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February 17

Cabbage, salt and water... blue?

Hi all,

I'm making pickled cabbage. I shredded a bunch of red and savoy cabbage, sprinkled a few tablespoons of salt on it, and left it for 24 hours. Then I removed the cabbage. At the bottom of the bowl, there was a puddle of red liquid. I then brought the bowl to the sink and started pouring some water in it. To my surprise, the water turned bright blue!

Can anyone explain the chemical reaction that must have occurred?

Thanks! — Sam 76.24.222.22 (talk) 01:40, 17 February 2010 (UTC)

Red cabbage is a traditional pH indicator. [1] Dragons flight (talk) 01:43, 17 February 2010 (UTC)

The salt might have extracted the acidic component without extracting a basic component, maybe? John Riemann Soong (talk) 01:51, 17 February 2010 (UTC)

Very interesting. Any thoughts as to why it only appeared when I added water? (I was able to replicate this later.) I doubt my water is that basic! — Sam 76.24.222.22 (talk) 03:55, 17 February 2010 (UTC)

According to the "How to Make Red Cabbage pH Indicator" link on the Red Cabbage page, at pH 6 the solution is violet, and is blue at pH 8. I imagine at pH 7 it would be classified as "blue". Most tap water is around pH 7 (indeed, if it falls much outside that range, your water company will adjust the pH to avoid damage to the pipes and to keep the sanitizing power of the added chlorine). Now, why does the water *change* the pH? Most tap water isn't just H₂O, it also contains a number of buffering agents, especially if it comes from something like a limestone aquifer. The buffering capacity of the water probably overwhelmed the small amount of acid in the cabbage drippings, bringing the pH back to ~7 and turning the color blue. It's not that the tap water was very basic, it's just that it was less acidic than the juice. -- 174.21.247.23 (talk) 04:10, 17 February 2010 (UTC)

Orientation of the International Space Station

I've been watching live video of the STS-130 mission to the ISS online on NASA TV. At times (when they are not receiving video from the ISS) they display a graphic showing the ISS, from three views, as it orbits. From the relative motion of the Earth displayed below and what I assume are velocity and acceleration vectors displayed on the side view, it appears as if they are representing ISS orbiting with the Russian section leading and the shuttle, docked to PMA-2 (attached to Note 2, Harmony), trailing. This is the opposite orientation as described at International Space Station#Attitude (orientation) control. Exterior ISS video I saw yesterday of the PMA-3 attachment to Note 3 seemed to agree with the WP description. So, is the NASA graphic backwards, or do they occasionally reverse the orientation of the ISS, perhaps to help protect EVA crew from MMOD? 58.147.58.28 (talk) 01:53, 17 February 2010 (UTC)

It is hit and miss whether the orbital orientation graphic is displayed on NASA TV at any one time. I will try to find it in another source, but I don't know how easy that will be as it is not the sort of thing that typically makes it into the daily highlights videos. 58.147.58.28 (talk) 02:03, 17 February 2010 (UTC)

I haven't found another source for the graphic, but exterior ISS video of the EVA in progress showing Note 3, PMA-3, and cupola with the Earth seen moving below seems match the reversed orientation of the graphic. 58.147.58.28 (talk) 03:41, 17 February 2010 (UTC)

While the Shuttle is docked to ISS, the ISS attitude is yawed 180 degrees from normal such that the Russian Segment is in front and the Shuttle trailing, exactly as you describe. This is done to protect the Shuttle Thermal Protection System from micrometeroids and orbital debris. anonymous6494 08:49, 17 February 2010 (UTC)

Thanks. With the answer in hand I was able to search and find this reference which deals specifically with STS-130. I'd like to find one that mentions the practice in general, but I suppose that this one would be sufficient to expand International Space Station#Attitude (orientation) control. 58.147.58.28 (talk) 01:08, 18 February 2010 (UTC)

And I see that the orientation is back to normal as the shuttle undocks. (I missed the change which I assumed was done by the shuttle's RCS shortly before undocking). 58.147.58.28 (talk) 01:17, 20 February 2010 (UTC)

Correct! anonymous6494 05:07, 20 February 2010 (UTC)

Linear density

I computed the linear dord of quartz for a question earlier using wolfram alpha as ${\sqrt[{3}]{density}}$. The units for the result are ${{\sqrt[{3}]{g}} \over cm}$. I understand why it gave that result, but it doesn't make sense. Shouldn't it simply be $g \over cm$? What did I do wrong? Ariel. (talk) 02:45, 17 February 2010 (UTC)

The cube root of density is the cube root of (g/cm) not the (cube root of grams)/cm. Plus "dord" isn't a real word - as you'd know if you'd followed the link you kindly left us! SteveBaker (talk) 03:02, 17 February 2010 (UTC)

I know dord isn't a real word. It was a joke. You and Jayron below you said exactly the opposite things about the units. Ariel. (talk) 03:14, 17 February 2010 (UTC)

(edit conflict)Density is grams per cubic centimeter, or g/cm³. Taking the cube root of that returns g^1/3/cm or as you note above, the cube root of grams over centimeters. --Jayron32 03:05, 17 February 2010 (UTC)

If you take the cube root of g/cm³ you get g^1/3/cm, and yet linear density is g/cm - so what gives? Ariel. (talk) 03:14, 17 February 2010 (UTC)

That's because linear density is defined as mass per length, NOT as the cube root of density. So, you are starting from the wrong premise. Linear density is NOT the cube root of density; its just grams per centimeter. Wouldn't it be nice if there were some sort of free information resource on the web where you could look this stuff up? --Jayron32 03:25, 17 February 2010 (UTC)

OK, so in that case, if I calculate: I have matter with a linear density of 2 g/cm, by 4 g/cm by 1 g/cm the density is then 8 g³/cm³. So then why is density defined as g/cm³? And I did look stuff up, I read Dimensional analysis and Quantity calculus, and density and Linear density, and none of them explained why the units don't work. Ariel. (talk) 03:41, 17 February 2010 (UTC)

Linear density is not defined for material in general, but for a structure in particular. To determine the linear density of your quartz bar you need to know its cross sectional area. The linear density is then the density divided multiplied by the area, not the cube root of the density.58.147.58.28 (talk) 03:48, 17 February 2010 (UTC)

(edit conflict) Linear density is sort of a specialized unit; you can't cube it and get actual density. To get denisty from linear density, you don't multiply the linear density in three dimensions, you divide linear density (g/cm) by the cross-sectional area (cm²) and then you'll get the density. The reason for this is that the linear density of a substance is a measure of all of its mass divided by its length in one dimension. If you want volume density, you need to include the other two dimensions in terms of length, but you don't need to count the mass again, since that number is already included in the linear density. So linear density divided by cross-sectional area will give you volume density (i.e standard density). --Jayron32 03:54, 17 February 2010 (UTC)

If your quartz bar had a cross section of 1 cm x 1 cm, its linear density would be 2.634 g/cm. If it had a cross section of 2 cm x 2 cm, its linear density would be 10.536 g/cm. — Sam 76.24.222.22 (talk) 04:00, 17 February 2010 (UTC)

Thank you all. I understand it now. For some reason I thought linear density is a measure of "number of units of mass" per length, i.e. that it's the same for all shapes of objects, just like density is the same for all shapes. Clearly my math in this question was wrong, and I will redo it. Ariel. (talk) 04:10, 17 February 2010 (UTC)

Yeah. Density is a intensive property because it is a property of the material itself irrespective of the amount of material. Linear density is NOT an intensive property, except in limited applications. Linear density is intensive with respect to length ONLY, and only if cross-sectional area is kept constant. If you alter the crosssectional area, you change the linear density of the material. It generally has to do with the applications of linear density. You only usually use it in situations where you are dealing with a material which you work with in relatively uniform, long amounts of it, like say yarn or railroad rails or 2x4's. You would, for example, be interested in the linear density of a particular type of cotton thread, but two different types of cotton thread would have different linear densities, even if the cotton fiber they were both composed of has the same volume density. --Jayron32 04:31, 17 February 2010 (UTC)

Medical devices, WWII-era occupied Poland

The device in this archival photo was used in the Lodz ghetto, ca. 1940–1944. My questions: what is it, and was it used for diagnosis or for treatment? -- Deborahjay (talk) 09:08, 17 February 2010 (UTC)

And this one as well: same questions as above. -- Deborahjay (talk) 10:24, 17 February 2010 (UTC)

Guesses: First may be a medical diathermy machine. Second may be radiation therapy, or maybe just diagnostic x ray. The second setting is clearly institutional like a hosp x ray dept. The first setting may be a home doctors office. alteripse (talk) 11:12, 17 February 2010 (UTC)

Image one: From the position of the doc's hand and the direction of her gaze, I would say she is draining his left pleural cavity with a chest tube.

Image two: Certainly looks like a glass X-ray tube inside the enclose. I would think that under war time conditions of desperately severe shortages, all x-ray therapy would have been discontinued. It had very low success rates and so priority would have been given to diagnostic uses. Also, the woman has her hand on the x-ray collimator which is used to produce sharper x-ray images. --Aspro (talk) 18:18, 21 February 2010 (UTC)

I'm on a barge travelling across Neptune, towed by a cable connected to the moon Psamathe...

... how fast would I be moving, if my moon-towed barge was skimming the uppermost clouds?

Thanks Adambrowne666 (talk) 11:15, 17 February 2010 (UTC)

Since the moon takes 9074.30 days to orbit neptune, your barge circles neptune once every 9074.30 days. Neptune has a circumference of 155600 km. So you are going 155600 km per 9074.30 days = 0.443952 miles per hour. Try this as well (click on the text of the result, then the orange link under it to get it in other units). Ariel. (talk) 11:38, 17 February 2010 (UTC)

wow - so that's what you plugged into wolfram alpha, and it understood what you wanted? Cool. Adambrowne666 (talk) 20:32, 17 February 2010 (UTC)

155600km / 9074.30days = 0.4440 miles per hour. Don't forget your significant digits. Dauto (talk) 14:25, 17 February 2010 (UTC)

As a comparison, a sloth will be cruising by you at 3x your speed. Googlemeister (talk) 17:24, 17 February 2010 (UTC)

Thanks, everyone. Of course, the Neptunian sloth is a little faster, so would be cruising by at almost 4X my speed. Adambrowne666 (talk) 20:32, 17 February 2010 (UTC)

I think it would be more natural to measure speed relative to the clouds, not relative to stationary space. Neptune rotates once every 16 hours. Your boat anchored to the moon is nearly stationary in the external frame, so if you are at the equator the clouds would be whizzing by you at ~9500 km / hr. Not exactly a leisurely pace. Dragons flight (talk) 20:52, 17 February 2010 (UTC)

A extremely good point! Here it is in wolframalpha. Since Psamathe has a retrograde orbit the speeds add. Ariel. (talk) 22:42, 17 February 2010 (UTC)

Yes, of course! thanks both of you, didn't think of that either. Adambrowne666 (talk) 23:08, 17 February 2010 (UTC)

Besides just orbiting Neptune, wouldn't Psamathe be rotating relative to Neptune? If you fixed the cable to a point on Psamathe and the cable stretched all the way to you on Neptune then the cable would start to wrap around Psamathe as the base point rotated relative to your position. Eventually, as Psamathe continued to rotate, you would be pulled from the surface of Neptune, into space, and dragged back onto Psamathe. Think of your sledge being a fishing hook, the cable a length of fishing line, and Psamathe and it's rotation as a fishing reel being wound backwards. •• Fly by Night (talk) 22:38, 18 February 2010 (UTC)

Yoiu could anchor your point at the rotational axis of the moon and limit this action. Googlemeister (talk) 15:42, 19 February 2010 (UTC)

Yes, good point, Flybynight, and good idea, Googlemeister - cable's hooked to a rotating joint on the moon's axis; also, it's able to play in and out to make up for Psamathe moving closer and further away. Problems solved, now let's get down to making it! Adambrowne666 (talk) 22:44, 21 February 2010 (UTC)

Time Capsule

If I took my iPhone and buried it in a sealed vacuum capsule, how long would it remain useable (assuming the discovers could put in a new battery/power source). Which components would fail first? Would the OS start up? TheFutureAwaits (talk) 11:49, 17 February 2010 (UTC)

Indefinitely, I expect. You need to bury it deep enough that it won't suffer significant temperature changes, and you need to make sure the seal will last, but if you do that I can't think of anything that would damage it. --Tango (talk) 14:19, 17 February 2010 (UTC)

Does an iPhone contain any electrolytic capacitors? They eventually leak. Cuddlyable3 (talk) 14:34, 17 February 2010 (UTC)

Some types of battery can leak after a few years, however. 195.35.160.133 (talk) 14:56, 17 February 2010 (UTC) Martin.

You'd probably want to remove the batteries before you tried this. APL (talk) 15:38, 17 February 2010 (UTC)

How many years before the wireless technology has completely evolved and dropped backward-compatibility? I would estimate at least 25-30 years, but it's hard to say. Some analog mobile telephone technologies from the late 1980s are still supported by the transmitter towers and network providers; stepping even farther back, many land-line phone providers still provide support for rotary telephones or pulse dialing (probably using emulation with a software system). It seems plausible that 802.11 or "3G" GSM / WCDMA telephones might still be supported decades from now, even if they are no longer mainstream. Nimur (talk) 15:03, 17 February 2010 (UTC)

I wouldn't count on it. I had to replace my analog cell phone two years ago when the towers around here turned off their analog transmitters; the first-generation digital phone that replaced it lasted less than a year before the transmitters were turned off. --Carnildo (talk) 02:57, 18 February 2010 (UTC)

i would agree that any electrolytic capacitors are likely to become more leaky with time. Other components should not show significant ageing effects. However, some semiconductors may be compromised by the effects of nuclear radiation (gamma rays and cosmic rays). —Preceding unsigned comment added by 79.76.229.198 (talk) 15:36, 17 February 2010 (UTC)

After a while, tin whiskers may (or may not) start to form, these could cause shorts. The causes of tTin whiskers are not fully understood, so I'm not sure that a good estimate can be given.

This could theoretically be repaired by the benevolent future-people who also replaced the batteries, but it wouldn't be easy. APL (talk) 15:38, 17 February 2010 (UTC)

Dopants within semiconductors could migrate, rendering the chips nonfunctional, over a very extended time. You specified vacuum, which would prevent the oxidation of copper or brass I have seen in hundred year old telephones and telegraph instruments. But I have heard that vacuum can promote switch contacts welding together (that might apply more to those carrying high current, not so much a problem in a phone). It can also cause evaporation of films of lubricant which help switches and contacts operate. Vacuum would accelerate leakage of electrolytic capacitors. I would not expect typical rechargeable batteries to survive long storage under the conditions specified. Temperature variation could cause by the breaking of conductive paths and connections. Communications protocols will likely move on so that the signals used in the distant future would be incompatible with those used by a wireless phone of today. General Motors sold very expensive OnStar systems for car communication from 1996-2002 model years which became unusable after 2007 (this coming obsolescence was not mentioned at the times the expensive systems were being sold). The 1996-2002 system was analog, and was abandoned in favor of digital, with no retrofit of a new transceiver offered to keep the service going. From that example it is hard to see why operators of wireless systems would go to great lengths to make decades-old communications systems still operable. Planned obsolescence dictates that old software packages or hardware systems be "no longer supported" a few years later so the consumer has to shell out for a new one. Edison (talk) 17:21, 17 February 2010 (UTC)

Even with the cel-phone network gone or incompatible, the iPhone would still be a decent PDA. APL (talk) 18:41, 17 February 2010 (UTC)

One more angle, how long before Itunes is no longer backward compatible with version x (whatever version you bury it with), making it useless unless you posses the proper version of Itunes to perform intermediate updates? It won't be any fun to have to suffer along with the collection of music from right now... --144.191.148.3 (talk) 21:47, 17 February 2010 (UTC)

But this thing wouldn't be a practical/useful object after that much time. It would be a collectors item, a curiosity or a museum piece. In 20 years, we'll probably have a 1mm capsule that can be implanted behind your ear that runs on power generated from vibrations due to your heartbeat and not only comes pre-packaged with every piece of music known to mankind and can update with new music as it's recorded - but can compose new music in any desired style by itself. Why on earth would you care what music an antique iPhone could play? That's like asking why you can't get much rap music on 78 rpm shellac records. SteveBaker (talk) 02:35, 18 February 2010 (UTC)

Plastics are in fact not everlasting. There are many types of plastics and other materials on the circuitboard alone, not to mention the plastics in the casing. These will react with air or components in other plastics. I heard a museum curator remark that cellphones he were collecting would become brittle and disintegrate in just a matter of decades. The flash memory cards in the IPhone may also degrade over time, the technology actually relies on trapping electrons behind an insulating layer and I'm sure there's several ways that could be degraded. Add to that the problem with electrolytte capacitors mentioned above and I think we'll have to accept that many of us are going to outlive our gadgets, even if we store them in a cool dry place. EverGreg (talk) 09:39, 18 February 2010 (UTC)

Air in vaccum (okay I'm aware it's unlikely to be a perfect vacuum but you get the idea)? Nil Einne (talk) 22:51, 19 February 2010 (UTC)

Seal it in a 'dry nitrogen' atmosphere not a vacuum (a lot of military spares are packaged thus). It will also maintain a higher partial pressure to discourages the evaporation of the volatiles in plastic components.

A lead shield will help to mitigate natural radiation damage. Slow down chemical degeneration by cryogenic freezing -- then it might just last to the end of your warranty period. If you live in Poland, maybe not even that long [2].--Aspro (talk) 18:51, 21 February 2010 (UTC)

Average world temperature

What is the average world temperature? I want to compare one country with an average of 21–33 °C with world average, but can’t find any reliable sources of world average. Caspian Rehbinder (talk) 13:59, 17 February 2010 (UTC)

The first picture of the global warming article might have the answer you are looking for. Dauto (talk) 14:33, 17 February 2010 (UTC)

Actually, the article I linked uses temperature anomaly instead of actual temperature. The article Temperature record since 1880 quotes: "1901-2000 global mean of 13.9°C". Dauto (talk) 14:45, 17 February 2010 (UTC)

This is can be a very difficult number to generate[3], and most sources will tell you the average variance per month, or the "anomaly." Here is a page that throughly goes through all of this stuff[4]. The website is biased in POV, but all the data is good and kept up to date. In short, according to United States National Climatic Data Center, the mean world temperature for January is 12.60 °C. When you compare the country's average temperature to that of the global average, make sure you compare the same years or months.Mac Davis (talk) 07:11, 18 February 2010 (UTC)

According to satellite data, global average temperature anomalies jumped from +0.29C in December 2009 to +0.72C in January 2010[5]. ~AH1^(TCU) 00:54, 20 February 2010 (UTC)

Ion list

Where can I find a complete list of cations and anions?--Mikespedia (talk) 14:13, 17 February 2010 (UTC)

The short answer is, "You can't". An anion is any moderately stable negatively-charged atom or covalently-linked collection of atoms, and there is an infinite number of such. Among the anions, there are a finite number of monatomic ones (like chloride, Cl^-), but when you start allowing multiple atoms you get things like hypochlorite (ClO^-), acetate (CH₃COO^-), and dodecyl sulfate (C₁₂H₂₅SO₄^-). It gets complicated fast. Our article on ions lists a very few monatomic and small polyatomic ions, but you can't create an exhaustive list. TenOfAllTrades(talk) 14:50, 17 February 2010 (UTC)

In other words, because there are an infinite number of stable ways to combine atoms, there are thus an infinite number of ionized forms. A comprehensive list might contain all the relevant ions for a particular domain, but it will never really be complete. Nimur (talk) 14:58, 17 February 2010 (UTC)

Since this is relatively answered, I'll steer it away with some nit-picking. Is there really an "infinite" number of stable ways to combine atoms? there clearly aren't an infinite amount of different components to molecules (elements and their isotopes), and I'm skeptical that their is an infinite amount of ways you can arrange atoms into molecules to get "stable" arrangements. I will add to this the note that I don't know nearly as much about chemistry as I would like, but the use of the phrase "infinite arrangements" for a concrete thing such as an Ions made question mark appear. Please elaborate if you don't mind, thanks! Chris M. (talk) 17:26, 17 February 2010 (UTC)

Actually, there probably are an infinite number of ways, owing to substances such as polymers and network solids. For example, a diamond is essentially a single giant molecule of carbon atoms, and something like polyethylene contains molecules containing millions of atoms each. With carbon-based molecules alone, there is no finite limit to the size of the molecule, so there is no functional upper bound to the ways they can be combined. --Jayron32 18:38, 17 February 2010 (UTC)

Ah, I had a feeling my lack of knowledge of chemistry would show when asking that question. Thanks! Chris M. (talk) 21:14, 17 February 2010 (UTC)

Eating coffee beans

Say that I have a bag of coffee beans and wish to obtain the effects of caffeination, but I lack the means to grind and brew the beans to produce coffee. How much caffeination will I experience by simply eating the beans versus drinking brewed coffee? Do the digestive fluids "brew" the grounds in the stomach, or will they pass through the digestive system without yielding up their caffeine? 129.174.184.114 (talk) 16:16, 17 February 2010 (UTC)

Are you planning on swolling them whole? Dauto (talk) 16:40, 17 February 2010 (UTC)

Brewing doesn't create caffeine and there are a number of foods that include solid coffee beans (tiramisu, chocolate-covered expresso beans). But the results of civet cat consumption of raw beans is worth a mention: (Kopi Luwak). Rmhermen (talk) 18:34, 17 February 2010 (UTC)

Yes, I am aware that brewing doesn't create caffeine. My question is whether brewing in near-boiling water is necessary to release caffeine from the beans. In other words, if I eat coffee grounds (not intact beans), will the caffeine in the grounds leech out in my stomach or will the caffeine remain "locked" in the grounds? 129.174.184.114 (talk) 23:01, 17 February 2010 (UTC)

I'm pretty sure you will get the caffeine from the grounds, warm water may be slower than hot, but it's in you for much longer. If you don't crush (or chew) the bean you might not any from that though. Ariel. (talk) 07:41, 18 February 2010 (UTC)

Cosmological argument and the fine-tuned Universe

I have browsed some related articles and from what I understand, the biological evolution is inapplicable in explaining the formation of the Universe and its components, as well as the symbiosis of beauty and functionality of some of its components. The expanding Universe should expand in some surrounding space, that is it’s a closed system in terms of the 2nd law of thermodynamics, and yet demonstrates a quite strange decrease in entropy since its formation. So could the intricacy of the Universe, which features numerous self-sustained, sophisticated components in itself, serve as an evidence of initial intelligent design (if there is nothing from nothing)? From what I've read, the murky Planck epoch for example does not explain, how the four fundamental forces have formed. Neither does the science explain, where all micro essentials like elementary particles come from (instead that could be easily explained with FTU concept, assuming that the Big Bang stuff for example was meticulously concocted in a stock cube fashion and then launched off to run). The article on cosmological argument cites Kaku's critical example on gas molecules, but I think the bouncing molecules or any such stuff moving in a Brownian motion pattern will never form something complicated and useful, unless driven externally.

Another issue of the fined-tuned Universe that came to my mind is the Earth atmosphere. It’s one of the Universe components, which features multifunctionality (protection from asteroids and excessive solar radiation, etc.), combined with nearly unquestionable beauty. We admire it since Gagarin and most likely even an ancient or medieval man would notice its beauty on photo without even knowing what it is. That is, neither the Earth atmosphere has evolved to suit us, nor we evolved to, which means that most likely it was made to be such intentionally. Also, are stars the closed systems under thermodynamic principles? If so, the historical decrease of entropy in space would be striking. So how such long-lasting set of nesting dolls could form and evolve randomly, including the Universe itself? Brand[t] 19:20, 17 February 2010 (UTC)

I don't know what you've been reading, but there is no surrounding space around the universe, the universe is, by definition, everything. The universe is expanding, but it isn't expanding into anything. Also, the total entropy of the universe has increased since the big bang, not decreased. Beauty is an entirely human concept that we have evolved. Things aren't inherently beautiful, there has just been a reproductive advantage to us considering them beautiful. I think once you resolve these misconceptions of yours, you'll find your questions are moot. --Tango (talk) 19:42, 17 February 2010 (UTC)

See Metric expansion of space, which has sections called "Understanding the expansion of space" and "What is the universe expanding into?" (Though I don't know why that section says that if space is infinite, this would be "easy to conceptualize".) Comet Tuttle (talk) 20:19, 17 February 2010 (UTC)

I am content to allow our concept of beauty to abide in metaphysics. The OP may find the article Intelligent design helpful. It is not a mainstream view that there is convincing evidence of initial intelligent design. Cuddlyable3 (talk) 20:22, 17 February 2010 (UTC)

Re: "That is, neither the Earth atmosphere has evolved to suit us, nor we evolved to, which means that most likely it was made to be such intentionally." I'd have to say we most certainly evolved to suit the atmosphere, if we had not we would of course not have survived. The atmosphere has changed plenty in the billion+ years life has been around and the life that did not evolve to suit it died off, as you would expect. Chris M. (talk) 21:13, 17 February 2010 (UTC)

The only honest answer is that we don't know why the universe has the properties and physical laws that it has. Our knowledge today is far better than that of our ancestors (to whom nearly anything could seem magical), and presumably our descendants will have a better and more fundamental understanding of the universe than we do today. However, we may never know the answer to "Why are things just so?". It is easy to say that life as we know it could not exist if the universe was much different than we know it to be. Of course, we also can not know whether other forms of sentient life might come to exist had things been otherwise, so it is difficult to know how significant our existence truly is.

Given our current state of ignorance (and the possibility that we will never know), I'd say that it is an entirely valid - as an article of faith - to assume that God or some other intelligent creator set up the laws of physics in just such a way so as to allow life to flourish. Such beliefs are essentially unscientific in the modern era since we have no meaningful way to test them, but if they help people find comfort and meaning in their lives, then I would say that they are nonetheless useful for those people. Dragons flight (talk) 21:20, 17 February 2010 (UTC)

It is entirely valid if you don't mind worshiping a god of the gaps. Dauto (talk) 03:46, 18 February 2010 (UTC)

If it were only a matter of people getting some comfort and meaning from an unprovable hypothesis - then I'd be fine with it too. But when they start to use that to prevent my kids from being taught about evolution in school - or to persuade gullible people to commit suicide by flying planes into buildings - then we really have to say "This Simply Isn't True" and mean it. A belief in a god that pushes the big red "CREATE UNIVERSE" button - then walks away is perhaps tenable - if unnecessary - but why does that lead you to have some kind of comfort? Only a god who actually intervenes on your behalf is of any practical use to you - and that's quite clearly ruled out by science - or indeed basic logic. Why pray to a god who walked away from the universe after pushing that big red button? SteveBaker (talk) 16:48, 18 February 2010 (UTC)

Actually, research by Victor J. Stenger has shown that this whole business of the universe being "fine tuned" doesn't entirely hold water. His work isn't published yet (AFAIK) but from what I gather he's found that provided that you assume only the conservation laws (which seem pretty reasonable 'immutable' properties of all universes), then you can't vary single fundamental properties - you have to move them in groups. When you do THAT, you wind up with a very large percentage of possible universes having the necessary properties to allow life to form. If that work turns out to be true - then rolling the dice and coming up with a universe with different constants which obeys these conservation laws would almost always result in a "reasonable" universe. He has written some details here. SteveBaker (talk) 22:18, 17 February 2010 (UTC)

I've never read anything by Victor Stenger before, but the argument in the essay you linked is shockingly naive. He starts by claiming that the alleged fine tuning can be confined to a four-dimensional parameter space; I don't think I believe that but I'll accept it for the sake of argument. Then he says that he investigated 100 randomly chosen values of those parameters varying by ±5 orders of magnitude around the real-world values, and found that many combinations yielded an acceptably large stellar lifetime. His formula for the stellar lifetime (found here) is of the form k x^a y^b z^c w^d where k, a, b, c, d are constants and x, y, z, w are the parameters. This means that the log of the stellar lifetime is a linear function of the logs of the parameters, so it will be larger than the central (i.e. real-world) value in exactly half of his parameter space. If the real-world value is larger than the acceptable lower bound then more than half of the parameter space will be acceptable. He should have realized that immediately, before he wrote the program. I don't understand how a (retired) professional physicist could be so dumb as to resort to statistical sampling for this problem instead of just calculating the output distribution. And why only 100 samples? Even a very slow interpreted BASIC (his program was apparently written in True BASIC) on a very old computer could handle thousands of samples per second. I can't see any reason to stop at 100 except to add spurious randomness to the plot and make it seem less trivial than it really is. At any rate, as trivial as this is, it would be an argument against fine tuning if stellar lifetime were the only constraint and if the parameter values he investigated were natural. But no one would have thought the parameters were fine tuned in the first place if those things were true. As you add additional constraints (and there are a lot of others) you can expect the acceptable parameter space to be whittled down to almost nothing. And he varies the parameters around the observed values. The electron mass is about 10⁻²² in natural units, so he allows it to vary from 10⁻²⁷ to 10⁻¹⁷. But the real question is, why isn't it 1? You certainly don't get an acceptable stellar lifetime if it's anywhere close to 1. This is essentially crackpottery. -- BenRG (talk) 08:48, 18 February 2010 (UTC)

Thanks for the analysis. I hadn't read anything by this guy before either - it seemed interesting that someone with some credible scientific credentials had actually tried to investigate this. But if he screwed up - then that probably explains why his work remains unpublished. SteveBaker (talk) 16:14, 18 February 2010 (UTC)

Selectivity effect. Countless universes with each its set of laws, and us humans happen to be in one of them wondering how come it sound this fine tuned. -RobertMel (talk) 23:40, 17 February 2010 (UTC)

That is one solution that has been proposed. There is not, and probably never will be, any evidence for the existence of other universes, though. --Tango (talk) 00:06, 18 February 2010 (UTC)

Picture a nearly infinite series of universes, some with physical constants such that there is no air on Earth, with us whining here on Ref Desk about how hard it is to breathe without air. There could only be human observers in universes where human observers could exist. There is no need to suppose that Divine Providence engineered a world just right for our needs. If randomly determined physical constants and laws of physics and chemistry were very wrong for us, we would not be here to complain about virtual absence of gravity, or Planck's Constant being 10²⁰ larger, or water contracting when it froze. There would be a vast array of very boring universes, some with no planets, others with no light, and others with very different rules for the formation of chemical compounds such that life (as we know it, carbon and water based) would never emerge. Edison (talk) 05:52, 18 February 2010 (UTC)

Are the physical constants indeed determined randomly? Are there any descriptions of what happens exactly when any or all physical constants and/or properties would be altered (to any degree)? Or what theoretically happens, when one starts messing around with them? Brand[t] 16:01, 18 February 2010 (UTC)

Without any intervention, they are determined randomly, some will never survive more than a fraction of a second, others will. It was even proposed some, a kind of natural selection, universes who survive long enough could be fecund and transmit their laws through a collapsing black hole. It would be like natural selection on Earth..., which means that more universes will emerge with the needed laws to form a fecund universe, and those sets of laws are the same which are needed for life to emerge. Since a universe which can produce many black whole and would survive more would be more fecund, the kind needed to form stars. See Lee Smolin about that. -RobertMel (talk) 16:16, 18 February 2010 (UTC)

That's not known to be true. There is no reason whatever to assume that they are determined randomly. We don't (yet) know WHY they have the values they do - but it might very well be that we find certain interrelationships that force the number to be what they are. The worst case scenario is that they are determined randomly - but over what range? If they are random - plus or minus 1% then that's a different thing than if they are random plus or minus 20 orders of magnitude. They cannot possible be random over an infinite range because then we wouldn't be here...and we are. So even if you assume random settings of these parameters, you have to come up with some mechanism that limits the range - and if/when you find that mechanism, it might very well be that the randomness is limited to plus/minus one part in a trillion. We simply don't know. This discussion only comes about because the Intelligent Design nut-jobs want to make it sound like the answer is SO random that there had to be a designer. SteveBaker (talk) 16:24, 18 February 2010 (UTC)

It's true that there is no reason that the laws are set randomnly as in without range. But, I never meant to say that there was no range, ranges could exist, but if there are infinit numbers of universe, in the scale which could somehow compete with a boundless randomnity, then ranges don't need to exist. -RobertMel (talk) 16:41, 18 February 2010 (UTC)

If there are an infinite number of universes with randomly set parameters for each then the problem is trivially solved. The difficulty only exists if this is a small, finite number of universes (like "one") and the values are determined randomly and over a very large range and if over a large fraction of that range, no life of any kind is possible. But even then, the anthropic principle is a perfectly valid explanation in the absence of something more satisfying and is more than enough to deny the necessity of an intelligent designer. However, science isn't here to disprove the existence of god(s) (although it often looks that way) - it's here to find answers to deep questions. For that, the anthropic principle is useless. We would very much like to know why these constants are the way they are - are they determined by some deeper relationship? Could they have been different? Did they come about randomly? If so, over what range? Are there multiple (or even infinite) universes - all with different values? These are all great science questions that would lead to a greater understanding and perhaps even some interesting technological spin-offs - but we don't need to answer any of them in order to say conclusively that an intelligent designer isn't required. SteveBaker (talk) 17:04, 18 February 2010 (UTC)

"we don't need to answer any of them in order to say conclusively that an intelligent designer isn't required" - I'd say that is just as much an article of faith as saying that an intelligent designer is required. We don't have enough information to draw a conclusion. Why does a universe exist at all? If there are multiple universes, then why should that be? Etc., etc. The anthropic principle is a statement about the nature of our existence, but it doesn't explain the more fundamental question of how did there come to be a universe like ours. Maybe someday we will know the answers, but right now saying that God could definitely be excluded seems just as unfounded as saying that God must definitely be the answer. Dragons flight (talk) 21:19, 18 February 2010 (UTC)

If I had said that we didn't need to answer this in order to prove that an intelligent designer does not exist - then you might maybe have a point - but I didn't. This is evidence that an intelligent designer isn't required - which is quite something else. I can show that an ID isn't required by coming up with any hare-brained theory for the formation of the universe. To show that there definitely was an ID, you have an awful lot of proof to come up with...and we all know you don't have that or the question would already be solved. What the anthropic principle shows is that even if the probability of a single universe having exactly the right properties for human life to form is exceedingly small - providing it's not exactly zero, then we have an acceptable hypothesis that doesn't require ID. Hence suggesting that this 'fine tuned' property is proof of ID is pure nonsense. It proves nothing of the sort. The flip side of that argument would be if we could somehow prove that the universe HAD to form with a set of properties that would inexorably lead to intelligent life - then we would have proved conclusively that no intelligence was involved in the setting of those parameters. However, we have not shown that yet - and maybe we won't ever manage to do that. So this leaves us in a state of knowledge that says that we don't require ID - and that the ID proponents may have lucked out and guessed the truth against spectacular odds. Occams' Razor and Russels' Teapot suggest to rational people that the simplest explanation is the best - hence, no ID is where the smart money is...scientifically speaking. SteveBaker (talk) 22:49, 18 February 2010 (UTC)

I still disagree. Your "acceptable hypothesis", if true, merely pushes back the question of primary cause one more notch. Or to put it another way, the man-behind-the-curtain (if there is one), would simply be doing something like creating a multiverse that allowed for the creation, however improbable, of a universe like ours. That seems to be a property of all such theories, in that they can only push God further back into the shadows, but they can't rule him out any more than any existing evidence can rule him in. Eventually one might ask: "If God's only role was create the rules that eventually led to the creation of the universe, then is that really 'God' as most people envision him?", but that is rather something of a diversion. Did an intelligent process have any role in creating the physical laws that allowed our universe to exist? I don't know, but as long as physics is based on the assumption of physical laws whose origins are unknown, I don't see how any hypothesis could claim to exclude the possibility of God. Dragons flight (talk) 23:54, 18 February 2010 (UTC)

I can't believe you said that! Your "God hypothesis" also only pushes things back one more notch. Why do religious/ID people never address the question (which for scientists is inevitable) of "Where did the designer come from?". The only answers out there are of the "God was always there" or "Time is meaningless for God" or (worse still) "It is heresy to ask such questions" variety. But if that's an acceptable answer, then so should be a scientific answer such as "Time and space were formed by the big bang and therefore it is literally meaningless to ask what came before the singularity". That's a solution which (if true - as was recently believed) would not push things back one more step - at least no more than "Time is meaningless for God" does. You may be right that there is no ultimate way to disprove a god. What there most certainly IS is the ability to progressively narrow the influence that this god can possibly have on the subsequent progress of the universe. There comes a point (and I think we're already WELL past that) where if there is a god, there is no point in worshipping him - no benefit that he can possibly provide us with - he might as well not exist in that case. A hypothesis which predicts no new, testable/observable phenomena has zero value. At which point, we might as well simply apply Occam's razor and go with the simplest answer. SteveBaker (talk) 03:41, 19 February 2010 (UTC)

The idea of a Fine-tuned Universe is an interesting one to consider, but the degree of "fine tuning" (if any actually exists) is often grossly overstated, or at the very least stated in a way the leads to gross misunderstanding. I've heard some proponents of the fine tuning argument state that if you used a scale that stretched across the entire universe to representing the possible range of values for the strength of the force of gravity, then life would not be possible if the actual value varied by as much as one inch from what it is. People may take from this that the gravitational constant must not vary by one part in more than 10²⁸ (1 inch / 93 billion light-years) when in fact the actual value of G (6.67428(67) x 10^-11 m³kg^-1s^-2) is not even know to a precision greater than one part in 10⁴, and could presumable vary by considerably more than that without life extinguishing consequences. The trick is choosing the "range of possible values" (possible according to who and why?) as mind boggling huge as desired. I do wish that our Fine-tuned Universe article went more deeply into the numbers that are used and the justification offered for their use. 58.147.58.28 (talk) 02:04, 18 February 2010 (UTC)

I find the idea of a fine tuned universe a complete nonsense. First we don't know if the universe could actually be any different than it is. There is to reason to believe either way. Second we don't know for a fact that life would not be possible in a different universe, or how different it would have to be to prevent life from existing. That doesn't sound like strong grounds for anything as far as I can see. Definatly not strong grounds for a proof of the existence o god. If that's all that the god believers have, I think they are better off simply saying that they believe in god out of pure faith and that is that. Dauto (talk) 04:12, 18 February 2010 (UTC)

I defer to Douglas Adams: ". . . imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be all right, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for." Imagine Reason (talk) 04:18, 18 February 2010 (UTC)

The presence of multiply universes may additionaly point to external intervention I think. If such complex object as Universe evolved randomly, then why far more simple things like metal details for example do not assemble into a car? The countless universes should be complex too, which reduces their chance of being formed randomly IMO. I think it is very safe to suppose that initially there was nothing (the same way when I want to make a snack without having ham and bread). Then something from nothing has appeared like protons and neutrons, which suggests the external assistance. Brand[t] 06:39, 18 February 2010 (UTC)

I think it is safe to say that there will always be a why or a how beyond the current limits of our knowledge, and one can always choose to believe that the ultimate answer to how our universe came to be is God. I have no objections to that, if that is what you choose to believe. However, it is worth noting that a watchmaker God that sets everything up and then lets it evolve according to fixed and scientific laws is fairly different than the interventionist personal God that many people envision when they pray. Dragons flight (talk) 08:25, 18 February 2010 (UTC)

It also doesn't help with the task of explaining things. If you have a gap where science does not yet have an answer - and you insert a "god" in there - you really haven't added anything to the explanation because explaining how the god got to be there is a vastly more difficult question than explaining the gap that you dropped the god into in the first place. This is becoming most evident as science begins to plug some of the more traditional gaps.

But in this particular case, we don't need a god to explain why the universe is the way it is. Although we'd like a better explanation, the anthropic principle is actually a perfectly sound scientific explanation. In short, if those 'fine-tuned' variables are truly randomly set at the point when the universe popped into existence - then beings exactly like us can only be there to comment on the matter if the dice rolled the way they did. Sure, it might only be a one in a trillion chance that the universe could support life - but if there are a trillion parallel universes - or if the universe is re-made over and over - then sooner or later one will come up with intelligent life - and by definition, that's the one we'll happen to be living in. So we don't have a "gap" here...there is no need for a god to fill it. It would be nice to be able to come up with a reason why it's not a one in a trillion chance but maybe a one in ten - or better still, an absolute certainty - but even without that, we don't have to postulate an even harder to explain 'thing' to cover some horrible error in science as we know it. What we know is that no matter what the odds of getting a universe like ours - so long as the probability isn't zero - then this is how it turned out. If you roll three dice and you happen to get three sixes - do you seek an explanation as to WHY they came up that way? No! You realise that this was always a possibility - and that's what happened. SteveBaker (talk) 16:14, 18 February 2010 (UTC)

After millions of years of its existence the Brownian motion failed to produce something more than just a random bouncing. So it’s absurd to state that our universe started to produce the necessary stuff and subsequent components by itself, as if it were intelligent. I share the view that the constants were not set randomly, but if so, the logic, mine at least, suggests them to be affected externally and, most likely, to be rendered immutable to avoid terrific troubles.That’s why these values are constant, not variable like many others. And since God by definition is not detectable scientifically, being transcedental , I think the gap could be filled in such a way. Also, any possible intelligent designer including God would be naturally wiser than we, rendering us incapable to adequately describe him. Brand[t] 21:02, 18 February 2010 (UTC)

I'm not sure what that disconnected set of ideas proved - but let's take your reply a bit at a time:

• After millions of years of its existence the Brownian motion failed to produce something more than just a random bouncing. - Firstly, it's billions of years - not millions - secondly, how do you know it failed to produce something? Random bouncing will (over enough volume and time) eventually produce the complete works of Shakespeare. But it can destroy things just as quickly. You don't know that.
• So it’s absurd to state that our universe started to produce the necessary stuff and subsequent components by itself, as if it were intelligent. - The word "So" implies that your second thought follows from your first. But random motion can produce meaningful things (eventually) - if you roll 100 dice enough times, sooner or later, they'll all come up 6's. If you pack them into a 10x10 grid, they could equally probably produce a crude approximation of the MonaLisa (actually, more probably). That's not "intelligent" though - that's just random. Well, the appearance of the first self-replicating molecule could perfectly well have come about randomly - and having done so, would inexorably evolve into something like the life we see around us today. You don't need intelligence to get complexity.
• I share the view that the constants were not set randomly, - I didn't say that I believed that. I have an open mind about how those parameters came to have the values they do.
• but if so, the logic, mine at least, suggests them to be affected externally and, most likely, to be rendered immutable to avoid terrific troubles. - The trouble with "affected externally" is that for us to be talking about a "universe" there can't be "externally" because the word "universe" means "absolutely everything". If you want an external influence, you have to explain about how THAT came about. This is the massive problem with ID. If you finally prove that there is a "designer" out there - the very next words out of your mouth had better be "...and the way the designer came about was..." with a ton more explanation. The usual cop-out is to say "The designer was always there" or "Time does not exist for the designer". But when scientists offer the much simpler explanation that "The singularity that formed the big bang was always there" or "Time does not exist for the singularity", you ID'ers get upset and accuse scientists of failing to answer the question. So - how about you explain why the ID's "designer" offers us any additional explanation?
• That’s why these values are constant, not variable like many others. - Eh? So you're saying that God is what stops the charge on the electron from changing over time? As "God of the gaps" arguments go - that's the mother of all tiny gaps! Perhaps god also stops the value '6' from magically becoming '7'? Constants are (by definition) constant.
• And since God by definition is not detectable scientifically, being transcedental , I think the gap could be filled in such a way. - God is only undetectable so long as his believers continue to retreat into every smaller gaps. "God created created the heavens and the earth"...but when we prove conclusively that the earth was formed by gravitational forces operating on the stellar disk - you guys don't go "Huh! Well, whatddayaknow? We must have been wrong!" - instead you retreat a bit into a smaller gap. We prove that the story of Genesis is complete bullshit - and you retreat into "Well, that's just a metaphor". When we show that above the clouds, there is no heaven - you push it off into some metaphysical plane where we can't disprove it anymore. This "not detectable" approach forces your beliefs into smaller and smaller gaps. In the end, the problem is this: For a god to be entirely undetectable - he has to hide very, very carefully. Answering prayers is detectable, miracles are going to be violations of thermodynamics and conservation laws that science can spot a mile off. Your great and mighty god is reduced to cowering in tiny little gaps where science can't (yet) find him. That's not really a very pretty picture is it? So, sure - you can plug a god into the gap where science doesn't know how these numbers came about - but what do you do when we prove conclusively where they actually did come from? You have to run and find another gap.
• Also, any possible intelligent designer including God would be naturally wiser than we, rendering us incapable to adequately describe him. - You have no proof of that. Tell me - if your designer is so amazingly wise - why the hell did he come up with such an amazingly crappy design for the Recurrent laryngeal nerve in the Giraffe? SteveBaker (talk) 23:33, 18 February 2010 (UTC)

Well, I would reply in the same order.

• Billions of years are naturally better and in order to calculate the probability of producing the complete works of Shakespeare from the Brownian motion you should take some limited time span (800 billion years for example), not infinity. But is there a single evidence, that the Brownian motion has produced something sizeable and useful after billions of years have passed? Imagine another situation. A single normal car has everything to set it in motion. But it will not move unless we affect the ignition and accelerator. Maybe someday something will fall down, penetrating the roof and pressing down the pedal, but even after the infinitely long period of time (after the infinity, roughly speaking) nothing would be able to turn around the keys and ignite the engine. That’s why it’s impossible that our universe appeared and evolved randomly, the probability is zero I think. So the basic idea of specified complexity is quite plausible.
• I didn't say that I believed that. You state above: There is no reason whatever to assume that they are determined randomly and even: A belief in a god that pushes the big red "CREATE UNIVERSE" button - then walks away is perhaps tenable.
• The word "universe" may mean "absolutely everything" just in terms of our science. A single cat doesn’t know, from what and how it evolved. But unlike that cat, our advantage is that we as Homo sapiens can make plausible assumptions even within the cosmological argument, other than throwing dice around.
• So you're saying that God is what stops the charge on the electron from changing over time? I believe yes, since that value is a constant, unlike the values of such fundamental force like gravitation which may vary.
• "God created created the heavens and the earth"...but when we prove conclusively that the earth was formed by gravitational forces operating on the stellar disk - you guys don't go "Huh! Well, whatddayaknow? There is an artificial gravity, which means that initially it would not occur unless we influence the spaceship in a proper way to rotate it. Besides, actually there is an example of divine omnipotence, when God turned detectable and accessible to humans – Jesus (unless you don’t believe in him or think he was merely a human). He was certainly able to scientifically explain the divine engineering, in proton-neutron terms for example, but for obvious reasons did not – it was a different historical period of mankind. Brand[t] 06:23, 19 February 2010 (UTC)

I don't quite understand what you are getting at, your arguments seems disorganized. How can you suppose the chances are zero, under what basis? It is pointless to discuss the improbability of our existance to prove a God, because had we been not there we would have never asked those questions. (selectivity effect) It took a lot of orders (which means, a lot of accidents) for us to be here. The main point is that, for example us humans, we would have never been here, without all the other nature trials which we have evidence of. Of course we see order, because we are here, we being here required this order, which gives the illusion of a creator. The accident turning the key would have been irrelevant had there been no car in the first place. Some cars will be destroyed and turned into another thing until by accident the key is turned. Suppose that insteed of the key turning the engine on, it gives the car awarness of its seroundings and of its own existance. What the car will observe, it will observe the complexity of its own existance, and the complexity of all the machinery which were created by accident to permit its own creation. The car will believe it was created by a being until it discovers all the other trials. This amount to when Darwin discovered evolution. As for the laws of physic which seems fine tuned. Of course they will seem fine tuned for you and me, because if laws didn't permit your existance you would have never been here. So what you see as orderly laws is expected, just by the fact that an evolved being such as yourself is trying to understand and questioning their improbability. Of course there can alws be a god setting the laws, but you have to explain that being own existance.

We one day may simulate a universe in a Quantum computer, with entities which become self aware and wondering about their own existance, making of us gods. There will be nothing which would permit those entities to distinguish those universes from ours. But I highly doubt that's the kind of god which you had in mind. -RobertMel (talk) 15:53, 19 February 2010 (UTC)

I have already programmed a computer to be self-aware. It is not very smart, but it is self-aware. It speaks very little English, but it does know the answer to one question, "Are you self-aware?" It always answers "Yes" to this question, and it answers "I don't understand your question, because the universe is so very complicated and I have limited processing power" to every other question. That poor computer - it suffers from a perpetual crisis of existentialism - but it is indisputably self-aware! All you have to do is ask it! Nimur (talk) 17:25, 20 February 2010 (UTC)

How can you suppose the chances are zero, under what basis? Existing evidence. Our universe is not a crude approximation, but a well-ordered reality. It means that the random cause, instead of tossing dice, packed into a 10x10 grid (which is already an evidence of external intelligent influence) throughout zillions of years, would have needed an oil and canvas at least (i.e. appropriate and meaningful stuff) to produce a Mona Lisa-like image. I think Dembski’s problem is that he applies specificed complexity to living forms instead of non-living. Unlike live forms, the matter or any non-living form has no stimulus to appear and/or evolve in a meaningful manner by default and thus requires an external assistance. But every physical life form requires matter to appear and evolve. Also, a random cause would make all physical values to be either constant (fixed) or variable in my opinion. But the fact is that some values are constant and some are variable.

The accident turning the key would have been irrelevant had there been no car in the first place. Some cars will be destroyed and turned into another thing until by accident the key is turned. Do cars appear out of nothing? Turned into another thing until by accident the key is turned? Turned by what? Which natural accident would turn the keys? The creator, whoever he is, seems the only one to act beyond the confined laws of science (like admin), including those not yet discovered primarily because they were created by himself (the same way when we develop and pass various new laws, which did not previously exist – civil, criminal etc). I would add that God (or an uknown ID, as you wish) rendered himself generally undetectable probably because his existence and the complexity of his acts exceeds human understanding and is coupled with a certain degree of freedom of choice. That’s why one can only operate with observations and comparisons, but applying duck test, that would suffice, sapienti sat. Brand[t] 08:38, 20 February 2010 (UTC)

In my world view, cars have just assembled naturally. Of course, it took 4 billion years of evolution to get some of the assembly equipment in good working order. As for a fine-tuned universe, it seems like a dead-end argument since whatever airtight case for fine-tuning you come up with must also apply to whatever universe your "external force" grew up in. --Sean 16:46, 18 February 2010 (UTC)

You misunderstood the "sentient puddle." It is a story about how life can fit in the universe nicely by having developed in it and not at all designed for it. 67.243.7.245 (talk) 14:09, 19 February 2010 (UTC)

Brand, I don't you're really understanding Steve's points. Take the dice example, see this [6]. But basically the oil and canvas are the particles in the universe which due to the laws of nature have the ability to form complex structures. Ultimately there's no evidence for a god but what I would like to know is why you think a God that made himself undetectable deserves any attention? He created the universe. Well fantastic, that's quite a feat. But it doesn't mean that God was Jesus and if he doesn't perform miracles/answer prayers/etc. then why should I build my life around it? Do you spend your time worshiping the man who invented the lightbulb, or the automobile? It's fantastic that they did it but enjoy it and get on with your life. TheFutureAwaits (talk) 00:40, 22 February 2010 (UTC)

Capacitor

When a capacitor charges, both the negative and positive plates will always have the same charge (ie current in = current out). Why is that? —Preceding unsigned comment added by 173.179.59.66 (talk) 19:29, 17 February 2010 (UTC)

Current passes through the capacitor which builds up a charge of stored potential energy in the form of a voltage difference between the plates. See the article Capacitor. Cuddlyable3 (talk) 20:13, 17 February 2010 (UTC)

Yeah, I understand that...but why are the two charges equal, and not different? —Preceding unsigned comment added by 173.179.59.66 (talk) 21:13, 17 February 2010 (UTC)

Isn't the charge stored in the dielectric separating the plates? One dielectric, one value for charge. Add or take away electrons from either plate, and the one value of charge in the dielectric changes. In a Leyden Jar, the two conductors (inner and outer can be removed and grounded, then the capacitor reassembled, and found to be charged, because the charge was stored in the dielectric. Edison (talk) 21:22, 17 February 2010 (UTC)

No, the charge is in the plates, the dielectric must be nonconductive. The two sides normally hold equal amounts of charge because they are connected to metallic wires which supply large quantities of movable electrons -- if one side had an excess of charge, it would attract charges from the wire on the other side until the charges were balanced. If you disconnected both sides of the capacitor, it would become possible to have unequal charges on the two sides. Looie496 (talk) 23:10, 17 February 2010 (UTC)

Of course the dielectric is nonconductive. But note that a disassembled capacitor, with the metal plates thoroughly grounded, when reassembled is found to be charged once again, supposedly because of the charge stored in the dielectric. If it were stored only in the plates, then shorting them together and to ground after disassembling a Leyden Jar ( a common lab demo in college physics) would prevent the reassembled capacitor from being charged ( without connecting it again to some source of electricity). Edison (talk) 00:39, 18 February 2010 (UTC)

Thanks for the simple answer! —Preceding unsigned comment added by 76.68.246.12 (talk) 23:42, 17 February 2010 (UTC)

My thoughts are: charge (electrons etc) is moved from one plate to the other when charging. So one plate ends up with a charge +Q that has been supplied by and moved from the other plate that now has acharge of -Q. Charge exists on the plates (or the surface of the dielectric). By contrast, the energy is stored in the dielectric. In the above case, when the plates are removed, (most of) the stored charge will then reside on the surface of the dielectric. This charge will spreed out onto the plates when they are reattached. What happens when one side of the capacitor is connected to the earth (a source of infinite charge)? —Preceding unsigned comment added by 79.76.229.198 (talk) 01:57, 18 February 2010 (UTC)

You could charge an ungrounded Leyden Jar or capacitor to any voltage which was not so high as to rupture the dielectric. Then you could connect one plate to ground: no effect on the voltage across the capacitor, or the energy stored in it. Next, connect only the other plate to ground: again the voltage and stored charge are unaffected. The earth is indeed a giant conductor, but a giant conductor connected to one side of a capacitor would not change the charge, it would just change the voltage relative to that ground, causing one plate to be at zero volts from ground and the other to be at the full voltage relative to ground. Transformer secondary windings work similarly. Edison (talk) 05:39, 18 February 2010 (UTC)

Geological history of CT or North Eastern US coastline

I don't know where to go to find the geological history of CT, US (or NE US coast). Mostly interested in knowing if and when a huge galacier passed through this area. --Reticuli88 (talk) 19:53, 17 February 2010 (UTC)

• Wisconsin glaciation. Rmhermen (talk) 21:34, 17 February 2010 (UTC)

See also Laurentide ice sheet. Deor (talk) 23:45, 17 February 2010 (UTC)

And here is a brief account that focuses on Connecticut in particular. Deor (talk) 00:28, 18 February 2010 (UTC)

Semen and skin

okay, this question could be slightly improprious, so stop reading if you want.

I heard that human semen is excellent for the compexion of the face; is this true? Would rubbing semen in one's face actually be good for the skin? If so, then why? 82.113.106.198 (talk) 19:53, 17 February 2010 (UTC)

We can refer you to the article Semen. I know of no reliable source for what you have heard. I have changed the question title for easier reference noting that WP:NOTCENSORED. Cuddlyable3 (talk) 20:09, 17 February 2010 (UTC)

It would be a very amusing study to read if a study was carried out to study this hypothesis (or maybe it already has been done?). Acquiring funding and volunteers though might be a challenge. --antilived^{T | C | G} 23:58, 17 February 2010 (UTC)

College sophomore psychology students would sign up for almost any boring experiment or indignity for a few dollars or some course credit. This included studies of sexual arousal, or experiments involving painful electric shocks. The difficulty would be getting such an experiment as the one described by the questioner approved by the "human subjects committee." Edison (talk) 05:29, 18 February 2010 (UTC)

I find it tends to make my skin rather tight and shiny when dry. —Preceding unsigned comment added by 79.76.229.198 (talk) 01:59, 18 February 2010 (UTC)

There are some data on Facial_(sex_act)#Cosmetic_usage regarding this matter.--121.54.2.188 (talk) 02:00, 18 February 2010 (UTC)

Tangentially related is Semen#Psychological aspects. Which is worse, acne or depression? 58.147.58.28 (talk) 02:16, 18 February 2010 (UTC)

Reaching the conclusion that semen must chemically act as an antidepressant is a strange one. Wouldn't it make more sense to say women who have been getting laid more are happier? Mac Davis (talk) 06:57, 18 February 2010 (UTC)

They compared groups with/without condom use. Ariel. (talk) 03:53, 19 February 2010 (UTC)

Did they try to account for confounding factors like differences between the groups other then a regular dose of semen? I'm sure it's occured to many as it did to me that there's likely to be a difference between the average of both, for example women who have sex with men without using condoms may be more likely to be in a committed relationship. As for those who aren't in a committed relationship, the women who don't use condoms may be more likely to trust even casual partners and/or be move naïve about the risks of sex and may be more relaxed (well until they get a STD or pregnant) whereas the women who do use condoms even though they do use condoms may still be more concerned about the risks and so may not find sex as enjoyable. Nil Einne (talk) 21:26, 21 February 2010 (UTC)

Are you sure you weren't told a fib? I know someone who told his girlfriend that semen was full of nutrients that women couldn't get any other way, for obvious reasons. She believed him...--92.251.162.146 (talk) 22:00, 21 February 2010 (UTC)

Variables in procession

can anyone explain what the various constants in this article stand for, notably R and q are given without explanation Lense–Thirring precession

Cheers —Preceding unsigned comment added by 129.67.116.172 (talk) 20:47, 17 February 2010 (UTC)

I can only offer wild guesses (R probably is the radius of the large rotating mass), so I have added a request for expert attention, see Talk:Lense–Thirring precession#Expert attention needed. -84user (talk) 14:07, 18 February 2010 (UTC)

Thank you. I hope someone can help.

Outgassing on Earth and Mars

Earth is beleive to have runaway greenhouse effect when it is on the way as the sun warms up. Because Earth and Mars is bigger I thought the outgassing would be slower than the outer planet's moons. I still don't what what it means when Earth becomes Venus like planet. Will it's atmopshere become thicker. During this time it is possible that as Mars's surface temperature gradually rises, carbon dioxide and water currently frozen under the surface soil will be liberated into the atmosphere, creating a greenhouse effect which will heat up the planet until it achieves conditions parallel to those on Earth today, providing a potential future abode for life. From Mars citation from Formation and evolution of the solar system said Mars may become like earth again and Mars is only little bigger than Titan when sun just heats up Mars atmosphere can become thicker but I wonder if it can have any oxygen and can have a watery surface. This shows Mars atmosphere won't just leak away. This source is cite from google books and it is not speculation.--209.129.85.4 (talk) 20:50, 17 February 2010 (UTC)

Atmosphere to boil away on Earth

On earth ocean boil at 100 C (212 F) but what temperature will our atmosphere black out into space and become like Moon is it over 600 F?--209.129.85.4 (talk) 20:52, 17 February 2010 (UTC)

I don't know what the actually temperature would have to be, but given that Venus has >90 times as much atmosphere as we do and a surface temperature over 850 F (450 C), I think we can confidentially assume that the temperature to boil away the whole atmosphere is over 600 F. Dragons flight (talk) 20:58, 17 February 2010 (UTC)

The ocean certainly would not boil at 100C. It is salt water which means it has a lower boiling point then regular water, various sources in quick google searches point to a change of around 20 degrees in boiling point, but it various depending on the salinity of the particular part of the ocean. Chris M. (talk) 21:09, 17 February 2010 (UTC)

Salt water boils at a higher temperature than fresh water, not a lower one, per Boiling-point elevation. Having something in solution also lowers the freezing point, per Freezing-point depression. Sea water is said to boil at 103.7 C (compared to 100 C for pure water). Edison (talk) 21:17, 17 February 2010 (UTC)

Not sure how useful a comparison with Venus is since the gas properties of CO2 and the N2 O2 mixture we have are quite different. Googlemeister (talk) 21:10, 17 February 2010 (UTC)

On the other hand, Venus has more N2 than we do, and if you boil the biosphere and the oceans you'd destroy our O2 and get a lot of CO2 on Earth as well (though no where near as much as Venus has accumulated over billions of years). Dragons flight (talk) 21:39, 17 February 2010 (UTC)

Have you tried looking this up on Wikipedia ? The earth losses gaseous oxygen all the time because it can get enough kinetic energy to escape. The ionic oxygen then corrodes the artificial satellites. There is more here: Atmospheric escape--Aspro (talk) 19:10, 21 February 2010 (UTC)

Question about male genitalis

Why do male genitalia flop around?

The testes work best at temperatures slightly less than core body temperature. This is presumably why the testes are located outside the body. See the article Testicle. The Penis that forms the other part of the male genitalia must project in order to be able to penetrate the female genitalia. Please sign your posts. Cuddlyable3 (talk) 21:39, 17 February 2010 (UTC)

And what's more, observation has demonstrated that many animals streamlined for marine life (cetaceans, for example) exhibit internally located testicles that are surrounded by a venous plexus that effectively lowers the regional temperature. DRosenbach ^{(Talk | Contribs)} 13:51, 19 February 2010 (UTC)

glacial lake in siberia

File:Last glacial vegetation map.png This map shows an enormous lake covering eastern Siberia during the last ice age. What was its name so i can look it up? —Preceding unsigned comment added by 70.29.47.142 (talk) 21:32, 17 February 2010 (UTC)

It's hard to tell which lake you mean - but if you bring up Google Maps, you should be able to zoom in and find it very quickly - IF it's still there...it probably isn't - in which case it may not have a name. SteveBaker (talk) 21:47, 17 February 2010 (UTC)

It is the blue area covering eastern Sibera and north of the bering land bridge. Blue on the map means a lake. It is not still there, it was there in the ice age. I would like to find out more about it. there are names for the ice age lakes in north america like Lake Ojibway. 70.29.47.142 —Preceding unsigned comment added by 70.29.47.142 (talk) 22:07, 17 February 2010 (UTC)

I don't think that's a lake; it's an area of "polar and alpine desert". The two colors in the legend of File:Last glacial vegetation map.png are virtually indistinguishable, at least on my monitor. Deor (talk) 23:34, 17 February 2010 (UTC)

I checked the colours with Gimp and you're correct. FYI lake colour is 0094c8 and polar-and-alpine is 00a4c0; the two are very close indeed. -- Finlay McWalter • Talk 00:07, 18 February 2010 (UTC)

thank you. Does that mean Tibet was not a lake either? I don't see how it could be if there were still mountains there. Thank you for helpimg. 70.29.47.142 —Preceding unsigned comment added by 70.29.47.142 (talk) 00:47, 18 February 2010 (UTC)

Yes, it looks to me like Tibet was another "polar and alpine desert" area. As far as I know, there have never been freshwater lakes of that size on the earth. Deor (talk) 18:34, 18 February 2010 (UTC)

The supposed lake in Siberia is contiguous with the Arctic Ocean, which would make it an ocean, not a lake. Here's another question, though. I know that there were some very large lakes in North America during the Ice Age (such as Lake Bonneville and Lake Lahontan). Why aren't these shown on the map? --Smack (talk) 20:01, 18 February 2010 (UTC)

February 18

A greenhouse on Mars

If you put a large air-tight greenhouse on Mars and fuilled it with air, how warm would it get? Would earth-plants grow in the Martian "soil"? Maybe with some human 'compost' mixed in? 78.146.206.38 (talk) 00:00, 18 February 2010 (UTC)

To answer the first part, there is no theoretical barrier to designing a solar greenhouse on Mars that operated at comfortable temperatures of plant life. Dragons flight (talk) 00:14, 18 February 2010 (UTC)

The temperature would depend on the latitude. Climate of Mars#Temperature indicates that temperatures do get up to nice warm temperatures (27 °C max), presumably on the equator. With the (literal) greenhouse effect, the temperature inside your greenhouse would be higher than the surroundings, so anywhere reasonably close to the equator should be fine temperature-wise. The Martian soil might be suitable for the growth of Earth-plants - it seems from that article that more research is required. --Tango (talk) 00:18, 18 February 2010 (UTC)

The temperature would drop quite low, especially at night in the winter, unless there was sufficient thermal mass and a high insulation level. Mars gets on average only 43% the solar intensity or "insolation" received on Earth per [7]. The mean surface temperature (outside the greenhouse) is only -63C (per the NASA site, varying with season and latitude). The air pressure is very low, so a greenhouse dome would have to be quite strong to hold in enough airpressure for earth type plants. See also a NASA project looking at a Mars greenhouse. Apparently 1/4 of earth normal pressure would suffice. Actually sounds doable. The Mars Society also has some suggestions how to build the greenhouse. Edison (talk) 00:21, 18 February 2010 (UTC)

As that Mars Society link says, you can keep it warm with what is essentially an enhanced greenhouse effect - they suggest a silver compound in the plastic that will allow visible light and near-IR (ie. sunlight) through but stop far-IR from getting out. --Tango (talk) 00:45, 18 February 2010 (UTC)

a little help with equilibrium constants and partition coefficients as they relate to solubility

Admittedly, the whole "mole product / mole reactant" thing goes over my head when I imagine scenarios like adding more reactant or taking away more product. So ... like take these titration results.

There's approx 0.013 mmol of dissolved iodine (without iodide) in 50 mL solution.

When I add 5 mL cyclohexane, approximately 0.008 mmol of it escapes into the cyclohexane, resulting in a concentration-in-cyclohexane figure of 0.0016 M. From the new concentrations I calculate a partition coefficient of approximately 16.

When I add 8 mL cyclohexane, despite a 60% increase in the amount of lipophilic solvent there's only a 25% increase in extraction ... Indeed, the concentration of iodine in cyclohexane is now 0.00125 M, a concentration fall. This sort of makes sense since as the iodine gets less-concentrated in the water phase, iodine becomes harder and harder to extract from aqueous solution. The concentration in aqueous phase is now 5.6 * 10^-5 M and the new partition coefficient is 22.

This is clearly experimental error right? Shouldn't the partition coefficients remain roughly the same? (We measured concentrations by titration.) Let's take an ideal case with no experimental error and say I'm adding more water or more cyclohexane. How would I use the partition coefficient to predict new concentrations? What does the partition coefficient really mean, as an equilibrium constant? How likely is it that mistitration or something like that is the source of my error? Basically, I don't know how to think of "mol product over mol reactant" when I say add more of one type of solvent to the mixture. Are the concentrations going to rearrange themselves such that the ratios of concentrations in the different solvents will somehow remain constant.

I get even more lost when I deal with saturated solutions and there's apparently an equilibrium constant between the pure solid phase and a dissolved phase as a solute, because if I add more excess solute to a saturated solution, clearly the ratios cannot adjust themselves to the equilibrium constant since the solution is already saturated. John Riemann Soong (talk) 01:34, 18 February 2010 (UTC)

To address your last question, you need to remember that the concentration of a pure solid substance (or even a pure phase of a liquid) has a constant concentration. TenOfAllTrades(talk) 04:03, 18 February 2010 (UTC)

Coming back to the first part of your question, what's the precision with which you're measuring the amount of iodine (to start with, and in each phase)? If that 0.008 mmol iodine is ± 0.001 mmol (for example), then what is the range of partition coefficients that you could calculate (based on 0.007 or 0.009 mmol in the cyclohexane phase)? TenOfAllTrades(talk) 13:38, 18 February 2010 (UTC)

Angular momentum in collisions

The angular momentum of any object can be divided into the angular momentum of it's center of mass, and it's angular momentum with respect to the center of mass. When analyzing collisions, the total angular momentum is said to be conserved. However, sometimes both the angular momentum of it's center of mass and it's angular momentum with respect to the center of mass are considered, but other times only the angular momentum with respect to the COM is used. Why would there be this discrepancy? And when finding the rotational kinetic energy, are both types of angular momentum used? Thanks. 173.179.59.66 (talk) 04:24, 18 February 2010 (UTC)

I think the OP really means ITS center of mass and ITS angular momentum, without apostrophes in the ITS. Cuddlyable3 (talk) 12:50, 18 February 2010 (UTC)

Angular momentum will be separately conserved around any point. Often you only need to consider it around one point to get the information you need. --Tango (talk) 18:02, 18 February 2010 (UTC)

I'm sorry, I don't see what mean... —Precedingunsigned comment added by 173.179.59.66 (talk) 20:38, 18 February 2010 (UTC)

Angular momentum around point P will be conserved and angular momentum around point Q will be conserved and around point R, etc. etc. You often only need to apply one of those conservation laws to get the answer you are looking for. Sometimes it will be easier to use P, sometimes Q. That's why you see different ones used in different problems - you just use whatever is easiest. --Tango (talk) 21:08, 18 February 2010 (UTC)

Hmmm, I guess my question wasn't well worded. Let's say two billiard balls are heading towards each other and collide (with some impact parameter). When doing all the calculations, the angular momentum due to their pure rotation (ie due to w=V/r) is used, while the angular momentum due to their net velocities are ignored. However, in a problem where a superball is bouncing off a wall, both the objects rotation and net velocity are taken into accound when detailing how the angular momentum is conserved. Why would we look at both in one, and only look at rotation in another? If I'm not being clear, let me know. Oh, and he talk about rotational kinetic energy, is it just equal to (1/2)I*w^2, or does the angular momentum of the center of mass need to be considered as well?

Ok, I don't understand that either. The rotation of an individual ball about its centre of mass won't be conserved during such a collision, because it isn't a closed system (the ball interacts with the other ball). --Tango (talk) 01:03, 19 February 2010 (UTC)

But if the rotation of one ball slows down, the other will speed up, keeping angular momentum conserved, right? —Preceding unsigned comment added by 173.179.59.66 (talk) 03:48, 19 February 2010 (UTC)

To be strictly correct, the 'orbital' angular momentum always should be included along with the 'rotational' angular momentum, but under certain circustances one or the other might be considered negligible.Dauto (talk) 15:40, 19 February 2010 (UTC)

Math in physics

Out of curiosity, do most physicists (outside of ultra theoretical fields like string theory) spend time manipulating equations and such by hand, or is basically all the math handled by computers. The reason I'm asking is that I'm sifting through a textbook on quantum mechanics, and it's evident that to make any progress, physicists back then had to be able to work out equations and model situations by pen and paper...is that still true today? —Preceding unsigned comment added by 173.179.59.66 (talk) 04:40, 18 February 2010 (UTC)

Yes, even experimental physicists still need to keep the pen and paper at arms length. But computers play a increasingly indispensable role on more advanced calculations. Dauto (talk) 05:04, 18 February 2010 (UTC)

To turn the (usually continuous) models of classical physics into discrete computer-solvable models which have the same properties as the original continuous model (conserved quantities, stability, ...) is mathematics in itself. In short: you need to use mathematics in order to get the computer to do the mathematics you want it to do. http://en.wikipedia.org/wiki/Numerical_methods —Preceding unsigned comment added by 157.193.173.205 (talk) 10:57, 18 February 2010 (UTC)

There is really three parts to this - there is the business of arithmetic - plugging actual numbers into the equations to get answers in practical, numeric form - and for that, a simple calculator will sometimes suffice - but computers are better for repetitive stuff. Another aspect is taking raw data and performing statistics or fitting equations to those numbers (for which computers are pretty indispensable). But the other part is in the development of the equations themselves. Computers are making inroads into that too - we have 'symbolic math' packages that can manipulate equations symbolically - but it still takes a human mind to spot some of the subtle changes that can change a sheet of paper covered with hieroglyphics into something small, elegant and memorable. SteveBaker (talk) 15:52, 18 February 2010 (UTC)

In my experience, "it depends whether the physicist knows how to tell a computer to solve their problem." That depends on the individual physicist's level of interest and formal training with computers. I hang around mostly with "numerical physicists", which is sort of techno-jargon for "computer programmer". The types of problems we know how to solve with computers reach pretty far and wide. Categorically, we use more computational power than a theoretical physicist. For example, this last week I have been solving the wave equation for residuals in a numerical inversion scheme. Now, when a theoretical physicist "solves the wave equation," they write down some variables on paper and call it "solved." When I "solve the wave equation," that means that I arrange the equation to the simplest form that I can use to represent. Then I formalize an algorithm, and write computer code to represent that scheme. When the computer "solves the wave equation," it reads input data, performs calculations on that data following my instructions (that hopefully represent some physical process), and spits out numerical output data representing a model of experimental observations. So in some sense, both me and the computer are doing math - but I save the redundant calculations for the computer, and the mathematical formalism for myself. We blur the line as far as where the mathematics is actually being "done," and me and my team of powerful computers really solve the wave equation together.

Obviously, the simplest case to consider is basic arithmetic. I'm mathematically inclined, but even I have limits - so when I need to determine a value like (36 + (50*2)/1024)/4, it's a waste of my time to do that in my head or on paper. A computer gives me the correct answer, the first time, as quickly as I can type that in. But in my brain, I have done math to estimate the acceptable range of answers I expect. In that case, the computer has pretty much done most of the math.

Non-arithmetic calculation is a little harder to type into a computer. If I want to know the instantaneous phase of a function or a scale-factor for a fourier transform, I often have to decide whether it's easier to use a symbolic algebra system, a numerical approximation, or a paper-based analytic solution. It depends on the problem. But I'm a physicist, not a "number-cruncher" - so it'd be a mischaracterization to say that I spend all day typing out equations and hitting "enter." So let me diverge a little and explain a bit about what a physicist like me actually does.

People come to physicists with quantitative problems that they would like to answer. In my particular field, they come to us with field-recorded geophysical survey data, and ask us to generate images of the Earth from it. We want to perform this process faster and better, creating clear pictures even if the source data is crappy. So, I look at the physics that represents the field-data collection; I model the physical phenomena, observe the effects of unknowns and interferences, and use those insights to design an algorithm to convert input data into output data, while preserving the physical constraints that we know apply.

I would categorize the design of algorithms as a subcategory of "mathematics." Now, whether we design a particular algorithm with a computer or not depends on its complexity. Having some training in formal software engineering, I find UML diagrams to be a great way to set forth a large numerical physics scheme - especially since I like modular code. So, I can use a CAD tool to help me draw out the mathematical operations I plan to do. But, I also keep a stack of blank paper at my desk to scratch work on - diagrams are easier drawn by hand than by mouse. When I have to do geometry, I do it on paper with a pencil. When I need the value of a tangent, I get that answer from a computer (or desk calculator). When I want to do a coordinate transform for an integral kernel, I often use a computer algebra system, but more often than not, I need to do it by hand anyway. In this way, I am "doing math" - I am applying the structure and formalism of analysis to solve a physics problem. The overwhelming majority of this stage of work is by hand and in my brain.

By the time I have formalized my problem, I inevitably write it out as a series of program statements, in the form of a standalone subroutine, a full-blown application program, or a short script for simple arithmetic - all depending on the scale of the problem. The repetitive calculations are performed by machine - and sometimes, intelligent mathematical decision-making is programmed in as well. I would say that almost everybody (physicist or not) knows how to perform arithmetic by computer; almost all physicists know how to perform algebra and calculus by computer; and many specialized physicists and mathematicians (and others) know how to perform matrix mathematics, optimization (mathematics), and so on.

One of the turning points in formal physics education is being able to distinguish the subtle, qualitative difference between "math" and "physics." In other words, when a physicist sees a new form of the wave equation, they aren't looking at the values of the constants - they're looking at the qualitative interactions and relationships between components. (Ask a real physicist whether Schroedinger's equation, which defines a wave-function, is actually a wave equation! The way they approach that question will astound you). And if you sit in on enough physics seminars, you'll inevitably hear some stodgy old guy grumbling something to the tune of "That's all great, but where's the physics!?" What they mean by this is that despite a load of impressive mathematical maneuvering or experimental observation, the presenter has not identified any qualitative physical principle. In the same way, when you ask whether a physicist manipulates math by hand or computer, they can really do either - whether their physics needs a numerical result will modulate the way that they interact with their computers. Nimur (talk) 22:35, 18 February 2010 (UTC)

Great, thanks for the detailed response. PS Is the Schroedinger's equation a wave equation? —Preceding unsigned comment added by 173.179.59.66 (talk) 00:03, 19 February 2010 (UTC)

Yes. See the article Schroedinger's equation. Please sign your posts. Cuddlyable3 (talk) 17:02, 19 February 2010 (UTC)

Actually it is a diffusion equation ([8], [9]), because the time derivative is first-order and complex (a complex parabolic partial differential equation); while a wave equation is a hyperbolic partial differential equation). Ultimately, you can define a "wave equation" a lot of ways - but most commonly, the defining factor is whether you can construct an invariant of the form (x_i +/- v*t) - in other words, propagation - which cannot be done for Schroedinger's equation! It's the defining state-equation for the wave function - but it is not a wave equation! To some extent, this is semantics and a matter of definition - but the idea is that we care about the physics that the mathematics represents - in other words, the algebraic term that represents wave propagation is decidedly absent in the Schroedinger solution. This means a lot of things - there is no effective velocity to propagate perturbations of the wave-function. This has implication to quantum entanglement, because in the absence of a term to define a velocity, technically there is no speed limit on the propagation of quantum information - hence the paradox of faster-than-light propagation of quantum entanglement information! So, by playing with the maths analytically, we can try to peel away at the actual physics implications. Nimur (talk) 18:14, 19 February 2010 (UTC)

Your explanation for quantum entanglement is fishy. The Schroedinger equation is a non-relativistic approximation. A fully relativistic wave equation such as the klein-gordon equation is a hyperbolic equation with a speed limit associated to it and yet(!) quantum entaglement exists. Dauto (talk) 05:07, 21 February 2010 (UTC)

Of course, there's always room for a more complicated model. Klein-Gordon_equation#Derivation explains the extension/conversion to the relativistic model. Anyway, I'm not really sure how to use the Klein-Gordon model, but as I understand it, it does not correctly solve for the observables in a simple case such as a hydrogen atom. It seems that the Klein-Gordon model only works for certain spinless particles, pions. (I really haven't ever used it). As far as I know, the Dirac Equation is the standard form, relativistic-corrected wavefunction equation for atomic physics - and it too is a diffusion equation. Nimur (talk) 06:13, 21 February 2010 (UTC)

Nuh-uh. Dirac's equation is not a parabolic equation. Don't let the first order time derivative fool you. Parabolic equations are second order differential equations while the Dirac's equation is a first order differential equation. It can be easily shown that every solution of the Dirac's equation also is a solution of a second order differential equation but it turns out to be a hyperbolic equation. That's not surprising at all because it is the limited speed characteristic of hyperbolic equations that make them consistent with relativistic speed limit. Schroedinger's equation is not a relativistic equation so it is free to violate that principle.

Starting with Dirac's equation

$\left(\beta mc^{2}-i\hbar \sum _{k=1}^{3}\alpha _{k}\nabla _{k}\,c\right)\psi (\mathbf {x} ,t)=i\hbar {\frac {\partial \psi (\mathbf {x} ,t)}{\partial t}}$

And making use of $\beta ^{2}=1\,$, $\{\alpha _{i},\alpha _{j}\}=2\delta _{ij}$, and $\{\alpha _{i},\beta \}=0$ we can find an expression for $(i\hbar )^{2}{\frac {\partial ^{2}\psi (\mathbf {x} ,t)}{\partial t^{2}}}$

$(i\hbar )^{2}{\frac {\partial ^{2}\psi (\mathbf {x} ,t)}{\partial t^{2}}}=(i\hbar ){\frac {\partial }{\partial t}}(i\hbar ){\frac {\partial \psi (\mathbf {x} ,t)}{\partial t}}=(i\hbar ){\frac {\partial }{\partial t}}\left(\beta mc^{2}-i\hbar \sum _{k=1}^{3}\alpha _{k}\nabla _{k}\,c\right)\psi (\mathbf {x} ,t)$

$=\left(\beta mc^{2}-i\hbar \sum _{k=1}^{3}\alpha _{k}\nabla _{k}\,c\right)(i\hbar ){\frac {\partial }{\partial t}}\psi (\mathbf {x} ,t)$

$=\left(\beta mc^{2}-i\hbar \sum _{k=1}^{3}\alpha _{k}\nabla _{k}\,c\right)\left(\beta mc^{2}-i\hbar \sum _{l=1}^{3}\alpha _{l}\nabla _{l}\,c\right)\psi (\mathbf {x} ,t)$

$=\left(\beta ^{2}m^{2}c^{4}-i\hbar \sum _{k=1}^{3}\{\alpha _{k},\beta \}\nabla _{k}m^{2}c^{3}+(-i\hbar )^{2}{\frac {1}{2}}\sum _{k=1}^{3}\sum _{l=1}^{3}\{\alpha _{k},\alpha _{l}\}\nabla _{k}\nabla _{l}c^{2}\right)\psi (\mathbf {x} ,t)$

$=\left(m^{2}c^{4}+(-i\hbar )^{2}\sum _{k=1}^{3}\sum _{l=1}^{3}\delta _{kl}\nabla _{k}\nabla _{l}c^{2}\right)\psi (\mathbf {x} ,t)$

$=\left(m^{2}c^{4}+(-i\hbar )^{2}c^{2}\nabla ^{2}\right)\psi (\mathbf {x} ,t)$

so

${\frac {1}{c^{2}}}{\frac {\partial ^{2}}{\partial t^{2}}}\psi -\nabla ^{2}\psi +{\frac {m^{2}c^{2}}{\hbar ^{2}}}\psi =0.$

Which is the Klein-Gordon equation!!

Dauto (talk) 22:21, 21 February 2010 (UTC)

Hydrogen bond position transition

I was trying to understand the File:Glycine-zwitterion-2D-skeletal.png variant of Glycine but then I realized that File:Glycerin Skelett.svg might be subject to the same hydrogen bond position transition.

What reasons are there to believe that glycerin hydrogen bonds are stationary? 99.60.3.241 (talk) 05:02, 18 February 2010 (UTC)

In glycine (the neutral form), there is an "acid" part (a hydrogen can be released easily) and a "base" part (has a high affinity for free hydrogen). Acids and bases react with each other pretty well, and the result is the zwitterionic form. Glycerin does not have any part that is particularly acidic or basic, so it does not change to an alternate hydrogen attachment pattern. DMacks (talk) 18:25, 18 February 2010 (UTC)

Black hole

Hello i have read article on black hole but i do not understand how in some documentary space time is shown to be warped so much that it is such one layer is underneath or over lap with another layer such that a large enough distortion of gravity though to another place in space time that is space can be warped by mass but how can it tunnel be created or what causes space to warp in such that the infinite steep sides of a black hole gravity impression comes out on space time instead of just going forever (Dr hursday (talk) 06:29, 18 February 2010 (UTC))

It sounds like an Einstein-Rosen bridge. Check out that article and see if it answers your questions.  :) Mac Davis (talk) 06:54, 18 February 2010 (UTC)

Hello yes this is what I am talking about but i do not understand how the "U" curve at the left of this picture http://en.wikipedia.org/wiki/File:Worm3.jpg occurs. what causes this? (Dr hursday (talk) 07:01, 18 February 2010 (UTC))

The U is only there because of the way the image is drawn. The same thing is happening in this image (imagine the plane "above" the wormhole extending on forever instead of only in two spots). The only difference is the way it was drawn. The U is there because two places in spacetime are connected by a jump through a higher dimension. If you were on any part of the "U" you would not notice any bends and it would appear perfectly "flat." Mac Davis (talk) 07:43, 18 February 2010 (UTC)

The "higher dimension" has no physical relevance, it may be useful to "visualize" the situation but it need not "exist" in any physical sense. The last paragraph in http://home.fnal.gov/~skent/cosmo/cosmo3.pdf makes this point too. —Preceding unsigned comment added by 157.193.173.205 (talk) 08:28, 18 February 2010 (UTC)

Strange bug

Omg what is this. Can someone tell me? --✶♏‭ݣ 06:31, 18 February 2010 (UTC)

Belostomatidae. -- kainaw™ 06:35, 18 February 2010 (UTC)

Ew ew ew. But thank you. Ew. *shudders* --✶♏‭ݣ 06:37, 18 February 2010 (UTC)

Sometimes fear of the unknown is the scariest thing of all!!! What the Jesus God Hell ever happened to curiosity. 86.4.186.107 (talk) 06:58, 18 February 2010 (UTC)

Given that the sting of the Belostomatidae is considered "one of the most painful that can be inflicted by any insect" and thus is beyond the highest on the Schmidt Sting Pain Index (which is limited to Hymenoptera) "4.0+ Bullet ant: Pure, intense, brilliant pain. Like fire-walking over flaming charcoal with a 3-inch rusty nail in your heel" perhaps Belostomatidae should be rated "5.0+ Jesus God Hell that hurts!" 58.147.58.28 (talk) 08:33, 18 February 2010 (UTC)

Why the profanity? Did your question get a better or quicker answer because of it? Just curious. Kingsfold (talk) 14:51, 18 February 2010 (UTC)

Did the profanity ofend you?Dauto (talk) 15:27, 18 February 2010 (UTC)

No. The answer was quick because all it took was a simple web search. Instead of trying to make a highly juvenile joke by seeing how profane I could be, I went to http://tineye.com and pasted in the URL of the photo. It showed multiple results. The second one was to a Russian site that had a link below the photo right back to the Wikipedia page for the bug. Then, all I had to do was put a link to the article here. I didn't complain because many people seem to prefer to ask questions instead of searching for themselves. -- kainaw™ 14:58, 18 February 2010 (UTC)

Thanks for that link. I didn't know that site. Dauto (talk) 15:27, 18 February 2010 (UTC)

There's a Firefox extension that lets you just right-click on an image and search for it in Tineye. Unfortunately, Tineye seems to have a very tiny index. I wish Google would just buy them and do it right. --Sean 16:10, 18 February 2010 (UTC)

I think it's obvious that the OP was humorously incorporating the sort of reaction one might make upon seeing this beast into his/her question. "Jesus", "God", and "Hell" seem pretty mild profanities for such a sight. --Sean 16:13, 18 February 2010 (UTC)

If you think that's bad, you should meet my Italian girlfriend. Imagine Reason (talk) 16:59, 18 February 2010 (UTC)

I hope you're talking about the use of colorful language and not about the Belostomatidae! (I also hope she doesn't read this page!) SteveBaker (talk) 20:17, 18 February 2010 (UTC)

I'll point out, just because nobody else yet has, that the stuff on the back is a mass of eggs. Looie496 (talk) 00:42, 19 February 2010 (UTC)

Although Ferrofluid smeared on the back of a magnetic beetle would appear similar. I have changed the question title for clearer reference. Cuddlyable3 (talk) 16:52, 19 February 2010 (UTC)

I agree with that but for clarification for any future readers, the profanity discussed above was largely in the title [10] Nil Einne (talk) 22:44, 19 February 2010 (UTC)

What would happen to photon

Hello if I shine a flash light out into space in such a direction that it never encounters anything what happens to the photon over time? (Dr hursday (talk) 06:55, 18 February 2010 (UTC))

It keeps going and will get redder due to the metric expansion of space according to Hubble's law. Mac Davis (talk) 07:20, 18 February 2010 (UTC)

If the photon gets redder where does the energy go? Ariel. (talk) 07:44, 18 February 2010 (UTC)

Nowhere. Hubble flow implies that the farther away one looks, the faster the local matter is moving away from you. By extension, if one travels to those distant places, then you have to subtract the effect of the average local velocity when considering your motion. Hence the farther the photon travels the more it will appear doppler shifted with respect to the local standard of rest. Dragons flight (talk) 08:15, 18 February 2010 (UTC)

You may be concerned that energy does not seem to be conserved in this scenario. That is correct. In general relativity, energy is not conserved. There's a new blog post at Cosmic Variance today explaining this. -- Coneslayer (talk) 17:21, 22 February 2010 (UTC)

Put another way, the photon appears redder because whoever is observing it happens to be moving away from us. Someone moving towards us would see a bluer photon. I think this effect is indistinguishable from that of the space itself between the objects having expanded.. EverGreg (talk) 09:22, 18 February 2010 (UTC)

It's not only indistinguishable. It is the same thing. Dauto (talk) 13:32, 18 February 2010 (UTC)

No. The redshift due to the expansion of space depends on how much space has expanded during the photon's free flight. The usual picture of this is that it's the light-wave that's stretched along with the space it travels in. These are distinctions with real consequences. Consider for instance that distant objects are more red-shifted than nearby ones, so their apparent speed is greater, but an object does not feel acceleration as it recedes from us in this way. Redshift due to expansion also allows an object to speed away from us faster than the speed of light, which is impossible with doppler shift. (Yeah, I read up on the redshift article :-P) EverGreg (talk) 19:32, 18 February 2010 (UTC)

This difference you are pointing out is just an illusion. All redshift derives from the same principle no matter whether it is a gravitational redshift, doppler redshift or cosmological expansion redshift. In fact those distinctions are not as relevant as they sound since what is a doppler redshift for an specific choice of coordinates will be a gravitational redshift for a different choice of coordinates and vice-versa. The cosmological expansion redshift is an artifact from our choice of coordinates. specifically our choice of using comoving coordinates. Dauto (talk) 20:49, 18 February 2010 (UTC)

You cannot do a Lorentz transformation such that an object is accelerating in one choice of coordinates but not in another. EverGreg (talk) 09:13, 19 February 2010 (UTC)

Yes, true but

• A) Lorentz transformations explain the bulk of the effect. See that[11] paper for an explanation on how to build an expanding universe without matter or cosmological constant.
• B) There is no reason to restrict yourself to Lorentz transformations - they do not hold any special status within General Relativity.

Dauto (talk) 15:21, 19 February 2010 (UTC)

All of this fancy color shift stuff only happens from the point of view of the observer at the source of the light. From the point of view of the photon - nothing whatever happens - it just keeps on going. If space is infinite (we're not 100% sure of that) then it'll keep going forever completely unchanged. If space is finite then perhaps it 'wraps around' and comes back towards you from the opposite direction - but it's still completely unchanged. Photons can't "degrade" over time because they are travelling at the speed of light - and for them, the whole of eternity passes by in zero time. If they don't hit something (which seems highly implausible), then nothing can change because for them, time isn't advancing at all. SteveBaker (talk) 15:43, 18 February 2010 (UTC)

If by "never encounters anything" you mean your beam of light misses large objects like stars, galaxies and space rocks, its fate will likely be extinction in the interstellar medium. --Sean 16:19, 18 February 2010 (UTC)

Perhaps its information content will be absorbed into the Omega point. Graeme Bartlett (talk) 03:24, 19 February 2010 (UTC)

OK, I know I'm an ignoranimus about physics, but the OP stated "it never encounters anything". If you observe it, hasn't it encountered something, namely your eyeball? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:40, 19 February 2010 (UTC)

Not sure, but I suspect all photons are only produced with a matching absorbtion elsewhere.114.75.18.3 (talk) 06:48, 19 February 2010 (UTC)

Not sure what that means. In any case, the earlier discussion seemed to be confusing photons with galaxies. Obviously, galaxies can produce gazillions of photons, and those photons can appear red or blue depending on whether the galaxy is approaching or receding. But talking about photons that way implies that photons are ejecting other photons that would be visible without seeing the original photon. Maybe I'm wrong, but I don't think it works that way. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:54, 19 February 2010 (UTC)

How much sodium in 1g of Baking powder?

How much sodium is there in 1g of baking powder, after it has been used to make a cake for example? Thanks 89.243.151.96 (talk) 14:50, 18 February 2010 (UTC)

this suggests that there are 520mg per teaspoon. (In that brand, anyway.) I don't know how many teaspoons are in a gram of baking powder, though. Sorry. APL (talk) 15:29, 18 February 2010 (UTC)

It says on your picture that 1/8 teaspoon = 0.6 grams, so about 1/5 teaspoon per gram. --Sean 16:24, 18 February 2010 (UTC)

Most baking powdersoda is "sodium hydrogen carbonate" which is NaHCO₃ - so there is one atom of sodium, one hydrogen, one carbon and three oxygen. You have to figure out the atomic weight of each atom - add them up and then you know the ratio of sodium to the rest of the elements. Then you can figure out the fraction of a gram that is sodium. According to List of elements: Roughly, Hydrogen is 1, Carbon is 12, Oxygen is 16 and Sodium is 23. So one molecule of this compound has a total atomic weight of 23+1+12+3x16 = 84. So for every 84 grams of baking soda, 23 grams is sodium which means that about 27.4% of this stuff is sodium. There is therefore 0.274g of sodium in every gram of sodium hydrogen carbonate - if your brand of baking powder mixes that with some other 'stuff' (which is possible, for example to stop it clumping) then the answer will be different - check on the ingredients list on the packet. SteveBaker (talk) 15:35, 18 February 2010 (UTC)

Steve, that's baking soda. Baking powder is different. -- Flyguy649 ^talk 15:50, 18 February 2010 (UTC)

Baking powder says "Most commercially-available baking powders are made up of an alkaline component (typically baking soda), one or more acid salts, and an inert starch". So I guess we need to account for the other stuff too. SteveBaker (talk) 17:22, 18 February 2010 (UTC)

(EC)It would depend on the brand. In addition to the sodium bicarbonate (baking soda) and acid, like cream of tartar, baking powders contain various amounts of cornstarch. The acids used seem mostly not to contain sodium. So the answer is in how much baking soda is in baking powder. While this article gives some suggestions on how to make your own baking powder, it uses teaspoon measurements (not weight) for the ingredients. That article gives ratios ranging from 1 1/4:1 to 2:1 cream of tartar:baking soda. You should be able to figure out a rough answer by using the densities of each reagent. -- Flyguy649 ^talk 15:42, 18 February 2010 (UTC)

(edit conflict) Baking powder will certainly be mixed with other stuff; that's what makes it different from baking soda. Most baking powder is sodium hydrogen carbonate as well as an acid, like cream of tartar or monocalcium phosphate. They also typically contain an inert filler, like cornstarch. Look on the ingredient label, for both the serving size (hopefully they give a value in grams) and the amount of sodium per serving. Divide the second by the first to find grams sodium (or probably milligrams sodium) per gram powder. Buddy431 (talk) 15:49, 18 February 2010 (UTC)

This particular brand, for example, appears to contain 65 mg of sodium per 0.6 g serving, which is 108 mg sodium per gram baking powder. Buddy431 (talk) 15:53, 18 February 2010 (UTC)

The brand in my kitchen (Magic baking powder)has 45 mg of sodium per 0.6g (1/8 tsp) serving or 75 mg per gram of baking powder. This plus Buddy431's contribution above shows that there is a huge variation by brand. -- Flyguy649 ^talk 15:59, 18 February 2010 (UTC)

Yes and given all this, I think it's clear that unless the OP provides the precise brand and name of baking powder, we can't answer the question. It would surely be easier for the OP to just look on the label which is probably on his/her product anyway Nil Einne (talk) 16:38, 18 February 2010 (UTC)

None of the brands of baking powder I have in my possession or have seen in supermarkets have mentioned how much sodium they have in them. I presume they are trying to hide that they have a lot. 89.243.197.22 (talk) 15:19, 21 February 2010 (UTC)

File:refraction.jpg

what should be the minimum distance of the sun from the horizon so as to enable the observer to see it's image? —Preceding unsigned comment added by 117.201.65.74 (talk) 16:37, 18 February 2010 (UTC)

I converted your header into a proper subject header with the image as a link Nil Einne (talk) 16:38, 18 February 2010 (UTC)

Even only a part of the Sun need be above the sea horizon for its image to be visible. Cuddlyable3 (talk) 16:47, 19 February 2010 (UTC)

Monarch Butterflies

Where do Monarch butterflies go in the winter? —Preceding unsigned comment added by Dredfern (talk • contribs) 17:10, 18 February 2010 (UTC)

They migrate. "The most famous Lepidopteran migration is that of the Monarch butterfly which migrates from southern Canada to wintering sites in central Mexico. In late winter/early spring, the adult monarchs leave the Transvolcanic mountain range in Mexico for a more northern climate. Mating occurs and the females begin seeking out milkweed to lay their eggs, usually first in northern Mexico and southern Texas. The caterpillars hatch and develop into adults that move north, where more offspring can go as far as Central Canada until next migratory cycle." --Mr.98 (talk) 17:19, 18 February 2010 (UTC)

Addiction

Hi,

I'm very worried. In fact I think I'm addicted. It's a highly dangerous drug; an overdose can lead to death and the substance constitutes 98% of all cancer cells. So, should I be going to Waterholics Anonymous? —Preceding unsigned comment added by 86.150.210.228 (talk) 18:04, 18 February 2010 (UTC)

It's not as funny if you call it water. Try Dihydrogen monoxide - that sounds really scary. --Tango (talk) 18:06, 18 February 2010 (UTC)

Oh my God, you're not inhaling it, are you? AlexHOUSE (talk) 18:54, 18 February 2010 (UTC)

Think this is bad? I'm far more concerned about oxygen being a mutagen. Regards, --—Cyclonenim | Chat  21:39, 18 February 2010 (UTC)

Ah, but the antidote is red wine - have enough of that, and you won't be concerned at all! --Tango (talk) 23:05, 18 February 2010 (UTC)

I hate wine. I'm f**ked, but I guess I could just start on those vitamins... Regards, --—Cyclonenim | Chat  23:52, 18 February 2010 (UTC)

Bear in mind the kind you take intravenously is usually cut with salt. AlmostReadytoFly (talk) 09:57, 19 February 2010 (UTC)

waters not a drug —Preceding unsigned comment added by 67.246.254.35 (talk) 05:56, 19 February 2010 (UTC)

Fish reproduce in it (as per W.C. Fields). ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:34, 19 February 2010 (UTC)

On the contrary, you could very broadly define water as a drug. It can alter bodily functions. If you're dehydrated, it's a drug which can relieve symptoms. Regards, --—Cyclonenim | Chat  11:28, 19 February 2010 (UTC)

Water intoxication is real. DMacks (talk) 11:38, 19 February 2010 (UTC)

Twin Cities

What is the most twin city to New Bedford, MA in Europe, geographically and climate-wise? Note I am not referring to sister cities. --Reticuli88 (talk) 18:49, 18 February 2010 (UTC)

The article about New Bedford does not give any info about its climate. I'm not sure if places having the same Hardiness zone would feel as if they had the same climate from a human point of view, since the seasonal daylight, summer temperatures, and rainfall may differ. What hardiness zone is it please? 92.24.96.55 (talk) 22:21, 18 February 2010 (UTC)

I think it is 6a. --Reticuli88 (talk) 22:51, 18 February 2010 (UTC)

Assuming New Bedford has a Hardiness Zone of 6 and a Heat Zone of 4, then the places listed in Europe with the same figures are Bratislava Slovakia, and Vienna Austria. They are both inland. Kaliningrad in Russia is more coastal, but it is only heat zone 2 and I think its latitude is higher so the seasonal daylight will be different. Do not know about the rainfall. 89.240.61.50 (talk) 23:51, 18 February 2010 (UTC)

Of course there is nothing close to a perfect match, but in terms of setting, population, and climate my choice would be La Rochelle, France. Looie496 (talk) 00:33, 19 February 2010 (UTC)

The climate would be much warmer in the winter than it would be in New Bedford, and probably cooler in summer. I assumed that the "geographical" similarity specified by the OP did not include population. 78.146.181.195 (talk) 00:49, 19 February 2010 (UTC)

Thanks everyone. Just wanted to know if I traveled to Europe today from New Bedford, MA, what city would seem like I never left MA - meaning the landscape (hills n such) and weather-wise. --Reticuli88 (talk) 13:20, 19 February 2010 (UTC)

WAG here, but maybe Sheffield? --TammyMoet (talk) 15:14, 19 February 2010 (UTC)

No, that would be one of the least similar places in all of Europe. 78.147.225.78 (talk) 20:36, 19 February 2010 (UTC)

If you are willing to accept somewhere with a warmer winter and a cooler summer then you have much more choice. With this in mind, if you want to limit yourself to Britain, then Nairn in Scotland would be a possibility, but with a smaller population. Inverness has a similar population. But even in Scotland, the urbanisation of the surrounding area is probably going to be much more than I expect it is around New Bedford. 78.147.225.78 (talk) 20:43, 19 February 2010 (UTC)

It's really unlikely that you'll find a place with similar weather in Europe. New Bedford has that vast continental landmass off to the west and only ocean to the east. Nowhere in Europe has that much continental mass behind it and such as there is tends to be to the east - not to the west. All of that results in very different climates in Europe and the USA. Also, the prevailing ocean currents are quite different. New Bedford gets the gulf stream bringing warm water up from the south. There isn't an equivalent thing in Europe. SteveBaker (talk) 01:01, 20 February 2010 (UTC)

I'm shocked - wernt you brought up in Britain? I thought every schoolboy knew about the Gulf Stream coming across the Atlantic and keeping Britain, plus Scandinavia and western Europe, much warmer than it would otherwise be for its latitude. When I was at school it was called the Gulf Stream, now people call it the North Atlantic Drift. Where the OP is does I believe have what meteorologists call a Continental climate, while Britain for example is a maritime climate (Oceanic climate) with less extremes of temperature. Given that climate difference, plus the different latitudes, and the far greater population density, makes it as people have said impossible to match. 78.149.241.220 (talk) 16:54, 20 February 2010 (UTC)

Not quite all true. As the Gulf Stream article to which you linked says, the Gulf Stream proper does indeed warm all of the USA's eastern seaboard, and the North Atlantic Drift is not a recent synonym for it, but an offshoot from it. 87.81.230.195 (talk) 00:40, 21 February 2010 (UTC)

You've got the wrong end of the stick. I was referring to the North Atlantic Drift which was, in a classroom in the UK many years ago, referred to as the Gulf Stream. 78.146.167.216 (talk) 01:44, 21 February 2010 (UTC)

Freezing Point Depression and Boiling Point Elevation

After reading one of the above posts I came across this picture. I understand what the unbroken segments of the lines are. But how can one understand the dashed segments of the lines? For example on the right hand side of where the black "solid" line crosses the dark blue "Liquid (pure solution)" line? •• Fly by Night (talk) 22:55, 18 February 2010 (UTC)

It appears that the dashed lines are merely the continuation of the trends for the chemical potential versus temperature. That is, if the solid didn't melt at its melting point, its chemical potential vs. temperature curve would follow the dashed black line. I guess that the dashed lines are just in there to make the intersections more clear. Buddy431 (talk) 04:49, 19 February 2010 (UTC)

February 19

Altered taste buds after toothbrushing

Why does milk and orange juice taste so terrible after brushing? --70.167.58.6 (talk) 02:56, 19 February 2010 (UTC)

The Sodium lauryl sulfate in the toothpaste supresses the "sweetness" sensors in your tongue and decomposes phospholipids which normally inhibit your "sour" tastebuds. Net result, the usually sweet and subtly tart orange flavor becomes totally unsweet and super-sour. I don't know why milk would taste bad - I wasn't really aware that it did...but if you're right then it's probably the same kind of reason. SteveBaker (talk) 03:08, 19 February 2010 (UTC)

You can buy toothpaste without the Sodium laureth sulfate foaming agent. EDIT, Sodium lauryl sulfate is different to Sodium laureth sulfate and probably not found in many toothpastes... 188.221.55.165 (talk) 13:38, 19 February 2010 (UTC)

That makes me wonder... on a similar topic... Is there a toothpaste that enhances taste of "healthy" food? For example, they could throw some miracle fruit juice in the toothpaste. -- kainaw™ 04:21, 19 February 2010 (UTC)

You're supposed to brush after you eat, not vice-versa. APL (talk) 05:51, 19 February 2010 (UTC)

That supposes the purpose is to remove food particles. Ew. I brush before breakfast to remove the layer of plaque that builds up overnight, so the sugars in my breakfast have nothing to stick to. If I were brushing after eating, I would wait half an hour to allow my mouth pH to return to normal, as otherwise the teeth are softer and you can end up (over cumulative brushings over the course the years) thinning them, gradually brushing off the hard layer. Since I don't have half an hour to spare after breakfast, and the thought of brushing bits of food out in the froth makes me gag, I brush before eating. 86.182.38.255 (talk) 15:56, 19 February 2010 (UTC)

Hmm... That's pretty complicated. I had no idea that by skipping breakfast I was saving myself so much mental effort. APL (talk) 18:17, 19 February 2010 (UTC)

We're on the Science desk, and you think that's complicated? Maybe I should have just said "You're supposed to brush before you eat, not vice-versa." as if I had access to some ultimate truth, then left people to suppose that it is only cultural with no advantages or disadvantages either way. 86.176.185.157 (talk) 12:40, 20 February 2010 (UTC)

Toothpaste that enhances the taste of "healthy" food is called mayonnaise. --Dr Dima (talk) 10:06, 19 February 2010 (UTC)

Whether teeth are brushed before or after breakfast depends primarily on a cultural difference. And not eating breakfast simply makes one fat. ~AH1^(TCU) 00:01, 20 February 2010 (UTC)

In concert with Steve's response above, orange juice contains sugars as well as naringin, a bitter component of the peel and other parts of the orange. After sodium lauryl sulfate (essentially a detergent) destroys one's sweet-detecting taste cells, the only taste of the orange juice that can be detected is the bitter naringin. DRosenbach ^{(Talk | Contribs)} 13:56, 19 February 2010 (UTC)

"destroys" is a rather strong term for what this detergent does. It doesn't damage the cells - it merely inhibits them in some way. If it destroyed them it would be days to weeks before you'd get your sweet taste sense back rather than tens of minutes. SteveBaker (talk) 00:57, 20 February 2010 (UTC)

Integrating Partition Functions

When computing the partition function or doing other such calculations in statistical thermodynamics, one needs to sum (integrate) over all the possible microstates. How do you determine the appropriate variable over which to do the integration? An example to clarify: if one of the degrees of freedom of your system is a rotation around a molecule's bond, one possibility is to integrate over the dihedral angle. However, that degree of freedom can be quantified by any number of other equivalent formulations (e.g. something based on, say, the dot-product of the normal of the plane containing atoms A-B-C and that containing B-C-D). How can we tell what's the appropriate variable to use in the integration, and what is the property of that measure that makes it the appropriate one to use? -- 174.21.247.23 (talk) 04:20, 19 February 2010 (UTC)

For the outcome, it doesn't matter which representation you choose; all of them are quevalent by definition. Of course, choosing a different representation can make the integral easier to solve. But there no general rules which one to choose. --baszoetekouw (talk) 10:05, 19 February 2010 (UTC)

I believe it does matter which one you choose. I'll give an example: You have two different way to parametrize a single degree of freedom, x and α, related by the expression α = x², each of which varies between 0 and 1. Say your energy function is E = (1 - x²)/β = (1 - α)/β. The two different formulations for the partition function give

$Z(x)=\int _{0}^{1}\!e^{-\beta E(x)}\,dx=\int _{0}^{1}\!e^{-(1-x^{2})}\,dx\approx 0.538,$

$Z(\alpha )=\int _{0}^{1}\!e^{-\beta E(\alpha )}\,d\alpha =\int _{0}^{1}\!e^{-(1-\alpha )}\,d\alpha \approx 0.632,$

So in this case (and I believe most other cases, especially when the two are not linearly related) the two formulations do not give equivalent results. My question was, how do I know which formulation is the correct one to use? That is, which is the "natural" variable over which to do the integration, and how do we know which one it is? -- 174.21.247.23 (talk) 16:41, 19 February 2010 (UTC)

In general, the correct way of looking at the problem is actually:

$Z(x)=\int \!e^{-\beta E(x)}\rho (x)\,dx$

Where ρ(x) is the density of states in the neighborhood of x. For many practical problems, we tend to engineer the variable of integration such that ρ(x) = 1. In a sense that gives you a preferred choice for the variable of integration, but it is not a required choice. In particular, one can change as in a regular integration be realizing that ${\rho (x) \over \rho (\alpha )}={\partial \alpha \over \partial x}$.

By definition, each set of allowed quantum numbers will contribute exactly one term to the partition function sum. In general, this means one can find the ρ(x) = 1 formulation by starting with an explicit sum (or often a multiple sum, with one sum for each quantum number), and then when one extends it into the continuum limit the integrand for ρ(x) = 1 will have the same form as your summand. I'd suggest that a large part of the problem you are having in deciding how to do the integration is that you probably haven't figured out how your system is quantized. Being able to enumerate the quantum states is a necessary precondition to writing out a partition function. Dragons flight (talk) 18:12, 19 February 2010 (UTC)

How does one go about the quantum to classical conversion for complex systems such as large molecules? Going back to my original example of a rotation around a bond, is there a straight-forward way of determining how ρ(x) is constructed? "Enumerating quantum states" is all well and good for something like ethane, but for larger systems like erythromycin (or erythropoietin) it begins to break down. -- 174.21.247.23 (talk) 04:48, 20 February 2010 (UTC)

transformers

i was reading about transformers and came to know that it can easily defy ohm's law ie "V is directly proportional to I". i have a QUESTION what will happen if a appliances is rated to be used at 220V, and let us assume it needs 10A-- is given 220V and 5A? will it work perfectly or just slowly? since no appliance is rated abot current i am unable to conclude any thing. { we got a source of 110V and 10A, using a step up transformer we get 220V and 5A } <<<a request please dont start asking ur questions in this page, many a times it had happened to me, my question is interrupted by someone else>>>--Myownid420 (talk) 07:40, 19 February 2010 (UTC)

You'll blow a fuse. The current-rating on an appliance says how much current it takes at the given voltage. That is, if you push with a certain force (voltage), that's how much/rapidly the electricity flows (current) through its inner workings (consider Ohm's Law for the fixed resistance of the appliance). Your circuit is pushing with a certain force, which will cause that amount of current to flow. But your circuit is limited to supplying less than that. So either there is not enough energy in the appliance for it to do [whatever], and the failure will depend on how it uses the energy, or else your circuit will try to keep up with the flow the appliance is using, and overheat. Current output is a maximum-available, not a constant amount--as you draw more on the transformer secondary, the primary draws more from the mains. If you do not connect the secondary to anything, the primary is drawing nearly zero, not "the rated supply current". DMacks (talk) 08:08, 19 February 2010 (UTC)

Usually the voltage V and power P in watts are specified for a mains appliance. Given these two it is unnecessary to specify the current I in amps because I=P/V. The supply is just a voltage, such as 220V or 110V. The current depends (mostly) on the resistance R of the appliance. Here Ohm's law I=V/R is useful. With one proviso, any appliance rated for 220V can be connected to any 220V supply and any appliance rated for 110V can be connected to any 110V supply. The proviso is that the supply is able to deliver the current the appliance demands because if not, something in the supply will burn up, hopefully just a fuse. Your step-up transformer will work if it has high enough power rating (watts) for the appliance. Thank you for your question which was clearly written. Sometimes we need to ask questions to help us give better answers. Cuddlyable3 (talk) 16:21, 19 February 2010 (UTC)

Transformers are generally given a primary and secondary voltage rating and an amp or voltampere rating on the secondary side. They have some internal impedance to the flow of electricity,so if no current flows to the load, the secondary voltage may be higher than nominal. If more than the specified current is drawn out, the secondary voltage may drop lower than specified. How much current is drawn out of the secondary is up to the connected load, not to the transformer. It is not a pump of electricity. Under a very high load or a dead short, the current flow would be limited mostly by the transformer impedance (and to a slight extent by the impedance of the source feeding the primary) and the transformer might overheat and fail if a primary or secondary fuse or breaker did not blow. The primary fusing often is just to protect against a short in the transformer, and would let the transformer continue feeding a short on the secondary for a long time. I have seen 12kv primary, 480v secondary transformers continue to feed an arcing short on the secondary for over a half hour, providing enough energy to incinerate a metal enclosed switchgear. Edison (talk) 03:18, 20 February 2010 (UTC)

And, of course, your appliance may be fibbing. It may only draw 2 amps in normal operation. But talking about a household power supply: if you plug in a nice simple appliance, say a 220V 10A kettle, into a 110V supply via an appropriate transformer you would either trip a circuit breaker or melt something - hopefully a fuse. --203.22.236.14 (talk) 11:07, 21 February 2010 (UTC)

washingg labware

how is labware like beakers washed when it had strong acids like 100 % hydrofluoric acid —Preceding unsigned comment added by 67.246.254.35 (talk) 11:14, 19 February 2010 (UTC)

also eye dropers —Preceding unsigned comment added by 67.246.254.35 (talk) 11:20, 19 February 2010 (UTC)

A glass beaker would not contain 100% hydrofluoric acid for at least two reasons. DMacks (talk) 11:36, 19 February 2010 (UTC)

At least, not for long! One of my lecturers used a dilute HF solution when he was washing out all his glassware as an undergrad back in the day just to get the stubborn marks off. I don't think you could get away with that now. Also, for 67: I can't see why you'd use any special procedures; several water rinses then a squirt of acetone would probably do it. Brammers (talk) 14:24, 19 February 2010 (UTC) (Edited 14:26, 19 February 2010 (UTC))

No, first you have to safely neutralize the remaining HF. HF is only handled in fume hoods nowadays but you would wash it 3 times with dilute basic solution and store that in a waste acid container. Then you would wash with polar and nonpolar solvents and scrubbrush depending on what you were cleaning and store that rinsate in a organic (or solvent) waste container. Then you would wash with water (which rinsate may need to be stored in an aqueous waste container). Finally (at least in my college research lab) a 24-hour bath in dilute acid, followed by a 24-hour bath in dilute base, then overnight in a drying oven and you're done. Unless you are doing anayltical chemistry where you may then need to wash it three times in triple distilled dionized water before drying it. (Ah, the memories of washing dishes. The only time I have ever needed to use a fire extinguisher.) 75.41.110.200 (talk) 15:26, 19 February 2010 (UTC)

If you have an acid-waste container, then put your acid waste in it and let the waste-collection folks handle that. Few quick rinses with then water, and you're done. Well you were done long ago, because the HF (which cannot be made 100% in a beaker) would have dissolved the glass away. If poured out promptly, the HF would have merely etched the glass to become fluorosilicic acid, one of the fluorinating agents used in public water supplies. Repeated acid and base washes are waaaay overkill unless you actually need something that really clean. And anyway unless you use deionized water you're still going to bake out a bunch of ions and get an unpredictably-reactive glass surface, but for many purposes, it doesn't matter--triple-water-rinse and it's clean enough for non-analytical/non-biochemical purposes. Organic chemists just use a squirt of acetone and say "good enough":) A totally impossible scenario without detail/context, no way to know "how clean" the glass needs to be. DMacks (talk) 18:38, 19 February 2010 (UTC)

Ah right, thanks for the insight. The organic labs are the only ones where we have to wash our own glassware, so I'd assumed the acetone squirt was standard practice. Brammers (talk) 01:35, 20 February 2010 (UTC)

I loved lab sinks with a ring of Litmus paper around the drain. Edison (talk) 03:20, 20 February 2010 (UTC)

Years ago I heard a chemical-safety talk, involving the usual "nothing non-neutral down the drain, our waste-stream is monitored for pH outside a narrow range". Talked all about how one night there was a acidic spike, as usual blame went to the chem labs, rather than the cafeteria kitchen where someone had actually just poured out a bottle of vinegar, but the overall campus flow was low enough that it didn't get diluted to the legal level. DMacks (talk) 06:32, 21 February 2010 (UTC)

Apollo Missions

I think I have a decent grasp of most of the stages involved in the Apollo missions. However what I don't get is how NASA was so confident they could dock the orbiter and the lander AFTER the surface mission. To properly dock two untested components (how could they really test docking in lunar orbit?) seems like a major challenge. How did they know they wouldn't be stuck with two vehicles in non-intersecting orbits? TheFutureAwaits (talk) 11:59, 19 February 2010 (UTC)

Well, it's mostly just "docking in orbit" -- "docking in lunar orbit" adds no particular degree of difficulty. NASA had already done considerable work in Earth orbit to verify rendezvous launches (see Gemini 6 and Gemini 7) as well as Apollo CM/LM docking tests (see Apollo 9 and Apollo 10, the latter conducting lunar orbit operations). So, the vehicles weren't untested, and they'd verified that they could do the math to avoid non-intersecting orbits. — Lomn 12:32, 19 February 2010 (UTC)

By the time of Apollo 11, it was fully tested because Apollo 10 had done exactly the same thing, just without having actually set down on the moon inbetween. I guess Apollo 10 were taking a bit of a risk, but the Apollo programme accepted a significantly higher level of risk than modern space programmes. --Tango (talk) 12:34, 19 February 2010 (UTC)

Apollo 9 tested the lunar module in Earth orbit, flying more than 100 miles from the command module before separating from the descent stage and returning to dock. I assume that they limited the delta-V so that had the lunar module failed at any point, the command module could have caught up with it for docking. So, while these missions did take big steps, it was not done all in a single step. 58.147.58.28 (talk) 13:47, 19 February 2010 (UTC)

I have always assumed that NASA had planned for the contingency of the loss of the descent crew, either due to a crash of the LEM during descent or a failure of the ascent module, but I've never heard it specifically said that the command module pilot would have been able to execute the return to Earth single handed. (I suppose that it was done in Shane Johnson's Christian science fiction novel Ice, but I don't recall him discussing the logistics of the return.) 58.147.58.28 (talk) 13:47, 19 February 2010 (UTC)

Yes, the CM pilot could have returned home on his own. I can't find a reference for that at the moment, but I do remember reading it. I don't know quite how it would work, perhaps ground control would do some of the work remotely. --Tango (talk) 14:24, 19 February 2010 (UTC)

Considering that they had a planned presidential speech in case Neil Armstrong and Edwin Aldrin died [12], I expect they would have had a detailed procedure to bring Collins back. 75.41.110.200 (talk) 15:12, 19 February 2010 (UTC)

Cause of Menopause

Does meno pause happen because of running out of eggs in the avaries, or is there something else that causes it. In that case. are there eggs left over? —Preceding unsigned comment added by 79.76.254.35 (talk) 13:53, 19 February 2010 (UTC)

There are millions of eggs, so that's not the problem. This seems to indicate that you are correct (check out the last paragraph)...but biology class has always taught that this is not true. It's a reflection of lowered hormone production, specifically estrogen and progesterone. You can check out the article on menopause for more information. DRosenbach ^{(Talk | Contribs)} 13:58, 19 February 2010 (UTC)

Running out of eggs in aviaries usually results in a lack of birds! --TammyMoet (talk) 15:12, 19 February 2010 (UTC)

Simply put. The eggs in the women cycle not only contains the gonades, but they also end up producing hormones, (which explains the hormonal variation, most of the time a single at a time, the same one which migrate waiting to be fecunded). That's controled by the putiary gland. During menopause there are no eggs left. That's quite different than the production of androgenes by the testicules and that's why male adropause is more gradual. -RobertMel (talk) 17:14, 19 February 2010 (UTC)

This question is tantamount to asking why people age or die. It's a long story! Vranak (talk) 17:31, 19 February 2010 (UTC)

No actualy, it is not. Menopause is due to no eggs left to produce female hormones and the surrenals conversion of DHEA does not suffice to replace that loss. It's really that simple. -RobertMel (talk) 17:35, 19 February 2010 (UTC)

Symptoms of a higher-level process. Vranak (talk) 19:07, 19 February 2010 (UTC)

Menopause simply means the cessation of menstruation as there is no eggs left which will be answering to LH and FSH. It's really not that long as a story, really. Menopause can be induced by simply removing the ovaries, because you get rid of the eggs all at once. What it means to be old? The question is much more complex. -RobertMel (talk) 19:31, 19 February 2010 (UTC)

~Shakes head~ I think we are at loggerheads here. Vranak (talk) 04:08, 20 February 2010 (UTC)

Im still not clear of the answer to my question. Can someone simplify the answers? —Preceding unsigned comment added by 79.76.244.151 (talk) 10:56, 20 February 2010 (UTC)

Okay - first thing to be clear about is that the ovaries do not contain a supply of mature eggs - they contain immature egg cells called primary oocytes. The supply of immature egg cells in the ovaries is fixed during embryonic development, well before birth - see oogenesis. There are far more than a woman will need in her reproductive span - the ovaries contain around two million immature egg cells at birth, but only around 400 of these will become mature egg cells and be released from the ovaries in ovulation - see folliculogenesis. The remainder die off over time in a continuous process called ovarian follicle atresia. The development of a small proportion of immature egg cells into mature egg cells is triggered by a set of interacting hormones, one of which is follicle-stimulating hormone or FSH. As a woman approaches menopause, her immature egg cells become less sensitive to FSH, ovulation becomes less regular, and eventually stops altogether. At menopause, FSH is still produced (in fact, post-menopausal women have higher levels of FSH than pre-menopausal women, because one of the side-effects of ovulation is to inhibit the production of FSH) and the ovaries still contain immature egg cells at menopuase - up to 10,000 according to this source. The cause of menopause is that the remaining immature egg cells in the ovaries have become insensitive to FSH. Gandalf61 (talk) 13:27, 20 February 2010 (UTC)

Thanks that makes sense. But what causes the immature eggs to become less responsive to FSH? —Preceding unsigned comment added by 79.76.132.10 (talk) 23:47, 20 February 2010 (UTC)

It is assumed by many that only those which are not responsive to begin with are left. -RobertMel (talk) 00:18, 21 February 2010 (UTC)

Assumed by who, exactly ? Do you have a source for that ? The development of immature egg cells into mature egg cells is a long and complex process that takes thirteen menstrual cycles altogether. At the start of this process, many immature egg cells start responding to FSH and developing. Most die along the way. At the start of the follicular phase between five and seven developing egg cells and surrounding structures (called tertiary stage ovarian follicles) continue their development, but normally only one - the dominant follicle - completes this development and is released in ovulation. Sometimes two mature egg cells may be released in ovulation. Or sometimes no dominant follicle emerges, and the process starts over again with another group of tertiary follicles - this is why the follicular phase is variable in length. The response of immature egg cells to FSH and other hormones is not a simple on/off switch. Gandalf61 (talk) 10:48, 21 February 2010 (UTC)

You are not contradicting me here. I was getting to egg selections. Unlike male who produce billions and only the strongests get to achieve their destination, women complete this selection starting with a prederminated number of immature eggs. At the end, either the remainings aged too much or only bad ones in the first place. They can now predict the age of menopause based on the size of the ovaries, which assume the reserves. -RobertMel (talk) 16:17, 21 February 2010 (UTC)

Really ?? I can only find one study (Wallace & Kelsey, 2004) that suggests that ovarian volume is an accurate predictor of the onset of menopause in an individual woman (as opposed to a general statistical correlation), and a lot of commentary (here for example) that says that this method is based on faulty assumptions and has not been clinically proven. Gandalf61 (talk) 18:15, 21 February 2010 (UTC)

Are kale stems edible?

All my kale was infested by Whitefly, they only spared the stems. Are they edible, and would they need special treatment before eating? 95.115.163.171 (talk) 14:17, 19 February 2010 (UTC)

I'm pretty sure I've eaten kale stems. It's just a variety of cabbage. --Tango (talk) 14:26, 19 February 2010 (UTC)

Yes: raw or boiled. Bit woody either way if the plants are too old. A related question if anyone knows is whether Vitamin K is uniformed distributed between stalk and leaves for plants such as this, or broccoli. Anyone know? I happen to be very fond of the crudity made from the centre of a broccoli stalk and have to watch Vitamin K intake. --BozMo talk 18:14, 19 February 2010 (UTC)

Sorry to be picky, but I think it's crudité 86.4.186.107 (talk) 19:12, 19 February 2010 (UTC)

Crudity means crudeness. --Tango (talk) 20:59, 19 February 2010 (UTC)

If the stem is edible and spared by pests, is there any cultivar with thick and not-so-woody stems? 95.115.163.171 (talk) 22:46, 19 February 2010 (UTC)

Hmmm. I just read that Kale -like Broccoli, Cabbage, Brussels Sprouts, and Cauliflower- is derived from wild mustard by means of artificial selection. on a side note, why are you interested in maggot-infested stems? just go to the market and purchase some new Kale, no?Chrisbystereo (talk) 14:47, 20 February 2010 (UTC)

Who said they were maggot-infested? The OP probably doesn't want to waste the food they have grown if they don't have to. --Tango (talk) 15:48, 20 February 2010 (UTC)

That's right. Actually I (the OP) discarded leaves and stems already last year. I am not in a situation where I need to do "original research" on what might be edible. But 1.) I'm curious, 2.) times may change, and 3.) I don't want to deliberately waste food, for ethical reasons as well as for plain stinginess. 93.132.156.86 (talk) 17:54, 20 February 2010 (UTC)

H₂O a covalent compound

why ionic compounds dissolve in covalent compound water(H₂O)? how does a covalent compound sugar(C₆H₁₂O₆)dissolves in water and not a oil?is it necessary for all ionic compounds to be soluble in water. —Preceding unsigned comment added by Myownid420 (talk • contribs) 16:27, 19 February 2010 (UTC)

The bond in H₂O is a polar covalent bond which means it can be considered partially ionic. Read ionic bond#Ionic versus covalent bonds for a brief explanation. It is the polarity of the compound that matters when figuring out whether it is water soluble or not. Dauto (talk) 16:41, 19 February 2010 (UTC)

Rings around Earth

This video was very interesting however I wonder if earth would be different or possible for life to happen on earth if it had this. Does it matter what the rings would be made of or the size? --Reticuli88 (talk) 16:54, 19 February 2010 (UTC)

Not an answer but a further question: how do we go about building those way cool rings? Maybe even temporary ones, say, from water ice that will deorbit in a few decades -- how many kg of water? Launch cost in USD? (Yeah yeah, astronomers will complain about light pollution; we'll just ignore you.) 88.112.56.9 (talk) 17:21, 19 February 2010 (UTC)

To answer the cost question, a general estimate is that it costs $10,000/lb (roughly $20,000/kg) to get something into LEO. It would likely take many, many thousands or millions of tons of material in order to crate planetary rings. The more spectacular, the more material you probably need. So I estimate cost on a bare minimum guess of $2 trillion for a measly 100,000 tons of material. Keep in mind that is only 100,000 cubic meters of ice (approximately) so it would be spread pretty thin. Also, the people who have satellites might not like you if you did this. Googlemeister (talk) 17:40, 19 February 2010 (UTC)

How will the water de-orbit? --Reticuli88 (talk) 19:09, 19 February 2010 (UTC)

There's still plenty of atmospheric drag in low Earth orbit, and ice chunks have no fuel to counteract that. — Lomn 20:01, 19 February 2010 (UTC)

To answer the original question. The rings would have no ill effect whatsoever for life on earth. Dauto (talk) 20:51, 19 February 2010 (UTC)

I don't know about that - the shadow the rings cast across the planet could have some effect. It wouldn't prevent life from forming, but it might be a little different (in the appropriate region, anyway). --Tango (talk) 20:57, 19 February 2010 (UTC)

The amount of light blocked by the rings is negligible. Dauto (talk) 21:42, 19 February 2010 (UTC)

OK, our rings of saturn page says 5 to 12% gets blocked so not completely negligible but too small to cause any direct ill effect. Dauto (talk) 22:26, 19 February 2010 (UTC)

That's just the C ring (and is unreferenced), which is described as "faint". Presumably the darker rings block more. --Tango (talk) 22:44, 19 February 2010 (UTC)

Dauto, your claims in this thread are really sloppy. Can you provide references for your extravagant claims that there would be "no ill effect whatsoever" and "too small to cause any direct ill effect"? You're aware, aren't you, about possible tipping points, and that any weather system is so chaotic that you can't possibly predict the consequences of changes? 63.164.47.229 (talk) 23:12, 19 February 2010 (UTC)

Yeah, but who said anything about no changes? I said there would be no ill effect. Earth might become cooler by several degrees due to the rings and life would adapt the same it adapted to the last several glacial maxima. Note that the question is about whether life on earth would be possible at all. Dauto (talk) 23:40, 19 February 2010 (UTC)

That life would eventually adapt is a given - but if the rings formed quickly enough then there might not be time for that. Assuming Saturn's rings for a model (not necessarily a valid thing - but let's go with it), the rings block sunlight for half of the year and enhance it for the other half. That results in hotter summers and cooler winters. How much that blocking might be is tough to guess - because we don't have a solid description of how thick or how wide these rings are. Judging by the density of the shadow cast by the Saturnian ring system, it's certainly not negligable. We could certainly imagine more pronounced weather at the edges of the ring shadow where the temperature contrasts are strongest. The complexity of the changes caused by such rings are hard to unravel. So I'm sure Dauto's statement is too strong. This is a "Don't know" kind of a question.

It's worth mentioning that according to the Giant impact hypothesis the Earth did once have rings - shortly after the Mars-sized object sometimes known as "Theia" smacked into the young Earth there would have been some pretty impressive rings - much of which eventually formed the Moon - with the remainder falling back to Earth eventually. SteveBaker (talk) 00:50, 20 February 2010 (UTC)

I stand by what I said. I few rings around the earth wouldn't prevent life on earth. Life survived more extreme events in the past such as the K-T event. Dauto (talk) 01:11, 20 February 2010 (UTC)

But you went way further than that, and claimed there would be no ill effect whatsoever, which you could not possibly predict or know for sure. Being a little less sure of yourself in such answers would suit you. 63.164.47.229 (talk) 01:50, 20 February 2010 (UTC)

Rings in orbit really wouldn't hurt life on earth. They might make a few things a little different but still suitable for life. Hence no ill effect. Dauto (talk) 02:38, 20 February 2010 (UTC)

Butterfly effect. Too chaotic to predict what changes would occur, good or ill. Ks0stm ^(T•C•G) 03:08, 20 February 2010 (UTC)

The butterfly effect doesn't make it impossible to make predictions. For instance, I predict that six months from now it will be warmer in New York City than it is today. Dauto (talk) 03:17, 20 February 2010 (UTC)

Sure, you can predict that, but it is far from certain to be true. If you average the temperature over a month, it becomes a safer prediction. --Tango (talk) 13:11, 20 February 2010 (UTC)

Perhaps our problem is with the definition of "ill effect". Determining whether an effect is ill or not is very subjective. The only effect on life that is unquestionably ill is life being entirely wiped out, and I think we're all agreed that wouldn't happen. However, there are other effects that are possible which could be considered ill - some species going extinct, for example. --Tango (talk) 13:11, 20 February 2010 (UTC)

Always radioactive?

Are all chemical compounds of radioactive chemical elements radioactive? --88.76.18.70 (talk) 16:56, 19 February 2010 (UTC)

Simply put, chemical compounds concerns the electrons, radioactivity concerns the nucleus of the atom. So no matter the lenght of the chemical compound, as long as it contains radioactive elements, it is radioactive. -RobertMel (talk) 17:06, 19 February 2010 (UTC)

Maybe slightly off-topic, but it might be worth mentioning water vs. heavy water as an example of a compound whose chemical properties do depend appreciably on the nuclei of the constituent atoms. —Preceding unsigned comment added by 83.134.169.7 (talk) 10:01, 21 February 2010 (UTC)

Are there any radioactive chemical compounds which don't contain any radioactive atoms? --88.76.18.70 (talk) 18:08, 19 February 2010 (UTC)

No. -- Flyguy649 ^talk 18:10, 19 February 2010 (UTC)

I think the variations on what you are looking for in a single type of atom are called isotopes. ~AH1^(TCU) 23:41, 19 February 2010 (UTC)

February 20

star size limits

is there a limit for stars to grow before nuclear reaction is not enough to prevent them from collapse do to gravity —Preceding unsigned comment added by 161.184.96.146 (talk) 12:52, 20 February 2010 (UTC)

Yes. See Star#Mass and Eddington luminosity. I believe what the limit actually is depends on the metallicity of the star (which depends, among other things, on how old the universe was when the star was created). --Tango (talk) 13:06, 20 February 2010 (UTC)

For interest, last week's New Scientist magazine (dated 13 Feb 2010) had a cover-featured article [13] examining exactly this topic. 87.81.230.195 (talk) 16:30, 20 February 2010 (UTC)

Why are croc's more closely related to birds than lizards/snakes?

Is this because crocodiles and birds share a more recent common ancestor than the croc's and lizard/snakes do? Any help would be appreciated, thank you!!Chrisbystereo (talk) 14:32, 20 February 2010 (UTC)

Yes. See the nice tree at Archosaur#Phylogeny. --Mr.98 (talk) 15:07, 20 February 2010 (UTC)

Yes, that is a very common way of defining how closely related certain species are. That doesn't necessarily mean they have more genes in common, or more physical characteristics, etc.. The speed of evolution can vary widely, so one branch may have changed far more than another. --Tango (talk) 15:46, 20 February 2010 (UTC)

Well, it does mean that they have more genes in common (or rather greater similarity between homologous genes) -- that's the data that is used to work out the evolutionary history. Looie496 (talk) 17:45, 20 February 2010 (UTC)

They don't work out the evolutionary history in big jumps, though. On a small scale, what you say is correct, but when you are talking about branches that separated hundreds of millions of years ago it isn't so simple. Each species will have a lot of genes in common with other species that are very closely related to them, but when you are looking at distant relatives it is difficult to say. Consider this example. Species X has genes AAAAA and splits into species Y and Z with genes AAAAB and AAAAC. Species Y then splits into Y1 and Y2 with genes BAAAB and CAAAB. Y1 then stays as it is and Y2 evolves into Y2' with genes CBBBB. Y2' and Y1 are quite closely related (their common ancestor is Y), but only share 2/5 genes. Y1 and Z are more distant relatives (their common ancestor is X) but share 3/5 genes. --Tango (talk) 19:10, 20 February 2010 (UTC)

The last common ancestor of crocodiles and birds is more recent (in time) than the last common ancestor of crocodiles and lizards & snakes. That makes them more closely related in exactly the same way that brothers and sisters are more closely related than cousins. Birds are descended from dinosaurs - and dinosaurs and crocodiles are closely related. SteveBaker (talk) 17:48, 20 February 2010 (UTC)

Decaying Copernicium

First off, chemistry is far from being my strongest subject. That said, when radioactive elements decay, they become other elements, yeah? So what does Copernicium become? If I'm totally off, please explain why in fairly simple terms. Thanks, Dismas|^(talk) 15:29, 20 February 2010 (UTC)

In the table at the top-right of each element page, it lists the stable isotopes, and for radioactive elements, has a "DP"="Decay product". So in this case, the most stable ones seem to become various isotopes of Darmstadtium (Ds). As for decay in general, there are a bunch of different ways radioactive elements can decay, some of which can modify its proton count (which makes it a different element and not just a different isotope)—see Radioactivity#Decay_modes_in_table_form. Anytime Z changes, you have a different element. The odd cases where Z goes up are from where other internal parts of atoms are converted into protons. --Mr.98 (talk) 15:52, 20 February 2010 (UTC)

132Sn is mentioned in the article text as well. (I would consider this a physics question, not chemistry) 75.41.110.200 (talk) 15:59, 20 February 2010 (UTC)

Though that's in the case of fission, not decay. (Which we can guess, immediately, by the fact that a fission product is going to be roughly 50% of the original, whereas a decay product is maybe 1 or 2 protons/neutrons different.) --Mr.98 (talk) 16:01, 20 February 2010 (UTC)

Spontaneous fission is a mode of nuclear decay. 75.41.110.200 (talk) 21:27, 20 February 2010 (UTC)

Erupting vanilla extract

While making waffles just now, I put the dry ingredients into one bowl and started mixing the wet in another. In the wet bowl, I put in milk and the eggs. Then when I put the vanilla extract in, it was roiling almost as if boiling. (so the combo was eggs, milk, van. extract) What causes this? Dismas|^(talk) 15:41, 20 February 2010 (UTC)

If it was bubbling when you poured it on to flour, I would suggest that percolation has the answers. Your flour and dry ingredients have pore spaces between the grains that are filled with air. As the fluid falls into those pore spaces, the air needs to bubble its way out. But it sounds like you've only mixed wet ingredients. Vanilla extract should really be pretty inert - it's mostly alcohol and water, with a trace amount of vanilla oil - but you could conceivably be seeing an acid-base reaction. I'm guessing your mixture is pretty viscous - so any trapped air (perhaps from whisking or mixing) might have formed bubbles that were slowly buoyantly rising to the surface. If the time constant for that buoyant rise is fairly slow, you might see air bubbling to the surface long after you stop mixing. Nimur (talk) 16:22, 20 February 2010 (UTC)

It's also possible that the vanilla extract is somehow acting as a surfactant and allowing the liquid to get more tightly into the pores of the flour, driving the air out. SteveBaker (talk) 17:40, 20 February 2010 (UTC)

Assuming that you only say liquid moving, with no visible gas bubbles and no liquid being forced higher than the normal surface of the liquid, the likely cause is mixing and surface tension effects. Vanilla extract usually contains a high proportion of alcohol, which has a lighter density than water, and certainly has a lighter density from the egg-milk mixture. When put together, they don't mix immediately, due to the density difference. As they slowly dissolve with each other, this sets up a number of concentration gradients, which can cause physical forces on the liquid. Additionally, and perhaps more importantly, water and water-alcohol mixtures have much different surface tensions. You can see this if you pour a small amount of alcohol into a very shallow layer of water. The water "tenses up" into a ball, and you get a "shimmery" movement at the water-alcohol interface as the two adjust to the surface tension differences. -- 174.21.247.23 (talk) 17:45, 20 February 2010 (UTC)

I'm sorry if I wasn't clear but the bowl only had the wet ingredients in it. Dismas|^(talk) 21:35, 20 February 2010 (UTC)

You've got a bowl with milk and eggs--are they beaten together or just poured in? Then you added vanilla extract. Dropped hard in one place (so that gravity makes it plunge towards the bottom) or gently sprinkled across the surface? When you say "roiling almost as if boiling", do you mean bubbling or just visible liquid mixing up-and-down? Alcohol is lighter than water, so if you drop alcohol to the bottom it will try to rise up again. DMacks (talk) 06:26, 21 February 2010 (UTC)

Just poured in. Dropped in one place. No bubbling, just a sort of eruption that didn't raise the surface of the liquid at that spot. It was fairly prolonged, on the order of 10-15 seconds. (on a side note, I just looked up 'roil' and apparently it's not a word though I've heard it used before to mean a rolling boil) After reading all the responses thus far, I'm betting that it's a surface tension thing. I wasn't aware that VE was mostly alcohol.

And on another side note, I've known a few alcoholics in my lifetime and I'm aware that they don't keep mouthwashes with alcohol in their houses. Now I'm wondering if I would find VE in their cabinets. Dismas|^(talk) 13:20, 21 February 2010 (UTC)

You would have to be pretty desperate to want to drink undiluted Vanilla extract - it's amazingly strong stuff. SteveBaker (talk) 16:19, 21 February 2010 (UTC)

I've heard (from a not terribly reliable source) that sailors in the navy would drink some sort of alcohol based extract (was it almond extract?) to get around prohibitions on alcoholic beverages. If true, I wonder what the suppliers thought about the amount of almond extract being ordered. Buddy431 (talk) 18:03, 21 February 2010 (UTC)

I heard that story too - but I thought they were distilling the alcohol out of the extract rather than drinking it 'as-is'. SteveBaker (talk) 18:23, 21 February 2010 (UTC)

Cooper Sulfate use

What are the affects on wildlife such as ducks and geese if cooper sulfate is used in a small neighborhood pond for algae control? —Preceding unsigned comment added by 96.28.172.66 (talk) 16:52, 20 February 2010 (UTC)

Copper sulphate can be toxic to fish, aquatic plants and algae - which would obviously eliminate a food source for the ducks and geese - but a lot depends on the dosage. At low concentrations, it's used to treat swimming pools (so it's obviously not toxic to humans at those levels) but out article lists a large number of alarming toxic effects on humans (so it's obviously nasty stuff in higher concentrations). It's also used to treat skin diseases in goldfish - so even the known toxicity to fish can only occur at higher dosages. Sadly, our article doesn't discuss toxicity to birds. I strongly suggest that you discuss the dosage levels used in the pond with whoever is doing the treatment - and try to establish that it's being used in reasonable amounts. Follow the instructions on the packaging very carefully - with particular reference to using only the minimum amount needed to treat the algae. This can be tricky without knowing the volume of water in the pond - which can be really tough to estimate. SteveBaker (talk) 17:32, 20 February 2010 (UTC)

focal length of lens

does focal length of a lens depends on the refractive index of its surroundings? like if we put a lens in water, will its focal length change? i think f should remain constant becoz by 'lens maker formula' :-

         1/f = (n-1)(1/R1 + 1/R2) 

it seems that focal length depends only on refractive index of the material by which lens is formed and radius of curvature of both faces. but if we put a convex lens in say a denser medium(optically denser than the lens) it will become a diverging lens. will not it? so as we put it in another medium which is rarer than the first medium, divergence of light shall decrease. by this we can conclude that in air if the focal length of convex lens is x then in water f will be y such that y > x. this is my dilemma.thanx§§§§ --Myownid420 (talk) 17:00, 20 February 2010 (UTC)

Technically, the refractive index should be measured relative to the medium in which the lens is immersed. However, because air and vacuum have almost the same refractive index (1.0000 for vacuum, 1.0003 for air at standard temp & pressure), it is rare for people to state which medium they are measuring it in. So, if you read that the glass that some lens is made of has a refractive index of 1.5 - then it really doesn't matter whether that's in air or in vacuum. If you put that same lens into water, then you should really use the refractive index of the glass relative to that of water - but nobody lists those kinds of numbers. Hence, you have to divide the refractive index of the glass in air by the refractive index of water in air to get the refractive index of glass in water. That does indeed mean that the focal length of the lens will be different in air than in water. SteveBaker (talk) 17:21, 20 February 2010 (UTC)

To summarize, the n in that formula is always $n_{\text{lens}}/n_{\text{environment}}$; see Snell's law, which contains only that ratio and neither index separately. We often neglect the denominator because it's so close to 1 for air and vacuum. --Tardis (talk) 17:38, 20 February 2010 (UTC)

Ideas for activity

I'm a nurse working in the area of Injury Prevention. We're going to set up an Injury Prevention booth at a college health event which will be 2 hours long. The booth will be one of many others that deal with a health topic. I set up a bulletin board with brief info on preventing injuries. Now I am looking for some ideas on the types of interactive activities around the topic of Injury Prevention that might be suitable for college students who stop by at my booth. I've currently thought of having students answer 5~10 True or False questions, but I'm open to any other ideas. —Preceding unsigned comment added by 70.68.120.162 (talk) 20:49, 20 February 2010 (UTC)

Can you get hold of some fake injuries like those used in TV and film that you can stick on people? That might give people a better idea of the consequences of their carelessness. It would also be fun, which always helps at that kind of event. --Tango (talk) 20:54, 20 February 2010 (UTC)

You could make a big, hollow foam polystyrene cube - dress it up to make it look like something really heavy and put fake "Warning: Really Heavy" stickers on it - then ask people to demonstrate how they'd pick it up off the floor. You'd be able to instantly show them the postural mistakes they (almost inevitably) make while doing that - and explain how to avoid the resulting back injuries by doing it right. SteveBaker (talk) 21:11, 20 February 2010 (UTC)

Maybe a picture or a staging of a common workplace situation having the students point out where the risks for injuries are. (a trailing cable, floor that will be slippery when walking with wet shoes e.t.c) Just looking at a website about slips and falls: [14] there's plenty of situations that a college student may meet in his/her part-time job. EverGreg (talk) 21:20, 20 February 2010 (UTC)

That would be a lot of fun - take over a room someplace - see just how crazy dangerous you can make it - take photos and challenge people to count the number of preventable injury sources there are! Sit around with some buddies and brainstorm all of the ways you can make it dangerous. Just try not to get injured while doing it because that would be something that would get you a fast-track to the Darwin Awards. SteveBaker (talk) 03:34, 21 February 2010 (UTC)

Bendroflumethiazide mechanism of action

Hi I understand that it is thought that some of the anti-hypertensive effects of Bendroflumethiazide may attributed to its inhibition of the enzyme carbonic anhydrase. (See the wiki article called thiazide) I'm not sure how the inhibiton of carbonic anhydrase would have an anti-hypertensive effect. How would this work? The article on carbonic anhydrases doesn't offer any suggestions. Thanks to anyone who can offer some insight. RichYPE (talk) 23:07, 20 February 2010 (UTC)

Well it affects bicarbonate levels in the blood and how well CO2 will dissolve in it. This in turn impacts blood acidity and H+ concentration. "Angiotensin II stimulates Na+/H+ exchangers located on the apical membranes (faces the tubular lumen) of cells in the proximal tubule and thick ascending limb of the loop of Henle in addition to Na+ channels in the collecting ducts. This will ultimately lead to increased sodium reabsorption" (Renin-angiotensin system). This is my guess ... John Riemann Soong (talk) 02:58, 21 February 2010 (UTC)

Green cones in the perception of colour

Hey, I was looking at this picture:

and it occured to me that we never really see green without quite a lot of red, and so we must be really sensitive to the difference between what our red and green cones are picking up. The purest green we'll ever see still looks like it'll maybe be 55% green to 45% red.

So I was wondering what it would be like to artificially stimulate only your green cones. This would essentially mean receiving RGB data in a ratio that you'd never experienced before, greener than the green. Would the experience of this be basically the same as seeing a normal bright green, or would one be able to tell that this is a colour they had never seen?

Thanks, Luke —Preceding unsigned comment added by 82.35.84.214 (talk) 01:00, 21 February 2010 (UTC)

I don't know what the result of that would be (or any way to do the experiment, actually), but it isn't easy to predict, because we don't "see" the raw output of the cones -- the neural activity is quite substantially transformed and recombined before it reaches the cerebral cortex, and then transformed even more inside the cortex. Along the way, the three-color cone activity pattern gets turned into an opponent process representation for which the primary hues are red, green, yellow, and blue. Looie496 (talk) 02:18, 21 February 2010 (UTC)

It's an interesting thought - what would happen if you got a green stimulus without any red stimulus at all? Certainly it's a bit of a guess because our brains are 'wired' to see things that way. Some colorblind people have no red sensors at all - so they are seeing what you're proposing. But the trouble is that their brains have formed since babyhood without that red sensor - so they don't know any different. The best answer is "We can't possibly guess without doing the experiment". If I had to guess, I think the result would be exactly what we see when we've been staring at a pure 625nm-ish red surface for a LONG time - then quickly glance at a green surface. Staring at the red surface will cause Neural adaptation which will make the brain ignore the "red" signal for a while. Then, when you look at a yellow or green surface, the red sensors are dumbed down and all you're registering is the green sensors. This is the basis of various Afterimage illusions. All I see when I do that is a really brilliant lime-green. But we have to be careful - we can't be 100% sure about the comparability of the result of this practical test with the impractical one you're thinking about. SteveBaker (talk) 02:46, 21 February 2010 (UTC)

Right. The color stimuli that correspond to impossible combinations of the three cone type activations are called Imaginary colors. Indeed, you can use the fact that human color adaptation is not instant, and have the L-cone gain reduced by strong input at 650-700 nm wavelength. Then, prompt preferential stimulation of the M-cones at around 550 nm should produce a "greener than green" color percept. However, I doubt the effect is going to be too strong, as V1 and higher visual areas have multiple negative feedback loops, making a highly unusual response next-to-impossible. Reducing this inhibition pharmacologically may actually produce an "impossible color" sensations via this mechanism; I think this was indeed reported as one of the LSD effects. Needless to say, any unauthorized use of controlled substances is VERY strongly discouraged. --Dr Dima (talk) 03:32, 21 February 2010 (UTC)

To be entirely accurate, LSD does not directly reduce inhibition. Still, it increases the excitability of the sensory areas of the cortex. --Dr Dima (talk) 03:40, 21 February 2010 (UTC)

The color you would see would not be green. Green is the color that is "55% green to 45% red". If you did only green cones you would have some other color, but not green. You have to remember our color is calibrated by the light we actually see, not by the labels we give the color sensors. Ariel. (talk) 04:33, 21 February 2010 (UTC)

Indeed. It is best not to refer to the different types of cones by colour, but by "short", "medium" and "long" (as they are labelled in that picture) to avoid confusion. --Tango (talk) 06:03, 21 February 2010 (UTC)

I think this has a straightforward answear. A situation where only the green cones are stimulated is closest to a situation where the green cones are stimulated the most and the blue and red cones are stimulated only a little and with equal intensity. From the figure it would seem that percentagewise, green is stimulated the most around 500nm, which corresponds to sea-green or blue-green according to a picture in the color vision article. EverGreg (talk) 13:15, 21 February 2010 (UTC)

Spectroscopy spectrum order

Okay, so I'm doing a lab right now on spectroscopy, and I'm given this equation: dsinθ=mλ. m is defined in the lab manual as "a positive integer equal to the order of the spectrum", but I am having trouble finding anything having to do with the order or how to know what value it may be.--十八 04:40, 21 February 2010 (UTC)

We're missing a lot of context about what kind of spectroscopy you're doing, so I'll answer in general. The idea is that as you go along, the the paths taken by two waves vary in length, and therefore the phase difference between them changes. Say they start off in-phase; as the path-length difference increases, they get progressively more out-of-phase and then they wind up coming back into phase again, and then back out-of-phase, and then back into phase, and so on. The "order" talks about how many times that happens: at the lowest m they are very close (m=0 is the starting in-phase phase); at higher m, they have gone through many complete cycles and beyond. DMacks (talk) 04:53, 21 February 2010 (UTC)

I'm doing visible spectroscopy.--十八 06:16, 21 February 2010 (UTC)

Are you using a diffraction grating, and is our article helpful? TenOfAllTrades(talk) 15:00, 21 February 2010 (UTC)

how does magnet works in space?????????

hi,i am one of your member and i want to know , how permanent magnet works in space ? I will be waiting for your answer. —Preceding unsigned comment added by Debiprasadnayak (talk • contribs) 06:14, 21 February 2010 (UTC)

A magnetism works through the vacuum of outer space just like it works in air. Magnetism is like light; it is not transmitted via real particles or pressure the way sound is. DMacks (talk) 06:17, 21 February 2010 (UTC)

Light IS transmitted via real "particles" though... --antilived^{T | C | G} 11:02, 21 February 2010 (UTC)

Coed Olympic Events

I just read the informative article on Olympic Sports but it does not cover the origin of the gender division, nor whether there have ever been any challenges to it. It occurred to me last night that there are more than a few Olympic events that could be fairly contested by both men & women together. In most shooting events strength plays only a very minor role, if not none at all (air pistols). I also suspect that gender would not imbalance a curling tournament, though perhaps the men could grind out a little extra bend to their throws?

Q1: Has there ever been a movement to unify some of the Olympic events?
Q2: In which events would gender impart very little or no advantage?

This question could have gone on Entertainment, but I find Q2 the more interesting and so I post it here. Thank you. 218.25.32.210 (talk) 07:15, 21 February 2010 (UTC)

Check out the equestrian events. B00P (talk) 08:25, 21 February 2010 (UTC)

Rightly or wrongly, the commentator on the US vs UK Women's Curling competition last night said something like: If this were the men's competition then this shot wouldn't have been a subject of debate - but it's a measure of how far Women's curling has come that they are able to even contemplate taking it" (after which the shot was taken and messed up). This suggests that the women's teams are getting closer to the men's game - but that they aren't there yet. I agree that there is nothing obvious in the biology of men and women to explain why women and men need to have separate games (unlike...say...weight-lifting). But the effect of merging the two events would undoubtedly to simply exclude women from Olympic curling. That would probably have a devastating effect on the number of young girls who see a female olympic curler and decide to take up the sport - and might well (effectively) keep women out of the competition forever. So I guess the Olympic committees prefer to keep male and female events separate until both genders are at about the same level. Is this "right"? Is it "fair"? Is it "sexist"? I don't know - it's like positive racial descrimination in college admissions - no matter what you do, there will be winners and losers. There are good arguments on both sides and no clear moral high-ground. If there were big protests amongst women curlers about being excluded from the men's game - then perhaps we'd be doing this differently. SteveBaker (talk) 16:12, 21 February 2010 (UTC)

Probably not what the OP means but it was a good play. Cuddlyable3 (talk) 17:00, 21 February 2010 (UTC)

I will note that there may be a preference for maintaining separate men's and women's events even where men and women are playing at comparable skill levels. This would be purely because it doubles the number of athletes who can participate, the number of events that can be televised, the number of medals to be won, and (potentially) the number of sponsorships and endorsement contracts available.

On the subject of curling, I will note that men (on average) are bigger and stronger than women. While this should make no difference for the majority of shots (which depend heavily on touch and finesse, rather than raw power), it will have an effect on a few of the high-power, high-risk shots (double peels, multiple raise takeouts, etc.) where a large amount of power needs to be finely controlled. I suspect that the biggest difference probably comes in sweeping, however. Bigger, heavier, stronger men are going to be able to put more weight on the brooms, and are going to be able to affect the course of a moving stone more effectively. TenOfAllTrades(talk) 18:07, 21 February 2010 (UTC)

Litmus paper

how does Litmus paper or Universal indicator work. what chemicals are on the paper? are these harmful? and where can i buy the paper? —Preceding unsigned comment added by 67.246.254.35 (talk) 08:16, 21 February 2010 (UTC)

Have you tried reading the article on litmus paper? It is harmless (but obviously you wouldn't want to eat it). It is easy to buy on line.--Shantavira|^{feed me} 08:46, 21 February 2010 (UTC)

whats in it thou? —Preceding unsigned comment added by 67.246.254.35 (talk) 08:58, 21 February 2010 (UTC)

litmus is extracted from lichens(a symbiosis of algae and fungi). its really a solution of purple color and changes to red when in contact with acid . and turn to blue when in contact with base. if u just want a acid base indicator you can use turmeric it turns red with base( try it on soap water) and shows no difference for acid

most probably litmus when in contact with H⁺ ions give red color and when in contact with OH^- it gives blue.--Myownid420 (talk) 09:26, 21 February 2010 (UTC)

As Shantavira hinted at, what exactly from the article requires further clarification? Nil Einne (talk) 11:49, 21 February 2010 (UTC)

Here's a picture of Roccella tinctoria used to make Litmus paper. The article São Jorge Island under "Economy" mentions a possible source of this lichen. Cuddlyable3 (talk) 16:55, 21 February 2010 (UTC)

As the litmus test article indicates, the compound that changes color with a pH change is 7-hydroxyphenoxazone (pictured in article). It works like all other pH indicators - that is, it's a compound where the conjugate acid and the conjugate base have different colors (so it changes color around the pKa when the molecule gains or loses a proton). And the two have different colors because the presence or absence of a proton (hydrogen ion) changes the electronics of the conjugated system, perturbing the energy levels of the molecular orbitals, altering the energy difference between them, and thus the wavelength (color) of the photons the compound can absorb. -- 174.21.254.47 (talk) 18:37, 21 February 2010 (UTC)

field lines of magnet

lets assume a straight conductor studded in a square cardboard,which is parallel to the ground, If xA current flows through conductor than the concentric field lines formed are at distance of m cm from each other. now current yA flows though the conductor, Such that yA > xA, and dist between circles is n cm. so will n = m or n>m or n<m? in simple words if current is increased in a conductor the field lines get denser or distance between them remains same?--Myownid420 (talk) 09:41, 21 February 2010 (UTC)

First you need to know that the magnetic field lines fill the whole space so it is not meaningfull to talk about the distance between them. But conventionally when drawing them they're spaced inversely proportional to the magnetic field intensity. The magnetic field intensity around a wire drops with the distance from the wire so you really shouldn't draw equaly space concentric field lines. Dauto (talk) 15:00, 21 February 2010 (UTC)

Those "field lines" are not things that really exist. Think of them as the contour lines on a map of a mountain - when you visit the actual mountain, there are no lines to be seen! The spacing between the lines is something that the map-maker (or the magnetic-field-illustrator) chooses to make the illustration be informative. As Dauto points out, if the field lines were intended to represent fixed intervals of magnetic intensity (like the 100' foot contours on a map that are equally spaced in height) then they wouldn't be uniformly spaced in the first place. If they are uniformly spaced then they must represent varying 'step' in magnetic field intensity. SteveBaker (talk) 15:55, 21 February 2010 (UTC)

The title is about a magnet but the question is about the magnetic field of a straight conductor. The cardboard and the ground seem to be unnecessary parts of the question. The magnetic field lines are indeed concentric with the wire but as Dauto pointed out the lines are just a way of showing the direction of the field which actually fills the whole space (it is a Vector field). As one moves away from the wire the distance between the lines should increase because the field gets weaker. To the question: Increasing the current by the factor y/a increases the magnetic field at a given point by the same factor so the line spacing gets less, n<m. You may like the article Field line but note that its top diagram shows electric field lines not magnetic ones. Cuddlyable3 (talk) 16:38, 21 February 2010 (UTC)

Stars ejected from the Milky Way

Are there any known stars that are no longer part of the Milky Way but are just floating away in extragalactic space? TheFutureAwaits (talk) 17:54, 21 February 2010 (UTC)

This section of our Milky Way article describes some globular clusters that are a long way outside of the galactic disk which may be leaving the galaxy. Also, it is thought that the Canis Major Dwarf Galaxy is close enough to the Milky Way to be ripped apart by it - and it would be surprising if some of the Milky Way's stars were not being pulled out in the opposite direction. But at these great distances, we aren't really looking so much at individual stars as larger groups like globular clusters. So I doubt we could point to a particular "known star" and say "Ooops! We lost that one!". Also, this stuff happens on truly spectacular time-scales - so it's not like we can see it happening. SteveBaker (talk) 18:17, 21 February 2010 (UTC)

See hypervelocity star. According to that article (or rather section), 10 are currently known. Looie496 (talk) 18:23, 21 February 2010 (UTC)

There are nine stars in Category:Extragalactic stars. TenOfAllTrades(talk) 18:39, 21 February 2010 (UTC) ...though most of those aren't free-flyers, but are in the Large Magellanic Cloud.... TenOfAllTrades(talk) 18:43, 21 February 2010 (UTC)

nutrition labels

How would a nutrition label for the average human body (male and female) be broken down and for the normal distribution of (male and female) humans? No, I am not planning to join a cannibal cabal but just want to know what nutrients the human body already contains so I can print a human nutrition label on a t-shirt to give people who look at me in that sort of way a printed answer to their question. 71.100.3.6 (talk) 19:44, 21 February 2010 (UTC)

research methods

A society has a very high gini coefficient, a high level of social inequality. The same society has a very high level of HIV infection. The hypothesis could be that social inequality 'causes' or exacerbates HIV infection, or conversely that high HIV infection leads to social inequality. We're trying to avoid a fundamental methodological mistake...is it possible that both can be true at the same time, or does scientific method assume that only one of these hypothesis can actually be 'true'?