already emailed. The dead birds might be a hazard if handled if they have disease. If they ate or drank something toxic or poison, they might be a hazard to pets who find them. Edison (talk) 19:45, 10 April 2010 (UTC)

Or maybe there's a gas leak nearby ? Birds seem to be a lot more sensitive to that than us. StuRat (talk) 20:59, 10 April 2010 (UTC)

Which is why miners use canaries to detect methane. 24.23.197.43 (talk) 02:07, 11 April 2010 (UTC)

There goes my theory that they were used to add accent colors to those drab old mines. :-) StuRat (talk) 03:49, 11 April 2010 (UTC)

Where I live there is a department of health (or something like that) which actively solicits reports of dead birds of unknown cause (they are monitoring for bird flu). Perhaps there is a comparable agency where you live. Also check with your local university. Ariel. (talk) 06:37, 11 April 2010 (UTC)

There is a far more common reason for death, senescence. Although this doesn't seem like a coincidence, it might be.--92.251.143.238 (talk) 20:29, 11 April 2010 (UTC)

Do you have any kids with blow-guns next door?--FUNKAMATIC ~talk 03:13, 14 April 2010 (UTC)

How power stations deliver electrical energy to my home

I'm trying to understand live and neutral and how power is transmitted. I recall once reading that overhead powerlines are all live, by which I intend to say that they are all pushing and pull current in union, and no voltage difference occurs between them, and that the return occurred via the earth. Is that correct? Does this mean that all power stations which are connected into a single grid need to be in phase? Otherwise, one power station in location A, 100 km from a power station in location B could be pushing current through earth while that in location B is pulling current and that would have implications unfathomable to the human mind. The neutral in my domestic power supply... is it connected to earth and if so, where? --84.13.85.158 (talk) 15:48, 10 April 2010 (UTC)

The three phases are 120 degrees out of phase, so, on average, they cancel out. In practice, this seldom happens exactly, so there is often but not always a small neutral or common return wire as well. The supply voltage is between the conductors on a three-phase supply (large overhead powerlines), but this means that they are all at different voltages to earth at any one instant. Yes, it is essential that any generator is in phase before it is connected to the grid, though it would soon be forced into phase by very large currents if it wasn't! The neutral at your house is created at the last step-down transformer by bonding one side of the output winding to earth, and this earth bonding is usually repeated at your house (depending on where you live). See Three phase electric power for details. Dbfirs 15:55, 10 April 2010 (UTC)

Note that many long-distance power lines are carrying high-voltage direct current, with AC conversion closer to the consumers (regional systems but not the "last mile"). For example, the UK-to-France grid connection is DC. Here's a link to the history of DC links [4]. NVO (talk) 16:12, 10 April 2010 (UTC)

As to your question of "how they keep the phase locked" ... we have <quite sketchy> articles on Wide area synchronous grids and the Synchroscope, the antique device that still works ... NVO (talk) 16:24, 10 April 2010 (UTC)

I think the DC lines are quite rare and used only for long-distance transfer of power, not for distribution. See our article on High voltage direct current.
On synchronisation, I think that keeping in phase is almost automatic as long as the generator is running properly because if it lags behind it will become an electric motor, drawing power from the grid (and possibly being damaged if it lags too far). Obviously it is essential for the frequency and phase to be synchronised before connection. I assume that there is an automatic disconnection if something goes wrong. Our article might be improved by explaining this. Have we any electrical engineers? Dbfirs 16:32, 10 April 2010 (UTC)

A picture (or in this case a meter) paints a thousand words.[5]--Aspro (talk) 18:12, 10 April 2010 (UTC)

That's brilliant! Smart devices to switch off the load at high demand must make life much easier for the grid engineers. Was I correct in assuming that individual generators are automatically synchronised by the grid once they are connected? I know that mains electric clocks are less common these days, but do the engineers still ensure that the time-average frequency is exactly 50 Hz? Dbfirs 19:01, 10 April 2010 (UTC)

Yes. Pieter-Tjerk de Boer's web page answers your next question better than I can. As the grids got bigger and bigger extra refinements were built in to the system though. Maybe the following link could be added to the appropriate article, because it goes into some detail of the European system but I can’t find the time right now. Load-Frequency Control and Performance Policy--Aspro (talk) 20:42, 10 April 2010 (UTC)

Thanks for the interesting links. Dbfirs 07:36, 11 April 2010 (UTC)

nuclear waste

Is it possible to drill a hole deep enough to use the Mantle as a place to dispose of nuclear waste? 71.100.3.207 (talk) 16:08, 10 April 2010 (UTC)

You might be interested to read our article on Mantle_(geology), especially the exploration paragraph, but I will leave it to an expert to comment on the practicalities of putting nuclear waste down there. Dbfirs 16:19, 10 April 2010 (UTC)

Bad idea. The pressure down there would cause the nuclear waste to erupt back up. StuRat (talk) 16:28, 10 April 2010 (UTC)

Yes, I was worried about that, but how do they avoid creating a volcano when they explore the mantle? Dbfirs 16:46, 10 April 2010 (UTC)

We don't explore the mantle, at least not by drilling holes into it. StuRat (talk) 17:11, 10 April 2010 (UTC)

When drilling very deep wells (typically looking for petroleum), most of the pressure at depth is kept at equilibrium by the hydrostatic head. In other words, your bore hole is full of fluid - drilling mud. That fluid has weight (a lot of weight, if you're drilling 20,000 feet). The effect is a very high pressure that counteracts most of the pressure at depth. However, because of geology and geochemistry, it is possible to drill into a region where the pressure is higher than hydrostatic equilibrium. This often happens as pressure builds up over time, usually by the physical and/or chemical release of gas or fluids from rock pore spaces, or thermal contact which changes the equilibrium pressure. If the reservoir is sealed, the pressure is much higher than it "should" be, and drilling through the seal rock releases it geyser-style. (This is what you see in stereotypical oil spout photographs, and is a sign of poor drilling engineering. To fix and/or preempt this sort of problem, deep wells have one or more well completions, including well casing and downhole pressure valves. Schlumberger has a very nice website, the Oilfield Glossary, which explains terms like well completion with links, diagrams, and up-to-date state-of-the-art drilling industry expertise. As you can see, no techology exists which can effectively drill all the way down to the mantle of the Earth; very deep offshore wells are now pushing close to the 10-km neighborhood below sea-level, but this is not anywhere near reaching the mantle. To prevent a "volcano", we would need to invent the technology to both drill and complete a well at much greater depths; this would require materials that could withstand much greater temperatures and pressures than we currently have. Nimur (talk) 19:35, 10 April 2010 (UTC)

We can't even get through the Earth's Crust, let alone get into the Mantle. The continental crust is approximately 20-30km thick and our deepest mines are at most 5km down (I think). That means it's going to be very, very difficult to get to the Mantle any time soon. Regards, --—Cyclonenim | Chat  17:35, 10 April 2010 (UTC)

... so is the article to which I linked (Mantle_(geology)) total fiction? Dbfirs 18:52, 10 April 2010 (UTC)

No. We know quite a lot about the mantle, just not from direct observation. Measuring how Earthquakes travel around the world is the main way of finding out about the Earth's interior composition, I think. --Tango (talk) 18:57, 10 April 2010 (UTC)

Yes, I know that, but the article talks about drilling 23,000 feet to the mantle below the ocean floor. Was this done? Dbfirs 19:05, 10 April 2010 (UTC)

This book:
Ojovan M.I., Gibb F.G.F. "Exploring the Earth’s Crust and Mantle Using Self-Descending, Radiation-Heated, Probes and Acoustic Emission Monitoring". Chapter 7. In: Nuclear Waste Research: Siting, Technology and Treatment, ISBN 978-1-60456-184-5, Editor: Arnold P. Lattefer, [[Nova Science Publishers|Nova Science Publishers, Inc.
seems to suggest that the possibility is being seriously considered. Dbfirs 19:53, 10 April 2010 (UTC)

See: Kola Superdeep Borehole, they went down to 40,000 feet (on land) and it remains the deepest that mankind has ever drilled. SteveBaker (talk) 20:01, 10 April 2010 (UTC)

That project was abandoned because of the high temps at the bottom, and that only went about a third of the way through the crust. StuRat (talk) 20:56, 10 April 2010 (UTC)

23,000 feet = 7km or there about, not far above what I said. 40,000 is admittedly quite a bit more but still 8km or so from the mantle. So no, we can't store nuclear waste there. Regards, --—Cyclonenim | Chat  22:30, 10 April 2010 (UTC)

... yet! (... though I agree that we are not likely to try it until we know a lot more about the risks.)
What about the self-boring module that melts its way through the crust? Has this ever been built?
If our article on Chikyu Hakken is correct, and they are still on schedule, they should be nearing the mantle soon. Dbfirs 06:44, 11 April 2010 (UTC)

Well of course there is always a "yet" you can add on to any hypothetical situation. We can't travel to other galaxies... yet. Doesn't mean it's realistic to assume we have even the potential to do it yet. I imagine getting through the crust would be very, very expensive indeed and I'd speculate that it's probably cheaper to send it into space, where it won't come back or have any real consequences (as long as it clears the orbit intact). Regards, --—Cyclonenim | Chat  08:03, 11 April 2010 (UTC)

OK, fair comment. So our articles are over-optimistic about direct exploration, and all attempts have failed? Dbfirs 12:22, 11 April 2010 (UTC)

Have there even been attempts to get to the mantle? As far as I'm aware the only projects have been to see just how far we can get, and ultimately it's not that far. There was no failure, per se, just not as far as you thought :) Regards, --—Cyclonenim | Chat  14:25, 11 April 2010 (UTC)

Yes, I assume that this was an attempt: "The 57,500-ton Chikyu, which means the Earth in Japanese, is scheduled to embark in September 2007 on a voyage to collect the first samples of the Earth's mantle in human history." (from refernce 22 in our article on Mantle_(geology)). Since no-one seems to have heard of any success, I assume that the attempt was either a failure or was abandoned. Dbfirs 16:47, 11 April 2010 (UTC)

... and everyone seems to assume that the crust is of uniform thickness. The following is from ref. 21 in the same article: "Scientists have discovered a large area thousands of square kilometres in extent in the middle of the Atlantic where the Earth’s crust appears to be missing. Instead, the mantle - the deep interior of the Earth, normally covered by crust many kilometres thick - is exposed on the seafloor, 3000m below the surface." Dbfirs 16:54, 11 April 2010 (UTC)

Coming back to the OP's question, what would happen if we were to drill a hole near to a subduction zone, dump the waste there, and then seal the hole? I vaguely remember something like this being proposed somewhere. CS Miller (talk) 21:12, 11 April 2010 (UTC)

Subduction zones are associated with volcanoes. See, for example, Pacific Ring of Fire. Presumably, the odds of any particular package of nuclear waste reaching a volcano would be very small, but the consequence of that happening might be catastrophic if the waste was still dangerous. Might depend on how long that was likely to take, as to whether using subduction zones could makes sense. At the same time, subduction zones necessarily have earthquakes and grinding, etc. Such earth movements might rupture the containers while they were still near the ocean floor and allow things to leak back into the ocean. If you want things to stay put for millions of years, then it might be easier just to find a deep geological formation that is far from geological activity. Dragons flight (talk) 21:24, 11 April 2010 (UTC)

Not quite getting to the mantle (unless you're going through oceanic crust in some really thin spot), there was the plan of Deep_borehole_disposal. No mentions of the plan ever being implemented however. On a side note about continental crust Craton might be of interest. And an even bigger tangent, when you think about the continental crust being composed of granite, it makes sense that the continental crust is so thick. Granite is rich in quartz and potassium feldspars (like orthoclasse), the later products of the Bowens reaction series. What this means is that these minerals will crystallize last out of a body of cooling magma. In general, getting the conditions for this to occur are rare. It requires alot of minerals to settle out of the magma body. So from what I remember, alot of granite is thought to form from partial melting of the lower crust (magamatic underplating?). The last minerals to crystallize OUT of the magma are the FIRST to melt (also the FIRST minerals to crystallize are very unstable at normal earth surface because it's so different from what it came from, so they break down into clay minerals). So, when you have a cooled body of rock, and raise it to about 800C (adding water lowers this) (the temperature raise coming from a rising mantle plume or something?), the minerals needed for granite will melt out first, and this process lets you get granite. So, it makes sense that continental crust is so thick, because it's made from this process of partial melting and cooling again. Oceanic crust, on the otherhand, is made from mafic rock, basalt, which is made of amphiboles and pyroxenes, which crystallize earlier in the Bowens reaction series. It's not hard for cooling to progress enough to get these minerals. It also then makes sense why the Yellowstone Volcano has rhyoltic (rhyolite is the extrusive counterpart to granite) -- the lava there comes from this same process. Any corrections? Sorry for the tangent! 66.133.196.152 (talk) 09:19, 12 April 2010 (UTC)

Nuclear waste - reuse

Why can't we just centrifuge it again to re-enrich it to the point that it's ready for manufacturing of new fuel rods? According to [6], naturally occurring uranium is 0.72% U-235. What about the waste? Much less? --84.13.85.158 (talk) 16:32, 10 April 2010 (UTC)

You can reprocess the spent fuel rods, nuclear reprocessing goes into the details although the article seems to have problems. However you still end up with a lot of nuclear waste which includes a lot of stuff besides the spent fuel rods. Interesting enough this [7] & [8] suggest reprocessing actually results in more waste although I don't know how much you can trust the Institute for Energy and Environmental Research who are apparently anti-nuclear. However you could probably research it yourself from the citations they use Nil Einne (talk) 17:00, 10 April 2010 (UTC)

I haven't read the linked articles, but there are two factors to consider when measuring how much waste is produced by reprocessing. 1) You need to compare the waste produced by reprocessing with the waste that would be produced by using new fuel instead, you can't just look at the absolute amount produced. 2) There is a big difference between low level waste and high level waste - you can't just look at the total amount of waste produced, you need to look at how radioactive it is. --Tango (talk) 19:02, 10 April 2010 (UTC)

Actually the problem with an increased level of high level waste seems to be a key concern. E.g.:

Reprocessing is also the option that generates the largest amount of radioactive waste. The most dangerous of this waste is called high-level waste -- a liquid waste stream carrying chemicals used in reprocessing along with many radioactive isotopes from the spent fuel or other material. This high-level waste would be added to over 30 million gallons of liquid waste from past reprocessing already stored in underground tanks at SRS. (first ref)

When high-level waste and Greater than Class C waste are considered together, the volume of waste to be disposed of in a repository is greater by about six times compared to the no-reprocessing approach that is current U.S. policy on a life-cycle basis. Low-level waste and waste shipments are also increased several fold by reprocessing. These are Department of Energy estimates comparing present U.S. once-through policy with the French “recycling” system using thermal reactors (second ref)

Nil Einne (talk) 00:33, 11 April 2010 (UTC)

300 million gallons sounds dramatic - but it's a volume of only 100 x 100 x 100 meters. That's quite manageable. The problem with unreprocessed fuel rods is that they have long half-life materials. Reprocessing extracts those and leaves materials with a more manageable half-life behind. SteveBaker (talk) 02:02, 11 April 2010 (UTC)

What do you mean more managable? If we're still talking say 10k years, does that really make things much easier? Storing the unreprocessed fuel rods for millions of years may seem daunting but if you have much less of it it may be better particularly since you may be able to more effectively deal with it in the future (leaving such things for the future may seem a cop out however particularly if you keep the stuff in a way that you can safely recover it, it may still be better then leaving significantly more slightly lower level waste which won't last quite as long but still a very long time). In other words while I haven't researched this, I'm not seeing much in this discussion to convince me that the IEER is wrong, whatever their bias. P.S. Perhaps this wasn't clear enough from my earlier comments but the IEER also discussed significantly more lower level waste from reprocessing. Nil Einne (talk) 23:16, 13 April 2010 (UTC)

There was an NPR radio piece about this just a few days ago. You can indeed reprocess spent fuel rods - extract usable (high-radiation) stuff to use as fuel - and wind up with less bulky, less radioactive waste. That seems like a win/win situation - and indeed this is what is done in the UK, France and a few other countries. However, in the USA, the cost of reprocessing is still higher than storing the waste (for a million years!) and mining new uranium - so it's not done here. Elsewhere in the world, there is concern that reprocessing uranium-fuel-waste produces plutonium waste - which useful for making nuclear weapons. Hence there has been pressure on certain countries to send spend fuel rods to places like Europe for reprocessing instead of having them do it in-house and (like India) winding up with weapons' grade plutonium.

An interesting fact from the NPR piece is that if you took all of the used fuel rods ever produced throughout the USA over all of history - you could keep them in one 30' deep pool of water the area of a single football field. The actual AMOUNT of this high-grade waste is not by any means a problem. The problem is that we're stuck with looking after it for the next million years...also, we can usefully reprocess this stuff at any time in the future...like when the uranium runs out. The problem for storage is not that high-grade waste - but the medium and low-grade waste. Stupid things like used tools, gloves and coveralls from nuclear workers that are sufficiently radioactive that the law demand that they can't just be buried - but large in volume. The medium-grade radioactive waste is made up of things like the casings of the spent fuel rods could be recycled to make new fuel rod casings - but again, it's cheaper to store the old ones and make new ones.

The other interesting fact is that the oldest nuclear submarine in the US fleet has been more or less continuously sailing around the worlds' oceans for 30 years - and is still using the original "fist-sized" chunk of plutonium to do that. This brings home how amazingly powerful nuclear power really is!

Sooner or later (hopefully sooner), the world is going to have to come to grips with recycling and storing this stuff - because for sure we can't keep burning coal, oil and gas.

SteveBaker (talk) 19:28, 10 April 2010 (UTC)

In the US, it was initially the case that they thought that reprocessing would be a good way to deal with the waste issue and the power issue. But the two things that killed it in the late 1970s was that: 1. The political atmosphere was such that the US gov't didn't want to pay for reprocessing itself, and wanted the private sphere to do it. The problem is that reprocessing is not financially very lucrative (or at least wouldn't be until the price of uranium rose considerably). 2. There are proliferation/theft fears associated with reprocessing, because it increases the volume of plutonium used in reactors quite considerably. These two things led, in about 1980, for the Carter administration to ban reprocessing indefinitely, and nobody has ever succeeded in getting it back on the table. My personal opinion is that the US approach to nuclear policy is more about its historical politics than it is about technical feasibility. We have a political system that makes it very easy for fairly unfounded (or weakly-founded) fears to have a lot of influence on the political system when it comes to scientific and technical matters. This is not the case in the UK or France. Sometimes it is for better, sometime it is for worse. In the case of nuclear power, we have erred on the side of being extremely conservative since the late 1970s. --Mr.98 (talk) 02:05, 12 April 2010 (UTC)

It seems to me the UK and French approach is not so clear cut either. While I'm not a libertarian and while the US ban may be hindering private efforts, if the private efforts aren't worthwhile, then are the public efforts worthwhile? Just because it's possible doesn't mean it make sense and just because the UK and French (& Japanese) decided to do it doesn't mean they made the best decision. Given the above, it seems to me this is far from clear cut. I'm far from convinced the UK or France approach has any less to do with politics and history then the US. (Why would it? Most of the decisions do.) Sure not reprocessing may seem wasteful however if your primary concern is nuclear waste then that's what you should look at. Nil Einne (talk) 23:16, 13 April 2010 (UTC)

Nuclear has never needed to compete in a free market. Governments sunk immense costs into developing it in the first place, government is covering insurance, and government is subsidizing nuclear waste disposal (without any clear idea of how to so that). As for libertarian solutions: I always wondered how they handle this case. I build myself a nuclear plant, I sell electricity until it becomes unprofitable, spending all the money of fast women and pretty cars, then I die. Who picks up the bill of cleaning up the defunct nuclear site? --Stephan Schulz (talk) 09:45, 14 April 2010 (UTC)

Wheat Berries

Why are the wheat berries that ground up make flour referred to as berries, are they actual berries? And what other plants berries can be ground up to make flour? —Preceding unsigned comment added by 71.147.7.50 (talk) 17:47, 10 April 2010 (UTC)

No they are not true "botanical berries". See the article titled Berry for more details. The word berry gets applied to many different kinds of fruit. But True Berries are a specific class of plants that includes cranberries, grapes, and (surprisingly) many melons. Other plants with the name "berry" in them are not botanical berries, including strawberries, blueberries, and the various brambleberries (blackberry, raspberry, etc.) Wheat berries fit into this second class of false berries. --Jayron32 18:41, 10 April 2010 (UTC)

I thought that the normal term was "grains of wheat". Who calls them berries? Dbfirs 18:44, 10 April 2010 (UTC)

Nobody I know. In English, they are definitely called "grains". They may be called something that translates to "berries" in other languages, I suppose. --Tango (talk) 19:03, 10 April 2010 (UTC)

... and the answer to the second question (using "berries" in the "sense" of "part of a plant") can be found in our article on flour. Examples are rice, beans, nuts, some roots ... (lots more). Dbfirs 19:29, 10 April 2010 (UTC)

cf. Sugawara v. Pepsico, wherein Sugawara sued the makers of Captain Crunch cereal with "Crunch Berries", alleging that a "reasonable consumer" such as herself would be "deceived" by the description of the product's "berries" leading her to believe they're actual fruit, rather than clusters made chiefly of corn flour, sugar, oat flour, and more sugar. Sugawara lost, but someone else has filed a similar suit, this time about the fruitiness or otherwise of Fruit Loops. -- Finlay McWalter • Talk 19:30, 10 April 2010 (UTC)

That's Froot Loops. The spelling is no doubt to protect them from such lawsuits. Still, it's pretty clear there's an attempt at deception, at some level, as calling them "Froot", making them bright, fruity colors, and giving them a sweet, fruity taste and smell is obviously supposed to remind you of fruit. But, if it only fools you at a subliminal level, I doubt if you can sue for that. StuRat (talk) 20:45, 10 April 2010 (UTC)

I've encountered "wheat berries" only when they were soaked and included in a dish whole. --ColinFine (talk) 22:59, 10 April 2010 (UTC)

Here's the actual decision in Sugawara, BTW. Circéus (talk) 13:43, 12 April 2010 (UTC)

Bus brand

Bus wreck

I hope I am here at the right category. I already asked this question at the German Wikipedia, but nobody was able to help me. Last summer I took a photo of an old bus wreck at Arkhangelsk, Russia. I would like to know the automobile brand (maybe even type) of this bus. Unfortunately I can't ask this question at the Russian wikipedia, as they don't allow questions which aren't directly connected to Wikipedia. --Paramecium (talk) 19:10, 10 April 2010 (UTC)

A kinda-similar-looking LiAZ bus

It looks a bit like these LiAZ busses - but differs in details. We have an article about LiAZ (Russia). SteveBaker (talk) 19:32, 10 April 2010 (UTC)

Yes, I already browsed the articles about the LiAZ models. Especially the headlamps of this bus are very distinctive, but until now I didn't find a LiAZ model which looks similar. --Paramecium (talk) 20:04, 10 April 2010 (UTC)

I agree, the headlamps don't match, the window patterns are different, the engine compartment has a bigger cover and the wrecked bus doesn't have a "destination" sign on the front. However, I found a lot of pictures on Google Images of LiAZ busses - there are dozens of slightly different designs and they all have that overhanging roof and the same general 'look'. None of them match your photo exactly - but lots of them have the same design cues. It's perfectly possibly that it's not a LiAZ - but I don't see other kinds of russian bus that look anything like that - so I'd put the odds at better than 50/50. Sorry I don't have a more definite answer. SteveBaker (talk) 01:17, 11 April 2010 (UTC)

I have to ask, did they just pull that bus off the road and leave it there ? That pic doesn't appear to be a junkyard, although I do see a car behind the bus, too. StuRat (talk) 20:38, 10 April 2010 (UTC)

No, it's no junkyard. It's a small street in a quarter in the north of Arkhangelsk with many wooden houses and quite poor people. Actually it's not seldom that you can encounter such car wrecks in russian towns. --Paramecium (talk) 21:25, 10 April 2010 (UTC)

In the United States, we usually put such vehicles on cinder blocks. Nimur (talk) 22:18, 10 April 2010 (UTC)

Question about Autism

السلام عليكم لديا بعض الاستفسارات هل يحدث مرض التوحد بسبب التسمم بالمعادن الثقيلة هل لدى كثير من المصابين بمرض التوحد موهبة في الرسم والفن والكمبيوتر؟ هل يفضل دمج الأطفال المصابين بمرض التوحد مع الأطفال الطبيعين في المدارس؟ هل يوجد علاج ولو مؤقت لمرض التوحد بغض النضر علي العلاج النفسي؟ هل مريض التوحد يشعر بالنجومية في الفضاء المفتوح مع عدم التركيز علي أي شيء محدد؟ —Preceding unsigned comment added by 41.252.190.63 (talk) 22:44, 10 April 2010 (UTC)

I gave the above text to Google-translate and added a section heading:

"Peace be upon you for some friendly inquiries you happen autism because of poisoning by heavy metals is among many people with autism talent in drawing and art and computer? Is it better to integrate children with autism for natural with children in schools? Is there even a temporary cure for autism, regardless Nadar Ali psychotherapy? Do you feel sick Autism stardom in the open space with no focus on anything specific?"

To our questioner: This is the English-languge Wikipedia help desk - we expect questions in English and we can generally only reply in English. SteveBaker (talk) 01:07, 11 April 2010 (UTC)

There idea that autism is caused by heavy-metal poisoning in the womb is highly controversial - as is the idea that heavy-metals in preservatives used in vaccines are the cause. Autism is a "spectrum" condition...not all autistic people have special talents - those at the most extreme end of the range are completely cut-off from the normal world and certainly could not function in a normal school. Those at the other end may appear more or less normal and certainly should be integrated into schooling (although they might benefit from a few special classes). There isn't a cure for autism - but some of the worst symptoms (things like depression) can be treated with drugs. SteveBaker (talk) 01:34, 11 April 2010 (UTC)

The idea that autism is caused by heavy-metal poisoning in the womb is not "highly controversial"-- it is simply false. There has never been any evidence of such a relationship and the evidence against it is as strong as the evidence that evil spirits don't cause cause tuberculosis. You usually provide better answers than this, Steve. alteripse (talk) 15:01, 11 April 2010 (UTC)

Time to nitpick:

You said "the evidence against it is as strong as the evidence that evil spirits don't cause cause tuberculosis". There hasn't been any such proof on TB, has there ? Even though the cause of TB may be absolutely established, there's no way to prove that that cause, in turn, isn't caused by "evil spirits". So, that argument is rather silly.

You also said there "has never been any evidence of such a relationship". If true, that still doesn't constitute proof that the relationship doesn't exist, especially if the lack of evidence is due to a lack of studies. Also, since autism actually may be a range of disorders with similar symptoms, it's possible a small portion of them may be "heavy-metal allergies", while the majority are not. This would make any study problematic, if the percent with this sensitivity are low enough to get lost in the margin of error for the study as a whole.

I'm not saying I support the relationship, just that it's a bit early to conclude that "it is simply false". StuRat (talk) 15:53, 11 April 2010 (UTC)

I'd also point out that it's perfectly possible for some issue to simultaneously be both "false" and "highly controversial". SteveBaker (talk) 19:55, 11 April 2010 (UTC)

I'd like to see your source for it being simply false, do you have such proof? Whilst I don't actually agree with the OPs reasoning, heavy metal poisoning as a source of mental illness, mental retardation or whatever is not completely wild. The controversial bit comes from saying that it derives from the vaccines--there is no proof of that. Regards, --—Cyclonenim | Chat  10:52, 12 April 2010 (UTC)

Stu I chose that comparison intentionally. It is hard to prove a negative and it took decades of research and controversy before a mycobacterium was accepted as the cause of TB. However, at some point, the medical scientists accepted the evidence and it was no longer accurate to say it was controversial, even though there are quacks who have continued to deny the germ theory of causation for over a century. Perhaps an even better comparison would have been evil spirits causing epilepsy, which was a documented ancient belief (Mark, Gadarene swine) that has not been "scientifically disproved" by any study you can cite, and epilepsy remains a somewhat mysterious (in terms of causation) brain disorder. There has been ample research on the possible link between mercury and autism and none of the honest, well-designed studies show an association, let alone causation. Steve, if the questioner had asked about evil spirits causing tuberculosis, would you have explained the germ theory as controversial just because you can still find some fools who deny it? We generally do a good job of distinguishing crap and misinformation from facts here. In my opinion, your answer failed to do so in a clear-cut case. alteripse (talk) 10:58, 12 April 2010 (UTC)

Actually, there is fairly good evidence that mercury exposure in the womb can affect a growing baby's brain. That's why you're not supposed to eat shellfish during pregnancy as there is a chance of exposure to methylmercury. Therefore it's not a wild assumption to guess it could cause autism, as obviously that is an illness affecting the brain in some way. But you are right about the lack of reliable trials and case studies to actually prove the claim, so who knows. Regards, --—Cyclonenim | Chat  16:23, 12 April 2010 (UTC)

If you are reffering to vaccines then I disagree. There have been lots of studies. Thiomersal was completely removed from childhood vaccines about 7 years ago but the rate of autism has not dropped at all. So i think that's pretty good proof that this mercury compound is not causally related to autism in the doses which were present in those vaccines. Vespine (talk) 05:38, 14 April 2010 (UTC)

As I said above, I'm not referring to the vaccines, that's very controversial. I'm saying mercury expose in general has consequences for the nervous system and brain in general, so it wasn't a preposterous assumption that thiomersal could cause autism. Clearly, studies have proven that not to be the case. I agree that the removal of thiomersal from vaccines, and the consisitent rates of autism, proves there is no causual link between the two, but that's not to say mercury and it's compounds in general are harmful to the brain. Regards, --—Cyclonenim | Chat  13:23, 14 April 2010 (UTC)

Uncertainty principle

In "a brief history of time", stephen hawking emphasises that the reason we cannot precisely know both a particle's position and its momentum is not simply because we disturb the particle when we try to measure one or the other but that they actually do not have a definite position and momentum at the same time. I believed this to be the correct interpretation because, well, stephen hawking said it.

However, Ive recently been looking into the subject more and even the uncertainty principle seems to suggest that, at least, it is not fully agreed upon which interpretation is correct. In the first paragraph in particular I believe is where this ambiguity lies. From then on it seems to agree with the interpretation explained by hawking. Can someone confirm that this is the "correct interpretion" (i.e. the view held by most scientists)? --212.120.246.119 (talk) 23:40, 10 April 2010 (UTC)

I can only tell you my own interpretation, which is that the uncertainty principle causes the manifestation of an observation disturbing that which is observed. StuRat (talk) 03:36, 11 April 2010 (UTC)

It's not just observation. Mathematically, once you know the exact position, you know nothing about the momentum; once you know the exact momentum, you know nothing about the position. The key words are "exact" and "nothing." You can know a little about one and a lot about the other, but once you know one exactly, you know absolutely nothing (not exactly, not approximately, not at all) about the other. 63.17.91.51 (talk) 03:58, 11 April 2010 (UTC)

There's not really an agreed upon "correct interpretation" of quantum mechanics. See Interpretation of quantum mechanics. We can agree about the physical implications of the theory since they can be tested, but how we should understand these results is more of a philosophical question and there is no shortage of theories that have been proposed. One thing to note about hidden variable theories (where particles have an actual position and momentum even though we can't ever know them both at once with certainty) is that they have to sacrifice the principle of locality. Some people don't like that, so in that sense you could say that hidden variable theories are unsatisfying. Rckrone (talk) 04:49, 11 April 2010 (UTC)

Ignore the above answer, your question has nothing to do with interpretations of quantum mechanics (though you may find them interesting one you understand the uncertainty principle). The position of a particle is described by a probability distribution (the wavefunction) and the momentum (or possible momenta) is not an independent property but can actually be calculated from the way the wavefunction changes from place to place. A particle with a definite position has a different position probability distribution than a particle with an uncertain position, so it therefore also has a different momentum distribution. The uncertainty principle puts limits on how definite either probability distribution can be, for example, a particle with a definite position will have a momentum distribution of every possible momentum, with equal probability. 74.14.111.110 (talk) 06:22, 11 April 2010 (UTC)

OP: If for some reason you're looking at these posts in reverse order, please don't ignore my response. :(

You might find it useful (although there is always the possibly that you won't). Instead, ignore 74...'s advice to ignore my response. Rckrone (talk) 06:51, 11 April 2010 (UTC)

You may also wish to consider that, in the 22 years since the book was published, the science has moved on apace and ABHOT may be out of date. --TammyMoet (talk) 10:39, 11 April 2010 (UTC)

Hawking's book is not outdated and 74.14.111.110's answer above is correct. It's important to understand the difference between the uncertainty principle and the observer's effect which may also exist even in classical mechanics. That's what StuRat is talking about Dauto (talk) 01:57, 12 April 2010 (UTC)

(ec) Hawking's basic point, that the UP is not really about the measurement problem but about a fundamental property of the universe, is, I think, agreed upon by all people who understand the uncertain principle. The one-particle-affects-the-other problem is how Heisenberg initially thought of it, but even he quickly agreed with Bohr that this was not the best way to think about it. Bohr's way of thinking about it (which is the wavefunction issue that 74.14 mentions—paragraph 2 in the UP article) is a little harder to explain, but the basic take-away point is that UP is something fairly inherent to the universe under any interpretation, and not just a measurement problems. It's not so much that the problem stems from the fact that the measurement disturbs the system, in this view, but that the system itself is contrary to precise measurement. --Mr.98 (talk) 01:58, 12 April 2010 (UTC)