Wikipedia:Reference desk/Archives/Science/2010 July 11

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July 11

Ground connection

Why do some electrical devices have plugs with three "sticks" (don't know their names) instead of two? I heard that the third one is a connection to the ground. If so, 1) why include this, and 2) how would the current go to the ground? Thanks. 74.15.137.192 (talk) 00:53, 11 July 2010 (UTC)

The Ground pin or prong, also known as the Earth, is indeed a connection to the ground/Earth. 1) Appliances designed for such systems have internal connections between their external cases or other touchable components (if conducting) and the Earth pin on their power plug so that if a fault develops in the appliance making such parts live, there will be a lowest-resistance path for the electrical current to pass harmlessly to Earth rather than taking the only somewhat higher-resistance path via the appliance's user, electrocuting them in the process. 2) Power supply circuits using this system include connections between the Earth socket (which takes the Earth pin) and the ground, often but not necessarily utilising existing good Earth connections such as metal water-supply pipes that pass through the ground.

Not all appliances used with 3-pin plugs necessarily have an Earth connection: table lamps, for example, often use cables or flexes with only two internal wires, one for the Live and one for the Neutral; in this case the Earth pin has no electrical function, but on most modern 3-pin sockets, it is still necessary for pushing aside the internal shrouds that otherwise block off the other two socket holes to prevent such things as small children poking sharp objects into them, and to discourage irresponsible adults attempting to insert flex wires without using a plug. 87.81.230.195 (talk) 01:32, 11 July 2010 (UTC)

I'm guessing '87 is from the UK. Here in the US, there aren't shrouds in the socket to be pushed aside by the third pin. There are far too many two-pin devices still being made to allow that possibility. Fortunately, 110v is a lot less dangerous than 240v. But you're right otherwise. Devices with plastic cases can't really become dangerous even if an internal wire breaks loose - so two pins is enough. Devices with metal cases or exposed metal parts can potentially become live in the event of some kind of internal fault - and internally connecting all of the metal parts to the earth wire provides both an efficient way to route the current away - and a way to rapidly trip an earth leakage circuit breaker to make everything safe. SteveBaker (talk) 04:04, 11 July 2010 (UTC)

Indeed: I'm afraid I subconsciously subsumed North American systems under the subset "not modern" :-) . 87.81.230.195 (talk) 22:48, 12 July 2010 (UTC)

The goal of the earth-wire is not to reroute the current from the user but to make sure that ther are a path for the current that has low enough resistance to blow the fuse. The resistance in the earth-wire are often large enough that the the voltage-drop makes the remaining potential of the casing still lethal but since the current is so high the fuse will interrupt the current fast.

If we assume zero source impedance and earthing impedance and the same thickness of the live wire and the earth wire then the case would get half the live potential, 115 V for a 230 V 1 phase system, this is still lethal but the fuse will interrupt it in less than 200 ms in most cases.--Gr8xoz (talk) 10:09, 15 July 2010 (UTC)

But what prevents the current from always flowing to the earth? 74.15.137.192 (talk) 09:39, 11 July 2010 (UTC)

Most of the components are isolated from contact with the ground to prevent this from happening. They are either physically kept away, or are insulated by wrapping them in plastic or some other nonconductive material. This is why (among other reasons) wires are usually coated in plastic. Staecker (talk) 10:21, 11 July 2010 (UTC)

Yes: to clarify a little further, the Earth pin is connected (via a third wire inside the cable) only to parts of the appliance that should not be live, but may become live if a fault inside the appliance occurs. 87.81.230.195 (talk) 16:42, 11 July 2010 (UTC)

Indeed, if you pull apart a device with a 3 pin plug and carefully trace the earth wire, you'll find that it doesn't connect to anything at all besides the metal parts of the case of the machine. When the gizmo is functioning normally, the earth wire simply isn't connected and no electricity flows along it. Where it comes into play is if someone yanks hard on the power cord or drops the device or something - at that point, either the live or neutral wire could come loose and touch one of the metal parts of the case. If you're holding it at the time, you're going to get a powerful - and possibly lethal - electric shock. This is so dangerous that we have that earth wire there as a "just in case" measure. So if the live wire should come loose, the current won't flow through your body because the earth wire is a "shorter" path (less resistance) to ground than your flesh. But when the machine is working perfectly - the earth wire doesn't do anything at all! You could disconnect it and the machine would continue to work perfectly well (but please don't because that's dangerous!)...of course none of this is an absolute guarantee - it could be that you dropped an electrical device and that it broke such that the earth wire became disconnected AND the live wire ended up touching the case. But it is generally assumed that such 'double fault' conditions are sufficiently rare as to be of little concern. Personally, if I drop an electrical device, I'll first unplug it at the wall before picking it up and checking it for obvious damage. SteveBaker (talk) 16:51, 11 July 2010 (UTC)

Okay that makes a lot of sense, thanks for the explanation. 74.15.137.192 (talk) 22:49, 11 July 2010 (UTC)

Relevant to this discussion is Appliance classes. Appliances with an earth plug are called Class 1, appliances without an earth plug are called class 2 or "double insulated" which means they are designed in such a way that no internal fault can cause the chassis to become live, typically this means a housing entirely made of plastic. Vespine (talk) 00:52, 12 July 2010 (UTC)

Quantum mechanics, psychology, and free will

Up until now, I thought that neuroscientists were generally in favor of hard determinism (I know philosophy falls outside their field) because of Libet's experiment on conscious decision-making, but I came across this: Excitatory postsynaptic potential#Miniature EPSPs

See what it says about the quantal nature of synaptic activity.

Wouldn't that hold relevance to the article on Free Will? I don't see anything there mentioned about it. That is, couldn't miniature EPSPs provide a basis for free-will?

And one more thing: Are there any other interesting experiments or research which involve quantum mechanics and psychology? Aside from EPSPs, apparently IPSPs are probabilistic also? So, are there miniature IPSPs too? ☯  Zenwhat (talk) 05:01, 11 July 2010 (UTC)

(1) Speaking as a neuroscientist, I can tell you that neuroscientists are generally materialists, but don't care very much whether the world is deterministic at the subatomic level. Only a small fraction of neuroscientists know about the Libet experiments in any detail, and of the ones that do, attitudes are mixed.

(2) The "quanta" that are involved in synaptic release have absolutely nothing to do with quantum mechanics. They are subcellular structures that are large enough to be visible in an electron microscope -- they are called quanta because they come in discrete packets, called synaptic vesicles. They are orders of magnitude too large for quantum mechanical phenomena to come into play.

(3) I don't believe there have been any experiments that involve quantum mechanics and neuroscience or psychology. A few people in the "physics of consciousness" camp have suggested ideas for experiments, but I'm not aware of any having been conducted. You might look at our article on quantum mind for further pointers. (I think it's ridiculous myself.) Looie496 (talk) 06:12, 11 July 2010 (UTC)

I'll add (from a different perspective) that random phenomena is a bad direction in which to start searching for free will. free will is not random (in fact, there is no decent analytical definition of what free will means, and so there is no possibility of testing for or measuring it). when a scientist uses a random model to study human/cognitive behavior it's not because he necessarily thinks there is or isn't anything random about human/cognitive behavior, it's only because human/cognitive behavior is too subtle and complex to be handled accurately using a deterministic model under current empirical limitations. --Ludwigs2 07:10, 11 July 2010 (UTC)

Modern mainstream physics does not describe a "free will" in any shape or form. A system may exhibit a pronounced quantum-mechanical behavior if it is small enough. This usually has no effect on a large scale (indeed, you do not need to know the rotational and vibrational state of every molecule to estimate the thermodynamic properties of the air in the room; knowing pressure and temperature is enough to get a very accurate prediction). On a large (macroscopic) scale a system may exhibit a "deterministically chaotic" behavior, which simply means that to predict the system behavior on a long enough time scale the initial conditions must be known with impossible accuracy (imagine a nitrogen molecule released in a vessel of oxygen gas; no amount of accuracy will help you predict the nitrogen molecule location a minute later). Alternatively, a large system may have a "deterministic" behavior proper (for example, a deep enough attractor state for the probability of escape to be negligible over the longest relevant time scale; put your lab notebook in the desk drawer in the evening and you will find it there the next morning). Finally, a macroscopic system may (by chance or by feat of engineering) reflect in its macroscopic state a state of a much smaller, quantum-mechanical system it is brought into interaction with. When this happens deliberately it is called "a measurement"; when this happens by chance it may be referred to as "a butterfly effect". Note that nothing I described above has anything even remotely to do with a free will. Neuroscience, on the other hand, has something to say about the free will. It has been shown repeatedly that the brain prepares for an action (or for a particular decision) before the decision is consciously taken or the action is is consciously initiated. Some human data are summarized in the Neuroscience of free will article, with due caveats. There are also some monkey electrophysiology + behavior data reported by several groups on a few different tasks, all pointing to the same thing. However, again, this does not imply that there is no free will; rather, this implies that the brain is indeed involved in the early stages of decision-making :) . Indeed, when we decide to turn our head to attend to a particular stimulus, the brain must have already compared its relative importance to the other stimuli for us. And when we speak with other people, we do not consciously prepare every word we say, yet we say what we want and do not spew random nonsense. The unconscious decision precedes the conscious one, but it is still our decision and not Erwin Schrödinger's. It is still a free will, or at least it feels like a free will, so at least some people assume it is; and our entire moral system (and the entire criminal justice system, too) are based on this assumption. On the other hand, as Ludwigs2 said above, any sufficiently complicated but ultimately chaotic system is indistinguishable from a system with a free will; at least not at the Turing test level. Yet no-one seriously blames a computer's free will for coming down with a Blue Screen of Death or mucking up its own file-system at the worst possible moment. A very compelling scientific evidence against the existence of the human free will would necessarily lead to abolition of the notion of crime or responsibility for one's actions; and the human civilization will need to adjust accordingly (as it has adjusted to the fact that the Earth is round, or that the sky does not separate the waters above from the waters below). I personally do not see this forthcoming anytime soon. --Dr Dima (talk) 08:30, 11 July 2010 (UTC)

I would just like to point out, as a philosophical thing, that there is no recourse in the probabilistic for free will. Showing something is not classically deterministic does not give the individual agent any freedom. Doing what you do because of a cosmic dice rolling is not free will in any sense. It is still deterministic, just with the dice as the determiner. Free will is a complicated and quite fuzzy concept, one rooted more in moral questions than physical ones, and looking for a physical analogy for it has been, so far as I have been able to see, quite fruitless. The world is, as far as anyone can tell, ultimately mechanistic, even if some of that mechanism is, at a very low level, inherently probabilistic. (I would contrast this with things that are "apparently probabilistic," like shuffling a deck of cards, which appears randomly determined only because we aren't tracking all of the initial conditions and variables involved. The quantum level is truly probabilistic so far as we know—the information required to understand it in a deterministic way just simply does not exist, according to reigning thought on these things.) At the levels of complexity one is talking about, speaking of the world, or the human brain, in strictly deterministic terms is not always the most sensible way for coming to terms with moral problems, that much I agree. But searching relentlessly for some tiny part that might be somehow outside the rest of the physical system seems to me quite pointless on the face of it, and probabilistic functions are no less determined, even if their outcome cannot be predicted ahead of time. --Mr.98 (talk) 12:30, 11 July 2010 (UTC)

I concur with the point of view that free will is not random. Therefore deterministic models of human mind are likely better models to explain our perceived free will. Dauto (talk) 13:21, 11 July 2010 (UTC)

I somewhat disagree (but not with your conclusion). Randomness does not equate to what most people think of as "free will". When you roll a dice - does the dice have "free will" to decide what number will come up? No! It's just obeying the laws of physics. That doesn't stop it from coming up with different numbers each time you roll it - and it doesn't mean that there aren't 'weighted' dice that come up with a '6' more often than the other numbers.

There are undoubtedly random effects going on here - between quantum effects, external 'noise' sources impinging on the neural network and chaos theory effects, there are plenty of reasons to believe in randomness in the brain. The brain is a massively parallel, asynchronous machine, without timing interlocks of any kind. Which means that (in computing terms) it's going to be super-sensitively dependent on internal timing and 'race-conditions'. To try to put that into concrete terms: Suppose someone asks you a question that doesn't have an automatically "right" answer. One part of your brain starts assembling data that would result in a "Yes" answer and another part is coming up with other information that would produce a "No" - then differences in speed between those two parts (which could depend on anything from what you ate for breakfast to the phase of the moon!) might cause you to answer the question differently each time you are asked. That might make it 'seem' like you were making a 'free choice' - when in fact, it was essentially just a random fluctuation.

However, I don't see how any of those things results in an assumption of "free will". After all, we can plug random number sources and timing weirdnesses just like this into any 100% deterministic computer and have the result of a question be somewhat randomly determined - and we certainly wouldn't say that was "free will"! I have had plenty of programs that I've written that have "race-conditions" that I hadn't noticed that would cause the program to behave differently each time I ran it. In software, we'd generally call those "bugs". Some programmers use the specific term "heisenbug" to describe them because any attempt to pin the bug down causes it to behave differently!

So I definitely don't hold with the idea of "free will" - that smacks of something highly non-scientific, verging into matters of "the soul" and all manner of other metaphysical bullshit. However, that's not because of a lack of randomness - it's because the brain is just another computing machine (albeit a somewhat flaky one) - and it has to obey the exact same laws of physics as the laptop on your desk or that rock over there.

SteveBaker (talk) 16:40, 11 July 2010 (UTC)

I fully agree that free will has nothing to do with randomness -- the idea that it does is an artifact of most people's intuitive dualism. And I also agree with Steve that there is a lot of randomness in the human mind at the macroscopic level -- and not just the human mind. I've studied the behavior of rats running on a T-maze, where on every trial they have a choice of going right or left, with no motivation to choose one direction over the other. The rats have a pretty strong natural tendency to alternate, choosing the opposite direction from the previous trial, but there are lots of exceptions, and it is extremely difficult to find any deterministic pattern in them. It even goes beyond mammals: Paul Grobstein has studied decision-making in frogs, and found that their choices seem to contain a large component of unpredictable randomness. Why does this happen? Nobody really knows -- my guess is that it happens because operant conditioning requires a basic mechanism for randomizing behavior as a starting point for learning. In other words, you can't find novel solutions to problems if you can't start out by experimenting randomly. Looie496 (talk) 17:08, 11 July 2010 (UTC)

I would just point out, to both Steve and Looie, that there are two different (among many) definitions of "randomness" here. One is like dice—they are only random in the sense that our model of them and their conditions is insufficiently complicated enough to calculate the outcome, but with a sufficiently omniscient model of the initial conditions and the rolling mechanism, you could hypothetically calculate out what the next roll would be at "classical" (non-quantum) scales. It is only "random" in the sense that it is complex. The other is a quantum definition, where the information to predict the end-state simply is not there. The probabilistic nature of quantum effects is, as far as our theory tells us, utterly and irreconcilably random. It is not random because it is complex—in fact, it is quite simple, by comparison. But knowing all of the initial conditions will not tell you whether a given atom of a given radioactive element will decay at a particular point in time. From a philosophical point of view I would consider those to be quite different. A decision-making process that is "random" because it is a complex mixture of variables and conditions is not quite the same thing as one that is "random" in the sense that it is non-deterministic. Now I do agree that in both cases, as I said before, there is no way that I can see to turn either of those forms of randomness into something like "free will," which I do agree with you is not a scientific concept anyway. --Mr.98 (talk) 18:36, 11 July 2010 (UTC)

Yes, I'm aware of the difference between randomness and pseudorandomness. But where brain function is concerned, they both have the same consequences. (Quantum randomness is relevant because of the so-called Butterfly effect, which amplifies tiny perturbations into large differences, and is sure to operate strongly in a system with the powerful positive feedback loops that the brain has.) Looie496 (talk) 23:15, 11 July 2010 (UTC)

You do realize, however, that the usual (philosophical) understanding of 'free will' sees both determinism and randomness as a lack of free will, right? determinism signifies a lack of free will because it violates the 'free' aspect; randomness signifies a lack of free will because it violates the 'will' aspect. free will implies that you can make an exercise of will (which implies focus and function) which is not predetermined by material conditions. Altruism is often pointed to as an example of free will (and suffers the same philosophical critiques as free will). --Ludwigs2 23:34, 11 July 2010 (UTC)

Note that free will is often (implicitely) invoked in certain discussions, e.g. when you need to assume that the experimentor has the free will to choose the setting of his measurement apparatus in an arbitrary way. 't Hooft (who still believes that local deterministic models are feasible) has recently commented on this issue. Count Iblis (talk) 00:18, 12 July 2010 (UTC)

Condition with monologuing, stream-of-consciousness speech

Is there a psychiatric or neurological condition characterized by extreme talkativeness (e.g., a monologue that may go on for 15 minutes or more), stream-of-consciousness-like speech in which a particular theme is carried for maybe 15 seconds, followed by another, tangentially-related theme, and so forth, and attention to irrelevant detail (such as giving the home addresses of persons whose names come up)? Thanks in advance for your attention. 70.50.64.16 (talk) 06:00, 11 July 2010 (UTC)

Williams Syndrome can look a lot like that. So can some forms of mental retardation or autism. Looie496 (talk) 06:20, 11 July 2010 (UTC)

We can give direction if you're looking for an answer to a random question. If you are asking for a real person please consult a medical doctor. --mboverload@ 06:45, 11 July 2010 (UTC)

talkativeness is a symptom of many different psychological conditions (as well as being part of the spectrum of normal behavior). In and of itself it is not indicative of anything without a proper differential diagnosis. if it's behavior that in some way interferes with the person's life, they should consult a therapist. --Ludwigs2 07:00, 11 July 2010 (UTC)

The symptoms you describe, I believe, are called Pressure of speech. This is not a diagnosis, this is the answer to your direct question. We can not and do not provide diagnoses. If you suspect that someone you know exhibits these symptoms, please consult a specialist. --Dr Dima (talk) 08:45, 11 July 2010 (UTC)

Stumbled upon Tachylalia. Consult a specialist. --Ouro (blah blah) 10:23, 11 July 2010 (UTC)

These conditions may also be seen in Asperger's Syndrome, monomania, and a "verbal" form of hypergraphia. ~AH1^(TCU) 14:39, 11 July 2010 (UTC)

I have Asperger's and I have a definite tendency to "monologue" which I try (but fail) to notice and curtail. But in my experience, 'aspies' don't randomly change the subject every 15 seconds - instead tending to drill down in more and more detail in the same obsessive subject for as long as you let them...and if you happen to catch one of their 'pet' subjects, 15 minutes would barely be enough to get started! In my case (and, in most others I've seen), simply interrupting the person and telling them to please stop talking is a good thing...and it shouldn't offend them. I'd prefer the momentary annoyance of not being able to finish that extended thought - to the realization that I've monopolized the conversation and upset everyone within earshot. Of course if you're interested in every possible detail of how a 1963 Mini Cooper works, how it was designed and which Monte Carlo rallies it won - please feel free to ask and I'll be more than happy to give you a two hour dissertation! It's also not just speech...people who frequent these Reference Desk pages will surely have noticed how my posts are much longer and (arguably) overly-detailed than those of normal people. SteveBaker (talk) 15:50, 11 July 2010 (UTC)

Do not assume that a psychiatric or neurological diagnosis is necessary if talkativeness can be explained by simple enthusiasm or nervousness. A self-absorbed actor met a lady and told her about his career, talking for an hour non-stop about his theatrical successes. Eventually he ended by saying "Sorry I've been speaking only about me and I would rather hear about you. Tell me, how did you like my latest play?". Cuddlyable3 (talk) 21:57, 11 July 2010 (UTC)

Resonating chimney creates infrasound in breeze?

When its quiet at night I can often hear or feel an unpleasant very low-pitched noise in one particular room. That room has a chimney that has been closed up, nearly. The total length of the chimney must be about 25 feet. I cannot detect where it is coming from, only guess. Perhaps the chimney is resonating like an organ-pipe or like blowing across the top of a bottle.

What frequency of sound would a 25ft long organ pipe make? Would the frequency of sound of it in bottle mode be similar? Thanks 92.15.3.130 (talk) 11:35, 11 July 2010 (UTC)

The first harmonic frequency would be 11hz. Slightly lower actually, once you include the diameter (and harmonics at the odd multiples of this). See Acoustic resonance. That said I've never heard of it happening with a chimney, although I have with caves. I'm pretty sure you'd need some fast wind, a regular breeze probably wouldn't work. (But I'm not really sure.) Ariel. (talk) 12:38, 11 July 2010 (UTC)

The formula given in the article suggests about 11Hz, with harmonics at 33hz, 55hz, etc. Assuming the loudness of the harmonics decrease as the Hz rises, and that the unhearable 11Hz modulates the higher harmonics, it may well explain what I've been hearing. 92.15.3.130 (talk) 16:44, 11 July 2010 (UTC)

My next question is - how would the subjective loudness or energy (not the same thing) of the various tones compare? Would the noise I could barely hear be accompanied by more powerful infrasound at 11Hz? 92.15.3.130 (talk) 16:49, 11 July 2010 (UTC)

Perhaps a house with windows open in the summer could act like a very low frequency whistle. Maybe this might explain The Hum. 92.28.255.202 (talk) 10:08, 12 July 2010 (UTC)

Anecdotally, when I used to live in St Andrews there was one high-walled, open-ended alley I regularly walked through where I could, often at night but rarely during the (noisier) day, just hear a very, very low sound, on both the pitch and volume thresholds of audibility. After some deliberate observations I determined that this was not related to the sometimes similar low growling sounds of aircraft active at RAF Leuchars several miles away, and concluded that it was probably an 'organ-pipe effect' caused by wind and the alley's physical characteristics. Until I consciously noticed the sound, I often felt uneasy around the alley, and I have read speculations that some "haunting" experiences may be triggered by infrasound. 87.81.230.195 (talk) 22:42, 12 July 2010 (UTC)

Parkinson's disease differences from chronic alcoholism

How are the symptoms and diagnosis of these two differentiated? Thanks 92.15.3.130 (talk) 11:43, 11 July 2010 (UTC)

You may be interested in Parkinson's disease#Diagnosis and Long-term effects of alcohol. The tremor experienced by people with Parkinson's disease is different and usually more severe than that in alcoholism. The Parkinson's disease article describes it very well; the alcoholism article not quite so well. Regards, --—Cyclonenim | Chat  12:40, 11 July 2010 (UTC)

As for the temors experienced in alcohol withdrawl, see delirium tremens. ~AH1^(TCU) 14:37, 11 July 2010 (UTC)

Typically in Parkinson's the symptoms originate on one side of the body and worsen and remain worse on that side even after symptoms begin to affect both sides of the body. This is NOT seen in alcoholism induced tremors. Secondly Bradykinesia- slowing of voluntary motion is a hallmark of Parkinson's. This is not seen in Alcoholism. Finally significant improvement with levodopa, is seen in Parkinson's. A careful history and simple CNS examination can distinguish the two. Hope this helps.--Fragrantforever 04:49, 12 July 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

Where is the 2nd dimension?

I was watching this video, http://www.youtube.com/watch?v=UnURElCzGc0 with Carl Sagan explaining the fourth dimension to laymans using the second dimension as an analogy.

I showed it to my friend and he was a bit skeptical. He says that we strictly live in a 3D universe, and he gave a rather convincing argument for it that had me stumped. Rather than paraphrase what he said, I'll just quote him directly so I don't lose any of his arguments.

"Yea, the 1D-2D bullshit. The guy in this video tells you: IMAGINE, that there is a flatland. Okay? Why do you want me to imagine? Isn't there a 2D realm already? He asks you to ignore the height of the square and just try to pretend it doesn't exist.

So, what is he doing now? He is asking you to ignore reality (which is the only thing that exists)and recall a non existing "idea". You see, in our universe, squares don't really exist. Lines don't exist either. Lines, squares circles, and all 2D shapes are all just perfect ideas. They don't exist in our universe. You can draw a line and it can seem to be perfect, but, after you zoom in you will see imperfect and rough edges. You can use laser sharp cutting and it will be perfect this time. But, you zoom in more, still, it's not perfect. You will never ever reach a perfect line.

When you talk about a square, you KNOW you're talking about something that's so perfect that it doens't exist. And when you build a square building, no matter how accurate, you're just immitating the absolute idea of a square. Something your brain had imagined one day and you're trying to achieve it. So, it's WRONG to think that there is 1D, and then comes 2D, then our 3D. Because, all that exists in the universe is 3D. The other "D's" are philosophical ideas. And so is the 4th dimension. The 4th dimension is a "clever" approach to apply perfect ideas to try to imagine how the 4th dimension "would" look like. But, it's not more real than you imagining what would have happened if we lived in a cube planet. You can derive euqations to try to understand how gravity would be like? how the earth orbit would be like? But, that's all just on paper.

People who use the (2D-3D) (3D-4D) analogy try to convince you that there IS a fourth dimension and that you are to it as a 2D realm to 3D one!!!

FUCK! Did we approve 2D realm as a reality now? Didn't we just agree it's just our imagination?

I believe other dimensions are just "other scenarios" of the same 3D universe. This is all I can approve. Because it's a general rule that can be applied on lines and squares, and on our universe too.

2D is a realm of infinite scenarios of 1D. 3D is a realm of infinite scenarios of 2D. and 4D is a realm for infinite scenarios of 3D, and there it stops. And, since there is no 1D or 2D, then it's only 3D with different scenarios and that's ALL."

I thought about what he was saying, and it made sense. There are no true 2D objects except those we think of in our heads or exist in abstraction. Or are there? Could it be that all objects have a projection in 2D but we can't see it because we only see and experience the universe in 3D? ScienceApe (talk) 14:33, 11 July 2010 (UTC)

Your friend obviously lacks imagination. What Sagan is asking you to do is to IMAGINE a 2D world. Not that there is a 2D world - just use your imagination. The problem he is trying to solve is to explain how a fourth spatial dimension might work. That's difficult because our brains are not well-equipped to imagine a 4D world (and here we're talking strictly about four SPATIAL dimensions - we're not talking about 4D as in three spatial dimensions plus time. To try to help our imaginations along - to understand (at least at some level) what an 'extra' dimension would be like, it's easier to imagine that we're 2D beings in a 2D universe - then to imagine how the 'extra' third dimension would appear to such beings. Most people have no trouble whatever imagining 2D - there have been at least a couple of fictional stories written about 2D universes..."Flatland" (which I, personally, think is a pretty terrible book) and "Planiverse" which makes it onto my personal "top 20" bookshelf.

So, we have to imagine creatures whose whole existance lies on the surface of (let us say) a sheet of paper. Now we know this 2D universe doesn't really exist (and according to some of the appendices of Planiverse, cannot exist as a meaningful thing because chemical reactions would be impossible in 2D)...but this is just a thought experiment. So these 2D creatures would look to us like drawings on a page.

This is easy to imagine. Think about the PacMan game. It is set in a 2D world. The 'walls' of the maze have no height. PacMan is a circle with a mouth, not a sphere. The ghosts are just 2D shapes. When PacMan is caught between two walls with a ghost coming towards him from both directions, he can't put on a James Bond jetpack and move out of the screen to avoid them...he's trapped in a 2D world. Now - that's not hard to understand is it? So the question is, if we go to PacMan and tell him that there really is a third dimension - and that he could escape the ghosts easily by moving "up" and out of the screen...or tunneling "down" under them. This would be a very tough concept for his tiny 2D brain to imagine.

Just as it's hard to imagine (for us) escaping out of a doorless, windowless jail cell with solid walls, roof and floor by moving in the 4th dimension...stepping "up", going past the walls and then back "down" again. Unfortunately, we don't even have good words for "up", and "down" in the 4th dimension...which makes even discussing this problem tricky! Suppose we make some words: Norf and Souf (like North and South) to describe directions in the 4th dimension. We have cell walls to the north, south, east, west, and floors above and below...but the stupid 3D prison cell designers forgot to build walls to the Norf and Souf! So as 4D beings, we walk out of the cell by moving Norf - then a little to the East - then back Souf again! It's just as easy for them as if the jailer forgot to build North and South side walls for our cell!

This is hard to imagine - but let's do the analogous thing in PacMan-land: PacMan is stuck in a square jail cell - encompassed by four typical pacman game walls to the North, South, East and West. But nobody built a floor or ceiling to his jail. But if a 3D being like you or me were imprisoned in pacman-land, we could simply step over those pathetic 2D walls by moving "up" - then east then back "down" again.

The analogy here makes it much easier to imagine those "Norf" and "Souf" directions - which our poor little brains simply can't grasp - by imagining how pacman has problems understanding "up" and "down".

What's worse about your friend's rhetoric is that he claims that 4D is the most you could have...but one of the leading scientific theories that we have to explain how our 'for-real' universe works (string theory) requires there to be somewhere between 15 and 26 actual 'for-real' spatial dimensions! It is quite possible (and some would say, almost certain) that we really do live in a 26D universe!

But it does require an effort of imagination and a degree of patience to follow Sagan's explanation - and I guess some people are simply incapable of doing that - which is sad. Anyway, if this interests you (and I surely hope YOUR imagination is up to it) - then grab a copy of Planiverse and prepare to have your brain stretched!

SteveBaker (talk) 15:18, 11 July 2010 (UTC)

for a person who laughed at the idea of sound waves being represented in a physical form for the lack of proof ( Steve Baker) possesses quite a vivid imagination to assume we live in a 26D universe!!! where did the proof come for this 26D universe steve? or do you ask for proof only when it suits you? Most of us could argue that the argument of the OP's friend is perfectly sane... and would suit most scientific minds.... My suggestion is to continuously think out of the box and not to ridicule or laugh at what appears to be fantastic today for lack of proof like how Steve Baker dramatically did using quite a few profanities in the thread about representing physical matter in the form of sound waves.--Fragrantforever 16:27, 11 July 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

Fragrantforever: see Bosonic string theory. – ClockworkSoul 16:56, 11 July 2010 (UTC)

The "proof" of dimensions is a mathematical construct, thus all theorems associated with them are perfectly correct. The application of those dimensions to the physical world is something that simply works, and works well, thus we see three dimensions around us, referred to as 3D, and it corresponds pretty much exactly with the mathematical form (and for reference, we get another hint on Earth where the pull of gravity marks the z-axis and the surface of the earth is x-y). As physics expands, we find that we can make time into a fourth dimension, with a major difference in metric, and again still fit the dimension model just as easily as we did with space. Note that all proofs still hold, once we fit reality so well to the math. When Steve refers to the possibility of a 10D or 26D universe, that refers to a specific framework of particle physics that is still debatable, but if the clues fall into place, then through the same mathematical theorems we will understand that there are 6 or 22 more "hidden" dimensions that only the borderline-possible fundamental particles see, but we here on Earth still only see four. SamuelRiv (talk) 16:59, 11 July 2010 (UTC)

Really this is a generic know-nothing argument that can be used against any scientific discovery since Copernicus. Of course the Earth isn't moving—isn't it obvious? You know what it's like to be in a moving vehicle. Of course matter isn't made of atoms; have you ever seen an atom? Have you ever seen a new species arise? And so on. The evidence supporting modern science is very subtle. If it weren't, it wouldn't be modern science, because the ancients would have discovered it already. Nevertheless, the evidence is there, and in such overwhelming quantities that you can't help being persuaded by it once you've found it. Incidentally, the three-dimensionality of space isn't obvious either. The experience of space is so immediate and unconscious that it took a long time for anyone to realize that one could associate the number 3 with it. A possible response to this argument would be to say "I don't believe that space is three-dimensional. Can you convince me?" and then see if he can do it without asking you to imagine two-dimensional space. -- BenRG (talk) 18:38, 11 July 2010 (UTC)

The OP's friend expresses an objection to the elements (point, line, sphere,..) of Euclidean geometry that Buckminster Fuller made in his book "Synergetics". It is correct that none of those primitive elements can be physically realized in the real world of atomic particles. However that does not invalidate the use of orthogonal dimensions to make 3 independent measurements that together uniquely locate a real object in space. The friend is confusing construction with analysis. Sagan (a consummate explicator) demonstrates removal of information about a dimension in order to prepare a thought experiment about how we might perceive information on a 4th dimension. The hypercube model can be interpreted as being the history of a cube whose size changes during a span of time where time is posited as the 4th dimension. The friend's closing statements about "scenarios" such as "2D is a realm of infinite scenarios of 1D" would be better understood in terms of calculus, thus "a 2D area can be differentiated into infinitely many lines". Again, this is all about analysis not real construction. Cuddlyable3 (talk) 21:40, 11 July 2010 (UTC)

This is turning out to be a very interesting and enlightening thread. But what I dont understand is that some people quote the Bosonic string theory and refer to tachyons and invoke the idea of 26D when they are on this thread and on an another thread laugh at the idea of tachyons and possibility of travelling faster than the speed of light. If you beleive the Bosonic String Theory to be true and beleive Tachyons exist, then you should beleive that it is ( atleast experimentally) possible to travel faster than light. How can you invoke parts of such theories when it suits you and reject parts of it when it doesnt? My arguement is, all these are hypotheses with limited proof only in lab settings, if we start demaning proof for every theory we would never proceed anywhere. The reason why I raised my objection was we were discussing several weeks ago, if physcial form can be transmitted as sound waves - a very knowledgeble person ridiculed and rubbished this idea for the lack of proof. But now truns around and talks about tachyons and 26D. Shudnt we have a moderation in our demand for scientific proof? The beauty of science ( I Repeat) is that what seems too fantastic to be true today could be a very well accepted fact in a few years or months. --Fragrantforever 04:22, 12 July 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

... or what seems too fantastic can very well be laughed at as the silly imaginings of science-fantasy writers when a proper theory is found that has experimental verification. Faster than light, parallel universes, more than three dimensions (allow 4 for space-time), wormholes, transmission of matter by sound waves or light waves or "transporters" etc all fall into the fantastic category (IMHO). We are fascinated by the concepts, discuss the theories, develop the mathematics, but we don't know whether we are talking about fantasy or reality until we have experimental evidence. Dbfirs 06:57, 12 July 2010 (UTC)

The 26-dimensional bosonic string theory is unrealistic for several reasons, but it can still be useful to study unrealistic theories because they can give insight into more realistic theories that are more difficult to solve. Note that "tachyon" doesn't mean what you think it means. In field theory (and string theory, I believe), the speed of information propagation is always c, regardless of the nature of the particle. Tachyons in field theory are formally analogous to classical faster-than-light particles in a certain way, but they don't propagate faster than light. Also, tachyons aren't automatically fatal to a theory. They make the vacuum unstable, but there might still be a different, stable vacuum. In fact, this is exactly what happens in the Standard Model; the fundamental Higgs field is tachyonic. What is fatal is when there's no such stable state, which is the case in bosonic string theory, I think. -- BenRG (talk) 09:15, 12 July 2010 (UTC)

Actually, tachyon condensation says "the fate of the closed string tachyon in the 26-dimensional bosonic string theory remains unknown", which seems to imply that the tachyon might not be fatal to the bosonic string theory after all. I have no idea. -- BenRG (talk) 09:20, 12 July 2010 (UTC)

ScienceApe: your friend's argument is stupid because cubes don't "exist" either -- so by his/her argument, neither does the 3rd dimension. 63.17.82.101 (talk) 09:52, 14 July 2010 (UTC)

Surprised no one's mentioned the Möbius strip. 67.243.7.245 (talk) 01:30, 19 July 2010 (UTC)

fluorescent light

how to disposing of long fluorescent light bulbs without breaking them —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 19:49, 11 July 2010 (UTC)

In Norway, shops that sell electronic articles are required to accept them and dispose them free. That's useful if you happen to be Norwegian. Cuddlyable3 (talk) 20:55, 11 July 2010 (UTC)

That relates to a similar situation with the Waste Electrical and Electronic Equipment Directive, which only applies in the European Union.Sf5xeplus (talk) 22:03, 11 July 2010 (UTC)

Ask the organization that collects garbage where you are. In my case, they used to be collected as ordinary garbage but now I have to keep the things until the next annual "Environment Day" or take them to an inconvenient "household hazardous waste" site. --Anonymous, 21:35 UTC, July 11, 2010.

Where are you located? What country? At least near where I live, Ikea takes them. Ariel. (talk) 22:08, 11 July 2010 (UTC)

I live in the US and dispose of them in the regular trash (sorry green people). --Chemicalinterest (talk) 01:13, 12 July 2010 (UTC)

Here in Spain, they are often disposed of in the normal glass recycling bins. That's what my local council told me to do last time I asked them (not that I trust them to know the answer, but I couldn't be bothered to look it up). Modern domestic flourescent tubes are nowhere near as toxic as the early models in any case, but correct (and actual) disposal procedures will vary from place to place. Physchim62 (talk) 01:45, 12 July 2010 (UTC)

Common 4 foot fluorescent tubes sell for about $1.60 retail in the U.S., and cost the merchant about $1.50 to $2 a piece to recycle in bulk [1]. This is more than the merchant's profit on selling a new one, so the merchant has a substantial net loss if he sell a fluorescent tube and accepts the old one for recycling. If he accepts one for recycling that you bought elsewhere, the loss is naturally greater. Some merchants accept them for "recycling," then smash them in the dumpster (to prevent kids taking them out and smashing them somewhere else). The compact fluorescent bulbs are cheaper to recycle. Some good-hearted people have gotten the recycling bug to the extent that they want to recycle common incandescent light, which is nonsense. Edison (talk) 02:16, 12 July 2010 (UTC)

That depends what you recycle them as! Here in Spain, the glass is collected separately, but not recycled as glass, just crushed and used as hard-core for roads. It cuts down on the amount of landfill (and makes for safer recycling of other waste), but is much cheaper than trying to do "glass-to-glass" recycling, which requires separation of colours and glass types. Physchim62 (talk) 02:34, 12 July 2010 (UTC)

Fluorescent tubes contains mercury and most incandescent light contains lead, that is the reason they should be treated separately. The amount of glass is insignificant so recycling it has limited utility. I would be very surprised if it is legal to dispose them in glass recycling bins in Spain as it is part of EU. I do not know about US regulation but they should not be smashed in the dumpster and any regulation that give merchants economic incitements in doing so without proper control is clearly flawed.--Gr8xoz (talk) 09:17, 15 July 2010 (UTC)

Tetramethrin

Are there any known cases of toxicity in humans from tetramethrin? Unlikely given the minute quantities we're exposed to and I'm not even sure if anything in our bodies reacts to it as it's used in wasp killers, but I'm curious if it does present effects in humans. Regards, --—Cyclonenim | Chat  22:39, 11 July 2010 (UTC)

According to the references at the bottom of the tetramethrin article: [2] and [3], these chemicals are really very safe. They don't absorb through the skin, absorption through the lungs is slightly more of a concern, but the chemical is metabolised quickly by mammals. They had to feed rats an entire gram of the stuff per kilo of bodyweight to get an effect - scaled up to human body size, that would require you to eat a hell of a lot over a short timespan to suffer a risk that way. I don't think you have to worry - and probably the best precaution is to avoid breathing too much of it over a short period of time. SteveBaker (talk) 22:52, 11 July 2010 (UTC)

The safety data lists it as irritating to eyes, skin, and respiratory systems, but the LD50's (lethal doses) are very high. Looie496 (talk) 23:04, 11 July 2010 (UTC)

Up to 1990, when the last WHO review was carried out, there were no reported cases of poisoning or adverse effects in humans [4]. Pyrethoid insecticides are known for having very low toxicity for mammals: they can be substantially more toxic to birds, reptiles and fish, which leads to some environmental concerns. Physchim62 (talk) 23:15, 11 July 2010 (UTC)

Remember though that measures like LD50 are generally talking about acute toxicity. Long-term effects are much slipperier and harder to measure. In the first PDF link given by Steve, we read that a committee at EPA reviewed the carcinogenicity data of pyrethrins in animals and decided thatthey showed carcinogenicity, but they were unable to classify pyrethrins into a carcinogenicity group until some of the tissue specimens [...] were re-read.

Now, my general sense is that if you wanted to avoid everything with even this much hint of cancer-causing, you'd have a tough time in this world. Still, it's a note of caution; I wouldn't be reckless with the stuff. --Trovatore (talk) 03:52, 12 July 2010 (UTC)

Thanks guys, pretty useful stuff. Regards, --—Cyclonenim | Chat  09:19, 12 July 2010 (UTC)

Electric stove

My understanding is that an electric stove is essentially a big resistor. If so, will you get electrocuted if you touched the stove while it's on (because of the current running through it)? 74.15.137.192 (talk) 23:04, 11 July 2010 (UTC)

No. The 'elements' of the cooker are insulated. --Tagishsimon (talk) 23:06, 11 July 2010 (UTC)

It's usually a Nichrome wire (or coil) inside a ceramic tube. See Heating element. But it's not always like that, inside a toaster, or a space heater for example it's not always insulated. Ariel. (talk) 00:44, 12 July 2010 (UTC)

Blow dryers have bare nichrome wire. I dissolve it in hydrochloric acid to get nickel and chromium compounds. --Chemicalinterest (talk) 01:12, 12 July 2010 (UTC)

If you touch a metal spoon to a hot stove element and touch the handle of the oven door with your other hand you DO feel the electric current. I tried it! —Preceding unsigned comment added by 142.104.215.119 (talk) 01:36, 12 July 2010 (UTC)

That is surprising. There may be faulty insulation. I do not advise passing electric current through your body as an electrical test in the manner you describe. Edison (talk) 02:08, 12 July 2010 (UTC)

In India, at least such elements (as we call 'em here, like a heater's main coil etc) are never insulated. Newspapers are filled with numerous accidents, sometimes even "accidents", when the heater kept on the window-sill fell down in full bathtub and the bather gets electrocuted. Of course, the bather is mostly a newly-wed bride... Jon Ascton  (talk) 04:55, 12 July 2010 (UTC)

The ones on top of the stove (range) are always insulated - otherwise any metal pot would short them. If an insulated heater fell in water it would still be bad - the insulation is only for the external parts, the internal wiring, switch, etc, are never fully insulated. Ariel. (talk) 05:45, 12 July 2010 (UTC)

Note your's "always" and mine "never" ! That's huge difference in safety-standards, between us ! Kipling was right - "East is east, and West is west / And never twain shall meet..." Jon Ascton  (talk) 06:13, 12 July 2010 (UTC)

No, you are talking about different types of heating element. Both are common in both countries. In the UK it is illegal to fit uninsulated heaters in a bathroom, but this doesn't stop people using them there and sometimes electrocuting themselves (or their brides?).Dbfirs 06:30, 12 July 2010 (UTC)

An uninsulated stove-top element wouldn't just be dangerous, it would be nearly unusable. Besides which, hot nichrome is a bit delicate, even expecting you to put a non-conducting pot directly on the element would be essentially the same as selling a stove that didn't work for more than a few days. APL (talk) 16:19, 12 July 2010 (UTC)

Are you suggesting that the newly wed brides are murdered, or that they are killing themselves, or that they have poor safety habits? --Sean 19:44, 12 July 2010 (UTC)