# Wikipedia:Reference desk/Archives/Science/2010 February 10

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# February 10

## black hole event horizon

hello this is hursday. does black hole event horizon always have to be spherical or can it be other shapes? (Dr hursday (talk) 01:07, 10 February 2010 (UTC))

They have been known to share the topology of cup cakes and muffins. (Nurse ednesday.) —Preceding unsigned comment added by 58.147.58.179 (talk) 01:29, 10 February 2010 (UTC)
I believe they are always spherical. Even spinning and/or electrically charged black holes have spherical event horizons. However, the spinning ones also have another kind of "horizon" called the "ergosphere" that takes on the shape of a flattened sphere. SteveBaker (talk) 03:04, 10 February 2010 (UTC)
Probably stupid Theoretical question : Can't other nearby massive objects effect the shape of the event horizon? If I had a black hole that happened to be near another black hole, wouldn't the event horizon extend farther out on the side that faced away from the second black hole? What about the point at the center of gravity of the two black holes, couldn't that not be inside the event horizon, even if happened to be close enough to fall within a spherical event horizon? Or do I badly misunderstand? APL (talk) 03:26, 10 February 2010 (UTC)
I don't have time for a long answer right now, but yes, interacting black holes can give rise to a transient event horizon that is distorted into other shapes beyond the simple sphere. Dragons flight (talk) 04:18, 10 February 2010 (UTC)
Hello this is hursday again. yes i was wondering if the presents of other black holes around might distort the gravitational field enough to change the event horizon if so could then particle that is has passed event horizon of one black hole then have another large black hole zoom by it very fast and free the particle the particle would have to be in the event horizon of the black hole zooming by but the black hole couldnt be in the event horizon of the black hole or it would get sucked into the black hole as well. also I was wondering if at the point just after a large mass is absorbed into the event horizon would that not shift the center of mass of the black hole away from the center as the mass inside the event horizon is not equally distrubted? (~~~~)
Replying to hursday and APL: as far as I know, once you stop tossing stuff into a black hole, the event horizon becomes spherical, period. There's no equatorial bulge, no distortion by nearby masses, not even any Lorentz contraction (the horizon is spherical in any coordinates). This doesn't apply if there are gravitational waves around or if black holes merge (both of those count as tossing stuff in). It also doesn't apply to the black hole's gravitational field (outside the horizon), which can be permanently asymmetrical. It's never possible to free a particle from inside the event horizon because the event horizon is defined in the first place as the boundary of the region from which things can't get out. This does imply that event horizons are unphysical; they know the future in a way that physical objects can't. -- BenRG (talk) 06:55, 10 February 2010 (UTC)
Are you sure about the 'no lorentz contraction' bit? Dauto (talk) 13:55, 10 February 2010 (UTC)
Pretty sure. The black hole metric restricted to the event horizon is just ds² = rs² dΩ². There's no dt² or du² or whatever, because the third direction is lightlike. If you take any spacelike slice through the full geometry and restrict it to the horizon, it becomes a constraint of the form t(Ω) = something, but it doesn't matter because t never occurs in the metric. Contrast this with a sphere in Minkowski space, where you have ds² = R² dΩ² − dt² on the sphere and ds² = R² dΩ² − t'(Ω)² dΩ² on the sliced sphere. That factor of 1 − t'(Ω)²/R² is where the Lorentz contraction comes from. -- BenRG (talk) 05:38, 12 February 2010 (UTC)
Slight clarification - you don't just have to have stopped tossing stuff in, but you have to never be going to toss anything in in the future. As I understand it, any object that is going to cross the event horizon at any point in the future creates a (usually very small) dimple in the event horizon from the moment the black hole comes into existence (as you say, event horizons know the future). --Tango (talk) 10:02, 10 February 2010 (UTC)
Yes, the horizon is defined globally, not locally. And by globally we mean mass distribution everywhere past, present and future. The horizon is not a real physical entity. We might be crossing the horizon of a huge blackhole right now as we speak, and not even be aware of it. Dauto (talk) 13:55, 10 February 2010 (UTC)
Also, the singularity is hypothesized to be ring-shaped if the black hole rotates. ~AH1(TCU) 00:09, 14 February 2010 (UTC)

## Blue gold

I read on wikiarticle that blue gold exist. what does blue gold look like (Dr hursday (talk) 01:10, 10 February 2010 (UTC))

Bluish. See Blue gold (jewellery) (and the cited ref) for info about it. Sadly, I can't find an actual picture. See [1] ("thanks, google-image search!") Would be great to get a free set of pictures of colored gold for the article. DMacks (talk) 01:24, 10 February 2010 (UTC)
Depending on the context, it could have several other meanings as well. What article did you see the term in? A quick google search shows that water is sometimes called "blue gold", especially in political or economic contexts (see this, for example). And there are numerous references to blue and gold. Buddy431 (talk) 01:38, 10 February 2010 (UTC)

if you make these twin particles with opposite whatever, then why can't you just measure the position of one with high certainty (sending the velocity of that one into uncertainty) which position the other half of the twin then "will have had" all along, while doing the same thing for the other one but for the velocity? Then you know the initial velocity and position of both (though the current position/velocity of each respectively is uncertain). Isn't that disallowed by the heisenberg's uncertainty principle (thup)? Also thank you for clearing up any misconceptions I might have had. —Preceding unsigned comment added by 82.113.106.88 (talk) 02:15, 10 February 2010 (UTC)

Well, for one, the uncertainty principle isn't relevant to the EPR paradox as it's been experimentally tested and resolved (see Bell's theorem). The article ought to refer to the observer effect. The uncertainty principle is for continuous values, not the discretes (photon polarizations) of the EPR paradox. However, to address why the uncertainty principle can't be abused in such fashion:
${\displaystyle \Delta X\Delta P\geq {\hbar \over 2}.}$
In short, the product of the uncertainty of the position and the uncertainty of the momentum must be at least some positive value. If you were to set one uncertainty to zero (say position), then the other (possible momentum) would span an infinitely large range of values, or more accurately, would not be defined. It's not simply sufficient to say that you can't measure the definite position and momentum of an object at the same time. Rather, it is better to say that particles do not have definite positions or momentums to be measured, merely probabilities. — Lomn 04:14, 10 February 2010 (UTC)
Yes, but in this case there are two twin particles which originated at the same location and left it with exactly opposite (times -1) velocities. I see what you mean about one of them, call it A: if you know A's position perfectly, it's momentum could span an infinitely large range of values. So let's do that. Meanwhile, if you know B's momentum perfectly, then B's location would span an infinite range of values. But combining A and B, you can get the original location AND velocity of the particles at starting point... Can you address this? Everything you wrote above seems to be about one (either A or B) of the particles, rather than both... 82.113.106.91 (talk) 12:34, 10 February 2010 (UTC)
At the level involved, however, you don't know that the particles originated at exactly the same place (nor exactly where that place is), nor that they left with exactly opposite momentums (even where c is a given, the direction is not known with certainty). The Schrödinger equation, which describes the nature of a particle's position and momentum, is what illustrates that these concepts are not distinct values that can be known. It's not that you can't measure them because of some limitation in measurement -- it's that they don't exist as single answers to be measured. For an introductory book on the subject, I recommend How to Teach Physics to Your Dog. — Lomn 13:40, 10 February 2010 (UTC)
Your question is exactly the question that the original EPR paper asked. The obvious interpretation of the uncertainty principle is that the physical process of doing a measurement on a system must alter it in some way. For example, if you bounce a large-wavelength photon off the system, you alter the momentum only slightly, but get only a vague idea of the position; if you use a small-wavelength photon, you get a better idea of the position, but alter the momentum a lot. EPR had the idea (obvious in hindsight) of making two measurements that are separated in space so that no physical influence from one can reach the other, even at light speed. If the uncertainty principle is a side effect of physical "measurement interference" then it has to fail in this case. If it works in this case, it must work by some weird mechanism that's unrelated to ordinary physical interaction, which Einstein famously dismissed as "spooky action at a distance". Bell was the first to point out that the correctness of the uncertainty principle in this situation could actually be tested in real life. Subsequent real-life tests have concluded that it does hold—i.e., the bouncing-photon explanation of the uncertainty principle is wrong and the "spooky action at a distance" is real. The philosophical implications of this still aren't understood. -- BenRG (talk) 06:16, 10 February 2010 (UTC)
Thank you for the answer. Can you explain in simple terms to me what the actual "spooky" results are? What happens when you learn that of A .... B, which had been at one point but now have opposite velocities, A is moving due left at exactly "1230 units per second" (hence B will have been moving with that velocity all along) meanwhile, B is in such-and-such a place, exactly. Couldn't you combine the 1230 unites per second and the such-and-such place to get both components (momentum and location) perfectly? What actually happens when you measure the velocity of one half of the particles and the location of the other, with a high degree of accuracy? 82.113.106.91 (talk) 12:40, 10 February 2010 (UTC)
They are hard to break down in simple terms, unfortunately. (I've tried to do it for a few years now in teaching non-science undergraduates.) The less hand-wavy approach is to show how the statistics work. Mermin's classic article on this (referenced in the article on Bell's theorem) does this a bit; this page is derived from it and has a similar line of argumentation. Science people find that a useful way to simplify, but those less quantitatively inclined do not, in my experience. The basic answer is that your "I can have all the information approach," which was what Einstein thought, turns out not to work out correctly if you run your test over time. There is a testable difference between the quantum outcome and the EPR prediction.
Another approach is to jet all the actual explanation and just explain why it is spooky. Basically what you find is that when you measure one of the properties, it does modify the other property you are measuring in the paired particle even if there is no "communication" between the particles (in other words, even if there is no reason that it should). That's the "spooky" bit. One professor I had put it as such: Imagine there were two twins, separated by an ocean. Both happen to enter into a bar at the exact same time and order wine. When one orders red wine, the other one, instantaneously, knows they want white wine. If the first had instead ordered white, the second would instead order red. They have no communication between the two twins, no way that we know of to "know" what the other is ordering, yet each and every time their orders are exactly the opposite of their twin. Spooky, no? They (your particles) are truly entangled—one you do to one does affect what you do to the other—even if there doesn't seem to be any obvious reason why that should be. Again, this is testable (and is the basis for quantum cryptography). Unfortunately getting a deeper understanding of how this works is non-trivial. (I understand maybe half of it, having sat through quite a few lectures on it at this point.) --Mr.98 (talk) 13:33, 10 February 2010 (UTC)
Expounding on the spooky action: the part that leaves it consistent with the rest of physics (specifically, with c being the speed limit of information transfer) is that nothing can be learned by observing only the local one twin. I'd suggest that it's more accurate if you remove the bit about "both entering the bar at once" and instead go with this:
Imagine there are two twins, separated by an ocean, who both like wine. When one decides that he prefers white wine, the other's preference immediately becomes for red wine. When one decides that he prefers red, the other immediately prefers white. One twin enters a bar and orders red, and immediately, faster than the speed of light, the other prefers white. There's your spooky action. Now to fix information transfer: A scientist follows around Twin B, periodically asking him what wine he would prefer. The scientist doesn't know when Twin A enters a bar and orders wine. When Twin B answers "white", is it because Twin A just ordered red, or is it because Twin B had to answer something (because even if he could prefer either, he must answer one or the other)? The two are indistinguishable unless some other means of communication (which is limited by the speed of light) is used to inform the scientist about Twin A. — Lomn 14:17, 10 February 2010 (UTC)
The point is that the spookie action cannot be used to send a message. Dauto (talk) 15:36, 10 February 2010 (UTC)
Which means it doesn't violate special relativity, but it is still spooky! --Mr.98 (talk) 16:40, 10 February 2010 (UTC)
What you're describing here is Bertlmann's socks, which is easily explained classically. I know that you're trying to use an analogy that a layperson will understand, but I don't think it helps to describe "quantum weirdness" with an example that doesn't actually contain any quantum weirdness. The gambling game I describe below is a genuine example of nonclassical correlation, not an analogy, and I think it's simple enough to replace Bertlmann's socks in every situation. -- BenRG (talk) 20:54, 10 February 2010 (UTC)

You guys are not getting my question. Say the twins had two properties like speed and velocity that you couldn't simultaneously know. As an analogy, say they had a height and a weight, but the more exactly you measured the height, the less sure you could be of the weight. However, you do know that their height and weight is the same. So, you just measure the height of one very exactly (at the moment you do that, its weight becomes anything from 0.0000000001 to 1000000000 units and more - you've lost all certainty), let's say you get 5'10". Then you measure the weight of the OTHER with high certainty. Let's say you get 150 pounds. That means the height of the other becomes anything from 1mm to 1km and more. However, you do know that well before your measurements, the height and weight of each was the same. So, you can deduce that the height of each was 5'10.56934981345243432642342 exactly, to arbitrary precision, and that the weight of each was 150.34965834923978847523 exactly, also to arbitrary precision; this violates the idea that the more precisely you know one, the less precisely you know the other. It depended on the fact that the twins were guaranteed to be the 'same'. It's not about communication, you guys are misunderstanding. It's not faster-than-light communication that worries me. It's that you can just compare the two readings and come up with the above high-precision reading for both components. Now without the analogy: it was stated that you can get particles that have the exact opposite velocity when they leave each other from a specific place(entangled or not). My question is, using the analogy of height and weight, why can't you learn the height of one, and the weight of the other, after they have left their common source at the EXACT opposite 'height' (one is guaranteed to grow downward, below the ground or something). Is my assumption that two particles can be guaranteed to leave with opposite velocity from a fixed position wrong? Or what am I missing? It seems to me you could deduce the exact velocity /and/ position of both, by measuring the other component in the other.

Please guys, I'm not asking about information transfer! I'm asking, when you physically bring the two notepads with the readings next to each other, you now have both components of the original particles... how is that possible? Thanks for trying to understand what my question actually is, instead of answering more of what I am not asking. Thank you. 82.113.106.99 (talk) 16:49, 10 February 2010 (UTC)

Quote: "Is my assumption that two particles can be guaranteed to leave with opposite velocity from a fixed position wrong?" Yes, it's wrong. In order for them to have exactly oposite velocities the pair would have to be exactly at rest before, and in order for you to be able to pinpoint the position of A after measuring the position of B you would have to know exactly where they were before. So you need to know exactly both where the pair was and how fast it was moving before the split. Heisenberg's uncertainty doesn't allow that. Note that this has nothing to do with EPR paradox. It's a complete separate thing and doesn't require entanglement or spooky action at a distance. Dauto (talk) 17:53, 10 February 2010 (UTC)
Thank you, you're exactly right: my question had nothing to do with EPR, or entanglement or spooky action at a distance. The only connection was the experimental setup, getting particles explosively popping off of each other... Thank you for your answer, I think it makes everything very clear. Sorry that I didn't phrase my question more explicitly, this is very hard stuff for me :). 82.113.106.99 (talk) 18:09, 10 February 2010 (UTC)
(ec) I think we're getting your question—but I don't think you're quite getting the answer. (Which I sympathize with, because it is not the easiest thing to explain.) The point of Bell's inequality is that you do not actually get total information about the particles—that your measurement of one of them does affect your measurement of the other, and this is experimentally testable (it is not just a philosophical distinction). The issue of "communication" comes in because you then naturally say, "so how is that possible if the particles are different and unconnected—how could measuring one affect the other, if there is no connection between them?" --Mr.98 (talk) 18:00, 10 February 2010 (UTC)

### What's wrong with this loophole?

By the way, what's wrong with this loophole? I mean, where is the flaw in that math? Thanks. 82.113.106.99 (talk) 17:12, 10 February 2010 (UTC)

It's an issue of interpretation of what Bell's inequality means for quantum mechanics. You're going to have to understand Bell's inequality though before you are going to understand the different interpretations of local hidden variable theory... it is not a problem with the math, it is a question of interpreting the results. Bell's theorem rules out certain types of theories but not others. --Mr.98 (talk) 18:00, 10 February 2010 (UTC)
Here's a refutation of the paper, for what it's worth. The paper's conclusion is obviously wrong. What its publication really shows is that there are a lot of physicists who don't understand Bell's theorem.
Here's an example of what people like Hess and Philipp are up against. Imagine two people are playing a gambling game that's a bit like The Newlywed Game. They play as allies against the house. They're allowed to discuss a strategy first; then they're moved into separate rooms where they can't communicate with each other. Each one is then asked one of three questions (call them A, B, and C) and must give one of two answers (call them Yes and No). Then they're brought back together and receive a payoff depending on whether their questions and answers were the same or different. The payoffs are shown on the right. "−∞" is just a penalty large enough to wipe out any other gains they've made and then some.
 same Q diff. Q same A 0 −2 diff. A −∞ +1 Game payoffs
What's the best possible strategy for this game? Any strategy must, first and foremost, guarantee that they'll give the same answer when asked the same question. This means that there can't be any randomness; they have to agree beforehand on an answer to every question. There are eight possible sets of answers (NNN, NNY, NYN, …, YYY). NNN and YYY are obviously bad choices, since they will always lose when the questions are different. The other six choices all give different answers with probability 2/3 when the questions are different. Because of the way the payoffs are set up, this leads to the players breaking even in the long term. So it's impossible to do better than break even in this game.
But in a quantum mechanical world, the players can win. In the initial discussion stage, they put two electrons in the entangled spin state (|↑↑〉 + |↓↓〉) and each take one. Then they measure their electron's spin in one of three different directions, mutually separated by 120°, depending on the question, and answer Yes if the spin points in that direction or No if it points in the opposite direction. According to quantum mechanics, measurements along the same axis will always return the same value, while measurements along axes separated by 120° will return different values with probability 3/4, which is more than 2/3. Thus the players will win, on average, 1/4 of a point on each round where they're asked different questions.
Can you come up with a classical model that explains this? You are allowed to model each electron with any (classical) mechanical device you like; it may have an internal clock or an internal source of randomness if you want. It takes the measurement angle as input and returns Up or Down as output. The two electrons are not allowed to communicate with each other between receiving the question and returning the answer (that's the locality requirement).
Hess and Philipp think that they can win the game by putting an internal clock in their electron devices. I hope it's clear now that they're wrong... -- BenRG (talk) 20:54, 10 February 2010 (UTC)

## Burning down stone buildings?

I don't mean this kind of building.

Reading Herostratus makes me wonder: how is it possible to burn a stone building? I get the impression that ancient Greek temples were made of solid marble, not wood faced with stone, and of course I know that marble doesn't generally burn. Nyttend (talk) 05:24, 10 February 2010 (UTC)

Ancient greek buildings certainly had a framework and detailing done in marble or other stone, but there was also likely lots of flamable stuff (wood, tapestries, decorations, etc. etc.) all over them, so that could very easily burn. Furthermore, thermal stresses caused by the fire could cause the integrity of the marble structure to fail, ending up with a pile of rubble. Said pile would likely be recycled for use in other buildings, so in the end there wouldn't be much of the "burned" building left. --Jayron32 06:09, 10 February 2010 (UTC)

Cyrus the King of Persia commanded to build a row of wood between every three rows of stone in the walls of the Second Temple in Jerusalem, in order to make it easier to burn down the Temple in the event of a revolt.(Ezra 6:4; Babylonian Talmud, Rosh Hashanah 4a) Simonschaim (talk) 08:17, 10 February 2010 (UTC)

Roofs would often have been made of wood as well. Large spans like a roof covered only with stone are not simple. The Pantheon was (and is still) considered a marvel and its roof is concrete. 1 Kings 6 gives details of the large amount of wood (and where it was used) in the First Temple at Jerusalem. 75.41.110.200 (talk) 14:42, 10 February 2010 (UTC)
Yes, but the gold-plated cedar wood isn't typical of Greek temples; thanks for the point about the roof, however. Nyttend (talk) 15:52, 10 February 2010 (UTC)
I think IP 75.41. means Parthenon rather than Pantheon. -- Flyguy649 talk 16:26, 10 February 2010 (UTC)
No, he means the Pantheon, Rome, in many ways more impressive than the Parthenon. Mikenorton (talk) 16:31, 10 February 2010 (UTC)
I don't think anyone except the Romans used concrete in antiquity; nobody else could have built something with a concrete roof. Nyttend (talk) 21:10, 10 February 2010 (UTC)
Greek temples were built of wood until around the 6th century BC (see Temple (Greek)#Earliest origins) - although there had been a lot of stone temple construction by Herostratus' time, there would still have been some wooden temples around (one theory suggests that wooden elements were often replaced one at a time, as required). Indeed, an earlier Temple of Artemis was built of wood, but it was rebuilt as a grand, fairly early example of construction in marble. However, it had wooden beams in the roof and contained a large wooden statue. Warofdreams talk 16:21, 10 February 2010 (UTC)
According to the lime mortar article, it is made of calcium hydroxide, which decays at 512C. Silca sandstone melts at 1700C, but I can't tell the softening point. Wood fires can easily reach the melting point of copper (1000C), but not iron (1800C). So the mortar (which the Romans used, and probably the Ancient Greeks as well) would fail and the building is likely to collapse. However, this is not my area of expertise, so I'm just taking an educated guess. CS Miller (talk) 23:55, 10 February 2010 (UTC)
Also, marble (and chalk) is calcium carbonate, it decomposes at 1200C. Do you know what stones the building was made from? CS Miller (talk) 00:59, 11 February 2010 (UTC)
The article says that the temple he burned was built of marble. Is that what you mean? Nyttend (talk) 05:07, 11 February 2010 (UTC)
Oops, didn't see that you stated that the building was made of marble. A wood fire will reach the decomposition temperature of lime-mortar and marble. Both of these decompose to calcium oxide (quicklime). These decompositions are endothermic, meaning that heat-energy is absorbed, not released during the reaction. Calcium oxide has about half the molar density of calcium hydroxide and calcium carbonate, so the mortar and marble will double their volume on decomposition. Calcium Oxide is 16.739403 ml/mol, Calcium hydroxide (lime-mortar) is 33.511081 ml/mol, calcium carbonate in calcite form is 36.932435 ml/mol. So in short a wood fire could reduce a marble building to a large pile of quicklime, if there was enough wood. CS Miller (talk) 14:24, 14 February 2010 (UTC)

## heat pump

is chillers and heat pump are the same —Preceding unsigned comment added by 180.149.48.81 (talk) 08:43, 10 February 2010 (UTC)

See chiller and heat pump. The answers are there.--Shantavira|feed me 13:08, 10 February 2010 (UTC)
My house has one unit that is either considered to be a heat pump or an air conditioner depending on which way it's driven. It cools the house by heating the back yard and heats the house by air-conditioning the back yard. So in at least some situations, they are the same thing. However, there are air conditioners and heat pumps that are optimised for one specific function that are not intended to be reversible - so, in general, they are not necessarily the same thing. I suppose it would be most correct to say that a "chiller" is one application for heat pump technology. SteveBaker (talk) 20:14, 10 February 2010 (UTC)

## soft iron

i was reading about transformers and torroids and to conclusion that both are nearly same. emf is induced in both of them when current passes through 1 coil,in 2 coil. one more similarity is eating my mind is that why soft iron is used in both of them to wind wire - why not some another metal or ceramic? does soft iron has any role in producing emf or anything.--Myownid420 (talk) 09:23, 10 February 2010 (UTC)

Small toroidal core transformer
We have a brief explanation at Soft_iron#Common_magnetic_core_materials. I found this, as I hoped, by typing soft iron into the search bar. If you don't understand the explanation there, or want more detail, feel free to ask a more specific question. 86.183.85.88 (talk) 13:52, 10 February 2010 (UTC)
The article says nothing about its "softness" (it would make a lousy pillow). Is it the carbon content? Is it really "softer" in a physical sense than steel? Is pig iron from an iron furnace "soft" before it becomes "hard" by being worked or alloyed with carbon? How do wrought iron, cast iron, mild steel, tool steel, and stainless steel compare in "softness?" If I want to buy "soft Iron" where would I go and what product would I ask for? I only know that steel retains magnetism better than a nail which is supposed to be "iron." Edison (talk) 16:18, 10 February 2010 (UTC)
You could try Googling "soft iron" and looking at the third result. --Heron (talk) 19:24, 10 February 2010 (UTC)
I suggest it is safer to give the actual link since Google search results order can vary. Cuddlyable3 (talk) 20:31, 10 February 2010 (UTC)
The "third result" is for "curtain rods with a 'soft iron' finish." I expect that such rods are steel, which is strong and cheap, and that the "soft iron"" only refers to the appearance. Edison (talk) 05:05, 11 February 2010 (UTC)
The third result for me is a company that supplies science equipment to schools advertising that it sells packs of affordable soft iron rods for making electromagnets. I'm a little surprised that, with your username and the personality you choose to project, you appear to know nothing about soft iron, even 2 years after a similar conversation. 86.183.85.88 (talk)| —Preceding undated comment added 16:09, 11 February 2010 (UTC).
Yes, that's the one I meant. Sorry, I forgot that Google is localised. --Heron (talk) 18:44, 11 February 2010 (UTC)
Here are some articles and with their spellings in Wikipedia. A torus is a doughnut shape. A toroid is also round but more like a sawn-off piece of pipe. Two windings on a toroid- or torus-shaped core make up a toroidal transformer, it is exactly a transformer but not all transformers are toroids.
Materials such as steel that are good for making permanent magnets are poor choices of core material for a power transformer because their retention of magnetism after a field is removed causes power loss to heating by Hysteresis. "Soft" iron[2] has low hysteresis and is almost pure iron. It is a cheap low-grade structural metal and is also used to make Clothes hangers. Cuddlyable3 (talk) 20:31, 10 February 2010 (UTC)
I really would expect clothes hangers to be made of recycled steel rather than elemental iron. Edison (talk) 04:44, 11 February 2010 (UTC)
Plus ca change. You could get soft iron from a company that makes soft iron for the cores of electromagnets, for example. You can get iron of varying degrees of hardness, mostly fairly hard, by buying some iron nails. If you buy them from a variety of companies, you'll probably be able to demonstrate to yourself that they have differing retentivities. 86.183.85.88 (talk) 23:00, 10 February 2010 (UTC)
What specialized company which supplies transformer cores to ABB or GE would bother to sell a pound of their product to a hobbyist? Seems unlikely. A certain alloy number or name would be a more useful thing to look up online. Salvaging a core from a transformer or motor is another idea with better prospects. I have made a madly powerful electromagnet by sawing apart a motor stator. Edison (talk) 04:59, 11 February 2010 (UTC)
This does seem to be a typical example of something that everyone who learns about this stuff in the real world knows, but the Internet population doesn't seem to bother its head about. This paper from the late 50s gives an idea of the basics. Perhaps it is neither basic enough, nor new enough, to feature in pop science? 86.183.85.88 (talk) 23:35, 10 February 2010 (UTC)

## The Future

In your opinion(s), what/which areas of active scientific research will make the greatest impact on our technological development, say, by 2060? In my uninformed opinion I would think nanotech, but that's just me... —Preceding unsigned comment added by 173.179.59.66 (talk) 10:50, 10 February 2010 (UTC)

We don't do opinions, we do references. You can try going through this list of people that make a living out of giving opinions on the subject and see what they've been saying. I, however, would say that it is impossible to predict technological development 50 years in the future with any meaningful accuracy. I'd say the biggest technological development in the last 50 years is the personal computer (and, more recently, various other devices that can perform the same functions - eg. mobile phones) and I don't think many people predicted the importance of PCs in 1960 (the microchip had only just been invented and no-one had put it in a computer yet, and that was one of the major developments that made small-scale computers possible). --Tango (talk) 11:09, 10 February 2010 (UTC)
In fact, I think most people in 1960 would have predicted nuclear reactors as the most important development over the next 50 years, and it turned out they played a very minor role. --Tango (talk) 11:14, 10 February 2010 (UTC)
Yes, and extensive human space travel (e.g. moon colonies and the like). And jetpacks. AndrewWTaylor (talk) 12:01, 10 February 2010 (UTC)
Oh, yes, I forgot about space travel. I think nuclear energy was expected to have a bigger impact overall, though. --Tango (talk) 12:05, 10 February 2010 (UTC)
I agree nuclear power didn't live up to the predictions of energy too cheap to be worth metering, but it still delivers 15% of the world's electricity. If it ever becomes a practical reality, fusion power will have a huge impact. Room temperature superconductors would also have a huge impact, but are a more remote possibility. See our Timeline of the future in forecasts for some more ideas. Gandalf61 (talk) 12:06, 10 February 2010 (UTC)
I was about to say - fusion power would have huge consequences. Noodle snacks (talk) 12:13, 10 February 2010 (UTC)
Energy too cheap to meter was one part of predictions about the atomic age, the other was small-scale reactors in individual devices (nuclear powered cars, for example). The former happened to a small extent, but not really a significant one (nuclear energy is cleaner than fossil fuels, but not really cheaper), the latter didn't happen at all (we have nuclear submarines, which existed before 1960, but that's it). Fusion power would probably have a major impact, but there is no way to know if it will be invented in the next 50 years. --Tango (talk) 12:22, 10 February 2010 (UTC)
To be sure, scientists, politicians, and industrialists all spent a lot of time trying to distance themselves from the "too cheap to meter" fantasy (which frankly I doubt Strauss really thought would be about fission, anyway). The difficulty is that the popular imagination grabs onto such bountiful ideas and holds them tightly, no matter what cautions are put up by those more informed. Similarly the reactors in cars, etc., which even the more optimistic scientists (e.g. Edward Teller) recognized as having likely insurmountable technical difficulties, along with potentially just being bad ideas from the standpoint of safety. Even the more optimistic of the realistic possibilities—e.g., that widespread nuclear power would allow you to just convert your cars to being electric—was simply not as "interesting". --Mr.98 (talk) 16:09, 10 February 2010 (UTC)
Checking Google Book Search for "future" and "technology" in 1959-1961 publications, there is discussion of electrification in developing countries, nuclear fusion, space exploration, "atomic cars," the "energy cell" for portable electricity, hydrogen fuel produced by solar energy and used in fuel cells, satellite reconnaisance, "roller roads" loaded with cars on carriers, moving at 150 mph by 1970, negative ions introduced in the air in our living spaces. One Nobel Prize winning scientist, Nikolai Nikolaevich Semenov, (1896–1986) in 1959 predicted that in the future the electricity available per person worldwide would increase from 0.1 kilowatt to 10 kilowatts, allowing greater comfort and productivity, and that nuclear fusion would increase the power by another factor of ten, allowing climate control. He predicted that by 2000 synthetics would largely replace natural materials (fiber, animal products, wool, metal) not just in in clothing but in buildings and machines. Automation would shorten the workday to 3 or 4 hours (true enough now, if you average in the under/unemployed), irrigation and technology would allow ample food for everyone, understanding of "heredity" would revolutionize medicine. Edison (talk) 16:12, 10 February 2010 (UTC)
He deserves his Nobel prize - those are some good predictions. Not perfect, but good. --Tango (talk) 16:30, 10 February 2010 (UTC)
Among the difficulties with futurology is that 1. current trends often do not extrapolate (for various reasons), 2. new things come up that are unexpected, and 3. even when current trends do extrapolate, it's very hard to figure out what will really matter. Computers are a great example—in 1950, you could definitely have extrapolated that computers would become more and more prevalent. You might have figured out something akin to Moore's law (which came 15 years later, but that doesn't change too much), which, if true, would lead you to think that computer processors would be getting incredibly powerful in 50 years. On the other hand, you probably wouldn't have foreseen some of the other important developments in, say, LCD technology and battery technology which makes these things so beautiful, cheap, and portable. And even if you did expect computers to become a "big thing", anticipating how they would be used by individuals is still a massive jump. I've read wonderful articles from as late as the 1970s that predicted that home computing would be a big thing, but what would people use them for? The article authors (all avid home computer people) either imagined way too much (artificial intelligence, etc.) or way too little (people would use their computers almost exclusively for spreadsheets and word processing). Now multiply all the ways you can go wrong by the number of possible authors and commentators, and you have some people who will look prescient in 50 years, but most will look off to a fairly great degree. It's fairly impossible to know which of the commentators today are going to be the right ones, retrospectively, and focusing on those people who were "correct" by some interpretations is an exercise in cherry-picking. --Mr.98 (talk) 17:41, 10 February 2010 (UTC)
Always keen to point out my little quip about Wikipedia, I'd suggest that many futurists of the last century predicted that a machine would exist that would serve as a great encyclopedic compendium to democratically distribute information to the masses. H.G. Wells predicted it in 1937, Vannevar Bush predicted it in 1945, and Doug Engelbart demonstrated one in 1968. The exact incarnation of Wikipedia takes its present form as a distributed, internetworked set of digital-electronic-computers with a graphic terminal interface - but even in 1945 that idea was pretty well predicted (the significance of digital information was not yet understood until at least the 1960s). Yet, the concept of the usage-case and the societal impact that it would have is the really innovative and predictive leap. Whether the implementation is by photographic plate or by integrated transistor circuit is less important (in fact, how many users of the internet could tell you which technology actually makes their computer run? Therefore, it's irrelevant to them). So, when you look back at prior futurists' claims, you have to distinguish between predicted concepts and predicted implementations - implementations are for engineers to deal with, while concepts are the marks of revolutionary leaps of human progress. "Quietly and sanely this new encyclopaedia will, not so much overcome these archaic discords, as deprive them, steadily but imperceptibly, of their present reality. A common ideology based on this Permanent World Encyclopaedia is a possible means, to some it seems the only means, of dissolving human conflict into unity." ... "This is no remote dream, no fantasy. It is a plain statement of a contemporary state of affairs. It is on the level of practicable fact. It is a matter of such manifest importance and desirability for science, for the practical needs of mankind, for general education and the like, that it is difficult not to believe that in quite the near future, this Permanent World Encyclopaedia, so compact in its material form and so gigantic in its scope and possible influence, will not come into existence." Nimur (talk) 18:12, 10 February 2010 (UTC)
The question isn't whether people could have predicted things (I would personally say that the examples you are mentioning are, in many ways, fairly selectively chosen anyway—you're ignoring all the many, many ways that they have nothing to do with Wikipedia whatsoever in focusing on the few, narrow ways they have anything to do with it), because in a world with enough people speculating about the future, some of them are going to be right even if we assume the speculation is entirely random. The question is how you can possibly have any confidence in picking out the good predictions before you know how things worked out. It's easy to trace things backwards—it's pretty difficult to project them forward. And if you leave out the error rate (the number of things these same people predicted which did not come to pass), then their predictive ability becomes much less dodgy. --Mr.98 (talk) 18:30, 10 February 2010 (UTC)
Firstly, making a long list of all the possible things there might be in 25 to 50 years isn't "predicting the future" - that's a scattergun approach that's guaranteed to score a few hits - but if you don't know which predictions are the right ones and which ones will be laughable by then - then you haven't predicted a thing. But Nimur's example is a good one: 70 years ago, H.G.Wells said that it "'...is difficult not to believe that in quite the near future, this Permanent World Encyclopaedia, so compact in its material form and so gigantic in its scope and possible influence, will not come into existence" - I don't think 70 years is "quite the near future". That was one of those "more than 5 years means we don't know" kinds of prediction. Sure it came true eventually - but nowhere close to how soon he expected. Then we look at Bush's 1945 prediction - and again "The perfection of these pacific instruments should be the first objective of our scientists as they emerge from their war work." - 60 years later we have it...again, this was a vague prediction that was wildly off in timing. Engelbart did better - but even so, he was off by 30 to 40 years. If my "five years away" theory is correct then we should be able to find the first confident, accurate prediction: Wikipedia has been around for 9 years - but it's only really taken off and become more than a curiosity for maybe 6 years - and that means that the first accurate, timely prediction of Wikipedia ought to have been about 11 years ago - which is when Wales & Sanger started work on Nupedia. That fits. When something is utterly do-able, desirable and economically feasible, you can make a 5 year prediction and stand a good chance of being right on the money...but from 25 years away, all you can say is "This might happen sometime in the future - but I have no idea when." - which is what the previous predictors have evidently done. SteveBaker (talk) 03:55, 11 February 2010 (UTC)
So we can know pretty well that most of the stuff promised to us in Back to the Future 2 is not going to happen. Googlemeister (talk) 20:50, 11 February 2010 (UTC)
When scientists and technologists say "We'll be able to do this in 50 years" - they mean "This is theoretically possible - but I have no idea how". When they say "We'll be able to do this in 10 years" - they mean "This is technologically possible - but very difficult" and only when they say "We'll be able to do this in 5 years" should you have any expectation of actually seeing it happen. Five years is therefore the limit of our ability to predict the future of science and technology with any degree of precision at all. Flying cars and personal rocket packs are always 10 years away - and have been 10 years away since the 1950's. SteveBaker (talk) 20:10, 10 February 2010 (UTC)
Here is Steve's post summarized in table form. —Akrabbimtalk 20:17, 10 February 2010 (UTC)
I'd say we can make pretty reliable negative predictions 10 years in advance - if something isn't already in development, then it won't be widespread in 10 years time. The development process for new technology takes about 10 years, so what is widespread in 10 years time will be a subset of what is in development now - it is essentially impossible to know which items in development now will become widespread, though. (Note, I'm talking about completely new technology. Incremental changes happen much quicker - about 2 years development, often.) --Tango (talk) 20:21, 10 February 2010 (UTC)
I'll take 'greatest impact' to mean 'most impressive' and go with
1. transcontinental flights in two or three hours
2. quiet, environmentally friendly, autopiloted cars
3. highly immersive, interactive, tactile online gaming
Vranak (talk) 21:48, 10 February 2010 (UTC)
There are problems with all three of those - although they aren't technological ones:
1. We could build a 3 hour transcontinental airliner - but as Concorde conclusively proved, people are not prepared to spend the extra for a shorter intercontinental flight in sufficient numbers to be profitable...given the inevitability of exotic and expensive technology required to do it.
2. Quiet and environmentally friendly cars already exist - but their range is a little short and they aren't cheap. But I think it'll be a while until we get "autopiloted" because of the liability laws. If "you" are driving the car and something goes wrong and there is a crash, then "you" are responsible. If the car is driving itself, then the car company becomes liable - and that's not the business they want to be in. We're starting to see cars that help you drive - eg by warning you when you drift out of your lane or get too close to the car in front - and (like my car) by applying the brakes to the right wheels to help you avoid a skid...but although we have the technology to do much more than that - the car makers are being very careful to make these systems help out the driver and NOT be responsible in the end.
3. The problem with immersive (like virtual reality) systems is a chicken and egg situation. On PC platforms, the additional hardware has to appear before games companies can take advantage of it - and nobody will buy the hardware unless there are games for it - so things have to follow an evolutionary rather than revolutionary path. That leads to gradually better and better graphics cards - but it doesn't lead to a sudden jump to helmet-mounted displays, tactile feedback, position-measuring gloves, etc. The way this would have to happen is via the game console market - and as we've seen with the Wii's clever Wiimote and balance board, people like this and will buy it. But the problem with game consoles is the way they are sold. The business model is to sell the machine for much less than it costs and make the money back on the games. But if the hardware suddenly costs a lot more - there is no convenient way to get that money back without pushing games up to $100 to$150 (I can tell you don't like that idea!) - or coming out with a $1000 console that nobody will buy. The Wii managed to take the tiny step it did by using exceedingly cheap technology. The accelerometers and low-rez IR camera cost only a couple of bucks to make - so that was easy. Worse still, the public are heading rapidly the other way. People are buying$5 iPhone and Android games in massive numbers - and the PC and console market are drying up - except in these Wii-like areas where they widened the demographic. Developers like this trend because employing several hundred people for three years to produce a $60-a-pop game is an incredibly risky business. Only 35% of them ever turn a profit and that's a major problem for the people with the capital to fund them. On the other hand, if you have 100 three-man teams each writing an iPhone app, the law of averages means that you get a very accurate idea of the return on your investment...the risks are vastly lower. The idea of pushing consumers and developers into$1000 consoles and $150 games is really not very likely in the near future. Microsoft, Sony & Nintendo know this - which is why there is no Xbox-720, PS-4 or Nintento-Poop (or whatever stoopid name they'd call it) expected either this Xmas or the next. So sorry - while the technology certainly exists for all three of the things on your "wish list" - I'd be really very surprised to see any of them them happen within 10 years. SteveBaker (talk) 23:30, 10 February 2010 (UTC) Both Microsoft and Sony are of course following Nintendo with PlayStation Motion Controller and Project Natal Nil Einne (talk) 09:29, 11 February 2010 (UTC) We already had #1 forty years ago.. see Concorde. We don't do it any more for a variety of economic and political reasons. --Mr.98 (talk) 23:28, 10 February 2010 (UTC) Concorde actually took three and a half hours to get across the atlantic - not "two to three" - but because everyone flew first-class and they had specially expedited boarding, luggage reclaim and customs, you'd probably save an hour at the airport compared to a commercial flight! If the Concorde-B had ever been built (which had 25% more powerful engines), I think they would have broken the 3 hour mark. SteveBaker (talk) 23:41, 10 February 2010 (UTC) First of all, let's refer back to the original question. 2060. Not 2020. Second, I was thinking about those spaceship-plane hybrids that go into the near reaches of outer space. Nothing to do with conventional aeronautics. Something that'll take you from Paris to Sydney in a couple hours. Vranak (talk) 00:41, 11 February 2010 (UTC) I thought you meant sub-orbital hops. There may be something in that. While London to New York in 2 or 3 hours isn't sufficiently better than the 5 or 6 hours you can do it in a conventional plane to warrant the extra cost, London (or Paris if you prefer) to Sydney in 2 or 3 hours would be sufficiently shorter than then current 20 hours (or whatever it is) that people would pay quite a lot for it. --Tango (talk) 01:03, 11 February 2010 (UTC) You mean like Scramjet#Applications [3]? I remember a book from the late 80s IIRCsuggesting something like that. I can't remember if they had a time frame but it didn't sound particularly realistic at the time and I'll freely admit I'm still far from convinced we'll see it in even in 2060. We'll see in 50 years whether I'll be eating my words I guess. Nil Einne (talk) 09:08, 11 February 2010 (UTC) I expected that higher definition television would come along in my lifetime to replace the 1941 black and white system and the 1950's color add on (NTSC=never twice same color), but I am stunned to read that 3D TV will be in stores with at least a couple of broadcast channels plus DVDs in less than a year. I never really expected that to be a consumer item in my lifetime. (Maybe I'll hold out for "Smellovision" with olfactory output.) If car GPS units had an order of magnitude more spatial resolution, or if lane markers were embedded in the pavement, it should be possible with straightforward extension of existing technology, demonstrated in the DARPA Challenge, to tell your car of the foreseeable future to drive you to a certain address, or to drive you home, as surely as if you had a chauffeur. I am amazed by the IPOD, considering the reel-to-reel tapes or LPs of a few years ago. The coming practical LED light bulb is amazing (as yet a bit dim/expensive). So for scientific advances affecting our technology and lives by 2060, medical science should benefit from study of genetics, with ability to predict who is likely to get a disease, and what medicines are best for that individual, and with genetic solutions to cancer, diabetes and other diseases with a hereditary component, perhaps at the cost of engineering out "undesirable" traits such as Aspergers, leaving a shortage of techies and scholars. Militaries and sports empires might genetically engineer super soldiers and super athletes, just a super brains might be engineered. The ability to speak articulately might be given to some animals like chimps and dolphins who are somewhat intelligent, or even to domestic pets (the cat , instead of "Meow" says "Pet me. Don't stop. Now feed me." The dog, instead of "Woof! Woof! Woof! says "Hey!" "Hey" "Hey!"). Breakthroughs in batteries or other energy storage technologies could make fossil fueled cars a relic of the past, just as matches made tinder-boxes obsolete. Nuclear proliferation, or new technologies for destruction, could render the metropolis obsolete, as too handy a target. Terrorists with genetically engineered bioweapons could try to exterminate their perceived enemies who have some different genetic markers, ending up with a much smaller global population. Crime solving of 2060 would be aided by many more cameras and sensors which track our movements and activities, and more genetic analysis will be done on trace evidence, based on a larger database of DNA. Zoos might include recreated mammoths and dinosaurs, by genetically manipulating their relatives, the elephant and the bird. Astronomy will certainly have vastly improved resolution for detecting smaller planets, including Earth-like ones. More powerful and efficient generators of electricity could make unmanned interstellar probes possible. Mind reading or interrogation will be facilitated by cortical evoked potentials,and MRI. There will be more robotic airplanes, foot soldiers and submersibles in future wars. Cyber warfare will be an important part of major conflict. Computer intelligence could far outstrip that of humans. Improved robotics could create robots who were for a few years the best of servants and thereafter the worst of masters for the remnant of humans. All themes that have been explored by futurists and sci fi writers. Edison (talk) 04:22, 11 February 2010 (UTC) 3D TV (in the sense that it's about to be dumped onto the airwaves) is really no big deal - the technology to do it has been around since the invention of liquid crystal displays and infra-red TV remotes. You have a pair of glasses with horizontal polarization...and behind that a set of liquid crystals that polarize vertically when they are turned on - and horizontally when they are off. By applying voltage to the two lenses alternately, you block the view from one eye and then the other. The glasses have a sensor build into the frame that detects infrared pulses coming from the TV. The TV says "Left eye...now Right eye...now Left eye" in sync with the video that displays left-eye then right eye images. That's about a$5 addition to an absolutely standard TV...I've had a pair of those 3D "LCD shutter" glasses for at least 15 years - they were $30 or so back then - but with mass production, they could have sold them for$10. These days, they probably cost a couple of bucks a pair. We could easily have made this exact system for a very reasonable price back in the 1970's...it simply required the will on the part of the movie and TV companies to make it happen - and a sense that the public are prepared to pay the price to see it. Of course these 3D TV's are gonna cost a packet to start with - but within a couple of years, all TV's will have it. SteveBaker (talk) 03:18, 12 February 2010 (UTC)
SB already mentioned the perpetually coming flying cars. There's also of course the Arcology which some may believe we're now moving away from with the proliferation of the internet and other factors like that Edison mentions which make metropolises lass desirable. In a similar line, it's usually funny how many of these predicitions of the future fail to predict social changes.
Perhaps few here would have heard of it but Anno Domini 2000 – A Woman's Destiny receives some attention particularly for its predictions of female involvement in politics and other aspects of life and some of the other predicitions also have a ring of truth [4] yet if you read it (it's in the public domain so is available online if you wish to, e.g. [5]], much of it comes across as at best 'quaint' particularly when it comes to the importance of the British Empire and the monarch in the imperial federation and in the US rejoining the Imperial federation.
Similarly many of those predictions of the future in the 40s, 50s and 60s like this [6], [7], [8], [9] & [10] include numerous predicitions of how the housewife of the future will manage the home. (Incidentally, those examples may be interesting to read in general to see how right and how wrong they are.)
This may not seem particularly relevant to the question, but I would say it is, since prediciting the future does require some knowledge of social & politicial changes that have taken place (a related example, I've heard the story before that 30 or so years ago few were prediciting the current demands for lean meat which makes things difficult since selective breeding takes a long time).
BTW, in case people didn't notice, there are two links [11] [12] which may be of interest for those looking at predicitions of the past.
Nil Einne (talk) 09:08, 11 February 2010 (UTC)

Artificial intelligence and Raymond Kurzweil's technological singularity. Intelligent organic life, if it survives long enough, probably inevitably becomes an organic-cybernetic hybrid -- a cyborg. When the same thing happens to the human race, perhaps intelligent life from elsewhere in the universe (very long-lived and ancient, because cybernetic) will communicate with it. The first step in that direction will be artificial intelligence and organic-cybernetic hybrids (cyborgs), both of which could evolve exponentially in the next century.

## how many moons dwarf planets have total if we found all of them

How many moons will Pluto Eris Makemake and Haumea have most if we found all of them. They won't have more than 5. Pluto formerly only Charon in 2005 2 more Eris have two moons. To Makemake have any moons virtually. Could Haumea have 3 moons. Jupiter technically could have over 100 moons just many moons hidden moons.--209.129.85.4 (talk) 21:00, 10 February 2010 (UTC)

We cannot possibly answer how many moons will be found around dwarf planets; indeed, we cannot answer if or when all such moons will be or are found. At present, the five dwarf planets have six known moons. — Lomn 21:18, 10 February 2010 (UTC)
Why won't they have more than 5 moons? --Tango (talk) 21:20, 10 February 2010 (UTC)
Why not? Duh! Because they are small and they have low gravity--209.129.85.4 (talk) 21:35, 10 February 2010 (UTC)
Very little gravity is required to have very small moons (particularly on the extremely distant DPs that don't/won't interact with Neptune). There is no theoretical upper limit. — Lomn 21:46, 10 February 2010 (UTC)
But why should the limit be 5? Why not 4 or 6? --Tango (talk) 23:12, 10 February 2010 (UTC)
Why would Pluto be a dwarf planet but not Charon? I thought they were a binary dwarf planet pair? Googlemeister (talk) 21:21, 10 February 2010 (UTC)
Per our Pluto article, the IAU has not yet formalized a definition for binary dwarf planets. If you prefer to ignore the IAU, then by all means consider Charon a dwarf planet in its own right (I find that a reasonable position). — Lomn 21:46, 10 February 2010 (UTC)
Charon doesn't count as a dwarf planet under the IAU rules because the point around which Pluto and Charon orbit is (just) below the surface of Pluto - so by a rather small margin, Charon is (like our Moon) still a "moon" no matter how big it is. SteveBaker (talk) 23:10, 10 February 2010 (UTC)
Our article, Charon#Moon or dwarf planet?, seems to disagree with you. --Tango (talk) 23:52, 10 February 2010 (UTC)
Yeah - you're right. My mistake. So why is there any debate? Charon is larger than many other bodies described as "dwarf planet" under the new rules. I can't think of any reason not to describe Pluto/Charon as a binary dwarf-planet. SteveBaker (talk) 03:11, 11 February 2010 (UTC)
I don't think there is debate, that's the problem. There needs to be some debate and settle on an official definition of a double planet. The "barycentre outside both bodies" definition is unofficial in the same way the (very vague) definition of "planet" was unofficial before 2006. There are other possible definitions to be considered, although I doubt any of them would chosen - mostly things to do with the smaller body's interactions with the Sun being more important than its interactions with the larger body. Those definitions sometimes make the Earth-Moon system a double planet. That's probably the biggest reason they won't be chosen - people can get used to Pluto no longer being a planet, but the Moon no longer being a moon? That would be hard! --Tango (talk) 12:09, 11 February 2010 (UTC)
There isn't a formal definition for the words "Moon" and "Moonlet" - so in theory, you could claim that every single one of the trillions of little chunks of ice orbiting Saturn was a moon. In the absence of a decent definition, if we found even the most tenuous ring system around any of those dwarf planets, then the number of teensy little "moons" would be hard to pin down. Right now, there are 336 named objects that are labelled "moons" - but with over 150 more ill-classified bits and pieces awaiting accurate orbital calculations flying around Saturn alone - it's a silly game. Until we have a formal definition, it would be tough to answer this question even if we had perfect knowledge of what is orbiting these exceedingly dim and distant dwarf planets. With the best telescopes we have, the dwarf planets themselves are just a couple of pixels across - finding moons that are maybe 1/1000th of that size would be very hard indeed without sending a probe out there - and doing that is a 10 to 20 year mission. SteveBaker (talk) 22:47, 10 February 2010 (UTC)
Which we launched 4 years ago: New Horizons Rmhermen (talk) 23:42, 10 February 2010 (UTC)
But since most of those dwarf planets (Eris, Sedna, MakeMake, etc) were only discovered a matter of months before the launch, I don't think New Horizons will be able to visit them. Our New Horizons article explains that a flyby of Eris has already been ruled out. It's basically a Pluto/Charon/Kyper-belt mission. Since it's not going to reach even Pluto until 2015, and those other dwarf planets are WAY further out there - we may discover other dwarf planets for it to visit in the meantime. SteveBaker (talk) 13:47, 11 February 2010 (UTC)
If New Norizons originally plan to go to other planet dwarfs (Makemake, Eris) by cancelling visits is probably once again budget problems.--209.129.85.4 (talk) 20:48, 11 February 2010 (UTC)
I think it was technical problems, actually. It wasn't feasible to give the probe enough fuel for such a large course change. --Tango (talk) 20:53, 11 February 2010 (UTC)
How exactly could they 'originally plan to go to other planet dwarfs' if (according to SB) they were only discovered a few months before the launch? Nil Einne (talk) 18:28, 13 February 2010 (UTC)
There is an active search for other dwarf planets within the cone New Horizons can reach after visiting Pluto. Hopefully someone will find one in time. --Tango (talk) 16:31, 11 February 2010 (UTC)

## earth-moon double planet

How long will it be until the barycenter of the earth-moon system is locate outside the surface of the earth, which would, under current definitions, promote the moon from a moon to the second body of a binary planet? (Imagine the wikipedia article "moon (dwarf planet)" Googlemeister (talk) 21:28, 10 February 2010 (UTC)

Per our orbit of the Moon article, assuming a steady solar system, the Moon would eventually stabilize at an orbit with a semi-major axis of some 550,000 km. The barycenter of the Earth-Moon system would move into free space at a semi-major axis of about 525,000 km. Since it would take ~50 billion years to reach the maximum, I'd guess it would take ~40 billion years to reach the double planet portion. Of course, the "steady solar system" thing won't hold for 40 billion years. As the article notes, in two or three billion years, the Sun will heat the Earth enough that tidal friction and acceleration will be effectively eliminated. As such, it's not clear that the Earth-Moon system ever will have a free-space barycenter, even though it's theoretically possible. — Lomn 22:03, 10 February 2010 (UTC)
Per our orbit of the Moon article, you could argue the Moon is already half of a double planet, since the Moon's orbit around the Sun is everywhere concave. --Michael C. Price talk 12:08, 14 February 2010 (UTC)

## teleportation

Is there any actual research in the field of teleportation? I mean obviously Star Trek style teleportation is pretty unlikely (especially living things), but has there have been experimentation involving transporting inert material between say two wired locations? Googlemeister (talk) 21:35, 10 February 2010 (UTC)

There's plenty of actual research in quantum teleportation, but that's not really "teleportation". I don't believe there's been any meaningful work in turning atoms into bits back into atoms. — Lomn 21:51, 10 February 2010 (UTC)
Ob.XKCD is at: http://xkcd.com/465/ SteveBaker (talk) 22:34, 10 February 2010 (UTC)
Current research (that I know of) is in teleporting energy, not matter. This is performed by taking advantage of entanglement to put energy into a particle in one place and get energy out of a particle in another place (which is such a generalized statement that it isn't completely true - but easily understood). Because energy/mass is very similar in physics, it may be possible in the future to go from matter to energy to teleportation to energy to mass again. So far, once you convert matter to energy (think atomic bomb), it isn't very easy to get the matter back again. -- kainaw 22:39, 10 February 2010 (UTC)
Instantaneous, literal teleportation is a problem that physics may not ever overcome except for the most trivial examples of moving single particles or packets of energy. Conservation laws of all kinds would have to be mollified before we could possibly do this for 'macro-scale' objects.
But the other approach is to scan and measure the object at one location - destroy it utterly - then transmit the description of the object and recreate it at the other end. StarTrek teleportation is sometimes like that (depending on the whim of the authors of a particular episode - it's not very consistent) because teleporter errors have on at least two occasions resulted in winding up with two people instead of one...however, the difficulty is that there is typically only one machine at one end of the link and to do the scan/destroy/transmit/receive/recreate trick, you need two machines, one to scan/destroy/transmit and another to receive/recreate. However, with two machines, this starts to look almost do-able. If you take a fax machine and bolt it's output to a shredder - you have a teleporter (of sorts) for documents with present-day technology. Interestingly, if the shredder should happen to jam, you end up with one Will Ryker left behind on the planet and and another one on the Enterprise. Doing that with things as complicated and delicate as people is a lot harder. You have to scan at MUCH higher resolution, and in 3D - and the data rates would be horrifically large - and we have absolutely no clue how to do the "recreate" step (although I'd imagine some nanotechnological universal replicators would be involved). There is also the ethical issue of the 'destroy' step and the extreme unlikelyhood of anyone having the nerve to step into one!
The thing I do think may one day be possible is the idea that we scan people's brains into computers when their physical bodies are about to conk out - and allow them to continue to live as computer programs that simulate their former biological brains so precisely that the persons can't tell the difference. If you could do that then future robotic-based humans could teleport at the speed of light to remote locations fairly easily by sending their software over a digital communications link and reinstalling it on a remote computer/robot. This would be an amazing thing and would allow you to walk into a teleportation booth in NewYork, dial a number and pop up in Australia a few seconds later, being completely unaware of the (brief) journey time. Because you're unaware of the journey time, distance would be little obstacle - providing there is a suitable robot/computer waiting for you at the other end.
SteveBaker (talk) 23:06, 10 February 2010 (UTC)
"Star Trek style teleportation is pretty unlikely (especially living things)" While such teleportation is pretty unlikely, I don't see how teleporting a living thing would be any more difficult than teleporting a finely detailed non-living thing, such as a microprocessor. 58.147.58.179 (talk) 04:06, 11 February 2010 (UTC)
A microprocessor doesn't move. A living being does. So, if you scan a microprocessor from top to bottom, you can get the whole thing scanned in atom by atom. Yes, the electrons are whizzing around, but the atoms are rather stable. If you scan a living being from top to bottom, the atoms are not remotely stationary. They are moving here and there, all over. You will scan some atoms multiple times and some not at all. The scan will be like a photo that is blurred when a person moves during the photo. So, you have, on top of teleportation, the concept of a shutter speed for the scan. -- kainaw 04:24, 11 February 2010 (UTC)
Also, for most objects (a teacup, for example) you could "summarize" the object rather simply by saying "the shape of the object such-and-such and it is made entirely of a uniform ceramic of such-and-such average composition with a surface coloration made of such-and-such chemicals laid out such as to produce an image like this" - and what the 'reconstruct' stage could conceivably do would be to reproduce a perfectly good, identical-looking, fully functional teacup at the other end - although it might differ in irrelevent, microscopic ways. But with a living thing, teeny-tiny errors at the atomic level in something like a DNA strand or tiny structural details about where every single synapse in the brain connects to are utterly crucial - and no reasonable simplification or summarization is possible. When you photocopy or fax a document, the copy isn't 100% identical down to the individual fibres of the paper - but that doesn't matter for all of the usual practical purposes. However, if that detail DID matter, then faxing and photocopying documents would be impossible. When you copy a human, they are really going to want every neural connection and every base-pair on their DNA perfectly reproduced and not being regenerated from a "bulk description" such as we could use for a teacup. SteveBaker (talk) 13:38, 11 February 2010 (UTC)
I always assumed this is why Captain Picard always complained about the quality of replicator food (and tea). The engineers that designed the thing were probably too aggressive with their compression algorithms. APL (talk) 15:22, 11 February 2010 (UTC)
I thought he complained about the food because he was French. Googlemeister (talk) 17:39, 11 February 2010 (UTC)
There's also the problem of replicating electrical charges, and probably other sort of dynamic aspects of the body like pressures, which would be necessary in order for the 3D printer to print out a living being instead of a dead one. A computer would be easier to teleport because you could replicate it switched off and then switch it on again later. 81.131.39.120 (talk) 21:44, 11 February 2010 (UTC)

The answer to "blurring" would be to freeze them-though that's another questionable technology.Trevor Loughlin (talk) 09:24, 11 February 2010 (UTC)

Indeed - cryogenics is more likely to be possible than teleportation, but it is still very difficult. --Tango (talk) 12:11, 11 February 2010 (UTC)
The amount of energy required to create matter at the destination end is stupendously huge. 67.243.7.245 (talk) 15:35, 11 February 2010 (UTC)
You could conceivably have giant tanks of raw material.
Alternatively, if you have an easy way to convert between energy and matter, you could feed random junk into the machine, or save the energy from the last out-going transport. APL (talk) 16:52, 11 February 2010 (UTC)

## Diethyl ether

how did they use Diethyl ether for surgery if it forms peroxides . any peroxides over 3% are extremely caustic and would burn the patients skin —Preceding unsigned comment added by 67.246.254.35 (talk) 21:50, 10 February 2010 (UTC)

"Don't use it if it's got a high peroxide content."? It's easy to detect them and it's easy to remove them from the liquid. How is/was ether administered?--does that method result in transfer of substantial amounts to the skin? DMacks (talk) 00:07, 11 February 2010 (UTC)

yes , they put it on a cloth and put it over their mouth and nose —Preceding unsigned comment added by 67.246.254.35 (talk) 00:18, 11 February 2010 (UTC)

(edit conflict) I recall it depicted (TV/Movies) as being dripped manually onto a pad or mask over the nose/mouth. See also Diethyl ether, Diethyl ether (data page) and Diethyl ether peroxide220.101.28.25 (talk) 00:24, 11 February 2010 (UTC)
In particular seeDiethyl ether#Safety re peroxide formation. No information that I can see however about how it was applied, though pads as mentioned seems likely. --220.101.28.25 (talk) 00:33, 11 February 2010 (UTC)

yes i read those articles they did not answer my question--67.246.254.35 (talk) 00:31, 11 February 2010 (UTC)

When it comes to medical chemicals, any impurity might be cause for concern, and 3% of another non-inert contaminant is very high--I would be concerned well before that level is reached. For example, physiological effects (blood pressure) apparently become noticeable already at 0.5% ether peroxide concentration.("Pure Ether and Impurities: A Review". Anesthesiology. 7 (6): 599–605. November 1946.) DMacks (talk) 01:00, 11 February 2010 (UTC)

so how do you tell if there are peroxides in the ether? —Preceding unsigned comment added by 67.246.254.35 (talk) 05:51, 11 February 2010 (UTC)

Answering an above question: the article states that diethyl ether is sold containing a trace amount of BHT, which will mop up any oxygen before it can form an ether peroxide. I expect that by storing the ether in well-sealed, dark bottles it would be possible to make the amount of peroxides formed over the lifetime of the bottle (as an anaesthetic) negligible. Also, 67, please do not blank your talk page if I have written on it. Brammers (talk) 08:08, 11 February 2010 (UTC)
The diethyl ether peroxide page that you (67) had read includes a whole section about testing for its presence. DMacks (talk) 15:56, 11 February 2010 (UTC)

## Chemistry question in regards to chemical bonds

What chemical bond is most vulnerable to an acid attack and why? I think it may be ionic but I am unsure. —Preceding unsigned comment added by 131.123.80.212 (talk) 23:12, 10 February 2010 (UTC)

What are your choices? Is this a homework problem? DMacks (talk) 00:46, 11 February 2010 (UTC)
I was just given that question. It is a lab question for my Petrology class (undergraduate geology class). I have scoured all possible resources to find the answer (i.e. Google, Ebscohost, Google Scholar, etc.) but with no such luck. —Preceding unsigned comment added by 131.123.80.212 (talk) 01:15, 11 February 2010 (UTC)
Acids don't really attack chemical bonds, per se. See Lewis acid-base theory for an explanation; but in general acids produce H+ ions in solution, and bases (which is the stuff that acids react with) all generally tend to have unbonded pairs of electrons in them, (see lone pair). So the acid doesn't attack the bond, it attacks electrons that aren't currently involved in bonds. Now, once the acid forms a new bond with that lone pair, other bonds in the molecule may break at the same time, but one would have to see a specific reaction to know exactly what would happen. The best I can say is that the question, as the OP has worded it, is so vague as to make it very difficult to answer. --Jayron32 02:58, 11 February 2010 (UTC)

The most basic thing in solution. H+ usually goes after lone pairs, as they are the highest energy electrons present generally (they tend to form HOMOs). That's because unshared electrons tend to be in a higher energy well. There are cases where some chemical bonds are higher in energy than a lone pair, but you really have to work hard to get rid of most other bases first. In fact for example I think sulfuric acid attacks alkenes directly -- you don't want too much water because H2O may in fact be more basic than say, cyclohexene. John Riemann Soong (talk) 03:25, 11 February 2010 (UTC)

This question is addressing weathering as in soils, when highly acidic conditions increase the solubility of certain minerals (because of the dissociation of water to H+ and OH-). I was trying to decide between ionic/metallic/covalent bonding of certain minerals in soil, which would be most vulnerable to what this professor calls an "acid attack". Any more help would be greatly appreciated!

—Preceding unsigned comment added by 131.123.80.212 (talk) 23:48, 10 February 2010 (UTC)

(ec with post above) (Responding to John Riemann) Right. One answer that would be correct would be "double and triple (covalent) bonds". See, for example, Electrophilic addition. A pi bond is generally weaker than a sigma bond, so easier for an electrophile (aka lewis acid) to go after.
(Responding to 131's post above) Reading your post above, though, I don't think that's what you're looking for. You're basically asking why certain minerals dissolve better in acidic conditions. Many of the things in the earth are oxides, especially basic oxides (which is a pitiful article, really). I'm not really sure of the chemistry of these things, but often times, an acid will convert a basic oxide into a hydroxide, which tend to be more soluble in water. Carbonates are especially suseptable to acid (they decompose to carbon dioxide and water). That's why acid rain can do so much damage to marble (that's calcium carbonate) statues and buildings. Buddy431 (talk) 05:06, 11 February 2010 (UTC)