Wikipedia:Reference desk/Archives/Science/2009 July 8

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July 8

Paddy Mouse

What is Paddy mouse?70.73.145.207 (talk) 01:07, 8 July 2009 (UTC)

Paddy is a rice field. I've seen Mus booduga being referred to as a "rice paddy mouse", but I guess any murid living in a paddy may qualify as a "paddy mouse"... --Dr Dima (talk) 01:39, 8 July 2009 (UTC)

Total guess here, but is "paddy mouse" something akin to Welsh rabbit; that is it really isn't mouse, but the term is used as a perjorative towards Vietnamese cuisine? --Jayron32.talk.contribs 02:33, 8 July 2009 (UTC)

No, the Vietnamese cuisine article clearly talks about the paddy mouse meat sensu stricto. --Dr Dima (talk) 03:53, 8 July 2009 (UTC)

Well then, why not eat them? Not a lot of meat, I'd imagine, but get a few dozen together and the right spices, and it sounds like a fine dinner. --Jayron32.talk.contribs 04:33, 8 July 2009 (UTC)

I would actually very much like to try what a well-prepared paddy mouse dish tastes like. From personal experience, a platter of frog legs is a fine dinner to say the least, miniature size of the said legs notwithstanding. Never tried a roasted rodent, though. Do you know of any Vietnamese restaurants in US or in Western Europe that serve a paddy mouse dish? --Dr Dima (talk) 07:59, 8 July 2009 (UTC)

I was imagining a pejorative toward something Irish. —Tamfang (talk) 18:05, 21 July 2009 (UTC)

Do birds have an equivalent to the navel, as seen in mammals?

In mammals, the navel/bellybutton is the point at which the umbilical cord was attached while in the womb. Is there something similar in birds, i.e. at the point at which the bird was connected to the yolk, while in the egg? I've seen cross-sectional pictures of fertilized eggs and it looks as though the bird foetus is connected to the outside of the yolk by something similar to an umbilical cord. --84.69.51.112 (talk) 01:12, 8 July 2009 (UTC)

No. Not even all mammals have them. We are a part of the "Placental Mammal" sub-group - the umbilical cord connects to the placenta. No placenta - no cord. Hence, Duck billed platipus and Kangaroos don't have belly buttons because, while they are mammals, they are not placental mammals. Birds lay complicated eggs with all sorts of membranes and stuff in them - but I don't think there is a similar connection. See image at right of a 1 week old chick embryo - I don't see any kind of cord there... SteveBaker (talk) 02:48, 8 July 2009 (UTC)

the Vitelline duct or the vitelline system is the thing that connects the yolk to the embryo.--Lenticel ^(talk) 03:58, 8 July 2009 (UTC)

Dislocated knuckles

Just read an article in my local newspaper about a policeman suffering a dislocated knuckle while attempting to arrest someone. I've never heard of such an injury before; is it very common? Joint dislocation makes me guess that it's not the same as any of the dislocated finger pictures (can't remember which joint is the knuckle, and our article is very poor quality, but I expect that these would also be captioned "dislocated knuckle" if it were the same thing), so I'm assuming that this is not a dislocated finger. Nyttend (talk) 02:09, 8 July 2009 (UTC)

Knuckle is a common term for the any of the three joints on each of your fingers (well, two on your thumb). A dislocated knuckle is identical to a dislocated finger. The two bones that meet at one of the knuckle joints can become disarticulated just as any other joint can. --Jayron32.talk.contribs 02:31, 8 July 2009 (UTC)

Animal intelligence and attempts to escape captivity

Is there any evidence on whether more intelligent animals in captivity are more or less likely to attempt to escape? NeonMerlin 02:12, 8 July 2009 (UTC)

Depends how you define intelligence. A hamster is more likely to escape than a dolphin; can you claim that the hamster is more intelligent? A male cat with its balls still attached is more likely to attempt to escape than a neutered one; does the feline intelligence reside in the scrotum? I don't think so... --Dr Dima (talk) 04:00, 8 July 2009 (UTC)

The females of the human species thinks that their male counterpart do think with their scrotum and its attached part. :)--Lenticel ^(talk) 04:22, 8 July 2009 (UTC)

You know, NeonMerlin was asking a question, not asserting something. Tempshill (talk) 04:29, 8 July 2009 (UTC)

Well, monkeys will escape if given the slightest opportunity, and they're the most intelligent animals in captivity, so at some level it is true. Looie496 (talk) 05:53, 8 July 2009 (UTC)

The most intelligent animals in captivity are chimps, not monkeys.--80.58.205.37 (talk) 08:08, 8 July 2009 (UTC)

Surely some humans in captivity are smarter than that... Prison escape? Nimur (talk) 15:01, 8 July 2009 (UTC)

I would say that monkeys/chimps are escaping not to necessarily escape, but out of curiosity of the unknown. I know my pet budgerigars are kept captive in a cage and they like it. Whenever I remove them from the cage, they always try to fly back into it. This must be because they know that the cage provides security and necessities for their survival. This would be untrue for a captive wild bird rather than birds that were born in the cage. -- penubag  (talk) 10:27, 8 July 2009 (UTC)

Parrots are fairly notorious for figuring out how to escape from their cages - routinely pulling back bolts, undoing clasps, lifting up sliding panels, butting open hatches, etc. I've personally seen a cockatoo that understood how to open a padlock by turning the key (the cage was actually padlocked to prevent the bird from getting out - the owner left the key in, figuring that she would *never* work that one out!). Budgies, whilst not as intelligent as Macaws, Amazons, African Greys, Cockatoos, etc. do sometimes work out how to get the door open - though it seems to very from individual to individual. Some never appear to consider trying to escape - though I suppose that it may just mean that those particular birds are quite happy to remain in the cage. --Kurt Shaped Box (talk) 10:52, 8 July 2009 (UTC)

Does John Dillinger count as an "intelligent animal?" He made some impressive escapes. Our hamster lifted up the water bottle out of its niche in the seemingly secure Habitrail, escaped, found some colored tissue paper, tore off a 2 foot by 1/2 inch strip of white, and a similar strip of pink, took them back into the cage, and up to his bedroom chamber, where he installed them as decorations. Perhaps the most intelligent animals escape, go shopping, and come back. If they had internet and a credit card, would they just order stuff to be delivered? 24.13.87.201 (talk) 15:00, 8 July 2009 (UTC)

Massless patricles in quantum mechanics

Can they have 0 angular momentum? If not, which system has fewer degrees of freedom, a massless particle or a spinless one? 76.67.78.167 (talk) 04:58, 8 July 2009 (UTC)

According to our article on Spin (physics), photons have a spin and are massless. In fact, the same article notes that the only spinless particle in the Standard Model is the Higgs boson, which if it exists, definately has a mass. So, to answer your question, all particles in the standard model, even those which are massless, and even those which are point particles and lack internal structure or even volume, have spin, except for the Higgs, which has a mass but no spin. Of course, if it turns out that the Higgs does not exist, then the answer would be that all particles have a spin. --Jayron32.talk.contribs 05:04, 8 July 2009 (UTC)

I want to know if it is possible for a massless particle to have no spin, not just whether one exists. For example, it is impossible for a massless particle to have a speed lower than c, not because no massless particle with this ability is in the standard model, but because of special relativity. Does something similar rule out spin 0 massless particles, or are they theoretically possible? 76.67.78.167 (talk) 07:45, 8 July 2009 (UTC)

In today's quantum mechanics there is no rule forbidding the existence of spin 0 massless particles. In fact if you google the term "massless spin-zero" you will find several papers that either propose such particles or ways to detect them, should they exist.

But if it one day turns out that no massless spin-zero particles exist, there will hopefully be a theory explaining why it's impossible. EverGreg (talk) 08:03, 8 July 2009 (UTC)

What would the equivalent of the Dirac equation be for such a particle? Klein Gordon with m = 0? 76.67.79.118 (talk) 05:33, 9 July 2009 (UTC)

Goldstone bosons? JMiall₰ 08:14, 8 July 2009 (UTC)

Black or white aircraft paint?

I have a question that is (sorta-kinda) related to the question "Black or white parasol" in the science reference desk archives. This has to do with the paint job on the Lockheed SR-71 vs. that on the Concorde. You see, the SR-71 is painted a flat black (that's why they call it the Blackbird), while the Concorde is painted a glossy white. I was just wondering, which is a better choice for dissipating the heat generated by air friction and such during supersonic flight? Thanks, and clear skies to y'all! 76.21.37.87 (talk) 06:03, 8 July 2009 (UTC)

I'm not sure about the heat-reflective differences, but my understanding is that the reason the Blackbird is painted black is to help it hide from Radar. At least that's what I heard on some tv show. According to this (http://answers.yahoo.com/question/index?qid=20080604155845AA2TCgt) Yahoo answers the colour white is used to help facilitate ground-checks (though to be honest there's no more detail on how white iteslf helps do this) ny156uk (talk) 07:22, 8 July 2009 (UTC)

There could be a simple explanation. At [1] it says: White colors are much easier to cover with final topcoats. That is, it's easier to paint a logo or some pattern on the aircraft if you do it on a white background. When it comes to military crafts, the stealth aircraft article notes that F-22 was designed to be less visible to the naked eye. I guess dark colours play a part in that. EverGreg (talk) 07:49, 8 July 2009 (UTC)

The SR-71's black paint was selected primarily for its radar absorption properties. Stories about the thermal effects of the paint may have been injected as intentional misinformation to draw attention away from the "stealth" radar characteristics. It's worth noting that most of the useful stealthy characteristics come from the shape of the airframe, the engines, and the (minimal use of detectable) onboard electronics - so even the radar dissipating paint is itself sort of a red herring. Nimur (talk) 14:03, 8 July 2009 (UTC)

A physicist once told me that a steam radiator painted black would emit heat more efficiently than one painted white or silver. The SR-71 gets very hot from friction with the air at extreme speed. Would the black paint allow the heat to be radiated out better than a silver or white finish? Edison (talk) 15:35, 8 July 2009 (UTC)

Yes, in general darker colors have higher emissivity and better approximate a black body spectrum when heated, allowing them to dissipate energy by radiation more rapidly. Dragons flight (talk) 16:42, 8 July 2009 (UTC)

The curator at RAF Cosford told me that the BAC_TSR-2 was painted Anti-flash_white to protect the crew from A Bomb heat. I'm not convinced paint would protect you from a nuclear explosion. --TrogWoolley (talk) 21:54, 8 July 2009 (UTC)

All the V bombers were painted white for the same reason. MilborneOne (talk) 22:20, 8 July 2009 (UTC)

Yeah, I think paint would provide about as much protection as a school desk. Red Act (talk) 10:33, 9 July 2009 (UTC)

Thanks, Edison and Dragonsflight, you really answered my question from a physics point of view (BTW, my physics textbook also confirms that black paint radiates heat better). Now just one final point, it says in The Lore of Flight that the Concorde's white paint "reduces the temperature of certain areas [of the plane's airframe] by more than 10 degrees Centigrade", is that book just wrong about it, or are there some other heating effects (in the case of the Concorde but not the Blackbird) that are better countered by white paint? Thanks, and clear skies! 76.21.37.87 (talk) 09:26, 9 July 2009 (UTC)

Torque multiplication in a torque converter

How does it actually happen ? I fail to accept the explanation according to which the redirected oil flow (done by the stator) entering the impeller would do the trick, because it would only relieve the load on the engine and not transfer more force to the transmission.

My own guess is that there must be some kind of reaction force acting on the turbine in a similar manner as in a fire hose when the hose is opened at a close proximity to a solid wall.

Hope that someone with a scientific approach could shed some light on this phenomenon. —Preceding unsigned comment added by 193.210.65.69 (talk) 09:50, 8 July 2009 (UTC)

See Torque converter for more on this and it and the article has a link to howstuffworks. An interesting sort of related topic is torque amplifiers which I've made a couple of, they are used in power steering for instance. Dmcq (talk) 10:10, 8 July 2009 (UTC)

To quote the howstuffworks article: Modern torque converters can multiply the torque of the engine by two to three times. This effect only happens when the engine is turning much faster than the transmission. —Preceding unsigned comment added by EverGreg (talk • contribs) 10:14, 8 July 2009 (UTC)

Does fluid coupling make sense - they transmit torque, but do not multiply the torque, a very simple torque converter is just a fluid coupling with the output stage modified - see Fluid_coupling#Developments - if you don't understand fluid couplings then torque converters will be a mystery.83.100.250.79 (talk) 15:34, 8 July 2009 (UTC)

Remember that a fluid coupling is a torus - there are two types of fluid flow

• Going around the torus (ie like a wheel)
• Going around the circular segments of the torus (ie going around the circular cross sections)

It's the first that transfers the torque in a fluid coupling).

In a simple torque converter the stator redirects the second flow (using angled blades) so that some of its motion is converted to the first type of flow. (The turbine blades can also be angled, but it's unnecessary to imagine this for a simple explanation)

OF COURSE there is a reaction of the liquid flow on the output stage - this is how all fluid couplings and torque converters work fundamentally. ie if you point a fire hose at a shovel the shovel will be forced back by the water.

Definately read about simple fluid couplings first, before moving onto torque converters.83.100.250.79 (talk) 19:53, 8 July 2009 (UTC)

Does humidity affect hair growth?

I live in dry southern california, it's practically desert. A few times, I've traveled to other countries with much more humidity than where I normally live and notice that my hair (as well as my other family members) has grown faster during the time I've spent in this country. I don't know if I'm just imagining things or if humidity really does affect the speed of hair growth. On a related note, after removing a cast after a broken bone has healed will reveal that the hair on the skin below has grown considerably longer. Can this also be related to the dampness of the skin under the cast? -- penubag  (talk) 10:21, 8 July 2009 (UTC)

This is a fun thing to notice! :-) Hair actually expands in moist conditions and contract in dry ones. I've seen 3% being cited as a figure. If your hair is 30cm long, that should make for a difference in almost 1cm. This has been the basis for some hygrometers, which measure the humidity in air. EverGreg (talk) 10:36, 8 July 2009 (UTC)

Hmm, that is really interesting, perhaps that's what happens when I travel! But it doesn't answer my second question as to why hair grows long and dark under a cast.-- penubag  (talk) 11:02, 8 July 2009 (UTC)

No it dosn't. Though I suspect that if it seems dark, that's because it's in stronger contrast to the skin, which is paler after being covered in a cast. That it looks longer may be an optical illusion from the increased contrast. The hair on a stubbled chin is more prominent if it's black for instance. EverGreg (talk) 11:10, 8 July 2009 (UTC)

Nope, I guess you've never worn a cast (lucky you). It grows substantially longer while under the cast thus darkening as most longer pieces of hair do. -- penubag  (talk) 11:24, 8 July 2009 (UTC)

I suspect the difference is not in growths, but in life time. The cast protects the hair, so it will not fall out or break of as fast as on the unprotected skin. So you will have more and longer hairs, although none grows faster. --Stephan Schulz (talk) 14:21, 8 July 2009 (UTC)

The darker color might be due to it not being exposed to the bleaching effects of the sun. Grey hair has recently been identified as being caused by hydrogen peroxide accumulating in the hair. I don't know if it requires light to bleach hair, but that may also happen. 71.236.26.74 (talk) 15:27, 8 July 2009 (UTC)

Sunlight can certainly lighten hair. When a small boy I went (from the UK) to live in the much sunnier Far East for a few years; my normally dark blond/light brown hair turned very light blond for that period, but re-darkened on returning to Blighty. 87.81.230.195 (talk) 20:18, 8 July 2009 (UTC)

Glycerine + Ca(OH)2 ?

As I know, glycerine is hygroscopic and can absorb some quantity of water. What is the theoretical range of pH of this mixture? —Preceding unsigned comment added by Renaldas Kanarskas (talk • contribs) 12:42, 8 July 2009 (UTC)

I find it difficult to understand what you mean. Do you want to know what happens if you mix Calciumhydroxide with Glycerine (as the Title suggests) or what happenes if you mix it with Water (as the Text suggests). To find out about the pH of the resulting Mixture you simply need the pKs-Value/ pKa-Value of the Substance in question. In your case I just found the one of ethylene glycol, which already is 14.2 so considering the chemical relation between the two substances I would guess there is no big change in pH of the water whatsoever as glycerine should not be that easy to deprotonate. And of you mix it with a base you would either find that nothing happened, or you might create an Adduct depending on base strength. --91.6.6.157 (talk) 16:55, 8 July 2009 (UTC)

If I mix pure anydrous glycerine and CaOH2, I will not get any H+ and OH- ions because of anhydrous mixture. Glycerine absorb some water, I want to calculate pKa/pKb of this solution. Renaldas Kanarskas (talk) 22:45, 13 July 2009 (UTC)

Particles that are their own antiparticles and vice versa

How does this work? Neutral pions for example. Would two of them annihilate eachother when they get too close together? -- Aeluwas (talk) 12:43, 8 July 2009 (UTC)

It appears that it IS its own antiparticle, and "self-anihilates" all on its own. The quark structure of the pi-0 particle is listed in the article, which would also seem to indicate that it is clearly its own anti-particle. As with all aspects of quantum physics, try to suspend basic logic and reason when understanding how the system works. There are two possibilities here; either neutral pions do not exist, or your own understanding of the matter/antimatter interaction is flawed. Perhaps there is something in the pi-0 structure which makes it metastable; that is it probably doesn't exist for long, but it hangs around just long enough to prove that it exists. --Jayron32.talk.contribs 12:49, 8 July 2009 (UTC)

Things are simpler than Jayron32 presents them. A neutral pion consists of one quark and one anti-quark. It is therefore a composite of matter and antimatter and can annihilate itself. To dig deeper, the first thing to grasp onto here is the conservation laws. For instance the Charge conservation or more to the point, Baryon number conservation. The baryon number is the number of quarks minus the number of antiquarks divided by 3, so it's zero for the pion. Zero means it can evolve into something with zero quarks without breaking baryon number conservation. For the neutral pion the sum of the electric charge of the quarks sum to zero, so it's also ok to transform into something with no charge. (In fact, it couldn't be its own antiparticle if it had a nonzero charge, because particles and antiparticles have oppsite charges) In total, this means that the pion is allowed to transform into pure energy, or two photons to be precise:

π0

→

2 γ

It can however also transform into an electron and a positron since these too consists of no quarks and their electric charges sum to zero. Another particle which is its own antiparticle is the Z0 boson. Not surprisingly, this also has the ability to turn into photons, or pure energy:

Z

→

3 γ

EverGreg (talk) 13:27, 8 July 2009 (UTC)

To be super-precise, an antiparticle has the opposite charge of its corresponding particle. When you have zero charge, you can therefore be your own antiparticle :-) EverGreg (talk) 13:31, 8 July 2009 (UTC)

To be even more precise, a particle can only be its own antiparticle if all of its quantum numbers, including charge, are zero. A neutron is not its own antiparticle because its baryon number is not zero; a neutrino is not its own antiparticle because its lepton number is not zero. Gandalf61 (talk) 15:16, 8 July 2009 (UTC)

Gandalf, it is actually not yet known for a fact whether neutrinos are their own anti-particle or not. Lepton number conservation is not writen on stone. See majorana neutrinos. Dauto (talk) 18:33, 8 July 2009 (UTC)

Thanks guys, that clarifies it a bit. :) Especially "It is therefore a composite of matter and antimatter and can annihilate itself.".

I'm still confused about the whole pion as a strong force carrier, though. Particle physics is a very weird field. Are those pions there all the time (and add to the mass?!), or are they virtual, or what? :) -- Aeluwas (talk) 15:13, 8 July 2009 (UTC)

It seems as if the article about virtual particle semi-answers that question... not that I can say that I understand that it works. ;) -- Aeluwas (talk) 15:15, 8 July 2009 (UTC)

That is actually a confusing topic! Nobel prize winner Yukawa thought that the strong force was transmitted via pions. It is actually transmitted via gluons, but gluons can turn into quark-antiquark pairs, which is what pions are. These pions can in turn back into gluons. These constitute the sea quarks. So it's not completely wrong to say that the pion is involved. Yukawa's pion model has also been retained in nuclear physics as an approximaiton because it has been mathematically difficult to work with gluons alone, or so I've heard. EverGreg (talk) 18:31, 8 July 2009 (UTC)

EverGreg, There is nothing wrong with saying that pions transmit the strong force between the protons and neutrons inside a nucleus the same way that there is nothing wrong with saying that the nucleus is made of protons and neutrons. In fact, whenever dealing with sacales larger than the size of the nucleons, due to color confinement, the strong force is constrained to being transmitted by color singlets (white, if you will) which cannot be satisfyed by single gluons. The lightest color siglet particles are the pions and that's why they are indeed the most important component of the interaction between nucleons. Dauto (talk) 22:15, 9 July 2009 (UTC)

Good point! EverGreg (talk) 07:46, 10 July 2009 (UTC)

plasma

Can plasma movement in a theoretical pipe that plasma could not destroy be accurately modeled using fluid dynamics? 65.121.141.34 (talk) 16:08, 8 July 2009 (UTC)

Absolutely. Plasma is a fluid and as such obeys the Navier-Stokes equations. Readro (talk) 16:10, 8 July 2009 (UTC)

Because a plasma is an electrically conducting fluid, it is subject to electromagnetic forces, so you specifically need magnetohydrodynamics, a sub-field of fluid dynamics. Gandalf61 (talk) 16:28, 8 July 2009 (UTC)

Price of agricultural products

is there a direct correlation between price of agricultural product and growing time of its tree/plant? What are the most expensive agricultural products?--Quest09 (talk) 17:50, 8 July 2009 (UTC)

Saffron is one of the most expensive agricultural products—it's the most expensive spice by weight. I wonder if there are any pharmaceuticals that are derived from plants in tiny, expensive quantities? -- Coneslayer (talk) 17:56, 8 July 2009 (UTC)

Marijuana is a rather expensive agricultural product, and it is very fast growing. I think that the fact of it being illegal is the primary impact on its high price. I don't know how long it takes to grow the plants for cocaine. 65.121.141.34 (talk) 18:11, 8 July 2009 (UTC)

Were marijuana not illegal in many countries I have no doubt it would be much more expensive than tobacco. -RunningOnBrains^{(talk page)} 04:36, 9 July 2009 (UTC)

One would naively expect that the slower the plant grows, or the longer it takes to reach maturity, the more expensive would be its fruit (or, generally, any product obtained from it). That is true in some cases (walnuts, for example), but not in general. Prices are set by supply and demand, and the rate of the plant growth is just one of many factors. Some other factors that play a role are: 1. Desirability of the product (compare good Burgundy wine to cheap local one); 2. Legality of the product (see above); 3. Yield (roses are rather fast growing, but rose oil is very expensive nevertheless); 4. Ease of cultivation (e.g. truffles and brazil nuts). And there are more factors, of course. --Dr Dima (talk) 19:10, 8 July 2009 (UTC)

Perishability is a big one. Raspberries grow like weeds in my part of the world, yet they cost about US$16/lb for moldy ones at the grocer. --Sean 23:25, 8 July 2009 (UTC)

Some essential oils are amazingly expensive. This site claims that 7 tonnes of lemon balm are needed to produce 1 kilogramme of Melissa essential oil. [2] This site sells 1 kilogramme of Melissa essential oil for £1,800! [3] Some of the absolutes are even more expensive: 1kg of lotus (plant) absolute costs £5,900!--TammyMoet (talk) 19:26, 8 July 2009 (UTC)

The caveat in this analysis is that many of the incredibly expensive (per pure unit) things are used in only minute quantities (50 g leaves for melissa-based therapy at £1,800/7 tonne oil equivalent?), so the cost-per-enduser-product isn't so bad. Same pattern holds for API for pharmaceuticals...manufacturing price-per-truckload of the active ingredient might look huge but at only a few mg per dose the dose cost is reasonable. DMacks (talk) 21:07, 8 July 2009 (UTC)

Truffle (fungi)s can sell for a fortune. According to the article the record for a white-truffle was £165,000 for one that weighed 1.5kg. 22:37, 8 July 2009 (UTC)

banana plants take a long time to grow and only bear fruit once and then die off. They are a third world country product, though and economic pressures keep the price low. Some rain forest timber takes decades to grow but it doesn't fetch a fair price because it's not a "standard" species like oak or redwood. So world economy plays a role in pricing. 71.236.26.74 (talk) 04:50, 9 July 2009 (UTC)

"Some rain forest timber takes decades to grow but it doesn't fetch a fair price because it's not a "standard" species..." -- And what do you define as a "fair" price?

76.21.37.87 (talk) 10:20, 9 July 2009 (UTC)

Better than what it's fetching now at least. It is generally valued at less than "standard hardwoods" because consumers are not familiar with the names, etc. If you want to start a discussion on there not really being a "fair" price for cutting down a tree from a rainforest I don't think this is the place (but I happen to agree). 71.236.26.74 (talk) 14:40, 9 July 2009 (UTC)

The amount of time that a certain crop is in the field would be a factor in its price because of the opportunity cost of said crop taking up the space when another one, possibly faster growing, could be planted instead. —Preceding unsigned comment added by Frogmaster3950 (talk • contribs) 15:37, 10 July 2009 (UTC)

anchors and tides

If you have a boat and drop an anchor, and the tide goes up a lot, like 20+', will the anchor sink the boat if the anchor line was pretty taut at low tide? 65.121.141.34 (talk) 18:54, 8 July 2009 (UTC)

Only if the anchor weighed so much that it pulled the top of the ship's hull below the waterline - and that won't be the case, because the ship wouldn't ever be able to lift and carry its own anchor. Anchors don't rely on their mass (mostly), but on hooks or plates to catch the seabed; the weight of a heavy anchor is there only to help it bite into the seabed better. 87.113.26.43 (talk) 19:02, 8 July 2009 (UTC)

Well, it's possible that the anchor could get wedged under something really heavy and get stuck. However, even then, the anchor line/chain is likely to break before the boat could go under. As a practical matter, this is never an issue. Even with an all-chain anchor, good boating practice is to lay out enough chain to give a scope of about 7:1 -- translated, for every one foot of depth, you should have seven feet of anchor chain in the water. In adverse conditions, even more should be laid out. Consequently, you've always got far more chain in the water than the tide could impact. — Lomn 19:29, 8 July 2009 (UTC)

For interesting consequences of a (fictional) failure to do this, read We Didn't Mean to Go to Sea by Arthur Ransome. 87.81.230.195 (talk) 20:10, 8 July 2009 (UTC)

I've seen the opposite of that happen though - someone tied their boat to a jetty and the tide went out - initially lifting the boat out of the water - then ripping the fixtures that the ropes were tied to off of the deck - then finally allowing the boat to float away. SteveBaker (talk) 20:25, 8 July 2009 (UTC)

If an anchor chain is pulled to a vertical position by a rising tide, further rise of the water will pull the anchor free. In case any reader is a land lubber and does not know how anchors work, an anchor has a crossbar at the top, or in the case of a patent anchor it has flukes which are hinged at the bottom. Immediately after the anchor is dropped, the ship drifts a bit due to current or wind. The crossbar causes one of the flukes to be at an angle to the bottom. The drift causes the fluke to dig into the bottom (unless the bottom is rocky). Further drift causes the fluke to dig deeper until the ship is brought to a standstill. Obviously, the ship does not have to drift far for this to happen. In the case of a patent anchor, both flukes initially lie flat on the bottom. As the ship drifts, the weight of the flukes causes them to dig into the bottom. With either type of anchor, if the chain becomes vertical, further pull on the chain will lever the anchor out of the bottom (unless a fluke is hooked under a rock, as another poster pointed out.) The bottom is relatively soft – it had to be for a fluke to dig in. So the anchor can be levered out of the bottom. When pulled vertically, I don't think the chain is likely to break – it held the ship against drifting so it is not badly flawed.
The Wikipedia article for "anchor" is very poor. Also, the anchor shown in the illustrative photo seems to be without the essential crossbar.
GlowWorm. —Preceding unsigned comment added by 98.21.111.233 (talk) 01:04, 9 July 2009 (UTC)

The captain of this boat might not mind as long as it comes back up. [4] :-)71.236.26.74 (talk) 06:20, 9 July 2009 (UTC)

I don't think the captain even dropped the anchor. He should have done that before he got to the bridge. - GlowWorm. —Preceding unsigned comment added by 98.17.35.216 (talk) 03:58, 10 July 2009 (UTC)

Or maybe the anchor didn't have a crossbar. - GlowWorm.

On a practical front, sailors are taught to use a length of anchor rode (the technical word for the chains and ropes) between five and seven times the depth of the water, AND to take account of tide changes in the calculation. Most anchors will drag if the rode is much shorter than this. DJ Clayworth (talk) 18:23, 10 July 2009 (UTC)

B vitamins

NZ is currently planning to begin mandatory folic acid (vitamin B9) fortification of most bread. This has lead to a lot of debate and one of the issues which people have been saying on forums is that if you increase consumption of one B vitamin you need to increase them all or you risk deficiencies in the other B vitamins. This seemed strange to me and reviewing further I can't find any evidence of this being true. From what I can tell, the only currently known risk is between folic acid and vitamin B12. Specifically since the effects of these two are connected, taking extra folic acid may mask some of the symptoms of vitamin B12 deficiency (but it doesn't treat all the problems) so that it's not so obvious the person is suffering from it (it doesn't require you increase your vitamin B12 intake if it's sufficient). The evidence for this being a problem in the US and Canada who also have fortification however appears limited. There is also some more recent suggestion that a high folic acid intake and a low B12 may be bad and excess folic acid consumption "worsens the effects of B12 deficiency and in fact may affect the absorption of B12" (although I suspect this is talking about very high levels that your rather unlikely to get from fortified bread anyway). In particular, there's little evidence if you have a healthy/sufficient B12 intake, taking extra B9 suddenly requires you to increase B12 intake or any other of the B vitamins. Is there something I've missed or am I right that the claims about needing to increase all B vitamins are unsupported? Nil Einne (talk) 21:24, 8 July 2009 (UTC)

I have nothing to add beyond the B vitamins article, which I assume you've read, and which does mention that too-high doses of folic acid can mask a vitamin B12 deficiency. Tempshill (talk) 22:18, 8 July 2009 (UTC)

I guess one could counteract that by eating marmite on each slice of B9-fortified bread, since it is high in B12. Gwinva (talk) 22:53, 8 July 2009 (UTC)

Yes that and the Vitamin B article (as well as a quick Google) neither of which provide any real support for the notion other then what I mentioned. I normally would have dismissed the comments as 'ill-informed' (the place I read them isn't known for the high standard of debate [5]) but decided to check since more then one person made the claim. I presume they're confused by the B9-B12 issues as well as perhaps the general advice it's not wise to take excess of any vitamin and the general belief that improving one's diet and better food is better then supplements and fortification. Nil Einne (talk) 01:01, 9 July 2009 (UTC)

Ctenophores as human food source

It's frequently been suggested that we could adopt jellyfish as a food source once fish stocks are depleted, but could we do the same with ctenophores? Are they common and nutritious enough to make this idea viable? 69.224.113.202 (talk) 23:18, 8 July 2009 (UTC)

The main reason people eat meat rather than textured vegetable protein is palatability and "ick factor". I can hardly see either jellyfish or ctenophores overcoming either of those obstacles. The latter appear to be mostly water, anyway. --Sean 23:31, 8 July 2009 (UTC)

I've eaten jellyfish in Chinese restaurants -- I confess that I found it icky though. Looie496 (talk) 01:01, 9 July 2009 (UTC)

Jellyfish do contain nourishment. They are one of the food items of the ocean sunfish. Sadly, some of the sunfish are killed by swallowing one of those thin plastic bags, thinking it to be a jellyfish. Like other human castoff material, those bags even find their way into the sea. - GlowWorm. —Preceding unsigned comment added by 98.21.111.233 (talk) 01:33, 9 July 2009 (UTC)

Relatedness of species / Last common ancestor

Hi all,

I have a bit of confusion about species. I recently learned that if two species had a more recent common ancestor than either of them to a third species, then those two species are considered more closely related to each other than either is to the third species.

A       B   C
|       |   |
|       -----
|         |
-----------
     |

So B and C are "more closely related" than either is to A.

But what if A and B have barely evolved at all since their respective splits? Say the common ancestor at the bottom splits 100 million years ago and the resulting "A" branch doesn't change ever after (kind of like a crocodile). Soon after (95 m.y.a), the right lineage splits, and the resulting "B" branch doesn't change ever there after. The "C" branch, however, changes tons and tons, and all sorts of other species branch off of that last branch, and C is very, very different from its last common ancestor with B.

In this case, A and B are virtually identical -- they evolved from a LCA in just 5 million years apart and never changed. C is really, really different, though, and has millions of new genes. In this case, wouldn't A and B really be more closely related, even though B and C had the more recent common ancestor? —Preceding unsigned comment added by 76.118.181.97 (talk) 23:27, 8 July 2009 (UTC)

I believe you will find the answer in the definition of "more closely related". The assertion is correct if you mean more closely in time, and incorrect if you mean more closely in common genes. Avoiding this kind of discrepancy is why scientists talk like a bunch of nerds. --Sean 23:35, 8 July 2009 (UTC)

Both ways of describing how closely related species are are useful and so both are used. It's very common so see statements about what percentage of genes two species share (even that varies depending on your exact definitions). --Tango (talk) 00:53, 9 July 2009 (UTC)

The use of the term "closely related" is used pretty much exactly like it is in your family tree; just because your second cousin look a lot like you doesn't make him more closely related to you than your sister. You may also find the article on convergent evolution to be germane; it is often the case that even totally unrelated organisms can look similar due to being exposed to similar environmental pressures. Matt Deres (talk) 01:42, 9 July 2009 (UTC)

There are almost certainly genes that B and C share that A doesn't have...that makes them (genetically) more closely related than A and B. SteveBaker (talk) 02:38, 9 July 2009 (UTC)

The diagram you gave (as described) was only the qualitative branching. You can make it more quantitative to illustrate the amount of evolutionary change ("...and then C evolves much further while A and B did not change much or diverge very far"):

        C
        |
        |
        |
        |
        |
        |
    B   |
    |   |
A   -----
|     |
-------
   |

and now it's more clear that while B and A are more diverged from each other than B and C are, C has evolved further from A than B has. See our Phylogenetic tree article for several different types of representations (with actual diagrams vs our quick'n'dirty ASCII art:) DMacks (talk) 07:35, 9 July 2009 (UTC)