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

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April 8[edit]

Make OH Hydroxide[edit]

Is there a way to create OH(hydroxide) with household or easy-to-get inexpensive materials?The Successor of Physics 04:24, 8 April 2009 (UTC)

Yeah, dissolve Crystal Drano or Red Devil drain opener in water, and you get lots of it. (Disclaimer: if you create an explosion or burn yourself, you have only yourself to blame.) Looie496 (talk) 04:51, 8 April 2009 (UTC)
Indeed. In ordinary distilled water there are trace amounts of detectable hydroxides (about 1 x 10-7 mol/liter on average). This is true in the purest of water, due to a reaction known as the autoionization of water. Drano will give you GOBS of the stuff, but is also highly caustic and toxic (you can get nasty chemical burns as it turns your skin into soap), and adding straight Drano to water is highly exothermic; it could heat the water to boiling, and it could spatter or splasg, at which point you could be covered with a highly caustic boiling solution. Not fun. Just about any high-pH substance will contain reasonable amounts of measurable hydroxide. Ammonia-water is basically a solution of ammonium hydroxide, and even simple soap, like say dishwasher liquid, will generate some hydroxide ions without being too dangerous. If you explained why you were interested in generating hydroxide, perhaps we could give you more direction... 12:38, 8 April 2009 (UTC)
Well, I wanted OH because I read somewhere that shining light on OH could make the highly dangerous H2O2 hydrogen peroxide which I wanted to make a rocket fuel with.The Successor of Physics 14:32, 10 April 2009 (UTC)
Well, actually all these responses seem to be about OH- . If TSoP really wants OH, as requested, that's a different kettle of fish. --Trovatore (talk) 00:23, 9 April 2009 (UTC)
Since he asked for hydroxide, we assumed he meant OH-. The uncharged ·OH is the hydroxyl radical. TenOfAllTrades(talk) 00:38, 9 April 2009 (UTC)
If you want H2O2, go to any nearby pharmacy and buy a bottle of it. "All you have to do" is separate it from the water in which it's dissolved (or remove enough water that the H2O2 concentration is sufficient for your purposes). I think if you're intending to make rocket fuel using "something you heard somewhere" without knowing more about what you're dealing with, we probably shouldn't be providing more details about this. DMacks (talk) 15:02, 10 April 2009 (UTC)
So what I should do is goto a pharmacy and buy a bottle of hydrogen peroxide and separate it from the water it is dissolved in. Can I remove the water by evaporation(H2O2's boiling point is 150.2 °C but water's boiling point is 100 °C)?The Successor of Physics 11:19, 12 April 2009 (UTC)

Why does accelerating a charged particle produce radiation?[edit]

What is the actual physical reason for this? —Preceding unsigned comment added by (talk) 06:29, 8 April 2009 (UTC)

Acceleration in general (including linearly)? Or only circular? The latter is Cyclotron radiation or Synchrotron radiation, caused by the deflection or bending--centripetal acceleration--not just increasing speed. DMacks (talk) 06:58, 8 April 2009 (UTC)
Yes particularly circular acceleration. Why does bending the electron create radiation? (talk) 07:31, 8 April 2009 (UTC)
The explanation is the same whether it's circular motion or accelerating linear motion. A radiating field consists of disturbances in both the E and H fields, perpendicular to each other. The H field is the time derivative of the E field, and the E field is minus the time derivative of the E field. This is a self-reinforcing relationship that causes an EM wave to propagate indefinitely through space. A charge moving at constant velocity won't create this relationship, because the E field is changing linearly and so the H field, which is the derivative of the E field, is constant. Changing E + static H --> no radiation. If you have an accelerating charge (whether that acceleration is linear or circular doesn't matter), then both the first and second derivatives of E are non-zero, so now you have changing E + changing H --> radiation.
Synchrotron radiation is just a special case of this. If the charge is going round in a circle then all the radiation comes from a finite area instead of being spread out in an infinite line. This makes it a more convenient source for experiments. --Heron (talk) 18:04, 8 April 2009 (UTC)

optical reflection distortion in tempered glass in automotive[edit]

dear sir,

I want to know which standards/methods has to follow to check optical reflection distortion in tempered glass. As per my information it is present in DIN standard , but i dont know it . I want to know the standard no. and why this occure during production of automotive glass and how to judge it. —Preceding unsigned comment added by Ravscapc (talkcontribs) 07:28, 8 April 2009 (UTC)

could a fast enough solar-powered car catch more sunlight?[edit]

Imagine if you had a raindrops powered car. It would make sense that if it were going very fast through raindrops it would be catching more of them. Is the same thing true of a solar-powered car going fast thorugh sunlight versus being stationary? (talk) 08:01, 8 April 2009 (UTC)

Check out this derivation of the "simplified total wetness equation" by the BBC News. The answer is yes, but since the speed of (sun)light greatly exceeds that of your car (unless it's a really fast model), you'd only get an ultra teeny tiny improvement. Clarityfiend (talk)
No. Regardless of speed of your car, your car will measure speed of light to be same, and number of photons hitting the solar cells will be same and hence gathered solar energy will be same. In fact, if your call travels too fast (relativistic speed), your car will put on more mass, making it difficult to drive faster using the same quantity of solar energy. manya (talk) 09:13, 8 April 2009 (UTC)
Manya, I'm sorry to say that we're not discussing the change in the speed of light here and I think you have misunderstood the question, although what you mentioned about relativistic effects is true. My answer would be yes, and essentially the same as Clarityfiend's answer.The Successor of Physics 09:45, 8 April 2009 (UTC)
(@Superwj5: I have un-struck Manya's answer that you so rudely struck-out. We do NOT go around striking out answers we don't agree with unless they flagrantly break the WP:RD rules. If you think a previous answer is wrong - you must explain why you think it's wrong - not just cross it out...after all - you could just as easily be wrong - and in this case (as it happens), I think you are entirely wrong. Please consider your knuckles firmly rapped!) SteveBaker (talk) 12:48, 8 April 2009 (UTC)
Actually - I believe Manya is correct and Superwj5 has not considered the matter carefully enough. The speed of light is constant in all reference frames - so the car sees the speed of light coming from the sun as being the same no matter what speed it's travelling at. However, there would be a 'blue-shift' in light coming from in front of the car and a red-shift from the rear - and I think that means that the light coming from the front has more energy (I'm not 100% sure about that - with relativistic stuff, it gets complicated). But that only applies when the car is driving towards the sun - whatever that effect was, it would cause you to lose energy when driving away from the sun. When the sun is vertically overhead or off to one side - there is no benefit either way. Photons are in no way like raindrops! However, it's pretty clear that whatever the effect is, it's entirely negligable at all 'reasonable' speeds. SteveBaker (talk) 12:48, 8 April 2009 (UTC)
The Michelson-Morley experiment indicates that a light source that is directly overhead remains overhead regardless of horizontal motion of our car. Hence there would be no change in the energy collected by a horizontal planar solar cell.Cuddlyable3 (talk) 16:57, 8 April 2009 (UTC)
I'm fairly certain that there's another effect that causes light moving perpendicular to the observer to blueshift. I think it also makes the light move in the opposite direction of the observer from their point of view, which is contradictory to what Cuddlyable3 said, so can someone double-check this? By the way, the OP was comparing this to hitting more raindrops, rather than hitting them harder, so maybe we should also think about how many photons hit. — DanielLC 17:21, 8 April 2009 (UTC)
DanielLC is confirmed with Relativistic aberration. Is anyone up to drawing some diagrams to illustrate this article? It could really do with picturesque adornment. Relativistic beaming talks about the variation in apparent intensity at different directions. Graeme Bartlett (talk) 21:51, 8 April 2009 (UTC)
If your rain collector is horizontal and sitting on the roof then it will collect the same amount of rain regardless of speed. Imagine a loop of identical rain-collecting cars on a closed track: they will collect the same amount of rain moving as they do stationary because both the total available rain and the total collecting area are unaffected by the speed. The reason this differs from the "wetness equation" that Clarityfiend linked is that they're also counting rain that hits your sides. If you have rain collectors on the sides/front/back of the car then you will collect more rain when you start moving (moving relative to the horizontal speed of the rain). Interestingly, the amount of rain you collect sideways has no direct dependence on speed or elapsed time, it's solely a function of the distance you travel. More precisely, it equals the rain density times the volume of the tube of space you occupy during your trip. So to minimize rain on your sides you want to head straight for the nearest shelter, and to minimize rain on your head you want to get there as fast as possible. (I'm assuming a cylindrical cow here, of course.)
With respect to the rest frame of the moving car there will be aberration: the rain/light will appear to be coming from in front of you if it was initially coming straight down. The rain/light will also have a higher energy per particle (Doppler shift in the light's case, I don't know if this has a name in the rain's case). Since the collected particle count is the same, you're getting more energy overall. This isn't as great as it sounds because it's kind of an artifact of the frame-dependent definition of energy. Since rain and light both carry momentum, they will also push you backward as they pummel you from the front, so you have to fight this by accelerating harder. You won't get a mixed redshift and blueshift in this situation because the light/rain is all going in the same direction. Everything will be blueshifted (if it was initially coming straight down).
When you add special relativity, with respect to the initial rest frame, Lorentz contraction means that the collecting area (on the top of the car) decreases by a factor of γ at high speeds, hence the count of collected particles per unit coordinate time goes down by the same factor. But the particle count per unit proper time gets another factor of γ, so it's independent of speed as in the nonrelativistic case. I don't think it's possible to push the relativistic analysis very far because too many of the problem's assumptions stop making sense (you can't accelerate to relativistic speeds using the friction of wheels against a road, for example). -- BenRG (talk) 10:41, 9 April 2009 (UTC)
Thanks, BenRG! That's my point, you have collectors all around(I didn't have time to point it out last few days)! Also, the front back sides don't face Lorentz contraction but the light will be blueshifted so the total collected energy will be higher, according to BenRG and my initial assumption that the energy collected on the top doesn't vary.The Successor of Physics 06:55, 11 April 2009 (UTC)

why isn't the segway a unicycle?[edit]

i don't get why the segway isn't a unicycle, wouldnt it have to do the same job just with half the parts?

also why not sit over a ball (like an old mouseball) then it could roll in 2 dimensions instead of just 1 + turning? (talk) 08:21, 8 April 2009 (UTC)

1 wheel would be less stable than 2 wheels. I know it does the gyroscope/whatever thing but it'd increase the workload on it. The ball would add more friction, making it require more 'effort' (power) to move it around. The wheel has a small amount of surface in contact with the path/road, whereas a ball would (I expect) have more. (talk) 08:37, 8 April 2009 (UTC)
why would you expect it would have more contact? A plane is tangent to a wheel in only 1 point, and it is also tangent to a sphere in only 1 point. How much friction there is would just depend on what PSI you pump the wheel/sphere to, wouldn't it? (the more it sags the greater the actual touching surface area). Why would 1 wheel be less stable than 2 wheels? People are able to ride unicycles... (talk) 08:42, 8 April 2009 (UTC)
Riding on a plane needs minimum 1 or 2 wheels. Riding on a sphere needs minimum 3 wheels (which you find inside an old mouse), that's 4 frictional contacts including ball-to-ground. Cuddlyable3 (talk) 16:43, 8 April 2009 (UTC)

But riding a bicycle is much easier than riding a unicycle, because balancing on a bike is much easier...Also it seems from reading the Segway article that it constantly rotates/moves both wheels to maintain its position - I suspect on 1 wheel that would be harder to achieve (and potentially much the same on a ball). (talk) 09:18, 8 April 2009 (UTC) right|200px

The segway doesn't use a gyro to make it balance - it rotates the wheels forwards or backwards to keep them under the center of gravity of the segway+rider. That's why you lean forwards to make it accellerate and backwards to make it stop or reverse. If you watch a segway when it's just sitting there, perfectly balanced, you can see the wheels moving microscopically to keep the thing balanced. The gyro inside is just it's way to measure how it's moving. Hence, to make a unicycle segway with just one wheel would be impossible because the wheel can't rotate sideways to keep the unicycle vertical in the side-to-side direction. A human unicyclist has to supply lateral balance by leaning from side to side. A segway that rolled on a ball could possibly fix that - but now it would need two sets of motors and two sets of gyro's - one for forwards/backwards motion and another for lateral balance. This would make it considerably MORE complex - not less. It might also make it exceedingly difficult to ride because when you leaned a little sideways - the "ballway" would tend to roll in the direction you're leaning. Since you need to lean into corners in order to keep your balance - the ball would presumably rotate such as to keep you vertical - which would result in you failing to turn corners at all (I's confusing!). Anyway - on complexity grounds alone, it's a bust. However - having said that - you might want to check out Uno (vehicle) - which is almost a unicycle "motorbike" that balances in the forward/backward direction using technology similar to the segway and uses a split center wheel to manage lateral need to read the article to understand it in more detail. SteveBaker (talk) 12:32, 8 April 2009 (UTC)
I think you're assuming that the Ballway would not change heading. (And perhaps it wouldn't, That would not be easy to build.) If you're leaning purely to the right you want the Ballway to sidestep to the right, but if you're leaning forward and to the right, then it's entirely acceptable to travel in an arc. That would keep you balanced.
Ideally the Segway's wheels do exactly what you would do with your own feet. When you walk, you lean forward a little, and then move your feet forward to keep them "under" you, the segway attempts to do the same thing with its wheel. (I rode one once. It's a weird feeling. It felt like the thing was reading my mind.) Since humans are perfectly capable of leaning into a turn I don't see why a Ballway couldn't do the same. APL (talk) 16:40, 8 April 2009 (UTC)
If it had a ball, it would have to be able to move forward/backward, left/right, and clockwise/counterclockwise. That's three degrees of freedom. You can only lean forward/backward and left/right, so you'd have to have another degree of freedom to control it. It's possible to make it so you can control it with just the two degrees of freedom, but you won't be able to do everything that it's mechanically capable of, for example: if you make it so you lean forward and to the side to make it turn, how do you make it go diagonal? It's mathematically possible to map three dimensions completely to two, but you'd up with a ridiculous control system (see space-filling curve). — DanielLC 17:13, 8 April 2009 (UTC)
That extra degree of freedom really isn't a problem though. The Segway only uses the balance/leaning thing to do acceleration and deceleration. For steering, you have a twist-grip thing. Because the same mechanism is used for controlling the gross motion of the segway as is used to make it balance - you really can't make leaning be the control for steering in our ballway. When you lean sideways - the machine MUST roll sideways (without turning) or you'll fall off! I imagine our ballway would have to have some kind of additional controller for rotation - just as the segway does. Hence, y concern is that when you use this additional controller to rotate the beast - you'll be forced to lean into the turn to counteract centrifugal force - and when you do that - the lateral balance system would roll you sideways - making your turn into a messy affair indeed! In fact, you'd have to take turns pretty gently because with the machine FORCING you to ride upright (because as fast as you try to lean, the machine counteracts that) - the centrifugal force in a turn would throw you off. SteveBaker (talk) 18:09, 8 April 2009 (UTC)
I'm unconvinced. Even if your analisys is correct, there's no reason the software couldn't compensate for this. Afterall, it's a 100% predictable effect. (If you lost the ability to go forward at high speed, change heading, and add an additional diagonal component all at once, then there's no great loss. I'm not confident I could do that with my own two feet. Let alone a computerized beach ball.)
But I'm not sure you are correct. Imagine if you used an accelerometer to measure your "levelness". The force from gravity as a result of your lean would be the same as the centripetal force from the turn, exactly balancing it out. That's why we do it.
Since the segway is designed to mimic the actions of our own two feet, I don't know why anyone in their right mind would program a 'lateral balance system' that would attempt to keep you strictly upright while you were cornering.
The logic of the Segway and other self-balancing systems has always been "Move the wheels towards the center of gravity." That would still work. The tricky part with the BallWay would be determining which way the user should be facing. I think some inteligent rules could catch most cases. APL (talk) 19:53, 8 April 2009 (UTC)
it seems you're thinking the ballway wouldn't have handlebars (which would define "which way the user should be facing") but why not? You think it should just be a platform? no way, that's why the segway isn't like a skateboard (no handelbars) but a scooter (has handlebars). shouldn't the ballway have some too? .... wait, do you mean determining which way the whole contraption should be facing? just face it whichever way is set by the handlebars then? i dont really get your point of concern... (talk) 22:30, 8 April 2009 (UTC)
Of course it would have handlebars, but how does it know which way the handlebars should be facing?
(Does the user want to go diagonally forward and to the left? Or does he want to go forward and turn to the left? Both would keep him balanced if he's leaning forward&left. )There's some ambiguity that would have to be worked out with some sort of logic. APL (talk) 12:42, 9 April 2009 (UTC)
Maybe I'm not communicating it right, but my problem with SteveBaker's comment was that he seemed to be conflating "Staying Balanced" with "Staying upright". They're really only the same thing when you're stationary. APL (talk) 12:52, 9 April 2009 (UTC)
If you google for "electric unicycle" and take the first link found, there are instructions for making your very own. The site has some info about balancing. This is a proper unicycle too, unlike the Uno (vehicle). I can ride a unicycle and when I was learning, I never had any problems with side-to-side balance once I could get some forward motion. -- (talk) 22:59, 8 April 2009 (UTC)

Quantum harmonic oscillator[edit]

what is the perfect defination of Quantum harmonic oscillator ?Supriyochowdhury (talk) 10:12, 8 April 2009 (UTC)

I don't really understand your question, but it might be answered by our article quantum harmonic oscillator. Algebraist 10:20, 8 April 2009 (UTC)

why the wave function corresponding to the E-nu for a simple harmoic oscillator are nondegenerate.Supriyochowdhury (talk) 10:23, 8 April 2009 (UTC)

why would they be degenerate? Degeneracy in a quantum-mechanical system is usually a consequence of a symmetry of some sort. Now, consider a quantum harmonic oscillator (a spinless particle in a one-dimensional parabolic potential). What kind of symmetry do you suspect here? Why would you expect any two or more states to be degenerate? If you are thinking about x => -x symmetry, it leads to no degeneracy as it produces no new states that are linearly independent from the "old" ones. Or do you mean something else? You can make the states degenerate if you ascribe your particle a nonzero spin, but that is just adding another dimension. Conversely, you can add another spatial dimension, that would also make your states degenerate. Is that what you want? Think about it. --Dr Dima (talk) 19:36, 8 April 2009 (UTC)

Mom's perception[edit]

Do mothers have a distorted perception of danger? Are they influenced by any hormone to watch carefully for danger?-- (talk) 10:51, 8 April 2009 (UTC)

Due to maternal instincts, a mother may be more risk averse regarding the child's well-being than the child. So the negative implications of a factor that would increase the child's risk carries a higher "weight" than the positive implications of a factor that equally decreases the same risk. I'm not sure if that's a distorted perception. Regarding the hormone, oxytocin (which is released during labour and breastfeeding) is thought to influence the maternal bond. From the article:
"Rat females given oxytocin antagonists after giving birth do not exhibit typical maternal behavior. By contrast, virgin female sheep show maternal behavior towards foreign lambs upon cerebrospinal fluid infusion of oxytocin, which they would not do otherwise."
See the article for the refs. Zain Ebrahim (talk) 11:31, 8 April 2009 (UTC)

A squalling baby is incredibly irritating but a mother seems to have hearing uniquely sensitive to that sound combined with specific mental (protective) and neurophysical (lactation) responses. I observe that a cat mother seems to have very little idea of how many kittens she has, which may be a source of worry that one may be lost, but is content if she has sniffed them all. Cuddlyable3 (talk) 16:22, 8 April 2009 (UTC)

Is it possible to predict an unknown element's attributes?[edit]

I'm interested in creating believable fictional elements, sort of like how people create believable fictional worlds with defined orbital distance and such. The only problem is that there doesn't seem to be any information on this topic, anywhere.

So is there a reliable, or at least somewhat believable, method to determine which attributes an element could have? What, exactly, causes an element, or compound containing a certain element, to be more prone to acidity, magnetism, and other features? What about its appearance--thickness, weight, color? Can these kinds of properties be determined or assumed from basic knowledge such as atomic weight, number of electrons, placement on the periodic table or relation to other elements, etc.?

Basically I'm just looking for guidelines. What can one realistically expect from an unknown element? What are the possibilities? What defines the possibilities? Is the lack of information on this subject due to the fact that an element's properties cannot be predicted accurately, or just because nobody else cares? —Preceding unsigned comment added by (talk) 13:09, 8 April 2009 (UTC)

At this point, the only unknown elements in this universe will be very unstable. Generally, an element will be somewhat similar to the elements in the same column on the periodic table. Noble gasses are pretty inert, Halogens are rather reactive etc. (talk) 13:18, 8 April 2009 (UTC)
It's not certain that all super-heavy elements (and their isotopes) will be unstable - there may be an island of stability. Dog Day Today (talk) 13:32, 8 April 2009 (UTC)
I should note that when the periodic table of elements was created, it functioned very well at predicting elements' properties. Dmitri Mendeleev was able to predict some of the properties of ekasilicon (germanium), ekaaluminium (gallium), ekamanganese (technetium), and ekaboron (scandium) just from their positions in the periodic table. Once you knew where your new element fits on the periodic table, you can semi-convincingly determine its chemical properties. -- (talk) 14:40, 8 April 2009 (UTC)

Yes and No. "Yes" because you can predict anything you like (and you would have to work hard to predict something that someone somewhere would not reject as unbelievable). "No" because fictional creations are speculations not predictions (if by luck they turn out to be true then they are no longer fictional). The believability of a fictional element is increased by incorporating some known physical chemistry. Example 1: Dilithium crystal in Star Trek is supposed to be an element with atomic weight 87 and remarkable properties in crystal form. There really is a dilithium molecule but the rest is believable fiction. Example 2: Superman has problems with Kryptonite which is a fanciful element with no more than a name similarity to Element no. 36. Example 3: Melange (fictional drug) is a substance that plays an role in Dune (novel) but is IMO the least believable example. If your aim is to invent an element for a story I suggest that its "entertainment value" is more important than its believability to chemists. Cuddlyable3 (talk) 16:05, 8 April 2009 (UTC)

Your question covers interesting areas of science. Scientists do care about predicting the properties of elements, particularly to test the abilities of computational chemistry and to search for possible allotropes and polymorphs not yet discovered experimentally. I imagine atomic physics does a great deal of computational and theoretical work trying to predict and understand the properties of atoms of as-yet-undiscovered elements.
One very important use of such interplay of theory and experiment is that it tells you if your theory is along the right lines. The fact that the periodic table allowed Mendeleev to accurately predict the existence and properties of undiscovered elements suggested it reflected something very fundamental about atoms. Science works on cycles of:
  • do an experiment
  • make a theory to explain the results
  • predict some new results with your theory
  • do experiments to see if the predict results actually happen
  • if yes, the theory is good (for now); if no, need to modify or abandon the theory.
If you want to create believable but fictional substances, you might be better off inventing fictional compounds rather than fictional elements - there's a lot more scope for undiscovered possibilities that would be stable - new compounds with unexpected properties are being discovered all the time.
Ben (talk) 17:07, 8 April 2009 (UTC)

The problem with inventing new elements is that the definition of an element basically revolves around the number of protons it has. Since that's a simple integer - and all of the elements up to well over a hundred are already 'known' - the only imaginary ones you can possibly have will need an ungodly number of protons. Sadly - it's all to easy to predict their properties...they fall apart in an alarmingly small number of milliseconds producing fairly boring elements and perhaps some stray radiation in the process! All of the very high numbered elements do that. There is some theoretical discussion of an 'island of stability' - a region where even an ungodly number of protons might hang together if the number of neutrons were just right. We don't yet have a way to make these high-atomic-weight elements right now - but the fact that we don't find them in nature is indicative that the island of stability either doesn't exist or is exceedingly hard to reach. This is really only theoretical - but I suppose you could use it as the basis of your fictional account. Personally, I agree with Benjah-bmm27 - you are better off thinking of imaginary compounds. There are (effectively) an infinite number of possible compounds - and we are only just learning of the near-magical properties of some of the weirder ones. Things like carbon nano-tubes, for example. Sadly - the prediction of their properties (especially the really weird ones like nano-tubes) is virtually impossible - which is what keeps chemistry from becoming a branch of physics! SteveBaker (talk) 18:02, 8 April 2009 (UTC)

Wow, what a reply. Thank you, everyone, this is all really helpful stuff. I should've thought to ask this here a long time ago! (talk) 20:14, 8 April 2009 (UTC)

Alternative engine vehicles[edit]

I would like a list of all currently available hybrids, electrics, or PHEVs that can currently be ordered or will be available with the 2010 model year. —Preceding unsigned comment added by (talk) 13:11, 8 April 2009 (UTC)

In what location? Some may even be sold in only one section of a single country (as was true of the GM EV1). The Category:Green vehicles looks like a good place to start but I doubt that we have a premade list of all current models anywhere. Rmhermen (talk) 13:46, 8 April 2009 (UTC)

Sorry - USA. Good point.

Effect of Centrifugal Force on Oceans[edit]

putting back in own heading again...Matt Deres (talk) 20:20, 8 April 2009 (UTC)
As the earth rotates, centrifugal force causes ocean water to be deeper at the equator than at latitudes farther north or south. Has the greater depth at the equator due to this been calculated? One result of this effect will be that as global warming increases, flooding of land areas will be worse near the equator and less in areas farther north or south. – GlowWorm. —Preceding unsigned comment added by (talk) 15:23, 8 April 2009 (UTC)

What we call flooding is relative to the normal coastlines that already include effects of tides and centrifugal force. Holland is far from the equator but would be among the worst hit by a global rise in sea level. Cuddlyable3 (talk) 16:29, 8 April 2009 (UTC)
The Centrifugal force really does have an effect, but the effect is felt by the whole planet, not just by the oceans. The earth as a whole is not sufficiently rigid to hold its shape against centrifugal force. Yes, the ocean surface at the equator is farther from the center of the earth than is the ocean surface near toe poles, but this si also true of the ocean bottom. see geoid. -Arch dude (talk) 21:37, 8 April 2009 (UTC)
Yes; the interior of the Earth is fluid and the entire Earth can be thought of as a sphere of liquid rotating in space in hydrodynamic equilibrium, with a thin solid crust. The centrifugal force makes the radius at the equater bulge out 21.3 km (13.2 miles) greater than at the poles. Except for local features such as continental plates the crust follows this surface of equilibrium (geoid), so the oceans are no deeper on average at the equator than at the poles. --ChetvornoTALK 06:15, 9 April 2009 (UTC)
OK, that's a good point about the earth itself bulging at the equator. But as more water is added to the oceans because of melting polar ice caps due to global warming, centrifugal force will bring more of the water to equatorial regions compared to areas farther north or south. And yes, Holland may still be severely affected. So will the city of New Orleans in the US. Bangladesh is closer to the equator, and a great deal of the country is at a very low level, so it may loose a significant part of its area. At least it will be slow flooding, so the people will be able to get out. – GlowWorm. —Preceding unsigned comment added by (talk) 07:00, 9 April 2009 (UTC)
I wold say that, if anything, there would be a small effect due to the fact that as ice from the polar regions melt and move equatorward to fill the oceans, the earth 's Inertia moment changes slightly, slowing down erth's rotation and reducing the ocean's bulge. The solid earth's bulge would also respond, but much more slowly and (temporarily) there would be more floding at higher latitudes then around the equator. I haven't done the calculations but would not be surprised at all if the effect turns out to be completely negligible. Aside from that, I can't think of any reason why the floding would be any different at different places on earth. Dauto (talk) 22:23, 9 April 2009 (UTC)
You could also argue that, as the ice caps melt, isostatic rebound will be stronger in polar regions than in tropical regions, so therefore the tropical coasts would sink relative to the poles. However, this is likely to be cancelled out by other factors, for example a constant melting into the ocean from the poles could cause more water to "pile up" around the poles. ~AH1(TCU) 01:49, 10 April 2009 (UTC)
With regard to the earth's inertia moment changing as water moves away from the polar regions, that's a good thought. But I think that effect would be extremely small. The Greenland ice cap is about a mile deep. The radius of the earth is about 4,000 miles. So the melt water from the ice cap has a tiny mass compared to the mass of the earth. The mass of other ice around the north and south poles is similarly relatively tiny. Regarding isostatic rebound, that's another good thought. But the loss of 1 mile of ice and the resulting isostatic rebound would make the earth very, very, slightly more oblate than formerly. (The earth would not rise to the former height of the ice.) As a result, the centrifugal force at the equator would increase very, very slightly, making the ocean at the equator very, very, slightly deeper.. – GlowWorm. —Preceding unsigned comment added by (talk) 04:52, 10 April 2009 (UTC)

Chemistry and lock, have any relation?[edit]

16:52, 8 April 2009 (UTC)bsm (=bimellahalrahmanalrahim) We must draw a plan for hacking door`s look that relate to chemistry any way, at least a little relation. we saw very ways but they are physically, completely. if there is any way or starting point? (talk) 16:52, 8 April 2009 (UTC)

Brute force! Destroy the lock with explosives, melt it, or dissolve it with Hg.
Ben (talk) 17:09, 8 April 2009 (UTC)
Freezing with liquid nitrogen could make the metal brittle and easy to fracture.Freezing could also inactivate the battery used for operating an electric lock, if it keeps a solenoid energized to hold it locked. Edison (talk) 17:30, 8 April 2009 (UTC)
Solids are solid and strong things are strong because of the bonds among their atoms. Take a solid, strong thing like a sledgehammer or crow-bar, for example. Or bones. Muscles contract because of chemical energy being released, so use those muscles to move those bones and kick down the door, swing a sledgehammer at it, or pry it open. DMacks (talk) 17:50, 8 April 2009 (UTC)
AKA MacGyver gets lazy? --Trovatore (talk) 22:19, 8 April 2009 (UTC)
On an utterly unrelated note: In Popular Culture DJ Clayworth (talk) 17:26, 9 April 2009 (UTC)
Make a replica of Humphrey Davy's 1808 vintage "Great Battery," which was constructed with 2000 pairs of zinc and copper plates in individual tanks of dilute acid. It could produce about 2000 volts and over an ampere, and an arc from it could vaporize all known substances. It operated by electrochemistry so it should fall within the assignment. Just (carefully! extreme hazards from electric shock, acid, and high heat, as well as likely damage to the corneas and retinas) use a couple of electrodes to create an arc and burn away the lock. Or use an oxyacetylene torch (again, chemistry) to do the same thing in a more modern way. Edison (talk) 22:39, 8 April 2009 (UTC)

Thank u, but these ways damge the lock. (writer) —Preceding unsigned comment added by (talk) 20:54, 9 April 2009 (UTC)

I see, so you have to leave the lock and door in its original condition. I don't know much about locks, and I'm pretty sure it depends greatly on the type and age of the lock, but you might be able to make a camera out of optical fiber (a fiberscope), feed it into the lock hole, and find the shape and configuration of the lock from the inside. The "chemistry" part of it would be the fact that you're taking advantage of the refractive properties of the material used in the fiber. The hard part is creating a key to the shape that you decipher using the fiber optic camera. (talk) 05:42, 10 April 2009 (UTC)
Pour rubber solution through the keyhole, wait for it to set, then pull out the solid rubber through the same hole. You now have a reverse mould of the lock mechanism. I don't know if there is any rubber that could withstand that much deformation, but you didn't say whether you wanted practicable ideas or not. --Heron (talk) 13:25, 10 April 2009 (UTC)
Go to the owner of the building and say "Hey - I'll give you this really nice chemistry set if you'll let me into your building for a couple of minutes." SteveBaker (talk) 22:49, 10 April 2009 (UTC)

HHH like Norwegian physician!

why don't we use the sun as a fusion generator?[edit]

i dont mean to be difficult but it seems that space is empty as you just have to fling something and then wait. so it's only a matter of waiting (and flinging in the exact correct trajectory) that separates something from earth orbit from the sun. so the sun is a huge fusion generator, and except for a bit of a wait after you've flung something at it, it is as easy to get to as earths orbit. so why dont we use it as close fusion generator? (sorry if i am misunderstanding something basic -- ive gotten a lot of flack elsewhere recently and have tried searching. thanks. (talk) 22:12, 8 April 2009 (UTC)

The Sun already puts out as much energy as we actually want it to. If it put out more than it does, global warming would be an even worse problem than it is now. The difficulty is collecting that energy. --Trovatore (talk) 22:17, 8 April 2009 (UTC)
you don't see a difference between being as near to a huge fusion reaction as you want, 1 foot, 100 feet, 10000 feet, 100000 feet, etc, versus being able to build as large a solar panel as you want? i think there's a huge difference between having it in a few square meters and having it dispersed all over earth... (talk) 22:34, 8 April 2009 (UTC)
That aside, it might be an interesting calculation to see how much energy would eventually be returned from 1 kg of hydrogen delivered to the Sun, versus the energy it takes to get it there. My intuition is that the return would be many orders of magnitude less than the investment, but I haven't actually run the numbers.
On another note, if you don't mind a bit of waiting, please send me a million US dollars. I'll pay you back one dollar a year, for a billion years. You get a 100000% ROI! --Trovatore (talk) 22:26, 8 April 2009 (UTC)
what? it doesn't take very long to get to the sun! also, you are discounting prevailing interest rates. (talk) 22:34, 8 April 2009 (UTC)
In case we haven't yet been specific enough, solar energy is the term you're looking for. Anything we flung at the sun would return as such, and we've already got more sunlight than we can convert. This doesn't even get into the problems of getting something not just to the sun but to fusion depth (most of the hydrogen in the sun won't ever be fused) or of collecting the energy once it's created (the Earth receives less than one half of one billionth of the Sun's output). — Lomn 22:35, 8 April 2009 (UTC)
Follow-up fun. Burning one mole of hydrogen (w/ required oxygen) produces 242 kJ. Fusing that same one mole of hydrogen produces 2.7 billion kJ.[1] So fusion is better, right? Except that, as noted above, the Earth doesn't intercept all of the sun's output. Divide by the one part in 2.2 billion that we receive from the sun and that fusion nets us 1 kJ -- one half of one percent that of simple combustion on Earth (and well before we consider the point Trovatore raised regarding energy costs to move the hydrogen). No, sending stuff into the sun doesn't do anything to meet energy needs. — Lomn 22:45, 8 April 2009 (UTC)
Eh, the sun's already fusing; there's no need to fling *any* hydrogen. I believe the question here involves placing a satellite around the sun to harvest more of the generated energy and send it back to Earth. This concept has been explored in science fiction before (Asimov comes to mind – we even have an article), but I'm not aware of any practical research. A simpler implementation would involve Earth satellites transmitting power. Trovatore has it right though—any additional harvested energy sent to Earth would potentially cause an increase in global warming. – 74  01:08, 9 April 2009 (UTC)   edited by 74  14:20, 9 April 2009 (UTC)
Oh, well, if you could somehow collect the energy up close, and then (perhaps even harder) transmit it back to Earth efficiently, you could power an awful lot of stuff without aggravating global warming. Most likely you'd actually alleviate global warming, because you could replace carbon-emitting sources.
What I thought the OP wanted to do was increase the total power coming out of the Sun, so as to be able to get more power out of the same area of photovoltaics or solar-thermal generators here on Earth. That would aggravate global warming.
But getting the power back to Earth in a usable form seems completely infeasible to me. It's not like you can string up a high-voltage line. There have been proposals, kind of blue-skyish but at least semi-serious, to put solar-power satellites in orbit and beam the energy back to Earth in some sort of microwave beam. But that's from very much closer. Trying to put a power satellite in low Sun orbit and from there put a microwave beam direct on the collection station, rather than (say) the entire county surrounding it, strikes me as outside the realm of engineering possibility. (But don't let that stop you, OP; if you can figure out how to do it you could be wealthy indeed....) --Trovatore (talk) 01:51, 9 April 2009 (UTC)
My favorite concept is to put antimatter factories in low solar orbit and bring the "batteries" down the Beanstalk. —Tamfang (talk) 03:33, 9 April 2009 (UTC)

my god, you people thought i wanted to hurl hydrogen at the sun??? it boggles the mind. the sun has more than enough fuel. MY QUESTION IS SINCE IT'S A WORKING FUSION GENERATOR WHY DON'T WE USE IT AS THOUGH IT WERE IN OUR BACKYARD? Because the only thing separating the sun from our back yard (ie Earth's orbit) is a bit of a WAIT while our gear hurtles, AT NO ADDITIONAL FUEL COST, through space.

Space is a near vacuum. You hurl something and it goes "forever" (if you avoid colliding with something). So the difference between GETTING RIGHT HERE and GETTING WAY OVER THERE is 0 grams of rocket fuel -- just a bit of a wait.

So the way I figure, if the Moon happened to have a continuing fusion reaction, we would damn well harness that. So since the Sun is just as close (minus the bit of a wait getting there -- but at 0 fuel cost, just a correct initial trajectory), why don't we harness THAT? Seriously. (talk) 09:35, 9 April 2009 (UTC)

We thought you meant that, because that was our best guess as to what you were talking about. Now I have no idea what you are talking about. What exactly are you proposing? Algebraist 09:41, 9 April 2009 (UTC)
to clarify, if there were a working, large-scale, self-sustaining fusion reaction on the moon, you don't think we'd be using it? My question is, why not do the same with the sun, it's the same as getting to the moon except a longer wait... (talk) 10:01, 9 April 2009 (UTC)
We are using the sun. What is your suggestion for how we should use it better? Algebraist 10:05, 9 April 2009 (UTC)
We're not using any of the sun's heat, but only a little bit of it's radiation from an average of one "astronomical unit" away -- that's 92,955,887 miles. Obviously we're not using the sun as a fusion reactor if we are doing it from 92 million miles away by means of collecting rays so weak you can just walk in them and at worst get sunburn. I mean 'fusion reactor' as 'fusion reactor' -- ie the thing scientists would build on Earth if they could! So why not use the one that's built already, and quite close and easy to get to? (talk) 10:09, 9 April 2009 (UTC)
Speaking for myself, I don't want a sun-sized run-away fusion reactor in my back yard at all. Quite happy to put it in someone else's back yard and collect all the energy I need from a safe distance - say, oh, about 100 million miles away, give or take. Of course, what we really need is a Dyson sphere. Gandalf61 (talk) 11:21, 9 April 2009 (UTC)

Try looking up how fusion generators actually generate electricity. Then when you've found that out, look at different means of transporting electricity. Then come back here and tell us what you think. (talk) 11:39, 9 April 2009 (UTC)

I think the problem is that the OPer doesn't clearly understand how a fusion reactor would be, and how fission reactors already are, used on Earth.
What we get out of such reactors would be/is merely heat. This heat (often transferred via an intermediate medium such as molten sulpher) is usually used to boil water into steam, whose pressure is used to drive turbines that generate electricity, which is currently (pun intended) the most conveniently transmissable form of energy.
The fact that the Sun is 93 million miles away and transmits its heat energy via electromagnetic radiation through space, rather than directly via conduction as in reactors on Earth, makes no difference to this overall process. Intercepting and converting the Sun's e-m radiation - called "sunlight" - is the only feasible way of extracting and using its energy.
This is precisely what the various existing solar power systems do, whether they gently warm water in sunlight-exposed pipes, boil it or melt other materials by concentrating sunlight with mirrors, or convert it directly to electricity with solar cells. Wind turbines also utilize the Sun's energy indirectly, since wind is ultimately caused by the Sun's energy differentially warming the atmosphere: so do "renewable sources" such as the burning of wood from trees, or ethanol made from plants, since plants merely change atmospheric CO2 into carbon-containing burnable molecules by photosynthesis, which is powered by the energy in sunlight.
"Fossil fuels" are merely another form of this, since they too (mostly or entirely) formed from plants which grew by photosythesizing sunlight. In fact, virtually all life on Earth is already entirely dependent on the radiation from the fusion-generated energy of the Sun. (The minor exceptions are bacteria in hot springs and various deep-sea creatures round geothermal vents - but we are already exploiting some geothermal energy as well.)
In short, the answer to the question "Why don't we use the Sun as a fusion generator?" is "We already are, and always have been."
So far, we're only tapping a small fraction of what we potentially could, and we should probably expand greatly our solar power generation from current levels. However, note that all of the sunlight we can currently intercept and use is already going to hit the Earth anyway and (neglecting what is immediately reflected) turn directly or indirectly into heat: by the above means we merely get a bit of work out of some of it it in a form we can easily use, and ultimately all that work itself also turns to heat.
We don't want to increase the Sun's heat imput to the Earth even more by, say, launching satellites to intercept more sunlight and transmitting the energy (perhaps via microwave beams) to us, because that would tend to raise the planet's overall temperature further - you may already have heard of Global Warming and the problems it is expected to cause. We certainly don't want to alter the Solar Flux unpredictably by tinkering with the Sun itself, but (perhaps fortunately) there is absolutely no way we currently know of by which we could do that.
Arguably, we shouldn't be be using any sources of energy that effectively create "new" heat (such as fission and fusion reactors) rather than converting what's already around, but the trade-offs in efficiency make the calculations very difficult - for example, it might use more resources/produce more waste heat building solar power systems to generate X kilowatt/hours than it would to build a fission/fusion plant to generate the same amount. But that's getting into a whole other argument when I've spouted on far too long about this one. (talk) 12:54, 9 April 2009 (UTC)
Whilst what you say is technically true - the effect of heat from the energy we're using is entirely negligable. The sun slings about 1kW per square meter at the earth's surface - 1.7×1017 Watts altogether (at ground level) - we are consuming about 1.6x1013 Watts to drive our civilisation. So even if 100% of our energy needs were to come from solar collectors orbiting out far from the earth - this would only add to the natural heat arriving from the sun by about one hundredth of a percent. This is certainly not a concern - and if we could thereby avoid creating the worst of the greenhouse gasses, it would cut the absorption of sunlight by vastly more than one hundredth of a percent - so this would surely be a huge win. Unfortunately we really don't have the technology to build orbiting solar collectors with an area of around 1010 square meters (four thousand square kilometers - something in orbit that's the size of Rhode island!) - plus the technology to somehow beam that energy down to earth without frying everything for a hundred miles around. So, as attractive as that is, it's not really feasible yet. SteveBaker (talk) 00:29, 10 April 2009 (UTC)
Aye, Steve, but "mony a mickle maks a muckle," as my Scottish great-great granny might have said if I'd ever met her. There's a lot of things we do or did that we thought would have negligable effects, but have come back to bite us (or the environment), so I'd rather we played safe. As you say, the technology for large-scale space-based solar energy collection is a long way off, but meanwhile, our worldwide energy (= heat) generation/use is accellerating, and the developing nations (India, China etc) seem likely to exacerbate that (is there a single word for accellerating an accelleration?). On this present course the effects of that energy/heat itself (ignoring the decidedly non-negligable side-effects of its likely generation methods) may not remain negligable. Partly, therefore for the psychological effect of setting an example and partly for its actual impact, I prefer the current emphasis on reducing our energy consumption (or at least slowing down its increase) by developing methods of doing things more efficiently, using less energy. The promise of unlimited extra solar energy might have a detrimental psychological effect on that effort. (talk) 13:15, 11 April 2009 (UTC)
OP, I'm not sure we're understanding you properly. Are you suggesting that we take a giant rechargeable battery, send it to do a close-pass to the sun, bring it back, and use the energy in the battery?
It's an interesting idea anyway, I'm going to suggest that we don't have the technology to capture and store enough energy to make the whole exercise worthwhile. APL (talk) 13:22, 9 April 2009 (UTC)
I agree. The number of batteries you'd need would be totally impracticable. Much better to put gigantic solar arrays in orbit...but we don't know how to do that either. SteveBaker (talk) 00:29, 10 April 2009 (UTC)
What? Build solar arrays? Put satellites in orbit? Or the unstated transfer of collected power? Just because we haven't doesn't mean we don't know how; see Space-based solar power. – 74  00:50, 10 April 2009 (UTC)
I think by 'we don't know how' SB meant we currently have no pratical way to do it for a price that would make it worth doing and with actually getting a net energy return. Sure there are a lot of theories about how we could do it, just as there a lot of theories about how we could colonise Mars or the Moon but we're still a long, long way from actually knowing how to do it pratically. Nil Einne (talk) 11:10, 10 April 2009 (UTC)
If you "fling" something at the sun to capture its energy, how are you going to get that device back to Earth? Once it gets close enough to the sun to touch its atmosphere (if that's what you meant), alongside with the solar flares and magnetic disturbances, the device would be caught by the Sun's gravity and fall into the sun. How are we supposed to harness that energy, then? ~AH1(TCU) 01:42, 10 April 2009 (UTC)
Also, you may be interested in this. ~AH1(TCU) 17:21, 10 April 2009 (UTC)