Wikipedia:Reference desk/Archives/Science/2011 May 24

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May 24

Ambidexterity

I want to become ambidextrous since I think that would be cool and also in case I ever break my wrist but have to, say, sit an exam (it's also useful if my right hand gets tired from a lot of writing). I am right-handed right now and I would probably have to continuing using my right hand for anything important that has to be handwritten (such as homework) until I gain proficiency in my left. How should I go about doing this, and about how long would this take? Thanks. 72.128.95.0 (talk) 00:00, 24 May 2011 (UTC)

Although it can be aquired, it should take many years, as ambidexterity is a genetic trait. Plasmic Physics (talk) 00:16, 24 May 2011 (UTC)

If it's genetic, then it can't be acquired at all. You are either born with it or you aren't. It isn't genetic, though, so it can be learned (there may be a genetic component to it, meaning some people are genetically pre-disposed to learning it). I agree, it would probably take years to learn properly. Learning to write with your off-hand to a reasonable degree could be done a little quicker, though, if you spend a lot of time practising that one skill. --Tango (talk) 00:24, 24 May 2011 (UTC)

On a slightly more possitive note. Self taught motor skills tend to be easier and quicker to learn if you are in a younger age group. It may not take all that long.190.56.125.154 (talk) 00:38, 24 May 2011 (UTC)

It is genetic though, there exists a fraction of society where the person is neither/both left or right dominant neurologically, which is the root of natural ambidexterity. You can't learn to make yourself neurologically ambidexterous, but that doesn't stop you from learning how to use your hands in an ambidexterous fashion. Plasmic Physics (talk) 00:52, 24 May 2011 (UTC)

It's something you're born with, but genetic connections are weak at best. There's no known gene that if you have it you're certain to be a Lefty, and it doesn't tend to run in families anyway. The article on Handedness discusses this in depth, but genetics doesn't seem to play a large part. APL (talk) 01:46, 24 May 2011 (UTC)

It is certainly learnable for some people, so we can safely endeavor to answer the original question of how to go about it. Let me tell you about my own experience. Before I went to school, I used my left hand for drawing and writing my first letters, but the teacher convinced me that writing with the left would be awkward if I have to use a fountain pen; writing from left to right would mean that I would have to push it. Only much later did I realize that I could have turned the paper 90° clockwise and written top to bottom, like traditional Chinese. I tried that, but I never got as good at it as at writing horizontally left to right, or even backwards with my left hand. For me, the hard part of the turned and mirrored writing was in optically recognizing what I had written. That would be a different skill, which may however also be worthwhile. I was interested in ambidexterity for the same reasons as you, but I didn't spend much time and determination on it, just a few minutes here and there. Still, I'd be able to write homework with my left hand, albeit at a slower speed. But speed won't matter if it helps you enjoy your homework! The teacher may wonder why your writing looks different, but that shouldn't be a problem. So, you have at least these three ways to write with your left hand; I'd recommend experimenting with them and see which one works for you.

I also tried to be ambidextrous at other activities, such as racquet sports, but I never got anywhere with that; whether that is because I'm already doing those things with my dextrous (or should I say "laevous"?) hand, or because I never put as much time in it as into writing with both hands, I don't know. This indicates that the ideal to be completely ambidextrous may be hard to achieve; you may need to focus on certain areas.

On a related note, have you ever tried to use the other thumb for the space bar on the keyboard? I tried it shortly, triggered by a problem with my keyboard and my curiosity, but I gave it up soon, because it was too distracting. — Sebastian 06:08, 24 May 2011 (UTC)

I definitely have a handedness, but can do many things nearly as well with my other hand (and some things better). The difference for me is that I need to think more about each motion when using the "other" hand for a task. After a few minutes, I need to do so less, I assume I just get out of practice with a skill I don't perform as often? But anyway, one thing that helps me is to visualize my preferred hand moving (or sometimes even move it) and then have the other hand piggyback on that motion. That way I'm not so much "doing it with the other hand" as just "following the normal hand". For example, it's easier (or more legible) for me to write the same thing with both hands at the same time than to write with my non-dominant hand while keeping my dominant hand in my pocket. Similarly, it's easy to write with my non-dominant hand in mirror-image while writing the same thing normally with my dominant hand. DMacks (talk) 14:56, 24 May 2011 (UTC)

Case study!

A 25 year old male was addmitted to the emergency room after suffering a blow to the upper abdomen from a swinging beam.A CT scan demonstrated a significant hematoma deep within the substance of the liver as well as noteable amount of blood in small intensine.The decision was made to operate.Initial exploration revealed no trauma to the stomach or small intensine.

Questions 1-Why did the patient's vital signs stabilize upon administration of IV fluids?— 2-What is the likely source of bleeding? 3- Explain anatomically how the blood found its way into the small intensine,noting each step of its path? —Preceding unsigned comment added by Faridehm (talk • contribs) 01:39, 24 May 2011 (UTC)

Please do your own homework.

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Red Act (talk) 01:48, 24 May 2011 (UTC)

I hope this isn't my doctor. Googlemeister (talk) 14:19, 24 May 2011 (UTC)

What do you call someone that graduates med-school at the bottom of their class? --Tango (talk) 18:27, 24 May 2011 (UTC)

Waiter. Or is this a Jeopardy! response? Clarityfiend (talk) 19:51, 24 May 2011 (UTC)

I think the patient is in jeopardy if it is, Googlemeister. DRosenbach ^{(Talk | Contribs)} 03:54, 25 May 2011 (UTC)

Pro-neuro-genesis > proven-to-be-as-such FOODS?

Thanks. —Preceding unsigned comment added by 79.183.27.165 (talk) 10:29, 24 May 2011 (UTC)

I don't understand the form of your question. Plasmic Physics (talk) 12:43, 24 May 2011 (UTC)

I think it means "What foodstuffs are proven to assist neurogenesis?". Itsmejudith (talk) 15:07, 24 May 2011 (UTC)

Indeed, That's what I mean. 79.183.27.165 (talk) 17:16, 24 May 2011 (UTC)

Neurogenesis describes a (short term) increase from cannabis. Perhaps other edibles with antidepressant effects might work, like St. John's Wort, though I didn't find anything about that herb's effect on proliferation in a really quick and dirty search. Wnt (talk) 04:14, 25 May 2011 (UTC)

Land bridge between Asia and North America since...?

After the break-up of Laurasia... when did Asia and North America collide and build a land bridge for the first time? --KnightMove (talk) 10:54, 24 May 2011 (UTC)

They are still colliding, the earliest empirical evidence for a land-bridge is 55 million years before present. Plasmic Physics (talk) 12:41, 24 May 2011 (UTC)

55 million y.a.was the mid paleogene period. At that time North America was still seperating from Europe and no where near Asia yet. That period was marked by a much warmer climate than today, and little or no ice sheets. The aleutian land bridge was caused by a much cooler climate fixing a large amount of water in ice sheets, lowering sea levels so that the parts of the continental shelf were exposed first about 70 thousand y.a.Phalcor (talk) 14:50, 24 May 2011 (UTC)

I don't have any specific knowledge about when land bridges formed, but it is perhaps worth pointing out that the northwestern part of Asia actually belongs to the North American tectonic plate, not to the Eurasian plate. (The boundary between these two plates is very obscure.) So the first land bridge would probably not have at the Bering Strait, but somewhere well to the west or southwest. Looie496 (talk) 22:36, 24 May 2011 (UTC)

Yeah well, I didn't just pluck that number out of thin air. I read the article in Beringia. The final sub-section contains that number. Plasmic Physics (talk) 23:57, 24 May 2011 (UTC)

Hmmm... "Biogeographical evidence demonstrates previous connections between North America and Asia. Similar dinosaur fossils have been found between Asia and North America. For instance the dinosaur Saurolophus was found in both Mongolia and western North America. Relatives of Troodon, Triceratops, and even Tyrannosaurus rex all came from Asia."

As the dinosaurs disappeared 65 mya, this means that Asia and America must have collided even earlier?! --KnightMove (talk) 13:09, 26 May 2011 (UTC)

Today is a great day for science

When Dexter (Dexter's Lab) used to say that "today is a great day for science" did he mean that a) today is a great day to conduct science as some days may be better than others in, for example, wind surfing or b) that science has or will progress more than average on that particular day? --129.215.5.255 (talk) 11:31, 24 May 2011 (UTC)

This is a philosophical question, and so does not belong in the reference desks. It is simply not the type of question that they are designed to handle. Try an online forum. Plasmic Physics (talk) 12:22, 24 May 2011 (UTC)

Ask the author of the fictional cartoon Zzubnik (talk) 14:02, 24 May 2011 (UTC)

We cannot really tell you the answer, but this kind of question would be much better asked on the language desk than the science desk. You have to look at the context and decide for yourself (or ask the author, as recommended by zzubnik). Falconus^{p t c} 14:09, 24 May 2011 (UTC)

I think it's an obvious double entendre. The television show in question was unambiguously marketed to children, but the writers made heavy use of absurdist humor and dense prose-like dialog, evidently intended for an intellectual audience. Unfortunately, you probably won't get a more direct answer from the series' creator, as Genndy Tartakovsky squandered an opportunity to explain the premise of his television show during the original debut of Dexter's Laboratory, on Space Ghost in February 1995. You can actually view this interview online. Literary and theatric elements of this genre defy analysis. Nimur (talk) 15:22, 24 May 2011 (UTC)

For what it's a joke on, you should be aware of the battle cry/saying "Today is a good day to die", either from the Lakota Sioux's phrase "Hoka Hey", or more popularly from Klingon (also others). -- 174.31.219.218 (talk) 16:12, 24 May 2011 (UTC)

Speed of sound problem.

Hi all,

I am proof-reading documents on the Doppler effect, and I read the following, which I would like your opinion on.

"Sound travels in air at approximately 750 mph. If, for example, the sound is moving towards the listener at 75 mph then the sound wave fronts will travel to the listener at 825 mph."

Is this true? I can not get my head round this. I thought the speed of sound was absolute. Opinion in the office is mixed.

Thanks for any help offered. Zzubnik (talk) 15:39, 24 May 2011 (UTC)

The speed of light in a vacuum is absolute. The speed of sound varies depending on the medium, temperature, and other stuff. -Atmoz (talk) 15:45, 24 May 2011 (UTC)

Thanks, Atmoz. I should have added that I understand that the "speed" of sound varies depending on the medium it is travelling through. — Preceding unsigned comment added by Zzubnik (talk • contribs) 15:55, 24 May 2011 (UTC)

Thanks again for all the help. The issue has been resolved. It was an Ex teacher writing for a publication. I knew it wasn't right, I'm surprised the teacher was so confused about it. Thanks again for your help. — Preceding unsigned comment added by Zzubnik (talk • contribs) 12:42, 26 May 2011 (UTC)

There are two possible issues. The medium carrying the sound could be moving from the source to the listener at 75 mph, that is, there is a 75 mph wind blowing at the listener from the direction of the source. This would make the speed of sound, as observed by a stationary listener, as 825 mph. If both the source and and listener are stationary with respect to the earth, they both would observe the same frequency.

If the wind were calm and the source was moving toward the stationary listener at 75 mph, that would be a different situation. The listener would observe a speed of sound of 750 mph, but the listener would observe a higher frequency for the sound than the source would. Jc3s5h (talk) 15:48, 24 May 2011 (UTC)

Jc3s5h, thanks for the reply. I understand the frequency shift part. I can understand how moving air can change the apparent speed. But, in the example I stated, would the sound reach the listener faster than the speed of sound? I am under the impression that it will never exceed the "speed of sound". Again, thanks. Zzubnik (talk) 15:51, 24 May 2011 (UTC)

The basic problem is the terminology in the sentence. Sound waves travel through air. Sound sources travel also. Sound is vague. What does that mean? So, claiming that "sound travels" doesn't specify if it is the waves or the source. If the sound waves are moving at 75mph, it implies that they are travelling through a thick medium that inhibits sound waves. If the sound source is moving at 75mph, it simply means that the frequency will be shifted. In either way, the sentence doesn't appear to be accurate. -- kainaw™ 16:24, 24 May 2011 (UTC)

No, the speed of sound does not change, and the quotation is not really correct. What the author was trying to explain is why the wave fronts are "bunched together" in front of a moving object. Each successive wave front is emitted a certain period of time later (depending on the frequency); during that period of time, the object emitting the sound has moved. That means that the wave fronts are closer together than they would otherwise be, by a factor that includes the sum of the object speed and the speed of sound.

To illustrate, take this equation from Doppler effect:

$f=\left({\frac {v+v_{r}}{v+v_{s}}}\right)f_{0}\,$

where

$v\;$ is the velocity of waves in the medium

$v_{r}\,$ is the velocity of the receiver relative to the medium; positive if the receiver is moving towards the source.

$v_{s}\,$ is the velocity of the source relative to the medium; positive if the source is moving away from the receiver.

The effective frequency contains the factor ${v+v_{s}}$, which is your 750 + 75 = 825mph. That's not the effective speed of sound, it's the effective change on frequency. Your quote is an misleading explanation. Andrew Jameson (talk) 16:26, 24 May 2011 (UTC)

(ec) It appears that there's a confusion of terminology between the speed of propagation (group velocity), and the "speed of the wave front" phase velocity. The author is stating that the "wave fronts" propagate faster than the speed of sound. I think what they intend to say is that the apparent phase velocity is higher than the group velocity, resulting in a frequency shift. You can watch a physicist explain this using proper terminology here: Walter Lewin explains Dispersion, Phase Velocity, Group Velocity, from OpenCourseWare at MIT. Nimur (talk) 16:29, 24 May 2011 (UTC)

Yes but sound is a non-dispersive wave and its group velocity is identical to the phase velocity so that can't be correct either. The quoted phrase is misleading and unclear at best. Dauto (talk) 16:55, 24 May 2011 (UTC)

I agree. The original quote abused terminology pretty bad. The correct terminology is that the wave has been doppler shifted. To first order, its propagation speed is unchanged. With a little loose terminology, it is plausible to describe any frequency-shifting process as a generalized form of "dispersion," but this is non-standard at best, and as phrased above, I think would be invalid. Nimur (talk) 21:07, 24 May 2011 (UTC)

Thank you all for your continuing input on this. I can't tell you how stressed this is making me (I like facts to be correct). The statement is horribly wrong to start with. It should quote that the sound source is moving at 75 mph. Following the logic of this, the sound of an approaching space shuttle would approach the listener at (speed of shuttle plus 768 mph), which means that the sound could be traveling at more than 10,000 mph! Surely this is incorrect? Once sound waves reach "the speed of sound", they can travel no faster? Zzubnik (talk) 17:00, 24 May 2011 (UTC)

You are right, that is surely incorrect. And sound waves don't reach the speed of sound, they simply are at the speed of sound. As an aside, when you consider objects which move faster than the speed of sound, like your 10,000 mph space shuttle, you have supersonic flow, which results in a shock wave: that's different fluid behavior than occurs in subsonic flows, and not really applicable to your Doppler shift quote. Andrew Jameson (talk) 18:01, 24 May 2011 (UTC)

Can you supply the complete paragraph, it may be that what the author is attempting to explain is buried in there. Failing this, I would email the author back and query what he means. Proofreading is more about catching typographical errors, this is more like editing to make the text factually correct and understandable. I would demand extra money for that level of skill and fact checking. What is the purpose of the document anyway? I hope it 'ain't some spotty student's thesis.--Aspro (talk) 18:13, 24 May 2011 (UTC)

Two words: sonic boom. Plasmic Physics (talk) 05:55, 27 May 2011 (UTC)

Speed of light etc.

It would appear that both the speed of sound and the speed of light are constants within a given medium. Sound has to do with vibrations, so the speed of sound in denser media is faster than in air, if I'm recalling correctly from high school physics. The opposite is true of light, whose ultimate speed is in a vaccuum and is slower when traveling through a medium. My question is this: What is the slowest speed that light has ever been measured? That is, what medium, if any, will slow light down to the point where it's maybe even visibly noticeable? ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:18, 26 May 2011 (UTC)

A material's refractive index is inversely proportional to light's phase velocity in the material. The highest refractive indices listed in the list of refractive indices article is only up close to 4, which isn't all that impressive. However, there's also slow light, in which light has a very slow group velocity. The article mentions an experiment in which they got the light's group velocity down to an astonishing 17 m/s (listed in the article as 38 miles per hour). Red Act (talk) 15:02, 26 May 2011 (UTC)

Why does black cherry sparkling water spew all over the place but not other flavors?

In recent years I have stopped buying store brand sparkling water because I don't like the taste. They started using sucralose as the sweetener, and that tastes good only with brands such as Fruit2O. Last Christmas, since the recycling facility was going to be closed for two Saturdays, rather than go to the trouble of remembering to deliver bottles during the week, I chose to buy liter bottles of sparkling water, which take less time than half-liter bottles and probably save some space too. To deal with the taste I could just eat crackers immediately after drinking. But the black cherry sparkling water spewed all over creation like it had been shaken up. This was true for every bottle. The Pomegranate-Acai-Blueberry did not, but it tasted terrible. The black cherry actually tasted good and, for various reasons, if I can find it I get it again. Now I think I've figured out the formula for removing the cap for the first time in such a way as to prevent the spewing, and I reported this to the store, who forwarded the message to the manufacturer, who promised to investigate. Any ideas what they might find?Vchimpanzee · talk · contributions · 17:59, 24 May 2011 (UTC)

Well, the box with the black cherry flovored bottles could have gotten dropped shortly before they got put on the shelf and you bought them soon after. Googlemeister (talk) 18:12, 24 May 2011 (UTC)

This is happening to black cherry bought five months later. It would have to be a very big coincidence.Vchimpanzee · talk · contributions · 18:36, 24 May 2011 (UTC)

May be you have a tendency to treat the bottles in such a way they get shaken up before opening? Nil Einne (talk) 19:26, 24 May 2011 (UTC)

I would guess that the black cherry contains some ingredient not in the pomegranate-acai-blueberry that acts as a nucleation site. Andrew Jameson (talk) 19:35, 24 May 2011 (UTC)

I do not do anything to the bottles. I just opened a Key Lime bottle, and no problem there.

And I am now careful when I open a black cherry bottle. I open it very slowly, and if I hear the sound, I put the cap back on quickly and try again until I no longer hear the sound.Vchimpanzee · talk · contributions · 19:40, 24 May 2011 (UTC)

Just a note, completely unrelated to your actual question: Maybe you'd be just as happy with no sweetener at all? I know I prefer it. There are brands that add a little fruit essence but no sweetener; they are very refreshing. --Trovatore (talk) 19:42, 24 May 2011 (UTC)

Maybe the cherry is bottled in a different bottling plant where the carbonation process is slightly different.It should tell you on the bottle where.190.56.105.177 (talk) 20:02, 24 May 2011 (UTC)

The simplest explanation is just that the Black Cherry bottles are newer. I assume these are in plastic bottles, which will slowly leak out the carbonation and at the same time leach toxic chemicals into the drink. This might also explain why the older bottles (which might have sat on the shelf for years before you bought them) taste bad. Try looking for dates on the bottles.

Another possibility is that they are using different plastics in the two bottles, and the Black Cherry bottles don't leak and leach as badly. Does the plastic seem any different (try squeezing both to feel the resistance). StuRat (talk) 20:13, 24 May 2011 (UTC)

I haven't checked these out, but thanks. The bottling location may be some complicated code.Vchimpanzee · talk · contributions · 21:33, 25 May 2011 (UTC)

I saw some different ingredients listed with black cherry, and the label says it contains calcium while the others don't. I also got the sweetener wrong. It's actually aspartame.Vchimpanzee · talk · contributions · 15:20, 30 May 2011 (UTC)

Ancient Greeks

What was the daily live of the ancient Greeks like?

I have been reading the tales of ancient Greeks on http://www.sagen.at/texte/sagen/sagen_klassisches_altertum/sagen_klassisches_altertum.htm (German language). I'm aware that these are mythological tales not to be taken literally but they give some insight on the circumstances of live back then (some time before 1000BC, I guess). And before I smash you with a text wall, my question simply is this: where can I get more information on the common lives at that time? What I like to know is whether it is true what I can read between the lines.

All in all people back then would have quite a relaxed attitude (ah, at least those "people worth talking about", and, of course, unless the "gods" would meddle with their affairs). Women, as such, seemed not to be looked at as inferior, as many of the gods where female and played major parts in the game, notably Hera, Athene and Aphrodite. Most characters mentioned were called "heroes" ("Helden" in the German text) but from the context, "worrier" would be more accurate. When there was no actual war, a sense of "adventurer" would mix into the word. They fed mainly on beef, and to a lesser extend on pork, sheep and goats. On the islands as well as on the main land there seemed to been plenty of game around, and for people with arrow and sword, food was not an issue. It looks like wheat was used more as a kind of a spice. They had swords to kill the cattle without notable effort. There is no mentioning on any problem to make fire. Ships with rows and sails are frequently mentioned without any reference on who built them and how, so the technology must have been very common. With the exception of the mythological Hephaistos, no smiths are ever mentioned. So I guess this technology would also have been so common as not to be worth mentioning.

95.112.218.222 (talk) 18:26, 24 May 2011 (UTC)

Sorry to burst your bubble, but you are definitely idealizing the quality of ancient Greek life. The question is just how much. For starters, check out Ancient_Greek_cuisine, which starts out "Ancient Greek Food was characterized by its frugality, reflecting agricultural hardship. It was founded on the "Mediterranean triad": wheat, olive oil, and wine." (emphasis mine) -- meat is mentioned often in mythology because it was luxurious, that's why all the sacrificing of fatted calves, etc. SemanticMantis (talk) 18:56, 24 May 2011 (UTC)

No bubble to burst. I already suspected the tales where slightly biased. But at least the people were on wine and not on healthy carrot juice. On the other hand, it is mentioned that the island of Lemnos was uninhabited, as probably wide other areas were. So wouldn't it be possible, at least for the "hero" (hunter) class to live on hunted meat? 95.112.218.222 (talk) 21:49, 24 May 2011 (UTC)

You should bear in mind that when we speak of ancient Greece, we usually mean the eighth through the second centuries BC. The famous stories, however, refer to the much earlier Mycenaean period, the 16th through the 12th centuries BC. It's a bit like trying to get an idea of modern England from stories about King Arthur and Robin Hood. Also, the protagonists tend to be nobility, so there is little sense of the hardships faced by ordinary people.

Notwithstanding the prominence of goddesses, women were confined to the domestic sphere, totally inferior to men. The title of the leading text on the subject, Goddesses, Whores, Wives, and Slaves: Women in Classical Antiquity, gives some idea of their possible roles.

You may find our article on Mycenaean Greece of some use. There are several books on everyday life in ancient Greece, but I don't know if there are any about everyday life in the Mycenaean period. John M Baker (talk) 21:58, 24 May 2011 (UTC)

Yes, the article Mycenaean Greece points the direction, but I would like much more information. As for the smiths: "The metallurgical industry is well attested at Pylos, where 400 workers were employed. It is known from the sources that metal was distributed to them, that they might carry out the required work: on average, 3.5 kilograms (7.7 lb) of bronze per smith. On the other hand, it is not known how they were paid — they are mysteriously absent in the ration distribution lists. At Knossos, several tablets testify to the making of swords, but with no mention of the true industry of metallurgy." indicates that really all work was done by Hephaistos and his Cyclops ;-) 95.112.218.222 (talk) 22:45, 24 May 2011 (UTC)

Our article on Opson may be interesting in this context -- the basic thrust is that the ancient Greeks considered it decadent to eat a diet in which bread was not the main component. A person who ate a lot of meat (or fish) was derided as an opsophagos -- an "opson eater". 22:59, 24 May 2011 (UTC)

In a nomadic culture, opson will be bread rather than meat. 95.112.218.222 (talk) 23:48, 24 May 2011 (UTC)

I don't think nomads consider bread "decadent." (And they certainly don't eat just meat. You'd have to be one prosperous nomad to eat a heavy meat diet.) --Mr.98 (talk) 02:52, 25 May 2011 (UTC)

Hippocrates described gout in some detail, saying for example that eunuchs didn't suffer it, nor women before menopause. While I can't tell from that how many people were having meat, clearly some had access to enough to get into trouble. Wnt (talk) 04:03, 25 May 2011 (UTC)

Yes, but Hippocrates is much, much later than the Homeric heroes our IP is referring to. And while ancient Greek pastoralists/fishermen probably lived much like their descendents did until recently, it is harder to get a handle on the economy of early city states. The IP might like to look at information on Sparta, which liked to claim it was the closest to the heroic age in its lifestyle (none of your namby pamby democracy etc). Elen of the Roads (talk) 13:56, 25 May 2011 (UTC)

Carotene acetate

Hi. I had another dream about an organic molecule. This time, I had a container of carrot juice, and was wondering whether it could generate toxic compounds. The phrase for carotene acetate popped into my mind (or was it carotene-β acetate?). Now, this might be yet another nonexistent molecule I conjured, but some kind of bond could potentially occur to make such a molecule. The other time, the propylene molecule I conceptualized did turn out to be related to something real. Now, I have no idea whether toxicity is even relevant here. However, is there any information on this molecule, and what are its properties in terms of formation and effects on the human body, if it exists? How is it different from regular vitamins (A and B?) and from regular carotene? Thanks. ~AH1 ^(discuss!) 18:52, 24 May 2011 (UTC)

As your question arises from a dream it is no surprise that it is not very precise. Perhaps Carotene can give you a bridge from your dream state of mind to your awake state. If you are one of those people who are blessed/hunted by dream pictures, you might be interested to do it in an organized/controlled way, The mainstream would be meditation, but I like to simply doze off while focusing on a question. 95.112.218.222 (talk) 23:08, 24 May 2011 (UTC)

You wouldn't have a salt with carotene - note that it is purely C and H with a lot of double bonds. Now "carotenyl acetate" compounds are possible.^[1] You could also create "_-acetyl carotene" by sticking on an acetate somewhere. Wnt (talk) 03:50, 25 May 2011 (UTC)

Umbilical cord

A friend recently experienced a miscarriage a few days before her due date. She told me that the cause was the umbilical cord being wrapped around the baby's neck. How can this kill the baby? The baby is not using mouth/nose/throat for either oxygen or nutrients, with everything supplied by the umbilical cord, so how can constriction around the throat cause death? 148.177.1.210 (talk) 19:52, 24 May 2011 (UTC)

Cuts off blood supply. See Nuchal cord. --Aspro (talk) 20:02, 24 May 2011 (UTC)

I have to admit I find that article too dense with technical details to be all that useful. So the wrapped cord constricts a blood vessel in the baby's neck preventing, for example, blood flow to the brain? Or the wrapped cord cuts off the blood supply through the cord into the baby? 148.177.1.210 (talk) 20:12, 24 May 2011 (UTC)

Either or both . The result is the same.190.56.105.177 (talk) 20:34, 24 May 2011 (UTC)

To put it perhaps more complex but with more elaborate details that may explain things better, every part of the body requires sufficient blood supply to prevent necrosis (tissue death). There are two sets of arteries that supply the head, (which contains the brain, an essential organ for life): the vertebral arteries and the carotid arteries. The vertebral arteries are of far smaller gauge than the carotids and they exist almost perfectly nestled within the somewhat bony protuberances of the cervical vertebra (spinal column bones) and would likely not be compressed to a great degree by neck strangulation. The carotids, however, exist more towards the front of the neck and are largely unprotected from undue pressure placed by any sort of belt, rope or cord-like device that might find its way around someone's neck (be it a murder weapon, a noose or, in this case, the umbilical cord. After giving rise to many arteries that service the thyroid, the face, the oral cavity and other important structure of the head but prior to providing any arteries that provide blood to the brain, the aforementioned vertebral arteries and the internal branches of the carotid arteries fuse in a major anastamosis (fusion region) called the circle of Willis. In a sense, then, each artery can be compensated by blood provided by the other arteries because they all meet to then become the arteries that service the brain, but if the carotids are cut off, I think it's that the vertebral arteries are not of sufficient caliber to provide enough blood supply to the brain. That's why carotid restraint works, but if applied for long enough, the victim dies of asphyxiation. It might also not be an issue of just blocking the arteries -- if the veins are constricted enough to prevent blood from leaving the head, there is no place for blood to go even if it is provided by the vertebral arteries, and even if the veins are not blocked, blood pressure reduction might have its dangers. And umbilical cord strangulation is likely not happening for a minute like a chokehold -- it probably lasts indefinitely. Anyway, that's a summary of what's going on, more or less, during strangulation. DRosenbach ^{(Talk | Contribs)} 03:51, 25 May 2011 (UTC)

I am sorry for your friend's tragic loss. Edison (talk) 16:15, 25 May 2011 (UTC)

In hospital a Caesarean section is often the course chosen when fetal distress due to a nuchal chord is observed in time. Cuddlyable3 (talk) 21:31, 25 May 2011 (UTC)

In the womb the fetus has no need to breathe, and heartbeat is self-exciting. As a result even an anencephalic infant can be born. Therefore, I doubt that strangulation is an issue at the neck. The cord, however, is another matter. Wnt (talk) 15:57, 28 May 2011 (UTC)

Radioactive Elements

would a radioactive element completely decay ? —Preceding unsigned comment added by 175.110.91.49 (talk) 20:54, 24 May 2011 (UTC)

Your question is unclear. can you elaborate? Dauto (talk) 20:57, 24 May 2011 (UTC)

I mean a radioactive element has a half life of a period T/2 in which the half of the atoms would decay. My question is would all the atoms of radioactive element decay ? —Preceding unsigned comment added by 175.110.91.49 (talk) 21:01, 24 May 2011 (UTC)

I'm guessing slightly at what you mean, but I imagine the question is thus: if the number of nuclei keeps halving, when do we arrive at none? If this is the case, then at some point after we have one. Once you get down to some fairly small number of individual nuclei, it's best to think of it thus. Each nucleus has a certainly probability it will have gone after one second, and two seconds, and so on. So there's a probability that's they've all gone after one second, after two seconds, etc. which will be increasing. There will be a chance that there is still one nucleus left after a million years, but if t is some small number of seconds, then this is really really unlikely. In short, the number of nuclei reduces, until the last one goes. Predicting exactly when is impossible, but it's likely to be around another half life, if it has survived up till now. Grandiose (me, talk, contribs) 21:12, 24 May 2011 (UTC)

Or, stated another way "given an infinite amount of time, all atoms of radioactive elements will decay". (Even stable atoms will eventually break down, due to proton decay, but that's another topic.) StuRat (talk) 22:09, 24 May 2011 (UTC)

(ec) The half life law is only valid on large samples. Nearly all samples you think of are large. Avogadro constant will tell you how many (*many,many,many*, a really huge number) atoms you have in a sample of a given weight. The Law of large numbers explains why large samples behave very predictable. Think of it that way (only a picutre/model): for each atom, every second, you throw a dice, and if it happens to show "six", then the atom decays. If you have a really large number of atoms, you can count on it that the number of decaying atoms will be fairly exactly one sixth of the total number. If you have only few atoms then the number of decaying atoms will deviate from the theoretical 1/6. The concept of probability is not easily understood, so you shouldn't feel uneasy if you don't get it on a superficial reading. If you have any specific trouble, don't hesitate to ask here on the desk. 95.112.218.222 (talk) 22:17, 24 May 2011 (UTC)

As a practical example, Carbon Dating is only possible with objects up to about 60,000 years old, about 10 times the half life of Carbon-14. At that point, there's only about 1/1000th of the original isotope left, which is still much, much more than zero. I think about 80-100 half lives is a good rough estimate for how long until an object is completely gone: that's a factor of 10^-24 - 10^-30, which, as Mr. 95.112 pointed out, is about the same scale as many elements are found at. Buddy431 (talk) 22:57, 24 May 2011 (UTC)

There's an interesting physics problem buried in this. At what point does the sample itself get small enough that half life stops making sense? Obviously if you are down to one atom, the half life no longer means anything (QM does not let you ever predict when a single atom will decay). But what's the larger limit than that? Is there a way to express half life that takes into account the rising uncertainty as you get smaller (e.g. handfuls of atoms) samples? --Mr.98 (talk) 02:25, 25 May 2011 (UTC)

Nay, the half-life means the same thing for one nucleus as a billion: there's a 50-50 chance that the nucleus will decay in that period of time. You can't say that it will decay at a certain time, but you can't say that about a billion either. If you hold up a chunk of uranium to a Geiger counter, there's a certain length of time until the first click. The lump doesn't know it was supposed to click, though - there's just as good a chance that it will last another equal period of time without a click after that, and so on. In theory it could stay cold for centuries, but that's one situation where your odds really are better in the Lotto. Wnt (talk) 03:29, 25 May 2011 (UTC)

Also interesting: If you confine one unstable atom in a box of finite volume such that the decay products will also be confined to that volume then, after waiting for sufficiently long time, you can find the original atom back with probability arbitrarily close to 1. Count Iblis (talk) 15:17, 25 May 2011 (UTC)

Hmmm, implying that neutrinos can mediate nuclear fusion? Wnt (talk) 15:58, 28 May 2011 (UTC)

We are not always talking about a gram of Plutonium or a milligram of Radium. For many years we have read of nuclear scientists discovering new high atomic number elements with ridiculously short half lives, in experiments where a few atoms of the element were produced. It does not seem so far fetched that in these experiments all the atoms decayed over time. In 1994 Element 110 (later named Darmstadtium "flickered into existence for less than a thousandth of a second" at Darmstadt, Germany. It was claimed that "four atoms" of it were detected by a nuclear fusion reaction. Do you expect that some of them are still in the atom smasher there, decaying atom by atom, or has the last atom decayed? Is there a lab somewhere which has , in a vault, decaying chunks of Roentgenium, Copernicium,Ununtrium, Ununquadium, or Ununpentium (which has only existed so far as 30 atoms per the article)? Why should there be confusion about how to describe the time course of decay of 4 or 30 atoms of such elements? Why wouldn't the same process describe the decay of a tiny speck of a few atoms of naturally occurring atomic elements? Edison (talk) 16:05, 25 May 2011 (UTC)