Wikipedia:Reference desk/Archives/Science/2013 May 13

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May 13

Other than dogs, what animals mainly perspirate by drooling?

--朝鲜的轮子 (talk) 01:56, 13 May 2013 (UTC)

Dogs don't really perspire by "drooling", they use panting to get rid of excess heat, the drool helps with the efficiency of the panting. Panting is also used for thermoregulation by pigs, cats and many birds. Vespine (talk) 02:56, 13 May 2013 (UTC)

I thought there's a theory about human's running. It says humans are "born to run long distances". People sweat and it helps you get rid of excess heat "in the long run". On the other hand, many other animals are only capable of sprinting. -- Toytoy (talk) 03:15, 13 May 2013 (UTC)

There's something to be said for that; famously in the Man versus Horse Marathon sometimes the man wins. That is, while horses are better, on average, at running a marathon-like distance, it isn't such an overwhelming advantage that some people can't outrace some horses over long distances. Quite notably, as the article Perspiration notes, while many mammals sweat, humans and horses are among the few that do so as an efficient means of thermoregulation; and notably horses are somewhat better long distance runners than humans. --Jayron32 03:31, 13 May 2013 (UTC)

Competitors in the 2006 Man versus Horse Marathon

This is unfair!

That poor horse has a man on his back.

To be fair, the man in front must carry a horse on his back! -- Toytoy (talk) 04:07, 13 May 2013 (UTC)

He already has a horse at his back... :-) Double sharp (talk) 13:41, 13 May 2013 (UTC)

22 miles is rather too short for an advantage for a man against a horse, it should really be over something like twice that distance and wild horses have been caught on foot just by running after them, it can be dangerous for the horse though. However for smaller animals like kudu persistence hunting is used by bushmen in a distance like 20 miles to tire down and kill prey, see [[1]]. Dmcq (talk) 09:18, 13 May 2013 (UTC)

(Speaking of horses...) I know very little about horse perspiration (that's not an article!), but I have rather distinct memories of horses I've been acquainted with being exceptionally drool-y (and that's not a word!) on hot summer days. My best guess at the time was that it was something like dogs' version of thermoregulation, minus the panting. I haven't been able to come up with a better explanation yet. Evanh2008 ^{(talk|contribs)} 06:06, 13 May 2013 (UTC)

Don't horses show froth or foam on their flanks when they've been ridden hard? I know hardly anything about horses, but remember reading it in different places. Alansplodge (talk) 17:24, 13 May 2013 (UTC)

Now that you mention it, that does sound like something I've heard in the past. The odd thing about this is that my most vivid memory of it involves an entire pasture of horses. They all would have been ridden fairly regularly, but I'm certain not all of them had been ridden that day or even that week. Evanh2008 ^{(talk|contribs)} 17:32, 13 May 2013 (UTC)

Frothing on the body depends on the action of friction on the sweat. See discussion. μηδείς (talk) 20:49, 13 May 2013 (UTC)

This was definitely originating from the mouth, rather than the body. Evanh2008 ^{(talk|contribs)} 00:35, 14 May 2013 (UTC)

Is it true that dogs have very few sweat glands except on their heads?--朝鲜的轮子 (talk) 02:57, 14 May 2013 (UTC)

Mammals like cats, dogs and pigs, rely on panting or other means for thermal regulation and have sweat glands only in foot pads and snout. Evanh2008 ^{(talk|contribs)} 03:09, 14 May 2013 (UTC)

Clam meat

Clams are usually sold by weight. Let's say all clams are sold at the same price by weight, and there are large, medium and small clams for sale. What kind of clam would you buy in order to get the maximum amount of edible clam meat? -- Toytoy (talk) 03:11, 13 May 2013 (UTC)

Depends on what you want to use them for. The larger the clam, the tougher the meat. Small clams are good raw or steamed on the half-shell. Larger clams should be used in chowder. What you want to do with them should be of greater concern for you than simply the total amount of meat. Think of it this way: filet mignon costs different than brisket, but you don't use them for the same thing. I'd never make pastrami out of filet mignon, and brisket is far too tough for making grilling steaks out of. Same with the clams. Regardless of which gets you the best "bargain", it isn't a bargain if the quality is not what you want. --Jayron32 03:14, 13 May 2013 (UTC)

To answer the question, I'd go for the larger clams to get most edible meat per weight. Here's my reasoning and assumptions: the shell thickness doesn't vary much, but total weight does. That is, a 4 oz clam may have a thicker shell than a 2 oz clam, but probably not twice as thick. The larger clams should have relatively less of their weight taken up by shell, compared to smaller clams. This is also assuming that we are talking about different size classes of the same species. Note that clam can mean many different species in USA English. SemanticMantis (talk) 14:22, 13 May 2013 (UTC)

A Boy and His Atom

This video is a stop-motion film made by IBM engineers using carbon monoxide molecules (the video describes them as "atoms," which I guess they technically are). Around the molecules, you can see something like a double image, almost a blurry, ripple-like duplicate of the molecules, only it may be many times double. Given the spacing of the atoms and the number of duplicates, it's hard to tell the exact number. My theory so far is that this is an optic effect (for lack of a better term), likely caused by mechanical oscillations in the microscope itself, as the imaging device vibrates, causing something like you may see when someone with an unsteady hand snaps a picture with a digital camera. What I can't figure out is why the molecules themselves aren't distorted in the picture (as you would see with a typical double exposure). But if that is the explanation, I can't figure out why you wouldn't see an identical effect with other pictures of small objects taken with electron microscopes. Any thoughts? Evanh2008 ^{(talk|contribs)} 05:59, 13 May 2013 (UTC)

This question is specifically answered in text and in video form at IBM's website: Made With Atoms. Nimur (talk) 06:18, 13 May 2013 (UTC)

And that's how the ref desk is supposed to work! Thanks, Nimur! :) Evanh2008 ^{(talk|contribs)} 06:23, 13 May 2013 (UTC)

Peroxodisulphate

calculate the volume of 0.01M peroxodisulphate ions required to oxidize 25cm³ of iron(Π) ions to ironΙΙΙ ions.iron(ΙΙ) ions were obtained by dissolving 1.12g of iron in dilute sulphuric acid — Preceding unsigned comment added by Nabwire (talk • contribs) 12:32, 13 May 2013 (UTC)

Please do your own homework.

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Red Act (talk) 13:32, 13 May 2013 (UTC)

Zero point energy and the volume of the universe.

Why doesn't the zero-point energy density of the vacuum change with changes in the volume of the universe? And related to that, why doesn't the large constant zero-point energy density of the vacuum cause a large cosmological constant? Is it allowed to postulate / hypothesize on this topic on the reference desk, or is there a separate science forum / talk page for that? Robert van der Hoff (talk) 06:49, 7 May 2013 (UTC)

Robert, the idea is that a header is a **short** (up to about 7 words) pointer to what the question is about, the meat of which then appears below the header. -- Jack of Oz [Talk] 07:32, 7 May 2013 (UTC)

(I made a more concise title and transferred the L-O-N-G title into the message body). SteveBaker (talk) 12:59, 7 May 2013 (UTC)

• We don't encourage using the reference desk simply to initiate discussion - especially when it's to discuss some idea that you had. However, there is a reasonable question here that we can possibly answer. SteveBaker (talk) 13:01, 7 May 2013 (UTC)

You hit the nail right on the head. That is indeed a very deep mystery that is yet to be satisfactorily answer by modern physics. Naive calculations show that the cosmologic is about 120 orders of magnitude off (If memory serves). Supersymmetry improves that to "only" 60 orders of magnitude. Dauto (talk) 22:28, 7 May 2013 (UTC)

And did you read the Zero-point energy article? where energy per particle is ½hν, not necessarily a very high density by cosmological standards. And this article also mentions renormalization to deal with the possibility of the lowest energy level of fields also containing energy. Graeme Bartlett (talk) 08:05, 8 May 2013 (UTC)

It's not ½hν per particle. It's ½hν per vibration mode of each bosonic field which strictly speaking is infinite hence the need for renormalization. Dauto (talk) 17:18, 8 May 2013 (UTC)

I read the article, and also the one about quantum foam, and the relevant sections from the book 'the fabric of the cosmos'. What I don't understand is how it relates to the universe we know. What are the properties or conditions of the quantum foam that triggered the Big Bang?Robert van der Hoff (talk) 13:38, 13 May 2013 (UTC)

Isn't this question listed in List of unsolved problems in physics? RJFJR (talk) 16:15, 13 May 2013 (UTC)

Correct, but there seems to be little movement in trying to solve it. I still hope that somebody will try to answer my question.Robert van der Hoff (talk) 11:29, 14 May 2013 (UTC) It's radio silence out there, so I'll just talk to myself. I postulate that the quantum foam is the real universe, infinite and eternal, and that our Big Bang was just a local outburst triggered by something that happened within the quantum foam. I wonder if that notion could put to rest the paradox of the large cosmological constant?Robert van der Hoff (talk) 07:15, 16 May 2013 (UTC)

Carbohydrate jacket potato overdose?

I was told earlier (during lunch funny enough) that it's possible to overdose on jacket potato...I'm aware you can overdose on vitamins, but there aren't any high vitamin values in jacket potatoes are there? The only decent Google references to this i could find point to someone named "Harvey" managing to "carb overdose" on 3 jacket potatoes. So really my question is how safe would it be to eat a jacket potato on a daily basis? Thanks ツ Jenova20 ^(email) 14:53, 13 May 2013 (UTC)

Think this is a miss use of semantics. Overdose usually in the vernacular means: taking too much of a drug. [2] Too much carbohydrate (at the expense of protein) will only leave you with stunted growth and that is a dietary thing. One just requires a balanced diet. If you do wrestling, then you could have a huge intake of calories and still be healthy. Sumo's eat amassing quantities of rice but burn it of in training.--Aspro (talk) 15:20, 13 May 2013 (UTC)

That's jacket potato, in case anyone else is unfamiliar with the term. Otherwise I agree with Aspro, this is a very informal usage (or just incorrect, e.g. overdose). Compare to "He overdosed on Breaking Bad, watching 50 episodes in two days!" SemanticMantis (talk) 15:36, 13 May 2013 (UTC)

I'm already stumped on this one... ツ Jenova20 ^(email) 15:45, 13 May 2013 (UTC)

A diet of whole milk and potatoes would supply almost all of the food elements necessary for the maintenance of the human body. Count Iblis (talk) 15:52, 13 May 2013 (UTC)

That's certainly interesting. So there's no issues of any overdose, like with a potassium overdose from eating hundreds of bananas? Thanks ツ Jenova20 ^(email) 16:02, 13 May 2013 (UTC)

. An organization whose sole raison d'être is to sell more potatoes is not where I would go for information on whether I should eat more potatoes. --Jayron32 16:17, 13 May 2013 (UTC)

I eat about 1 kg of potatoes a day, I doubt most people could eat this much. While 1 kg of potatoes contains a lot of nutrients, I still need to eat a lot of vegetables, fruits etc. to get all the nutrients I need. So, overdosing on potatoes isn't really feasible as our stomachs are too small. Perhaps big animals that eat foods low in nutrients like e.g. cows or elephants could overdose on potatoes. Count Iblis (talk) 16:31, 13 May 2013 (UTC)

• See hyperglycemia, diabetes, ketoacidosis, and death. μηδείς (talk) 17:48, 13 May 2013 (UTC)

Diabetes? Is there really much sugar in potato? I know it's starchy but i'm not really really technical with this stuff. Thanks ツ Jenova20 ^(email) 19:48, 13 May 2013 (UTC)

Starch is sugar, essentially. All carbohydrates are simply chains of sugar molecules of varying length, from one (Glucose and fructose) to two (sucrose and maltose) to shortish chains starch to long, complicatedly branching chains (cellulose and dietary fiber). The key is Glycemic index which tells how fast the digestion of various carbohydrates releases glucose into the blood stream. Foods with low glycemic index slowly release glucose, so you don't get high glucose concentrations, which is good, diabetically speaking. Foods which are high in glycemic index cause large spikes in blood glucose levels, which is bad diabetically speaking. Baked russet potatoes are among the worst foods in terms of glycemic index: 111, per this table published by Harvard Medical School, which makes it worse than pure glucose. Even boiled or mashed potatoes are pretty high, ranking in the 80s. It's hard to do worse, in terms of picking foods which are bad for blood glucose, than potatoes. --Jayron32 20:47, 13 May 2013 (UTC)

Starch is actually a chain of pure sugar with some water extracted. It converts entirely to sugar, starting even in the mouth with the action of pepsin in the saliva. μηδείς (talk) 20:45, 13 May 2013 (UTC)

Would it be possible to get an excessive amount of solanine or related compounds from eating potato skins? RJFJR (talk) 21:00, 13 May 2013 (UTC)

This article says that most commercial varieties of potato have between 2-13 mg/100 g of solanine in them. The TDLo for humans is 2.8 mg/kg: www.look chem.com/SOLANINE/. So, an 80 kg person would have to eat 224 mg of solanine to be toxic, that would mean eating 1.72 kg of potatoes, assuming the 13 mg/100 g at the high end of solanine concentration. The average Russet potato (one of the larger varieties) is 299 g: www.food facts.com/NutritionFacts/Fruits-Nuts-Seeds-Vegetables/Potatoes-Russet-Raw--Large-Potato-w-Skin-/21020. That would mean you'd need to eat 5.75 whole russet potatoes in a sitting to get toxic effects from solanine, assuming the worst case scenario. Unlikely, but not impossible. (refs hit spam filter. Take out spaces to get them) --Jayron32 21:16, 13 May 2013 (UTC)

You might try our article on solanine, just not the green potatoes. μηδείς (talk) 22:03, 13 May 2013 (UTC)

All potatoes contain some solanine, the data above is for average, standard store-bought potatoes of good eating quality. Green potatoes would, of course, contain even more solanine that what is noted above. --Jayron32 22:09, 13 May 2013 (UTC)

Hmmm, I'm not far below this limit with my 59 kg bodyweight and 1 kg of potatoes per day. Count Iblis (talk) 22:42, 13 May 2013 (UTC)

Some naturopaths claim that potatoes aggravate arthritis - a disease of elderly people. I've never believed it myself, as I am elderly, arthritis free, and eat a lot of potatoes, which contain vitamin C, but how old is Count Iblis? Wickwack 121.221.30.176 (talk) 01:55, 14 May 2013 (UTC)

One issue to bear in mind is that something like half of the solanine is in the outer few millimeters of the surface of the potato. So if you were to preferentially eat potato skins (and I've seen those served as appetizers in several US restaurant chains), you could easily go over the safe dose level. Fortunately, most people who serve them deep-fry them and that gets rid of most of the solanine. However, pan-frying or microwaving doesn't get rid of it...so beware! However, a corollary to that is that if you eat baked potatoes and leave the skin behind - or if you peel your potatoes, then the risk is greatly reduced. SteveBaker (talk) 16:59, 16 May 2013 (UTC)

Hot Jupiters

With Hot Jupiters, how is their mass, density, and composition determined? Bubba73 ^{You talkin' to me?} 16:25, 13 May 2013 (UTC)

AFAIK, you need planets that you can detect both via the Doppler method and the Transit method. In that case, you know that the orbital plane of the planet is (very nearly) aligned with a line from the star to the observer, and hence that all of the radial velocity difference visible in the doppler shift. Then you have the ratio of masses and the orbital period, and you can solve for mass. The transit observation shows you how much of the star is covered by the planet during transit, and hence the diameter of the planet. From that you get the volumen, and with the mass (and math ;-) the density. I don't think you can completely determine the composition, but the density gives you a good initial guess, and in the best cases, you can get spectroscopic data from the atmosphere during transits. --Stephan Schulz (talk) 16:38, 13 May 2013 (UTC)

OK, I see how you get the size, but how do you get the mass? Bubba73 ^{You talkin' to me?} 16:46, 13 May 2013 (UTC)

From the radial velocity changes, you get the relative ratio of the masses (the heavier the planet, the more it pulls the star around). You also know the orbital period (from the timing of transitions or doppler shifts). That gives you two equations for two variables. --Stephan Schulz (talk) 16:50, 13 May 2013 (UTC)

OK, the ratio of the mass of the planet and the star.

Resolved

Bubba73 ^{You talkin' to me?} 17:04, 13 May 2013 (UTC)

galactic plane all the same?

How closely aligned to our solar system's are the orbital planes of other planetary systems on average? μηδείς (talk) 17:45, 13 May 2013 (UTC)

They are not aligned at all. Ruslik_Zero 19:14, 13 May 2013 (UTC)

Ugh? You didn't give any references, so that's really no answer at all. [3] suggests that all stars, planets and star polars start up the same way. But the op is asking for an average or better description, like a bell curve as it applies to OUR solar system in OUR galaxy to other planetary systems in OUR galaxy --Aspro (talk) 19:44, 13 May 2013 (UTC)

I'm sorry, but I cannot find anything about the orbital planes of planetary systems in the linked article (that may be my failure). As far as I can tell, it only talks about the orbits of stars in the galactic plane. --Stephan Schulz (talk) 21:11, 13 May 2013 (UTC)

She didn't specify it was confined to our galaxy. -- Jack of Oz ^[Talk] 20:19, 13 May 2013 (UTC)

Quote the OP : "How closely aligned to our solar system's are the orbital planes of other planetary systems on average?"

What is there in that to suggest other galactical bodies other than our own? Use a modicum of commons sense.--Aspro (talk) 20:33, 13 May 2013 (UTC)

What is there in that to suggest other galaxies are excluded? Keep your remarks civil, please. -- Jack of Oz ^[Talk] 20:41, 13 May 2013 (UTC)

I didn't think it was necessary to mention the galactic plane twice, I usually assume common sense on behalf of the regulars here. Also, how many planetary systems in other galaxies do we have information on? Also, is it not obvious other galaxies all spin at random angles to ours? I am basically curious if there's any information; average, anecdotal, from a study, theoretical, whatever; that suggests there's a better than chance alignment of planetary planes in the galaxy. μηδείς (talk) 20:42, 13 May 2013 (UTC)

At least Kepler data is interpreted with the assumption that orbital planes of other stars are randomly aligned. Kepler is also looking "up", so this assumption has also been build into the mission (if planetary orbits were aligned with ours, Kepler would miss them all). --Stephan Schulz (talk) 21:19, 13 May 2013 (UTC)

Well, that article shows a field that looks pretty close to the galactic plane near Cygnus, so it's a matter of degree - it's certainly not pointed straight out to deep space. Wnt (talk) 16:57, 14 May 2013 (UTC)

Damned reference system confusion! I was talking about "up" from a solar system perspective, where "up" from the ecliptic is the side where Earth North Pole is, not "up" in a galactic reference system. --Stephan Schulz (talk) 19:27, 14 May 2013 (UTC)

Transits of planets close to stars in our galaxy are barely detectable. Yet, if you are insatiable (and I can think of better terms) you can search for them here. [[4]] For other planets in other galaxies far, far, aware -forget it -the orders of magnitudes are not yet within our realms detectability – Jesus (etc.,) -we can’t see planets on the other side of our own universes let alone other galaxies. Quote: ”Also, is it not obvious other galaxies all spin at random angles to ours?” Have you hear off “big bang" and space telescopes show everything flowing – blooming off from the centre?” Ballooning other analogies? Hubble & other images show it. Perhaps not obvious (to you) but it is very evident evident. Its not planetary planes but galactic planes. Quote: “other galaxies all spin at random angles to ours” they did not! Computer modelling has shown that the universe ended up in its present state according to to the physics that we now understand.Aspro (talk) 22:28, 13 May 2013 (UTC)

Your comment is very confusing, Aspro, and you seem to be conflating the words galaxy and universe, perhaps because galaxies used to be called island universes. In any case, I am talking about objects like the Milky Way and Andromeda when I speak of galaxies in general. It is quite obvious from both catalog and deep field images that their spin is random in relation to the spin of our galaxy. In any case, my question is only about the various planetary systems in our galaxy alone. μηδείς (talk) 23:56, 13 May 2013 (UTC)

Sorry, but nothing is "flying off from the centre", unless (maybe) you think in more than the customary dimensions. The metric expansion of space has no center. And the Hubble Deep Field and Galaxy Zoo do not seem to find much bias in galaxy orientation in the universe at large. I'm also confused by your plural use of "universes", and the idea of "the other side" of our universe(s). But yes, as far as I know, we have not yet detected any planets in another galaxy. We can resolve individual stars in nearby galaxies, so in principle it could be possible to use the transit method. --Stephan Schulz (talk) 22:54, 13 May 2013 (UTC)

When I was a child, the classroom dictionary said that "the universe" and "the milky way galaxy" were synonyms. Since that dictionary was printed, astronomers determined that there were other galaxies in the "universe." Edison (talk) 02:01, 14 May 2013 (UTC)

Are you the Edison and have invented a longevity machine, or was your school using really outdated books? The topic was settled late, but it was settled by 1930 or so. --Stephan Schulz (talk) 06:30, 14 May 2013 (UTC)

I was a child a long time ago, the classroom dictionary was an old one, and dictionary writers apparently took a surprisingly long time to stop saying that the Milky way galaxy equalled "the universe." Edison (talk) 16:05, 14 May 2013 (UTC)

Extragalactic planets. Dragons flight (talk) 23:23, 13 May 2013 (UTC)

And specifically: An extra-galactic planet has been detected in Andromeda, lovingly named OGLE-2005-BLG-390Lb. They used gravitational microlensing techniques to find it. SteveBaker (talk) 19:58, 14 May 2013 (UTC)

That page says it's ~20,000 ly away and in the Scorpius constellation, while Andromeda is 2.5 million ly away and in the Andromeda constellation. --Sean 20:58, 14 May 2013 (UTC)

Ack! Sorry - I was thinking of this: http://www.newscientist.com/article/dn17287-first-extragalactic-exoplanet-may-have-been-found.html - but that seems more tentative than I believed it to be. SteveBaker (talk) 20:05, 15 May 2013 (UTC)

It seems doubtful that any planets could be detected by wobble or by transit, the only means of analysis currently available, if they were not in our own galaxy. So the question must apply to planets in the Milky Way galaxy. The transit method only reveals a planet if its orientation is has an axis such that it passes between us and its star. I'm not so sure about the wobble method. Edison (talk) 01:54, 14 May 2013 (UTC)

I actually studied at Cornell as an undergrad because I was a huge fan of Carl Sagan, although I never did meet him. So I can speculate on my own. The extragalactic article mentions an unrepeatable observation, an unconfirmed one, and a rogue planet of assumed extraterrestrial origin, but no information on intragalactic (or intergalactic) systems. I can draw surmises from the Kepler article, but they are surmises. I do believe we have some professional or at least credentialed astronomers here, so I hope there will be more comment. μηδείς (talk) 03:57, 14 May 2013 (UTC)

I want to have new discussion about this , has solar system sidereal rotation?--Akbarmohammadzade (talk) 05:47, 14 May 2013 (UTC)

See your question "Has solar system sidereal rotation?" below. Wickwack 60.230.230.117 (talk) 06:38, 14 May 2013 (UTC)

In the astrophysics literature, it is standard to assume that the orbital planes of other stars are completely random. Every statistic you see in the news relating to exoplanet frequencies (i.e. "there are 2 billion Earth-like planets in the habitable zones of Sun-like stars in the Milky Way") is going to have that assumption built in. That's how we calculate the geometric transit probability of detected planets, and from there, work backwards to deduce how many of that type of planet there must be.

As of now, there's no way to test the assumption of random orientation. If a planet transits its star, we can deduce its inclination with respect to the plane of the sky, but this will always be close to 90 degrees (or else the planet wouldn't transit). To determine its 3D orientation, one more angle is required, and that's the direction of the orbital axis in the sky plane. There's no way to measure this angle because for almost every star, the star itself is a point of light, the planet is invisible, and the star does not move enough due to the planet to be detectable by astrometry.

That said, it would be quite surprising if orbital planes weren't randomly oriented. The molecular gas clouds that stellar systems originate from are expected to have tiny rotation rates determined by chance and internal dynamics, not the galaxy (see [5]). When they collapse, whatever direction the cloud's net angular momentum happens to be pointing in defines the stellar system's orbital plane. Also, we have evidence that the orbital planes of binary stars are randomly oriented, and the formation process of binary stars is roughly analogous to that of planets: [6]. --Bowlhover (talk) 08:13, 14 May 2013 (UTC)

The plane of rotation is defined by the net angular momentum. Physicists believe, rather religiously, actually, that conservation of angular momentum is one of the most fundamental properties of the universe - and is never violated. If many different objects - planetary or stellar systems - have the same plane of rotation, then they have aligned angular momentum - which doesn't cancel out if you look at the ensemble. The whole group therefore has angular momentum, and always had angular momentum. Consider two possible consequences of that hypothetical observation, spanning all cases:

• This is a local observation. Suppose we broaden our search and find that more distant systems do not align with the local systems. Elsewhere in the universe, if we looked on a bigger scale, the angular momentum is oriented differently, and does cancel out. Therefore, the universe is strongly inhomogeneous at very large length scales. Some parts "birthed" into existence carrying different values of built-in momentum.
• This is a global observation. Suppose we hypothetically observe very far into the universe; and everywhere we look, in the entire universe, all the planes of rotation line up. The universe has therefore a net angular momentum; this defines an axis of rotation: and therefore, the universe has a preferred direction. The universe is strongly anisotropic at very large length scales. The universe "birthed" into existence already spinning along a particular axis.

Now, as observationalist physicists, we can't seriously conclude either case to be true, but we can quantitatively bound how probable these cases can be, based on our observations of apparently random orientations of stellar systems. We can say that for case one, if such inhomogeneity exists, it must occur on length scales larger than L... where L can be specified based on our observation. Or, we can say that for case two, if such anisotropy exists, its net "strength" must be weaker than S based on our counterobservations at small length scales.

I have frequently stated that the only actual questions left in cosmology boil down to these two: how anisotropic is the universe? How inhomogeneous is the universe? And we can say to both, "less than some maximum, and more than some minimum, based on what we observe..." Either way, we can't make a very strong claim, and our bounds are so very broad as to be almost useless. This is because our observations are very sparse, and are limited by our technological capability to study distant stellar systems from here at Earth. But, we've quantitfied the limits of our knowledge!

Finally we're thinking and talking like real actual cosmologists, rather than pop-pulp-science-fiction-writers! Nimur (talk) 14:22, 14 May 2013 (UTC)

I have no idea what you're trying to say. The OP asked about planetary systems in the Milky Way. You're talking about cosmology. Cosmological effects are utterly negligible on the scale of a galaxy, especially because the expansion of space does not affect gravitationally bound objects like galaxies. The answer to the OP is still "orbital planes are randomly oriented". --Bowlhover (talk) 16:44, 14 May 2013 (UTC)

Sorry if my post was unclear. I was attempting to describe why, from first principles of physics, we expect random alignment of the orbital planes, irrespective of the various length-scales we choose for our observational sample. If you still find my explanations unclear, you might consider reading my favorite resource on the topic, de Pater and Lissauer, Planetary Science, which spends most of chapter 13 discussing formation and evolution of stellar discs and describes their constraints by applying physical principles to inferred cosmological initial conditions. Perhaps my regurgitation of these concepts was a little more disordered than a textbook explanation. Nimur (talk) 18:02, 14 May 2013 (UTC)

Apparently Nimur's given a theoretical argument against, while these images show that our ecliptic is not aligned to the galactic plane. It appears the answer is that there is no evidence in favor of the hypothesis that planetary systems within our galaxy are aligned. I suspect that makes sense for any system that evolved from a nebula that was not coeval with the original condensation of the galaxy, given the alignments of nova ejecta would not be expected to align with the galactic plane. Does that sound correct? μηδείς (talk) 02:09, 15 May 2013 (UTC)

I seemed to have confused μηδείς with my last post. Said, Quote “our own universe” not “the universe”. Galaxies (as far as we know, start of as a flat plain (think of a pitza). Over time gravity (including dark matter so I'm reliably informed) pulls it together and it thickens out. [7]. Now think of spinning a bicycle wheel axil on your hand. Hold it tight. Move it up down, rotate it left to right. If one holds it firmly (as gravity will do) then it does not keep pointing in the same direction (as a free floating gyro would do ) but the axis of rotation goes off somewhere else. So, therefore, and thus, etc., etcetera; our own Sun's planetary plane is not exactly on our own galactic plain. Because we (you, me, Martha Stewart et. al) are no longer on out galaxy's 'exact galactic plain. So, do other star systems in 'our' and other galaxies when the star bunch up. But now I'm forgetting what useful point of μηδείς question is about. Back to you μηδείς: For what useful purpose do you need to know this percentage?Aspro (talk) 22:50, 15 May 2013 (UTC)

Determination of titratable acidity in apple juice

Hi! So this is our project (sort of) for an analytical chemistry lab. And If get the idea, since the commercial apple juice (which is what we're gonna use) is more or less colorless we can use an indicator (I'm unsure of whether they'll give us pH-meters and I'm not gonna risk) and apparently Malic acid is the dominant acid in apple juice (the natural one at least) and I've read in sources here and there that at least for the apple juice the pH of equivalence point is about 8, which helps me choose an indicator. The problem, however, is that I need a reliable source on the internet which I can use to cite, and Google searching it didn't give me any method which cites reliable sources. so where can I find a source for that? (sorry for potential grammatical/spelling errors)--Irrational number (talk) 18:47, 13 May 2013 (UTC)

The equivalence point will depend on which base you are titrating with, but if you are using a strong base like NaOH, then you need to calculate the pH of sodium malate, which will be the only species present at the equivalence point. There's a description of how to do so here, it's not hard if you know how to do pH calculations in general. Since you're calculating the pH of a solution of a weak base (sodium malate), you need it's Kb=10^-14/Ka of malic acid (obtained from the malic acid article). If you have an estimate of the concentration of the sodium malate (based on what you expect the concentration of malic acid is in apple juice) you can make a decent guestimation of what pH the equivalence point will be. --Jayron32 21:00, 13 May 2013 (UTC)

Thank you, but I was actually looking for a source I could cite for writing my lab report. It's so important for them.--Irrational number (talk) 09:46, 14 May 2013 (UTC)

The source you cite is any source for the Ka of malic acid, as it is the only number you need to look up, rather than calculate. All of the rest of the numbers either come from the lab procedure your teacher gave you, or you calculate them. The Ka values are given in the Wikipedia article, but if your teacher doesn't want you to cite Wikipedia, the values have a footnote so you can follow that to a non-Wikipedia reliable source. --Jayron32 12:39, 14 May 2013 (UTC)

Yeah, but I need a source for the procedure, not the values that I need. The teacher didn't give us any procedure, she asked us to find one for determining the titratable acidity of apple juice. I can think of a procedure (calculating the pH value of the equivalence point by estimating the concentration (and choosing the best indicator for it), making NaOH, standardizing it, using it to titrate the sample in presence the proper indicator), but I don't have any source that says this is the right procedure. I know science must not be based so much on authority and all that, but that's what they want from us... Sorry if I'm annoying...--Irrational number (talk) 13:06, 14 May 2013 (UTC)

The source of the procedure would be the source for any titration of a weak, diprotic acid with a strong base, which isn't functionally different than any titration. Literally every single general chemistry lab manual for first year chemistry students at both high school and college level has a titration lab like this. The procedure itself doesn't have to be modified from any titration, except that malic acid is a diprotic acid, so has two equivalence points. --Jayron32 21:07, 14 May 2013 (UTC)