gcol

Ring configuration: After giving my brain a couple of caffeine shots, I came up with this, and you will be hardput to dissuade me. 12 magnets, for convenience, arranged in a circle, numbered as a clock face. Turn the 6 o'clock, the 7 and 5 will move. the 8 and 4 less, 9 and 3 even less, and 12 o'clock not at all, because it is being acted on equally and oppositely. Thus we have in effect two straight lines of magnets, where the 12 magnet acts as the common fixed end. From here, one can fiddle with uneven strength and spacing as before, so that with care any magnet from 7 through 12 to 5 may act as fixed.

I would suggest either a series of magnets of decreasing strength, or equal magnets spaced at increasing distances, perhaps? Have not previously considered positioning them in a nose-to-tail ring formation, as a closed loop, all free to rotate. Began to imagine it, but brain began to hurt. Might be easier to make a demo device, using bar magnets which are cheaper and easier to obtain. Might make an interesting executive desktop toy.

Swansont: Agree. And also, I am wondering whether in fact any of them will flip, except for the one to which external torque is supplied. (For the case where the one on the opposite end is fixed). That torque must be distributed over the intermediate magnets, none of which can therefore have more torque than the first. (The second more than the third, the third more than the fourth, etc.) The second may therefore almost get there, but not quite. The greater the number of magnets, the smaller the torque on any intermediate one. I am assuming that all magnets are of the same strength and are evenly spaced. Uneven spacing and strength may be a special case. Am I right?

Remembering the fuss about the dangers of lead in paint and petrol, asbestos in insulation, DDT, cadmium in batteries, etc., and how the debates always resolved to "yes, we know how dangerous it is, but for the convenience of commerce and profit, we can make a case for the risk to be acceptable". The problem is always to demonstrate statistically just how many deaths are caused, and the difficulty and expense of doing such research. How many deaths per annum would you find personally acceptable as a trade-off for the convenience of light sources containing mercury? 100, 500, 1000, more? How often do we pay for our convenience with other peoples' lives?

I have realised that a row of circular magnets on a common axis should exhibit the same characteristics as a torsion wire, as long as no magnet turns more than 180 degs. Past 180 is the equivalent of snapping the wire, but in the case of 'magnetic torsion', the wire will in effect re-join. From what I gather concerning sophisticated setups, it is this process of snapping and re-joining that exhibits interesting and non-intuitive effects. Am I on the right track?

I googled this: "fluorescent lamps mercury toxic" and got some, to me, worrying results, including 2-4 tons of mercury released in the U.S. each year through the disposal of fluorescent lamps. Mercury content per lamp varied per manufacturer, but was something like 3.5-6.0 mg per lamp, in the dust. Make of it what you will. But is the danger to be airily dismissed? I doubt it.

The question is indeed a moral dilemma. On the one hand we have the high moral stance of St. Francis of Assissi and some Eastern religions that would not tread even on an ant, and those of us struggling with the compromises that the real world demands. Assuming that most of us eschew the two opposites, that leaves us to wrestle in the mud of the middle ground and we end up by arguing over moral niceties. I fear that a point of universal agreement will never be reached. If it is however in one lifetime, it will surely change in the next. The balance of opinion forever shifting. Reasonable people should hold strongly to the middle ground, and fight against the extremes with equal vigour. For me, that is where this discussion ends.

I hope it was not my remark about rocket scientists and tool-room techies:-) They might spin if each magnet has gained enough inertia to carry it past the "dead" point., but the spin would be terribly jerky, no? Having second and third thoughts about the torsion wires. If I creep up on it, and don't allow any magnet to turn more than 180 degs, there will be no "twanging". Then I realised what the result could be. Take a row of say 5 ring magnets, an end one fixed, the others free. Rotate the first free one 24 degs, the next one will turn 18 degs, the next 12, then 6, the last being fixed 0. But now I have input 24 degs of torque, and the total torque of the intermediate magnets equals 36.....er, can't be right, can it. Where have I gone wrong?

I think you may have the wrong end of the stick there. If each ring magnet is free to turn independently, then when they are aligned at the point of mutually attractive equilibrium, it will be as if they are mechanically coupled. All the magnets would act as a single long magnet. Then turning one will turn the others easily, restricted only by the sum total of bearing resistance. The spacing between them would surely only be significant if far enough to weaken the quasi-mechanical link when not strong enough to overcome bearing friction. Now unless there is a difference in principle between a line of common axis ring magnets and a line of individually mounted bar magnets, then the effect should be the same surely, and easier to visualise? Now consider restricting a magnet. By exerting enough turning force on a distant moveable one, the force exerted on the fixed one can be no greater than that required to break the link.

Paranoia & JesuBungle: Apologies if I jumped to a hasty conclusion, perhaps I am becoming paranoid. Please forgive. Severian: If your Avatar reflects your vision of a "beautiful mankind", then beauty is definitely not in the eye of this beholder.

I see Religion has crept back in again, can't teach old dogs new tricks. More than one statement recently I could have quoted as examples. Got any evidence for these preachy assertions? Not exactly scientific, are they.

I began a prototype, using some tasty ring magnets (easier to mount) and immediately hit a massive engineering problem. The "cogging" effect. Anyone who has tried to use a stepper motor as a generator will know what I mean. The sideways strain on the bearings was immense, and the vibration. The torsion wires twanged like piano strings. Hard won lesson: Theory and thought experiments are often easy, devising a practical test and putting it into practice is something else again. You don't have to be a rocket scientist to devise a mechanism, but without the practical tool-room techie, you can't build a rocket.

For an example of mass rape being a successful reproductive strategy, just google Genghis khan and how common his Y chromosome is now. An example, also, of where success does not equal good.

I vaguely remember a documentary where, indeed crocs travelled considerable distances over land. I have the feeling this was in response to overpopulation, search for new breeding grounds, or the young being driven out by mature crocs. Rather vague, sorry, but I do remember something along those lines.

YT: I use the phosphoric to clean the alu and copper electrodes in my homebrew cells. This next bit is seriously off-topic, please forgive in advance, but: 1. If I have not washed the copper thoroughly afterwards, when put back in the cell electrolyte which contains caustic soda, a yellow coating appears on the copper. Is this yellow phosphorous? 2. If a piece of iron is put into the phosphoric, together with the copper, not only does the iron become copper coated, but it adheres so lightly that most of it falls to the bottom and forms a fluffy clump. After washing and drying, the copper dust is so fine it will disappear if I blow on it gently. Just a couple of curiousities, probably of no practical interest to a real chemist.

Is the above discussion all theory, or experimental result? If no practical experiment has been done, then I am thinking of mounting several magnets on torsion wires, each with a scale, to determine exactly how much force is exerted on each. I envisage a deal of poke and hope to optimise the gauge and length of torsion wire. Not sure if I would have the patience to make 20 of the things though I ask because there are no actual measurments quoted. If I can get enough bar magnets, building the contraption will give me something to do during the winter evenings. If it has been done, tell me so I don't waste time reinventing the wheel.

YT2095: Just for you, secret, hush. http://www.growell.co.uk/p/0130/pH_Up_and_Down.html

I just received a 1litre bottle of phosphoric. 83%. I got it from a hydroponics equipment supplier. They call it "ph down", not phosphoric, which is its hydroponic use. £8 per litre. Several suppliers in the U.K. It is also used, of course, in the motor trade as rust remover & preventer

Have I missed a post where the danger to other pupils has been mentioned? In this case, no harm was done. But if they had injured someone, staff or pupil, the law would have been involved, the school sued, etc. etc. A strong example should have been set as to the reckless disregard for others. This is where the school, in my opinion, erred by being so lenient. And as for whether they obtained and consumed the alcohol on school premises.........

I agree completely. No pants. Your example, to me, comes squarely in the category of "annoying auditory fidgetting". People, including aggravating children, have been assaulted in extremis. It is also like an intrusion into your spatial comfort zone, I sympathise. Everything normal.

Are you trying to determine what annoyed you in this paticular situation, or can we consider the broader question of why some noises/sounds we find soothing, some thought provoking, and some damn annoying? It might be interesting to try and categorise them, but I suspect personal preferences will confuse the result. A couple of examples: The screech of chalk on blackboard, the screech of high violin notes, car alarms, the cacophany of a flock of squabbling sparrows outside your bedroom window which renders your alarm clock superfluous. Repetitive noises with time intervals where, during silent periods, you are on edge and tense just waiting for it to start again...... I could go on with a large list, very tedious, but you get the point. Different types of noise, different types of annoyance, not everyone affected by the same thing.

Right, right, right. Sarcasm, sarcasm, sarcasm. (Must use more smilies to avoid misunderstanding.)

How about an Agony Aunt forum? This idea prompted by the ongoing "girlfriend in a threesome" topic. In it could (should) go such heartfelt pleas such as feeling temporarily suicidal, and I may be a total jerk, but why does nobody love me?. There have been many others, too. Not worth trawling the archives to be specific. You all know what I mean. Personally, I find them embarrassing, incredible, or uproariously funny by turns. Nice to go directly to them when I need a good laugh. I keep out of them, because I am usually tempted to say something like "never mind, kiddo, when you start to shave and are dry behind the ears, you will look back and turn pink with embarassment at having paraded your insecurities in public."

You may have put your finger on an experimental error there! What is the standard way of measuring finger length used in these observations? The worried world must be told. Measured from the web between ring and little fingers I have: ring finger 8cm. From the web between ring and middle, I have ring finger at 7.5cm. For index finger. from web between index and middle, I get 7.4cm. By line of sight accros finger tips, the difference is 0.4cm in favour of ring finger. So the actual length of the ring finger is subject to a considerable experimental error depending on point of reference. Really worried now, should I go for a well-woman checkup?

Yes, perhaps we should, but the topic is not misandry (the opposite of mysogyny). I would not dare deviate from the purity of the thread and risk penalty points. It must be true, the bible says so! Do I really need such support for what is an OTT joke in a lighthearted thread in a mere discussion forum? Well, sackcloth and ashes for me, then:-)