Wikipedia:Reference desk/Archives/Science/2012 May 29

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May 29

Central Sleep Apnea theory contested

The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

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Gentlemen

Some weeks ago for a second time I included in Wikipedia article on Sleep Apnea a short text titled "Central Sleep Apnea Contested". Both times this text was erased from Wikipedia the very first day in which it was posted.

On the other hand, HuffingtonPost published a post I sent on this same issue and they unposted it after about 15 minutes. But they sent my article to what they call their “Medical Preview” and after 15 days they got the medical approval of my revolutionary theory on this subject and they posted my Article: http://voces.huffingtonpost.com/../../antonio-garcia/para-superar-la-apnea-del_b_1501414.html.

Extensive text removed by Franamax. This is self-promotional / soapboxing unsuitable for the Reference Desk (no atucal question was asked) and should not appear in search engines. The removed text is available in page history. Franamax (talk) 02:55, 29 May 2012 (UTC)

— Preceding unsigned comment added by Genserico (talk • contribs) 00:04, 29 May 2012 (UTC)

The correct place to bring this up would be the sleep apnea talk page. However, removing your changes to the sleep apnea article was the correct thing to do. The main problem with your edits is that the book that you wrote does not count as a reliable source, in part because you are just a writer and a historian, not a doctor. I think it also counts as original research, since you yourself wrote the book that you're trying to promote in Wikipedia. And since you're self-promoting your own work, it also makes it hard for your edits to present a neutral point of view. Red Act (talk) 01:58, 29 May 2012 (UTC)

Note also that your mention of "legal consequences for Wikipedia" possibly violates Wikipedia's policy on legal threats. I recommend in the strongest possible terms that you delete that part of your statement. Short Brigade Harvester Boris (talk) 02:40, 29 May 2012 (UTC)

I've removed the bulk of the original post as it seems more intended to get onto a search engine than seek anything the RefDesks actually provide. The removed text can bee seen here. Franamax (talk) 02:57, 29 May 2012 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Low frequency sound waves

Apparently low frequency sound waves can travel very far, but direction of the source of such a sound wave can be hard to determine. What's the physics behind this (I'd prefer a technical answer). Thanks! 65.92.6.118 (talk) 01:18, 29 May 2012 (UTC)

I think that high frequency sound-waves are informationally more dense than low frequency sound-waves, so they are more easily scrambled by the environment as the propagate. It's like writting with a fountain pen - if you write in a large font size, and acidentaly smudge it as you do, then it is easier to make out what it is supposd to say, compared with a small font size. Sound-waves decay as the propagate, high frequency sound-waves are just easier to merge with background noise. It also depends on the evironment, differet materials are prone to absorb different frequancies of sound-waves than others. Plasmic Physics (talk) 03:32, 29 May 2012 (UTC)

The further from the source sound wave has travelled the larger the uncertainty becomes. The same reason why the arc length increases with the radius. It's just basic maths. Plasmic Physics (talk) 03:35, 29 May 2012 (UTC)

It has more to do with the ratio of the wavelength to the dimensions of the sensor (typically, the human head). If by "low frequency" you mean something around 20 Hz, then the wavelength is about (300 m s^-1) / (20 s^-1) = 15 m. The diameter of the human head is about 2 orders of magnitude smaller so there isn't much phase difference between the ears at such low frequencies. Wikipedia's article on Sound localization is reasonably good. Short Brigade Harvester Boris (talk) 03:46, 29 May 2012 (UTC)

I don't think that is where he was going. Plasmic Physics (talk) 03:57, 29 May 2012 (UTC)

The OP has asked 2 things: a) what is the physics behind the fact that low frequency sounds travel farther than high frequencies, and b) why is it harder to tell the direction of lower frequency sounds.

With regard to the first question (a): PlasmicPhysics has it wrong, as he has confused ear sensitivity with attentuation of sound over distance. The attenuation of sound in air has two parts: 1) a drop in intensity to the third power of the distance, due to radiation in all directions (360 deg), so that a unit area covers a smaller angle as you move away; 2) attenuation above the third power due to the viscosity of air. This part increases approximately in proportion to the square of the frequency (if air comprised only of monatomic gas, it would be exactly proportional to frequency squared.) Viscosity is a form of frictional energy loss and is increased if you try to move the air faster. A method of calculating the attenuation in air is given in International Standard ISO 9613-1 (1993).

With regard to the second question (b): The brain appears to calculate the direction of a low frequncy sound from the phase angle beween the two ears. The phase angle is proportional to the ratio of wavelength to the distance between the ears. As frequency is reduced, the wavelength becomes so huge compared to the inter-ear distance that the phase angle becomes too small to sense. Form this, you would expect that direction accuity would be according to:

k d * (2 π f)

where k = a constant representing the efficiency of the brain calculation of phase, d = distance bewteen the ears (~180 mm), and f = frequency (Hz).

However, it is not that simple. Our perception of direction is often better than expected, still works to some degree for people deaf in one ear, and is far from fully understood. It may be that the brain has a way of utilising short-term phase memory (if the distance between the ears is insufficient, subconsciously move the head & compare) and wavefront bending around nearby objects, and/or some other trick(s). It has been shown by a number of researchers that if the head is prevented from moving (eg with clamps), a lot of our directional sensitivity is lost. An article and subsequent letters in the electronics journal Electronics World some years ago concerning artificial recreation of direction in headphones made this sort of trickery clearer. From memory the author was Ian Hickman, who tried using head position sensors connected to special electronics to alter the phase difference as the subject's head moved.

Ratbone58.170.163.145 (talk) 04:16, 29 May 2012 (UTC)

Neither the OP, not I have mentioned anything about ear sensitivity. Plasmic Physics (talk) 04:48, 29 May 2012 (UTC)

Well, you talked about noise. Thermal noise is what sets a limit on ear sensitivity (unless your ears are damaged.) Dispersed background noise, or noise above the thermal level, can set a practical limit on ear sensitivity. Noise has absolutely nothing to do with attenuation. Sound intensity will drop the same amount over a given distance whether acompanied by noise or not. Ratbone58.170.163.145 (talk) 05:02, 29 May 2012 (UTC)

I wasn't talking about ears. I was talking about how sound interferes with each other and scatters, and what role frequency plays in magnifying or diminishing the effects of scattering. Plasmic Physics (talk) 06:03, 29 May 2012 (UTC)

I can accept it, if I'm wrong, but I did not talk about ears. Plasmic Physics (talk) 06:06, 29 May 2012 (UTC)

For ears, I think the problem with determining direction is that there is very little difference in phase between the two because the frequency is so low. You would need two sites much further apart to tell the direction. I would be very curious to find more information about mechanically detecting low frequency sound, and especially about materials capable of blocking it (which might also be important for generating good directional sensors). The only thing I've noticed that sounds like it blocks low frequencies is a water-filled container (including parts of the body), but I've not found this discussed scientifically. Wnt (talk) 12:48, 29 May 2012 (UTC)

Thank you for the great answer. ```` — Preceding unsigned comment added by 65.92.6.118 (talk) 02:47, 30 May 2012 (UTC)

Refraction and entantiomers

Is it unreasonable for entantiomers to have differing refractive indices? Plasmic Physics (talk) 06:09, 29 May 2012 (UTC)

I think the answer depends on how you define what's different. Each entantiomer of a set has diferent refractive indices for each polarisation plane. For compound having two mirror forms, the second form will have the two values swapped over. Ratbone58.170.163.145 (talk) 07:06, 29 May 2012 (UTC)

Is there not some sort of standard, why do I regularly see only one RI listed for a substance? Does this mean that only one polarisation is shown? Plasmic Physics (talk) 07:59, 29 May 2012 (UTC)

As Ratbone pointed out, chiral materials have a different refractive index for right- and left-circularly polarized light. However, the average refractive index for both enantiomers is the same. Furthermore, the splitting of polarized light due to chirality is very small, typically a few parts per million (see [1]). This means that for practical purposes, there is no difference, especially when the refractive index is reported with only three or four significant digits. - Lindert (talk) 08:36, 29 May 2012 (UTC)

So, the standard is to show the RI for unpolarised light? Plasmic Physics (talk) 09:41, 29 May 2012 (UTC)

Assuming yes, what is the relationship between the RI for a mixture that has many diastereomers and the RI of each entatiomeric pair? Plasmic Physics (talk) 05:55, 31 May 2012 (UTC)

What evidence is there that DNA has a double helical structure in vivo?

After much furor at the talk page of Non-helical models of nucleic acid structure, I have been wondering what evidence is there that DNA takes on a double helical structure in vivo and not just in crystallographic determination, for example? This is in consideration of the fact that the cellular environment (especially of a nucleus) may be quite different to even the most thoughtfully prepared in vitro preparations of DNA that would allow structure determination of some kind (see macromolecular crowding). It is something I had never really thought about before until I read this article, which is not at all in a wiki style or holds a neutral viewpoint may I add, but now that I consider it I think it is a question worth asking. Any ideas? -Zynwyx (talk) 08:40, 29 May 2012 (UTC)

As mentioned on that same talk page, we do also have liquid-phase models of DNA structure produced using NMR. But then again, in those experiments the DNA is usually in relatively small fragments, and the rest of the solution is merely a salt buffer, rather than being filled with all the proteins, nucleotides, and other molecules you'll find in a nucleus. But for me, the best evidence for the double-helical structure is the corroboration of two types of studies. One would be ChIP-seq (working from fixed samples, it may as well be in vivo data) studies as well as older technologies such as DNA footprinting (entirely in vitro). The other would be NMR studies of DNA-binding proteins (or fragments thereof) and their accompanying DNA binding site (also in vitro). In many cases, you can actually show that the protein beautifully binds to a double-helix, right at the position predicted by both in vivo and in vitro methods.

Now, to play devil's advocate, it's also true that the selection of proteins for which there is an in vitro demonstration of binding to a double helix exactly as it should is precisely that: a selection. When a scientist fails to produce a comprehensible NMR spectrum, he won't publish it.

So yes, in a very strict sense, no one has ever shown direct evidence that the in vivo structure is a double helix, but I think the indirect evidence is basically overwhelming. I mean, shit, I can take a cell that is quite alive, fix it to preserve molecular structures, extract the chromatin, show that a particular protein is bound to a particular portion of the DNA in that chromatin, and then recreate the protein and the DNA sequence in vitro and show that they bind perfectly while the DNA is a double helix! I don't know how many proteins that has been demonstrated for, but it's more than a few. Someguy1221 (talk) 09:55, 29 May 2012 (UTC)

what about UV spectroscopy? don't the double helix and denatured forms supposed to give different absorption behaviors? Maybe one could look at the (almost) in-vivo spectrum and calculate the ratio of various different structures.Staticd (talk) 17:47, 29 May 2012 (UTC)

Thanks for the responses. I guess the fact that many DNA-binding proteins have a fit for the double-helix structure is a good indication that DNA is double helical in vivo. -Zynwyx (talk) 10:39, 30 May 2012 (UTC)

In vivo hydroxyl radical footprinting is being done [2], apparently without surprising results though I didn't chase down the Tullius group papers. The procedure randomly splits the DNA backbone, which shows which side of the strand is up against a protein and which is not. Since the strand is a double helix, that means that the pattern of breaks of each strand are regularly spaced. [3] Wnt (talk) 10:55, 31 May 2012 (UTC)

non-determinism and causality

Are non-determinism and causality mutually exclusive? I mean if we say determinism means that "the evolution and the present state of a system is the result of its initial state only." then non-determinism means that the present state of the system is not the result of its initial sate (at least not completely) Now if we agree that our system is non-deterministic, then we may ask "if the present state of the system is not only the result of its initial state, then what is the "other thing" that it is partially or completely the result of?" and because our answer can not involve an inside-the-system process (because we'll be back to determinism) it is either

1.An outside of the system process (which I think will either lead us back to determinism or an infinite loop, because then the final state will be determined by the initial state AND the outside-of-the-system process, and if that process is deterministic, then the whole process is deterministic, and if it's not, again we can ask the same question we asked about our first non-deterministic system, and we're in an infinite loop)

2.Nothing. in this case, our final state is at least partially caused by nothing, in other words it does not have a cause, so the statement "everything has a cause" will be wrong... so... am I wrong? where am I wrong in this reasoning?Because I always linked determinism and causality in my mind, and I didn't know where does that come from, and now I think I found a way to express it, and I wanna check if it's true?--Irrational number (talk) 11:20, 29 May 2012 (UTC)

You and I exist because our respective parents conceived. Everything we do (or don't do) is "caused" by something. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:33, 29 May 2012 (UTC)

I don't know if this is relevant to the philosophical aspect here, but according to quantum physics there are things that are not caused by anything, but cause things to happen. Such as the radioactive decay of a particle. There is no timer, no cause, no determinism, no trigger, no hidden initial state that can be set or examined, no possible way to replay the experiment deterministically. It just happens when it happens to happen, and then can result in you digging a grave for a pet, or start a chain reaction that detonates a nuclear bomb. (Just rambling, but since you asked this on the science desk rather than at humanities...) 88.114.124.228 (talk) 16:49, 29 May 2012 (UTC)

What, as if the particle "decided" to do it? That's a pretty heavy implication. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:50, 29 May 2012 (UTC)

I think that this is mostly a matter of definition. Causation tends to refer to relationships between individual events (the cause of death was a blow to the head). You can have a nondeterministic world where at least some events have identifiable causes (we seem to live in such a world) and I suppose there could be a deterministic world with no identifiable causes (because the state of everything at time t is affected by the state of everything at time t−1 in a way that's mathematically precise but impossible to actually calculate).

Another problem is that you can turn any nondeterministic theory into a deterministic one by adding some extra state to the world, and any deterministic world is unpredictable in practice because it's impossible to know the exact state at a given moment or compute the state at a later moment before that moment has arrived. So it's hard for me to accept that determinism or nondeterminism can be incompatible with anything; they seem to be the same thing. -- BenRG (talk) 20:55, 29 May 2012 (UTC)

One perhaps convenient definition of determinism vs. non-determinism is that in a totally deterministic worldview, all information about the future can be derived from information about the present. The convenience here is that it readily translates into quantum terms (which is the only place that determinism gets really weird anyway) — there are certain quantum interpretations which allow you to claim the world is deterministic (Einstein would have been cool with this) and those that would claim it is ultimately non-deterministic (e.g. the Bohr, Bell, and so on interpretations of QM). In the latter case, there simply is no ultimate repository of information until the wavefunction has collapsed and so on, and in some cases there is no way to know how that is going to go down. The relationship between that an causality strikes me as a complicated one. An unstable nucleus will decay at an unknown time, but we know why it decays — it is unstable. What we don't know know is why the decay event happened exactly then — there may be no reason, other than the fact that it is unstable and that's part of the definition of being unstable. Is that an acausal worldview? Bohr and Pauli thought it was, but I agree that it's largely a matter of definition. --Mr.98 (talk) 22:26, 29 May 2012 (UTC)

The problem with that definition is that it excludes cases where the future is determined, but not in any way that can be decided from information about the present (pure fatalism, for example). --Trovatore (talk) 00:10, 30 May 2012 (UTC)

What is the nature of life

If our genes are 99% like chimpanzees, what if anything, does the other per cent most closely resemble? ~ R.T.G 13:27, 29 May 2012 (UTC)

Yeah, and what about the other 1% in the chimp?165.212.189.187 (talk) 13:37, 29 May 2012 (UTC)

(short version of what I say below - traits that humans have that primates don't could occur in other species due to Convergent evolution)

Humans naturally have a rather anthropocentric view of the tree of life, and as such we think we're very different from animals like chimps. However on a grand scale primates show a lot less variation than a lot of other types of life we often group together with a single term, consider how varied beetles are, or how so may different types of life are called "bacteria". Indeed, in one perspective there's not much difference between all animals, we're all just differently shaped blobs of similarly constructed eukaryotes. On the billions of years timescale of the evolution of life the time that has been spent differentiating humans from other primates is small, so we only have a little DNA which has been naturally selected for humans' specific ecological niche.

As to what that 1% would resemble, if other members of homo were still around, we'd have stuff in common with them (as they'd be related). As to what currently existing non-primate animals will have similar genes, you'd have to look for occasions where animals have independently evolved characteristics that humans have (but other primates don't). It's not unknown for a gene to independently evolve two or more times - see the article on Convergent evolution. -- LukeSurl ^{t c} 16:55, 29 May 2012 (UTC)

The answer is complicated. First it is necessary to point out that the 99% figure only applies to the portion of DNA that codes for proteins, which is only about 1% of the total human DNA. The remaining DNA differs quite a bit more between humans and chimps, but it is hard to give precise numbers because it is hard to figure out how to do the comparison. In any case, many of the differences are random mutations with no describable structure, but lots of them arise from transposons such as Alu elements. In terms of the total genome, the thing that actually most strongly distinguishes humans is our Alus. Looie496 (talk) 17:17, 29 May 2012 (UTC)

"Take a chimpanzee. Stretch the body out, rework the musculature and bones a bit. Elongate the nose and numerous other fairly superficial changes (remove most of the hair). Radically increase the frontal lobe and rewire it considerably." --Mr.98 (talk) 12:35, 31 May 2012 (UTC)

Uh? I am very confused by the idea about this bit of DNA being only 1% Hope you still see the response! ~ R.T.G 19:51, 1 June 2012 (UTC)

How does the pressure-temperature diagram for refrigeration look like?

Most refrigeration cycles are described with the temperature vs entropy (T-E) diagram (fig 1).

Figure 1: Temperature–Entropy diagram.

However I would like to know how the diagram for pressure vs temperature looks like (fig 2).

I assume that in a fridge the tubes inside the food storage will contain gas which increase in temperature from the heat that leaks inside. The latter compression of the gas should cause an increase in temperature (and pressure) according to the ideal gas law (pV=nRT). The compressed gas would then inside the radiator tubing equalize with the surrounding ambient room temperature and thus decrease in temperature in order to loose energy to the environment. At the end of the radiator when the gas/liquid is expanded the temperature decreases (and pressure) and the cycle repeats.

Does the diagram below describe this correctly, and if not how should it look like?, except that after compression the media is likely in gas form in the beginning and not liquid as drawn.

Figure 2: Pressure-Temperature diagram. v2

Electron9 (talk) 16:45, 29 May 2012 (UTC)

Firstly, the refrigerant does not act as an ideal gas under the conditions that exist in refrigeration, secondly, your marked up graph shows compression moving from vapour to liquid. Compression must be entirely within a vapour region. Wickwack121.221.228.157 (talk) 02:24, 30 May 2012 (UTC)

Accurate now with compression completely in the gas phase and transitions between phases only when exchanging heat energy with the environment ? (how does the gas behave?) Electron9 (talk) 03:15, 30 May 2012 (UTC)

You have your marked up diagram nearly right now. Could you please repost your orignal mark-up, so that both are included? Otherwise the discussion will not make a lot of sense to anybody who finds this later on, either here or in the searchable archives. Expansion can cross the liquid/vapour line - show this by moving the cycle to the right. When refrigeration compression and expansion are plotted on a pressure-temperature diagram, the lines will be curved, not straight. However, I have never bothered to calculate the curvature, and like you, I have never seen it plotted on a P-T diagram in a textbook. When gasses are near the liquid-vapour region, they depart from the ideal gas laws. At low temperatures, pressure is lower than it would be for an ideal gas. Wickwack124.182.185.168 (talk) 03:46, 30 May 2012 (UTC)

Unfortunately the way commons work the old version can't be shown as an image with inline wikicode, but here is a link to version 0. I think the "can" makes it hard, as there will be multiple choice, expansion inside liquid or out to gas and that will contradict simplicity. Which way should the compression and expansion moves bend? Electron9 (talk) 04:41, 30 May 2012 (UTC)

Now version 2 shows the media expanding from liquid phase into gas phase (link to v1). I assume that's the most common case. But not necessarily the only possible one. Electron9 (talk) 04:55, 30 May 2012 (UTC)

Is it correct now?Electron9 (talk) 00:39, 31 May 2012 (UTC)

Physics/Math Theory ... Flat Flexible Object ... Volume Mass Force

Can a flat and flexible shape or object have Volume if a mass or force is applied to it? What I'm wondering is: if it doesn't have a top or lid on it, does it have Volume? I know that your thinking yes, it does!!!! But nobody's taught it to anyone, it's never been established. So, I want to know if it's been established or not. And, if not, would gravity affect if this theory is true or not. weight plus height plus mass equals Volume????--DAVINATOR8001 (talk) 19:28, 29 May 2012 (UTC)

What do you mean by flat ? If you mean a mathematical plane, with no thickness at all, then no, it wouldn't have any volume. But any real world object will have some thickness, even a piece of paper. So, yes, it does have a volume, and it can be calculated, given the thickness, length and width. StuRat (talk) 20:22, 29 May 2012 (UTC)

... and mass is connected with volume only through density (and weight is connected with mass only through gravity). Dbfirs

He's not talking about thickness or density. He's referring to this: Take a can. It has a volume. Cut off the top. The enclosed volume is still there, obviously, but it is not enclosed. Davinator is asking if that still counts as the volume of the can. With regards the flexible surface, if instead of starting with an enclosing object and cutting off one surface, he's asking about starting with a flat surface and denting it into something that could be a container but missing one surface. The answer to your question, Davin, is that a volume can only be defined for a closed region of space. Even if you cut the top off a can, you can still define the "volume of the can" as the region of space that would have been enclosed had the top still be there. Same as with bending a flat surface. But you always need to at least conceptually, if not physically, enclose a region of space. Someguy1221 (talk) 21:13, 30 May 2012 (UTC)

Yes, I suppose you could call that a "basin". This is a fairly important concept in geology, since, of course, lake basins don't have tops on them (unless you count an ice cap), but still have a volume they can hold before they overflow their banks. In general, however, the orientation of the object would control how much liquid it could hold. StuRat (talk) 22:47, 30 May 2012 (UTC)

If an aquarium holds 10 gallons of water, does half the aquarium hold 5 gallons of water? Each half, on its own, is not physically enclosed, except by an imaginary dividing plane, but that should suffice. Wnt (talk) 11:41, 31 May 2012 (UTC)

It would depend on how the aquarium is cut in half and how it is oriented. If you cut the top half off, then yes, if you cut it down the center, then no, but it could still hold some water if you tilted it properly. StuRat (talk) 05:03, 2 June 2012 (UTC)

This seems related to the concept of the convex hull. StuRat (talk) 05:03, 2 June 2012 (UTC)

Making Ammonium sulfate

I would like to make ammonium sulfate to make the soil in my garden more acidic- it is highly alkaline. I have ammonia cleaner -ammonium hydroxide- and some "soil sulfur," which I think is probably pure sulfur. Could they, or other household products, be combined to make the fertilizer? B^e——C_ritical 19:36, 29 May 2012 (UTC)

Urine is acidic. You could dilute it, say 10:1 with water, and spread it around the garden. It will take a long time to make a difference, but, on the plus side, it's free. StuRat (talk) 20:18, 29 May 2012 (UTC)

I'm dealing with extreme alkalinity. White alkali is collecting on the surface. Actually, I thought urine was alkaline... or salty. I'm no chemist. Anyway, I already use urine as much as I can... a lot. I just dumped gallons on the compost pile. I also use large amounts of coffee grounds. It's not enough. They make ammonium sulfate, but I thought maybe I could make my own. I would also like to know how much of the stuff like this it might take for this extreme condition? B^e——C_ritical 22:23, 29 May 2012 (UTC)

Have you had the soil tested? If so, please share the results so that we can better help. If not, why do you think you have highly alkaline soil? I highly suggest that you get a test if you haven't. They are very inexpensive, and sometimes free via an extension service. Other factors can cause white crusts to form on soil. 71.169.121.43 (talk) 22:38, 29 May 2012 (UTC)

Sulfur is not the same as sulfuric acid (which is what you'll need to make ammonium sulfate). Under standard conditions, sulfur reacts poorly with aqeous ammonia. At best you'll get small quantities of ammonium hydrosulfide. Vinegar is acidic, try that. Plasmic Physics (talk) 00:10, 30 May 2012 (UTC)

Reduce some vinegar by boiling untill it's very concentrated, let it cool, and add it to aqeous ammonia. This should make acetate of ammine, you can dry this at low temperatures to procure the powder, which you can then spread on your garden. Plasmic Physics (talk) 00:24, 30 May 2012 (UTC)

Cool interesting answer, thanks (: Sounds like it would work but wouldn't be practical for a whole garden... Just better to get the commercial stuff since the chemicals I have won't combine easily. But it would make a truly awesome school project for a kid huh? B^e——C_ritical 02:39, 30 May 2012 (UTC)

If want to prepare vitriolate of ammine, I suggest that you combine soda water with aqueous ammonia and natron (washing soda). This should give you aqueous carbonate of ammine, which can then be combined with vitriolate of magnesia (epsom salt) to produce your desired substance. All that is needed is to dry your substance. Plasmic Physics (talk) 04:56, 30 May 2012 (UTC)

The obvious place to look is Sulfuric acid#Manufacture (of course burning sulfur is dangerous). Icek (talk) 16:44, 30 May 2012 (UTC)

You could always bypass the calcification of brimstone - use vitriolic acid obtained as fresh battery acid. Plasmic Physics (talk) 19:44, 30 May 2012 (UTC)

It is much cheaper to just buy ammonium sulfate. Adding sulfur to soil is also a way to make the soil more acidic, by letting bacteria oxidise the sulfur to sulfate. You will need many kilograms of sulfur: do you have that much? Graeme Bartlett (talk) 22:00, 30 May 2012 (UTC)

What kind of latch ?

How is this type of latch called: X latch. Thanks for help! Grey Geezer 22:30, 29 May 2012 (UTC) — Preceding unsigned comment added by Grey Geezer (talk • contribs)

Maybe because its profile is vaguely X-shaped. Meanwhile, that website's purpose seems to be to pollute your screen with spam, so beware. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:35, 29 May 2012 (UTC)

No, it is not called X latch. I called it "X" - like "unknown name". Grey Geezer 22:44, 29 May 2012 (UTC) — Preceding unsigned comment added by Grey Geezer (talk • contribs)

Can you find it on a non-spam site? ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:49, 30 May 2012 (UTC)

No. If I would have found it elswhere (I tried), I would know the name, right? Someone needs the name and uploaded it to the US-Imageshack site. Sorry. Grey Geezer 05:07, 30 May 2012 (UTC) — Preceding unsigned comment added by Grey Geezer (talk • contribs)

Here is the same image on imgur. The latch in question is called a draw latch. This particular one is a type with both a rubber arm and an over-center(?) pull. (I'm not certain of my vocabulary here. Perhaps it would be called a lever assisted rubber arm draw latch.) Note that in the photo, the cover or hood to be latched down is not in place, and so the latch is just "resting". Our latch (hardware) article does not offer very many illustrations and would benefit from a gallery of latch types. It does no more than admit to the existence of an animal called the "draw latch".-- 203.82.95.184 (talk) 06:29, 30 May 2012 (UTC)

This comes close. The correct (German) term is (=> GoogleImages) "Schaufelhalter" (shovel holder) but with "shovel holder" I could not find similar devices. Thanks everybody! Case closed. Grey Geezer 07:30, 30 May 2012 (UTC) — Preceding unsigned comment added by Grey Geezer (talk • contribs)

Color does not actually exists?

Is it true that color does not actually exists but is a figment of human anatomy (and a figment of living creatures' anatomy). That is to say in a universe devoid of life , there is no concept of color. 202.177.218.59 (talk) 23:09, 29 May 2012 (UTC)

I'd say yes, colour is just a construct facilitated by organisms to interpret different frequencies of light to receive information from the environment. Plasmic Physics (talk) 00:06, 30 May 2012 (UTC)

There is electromagnetic radiation and it comes in different frequencies. Our eyes and brains interpret a narrow (but rather useful) band of these frequencies as the qualia we call "color." The same can be said about sound (interpretation of pressure waves), taste and smell (interpretation of chemicals detected), and touch (interpretation of physical structure). All of our senses are equally "unreal" in that sense; it is what makes qualia interesting from a philosophical point of view. --Mr.98 (talk) 00:47, 30 May 2012 (UTC)

"Concept" is a human invention. In a universe devoid of life, there would be no concept of anything. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:48, 30 May 2012 (UTC)

This is really a question of ontology. Color does indeed seem not to exist in a "physical" sense; as in there is no such thing as an "atom" of color. However I don't believe it can be said that color does NOT exist as a real property of matter. I've heard it described as a "meta-property" or an emergent property. The thing that really complicates the issue is that color is NOT just a property of the wavelength, for example in some optical issusions, one wavelength of light can appear as two completely different colors, but I think that just means that our perception of the "property" is more complicated, not that it doesn't exist at all. Vespine (talk) 01:12, 30 May 2012 (UTC)

The Church–Turing–Deutsch principle implies that qualia are just computational states of computer programs. Count Iblis (talk) 01:21, 30 May 2012 (UTC)

That seems to assume at least a couple of unstated premises. According to the article you linked, that principle "states that a universal computing device can simulate every physical process". To get your conclusion, you seem to need to know two extra things: That qualia are physical processes, and that being simulable by a universal computing device is the same as being a computational state. --Trovatore (talk) 02:27, 30 May 2012 (UTC)

To say that "color does not exist" is rather a bad way of putting it. It's the sort of thing that makes scientists sound really smart to some people, but it is not, strictly speaking, true. Light (and hence, color) is "seen" by humans and other living creatures as the most directly observable byproduct of electromagnetic radiation in the visible spectrum. Colors are not observed by every species (or even every individual) in the same way, so the experience of color is subjective, but that doesn't make it any less existent. Color exists as much as FM radio does. Evanh2008 ^{(talk|contribs)} 02:04, 30 May 2012 (UTC)

Color as a perception is a figment of human anatomy. Color as the wavelength of light (which causes the perception) is a property of light. There would be no concepts at all without life. B^e——C_ritical 02:58, 30 May 2012 (UTC)

David Eagleman makes the point (argues) that even different people percieve color (=> => interpret a "color" via the brain) differently. Your Blue is not my Blue. Grey Geezer 05:11, 30 May 2012 (UTC) — Preceding unsigned comment added by Grey Geezer (talk • contribs)

If a tree falls in a forest... --LukeSurl ^{t c} 23:14, 30 May 2012 (UTC)

FWIW, "perception of colour" is a pretty big topic. It varies from person to person (typical people can differentiate on the order of a million colours), animal to animal, by source of light etc. The exact same "colour" may appear bright red or bright green -- depending. This is far different from colour as bing a wavelength of light - which has a definable value. Collect (talk) 23:23, 30 May 2012 (UTC)

Colour results because of light and how that light reflects refracts absorbs on /off any given surface. It is the the structure of the surface of the object the light hits that will ultimately determine its colour. With out light there is no colour, and with out the surface there is no colour. For example a Bluebird's feathers are blue because of the way the feathers are placed and structured. Change that structure and the Bluebird will not be blue. Second, how light is perceived is as Collect says a huge field. But animals including human being's eyes are all structured differently. Even within human beings there are different eye structures. Male and female human beings have a different eye structure for example. Eye structure is the tool which "sees" colour but until the brain and eyes connect there is no perception of colour.(olive (talk) 20:04, 31 May 2012 (UTC))

A surface is usual, but the light source is part of it also. One can perceive color by looking directly at a light source, rather than a reflective surface. And the light reflected is also partially determined by the light source, that is what colors in what intensity are present in the source. A light source may have only one wavelength -as a laser- or many, and will usually favor certain colors, as the sun favors yellow. B^e——C_ritical 18:10, 1 June 2012 (UTC)

I guess I'm referring to the sun as light source without which there would be nothing visible coloured or otherwise and no other source of light would have been possible in our history, but my view comes out of colour theory for art so has a specific slant and or limitation, I suppose.(olive (talk) 19:09, 1 June 2012 (UTC))

Good or bad edit?

Can someone with a bit more familiarity with messier objects please check whether this was a good faith edit or vandalism and do what is appropriate? It's rare that you can't tell but here I have no idea—I could spend the time educating myself, but I'm sure someone with familiarity can do this much more economically.--Fuhghettaboutit (talk) 23:25, 29 May 2012 (UTC)

Bad. Only three in Puppis. (M46, M47 and M93 - I'll admit I had to look that up) FlowerpotmaN·(t) 23:31, 29 May 2012 (UTC)

Edit reverted FlowerpotmaN·(t) 23:32, 29 May 2012 (UTC)

Thanks Flowerpotman. I had a feeling it was vandalism, based on the magnitude of the change.--Fuhghettaboutit (talk) 23:55, 29 May 2012 (UTC)

No problem. I had to check how many there actually were in Puppis, but I did know there were 110 Messier objects and only 88 constellations, so, while they aren't evenly distributed.... well you can do the maths :) FlowerpotmaN·(t) 00:11, 30 May 2012 (UTC)

To be honest, I'd probably ABF simply because of the username... Brammers (talk/c) 23:07, 30 May 2012 (UTC)