Wikipedia:Reference desk/Archives/Science/2010 February 9

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February 9

Attraction of metal to magnet.

How would one calculate the force on a piece of metal induced by a solenoid? The mass of the object, its magnetic permeability, its distance from the solenoid, and the strength of the field are known. Also, from there, how would you find its maximum velocity, ignoring gravity and friction? (when its at the center of the solenoid, I think.) —Preceding unsigned comment added by KyuubiSeal (talk • contribs) 00:34, 9 February 2010 (UTC)

This strikes me as a homework problem, which the reference desk is not suppose to do for you, though we may help with specific pieces. It also seems to be underspecified unless you know something about the dimensions of the solenoid and the piece of metal. The two typical homework cases are a metal bar the same size and length as the solenoid that slides into the middle, or a metal plate large enough to completely cover one end of the solenoid. Dragons flight (talk) 02:23, 9 February 2010 (UTC)

I can't prove it's not a homework problem, all I can do is say it's not. We don't start physics until 12 grade :(. The bar is the same diameter and length as the solenoid. EDIT: After reading some other posts, I realize I should be more specific. What I'm looking for is the equation describing the force the metal undergoes. I think I can get the velocity from there. All I can find is an equation for the force between two magnets. KyuubiSeal (talk) 03:28, 9 February 2010 (UTC)

The situation sounds a little bit like a coilgun, thus you might find some useful info here [1]. 152.16.15.144 (talk) 04:38, 9 February 2010 (UTC)

Unfortunately, ferromagnetism is fairly complicated. The force that a magnetic field creates is only simple if the field is very regular and simple - and a solenoid actually isn't very simple. It does have a region near the center, aligned with the axis, where the magnetic field is fairly uniform and collimated. The force also depends on many factors - including the material properties, the relative motion of the metal with respect to the magnetic field, and its ability to induce current and magnetize. But to really solve this nasty set of equations correctly, you will need to do some heavy-duty integral calculus. If, as you say, you haven't started any physics yet, you probably don't have the necessary math pre-requisites to solve this analytically. You probably can do a lot of simple algebra with magnets - the force that a magnetic field imparts to a charged particle like an electron is exactly proportional to the velocity, and perpendicular. This is called the Lorentz force law. When a magnet (permanent magnet or solenoid / electromagnet) interacts with a block of metal, that effect is called ferromagnetism. Again, the interaction is pretty nasty to describe correctly - there's not even a simple approximation that's very good to describe it. You could start off by estimating approximately 1/r^3 falloff with distance; but in reality, the force depends on many factors, including hysteresis - i.e., the path that the metal block takes as it approaches the magnetic field will cause the effective force to be different. This may be a good chance to do some experimental physics, though - with appropriately controlled conditions, you should be able to set up a repeatable experiment and then measure it - and generate a data table. You could even try to fit a power law, exponential, or any other formula, to that data. For the reasons I've mentioned above, most introductory physics courses never really give you homework problems to calculate the force of a magnet on a block of metal - there's too much math that doesn't simplify very well. Instead, they have you calculate easier quantities, like the force on a free electron or the force on a wire that's carrying electric charges. As you may know, electricity and magnetism are closely related - and the equations that govern that interaction are much simpler than those which govern the (arguably more familiar) magnet-attracting-metal phenomenon. In closing, you can read Calculating the Magnetic Force at our Magnet article - but as you can see, there's not even an approximate equation for the scenario you want (because the approximation is pretty bad). Nimur (talk) 05:23, 9 February 2010 (UTC)

Bleh. Dragons flight (talk) 06:01, 9 February 2010 (UTC)

In the uniform field approximation, what you describe is an elementary problem in magnetodynamics. Approximate the field as a constant everywhere inside the solenoid and zero everywhere outside. The energy density in the field is described by this article section. The total energy can be computed with the metal present, absent, anywhere in between. The force simply follows as the change in energy as a function of position. Assuming the permeability of the metal is much greater than that of free space:

$F\approx {B^{2}A \over 2\mu _{0}}$

where A is the cross-sectional area of the solenoid, B is the field strength, and μ₀ is the permeability of free space. Dragons flight (talk) 06:01, 9 February 2010 (UTC)

To clarify, that's the constant, inward force achieved under this approximation when the metal is partially inserted into the solenoid. Under this approximation the force is zero when the metal is either outside the solenoid or fully surrounded by the solenoid. Of course the force isn't really zero when the metal is outside, but that's a more complicated calculation. Dragons flight (talk) 06:26, 9 February 2010 (UTC)

Electromagnetic induction vs Transformer action

We have been asked to write a small treatise (<1000 words)on the above subject for our course. I know you dont do our homework for us, but any pointers would be most welcome. I always thought that transformers worked by electromagnetic induction, but the question seems to imply otherwise. Am i right in thinking that?. ie is there a difference between an induction coil, and a transformer? —Preceding unsigned comment added by 79.76.205.40 (talk) 00:52, 13 February 2010 (UTC)

A transformer is nothing more than two induction coils mounted on a common magnetic core, and it works by electromagnetic induction, not some kind of mysterious "transformer action". The only difference between a plain induction coil and a transformer is that an induction coil just creates a variable magnetic field when you pass AC current through it, whereas in a transformer, the primary coil creates the magnetic field from the AC current, and then the secondary coil turns this magnetic field back into AC current at a different voltage -- which is still electromagnetic induction, just the other way round. Please tell your teacher that he/she ain't got no clue. Clear skies to you 24.23.197.43 (talk) 01:07, 13 February 2010 (UTC)

This is a perfect example of why we should institute merit pay for teachers, and maybe abolish tenure as well... 24.23.197.43 (talk) 01:10, 13 February 2010 (UTC)

(EC) Transformers do work by induction. You can make an induction coil by wrapping many turns of insulated wire around an iron core. It will exhibit inductance. If a voltage is applied across the wire, it will take a longer time for the current to reach its full value than it the wire were not coiled around a ferrous core. If you open the switch, there will be a sharp voltage spike causing a spark, as the inductance effectively fights the decrease in current. If you wrap a second insulated winding around the first winding and the ferrous core, you have a transformer. Any change in the current in the first (or primary) winding, whether a change in direct current or an alternating current, will produce a voltage in the insulated secondary, and current can be drawn out of the secondary without any direct metallic connection between the circuits. See Michael Faraday#Electricity and magnetism for early experimental observations, Inductance for a rather mathematical treatment of the subject which requires higher mathematics to comprehend, Faraday's law of induction for another treatment which requires higher mathematics, and Transformer which offers at least some explanation in addition to the math. George Westinghouse by the 1880's used practical power transformers developed by William Stanley, Jr. to step up low voltage alternating current from generators to high voltage for long distance transmission, and then back down to voltages low enough to be used in homes and businesses. Nathan Stubblefield was a rural experimenter who used two coils of wire connected to telephones to transmit speech and music circa 1900 purely by electromagnetic induction. Induction coils (sometimes just called inductors) as well as transformers are commonly used in most electronic devices, such as telephones, televisions, radios, and computers. (291 words). Edison (talk) 01:20, 13 February 2010 (UTC)

ADM formulation

Can the ADM formulation of general relativity be used to describe any spacetime allowed by Einstein's formulation? If it can also be interpreted as a field on a Minkowski spacetime, how could it describe wormholes and similar? Thx, 99.237.180.215 (talk) 00:50, 9 February 2010 (UTC)

Meiosis

If during Meiosis, the sister chromatids separated first and then the homologous chromosomes, would it make a difference in the genetic diversity of the gametes? —Preceding unsigned comment added by Kristannsnyder (talk • contribs) 01:19, 9 February 2010 (UTC)

It would only make a difference in doing your own homework. --Jayron32 03:35, 9 February 2010 (UTC)

Mixing up the parental chromatids isn't the only source of genetic diversity in meiosis... *hint hint* 152.16.15.144 (talk) 03:58, 9 February 2010 (UTC)

If it's even possible -- because chromatid separation at that point would only happen if the asters pulled on the same chromosome to rip apart the chromatids, it might very well preclude proper distribution of the chromosomes into the gametes, unless there's another process that would allow for proper distribution. DRosenbach ^{(Talk | Contribs)} 08:21, 9 February 2010 (UTC)

Dinosaur eggs

How much evidence is there that dinosaur eggs in the late Cretaceous suffered from an acidic environment? Thanks. 67.243.7.245 (talk) 03:11, 9 February 2010 (UTC)

Please see Dinosaur egg--NotedGrant Talk 18:23, 9 February 2010 (UTC)

Did I fail to notice anything in this very short article that relates to the OP's question? 93.132.134.161 (talk) 22:50, 9 February 2010 (UTC)

Fossilized eggshell often shows signs of corrosion attributed to acid dissolution of the calcium carbonate. Here is a research paper "Taphonomic Effects of pH and Temperature on Extant Avian Dinosaur Eggshell" on the subject. Cuddlyable3 (talk) 23:11, 9 February 2010 (UTC)

How can we be sure then that any eggs failed to hatch due to acidification, as is sometime suggested (eg Walking With Dinosaurs)? 67.243.7.245 (talk) 00:00, 10 February 2010 (UTC)

We can't be sure. Walking With Dinosaurs tended to present one possibility as the absolute truth, regardless of how uncertain mainstream science was. It was intended the entertain and show-off computer graphics, not educate. --Tango (talk) 19:19, 10 February 2010 (UTC)

Trepanation

After a trepanation is performed how is the brain protected? A patch? A helmet? Unless I missed it, our article doesn't say and a couple other articles on the net and haven't found anything. I'll keep looking but thought someone here might know off the top of their head. A Quest For Knowledge (talk) 03:16, 9 February 2010 (UTC)

The curious case of Mr.Phineas Gage (see article) who survived accidental trepanation. Cuddlyable3 (talk) 19:09, 9 February 2010 (UTC)

"off the top of their head". <rolls eyes>. Seriously dude... tell me that wasn't intentional... --Jayron32 03:34, 9 February 2010 (UTC)

What do you mean intentional? I'm genuinely curious. I found something that says the skin grows back over the hole, but doesn't seem like sufficient protection to me. A Quest For Knowledge (talk) 03:40, 9 February 2010 (UTC)

You ask a question about drilling a hole through the top of someone's head (literally taking someting "off the top of ones head") and then ask if anyone knows something about it with the idiom "off the top of their heads". Wow. Jokes aren't funny if they have to be explained, less so if the person telling the joke doesn't realize they even told it. --Jayron32 04:20, 9 February 2010 (UTC)

Oh, I finally got it. That's my second Duh! on Wikipedia today. A Quest For Knowledge (talk) 05:21, 9 February 2010 (UTC)

in traditional trepanation, no protection is used - the holes (generally speaking) are not large enough to present a structural risk to the skull or brain. in modern equivalents (such as where pieces of cancerous bone material are removed) the surgeon may elect to fuse a plate of some sort into the surrounding bone. The brain itself us encased in the dura matter beneath the skull, so there's no danger of it 'leaking out' or suffering damage by anything other than a direct blow through the vulnerable hole. --Ludwigs2 04:15, 9 February 2010 (UTC)

Post ec. I found better results using "burr hole" rather than "trepanation". They may not be equivalent procedures though, so the techniques may not be the same. Here is an abstract to something that may point you in the right direction. [2]. In case you didn't get it, Jayron32 was referring to the ironic use of the phrase "off the top of their head" in a question about drilling holes into skulls. 152.16.15.144 (talk) 04:23, 9 February 2010 (UTC)

(ec too)

I recall reading that ancient skulls have been found where the bone has started to grow back over the hole from a Trepanation, indicating a 'successful' operation. I don't see any reason why the bone would not completely re-grow over a 'small' hole. In modern days implanted plastic or metal plates(Cranioplasty) seem to be the go, for where a large piece of skull cannot be replaced. Bone healing may be of interest. See also Craniotomy. I recall hearing of people with extremely large sections of skull permanently removed who have had to wear helmets to protect their brains from damage. Note, I have training in anatomy and phsysiology, but I am not a medical doctor. This is just 'off the top of my head' . ;-) I welcome corrections. 220.101.28.25 (talk) 04:56, 9 February 2010 (UTC)

• This web page may be of interest History of Neuropsychology --220.101.28.25 (talk) 05:08, 9 February 2010 (UTC)
• This gives details of bone grafting for "reconstruction of skull defects" Journal of Cranio-Maxillofacial Surgery Volume 26, Issue 6, December 1998, Pages 379-385 --220.101.28.25 (talk) 05:33, 9 February 2010 (UTC)

On an episode of Rome, a small metal plate was nailed into place. I can't find anything on the accuracy of this particular depiction. Vimescarrot (talk) 06:38, 9 February 2010 (UTC)

In Patrick O'Brian's The Far Side of the World, Maturin trepans Joe Plaice, "who had brought his head against a ring-bolt in a commonplace fall down a ladder, fracturing his skull".

It was an operation that Dr Maturin had carried out at sea before, always in the fullest possible light and therefore on deck, and many of them had seen him do so. Now they and all their mates saw him do it again: they saw Joe Plaice's scalp taken off, his skull bared, a disc of bone audibly sawn out, the handle turning solemnly; a three-shilling piece, hammered into a flattened dome by the armourer, screwed on over the hole; and the scalp replaced, neatly sewn up by the parson.

O'Brian is known for exercising a fair degree of historical accuracy in these novels, but I don't know if this particular practice is accurately described. ToE^T 08:14, 9 February 2010 (UTC)

The 3-shilling piece could have been this British silver coin issued 1811 to 1816. Cuddlyable3 (talk) 19:17, 9 February 2010 (UTC)

(Note: I only cite references, and do not claim any medical training. Certainly none of this historic medical information constitutes present day medical advice.) 1801, Benjamin Bell wrote about trepanning for skull fractures or other brain diseases. Surgeons of that time apparently did the operation on occasion. There was discussion of "brain inflammation" resulting from "the exposure of the brain to air (of course with no thought of there being germs)." After the trepan removed a circle of skull and the depression was corrected, or underlying blood clots or pus were removed, he just called for application of soft lint with "emmoliants" to the wound, with a linen dressing over all. No prompt installation of a silver patch was called for. The skull might eventually heal back over the opening. By 1816, the surgical book by Sir Charles Bell had some careful observations on brain injuries and their surgical management. I have been very critical of the medical profession clinging superstitiously to bleeding and purging, but Bell makes a case that bleeding decreases the injury of the dura mater against sharp bone edges of the skull after a penetration or depressed fracture of the skull, due to the reduced "pulse pressure." That book also does not say to make a patch out of silver and patch the hole promptly. I have also read accounts of surgery in the UK in the early 19th century (1830s perhaps, in rural Scotland most likely) where penetrating trauma to the skull was treated. Of course they knew nothing of germs, but some patients survived the operation, at least for weeks or months. Gauze with iodine might be used based on some theory other than that it killed germs. One surgeon covered the open wound with gauze and kept a slow drip of water over it to irrigate it while the hole in the bone slowly healed from the outside in. He was hesitant to just sew the scalp over it and wish the patient well, because he knew fatal infection would likely result. Dorsey, 1818, p307 says to put a soft dressing of "bread and milk" over the trepan wound, with the scalp covering the exposed dura mater. Pus and blood should be allowed to escape. Clearly hammering out a coin and patching the skull would be alien to his advice as well. Cooper 1822 discusses the trepan, and says that it is preferable to elevate the depressed bone with levers or elevators rather than trepanning it. He says that after elevating or trepanning the bone, the scalp should be laid over the opening (no silver coin patch mentioned), and that a soft dressing with nonirritating emmoliant shouled be applied. In all the cases, the wound is allowed to drain, and healing is from the outside of the hole in by granulation of the bone. Cooper says that a cover of horn or metal may be placed over the skin to shield the soft area from injury after the wound is healed. Phillips (1840) page 826 says that "the ancients" would place a perforated gold or silver covering in place of the removed bone, but that that was not done in "modern practice" since it was preferable to place a sponge or lint over the exposed brain to allow drainage. Phillips also has some statistics on deaths versus recoveries for trepanning as a treatment for various problems. I wonder if the fictional depiction of a silver coin being used as a skull patch after trepanning to correct a depressed skull fracture, seen in the Maturin book was projecting back to early times a practice used in 20th century battlefield medicine, where the infection was much easier to control? Edison (talk) 22:17, 9 February 2010 (UTC)

Am I the only person here feeling the urge to put on a helmet and go sit in a corner? --Ludwigs2 23:16, 9 February 2010 (UTC)

Good luck with that. Equipment of a barber-surgeon before the advent of Anesthetics could include a mallet and a metal helmet for the patient. The mallet was for hitting the helmet to concuss soothe the patient. This is how surgery on the Mary Rose 16th century warship was carried out. Cuddlyable3 (talk) 21:52, 10 February 2010 (UTC)

They did not use good old fashioned booze for anesthetic? Googlemeister (talk) 17:19, 11 February 2010 (UTC)

After using Grog to wash his hands and fortify himself a groggy naval surgeon would probably not waste it on a patient likely to die. Cuddlyable3 (talk) 00:36, 12 February 2010 (UTC)

capacitor

why a capacitor charges when connected across a DC supply —Preceding unsigned comment added by Raghuram.bura (talk • contribs) 08:43, 9 February 2010 (UTC)

You should start by reading our capacitor article. DMacks (talk) 09:33, 9 February 2010 (UTC)

The direct current can flow for a limited time through the insulator between the plates of the capacitor. This is called Displacement current and while it flows energy is being stored in the capacitor which thereby becomes charged. Charging a capacitor causes it to produce a voltage that opposes further charging. Cuddlyable3 (talk) 18:58, 9 February 2010 (UTC)

Be aware though that a displacement current isn't a real current. There is no movement of charges across the insulator. Dauto (talk) 20:46, 9 February 2010 (UTC)

... or, more precisely, the diplacement charging current is a real current through the battery and in the wires connecting the plates of the capacitor to the battery, but there is no "real" current (or, strictly speaking, an extremely small current) through the insulator. Dbfirs 22:27, 9 February 2010 (UTC)

It'sPart of it is a real current and itthat results from realignment of charges inside a material insulator. Insulator means that the usual charge carriers (electrons) cannot break free from their respective atoms or molecules. Considering for simplicity the Bohr model of an atom, an external electric field can bend the outer electron orbit without breaking it. This is polarizing the atom. One could stop the explanation there but some capacitors have only a vacuum to insulate the plates from one another. Displacement current through a vacuum is also real butwhere there are no atoms to polarize and it is more difficult to explainhas to be explained entirely in terms of setting up an electric field. Cuddlyable3 (talk) 21:32, 10 February 2010 (UTC)(edited with thanks to Dauto)

Uh... No. You are both mistaken, or perhaps confused. The current through the wires is not a displacement current and the polarization of the dielectric is only part of the explanation as the difficulty of explaining the displacement current through vacuum should have indicated. Dauto (talk) 00:09, 10 February 2010 (UTC)

Yes I was confused. I should have read our article on displacement current before I responded. (I've corrected my reply above.) The so-called displacement current is not just a re-alignment of charges, so I'm not sure whether one would regard it as real or not. Dbfirs 13:10, 10 February 2010 (UTC)

Flame Proof tests in USA and Europe

What are the Flame Proof Classifactions and / or Standards to be complied with regarding installation of Recycled Polystyrene Architectural Mouldings such as Skirtings, Base plates, Crown Mouldings, Cornices, etc, according to the American and European Standards on Building Regulations ?196.210.246.79 (talk) 08:52, 9 February 2010 (UTC)

Sorry I don't have time to track this down, but there is a well cited ASTM standard regarding this test. For polystyrene the standard would be a "D" number, such as D-XXXX. Can't recall the actual standard number. I would presume there are also CE-Mark, ANSI, and ISO standards. CoolMike (talk) 00:18, 10 February 2010 (UTC)

light(4)

if a star travels around its own galaxy at one thousand miles per second emitting light at 186,ooomps. how far would the light coming from it travel in a second. would the fact that the star as moved 1000 miles be added to the light speed of 186000 miles per sec making it really be travelling at 187000 miles per sec. or would the light only be able to be emitted at 185000 miles per sec so it did not exceed the magic 186000 mile per sec. —Preceding unsigned comment added by 82.22.255.246 (talk) 13:53, 9 February 2010 (UTC)

No it would not. The speed of light is constant. Everyone sees the light travel at 3*10^8 m/s, regardless of the source's velocity. See special relativity and lorentz transform —Preceding unsigned comment added by 157.193.173.205 (talk) 13:57, 9 February 2010 (UTC)

The speed of light is always observed as c (or 186000 miles/sec, or 3*10^8 m/s, or whatever your preferred units) regardless of what the observer is doing. Consider that an observer on the star (or in orbit around the star) can easily verify that he is stationary, that light leaves the star at exactly c, and that the galaxy is moving around him at 1000 miles/sec. That's a perfectly valid conclusion. An observer at rest with respect to the galaxy will observe the star moving at 1000 miles/sec and light emitted from the star moving at exactly c. Note, however, that this second observer will see a blue shift on the light emitted in the direction of the star's travel and a red shift on the light emitted opposite the direction of travel. Albert Einstein postulated the constant speed of light in his theory of special relativity; you may wish to read our introduction to special relativity. — Lomn 14:02, 9 February 2010 (UTC)

(ec):::::Lomn said rightly that the theory allows an apparent closing speed to exceed c, so the theory is not contradicted. A person on one spaceship (object) cannot send a message faster than c to the other spaceship (object). Cuddlyable3 (talk) 18:40, 9 February 2010 (UTC)

Relatedly, if you want to add velocities at speeds near c (e.g. if your spaceship was going .75c and passed another spaceship going .75c in the other direction, why don't they each look like they are going more than c), you need to use the relativistic velocity addition formula, not the standard Galielean one, if you want to get correct answers. --Mr.98 (talk) 14:55, 9 February 2010 (UTC)

Yep. Note that while the stationary observer (who makes those .75c measurements) observes the two ships closing at greater than c (which is allowed), neither ship (nor the stationary observer) will observe any single object moving at greater than c. — Lomn 15:37, 9 February 2010 (UTC)

The theory states that speed cannot exceed C from any reference frame, when the observer is in between two objects closing in then the apparent speed observed by the stationary observer will exceed C thereby contradicting the theory (If I'm right)--NotedGrant Talk 18:20, 9 February 2010 (UTC)

No - there is nothing out there exceeding 'c' - there is a situation where the "closing speed" appears from the stationary observer to exceed 'c' - but none of the actual objects involved is exceeding c. What IS happening is that if the stationary observer calculates the time until the two objects collide, and the measures the distance between them and divides one by the other then the "closing speed" he arrives at is 1.5c...but that doesn't have much of a physical meaning because the speed of each craft relative to him is still 0.75c and if he's thinking about how things appear form the perspective of either craft then he has to allow for their temporal distortions. From the perspective of the two pilots, the closing speed is less than 'c' and the time taken to cover that distance is much longer than the stationary observer calculates precisely in order to be consistent with that. Time distortion accounts for that discrepancy between the two pilots and the guy who is about to be vaporized by an alarmingly intense gamma ray bust when two multi-ton objects smack into each other at close to the speed of light. SteveBaker (talk) 18:36, 9 February 2010 (UTC)

(ec)Lomn said rightly that the theory allows an apparent closing speed to exceed c, so the theory is not contradicted. A person on one spaceship (object) cannot send a message faster than c to the other spaceship (object). Cuddlyable3 (talk) 18:40, 9 February 2010 (UTC)

For less hypothetical example, consider the LHC which collides particles into each other travelling at 99.9999991% the speed of light. If you fail to take into account the fact that time is relative, then it seems like the approaching particle is coming at you at almost 2x the speed of light from the reference frame of one of the particles. But time slows down for the particles so there is no problem. See Lorrentz factor and work at it for a while. -Craig Pemberton 02:18, 10 February 2010 (UTC)

anti-graviton (angriton)

if there exists a graviton (which most people accept) then according to rule of universe there must be an anti graviton to suppress or to reduce this force.I may call it Angriton. Now when a flame burns it is always in the upward direction .It is defying the force of gravitation(no matter the weight is less of flame it never goes right of left but only upwards).even in the case of plants or trees it always grow in the upward direction.So atleast there is some proof there is anti-gravitons exist as the particle in atoms or matter. Now in the flame there is random and fast moments of the particles. So then can the fast and the random moments create a force(may be in terms of electo-magnetism)or of some other kind which strengthens the anti gravitons and hence suppress the gravitons due to which a flame is always upwards? —Preceding unsigned comment added by Itsrohit (talk • contribs) 19:14, 9 February 2010 (UTC)

There is no need to invoke exotic particles to explain buoyancy. (Incidentally, the graviton is its own antiparticle, much like the photon.) -- Coneslayer (talk) 19:17, 9 February 2010 (UTC)

The flame goes up because cold air flows down around the flame, obeying ordinary gravity as cold air is heavier than hot. Plants and trees just know which direction is good for them to grow: roots downwards and stem/trunk upwards. Cuddlyable3 (talk) 19:22, 9 February 2010 (UTC)

plants "just know": or rather phototropism and gravitropism 75.41.110.200 (talk) 20:53, 9 February 2010 (UTC)

I think the OP is really reaching for something like orgone but casting it in physics-ish language. --Ludwigs2 20:55, 9 February 2010 (UTC)

Also, the OP's claim that "according to rule of universe there must be an anti graviton to suppress or to reduce this force" is not correct. The standard model does have a lot of symmetry - but I doubt many physicists would say that a "law of the universe" requires an anti-gravity particle. Further, the existence of the graviton is still speculative and depends on both theoretical development and experimental verification before it's really well-accepted by most particle physicists. Nimur (talk) 00:58, 10 February 2010 (UTC)

The reason a flame moves upwards is something that's been well known and understood for hundreds - if not thousands of years. There is no need to invoke extra magic particles to make it happen. Hot air floats on cold air like a cork floats on water. The hot air weighs less (technically: "is less dense") than the cold air, so the heavier cold air pushes it upwards. In fact, what makes the flame go up is the same thing that makes the cork float - and that's just regular gravity. You would do well to learn a little very basic physics before you attempt to hypothesize entirely new particles! SteveBaker (talk) 03:13, 10 February 2010 (UTC)

Also, flame in microgravity is awesome. There are a few videos online. -Craig Pemberton 03:40, 10 February 2010 (UTC)

I think seeing a microgravity spaceship on fire in a movie or game would be sweet. The CGI guys need to get on the ball. -Craig Pemberton 03:43, 10 February 2010 (UTC)

I am one of those "CGI guys" - and the problem is that in movies and video games people want things to look and sound the way they expect them to. Hence (typically) explosions in space make loud "BANG!" noises and (for example) trail smoke behind a spacecraft even when it's moving at constant speed. It's entertainment and therefore giving people what they want is the name of the game...whether it's realistic or not. SteveBaker (talk) 20:24, 10 February 2010 (UTC)

SB has just explained FOs. Cuddlyable3 (talk) 21:23, 10 February 2010 (UTC)

I think that there is more of a market for verisimilitude than that attitude belies. The very wondrous strangeness of it would charm a lot of people. -Craig Pemberton 23:22, 10 February 2010 (UTC)

Ancinet landmass plotting becomes less clear

I was told earlier after Jurassic time the landmass tectonic going further back in history things start becoming more and more fuzzy but 300 alot of fossils exist, green lizard with peacock shape wings exist about 280 MYA 330 MYA alot of dragonflies. What informations make the landmass plotting less clear? Was this speed of plate motion clouds the information or what?--209.129.85.4 (talk) 20:49, 9 February 2010 (UTC)

"alot" is not a word.Dauto (talk) 16:57, 12 February 2010 (UTC)

In short, because the whole thing is estimation, and the further you remove yourself from the known present, the more the uncertainties of the estimations compound. There's no firm fossil equivalent to say where plates used to be. — Lomn 20:54, 9 February 2010 (UTC)

And the ocean floor can be used to show how continents have moved, but when it is too old it is subducted and becomes inaccessible for investigation. There is no ocean floor left in place from those earlier times. Graeme Bartlett (talk) 21:47, 9 February 2010 (UTC)

For pre-Jurassic (that's the age of the oldest oceanic crust) plate reconstructions, it is necessary to use paleomagnetic data. This is done by sampling rocks (normally igneous, as they have had there 'compasses' reset - i.e. the magnetic minerals have cooled through the curie point. They represent a frozen record of their position relative to the magnetic pole at that time. Suitable rocks of the right age are not present everywhere, so some pieces of the puzzle are very unconstrained. Mikenorton (talk) 22:51, 9 February 2010 (UTC)

death

what was cause of death in this vid

http://www.theync.com/media.php?name=14054-crazy-fat-kid —Preceding unsigned comment added by 67.246.254.35 (talk) 22:23, 9 February 2010 (UTC)

The above link is not safe for work and contains adult images. Nimur (talk) 22:28, 9 February 2010 (UTC)

"Showoff Fat Kid Injects too much Synthol to have Muscles...and Dies Hours Later in Hospital" is the cause of death that is clearly stated above the vid of an autopsy. The OP's posting of a shock site was uncalled for. Here is a responsible site with information about Synthol abuse by bodybuilders. (It may need to be updated by a confirmed report of a Synthol fatality. Bodybuilders' abuse of Synthol should be mentioned in the Wikipedia article Synthol.) Cuddlyable3 (talk) 22:55, 9 February 2010 (UTC)

why did he die thou —Preceding unsigned comment added by 67.246.254.35 (talk) 05:23, 10 February 2010 (UTC)

Pardon my insolence, but the Darwin award article may be relevant here. --Mark PEA (talk) 14:36, 10 February 2010 (UTC)

Read Site enhancement oil, especially the section on "Risks" which explains how it can kill you if you inject it. Its not steroids, and not supposed to be taken intraveneously. Its basically supposed to be injected under the skin to make your muscles look bigger by making them bulge. People inevitibly get confused between "steroids injected to make your muscles actually bigger" and "oil injected under the skin to make your muscles look bigger" and inject the oil directly into their veins, which, of course, kills 'em by the methods noted in the article. Primary cause of death is, therefore, stupidity... --Jayron32 06:17, 10 February 2010 (UTC)

From the links to Synthol and Site enhancement oil above it looks like there are two entirely different substances called Synthol. The one for the muscles is just oil; however, the one that's described as a mouthwash is said to contain chloral hydrate. God help you if you confuse those two... --Dr Dima (talk) 07:32, 10 February 2010 (UTC)

Coroners are expected to formulate Cause of Death not as "He was stupid" but in medical terms, in this case possibly acute myocardial infarction. Jayron32 do you mean "It is not steroids..." and "It is basically supposed..."? Cuddlyable3 (talk) 21:17, 10 February 2010 (UTC)

I meant "it is up for the linguistic pedants to hunt out every time I miss an apostrophe" --Jayron32 03:44, 11 February 2010 (UTC)

chemical names

What do things like cupric, ferrous, etc. mean? --70.134.53.225 (talk) 23:13, 9 February 2010 (UTC)

Try googling for "define: cupric", "define: ferrous", etc. Looie496 (talk) 23:17, 9 February 2010 (UTC)

But in general, what do -ic and -ous mean? --70.134.53.225 (talk) 23:20, 9 February 2010 (UTC)

In English they are just the ends of words used in some adjectives: arduous, cryptic. It's a little confusing with ferrous (meaning "iron") and cupric (meaning "copper") because those words come from Latin; English for "iron" is not "ferr", and English for "copper" is not "cup". (By the way, the Language Reference Desk specializes in these sorts of language questions.) Comet Tuttle (talk) 23:25, 9 February 2010 (UTC)

Many elements have both a lesser and a greater ionization state is readily available for chemical reactions, for example Fe⁺² and Fe⁺³. In general, -ous denotes a lesser state than -ic when both terms are used for a given element (e.g. ferrous / ferric, cuprous / cupric, etc.). The exact ionization states given such names vary from element to element however. Dragons flight (talk) 23:31, 9 February 2010 (UTC)

(ec) Some metals have more than one common oxidation state, so different adjectival forms arose to distinguish them. Copper#Compounds states "Using old nomenclature for the naming of salts, copper(I) is called cuprous, and copper(II) is cupric." Iron#Chemistry and compounds states "Traditionally, iron(II) compounds have been called ferrous, and iron(III) compounds ferric." From those two examples, you can see the naming convention for the suffixes used for higher vs lower oxidation state. DMacks (talk) 23:34, 9 February 2010 (UTC)

Is there a page with a list of the specific ionization states for the -ous and -ic forms of each transition metal? --75.28.55.39 (talk) 23:34, 9 February 2010 (UTC)

This page [3] has a list of traditional names and states halfway down, possibly incomplete. Dragons flight (talk) 23:43, 9 February 2010 (UTC)

Why don't they still use those names? They sound so much cooler. --75.28.55.39 (talk) 23:49, 9 February 2010 (UTC)

IUPAC nomenclature of inorganic chemistry is the formal specification for naming these things. The "why" is "because an IUPAC committee decided it". But really, it's not obvious from the name what the actual oxidation state is unless you are familiar with the specific element. And it doesn't have enough flexibility to deal with more than two forms. So it fails the basic goal of being clear and fully systematic rather than an organized collection of special-cases. DMacks (talk) 00:03, 10 February 2010 (UTC)

(ec) In general, the "-ous" and "-ic" represent different bonding/oxidation states. For example, cupric sulfide is the same as Copper(I) sulfide - and cuprous sulfide is Copper(II) sulfide. The same trend goes for many of these - but in general, the IUPAC-preferred nomenclature, which explicitly states the ionizaton state, is easier to work with. Since oxidation states vary from element to element, the explicit specification means you don't have to memorize/remember the lowest state for any particular element. It also helps with "corner cases" when elements have unusually large numbers of possible states. Nimur (talk) 00:46, 10 February 2010 (UTC)

Relatedly, the oxygen acids of many elements use -ous for the one with fewer oxygen atoms and ic for those with more. For example chlorous acid is (if I recall correctly) HClO₂ whereas chloric acid is HClO₃; sulfurous acid is H₂SO₃ whereas sulfuric acid is H₂SO₄; phosphorous acid is HPO₂ H₃PO₃ whereas phosphoric acid is HPO₃ H₃PO₄ (I could have gotten some of these wrong — follow the links if you want to be sure.

Note that phosphorous is not the same word as phosphorus! The first is an adjective; the second, a noun. This follows the same pattern as mucous / mucus and callous / callus; both these pairs are often confused.

In the oxygen-acids case, if an acid ends in -ous, its salts will end in -ite; if it ends in -ic, its salts end in -ate. --Trovatore (talk) 03:21, 10 February 2010 (UTC)

As a chemistry teacher, I used to check if my students actually paid attention to nomenclature by checking to see if they could draw the structure of Periodic acid. Not "peer-ee-odd-dick" acid, but "perr-eye-oh-dick" acid. Its an analogue of Perchloric acid and Perbromic acid, but people often confuse it with the word "periodic" meaning once in a while, rather than "per-iod-ic" or "related to the iodine(VII) oxidation state". --Jayron32 06:14, 10 February 2010 (UTC)

Of course, in so doing, you're producing an entire generation of chemists who'll talk about the perr-eye-oh-dick table! SteveBaker (talk) 13:58, 11 February 2010 (UTC)

I assume that phosphorous is pronounced foss-FOR-us; is that correct? I don't know that I've ever actually heard it spoken. --Trovatore (talk) 09:11, 10 February 2010 (UTC)

Click the little speaker at fos-fer-uhs. DVdm (talk) 09:21, 10 February 2010 (UTC)

Hmm, that's too bad — that sounds the same as phosphorus. Note though that the second-syllable stress is the second alternative. --Trovatore (talk) 09:43, 10 February 2010 (UTC)

Hydric oxide and dihydrogen oxide are names for water. Hydrous oxide doesn't exist. Hydrogen dioxide is nasty stuff that may kill us all by attacking the ozone layer. Cuddlyable3 (talk) 21:02, 10 February 2010 (UTC)

Lets not be overdramatic. A slightly increased risk of skin cancer is a more realistic description of the consequences of a weakened ozone layer. 169.139.217.77 (talk) 16:48, 11 February 2010 (UTC

Water

How many grams is 1 mL of water? --75.28.55.39 (talk) 23:35, 9 February 2010 (UTC)

1.0 grams. Dragons flight (talk) 23:39, 9 February 2010 (UTC)

Source: Density_of_water#Density_of_water_and_ice. Mitch Ames (talk) 23:55, 9 February 2010 (UTC)

This is in fact one of the defining conversion factors as specified by the metric system (or "International System of Units"). Note that if extreme accuracy is relevant, you must also specify the temperature and pressure - though this does not make a huge difference under most circumstances, it can have up to ~ 5% difference at atmospheric pressure as the water temperature spans from freezing to boiling. (For the extremely nitpicky readers, see kilogram and meter for discussion about even more exact definitions of the units that are not subject to these sort of "practical details"). Nimur (talk) 00:18, 10 February 2010 (UTC)

Obligatory nitpick: this was originally one of the defining conversion factors of the system, before the establishment of "more exact definitions of the units that are not subject to these sort of practical details". I'm only nitpicking the word "defining"; when they changed the formal definitions they were careful to keep all the units the same size they were originally. --Anonymous, 04:50 UTC, 2010-02-10.

Yes, that's absolutely correct - the modern definitions don't depend on the physical properties of water - I should have said "historically." Nimur (talk) 06:44, 10 February 2010 (UTC)