Wikipedia:Reference desk/Archives/Science/2008 December 7

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December 7

Electric Tooth Brush

I have a couple of questions regarding these tooth brushes: does their effectiveness correlate with their frequency?

• would it make sense to design a tooth brush that made the teeth resonate, or would it damage the teeth? Soap (talk) 00:13, 7 December 2008 (UTC)

I don't know about effectiveness - but you couldn't design something like that. No two teeth are the same size or shape - so the resonant frequency of each tooth would be different. SteveBaker (talk) 02:11, 7 December 2008 (UTC)

Some frequency searching feedback could fix that - talk about having a tune on your mind! -hydnjo talk 03:06, 7 December 2008 (UTC)

Probably a small hammer that would hit the tooth and measure the resonating frequency would do that right? Assuming it is practical, would it make sense to design it?77.243.73.133 (talk) 11:30, 7 December 2008 (UTC)

Putting aside the fact that hitting your teeth with a small automated hammer may not be all that healthy, I don't think there's any particular benefits to a resonating toothbrush. Their purpose is to remove unwanted substances from the surface of the tooth, so causing the tooth itself to vibrate doesn't sound very necessary. There will definitely be a correlation between frequency and effectiveness, but it's more to do with finding a balance between swiftly removing plaque in the limited period the user is touching a particular tooth, but not having the toothbrush blasting away so fast it wears down the teeth or damages the gums. ~ mazca ^t|c 12:33, 7 December 2008 (UTC)

Rare meat

Why does rare meat taste so much better than well-done? Or rather, as de gustibus non est disputandem, what chemical changes account for the difference in taste between rare and well done meat? DuncanHill (talk) 00:18, 7 December 2008 (UTC)

Blood. You are experiencing a pleasure in the taste of fresh blood. I do not know if this is any good an answer for you but certainly you will find more blood in your raw flesh than in your burnt one. ~ R.T.G 01:24, 7 December 2008 (UTC)

I like cooked blood too. DuncanHill (talk) 01:25, 7 December 2008 (UTC)

My understanding is that the red stuff that comes out of a rare steak is not actually blood (the animal is bled before butchering), but a thin fluid of proteins leaching from the muscle tissue. I don't have a specific cite handy, but I heard it on Good Eats, which is unusually fact-based for a food show. Matt Deres (talk) 02:13, 7 December 2008 (UTC)

The red stuff is Myoglobin, here's a book source about the flavor part. -hydnjo talk 02:36, 7 December 2008 (UTC)

Yeah, the red stuff is definately not blood. Blood isn't found spread evenly among all of your tissues; its pretty well confined to things called veins and arteries. There is no blood inside of your muscle tissues. Blood is also pretty terrible for the flavor of meat; if it is not quickly drained, and it does enter the meat, it pretty much ruins it. The red stuff is just the stuff that makes muscles red in general; as noted above, its myoglobin. --Jayron32.talk.contribs 03:14, 7 December 2008 (UTC)

The red color of meat is certainly caused by the myoglobin (and that also explains why chicken isn't bright red) - but "There is no blood inside your muscle tissues"??? Er...are you sure about that? Our article on muscle says that they are "densely" suffused with capillaries - and the article on capillaries says that they carry blood. So there ought to be a fair bit of blood in muscle - and hence in meat from an un-bled animal...but I'm no biologist - I could be wrong. SteveBaker (talk) 05:34, 7 December 2008 (UTC)

Capillaries will have blood in them. Whether you consider them part of the muscle tissue or seperate may vary Nil Einne (talk) 09:02, 7 December 2008 (UTC)

OK, nice semantics - but they are definitely a part of the steak - some of them are so fine that red blood cells have to fold up to get through them...there is absolutely no way you could dissect them out during butchering! I doubt very much that 'bleeding' the animal after slaughter would drain those teeny tiny tubes - so we may safely deduce that there IS blood in steak. SteveBaker (talk) 02:49, 8 December 2008 (UTC)

Would that work with meat that is frozen almost as soon as it's killed or eaten fresh without being drained? We never drain anything and it never tastes odd. CambridgeBayWeather Have a gorilla 04:57, 7 December 2008 (UTC)

You hunt meat, kill it, and then don't drain the blood? Really? --Jayron32.talk.contribs 05:31, 7 December 2008 (UTC)

While today you might be able to get back to town and find a heated area to drain it before the meat freezes, in older times that would not have been possible, it's unlikely that you would get back quick enough. CambridgeBayWeather Have a gorilla 06:59, 7 December 2008 (UTC)

Why do you need to find a heated area? You can drain blood rather fast if you adopt the Muslim/halal method of killing an animal. (If you kill the animal while hunting that won't be possible but I'm pretty sure traditionally people would have been far more likely to wound rather then immedietly kill an animal. Arrows, spears and the like aren't going to guarantee and immediate kill.) Unless you are living in liquid nitrogen, the animal is not going to die that fast Nil Einne (talk) 08:56, 7 December 2008 (UTC)

Did you mean dhabihah rather than halal? To do that would you not need to be able to catch the animal first? It would seem to me that wrestling with a wounded muskox or even a caribo and trying to cut it's throat is going to be a problem. Still the animals were never (and still aren't) drained prior to eating. CambridgeBayWeather Have a gorilla 12:13, 7 December 2008 (UTC)

No I did mean halal. Dhabiha methos of slaughter is generally compulsory for halal meat for many Muslims. Anyway ignoring the semantics for now, I disagree it's going to be a big problem. Ultimately you have to kill the animal. Whether you slit it's throat (note it could be a spear or whatver, it doesn't have to be a knife) or try to stab its heart, both obviously require some skill but aren't not going to be that hard if you're used to that sort of thing. Otherwise humans would never have succeeded at hunting Nil Einne (talk) 15:54, 14 December 2008 (UTC)

I should note that not everyone prefers rare meat Nil Einne (talk) 08:57, 7 December 2008 (UTC)

A few notes from a cooking point of view. Many people like a rare steak. In this case the outside of the meat is cooked very quickly and the sugars undergo caramelisation. The taste mixes salt and sweet, which is generally pleasant. I expect there is umami involved as well. There is also an agreeable contrast between the crispy outside and soft middle of the steak. Let's also consider the counterfactual: long-cooked meat. If you cook a steak for a long time it may become tough and rubbery. However, some cuts of meat respond very well to slow cooking. Often we sear the meat first, to achieve the caramelisation, then add liquid (water, stock, wine, beer etc.) and cook slowly for hours. The meat becomes fibrous but not dry. The taste of the meat is transferred to the liquid and any vegetables that are included. Itsmejudith (talk) 12:55, 7 December 2008 (UTC)

Many thanks to you all - some fascinating stuff. DuncanHill (talk) 12:59, 7 December 2008 (UTC)

And given CambridgeBayWeather's very high latitude, where the average low is below -10ºC all year long, I'd guess that the meat and its blood would freeze rather rapidly if you didn't find a heated area. Nyttend (talk) 14:49, 7 December 2008 (UTC)

Whoops, I probably should have indicated that I live in Cambridge Bay, Nunavut and the mean daily average is −14 °C (7 °F). Sorry for any confusion. CambridgeBayWeather Have a gorilla 22:50, 7 December 2008 (UTC)

In the old days of farming, a farmer would kill hogs when the temperature dropped cold enough to preserve the meat but perhaps not way below freezing [1]. The animals throat would be cut and he would be hoisted by his hind feet to drain the blood within a couple of minutes. I don't see why that wouldn't be desirable for a deer as well. Field dressing [2] should get rid of the blood as well as speeding the cooling of the meat. Edison (talk) 03:51, 8 December 2008 (UTC)

All of that seems to involve the hanging of the animal but without trees that's not practical. Anyway, the thing is that we don't drain the blood and the animals taste fine, which seems to contradict with the earlier comment. CambridgeBayWeather Have a gorilla 06:44, 8 December 2008 (UTC)

"Globin" such as "myoglobin" and "haemoglobin", is a word used to describe blood cells, one is red, one is white. They contain stuff like salt, sugar, iron, etc. The red colour is partly caused by the iron, which in its natural form is pure rust or red rock, is the building block (a magnet) upon which oxygen is carried throughout the body therefore being well spread in a length of veins long enough to reach around the planet several times (that much veins must go into muscles or something) and being several six inch nails worth in a human body and as may be known has a strong taste. Salt, its very important, you are stuffed with it, what it does I do not recall, it has a strong taste. Sugar, again you are packed out with the stuff. It is the coal for you fire. It is the acid by which your blood and stomach burn. It burns the food and lets off the gas and steam and again it has a quite strong taste. Unfortunately what is sad but true after this point is that other stuff with a strong taste in its basic element sort of goes as far as calcium, clorophyll (or whatever gives that green taste), and narcotic tasting stuff like caffine and aspirin which tastes more alike the more pure it is. It's all sugar, salt and steel. Even natural flammable gas has no smell or taste. The smell is added so that if you are about to suffocate or set it on fire you have some sort of warning. Even when making soya milk it tastes pretty much like carboard unless they add calcium, salt and sugar (or apple juice which is common in the tastier stuff). Tastes pretty much like milk but is basically that same old stuff you are tasting. Ask any chef what is most important in a good meal... colour and presentation. What do they make fake meat out of? Corn. Can they make it taste like real flesh? Little fatty bits and all. Yik. ~ R.T.G 19:23, 8 December 2008 (UTC)

Um quite a bit of what you're saying is wrong. For example, I never, ever heard someone call Myoglobin a 'blood cell' in my 4 years at university doing biology which isn't surprising given that it isn't found in the blood. Nor have I ever heard some call myoglobin a white blood cell which isn't surprising since besides the aforementioned reason myoglobin when oxygenated is generally red (or brown) as with haemoglobin. BTW, the vast majority of Meat analogue is made with soyabean and sometimes a variety of legumes like chickpeas not corn. Nil Einne (talk) 16:01, 14 December 2008 (UTC)

Natural orbitational phenomenon

As in the orbitational phenomenon. What are the odds? Lets say you could remove the moon to outside the system and send it toward the Earth repeatedly on random courses until you got a stable orbit. What are the odds? Would the time scale of orbitational phenomenon occuring naturally fit in with the time scale of the orbital decay (or opposite) of the celestial bodies we have in the system now? i.e. the moon and other orbiting stuff will eventually crash or fly away... will this happen so slowly as new similar sized bodies will find such orbits before they do? Is there any known records of anything like a comet or a meteor that flew into a new orbit in our solar system? Any comets or meteors been recorded which are not beleived to have some sort of orbit in our system? ~ R.T.G 01:20, 7 December 2008 (UTC)

When looking for the likelihood that something the size of the moon would get "caught" in the orbit of earth you'd have to acknowledge that the moon didn't likely come towards the earth and then get caught in orbit (Giant impact hypothesis). Now if someone can try to do some math to give you a real answer, that'd be impressive. Chris M. (talk) 02:04, 7 December 2008 (UTC)

It's not a matter of statistics...it's not possible. SteveBaker (talk) 02:09, 7 December 2008 (UTC)

"orbitational" isn't a word. I guess you're asking how the earth could have 'captured' the moon? The answer is that it couldn't. There is no course that the moon could arrive along that wouldn't result in it shooting off back out into space - or crashing into the earth. But you should read our article on the Moon#Formation - it explains that the 'capture hypothesis' doesn't work. The generally accepted theory is that another planet collided with the earth and the moon was formed from material ejected from the collision. The moon's current orbit isn't 100% stable - it will gradually move further from the earth. This applies to other objects heading towards the earth - they'd have to find some means to lose exactly the right amount of energy as they arrived in order to make a stable orbit. Notice how our spacecraft heading into orbit around other planets have to use an 'orbital injection burn' of their engines - or use the drag of the atmosphere of the planet - to lose some energy and make a stable orbit. Meteors and comets don't have energy - so atmospheric drag is the only way to get into orbit...and an incoming moon would need to shed far too much energy for that to work. SteveBaker (talk) 02:09, 7 December 2008 (UTC)

But the need to slow down is because the spacecraft is going so fast. If an object approached the Earth at a lower speed, essentially tangent to the Earth's orbit about the Sun, it might be possible for it to fall into a stable orbit. Certainly not a likely scenario with an object the size of the Moon, but still possible, I suppose. StuRat (talk) 04:35, 7 December 2008 (UTC)

Nope - no matter how close to the correct orbital velocity you were going (Remember: velocity means speed and direction), you couldn't be at the exact correct velocity without already being in orbit. Hence you either have to gain or lose energy from somewhere...which means that you need either some engines, sufficient drag through the atmosphere or some third body to shed the excess energy into. SteveBaker (talk) 05:19, 7 December 2008 (UTC)

You talk as if there is only one possible orbit. Aren't there an infinite number of orbits at different distances (and subsequently speeds) from the Earth ? And, therefore, won't a body moving in a certain range of speeds naturally move into a stable orbit by either getting closer to, or farther from, the Earth ? StuRat (talk) 23:03, 7 December 2008 (UTC)

No. Conservation of energy means an object has the same amount of total energy (potential+kinetic) at all points in its orbit, either that is enough energy for it to escape or it isn't. You can't move from one type of orbit to another without a change in total energy. One way to look at it is to realise that the laws of gravity are completely time symmetric, so if it is possible to go from a hyperbolic orbit to an elliptical one, it is possible to do the reverse - that means you can break orbit without needing to fire your rockets, which is clearly not true. --Tango (talk) 23:29, 7 December 2008 (UTC)

Ah! Thanks Tango! That's an elegant way of saying what I was trying to get across. Time symmetry...yeah. SteveBaker (talk) 02:34, 8 December 2008 (UTC)

Ok, so let's say the Moon's orbital velocity (at one point in it's orbit) is now X. You're saying that, if the Earth didn't have a Moon, and an object identical to the Moon approached the Earth at tangent to the Moon's orbit, but at a velocity of 0.999999999999 X or 1.000000000001 X, that instead of settling into a slightly higher or lower orbit, the Moon would fly off into space or crash into the Earth ? I find that impossible to believe. Orbits aren't that unstable. If so, then when some ancient meteor hit the Moon and increased or decreased it's velocity that much, it would have been knocked out of orbit, too. StuRat (talk) 14:51, 8 December 2008 (UTC)

If an object were at that speed in that position then it would already be in orbit. You can't get from a long way from Earth to a lunar distance from Earth without the Earth's gravity accelerating you (we call moving towards a massive object due to gravity "falling") so you would be at a too great a speed to be captured. --Tango (talk) 15:19, 8 December 2008 (UTC)

Escape speed at a given distance is √2 times the speed of a circular orbit at that distance, by the way. (In a Newtonian universe; near a black hole that's likely off.) —Tamfang (talk) 08:44, 14 December 2008 (UTC)

Quibble: velocity means speed and direction, yes, but direction isn't important here: if the kinetic energy is less than (the absolute value of) the gravitational potential energy, the body is in orbit, no matter which way it's going. —Tamfang (talk) 08:44, 14 December 2008 (UTC)

To expand a little of SteveBaker's excellent answer; orbital capture COULD theoretically work for a small chunk of rock that happened to hit the atmosphere at just the right angle and slowed down to exactly the right speed. The main problem with the moon is that its, and this is a scientific term, pretty friggin huge. With the exception of the now-demoted "Pluto" system, the Earth-Moon system represents the closest in size between a satelite and a planet in the solar system, by far. The moon is about 2% the size of earth; no other satelite is even CLOSE to being that large relative to its planet. Orbital capture works; but not for something that size... --Jayron32.talk.contribs 02:50, 7 December 2008 (UTC)

Actually, it might be possible to capture a moon-sized object by gravitationally scattering it off of our existing moon-sized object. An incoming planetoid with just a little more energy than escape velocity might be captured if it transfered enough energy to our existing moon. Of course, that would leave both objects in eccentric and probably unstable orbits, but why be picky. Dragons flight (talk) 03:32, 7 December 2008 (UTC)

Yep - but the idea that our moon could simply be free-falling through space, pass close to the earth and be "captured" is a mathematical impossibility. That's why this theory for the formation of the moon has been dismissed these days. SteveBaker (talk) 05:19, 7 December 2008 (UTC)

So how do the theories that certain moons of other planets were captured work? Do they rely on the other moons or nearby planets? I can see why in the 2-body problem you can't go from an escape orbit to a periodic one without a change in energy, but it must happen somehow. --Tango (talk) 13:55, 7 December 2008 (UTC)

It's only a mathematical impossibility in the 2-body point mass (or rigid ball) model. While it's unlikely, the gravitational influence of the Sun could change the velocities by the right amount, see Interplanetary Transport Network. I think at least theoretically there could be a situation where tidal forces slow down a moon while it is passing close to the planet and make the orbit more stable (but the evolution of such a orbit wouldn't fit to the current orbit of Earth's Moon). Icek (talk) 15:00, 7 December 2008 (UTC)

Great answers! The collision idea is easier to visualise. It also gave me an idea to support it I think... all of the Suns orbiting bodies are more or less in a disc formation. Perhaps this is the angle at which large stuff is more likely to bounce off and find an orbit. I must agree that thinking about how an object would hit an atmosphere sounds more likely to make it curve. Also given the fact about the moons size and its relationship to life here (it provides the tide and hence the beat) its a pity we can't compare similar systems. I have seen a few pics on TV of a comet which hit Jupiter or Saturn but that is the only mention of something large hitting the gravity of a planet I can recall and funny enough as it left a large mark (i cant rememer which planet but it was a gas giant, Jupiter I would beleive) the comet bounced like a skimming stone not just leaving one mark but a row of marks where it bounced, another collision supporting evidence too. ~ R.T.G 01:58, 8 December 2008 (UTC)

BUT... if the Moon hit the Earth causing the orbit... isnt the Earth on a stable orbit? Wouldn't the collision of the Moon cause the two bodies to orbit each other rather than one orbiting the other? I guess the Earth could have been stabilised by the Moon colliding but is that any more likely than them just happening on their orbits without colliding? ~ R.T.G 02:04, 8 December 2008 (UTC)

The earth and moon DO orbit each other. The point about which they both rotate is somewhere beneath the surface of the earth - about a third of the way down to the center. Technically - the moon didn't hit the earth. Some other small planet (called 'Theia - perhaps the size of Mars) hit the earth - the resulting energy would have forced a blob of molten matter to spirt out of the opposite side - and billions of tons of debris to be shot into orbit - rapidly forming a disk (like the rings of Saturn). Gradually, the material in the rings would clump together making a larger and larger body - which eventually consumed all of the ring material. THAT is the moon. Our article Giant impact hypothesis explains the currently prevailing theory. SteveBaker (talk) 02:34, 8 December 2008 (UTC)

The Comet that hit Jupiter was Shoemaker-Levy. It didn't bounce. The reason we saw a series of collision points was that the comet broke up (prior to collision), due to tidal forces.Bunthorne (talk) 07:49, 8 December 2008 (UTC)

That theory of Giant impact hypothesis sounds good for most part but I don't understand the pictures where the theia object moves backwards and forwards or in a sort of a squiggle shape...? Don't cellestial bodies travel in straight lines or perfect curves? And, if the moon was definitely a ring but definitely only for a hundred years... what is going on with Saturns rings? ~ R.T.G 18:45, 8 December 2008 (UTC)

The picture was probably centred on Earth rather than the Sun, so the weird path is combination of the (roughly) perfect curves of the Earth and Theia. As for Saturn's rings, nobody is entirely sure, but it may be to do with its moons preventing coalescence. --Tango (talk) 01:00, 9 December 2008 (UTC)

No, they are all pictures of the Earths orbit around the Sun and at least 3 of them show Theia moving on a random path, including making about ten percent orbit on Earths orbital line then doubling back and repeating that a few times before smashing in to the Earth instead. Maybe its just some vandalism for a laugh but some effort has been made. ~ R.T.G 02:30, 9 December 2008 (UTC)

Actually, I think the theory of how Saturns rings stay put is becoming pretty well developed - there are multiple causes of their stability - and it seems they all conspire to create the unusual density, structure and longevity of Saturns' ring system. The moons that stop the rings from coalescing - yet give them such defined structure are called 'Shepherd moons'. There has even been a recent discovery of rings around one of Saturn's moons (See: Rings of Rhea)...this is amazingly cool! SteveBaker (talk) 02:40, 9 December 2008 (UTC)

I seem to remember reading something not too long ago about an attempt to model Saturn's rings and it didn't work, they couldn't get them stable over long periods (it's possible they simply aren't stable over long periods and we're just lucky to be born at a time when they are there). --Tango (talk) 13:40, 9 December 2008 (UTC)

If you look at the animated image you'll see the Earth is staying still, whereas we know it's actually orbiting the sun, the the image is being rotated as you watch it to compensate for the Earth's movement. The movement of Theia combined with that rotation of the image is what gives the weird shape. --Tango (talk) 13:40, 9 December 2008 (UTC)

Tango, if you can't see something unusual about the Theia trajectory... also regarding the lucky timing of the rings, Jupiter, Saturn, Neptune and one of Saturns moons all have rings although only Neptune and Saturns are easy to see. Planetary rings ~ R.T.G 00:17, 10 December 2008 (UTC)

Well, its trajectory isn't a standard elliptical orbit because of the influence of Earth's gravity, but it's not far off. It just goes a little faster or slower than you would otherwise expect at certain points, which causes it to either catch up with the Earth or fall behind it. --Tango (talk) 00:38, 10 December 2008 (UTC)

Comet Shoemaker-Levy 9 illustrates something said earlier, that tidal forces may cause capture. During the two years before impact, the comet fragments orbited Jupiter (in a very eccentric ellipse). I'd guess that some other fragments escaped. —Tamfang (talk) 08:44, 14 December 2008 (UTC)

nepeta

Catmint and catnip seem to be used interchangably. Catmint is 'nepeta mussinii' and catnipt is 'nepeta cataria'. Cat have quite different reactions to each. Can that entry be refined?

Goetzds (talk) 01:28, 7 December 2008 (UTC)

Wikipedia: The encyclopedia you can edit! SteveBaker (talk) 01:54, 7 December 2008 (UTC)

Ouch! hydnjo talk 02:26, 7 December 2008 (UTC)

WP:SOFIXIT is the link you were looking for... --Jayron32.talk.contribs 02:44, 7 December 2008 (UTC)

Why do CFL bulbs take a while to reach full brightness?

Why do Compact Fluorescent Lights take a few minutes to "warm up" to full brightness? Incandescent bulbs seems to reach full intensity instantly. --69.149.213.144 (talk) 03:34, 7 December 2008 (UTC)

I think it is literally because they need to warm up. That is, they work better once they reach optimal temperature, much like a car. Not all compact fluorescent lights have this deficiency, however, or at least not to the same extent. Regular incandescent bulbs need to warm up, too. The difference is that they warm up in a fraction of a second, because they are so much less efficient, and that wasted energy all produces heat. StuRat (talk) 04:25, 7 December 2008 (UTC)

Fluorescent lamp is a bit technical, but has more details. 76.97.245.5 (talk) 05:05, 7 December 2008 (UTC)

In that article, it isn't really so clear that there is a difference between the types of ballast. I guess that your CFLs just happen to be older and still have magnetic ballasts (a.k.a. "reactive ballasts"). (Thanks for being an early adopter!) New CFLs should have electronic ballasts and start up just as fast. This is a little bit better described at Electrical ballast — Sebastian 09:17, 7 December 2008 (UTC)

I don't think the OP is talking about start up time but warm up time. As in the CFL has started but is not that bright Nil Einne (talk) 11:29, 7 December 2008 (UTC)

That's correct. They all turn on instantly (no flickering or delay), but are rather dim for the first few minutes. (I think CFLs are too small for magnetic ballasts anyway, no?) --69.149.213.144 (talk) 13:47, 7 December 2008 (UTC)

My suggestion, give those old CFLs to a heavy drinker, as a light that starts out dim will be less shocking to them during hangovers. StuRat (talk) 22:40, 7 December 2008 (UTC)

Light bulbs work by making something white hot. In your older light bulbs this is a hair thickness piece of metal which even the flame of a match would burn through. It is specially sealed so that it doesnt burn itself out. In a flourescent bulb is a gas which doesnt need to be so hot to reach white hot intensity. Compare it to the movie special effects trick for making a person appear to be on fire. The stuff used doesnt burn at such a high temperature as most fire but does burn hot. So, your flourescent bulb heats up a gas and even though it requires less heat, it still is hot and to heat the whole chunk of gas to white hot in one instant would probably give you an explosion. The electricity only provides heat and the whole inside of the CFL bulb lights up not just a little strand of metal. ~ R.T.G 23:14, 8 December 2008 (UTC)

According to Wikipedia there is such a thing as flourescent lighting that starts instantly ~ R.T.G 02:58, 9 December 2008 (UTC)

What puts the fluorescence in fluorescent lights?

What are the most common phosphors in commonly available fluorescent lights? Dragons flight (talk) 04:42, 7 December 2008 (UTC)

Have you actually read the fluorescent light article you linked to? There is copious information about the phosphors there. SteveBaker (talk) 05:08, 7 December 2008 (UTC)

There is some information, but most of it is not very specific (e.g. which Eu and Tb compounds?) and does a poor job of distinguishing what are the most common (as opposed to listing what is merely possible). I'd like to know which specific compounds are the most significant on the market today. Dragons flight (talk) 05:35, 7 December 2008 (UTC)

The article seemed pretty darned specific to me...the section Flourescent_light#Phosphor_composition says that the most common lamps use rare-earth doped phosphors - and provides a labelled spectrum of the light (Image:Fluorescent_lighting_spectrum_peaks_labelled.gif) - which (if you scroll down a bit from the image) lists the chemical composition of the phosphor corresponding to each peak. You won't do better than that because (as the article explains at some length) each tube manufacturer will tweak the mix of phosphors to get the exact most pleasing/natural color they feel is right. SteveBaker (talk) 06:04, 7 December 2008 (UTC)

Steve, I'm not sure if you intended to link to the spectrum image or not but incase you're not ware, if you want to link to an image without it appearing in the page you can use [[:Image:Cat.jpg]] Image:Cat.jpg (wow that actually exists) Nil Einne (talk) 08:51, 7 December 2008 (UTC)

(fixed!) Ooops! Yes, I knew - I was just being yelled at to "get away from that damned computer and do {somethingorother}" which broke my concentration. Sorry! SteveBaker (talk) 02:16, 8 December 2008 (UTC)

making Part II

Thank you for the information. However, some of it was a little too complicated for me. Let me ask another question.

Let's say I want to make Zestril (Lisinopril), a high blood pplyssure medication. Would I start with, say a plant (or some other natural being), then alter the chemical make up to create a substance. Then add several other products, chemicals, heat, transfer of the product to make a drip, then alter the drip to make another product, etc....In the end I would have Zestril.

What I want to know is what kind of initial product or plant would you start with? I'm talking all drugs, I just used Zestril as an example. I hope the question makes sense. —Preceding unsigned comment added by JelloTube (talk • contribs) 10:22, 7 December 2008 (UTC)

We don't know how to quickly select the initial product/plant to start with in drug discovery and only find out the right one via clinical tests. To compensate with the lack of data we try to obtain as much samples as possible of anything which have promising effects (for example a plant was used by native inhabitants to alleviate muscle pain while another mushroom is rumoured to have the same effect). The selection process are usually done through in toxicity and dosage tests in cell tissue, Animal testing and finally Clinical trials. Anything with adverse reactions or have nasty side effects will be removed. If we're lucky, probably out of 10,000 initial samples will yield one or two viable substances for drug use (and we have to monitor the long-term effect of that drug). This process is extremely long and expensive costing millions of dollars and years.--Lenticel ^(talk) 12:40, 7 December 2008 (UTC)

Lenticel is referring to the selection/discovery of the drug, but if you already know the chemical and just want to synthesize it then it would be a good idea to read the patent! Drugs are usually protected by patents, and in order to get patent protection you have to publish details of the chemical process. E. g. go to http://www.google.com/patents/ and enter "lisinopril", and one of the results is Process for the preparation of 1-(N 2-(S)-ethoxycarbonyl)--3 phenylpropyl-N6-trifluoroacetyl.... - just click on "Read this patent" and there it is. You'll probably have to do further research on cited prior art in order to find out how to make the direct precursors.

By the way, Zestril is not the same as lisinopril; the latter is one chemical, the former is a whole medical preparation containing the chemical. Icek (talk) 13:37, 7 December 2008 (UTC)

OK, a simple answer: You can buy chemicals at all levels of complexity, check Sigma Aldrich, a company that sells literally millions of different chemicals. Some are isolated from plants or other living sources, some are derived from petrol, but most are have been synthesized from these by chemical synthesis. It works like a construction kit - you assemble assemble building blocks and add molecular features. Chemist learn the rules for this game and if a chemical synthesis has been published then you can repeat the sequence. Cacycle (talk) 03:26, 8 December 2008 (UTC)

Thank you. All these were helpful. I've just always wondered how the complicated world of medications began. —Preceding unsigned comment added by JelloTube (talk • contribs) 08:44, 8 December 2008 (UTC)

Asking the gods of science for some help.

A member of my family is going to attent a game show of this format http://en.wikipedia.org/wiki/Deal_or_No_Deal

There are 22 boxes with progressively larger ammonts of cash in each box. I would like to ask if there are any factors which can give an advantage (something similar to monthy hall problem), something to increase the probability of winning?. —Preceding unsigned comment added by 77.243.73.133 (talk) 14:13, 7 December 2008 (UTC)

How much will I get if I tell you? Icek (talk) 14:31, 7 December 2008 (UTC)

The strategy is relatively simple: Keep track of which amounts are removed. When asked whether you quit, compute the average of the remaining amounts - that's the expectancy of what is in your box. If the amount you are offered is greater than or equal to the average, then quit, else continue. Icek (talk) 14:36, 7 December 2008 (UTC)

I think the traditional and most effective method is to sleep with the producer - but there may be ethical, moral, and sexual compatibility problems with this approach. DuncanHill (talk) 14:38, 7 December 2008 (UTC)

This has been asked on both the maths ref desk and here... interestingly the maths ref desk has produced far more constructive answers - take from that what you will! (Oh, and to the asker - please don't cross-post in future, it just ends up with effort being split.) --Tango (talk) 14:42, 7 December 2008 (UTC)

But, being on the Science Ref Desk, perhaps we should go beyond the simple mathematics of probability. For example, if offered either 100 million dollars or a 1 in 2 chance at 1 billion, just about everyone would take the sure thing, even though, on average, the gamble will pay better. StuRat (talk) 22:35, 7 December 2008 (UTC)

Calculating an average of the contents of the remaining boxes in the stress and pressure of the show may be unrealistic (at least until there are just a couple of boxes left). The likelyhood of making a slip in your mental math under the hot lights and with the adrenaline pumping is HUGE. What is needed is an algorithm that improves your odds AND which is really easy to remember and apply under pressure. I recommend sitting down with family members and picking a dollar amount that represents the amount of money that'll make a big difference to your life - an amount you would not be disappointed to walk away with. Let's say that amount is $20k. Now, instead of calculating an average - just add up the number of boxes that'll "make a difference" and the number that won't. If the offer they make you "makes a difference" and less than half of the boxes "make a difference" then take the offer - otherwise turn it down. If the offer they make doesn't "make a difference" turn it down unless none of the boxes make a difference either. This is a simple enough rule to keep in your head under pressure. This approach doesn't maximise your expected dollar return - but it does maximise the chances of you walking away with a huge smile on your face - which matters more IMHO. I very much doubt that (walking out of the studio) you'll very much care whether you won $100k or $200k. Considering the amount of money at risk here - you might want to consider getting someone to write a computer program to simulate various strategies so you can test them out. SteveBaker (talk) 02:12, 8 December 2008 (UTC)

Indeed, my answer on the Maths desk accounted for that. (It's a consequence of the diminishing marginal utility of money combined with the need for a risk premium. The additional utility of the extra 900 million is pretty small so isn't sufficient premium to be worth the risk.) --Tango (talk) 23:25, 7 December 2008 (UTC)

I'm sorry for splitting posts, I was corrupted to the dark side. I promise not to do it again unless money or women are involved :P Bastard Soap (talk) 09:06, 8 December 2008 (UTC)

Common descent

Not being very familiar with evolutionary biology, I was somewhat confused by Common descent: although it unambiguously states that the idea of a common ancestor means a single organism for all organisms living today, is this meant for specific types of organisms? Is it typically said that all animals have a common ancestor that isn't a common ancestor for plants? Or the finches: would it be normal to speak of a group of finches flying to the Galapagos Islands as together the common ancestors of today's finches? Nyttend (talk) 14:56, 7 December 2008 (UTC)

Any given population will have a most recent common ancestor, the more restrictive that population the more recent that ancestor will be (roughly speaking). The most recent common ancestor for all life on Earth was about 3 or 4 billion years ago (I forget when exactly), the most recent common ancestor for animals will be some time later than that (somewhere around 0.5 billion years ago, I think), the most recent common ancestor for humans is somewhere in the order of 10,000 years ago (estimates vary). You may also be interested in the identical ancestors point. --Tango (talk) 15:08, 7 December 2008 (UTC)

With asexual reproduction this is a fairly strait-forward question, since each organism has one and only one parent. But, with sexual reproduction, it becomes more complicated, since we each have 2 parents. Thus, we have 4 grandparents, 8 great-grandparents, etc. (assuming no interbreeding). This means 1024 forebears at 10 generations, over a million at 20 gens, and over a billion at 30 gens (around 1000 years). Now, this doesn't actually happen, because over those time scales you get a lot of interbreeding. However, when you go back hundreds of thousands of years, a rather large percentage of the human population back then became the forebears of any given individual now. So, there may have been more than one individual who is the common ancestor of everyone alive today.

A further complexity comes in with chromosomes. You have half the chromosomes of each parent, on average a quarter of each grandparent, etc. Again, that means that you would only have 1/1024 of the chromosomes of each ancestor from 10 generations back. And, since we only have 46 chromosomes, that means we have a 46/1024 chance of having a chromosome from each ancestor. Again, this math is altered based on interbreeding, but, if you go back far enough, the chances of having any one chromosome in common with a given ancestor is small. This was assuming random distribution, however. If a chromosome contained genetic material which made survival more likely, then you're more likely to have that chromosome from your ancestor. Then there's also the possibilities of genes moving from chromosome to chromosome and there are mutations to consider. So, how much genetic material we each have in common with our common ancestor or ancestors is quite complex of a question. And can you call someone your ancestor if you don't have any genetic material in common with them ? StuRat (talk) 16:42, 7 December 2008 (UTC)

These is certainly more than one common ancestor of any population (except possibly all life), since any ancestor of a common ancestor is a common ancestor. That's why it is the *most recent* common ancestor which is relevant. --Tango (talk) 16:57, 7 December 2008 (UTC)

Note that (with the exception of the Y chromosome, which is inherited only from the father, and of which most people have at most one copy) the odds are very poor that any single chromosome will be passed on intact for multiple generations. Genetic material is swapped between pairs of chromosomes by a number of mechanisms; crossing over (chromosomal crossover) is the most common. The likelihood of a crossover event taking place is roughly 1% per million base pairs (see centimorgan) of human DNA. Even the shortest non-Y chromosome (chromosome 21) is just shy of 50 million bases long, and the longest (chromosome 1) is about five times that.

In other words, if you examined one of your copies of chromosome 1 very closely, you almost certainly wouldn't find that it's identical to the chromosome 1 of one of your grandparents. It's much more likely to be grandma's chromosome 1 at both ends, with some of grandpa's chromosome 1 swapped in in the middle. This mixing and matching within chromosomes happens with each generation. In the example above, the odds are not 46/1024 that any given ancestor would have – by himself – supplied one of your chromosomes. Instead, the odds are essentially zero; no chromosomes are likely to have survived intact for ten generations without a crossover event. However, this does mean that the odds are pretty good that you will share at least some genetic material with each of your ancestors. Due to crossing over, it's likely that you'll have gotten a piece of DNA of some length from your eight-times-great grandfather. TenOfAllTrades(talk) 19:42, 7 December 2008 (UTC)

But to go back to the original question: No, it is not meant for specific types of organism only. The science of cladistics deals with formalizing the relationships of all living being. A recent common ancestor of all Galapagos finches was probably something we would call a finch. But the most famous ancestor of all birds would be a dinosaur. Richard Dawkins' The Ancestor's Tale is an excellent book, tracking back the ancestors that humans share with increasingly larger parts of life on earth. --Stephan Schulz (talk) 22:39, 7 December 2008 (UTC)

Displaying carbon and hydrogens in Symyx/ISIS draw

I'm trying to use Symyx (formerly known as ISIS draw) to draw some molecules but I can't get it to display the carbon and hydrogen atoms. I want all atoms of the molecules to be displayed. Anyone know how I can do it? ----Seans Potato Business 16:53, 7 December 2008 (UTC)

In my ISIS Draw...select a molecule, and then Edit Molecule (double-click the seelcted structyre, use right-click popup, or use the Object menu). There, in the Atom pane, you can control how the hydrogens are displayed. It looks like this always gives condensed structures ("CH_n") rather than drawing explicit bonds to H atoms. DMacks (talk) 19:18, 7 December 2008 (UTC)

This fixes the hydrogen isssue but not the carbon issue. I'm also unable to get the program to display the molecule at right angles. If I click Chemistry > Clean then bonds adopt more realistic angles which is not what I want. Trying to drag them into regimental order is labour-intensive an ineffective. ----Seans Potato Business 20:38, 7 December 2008 (UTC)

Not sure I understand what you mean (i.e., what you want it to to look like). Actually, I am sure I don't understand. Could you give us a sample diagram of what style you're trying to accomplish? DMacks (talk) 21:21, 7 December 2008 (UTC)

In this image, in the upper section, you see angled bonds (which I don't want) and in the lower section, regimental, right-angled bonds which I do want]. I also want every carbon atom to be displaced. I know it's possible somehow, because I'm looking at it in a text book. ----Seans Potato Business 21:43, 7 December 2008 (UTC)

A California earthquake causing an associated blackout and causing people to see the Milky Way

Hi. There was an earthquake in California that caused a blackout at night, causing people to run outside and see the Milky Way for the first time. Authorities and a local observatory were flooded with calls. I have also posted this at Talk:1989 Loma Prieta earthquake, which might have been responsible for this blackout, but it might also have been the 1994 Northridge earthquake, which struck in the middle of the night, and since I want this to be included in an article and I don't want to post OR, does someone know which earthquake it is, and preferably find a reliable source as well? Thanks. ~AH1^(TCU) 18:37, 7 December 2008 (UTC)

Here's information on a related event during the Northeast Blackout of 2003: [3]. --Jayron32.talk.contribs 18:47, 7 December 2008 (UTC)

I'm guessing not Loma Prieta; I didn't think to look at the sky, but lights were on in patches soon after dark. —Tamfang (talk) 08:50, 14 December 2008 (UTC)

Rhizobium

Hi the article on Rhizobium says that the bacteria convert atmospheric nitrogen to ammonia. My question is can plants use this ammonia directly to form their proteins etc or does it need to be converted to other molecules - e.g. nitrates before the plants can use them? Thanks. —Preceding unsigned comment added by 139.222.240.167 (talk) 19:58, 7 December 2008 (UTC)

See Nitrogen fixation#Biological nitrogen fixation and Nitrogen cycle#Assimilation. It looks as though the ammonia is quickly converted to ammonium ions, which are what the plants use. No doubt someone who understands this far better than I will soon be along with additional information. Deor (talk) 21:47, 7 December 2008 (UTC)

Long train journey

I had the misfortune today of having to catch a train from Preston to Southampton which took nearly six hours! I did a very simple calculation and worked out that the average speed of the train during the journey was 52 mph which seems very slow, particularly as it is supposed to be a main line service.

The first leg of the journey from Preston to Stockport via Bolton took 1:39 and is about 35 miles (according to a quick path-drawing excercise following the general route of the line in Google Earth). This averages around 21 mph although there were quite a lot of stops.

The main part of the journey, from Stockport to Southampton via Stoke, Stafford, Birmingham, Oxford and Reading (but with more stops than that, about 15 stops in total) took 4:09 and is about 214 miles. This works out at an average of 52mph.

The trains [[4]] are capable of doing 125 mph. I assume that not all of the lines it went on allow that speed and obviously slowing down and stopping at stations all wastes time but it stills seems very slow indeed to me. The Virgin Voyager trains seem to accelerate quite fast so I can't believe that and slowing down adds so much to the journey time.

If the train could average 80mph then it would easily do the journey in about 3 hours, which is a bit more bearable but why does going 250 odd miles take such a long time? I think I'll fly next time I want to travel such distances! Much quicker and usually cheaper too. —Preceding unsigned comment added by 62.249.220.179 (talk) 21:01, 7 December 2008 (UTC)

Slowing down, stopping, waiting in a station, and getting back up to speed again does take a significant amount of time. Say it adds on 5 minutes per station, you say there were about 15 stops on the main leg, that's 1hr 15 mins added on to your journey. There may also have been additional delays due to waiting for other trains to get out of the way or parts of track where the train had to go slowly (damaged rails, damaged bridges, sharp corners, etc.), which all adds up. --Tango (talk) 21:35, 7 December 2008 (UTC)

5 minutes per stop seems quite low. That might be how long they are actually stopped, but adding in the slow down and accel and you can probably double that. StuRat (talk) 22:15, 7 December 2008 (UTC)

Indeed, that was a conservative estimate. I was guessing at 3 minutes stationary and 1 minute breaking and accelerating (it will spend more than 1 minute doing those things, but it is moving, if slowly, so not all the time is lost). --Tango (talk) 23:21, 7 December 2008 (UTC)

It usually works out quicker although more expensive if you go via London. That's where the fast trains go. Very annoying for us provincials. Itsmejudith (talk) 23:29, 7 December 2008 (UTC)

Yes, it's just under five hours via London according to Traveline. It's eight hours by coach but that includes an hour's wait in Birmingham, giving you time to do some shopping.--Shantavira|^{feed me} 09:05, 8 December 2008 (UTC)

The biggest problem with this sort of journey is that the rail system was never designed that way. In fact it wasn't designed at all, but grew somewhat organically depending where the railway companies (no national organisation in those days) thought that they could make some money. Presumably no-one thought that there would be much call for paying customers to travel your route, so you have to make use of the tracks that actually were built (and those not subsequently ripped up in the time of Beeching). Cross-country routes like this one are generally hampered by the need to use parts of the major routes and they have to wait their turn to fit in with the express trains. I've had my share of journeys like you describe, just try your best to feel noble about your reduced carbon footprint. Mikenorton (talk) 18:32, 8 December 2008 (UTC)

So lets say the train does 0 to 60 in ten seconds after every stop... not one for the old folks anyway. Wouldnt work the best if you were standing at the toilet. ~ R.T.G 12:50, 9 December 2008 (UTC)

Citrus identification

Can anyone identify this citrus tree? The fruit are about 3 inches (7.5 cm) in diameter, with orange skin and greenish pulp. The taste is like a lime, and very sour. [5] --Amble (talk) 23:18, 7 December 2008 (UTC)

Likely it's Mandarin lime – Citrus limonia is a hybrid. Julia Rossi (talk) 01:07, 8 December 2008 (UTC)

Thanks. I considered that one but doubted it because of the flesh color; it's greenish-yellow instead of orange. --Amble (talk) 05:48, 8 December 2008 (UTC)

I found it tricky too, but it's the pulp that makes it different. The article could use more images. : ) Julia Rossi (talk) 06:01, 8 December 2008 (UTC)