Wikipedia:Reference desk/Archives/Science/2014 October 31

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October 31

Leclanché cell and Vanadium redox battery

1. What is the total chemical equation for both batteries separated into equations at the cathode and the anode e.g.

Negative plate reaction:

Pb(s) + HSO⁻
₄(aq) → PbSO
₄(s) + H⁺
(aq) + 2e⁻

Positive plate reaction:

PbO
₂(s) + HSO⁻
₄(aq) + 3H⁺
(aq) + 2e⁻ → PbSO
₄(s) + 2H
₂O(l)

The total reaction can be written as

Pb(s) + PbO
₂(s) + 2H
₂SO
₄(aq) → 2PbSO
₄(s) + 2H
₂O(l) (From Lead–acid battery)

2. Is the Vanadium redox battery a fuel cell or secondary battery

Please ping my user using the {{yo}} template when answered Retartist (talk) 02:48, 31 October 2014 (UTC)

EDIT: Leclanché dry-cell batteries as opposed to the wet cells. Retartist (talk) 03:19, 31 October 2014 (UTC)

@Retartist: See Zinc-carbon battery, Vanadium redox battery, and Flow battery. This is also a useful introductory treatment of the VRB.

The equations for the zinc-carbon battery are:

• Negative electrode: Zn → Zn²⁺ + 2 e⁻
• Positive electrode: 2MnO₂ + 2 e⁻ + 2NH₄Cl → Mn₂O₃ + 2NH₃ + H₂O + 2 Cl⁻
• Overall: Zn + 2MnO₂ + 2NH₄Cl → Mn₂O₃ + Zn(NH₃)₂Cl₂ + H₂O

Note that the carbon of the positive electrode does not take part in the overall reaction, it's just to provide an electrically conductive path.

For the VRB:

• Positive cell: VO²⁺ + H₂O → VO₂⁺ + 2 H⁺ + e^-
• Negative cell: V³⁺ + e^- → V²⁺
• Overall: V²⁺ + VO₂⁺ + 2H⁺ ⇄ VO²⁺ + V³⁺ + H₂O

On the second question, "both" is probably the best answer. The reaction chamber itself is a fuel cell; the overall system (reaction chamber + storage tanks + pumps + control gear) is a secondary battery. Tevildo (talk) 10:08, 1 November 2014 (UTC)

Smelloscope

Now that it has become possible to predict the smell of a compound ab initio, is it possible to invent a Smelloscope? Plasmic Physics (talk) 04:03, 31 October 2014 (UTC)

You should probably check out Machine olfaction, There have been efforts to build artificial noses - computers that can detect odors. But generally they are only attuned to a particular limited set of smells. But since we have effective spectroscopes, which can analyse just about any chemical - I don't see why a general purpose "smelloscope" shouldn't be possible. SteveBaker (talk) 04:17, 31 October 2014 (UTC)

The image at right is only tangentially relevent...but for some reason I find it hilarious! SteveBaker (talk) 04:18, 31 October 2014 (UTC)

Just clarifying, I'm referring to a machine that generates a smell instead of detecting it. It would be interesting to smell the air on Io (moon) from the comfort of an observatory. Plasmic Physics (talk) 04:24, 31 October 2014 (UTC)

Yes, just as soon as we invent a machine to automatically synthesize any conceivable chemical. I think that would have just a few more applications than a smelloscope. 70.190.182.236 (talk) 04:37, 31 October 2014 (UTC)

Therein lies the crux of the recent achievement which I implied with my opening query. It is not necessary to synthesise the exact compound. Recently, a group of researchers tested an algorithm for simulating practically any conceivable odour based on its structural properties. They also invented the white noise equivalent of smell, which cancels out other smells. Plasmic Physics (talk) 04:49, 31 October 2014 (UTC)

Worth remembering that of all the many attempts at Digital scent technology, it's not entirely clear if the problem has been that they weren't able to produce a sufficiently accurate and broad range of scents, or other factors such as a believed lack of interest. It's possible a focused attempt aimed to produce any smells (edit: for exotic purposes like allegedly smelling Io or other stuff a person has little chance of smelling) will have more success, but may be not. Edit: Reading some of the discussion surrounding what you're referring to, I was also reminded of one recent attempt, the oPhone accessory. [1] May be this accessory will have more success than all the other previous attempts, may be not, I don't think it's clear if it does fail, the lack of their support for what is claimed possible by this recent research will be a big factor, except perhaps for the "smell cancellation" idea. In fact, some of the discussion mentions some of the possible reasons for failure, e.g. smell persistance. BTW in case there's any confusion, the team who came up with the algorithm recently appear to be largely unrelated to the Israeli team who came up with the "white noise" concept in 2012. [2] [3] Nil Einne (talk) 22:34, 31 October 2014 (UTC)

Hyperventilating

What is the name for the condition whereby too much oxygen in the lungs/blood causes a person to hyperventilate? KägeTorä - (^影_虎) (Chin Wag) 06:49, 31 October 2014 (UTC)

Oxygen toxicity causes dyspnea but it tends to result in coughing instead of hyperventilation. 71.215.67.106 (talk) 07:41, 31 October 2014 (UTC)

Yes. Hyperventilation is usually a result of lowered CO2 in the blood, not and increase in oxygen (although taken as a ratio, the end result would be a higher O2/CO2 ratio). The term for this is Hypocapnia. See also Hyperventilating.--William Thweatt ^TalkContribs 07:47, 31 October 2014 (UTC)

I think that's the wrong way round - lowered CO2 in the blood can be caused by hyperventilation. "Hyperventilation causes an excessive intake of oxygen and elimination of carbon dioxide and may cause hyperoxygenenation. Hypocapnia and respiratory alkalosis then occur"[4]. Hyperventilation is usually caused by anxiety or some other physiological problems such as raised cranial pressure. There is also iatrogenic hyperventilation caused by overventilating a patient mechanically. Richerman (talk) 11:24, 31 October 2014 (UTC)

Definitely. I meant to type "...usually results in...", not "...is usually a result of...". Thanks for catching that. That's what I get for not using "show preview".--William Thweatt ^TalkContribs 13:16, 31 October 2014 (UTC)

Been there, done that :-) Richerman (talk) 13:42, 31 October 2014 (UTC)

Why do concrete bridges have slight arches at the bottom

Why do concrete bridges have slight arches at the bottom like this (http://www.historicbridges.org/bridges/browser/?bridgebrowser=concrete/fred/) — Preceding unsigned comment added by 194.66.246.9 (talk) 12:31, 31 October 2014 (UTC)

I separated this question from the one above --Lgriot (talk) 12:51, 31 October 2014 (UTC)

The same reason that any bridge has an arch - they allow for transfer of forces to columns that support the span, so that it can bear a load. Though that's one terse sentence, the linked articles are all pretty good, and have tons of relevant information. Of course not all bridges have to have arches, but arches are often a good choice. SemanticMantis (talk) 15:01, 31 October 2014 (UTC)

Oh, and in some cases the arches might not be structurally necessary, but are used to create extra clearance below. SemanticMantis (talk) 15:06, 31 October 2014 (UTC)

Concretes' strength is in compression. Moving weight from the center to the supports using an arch is similar to how stone masons used arches. The center supports the least amount of weight.. Compare it to a steel suspension bridge where the arch of the suspension cable is reversed as steel is stronger in tension. --DHeyward (talk) 03:05, 1 November 2014 (UTC)

And the reason that concrete only needs a slight arch, rather than the full semi-circular arches required for brickwork, is that it is in the form of prestressed concrete. Alansplodge (talk) 08:43, 1 November 2014 (UTC)

Meteorite impact and electron degeneracy

When a very large bolide impacts on the Earth (100 km diameter), are the instantaneous pressures generated enough to approach the levels required for electron degeneracy, or does this phenomenon occur only in stars? Such an impact will drive zillions of tonnes of rock several kilometres into zillions of tonnes of rock, with nowhere for anything to flee. The "empty space" normally found around the nuclei must be eliminated. Does the shock wave force the electrons in the silicates into the nuclei of the atoms for a fraction of a second? Extending this line of thought and given a hyperbolic exponential stellathermal rifle of science fiction, with nearly infinite energy and muzzle velocity, is it possible to produce a black hole with a bullet and a planet? Captainbeefart (talk) 13:17, 31 October 2014 (UTC)

While there is no doubt that a large impactor could partipate in an incredibly energetic collision event, your extrapolations seem unlikely. We have never observed such an event directly - the closest we have seen is the impact of Comet Shoemaker-Levy a few years ago.

I suspect that the impactor would dissipate energy much too quickly for it to concentrate at the scales you describe. Collisional impacts cause ablation, thermal heating, and material deformation; all of these are great ways to move energy away from the boundary, quickly, before the energy reaches thermonuclear-scales. On the other hand, if we are hypothesizing any such impactor of arbitrarily-large size... well, our current understanding of stellar formation is essentially this exact process! Massive amounts of matter - mostly free neutral hydrogen - coalesces (in other words, "collides"), and the energy of its own self-gravitation is sufficient to stoke the fires of nuclear fusion!

There is a great review of the scientific state-of-the-art understanding of impact events in Planetary Science. Nimur (talk) 15:54, 31 October 2014 (UTC)

PUJT vs DIAC

Any ideas why using a PUJT would be preferable to using a DIAC as a triggering device in the 1980s? More specifically why one would want to change a working circuit to use a PUJT (configured for the same triggering voltage) rather than a DIAC?--86.176.23.223 (talk) 13:23, 31 October 2014 (UTC)

[See UJT and TRIAC for other relevant articles]. The best device to choose will depend on the application circuit, so it's not really possible to answer this question in the abstract. However, some possible advantages of UJT's are:

• Cost. Not really an issue for a hobby circuit, but definitely one for industrial applications.
• Threshold variability. With a UJT, it's possible to control the trigger threshold quite precisely - if the exact trigger level is important, a DIAC might have too variable a threshold voltage to be reliable.
• Speed. Normally the limiting factor here will be the speed of the TRIAC (or other switching device), but if you have to switch something very quickly (and you want to stay with solid-state devices), a UJT will give you a cleaner edge than a DIAC.
• Trigger current. Again, not normally an issue with TRIAC circuits, but if you need to dump a lot of gate charge very quickly when the trigger fires, the UJT will give you a higher "on" current than the DIAC.

Tevildo (talk) 20:37, 31 October 2014 (UTC)

And pulse rise time might be shorter with a PUJT. loupgarous (talk) 00:39, 4 November 2014 (UTC)

Insect overwintering

There are several articles on WP that discuss "hibernation" as an overwintering strategy for insects. However, the hibernation page says this is specific to endotherms. Can somebody definitively clarify: do insect hibernate? (I do not think so, but again, articles are poorly sourced). Is it correct then to say that they overwinter in diapause? Or should I keep it vague and say "overwinter" or "enter a stage of dormancy"? This is for the article Megachile campanulae. Thanks! —Gaff ^ταλκ 14:28, 31 October 2014 (UTC)

Right, "hibernation" as a technical term is reserved for a specific type of metabolic process, and it would technically be wrong to say an insect hibernates. However, as with many scientific terms, "hibernate" is used in English to refer to any number of animals that go dormant over winter. I believe diapause is correct for many temperate insects that "delay in development in response to regularly and recurring periods of adverse environmental conditions." For the Megachile specifically, they overwinter as pupae or prepupae or (pre-pupae) [5], though we don't have articles on the latter. I suppose it's not clear whether the overwintering pupae in your case have delayed development compared to putative mid-summer pupae (do they have multiple generations per season?), but I still think "diapause" is much better than "hibernate," and I would fully support the avoidance of hibernation terminology for insect articles. SemanticMantis (talk) 14:49, 31 October 2014 (UTC)

Thank you. —Gaff ^ταλκ 02:25, 1 November 2014 (UTC)

Bridge supports

What would happen if you fixed both ends of a bridge so they have no degrees of freedom? Would it just break? — Preceding unsigned comment added by 194.66.246.9 (talk) 15:21, 31 October 2014 (UTC)

Yes. "If both ends are provided with fixed bearings, internal stresses are sure to develop in bridge components." Get enough of those internal stresses, and your bridge will break. - Eron^Talk 16:32, 31 October 2014 (UTC)

We should be careful about what kind of bridge we're discussing here. There are plenty of small arched, stone bridges spanning small rivers and streams that are completely anchored to both banks and have stood for hundreds of years. So the size, materials and design are all factors here. But for sure, something large and made of steel could easily break from thermal expansion alone if it were firmly anchored. SteveBaker (talk) 17:12, 31 October 2014 (UTC)

Exactly! As Steve correctly points out, there are plenty of counter-examples. Not every bridge will break if the ends are firmly anchored!

Civil engineers (or anyone who studies structures or engineering statics) know that anchoring the ends of a cantilever will change the distribution of static and dynamic forces. If these changes cause a force that exceeds the material's safety limit, the structure will be damaged. If the bridge is intentionally designed to withstand those forces, the structure should not be damaged. It's almost common-sense!

The OP has probably read about suspension bridges - in some of the most famous examples, a suspension bridge is designed such that the support structures that bear the load need to be able to flex. In particular, the Golden Gate Bridge and the San Francisco Bay Bridge are examples where the bridge is specifically designed to "flex." Fixing the end-points would require a stronger suspension, bigger and sturdier towers, and heavier (stronger) catenaries and roadways. Those wouldn't be good engineering trade-offs for these bridges.

However, a bridge can be designed to have strongly anchored ends.

Nimur (talk) 17:28, 31 October 2014 (UTC)

Note that the local geology is important to answer this Q. If there are earthquakes or if one side is subsiding at a different rate than the other, for example, then flexibility on at least one end support is critical. StuRat (talk) 17:53, 31 October 2014 (UTC)

Measurement query

Hello. I would like to know, how much water do you need to dissolve 100g worth of stuff. What’s the sufficient amount (ml)?

(Russell.mo (talk) 18:08, 31 October 2014 (UTC))

It depends on what the stuff is, and at what temperature. See Solubility and Solubility_table for starters. SemanticMantis (talk) 18:13, 31 October 2014 (UTC)

Whoah, you gave me something that will never enter my brain. I got Double 'X's in science. Can you please let me know in simple terms please?

This is what i need to know,

100g's of solid, how much water (ml) do I need?

With Cold/normal water, I'm assuming not much, 500ml is more than the necessity. things will dissolve overnight...

With hot water? - I guess enough to make it 500ml after boiling... Note, if boiled the solid give more out of the 100g product.

(Russell.mo (talk) 04:36, 1 November 2014 (UTC))

I don't think every substance is water soluble. Petroleum, for example. But as Semantic said, the amount of water could be different depending on the substance. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:31, 1 November 2014 (UTC)

You need to tell us what the "stuff" is before we can answer your question. For example, from the link provided by SemanticMantis you can calculate that to dissolve 100g of ordinary salt you need just over a quarter of a litre of water close to boiling point, and about 280 ml of water at freezing point. For a similar substance formerly sold as weedkiller, you need only about an eighth of a litre of freezing water (no ice), and only 50ml of boiling water to dissolve 100g because this substance is much more readily dissolved at higher temperatures. If your "stuff" happens to be Potassium tetraphenylborate or Silver bromide then you would need a whole reservoir of more than a million gallons of water to dissolve it, or if it was Bismuth sulfide, then you would need nearly 2000 times the volume of the Mediterranean Sea to dissolve your 100 grams. At the other extreme, 100 g of Caesium acetate should dissolve in just 10ml of water! Dbfirs 09:00, 1 November 2014 (UTC)

Ammm, I think you guys are in the chemical laboratory and I'm in the kitchen!

Say raw garlic, ripe tamarinds, raw meat, any kind of food type solid 100g per product, how much of hot and cold ml/l of water do I need? I just want to know the average measurement of all products. I don't know how to explain it to you guys. The two examples dbfirs mentioned, one is powders, one is rock. I pretty much understand that for rock kind of thing, over quater of a litre (boiling point to what ml?). and for powder, I get the idea.

(Russell.mo (talk) 18:48, 1 November 2014 (UTC))

If you want to know this stuff for cooking reasons, I'll add that in my experience, spices, herbs, pastes etc. always have enough water to dissolve in. Also, I don't think most flavor compounds need to be fully dissolved to be tasty. I don't think raw meat will usually dissolve in water, but if cooking is your goal, I recommend experimenting and asking questions about specific foods. SemanticMantis (talk) 19:29, 1 November 2014 (UTC)

If you wanted to know about cooking, why did you say "dissolve"? Dbfirs 20:26, 1 November 2014 (UTC)

Dbfirs is right...the specific meaning of "dissolve" might be the reason you're not getting the kind of answer you are expecting. Consider salt or sugar, they dissolve to make a clear "solution". No matter how you filter it (slotted spoon, sieve, cheese-cloth, coffee-filter, etc.) you always have that same liquid. But when you put garlic and water in the blender, you get a cloudy slurry (a suspension) that can be filtered to give garlicy water and still the approximately same amount of solid you started with. That's not "dissolving", just "mixing the two components pretty well for now"--separable by physical means.

There's an upper limit (as others have noted) for how much of each specific material will dissolve in a certain volume (or the minimum amount of liquid it takes to dissolve a specific amount of a specific material), but it depends on the material--some materials are inherantly more soluble than others in various specific liquids, and the effect also strongly depends on temperature. Even between salt and sugar, you can dissolve different amounts in a cup of water, and you can dissolve different amounts of salt in a cup of cold water vs hot water, and in water vs vodka. But for a simple slurry, you're just mixing, so you can pretty much mix in any ratio you want. Many ground spices don't seem to dissolve at all in water--you can see specks of cinnamon dispersed throughout a sugar cookie--and it doesn't matter. DMacks (talk) 04:02, 2 November 2014 (UTC)

Thanks guys. Apologies.

I understand the difference between the word 'mixing' and 'dissolving' now, but I did meant what I said.

I want to acquire knowledge of how people create drinks in general. I know it is a completated task, I just wanted to have a general idea. I wanted to know how a product can be dissolved completely. I know they do it with water but how and to what extent with boiling/freezing point.

Salt measurement I understand, as dbfris mentioned. Salt and sugar makes clear solution I agree, I wanted to know how can you get the most out of a product. Of course by boiling, and now I know it is possible with freezing water too. I thought boiling a product will dissolve it to its extent rather than blending. All you have to do next is "filter it" thereafter... E.g., Raw meat, I thought boiling it will give the maximum out of it. But I guess you can't boil meat to dissolve it as SemanticMantis mentioned. I did try this once but it boils the product it doesn't dissolve it with water.

So, isn't there is an average, for a soluable product?

(Russell.mo (talk) 07:41, 2 November 2014 (UTC))

No, if you look at my extreme examples above, you will see that an average would be meaningless. In the case of foodstuffs, the usual advice is "just enough to cover the solid", and you are correct that temperature makes a big difference. Food cooks faster (and soluble substances dissolve faster) at higher temperature, hence the use of pressure cookers. In the case of good cuts of meat, I think most chefs try to keep the maximum in the meat, not "out of it".Dbfirs 08:05, 2 November 2014 (UTC)

I was imagine of a meat drink, chicken drink... (not chicken soup). Do you get what I'm saying? You must have seen in the shop the dry raw meat slices sold in packets... I was just wondering about a meat drink. Garlic, you can get something out of it while boiling but can't dissolve it like salt and sugar, until or unless its garlic powder for example. The only difference would be colour... Also if you boil it too much the water vapourises, water decreases in result. I wanted to level the ml of water in one go. If I use a similar method to a pressure cooker, I don't know, maybe the water will stay if I don't let it out. Btw, I learnt what you said about the meat Dbfris. Good to know. Thanks.

Sorry about the misunderstanding again everyone, I meant to say, I was experimenting in the kitchen while you guys are experimenting in the laboratory. Please considering re-understanding what I write and mean, all the time.

Thank you all!

(Russell.mo (talk) 09:04, 2 November 2014 (UTC))

Kitchen or laboratory; potato or potatoe - the laws of nature don't care. Plasmic Physics (talk) 22:29, 2 November 2014 (UTC)

If you want to suspend chicken in water, a blender is probably the way to go. Chicken probably won't dissolve completely in water no matter how long you boil it, so you chop it up into little bits that take a very long time to settle. How much water it takes to suspend a given amount of chicken would depend on a few things like how finely chopped up the chicken is and what else is in the water. Something like xantham gum or perhaps crushed ice could be used to thicken the water and make it easier to suspend the chicken. You'll probably have to experiment to find the right amounts of the different components, though you might be able to get some guidance by searching online for blending recipes.--Wikimedes (talk) 09:05, 4 November 2014 (UTC)

I've checked internet, I was looking for an ultimate solution regarding achieving maximum out of any cooking product by dissolving it. I understand now that not all products can be dissolved at a high temperature, in water, though can be blended. Halted via the sense as dissolving was the main aim. -- (Russell.mo (talk) 17:02, 4 November 2014 (UTC))

Space Vacuum confusion

What do you mean by ‘space’ is a ‘vaccum’?

(Russell.mo (talk) 18:09, 31 October 2014 (UTC))

It means that there is an almost complete absence of gas molecules in outer space which is the void beyond the Earth's atmosphere and between all other objects in the universe. see:[6] Richerman (talk) 18:34, 31 October 2014 (UTC)

The word "vacuum" means "empty".[7] The universe as a whole is obviously not empty, but a given reasonable-sized cubic volume in space is very, very close to being literally "empty". — Preceding unsigned comment added by Baseball Bugs (talk • contribs) 19:08, 31 October 2014 (UTC)

Air (and other gasses) are pulled toward stars and planets by gravity - so the spaces between those bodies has very, very little gas at all. Here on earth, there are around 200,000,000,000,000,000,000,000 atoms of gas in every cubic foot of air, but in the open space out between the stars there are about two atoms in every cubic foot...which is near-enough *nothing*. The "nothing" is what we call a "vacuum". When you encounter so-called vacuums here on earth (like in a vacuum-cleaner), we're really talking about 'partial' vacuums...where there is less gas...but perhaps not much less. The best vacuum made here on earth is still about a million atoms per cubic foot. SteveBaker (talk) 19:52, 31 October 2014 (UTC)

Someone told me there is no (air) in space. the weather means cosmic dust issues, solar radiation issue and so on, no air. I thought to myself once space air is another reason why we have weather effects on planet earth...

O, I think I understand. I was confused with the word vaccum cleaner, when it was used in the WP article. Just to clear the thought, so, there is nothing pulling the atomsic particles like a vaccum cleaner, rather than the planets, astroids, meteorid, gravities, also the Sun is pushing the atomic particles with its rays to the insteller medium, right?

(Russell.mo (talk) 04:49, 1 November 2014 (UTC))

A Vacuum cleaner uses an air pump to create suction, pretty much the same technology you would use to create a vacuum in a light bulb or whatever. The difference is that a vacuum cleaner only creates a partial vacuum within its hose and attachments. Whatever air it pulls through is expelled as the dirt catches in the filter, so the air pressure in the room stays effectively constant. The sun and other stars push particles away, while massive bodies like the earth pull them in - if they get close enough; otherwise they just scatter. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:29, 1 November 2014 (UTC)

Er...some corrections: Light bulbs haven't had a vacuum inside for about 40 or 50 years! Stars both push and pull...it's complicated! Their gravity pulls stuff inwards - and "radiation pressure" or the "solar wind" pushes it outwards. To what extent one wins and the other one loses is complicated! Our sun is in pretty good balance - but eventually, in a few billion years, radiation pressure will win out for a while and the sun will grow until it almost engulfs the earth - and a long time after that, it'll run out of fuel and collapse into a tiny ball as its gravity finally wins out. It's complicated! SteveBaker (talk) 14:04, 1 November 2014 (UTC)

Large wattage incandescent bulbs contain inert gases, but low wattage incandescent bulbs may indeed contain a hard vacuum. Edison (talk) 19:54, 1 November 2014 (UTC)

The term "weather" in space usually refers to the particles, radiation, cosmic rays, light and radio waves put out by the sun in an irregular fashion. We have an article called "Space weather" that explains all of this. We actually try to predict space weather in advance, just like we predict atmospheric weather here on earth...it's useful to know whether the sun is about to push out a gigantic amount of radiation so that our satellites and astronauts up there in orbit can take protective measures until the radiation passes them. It's kinda like weather here on earth - but it has very little to do with "atmosphere".

We also talk about "cosmic dust clouds" - and you see gorgeous photos of such things. This leaves you with the impression of a gritty dust cloud like you'd get from a car driving down a dirt road...that's kinda correct - but there is much MUCH less dust in every cubic foot of these cosmic dust clouds...if you were in the middle of it, you'd have to travel miles to find even one grain of dust. It looks dense in a telescope because you're seeing through millions of miles of the stuff.

SteveBaker (talk) 14:04, 1 November 2014 (UTC)

In regards to star pushing and pulling, I understand, I read through some WP articles. I am stuck somewhere I can't recall now. I've also read the Space weather article, I'm just surprised that there is no air at all. it doesn't make sense. I saw NASA youtube videos. It seemed to me like space has air...

Apparently it smells like arc welding, something, when you are in space in your space suit, outside the spaceship.

I still don't understand why they use the word 'vacuum' they could simply say void/empty and so on. The first thing that comes to my mind when I hear the word is, a 'sucker'.

How does the a core formation start anyway? I read through some WP articles, I guess gravity molecules contracts together with all the grains and other molecules what is available in the interstellar medium. Also Supernovae blast ray/plasma creates denses areas where there are/if molecules gathered during its passing through... How does it rotate? During its slightest clashing with the molecules in the interstellar medium, plasmas passing through...?

What gets created first, a star or a planet? I understand it entirely depends on the particles available, but to this time, I have not heard a planet got created first then a Star or a planet got created without a star... surely a star gets created in the nebula (gas cloud) What if there is no gas cloud, and its in the interstellar medium or in a dense place where plasma rays passed it through...?

I understand the accretion part, what I don't understand does a star go from a protosteller to a blue stagger (depends on the molecules I guess plus blue stagger is a hypotheses)? then yellow, then red, then white, than black? And what's black hole? It seems to me that it is like the vacuum word, its actually not a black hole, where you can jump in, not like a drain cover what you find in the street, its a black star.

(Russell.mo (talk) 18:20, 1 November 2014 (UTC))

You have to realize the real volume comparrison of space and matter. We usually think for example our Moon is "near" but it is actually up to 400.000 km away from us. To make it more imaginable - the radius of our Earth (~ 6.500 km) fits 62 times in that distance. Its likely caused by all the Orrerys that are completely out of proportion. In a proportional Orrery you would not see/find the small planets. You would need a magnifying Glas and you would need to know where to look. You could also ask the other way around why it is that there are some atoms that far "out there". --Kharon (talk) 05:41, 2 November 2014 (UTC)

Additionally you may want to read Solar_System_model#Scale_models_in_various_locations. --Kharon (talk) 05:52, 2 November 2014 (UTC)

I get what you are saying. : I -- (Russell.mo (talk) 09:07, 2 November 2014 (UTC))

This discussion has been closed. Please do not modify it.
The following discussion has been closed. Please do not modify it.
'Vacuum' is a relative word, meaning that it is always used in relation to a reference subject which is not a 'vacuum'. The word itself means 'at reduced pressure'. When a two volumes of gas at different pressures, are exposed to one another, they spontaneously equilibrate, which means that they automatically strive to set up an equilibrium state of zero pressure difference. This is because of the statistical observation of all matter naturally tending toward higher entropy, or 'disorder'. (The same reason why adding hot water to cold water gives you lukewarm water, but instead of temperature, think in terms of matter itself) Consequently, there will be a net motion of gas for as long as it takes to establish equilibrium. In a vacuum cleaner, the idea is not allow an equilibrium to be established, by creating a continuous pressure difference. This causes a continuous flow of air, creating the familiar 'sucking' behavior. Since space is at a greatly reduced pressure compared to atmospheric pressure on Earth, it is considered to be a vacuum. The reason why the Earth's atmosphere is not 'sucked away' into space, is because of the Earth's gravity is creating an equilibrium state, whereby a pressure difference is allowed, regardless. Mind you, this pressure difference is graded, not precipitous. Plasmic Physics (talk) 22:54, 2 November 2014 (UTC) The word "vacuum" actually means empty, not "reduced pressure". Comparing two cubic spaces for relative fullness or emptiness figures into it certainly. But "vacuum" is of the same root as words like "vacate", "evacuate", "vacuous" and even "vain". ←Baseball Bugs What's up, Doc? carrots→ 23:17, 2 November 2014 (UTC) Not in the scientific sense - there is no such thing as a vacuum that is truly devoid of any and all manner matter. This is for the same reason as absolute zero does not exist. Plasmic Physics (talk) 00:42, 3 November 2014 (UTC) True. But the word "vacuum" DOES NOT mean "at reduced pressure". It means a given cubic volume that for practical purposes is sufficiently close to being empty that we can consider it to be a vacuum. ←Baseball Bugs What's up, Doc? carrots→ 03:41, 3 November 2014 (UTC) I can't agree with that. First find me an authoritative source which exclusively supports your assertion of the extreme case. Even our own article agrees with me. Besides, if I was wrong, then 'vacuum cleaner' is a misnomer, so such extreme is facilitated. Plasmic Physics (talk) 03:54, 3 November 2014 (UTC) You first. Find me a source that contradicts the dictionary definition of "vacuum". ←Baseball Bugs What's up, Doc? carrots→ 17:33, 3 November 2014 (UTC) Isaacs, Alan; Daintith, John; Martin, Elizabeth, eds. (2003). "V". A Dictionary of Science (4.1 ed.). Oxford University Press. p. 817. ISBN 0-19-860757-1.. ...Your turn. Plasmic Physics (talk) 23:07, 3 November 2014 (UTC) I should buy a book just so you can prove your point? No. Give me a quotation. ←Baseball Bugs What's up, Doc? carrots→ 23:21, 3 November 2014 (UTC) Vacuum A space in which there is a low pressure of gas, i.e. relatively few atoms or molecules... Plasmic Physics (talk) 23:28, 3 November 2014 (UTC) Yes, that's correct. "The word itself means 'at reduced pressure'," is incorrect, nor does your source make that claim. ←Baseball Bugs What's up, Doc? carrots→ 23:33, 3 November 2014 (UTC) How can you possibly make such a clearly contrary assertion? 'Reduced' is synonymous with 'lowered'. Granted, my statement is not a verbatim copy, but that is the nature of paraphrasing. If anything, it refutes your definition, as there is no approximated mention of a "volume that for practical purposes is sufficiently close to being empty". Plasmic Physics (talk) 23:51, 3 November 2014 (UTC) That author has correctly defined what a vacuum is, "for practical purposes", because achieving a true vacuum in the lab is not possible, but can be "close enough" for experimentation. The air atop Mt. Everest is 'at reduced pressure' compared with what it is at sea level. But we don't call the top of Mt. Everest a vacuum. Because it isn't. And the word "vacuum" itself does not mean and never has meant 'at reduced pressure'. ←Baseball Bugs What's up, Doc? carrots→ 03:14, 4 November 2014 (UTC) Well, I defined it as exactly the same as the author, emphasising the subjectivity of the adjectives used. If you take issue with how the Oxford science dictionary defines a word, take it up with them, not me. Your argument is a semantically-based distraction from my original statement. Plasmic Physics (talk) 03:22, 4 November 2014 (UTC) Nowhere does that author say that the word vacuum means 'at reduced pressure'. And his explanation of what a practical vacuum is fits totally with my understanding of it. ←Baseball Bugs What's up, Doc? carrots→ 03:32, 4 November 2014 (UTC) I've already explained that "low pressure" is the same as "reduced pressure", and that 'few' is a subjective term. Nowhere does it support your view that I'm wrong. Now please drop this pedantic argument, it is starting to become disruptive. Plasmic Physics (talk) 04:00, 4 November 2014 (UTC) It is your false and misleading definition of the word "vacuum" that is disruptive. Drop it yourself. ←Baseball Bugs What's up, Doc? carrots→ 06:42, 4 November 2014 (UTC) Check out the lengthy discussion of the word at Wiktionary. Nowhere in there does it define the word "vacuum" to mean 'at reduced pressure'. Nor have you found any source that says the word vacuum means 'at reduced pressure'. You made that up. Stop it already. ←Baseball Bugs What's up, Doc? carrots→ 06:48, 4 November 2014 (UTC)

And just to completely blow your mind, you should have a read of Vacuum state. Vespine (talk) 02:44, 3 November 2014 (UTC)

-- (Russell.mo (talk) 17:48, 3 November 2014 (UTC))

Could you please be more particular - what or which parts of our explanations confuse you? Plasmic Physics (talk) 00:38, 4 November 2014 (UTC)

If he's confused from vacuum state (which is far beyond the level of this discussion), it could be because of its extensive references to virtual particles, which I find to be a most confusing bookkeeping device. For example the Casimir effect that the article references can be explained far more simply as Van der Waals force without referring to virtual particles at all.

But to make sure the earlier discussion is clear: although you can blow with potentially unlimited force, you can only suck so hard. Given a straw (any size, any model) even someone with the lungs of a mythological harpy could suck up a watery drink at most 32 feet. After that there is simply no meaningful air above the liquid left to suck out, so the liquid won't be rising any higher. This distance is actually a measurement of the barometric pressure, the current weight of air pressing down on the Earth's surface over any given area. Barometric pressure can be measured by doing the same thing with mercury (and a vacuum pump, not a harpy); because mercury is heavier the air can raise it only a much shorter distance. But to be clear, when you suck air out of a straw, the air inside gets thinner and thinner the more you suck, rather than all being used up at once. The pressure of the air is pretty closely proportional to the total weight or number of atoms per a given volume - that's the ideal gas law. So if you suck water 16 feet up a straw, you know that the pressure inside the straw is half the pressure in the air outside. And the total volume of the thin air is also half of what it was when there were 32 feet of it in the straw. Together this means you've sucked out 3/4 of the air that was inside the straw to begin with. Similarly when the water is raised by 31 feet (only 1/32 of atmospheric pressure left), you've sucked out all but 1 / (32*32) = 1/1024 of the air inside.

The definition of a "vacuum" is somewhat elastic. It can mean anything from a relative vacuum that is produced by any small disturbance of the air, even closing a door in wintertime. It can refer to the perfect vacuum in vacuum state, which is only theoretically accomplishable by an infinite amount of effort. But in space it generally means a hard vacuuum which our article vacuum defines as less than 1 Torr or 0.1 Torr of pressure, which is 1/760 of a standard atmosphere pressure. So the 31-foot raised example above may or may not be called a hard vacuum. But space is a million times better than that - and far from planets or stars, a billion times better than that. Wnt (talk) 12:54, 4 November 2014 (UTC)

@Plasmic Physics: @Wnt:: What is sucking in space and from Which way? 1) If you through a ball in space which will never stop 2) but it will stay in one place if you leave it to float, does the vaccum effect it by pushing it in anyway? How heavy do you have to be to maintain a fixed state? -- (Russell.mo (talk) 17:13, 4 November 2014 (UTC))

Gravity sucks. Planets, stars, galaxies pulled in gas and dust as they formed, leaving the rest of space more barren. By now the flow is actually outward, solar wind from the heat of the sun, and loss of atmospheres of smaller worlds over time; this is because the ignition of fusion in the stars heated everything. But even if all matter were evenly distributed, it would be more or less vacuum due to the metric expansion of space. The universe is thought to have expanded particularly fast due to cosmic inflation early in history (a principle so vague and poorly understood that some say it is not even a testable hypothesis), but the Hubble effect shows that nearly all distant galaxies continue to recede from us to this day. With more and more space, the stuff in it is ever more spread out. The fundamental "pump" that increases this vacuum is thought to be dark energy, which is another very poorly understood concept, treated more like a mathematical formula than something you can identify and experiment with. Unfortunately the explanations of why space is the way it is are still not really all that much advanced over "it just came out like that". Wnt (talk) 17:57, 4 November 2014 (UTC) Wnt (talk) 17:57, 4 November 2014 (UTC)

'Sucking' a gas is a concept used by the scientifically uninitiated to refer to a non-existent illusion. Such people would think that sucking a gas means to pull it in a direction, but that is not what's happening. Gas is simply spreading out, or to put it in scientific terms, it is increasing its entropy. It spreads out because of the pressure differential discussed earlier, and it does so towards every direction where there is less pressure. This applies to space as well. Assuming, the ball in space is either solid, or not filled with gas, it's motion should be affected by solar wind. Unlike the atmosphere of planets which simply spreads out into space. Solar wind is actively repulsed from the Sun, therefore it acquires a net flow, away from the Sun. The ball should get caught up in this flow, because of the force of the impacting gas molecules. Plasmic Physics (talk) 20:45, 4 November 2014 (UTC)

@Plasmic Physics: @Wnt: Thank you (both) and all! -- (Russell.mo (talk) 16:47, 5 November 2014 (UTC))

Resolved

Warnings on prescription labels

Oftentimes, I will see on a prescription label a warning that says "Do not store this medication in the bathroom." Why is that? The only thing I can think of is that repeated use of the shower causes a lot of moisture and humidity in the bathroom, as opposed to any other room in the house. But, I have no idea if that is the idea behind the warning label. Does anyone know? Thanks. Joseph A. Spadaro (talk) 20:17, 31 October 2014 (UTC)

That's about it. Here is some guidance. [8] --Aspro (talk) 21:44, 31 October 2014 (UTC)

Thanks. So, I have two follow-up questions. Is the heat, temperature, moisture, and humidity really that significant? I wouldn't think so, but apparently it is? Also, prescription medications come in pretty sturdy containers. Those containers are not strong enough to keep out the moisture and humidity? Thanks. Joseph A. Spadaro (talk) 23:49, 31 October 2014 (UTC)

To keep out moisture and humidity you need a Hermetic seal. You haven't been specific about the type of packaging but if you are talking about screw-top containers there is no way you can achieve a perfect seal once it has been opened. The article linked to tells you that during testing "Products are subjected to temperatures and humidity levels within the recommended ranges on the Drug Facts label, and then tested to ensure it continues to meet its product specifications. This provides evidence that the product’s active and other ingredients are stable under storage conditions and that there is no growth of unwanted mold or bacteria" It goes on to say that they are safe and effective when stored according to the ideal conditions listed on the Drug Facts label. The corollary of that is that they are not guaranteed safe and effective if stored outside those parameters. Also, medicines in tablet form are produced from dry ingredients and designed to dissolve when swallowed. Let them get wet and they will lose their structural integrity and break up. As for temperature, the active ingredients have a known shelf-life at room temperature. Increase the temperature and there is more energy available, which increases the speed of the chemical reactions that break them down. Richerman (talk) 00:15, 1 November 2014 (UTC)

I can see you're using your commonsense. There are two parts. The vapour pressure of water is pretty high. Given a chance it will get into anything. The modern blister packs are designed to resist this. However, pharmaceutical companies (as you will know and understand) are not in existence to improve our health. Their duty is to return a profit to their share holders. So they place short shelf -lives on their products to encourage hospitals, health charities, etc to throw out their old stock and buy new. Are we throwing away 'expired' medications too soon?. Temperature also affects the speed at which chemical reactions progress. By the time one gets down to the temperatures of liquid nitrogen, chemical reactions have more or less come to a halt. Likewise, a medications left on the parcel shelf of a car in full sunlight are likely to degrade quickly. It does depend though, on how heat-liable the drug is. For instance, antique arrows tipped with curare still have to be handled with care, many decades after they were made.--Aspro (talk) 00:48, 1 November 2014 (UTC)

Some jars of tablets come with a sachet of desiccant included. From personal experience once opened even in normal humidity these tablets can absorb enough moisture in 2 months that the tablet expands to be too large to swallow or breaks apart. JMiall₰ 11:08, 1 November 2014 (UTC)

Thanks, all. Makes sense. Joseph A. Spadaro (talk) 15:32, 2 November 2014 (UTC)

Cell Phones on Cruise Ships

Please let me know if this question would be better asked at the Computing desk or the Miscellaneous desk. Can someone provide me with information about the technical details behind how mobile phones work on cruise ships? Here is what can be observed. First, the time displayed on the phone when the ship is in port or very close to port is the time of the port. (In Florida, it is EDT. In the Caribbean, it is EST.) Second, when the ship is not near port, the time switches to GMT/UTC. Third, when the ship is close to port, service is sometimes lost. Fourth, when the ship is not near port, service to the United States is available but is poor. My assumption is that when the ship is at sea, it uses satellite connectivity, and the satellite is using UTC. Does the ship have its own cellular antenna? If so, why can't the cellular antenna keep the cell phones on "ship time", that is, the time of the port where the ship is based? Does the ship's own antenna have a feature so that it doesn't provide its own time? Robert McClenon (talk) 20:28, 31 October 2014 (UTC)

Service varies by cruise line, but it seems many of the big ones use Wireless Maritime Services (WMS), a partnership between AT&T and MTN Satellite Communications. There is a lot of information available on their corporate site. Under "How does your service work", they say:

"Our service operates over a satellite, or “VSAT” connection. Once your ship is at least 12 nautical miles out to sea (or at least 2 nautical miles in EU countries), the WMS network turns on... Once your ship approaches land again and is within 12 nautical miles from shore (or 2 nautical miles in the EU), our service is turned off and your phone will pick up local service. If you are able to pick up local service in the port areas you will be charged a different rate by your carrier then the Cruise Ship Roaming rate. Contact your carrier for pricing and details."

Not sure about the time zone question. - Eron^Talk 21:39, 31 October 2014 (UTC)

That answers why service was lost when close to shore but not in port. The WMS was switched off, but the ship wasn't close enough to pick up signal from port. Robert McClenon (talk) 22:44, 31 October 2014 (UTC)

As for the time issue, that will vary by cell phone model. Some have their own internal clock, unaffected by location, some get a time signal from the nearest cell tower, and some give you the option to select either mode. Presumably the cruise ship won't change their own clocks as they switch time zones, so it would make sense that they would use UTC, and any cell tower they have on the ship would thus send that out as the time. StuRat (talk) 21:57, 31 October 2014 (UTC)

My cell phone picks up a time signal from a tower, which explains the switching between local time and GMT. The ship itself remained on Florida time (EDT) for purposes such as the scheduling of dinner and events, and we relied on the ship's own wake-up call service rather than using the alarm clock feature of the cell phone. Robert McClenon (talk) 22:44, 31 October 2014 (UTC)

If I wanted to know this I would go to the horses mouth. This Cruise company wants you to tell all your friends about the wonderful time you had ( providing you were sober enough to remember any of it). So email them. Say you had a wonderful time and request they pass your email onto their technical department as your geeky friends are interested in how their cruise ship maintained such good telecom. Phrase it so that the recipient instantly understands that your email needs to be answered by someone with the right technical knowledge and that you will not be fobbed off with waffle. Tech guys tend to be proud of what they have achieved and will no doubt be pleased that someone has bothered to ask.--Aspro (talk) 22:11, 31 October 2014 (UTC)

What is the reason of the putting dextrose into the 5W?

"Half-normal saline (0.45% NaCl), often with "D5" (5% dextrose), contains 77 mEq/L of Na and Cl and 50 g/L dextrose."149.78.225.240 (talk) 22:46, 31 October 2014 (UTC)

Food through a tiny tube. More on this topic: Glucose in intravenous saline and Saline (medicine) and intravenous sugar solution. Nimur (talk) 23:01, 31 October 2014 (UTC)

I think those links are too complicated. Glucose is required anyway, in order to get water into the cell. Cells contain both potassium and sodium so there is an osmotic gradient to overcome and the glucose provides the energy to the cell to over come this. 2½ % Dextrose is normally sufficient for this to happen. But say the patient already has enough salt but needs water to increase blood volume. Decrease the salt and increase the dextrose to 5%. The extra dextrose will help prevent muscle protein from be metabolized to provided energy. Increase it to 10% or more and it can feed the body in the short term.--Aspro (talk) 02:04, 1 November 2014 (UTC)

Aspro, Thank you so much for the clear explanation. Now it's clear why phiscian use it sometimes. 213.57.114.161 (talk) 03:10, 1 November 2014 (UTC)

Hello, but 5% is considered as isotonic solution. so how can you say that 2.5% is normal and 5% is more? 213.57.114.161 (talk) 06:37, 2 November 2014 (UTC)

.Fair comment, but I did not say that 2.5% is normal, I said normally surffient. 5% is considered as isotonic solution in vitro but as soon as it passes through the catheter in into to the vein the dextrose starts to get metabolized and so it behaves like a hypnotic solution in in vivo. It is not really difficult but if a patient still has one foot in this world and the other in the next. Then, whist the human body is tremendously forgiving and robust. The right re-hydration regime is critical in these cases. Then gut feeling based on experience wins out on what theory one learns in med school. Thats why I want to stay away from getting too technical because there are other things to take into consideration like obesity, malnutrition, drug use, diabetes, reasons for re-hydration (thinking, blood loss through traumatic injury as opposed to burst aneurysm in the head, burns), etc. --Aspro (talk) 17:30, 2 November 2014 (UTC)

Now, I understand. May I get a scientific source for that: "2½ % Dextrose is normally sufficient for this to happen" (I blieve you, but I need to cite a souce) 213.57.114.161 (talk) 18:53, 2 November 2014 (UTC)

Hey 213.57.114.161, I can't remember what I had for breakfast this morning, let alone remember some boring lectures that I attended 40 years ago. If you are med student, then you really need to make use of your local medical library for up to date knowledge and not resort to Wikipedia Reference desk. Back to your question. You do some work. You said “Hello, but 5% is considered as isotonic solution” This chart shows that in vivo it is considered to be hypotonic and 2½ % Dextrose at this same salt concentration is isotonic. It also list some of the clinical implications of different salines. [9]. This link give another overview. [10]. Why exactly are you asking as we don't give medical advice here? --Aspro (talk) 22:07, 2 November 2014 (UTC)

What is the purpose of the lactate in the Hartman's solution?

149.78.225.240 (talk) 23:16, 31 October 2014 (UTC)

See Hartmann's solution, though our coverage in Lactated Ringer's solution is better. Basically, when given in small amounts, lactic acid (also useful to read) i.e. CH3CHOHCOOH can be metabolized by the liver (via gluconeogenesis), I assume to 3CO2 + 3H2O with the use of three oxygens. So if you add sodium lactate (Na+CH3CHOHCOO-) and the carbon dioxide is exhaled, what is left is effectively NaOH. The result is the overall composition of the blood can be made more alkaline. This would be a good subject to improve our coverage of. The use of racemic lactate seems somewhat disquieting... not sure what to make of it. (PMID 15345971, PMID 8721391)

On Wikipedia strong ion difference is only alluded to historically in Peter A. Stewart, but the Ringer's article cites a useful free review at [11]. That review also makes fairly clear the importance of having different levels of sodium and chloride in the blood (strong ion difference) though large amounts of lactate can actually act as strong ions themselves. Wnt (talk) 11:37, 1 November 2014 (UTC)

May you explain me in a sentence why did Hartman change the Bicarbonate in lactate? (Unfortunately, I didn't understand the answer well) 213.57.114.161 (talk) 19:18, 2 November 2014 (UTC)

Chemical compounds

I have four questions about chemical compounds.

1. How many natural inorganic compounds are known to humanity?
2. How many natural organic compounds are known to humanity?
3. How many synthetic inorganic compounds are known to humanity?
4. How many synthetic organic compounds are known to humanity?

—Wavelength (talk) 23:18, 31 October 2014 (UTC)

How do you define "known to humanity"? It will be easier to find an answer to a more precise question; for example, "how many compounds are listed with published data in (one of the various) standard IUPAC data handbook(s)?" Nimur (talk) 23:39, 31 October 2014 (UTC)

In that case, what is the most comprehensive handbook and how many compounds are there for each question, as revised with your wording? (This question has eight parts.)

—Wavelength (talk) 00:40, 1 November 2014 (UTC) and 00:52, 1 November 2014 (UTC)

Secondly, what is your definition of "natural compound" vs. "synthetic compound"? Plasmic Physics (talk) 03:16, 1 November 2014 (UTC)

A "natural compound" occurs in nature, whereas a "synthetic compound" is only made by humans.

—Wavelength (talk) 04:11, 1 November 2014 (UTC)

For instance? You do realize that there is no physically defining characteristic of any particular molecule which indicates whether it conforms to either definition, they are entirely artificial demarcations? Just because we have not yet discovered it in nature, does not mean it cannot exist in nature. Plasmic Physics (talk) 04:21, 1 November 2014 (UTC)

Yes, it is difficult to rigorously and cleanly define these categories, and it certainly can't be done by physical composition alone. There is also the point that humans are themselves a natural organism, etc. That doesn't mean the category of synthetic compounds doesn't make sense at all. I don't think any Earth process made teflon or aerogel before humans did so. Likewise, many compounds are known to be synthesized by plants and animals. There are compounds found in plants that we can make from scratch in the lab, and there are also life compounds that we cannot currently synthesize at will. These are all categories that might be useful to know about. I would imagine there are ways to estimate the number of compounds known to be synthesized by humans that are not known to be produced without human agency, but I don't know enough about chemical databases to help beyond the suggestion of IUPAC mentioned above. SemanticMantis (talk) 04:53, 1 November 2014 (UTC)

I'm not saying that the category of synthetic compounds doesn't make sense in general, only so unless you precisely define its member. Teflon and aerogel are structural materials, polymers, for which the monomers may exist in nature. Then there is also the problem of inorganic vs. organic - the different schools of thought. Personally, only consider compounds with C-H or C-X-H bonds as organic. No doubt, you disagree. Plasmic Physics (talk) 05:05, 1 November 2014 (UTC)

It's even worse than that because the very definition of a "compound" is very tricky. When you consider a polymer like nylon, each molecule can have anywhere from a few hundred to a few thousand repeated sections - should we consider each of those few thousand different forms of nylon to be different compounds? They each have slightly different properties and totally different molecular weights. You also get co-polymers where two or more different groups are alternated, or inserted in some complicated pattern. Every living thing on the planet has a different DNA molecule - each of which is a "compound" - so do we count the trillions upon trillions of those as one compound called "DNA" - or give the full chemical formula and say that there is a unique chemical compound in every living thing?

Then there are chemicals like proteins that fold up into different shapes. Two proteins with the exact same chemical composition, but different folding patterns will behave totally differently. Are different foldings of the same compound counted differently?

Deciding what's man-made and what's synthetic is also difficult. Often we find a chemical in nature and make it synthetically later - other times we make a chemical in the lab, and then find some means to extract it from plants or microorganisms. Then we specially breed or genetically engineer living things to make synthetic chemicals for us. You could argue that the DNA molecule in my dog (a pedigree yellow labrador) is a "synthetic compound" because the dog breeder selected two particular animals to breed in order to make a dog with a particular form of DNA that produces certain effects that are deemed desirable. Is our puppies' DNA natural or synthetic? Some polymers exist in nature up to some particular chain length - but the man-made versions have longer or shorter chain lengths. How do we count those?

Then you ask for "known" compounds. What constitutes "known"? If we have isolated some chemical from nature, researched it's function in the animal or plant - but not bothered to deduce it's complete structure and composition - is that "known"? If we haven't bothered to analyse it - how do we know that some hormone found in this plant has the exact same composition as one with identical function found in another plant? Because no two humans (except, perhaps, identical twins) have different DNA, can we say that we know of around 7 billion human DNA "compounds" - or only that of the relatively small number of individuals who have had a complete DNA sequencing done, so we can state the chemical formula exactly?

Sadly (because it would be interesting to know), your question in unanswerable. I hope that the reasons that it's unanswerable are more interesting than the actual answer would have been! SteveBaker (talk) 13:49, 1 November 2014 (UTC)

I would love to see an estimate for number of synthetic/naturally occurring compounds, regardless of the definition or. Unfortunately I'm out of my depth here, so I hope someone else who know more chemistry can comment. SemanticMantis (talk) 19:23, 1 November 2014 (UTC)

That is just what we've been saying - that the estimate cannot decoupled from the definition. I would be like asking "How many different widgets are there?" without explaining what a 'widget' is? Plasmic Physics (talk) 22:47, 1 November 2014 (UTC)

So if I told you that the answers according to my definition of these terms is (a) 10,000,000 (b) 40,000,000 (c) 42 and (d) 3.14159 ...then you'd be happy? I'm not telling you what definition I chose for calculating those answers...but you're interested in the results anyway? That makes no sense. The answer is 42, now what is the question? SteveBaker (talk) 14:47, 3 November 2014 (UTC)

Well, a definition that is not presented is not much of a definition now is it? I suppose I should have said "any reasonable, definition, that is presented clearly along with the estimate. It looks like we can all agree that the estimate depends on the definition. This is a relatively common and normal situation. So Jayron's answer below is helpful, while attacking every attempt at an an answer is not. SemanticMantis (talk) 15:33, 3 November 2014 (UTC)

• One marginal attempt at answering the question. The Merck Index has somewhat over 10,000 compounds listed. But that's a tiny subset. The Chemical Abstracts Service attempts to catalogue every unique substance in published, scientific literature. It gives each such substance a CAS Registry Number. According to our article, the CAS assigns about 15,000 RNs every day; it has about 81 million organic and inorganic compounds in its database, and 64 million protein and DNA sequences. So, there's at least some number of the scale we're talking about. There's no way to prove conclusively that the CAS's registry contains every single compound ever discovered, but it does at least try to do so. I hope this helps refocus the answer to the OP's question. --Jayron32 00:53, 2 November 2014 (UTC)

It's pretty easy to prove conclusively that CAS doesn't contain every single compound ever discovered, given the numerous dead-end routes often followed during research, with however-many novel intermediates and products that ultimately do not get published because they aren't what was intended and don't make an interesting enough story to publish (or pursue themselves to become so). DMacks (talk) 03:49, 2 November 2014 (UTC)

So what do those indices do about polymers with different chain lengths and molecules like DNA where we use one name to describe a billion trillion different molecules with similar structure but different composition? (I'm genuinely interested in the answer!) SteveBaker (talk) 14:49, 3 November 2014 (UTC)

Natural inorganic compounds have a better chance of having a count. Look at List of minerals (complete) which gives several counts numbering in the few thousands. List of interstellar and circumstellar molecules has molecules not found on the earth and which number a bit over 100. This misses out on molecules found in stars, and those found in atmospheres or oceans though as they are not solid and so are not minerals. Graeme Bartlett (talk) 22:26, 4 November 2014 (UTC)