Wikipedia:Reference desk/Archives/Science/2010 October 2

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October 2[edit]

plasma rockets-pbsnova[edit]

Plasma rocket to be tested in 2012 on space station would move space station76.28.54.105 (talk) 00:53, 2 October 2010 (UTC)

Is that a question or just a comment? Looie496 (talk) 01:07, 2 October 2010 (UTC)
Presumably you're referring to VASIMR. anonymous6494 01:39, 2 October 2010 (UTC)

YES it would move the station, the international space station could cruise around with VASIMR-like rockets, and that would be cool because they could explore the moon from orbit and then come back to an Earth orbit, thanks for pointing that out. The article referenced says it could be used for lunar cargo transport, or as a "space tug" and orbital transfer vehicle, the rockets I mean, but there is no reason I can think of why they can't use what is already there, the space station, for that for now. GabrielVelasquez (talk) 20:47, 2 October 2010 (UTC)

NO. The space station will not be leaving earth orbit with these or any other engines. It is too big and not built for lunar voyaging. It currently has something like 130 kW worth of solar panels but would need 8 mW (and somewhere to store 70 tons of argon propellant) Rmhermen (talk) 22:09, 2 October 2010 (UTC)

How much copper and/or gold is there in an HDMI cable?[edit]

HOW MUCH COPPER IS THERE IN A HDMI CABLE? ALSO HOW MUCH GOLD? —Preceding unsigned comment added by Mole800 (talkcontribs) 00:56, 2 October 2010 (UTC)

Just a bit of friendly advice: Try to sign your posts, and DON'T USE CAPITALS, because people WILL THINK YOU ARE SHOUTING.--Editor510 drop us a line, mate 09:31, 2 October 2010 (UTC)
That depends on the length of the cable. However, I think that most cable have ab 2 mm plastic coating and the rest copper. --The High Fin Sperm Whale 01:39, 2 October 2010 (UTC)
(edit conflict) It depends on the brand of cable, its length, etc. etc. Its impossible to make a general statement about the composition without knowing exactly which cable. Also, please do not type in all caps. In all internet forums, all caps is read as SHOUTING and is impolite. --Jayron32 01:41, 2 October 2010 (UTC)
Just weigh your cable, and probably about 90% of the weight is copper. The amount of gold is just a few micrograms to plate the contacts for the (partially) justifiable reason that bad contacts can cause a deterioration in the signal. Dbfirs 08:22, 2 October 2010 (UTC)
I'm not sure that that's true — for smaller-gauge wire, the layer of insulation around it is going to make up a proportionally-larger fraction of the total weight. (I agree completely with you about the utterly negligible amount of gold in the product.) I've seen HDMI cables marketed that are manufactured using anywhere from 22 gauge (quite heavy) to 28 gauge (lightweight) conductors. Nineteen 28 gauge wires will contain only about fourteen grams of copper per meter; rendered in 22 gauge cable you're looking at more then four times that mass. TenOfAllTrades(talk) 14:56, 2 October 2010 (UTC)
You make a valid point, and my estimate was only an approximation, but thicker cable tends to have a better insulation, and plastic is very light compared with copper, so I still claim that weighing the cable is the best way to estimate the weight of copper. Obviously 22 gauge will weigh about four times as much as 28 gauge, but that doesn't seriously upset the percentage, and have you ever seen nineteen strands of 22 gauge wire? Dbfirs 15:49, 2 October 2010 (UTC)

Indoor air quality solutions?[edit]

What are the best indoor air cleaners to remove pollution from motor vehicle exhaust? Many thanks! --3kdocnmjduif (talk) 01:49, 2 October 2010 (UTC)

HEPA filters will remove particulate. Catalytic converters minimize the release of nitrogen oxides, carbon monoxide, and unburnt gasoline. --Jayron32 01:55, 2 October 2010 (UTC)
It is the Clean Air Delivery Rate you need to use to compare devices with. Good units use a HEPTA filter, a carbon filter, and an ionizer. Just one on its own is no good for traffic pollution. Catalytic converters are not practical for indoor use.--Aspro (talk) 09:00, 2 October 2010 (UTC)
Here is an example of one that is suitable for a room up to 15m². [1] I bought a similar one for someone who stuffer from hay fever and pollution in general and he was amazed by how much better he could breath. I find its like walking into a room that is on a mountain top but then, after a time you gt use to it and its just every body else's house that smells like a dusty back yard of a fast-food-take-away situated under some flyover. --Aspro (talk) 09:39, 2 October 2010 (UTC)
I've heard some bad stuff about air ionizers - that people should avoid them... thoughts? I'm thinking of maybe installing a central air filter (in the ventilation system) - is that a good idea? --3kdocnmjduif (talk) 12:52, 2 October 2010 (UTC)
Don't forget to read indoor air quality and vehicle exhaust. ~AH1(TCU) 15:35, 2 October 2010 (UTC)


whats Softwood plywood —Preceding unsigned comment added by Kj650 (talkcontribs) 04:22, 2 October 2010 (UTC)

Do the articles Softwood and Plywood answer your question? --Jayron32 04:24, 2 October 2010 (UTC)

no —Preceding unsigned comment added by Kj650 (talkcontribs) 06:59, 2 October 2010 (UTC)

Softwood plywood is usually made either of Douglas fir or spruce, pine and fir (collectively known as spruce-pine-fir or SPF), and is typically used for construction and industrial purposes. Richard Avery (talk) 07:22, 2 October 2010 (UTC)

It is also cheap and so is usefully for formwork were it will be discarded afterwords or for use were it wont be seen -in other words, it lacks long term durability and it usually has a poor outward finish.--Aspro (talk) 09:13, 2 October 2010 (UTC)

breast question[edit]

what is the calorific value of human breast milk? —Preceding unsigned comment added by (talk) 07:15, 2 October 2010 (UTC)

They say it's 70 calories per 100 ml. This article on what to eat when breastfeeding also has interesting numbers. Our article on breast milk gives no numbers, sadly. Happy? Cheers, Ouro (blah blah) 08:04, 2 October 2010 (UTC)

Why does my head click if I turn it too fast?[edit]

This is NOT a medical question, it's not serious, I was just wondering, why does my head click if I turn it too fast? It feels like two sections of my skull sliding over each other. Is it my spine? Just puzzled, that's all.--Editor510 drop us a line, mate 09:29, 2 October 2010 (UTC)

We have an article on Neck creaking; it could be that. WikiDao(talk) 09:34, 2 October 2010 (UTC)
No, I can actually feel it, it's not a sound, and it shoots right through the back of my head, near the cranium.--Editor510 drop us a line, mate 10:36, 2 October 2010 (UTC)
The link within that article to Cracking joints is what you want. If it's not, then see a doctor. Vimescarrot (talk) 10:38, 2 October 2010 (UTC)
It's nothing serious, I think it's just to do with nerves.--Editor510 drop us a line, mate 07:18, 3 October 2010 (UTC)
I recently read up on globus pharyngis as it sounds remotely similar to your condition, but this is not an attempt to diagnose, and if you actually have that condition then you should consult a doctor. ~AH1(TCU) 15:34, 2 October 2010 (UTC)
No, I think it's just something to do with the spine and skull, perhaps due to stiffness. Definitely nothing deadly or dangerous. Thank you anyway.--Editor510 drop us a line, mate 07:41, 3 October 2010 (UTC)

50 F/500 - speaker[edit]

i have a speaker with writings
                     16 ohm

i understand that 16 ohm is the resistance of the speaker. but what is this "50F/500" .

one more thing -- if i want to produce a high frequency sound through a speaker, had it to meet some conditions. is so please specify what Thanx--Myownid420 (talk) 09:43, 2 October 2010 (UTC)
You may want to take a read of Loudspeaker. In particular, it is almost definitely the case that 16 ohm is the Electrical impedance not simply the 'resistance' of the speaker. Nil Einne (talk) 10:05, 2 October 2010 (UTC)
You don't specify how high a frequency you wish to produce, but you might like to read about tweeters. Dbfirs 15:42, 2 October 2010 (UTC)

How\why tastes enhance eachother or cancel eachother out?[edit]

What is it called when two flavors together seem to enhance eachother or cancel eachother out, and how does this happen? In other words, we can break down the sense of taste into a variety of different receptors, but a flavor is more than just a combination of sweet, salty, sour, bitter, and umami, right? (talk) 16:03, 2 October 2010 (UTC)

well, it's not simply a matter of taste. for instance, I know that an old chef's trick is to use salt and garlic together, because the salt overwhelms the taste buds in the mouth and so enhances the aroma of the garlic. scent is a more subtle sense, capable of distinguishing far more nuances than the simple five tastes, and so you can't discount the interaction between them. --Ludwigs2 17:11, 2 October 2010 (UTC)
We don't really perceive those basic tastes separately, though. Kind of if you take a red light and add green light to it you get yellow light. Yellow doesn't look red at all.
(We've only got 'three basic colors, but that doesn't stop us from seeing roughly a zillion colors.) APL (talk) 20:30, 2 October 2010 (UTC)
Not quite the same. Taste is synergistic, and chemically so. MSG + garlic + cilantro ==> a very synergistic mix. Sweet inhibits bitter. John Riemann Soong (talk) 08:35, 3 October 2010 (UTC)

Electrical energy[edit]

can we create electrical energy by applying electromagnetic induction in planes?? —Preceding unsigned comment added by (talk) 16:14, 2 October 2010 (UTC)

I added a title to this question to separate it from the previous section. Vimescarrot (talk) 16:59, 2 October 2010 (UTC)
Assuming you mean airplanes rather than geometric planes, we can certainly transform energy, like from air flow to electrical power by a little aux power generator driven by airflow or by rotation of the engine to electricity from a generator. Perhaps some form of waste energy could be changed into electricity by electromagnetic induction. A transformer in an airplane also changes one voltage and current level to another. I do not think that any energy will be "created" from nothing just by some electromagnetic doodad being placed on an airplane. For instance, if a coil of wire on an airplane cut through the Earth's magnetic field, a voltage and current could be produced in the coil, but there would be a mechanical force slowing down the plane a bit as a result. Edison (talk) 19:19, 2 October 2010 (UTC)

Mushrooms in BC[edit]

Are there any deadly poisonous mushrooms in British Columbia, especially in the Lower Mainland? And this is not a medical question, and I am not about to eat a mushroom. --The High Fin Sperm Whale 18:10, 2 October 2010 (UTC)

You are likely to find both amanita muscaria and amanita pantherina, according to this - no doubt there are others. Mikenorton (talk) 19:12, 2 October 2010 (UTC)
Thanks, I have seen Fly agarics, but is there anything that one bite of it can be deadly? --The High Fin Sperm Whale 19:18, 2 October 2010 (UTC)
I don't know about one bite but the death cap, amanita phalloides, has caused at least one fatality in BC [2] and that only needs half a mushroom. Mikenorton (talk) 19:40, 2 October 2010 (UTC)
One bite of that could kill you (or make you wish you were dead). Easy to stupidly do accidentally, and easy to add to a murder mystery plot. --jpgordon::==( o ) 20:27, 2 October 2010 (UTC)
Before, I thought I shouldn't eat mushrooms I find. Now, I know not to eat mushrooms I find. Thanks guys! --The High Fin Sperm Whale 20:58, 2 October 2010 (UTC)
Destroying angels probably occur in the Lower Mainland. Pfly (talk) 22:34, 2 October 2010 (UTC)

Crystaline sucrose[edit]

How many "waters of crystalization" are there in crystaline sucrose71.2.132.222 (talk) 19:30, 2 October 2010 (UTC)

I don't think that there is any water of crystallization. In case you didn't know, water of crystallization is water molecules that are attached to the crystal structure of the molecule. Have a nice one, --Chemicalinterest (talk) 20:36, 2 October 2010 (UTC)

Disease Labs[edit]

What's the name of that place in the US where they keep lots and lots of different types of diseases? There are three or four levels, with increasing levels of security, depending on how dangerous they are. Fly by Night (talk) 20:11, 2 October 2010 (UTC)

Centers for Disease Control and Prevention? Mikenorton (talk) 20:16, 2 October 2010 (UTC)
Biosafety level is all about the various levels and a listing of the few places that have the highest-level facilities. Careful to distinguish "level" (amount) of safety from "level" (floor) of a building (question seems to mix the two...unclear if there is really a single repository of all major pathogens). DMacks (talk) 20:21, 2 October 2010 (UTC)
There are multiple ones around the U.S. The most obvious ones are the CDC in Atlanta and USAMRIID in Maryland. Shadowjams (talk) 20:37, 2 October 2010 (UTC)
Wikipedia list of Level 3 and 4 facilities. Shadowjams (talk) 20:41, 2 October 2010 (UTC)
[[Maybe Plum Island? Rmhermen (talk) 21:01, 2 October 2010 (UTC)
from what I hear, Plum Island has been deactivated as a disease research location. --Ludwigs2 03:37, 3 October 2010 (UTC)

3D technology for teaching cats and dogs[edit]

I remeber seeing somewhere that cats and dogs don't see TV the same as we do, which is shame because they could learn so much and we could even help them evolve that way, but isn't there some way TVs could be adapted for dogs and cats, even something like a D&C-3D technology. Not to sound like a prophet but I bet plenty of people would subscribe to that channel for their pets. The African Grey can learn nearly a thousand word vocabulary, and I'm sure a 3D verson of some kids learning show would go a long way to educate them. Yes I just said educate a bird, not a bachelors degree or anything like that but, elementary school graduate maybe. GabrielVelasquez (talk) 20:51, 2 October 2010 (UTC)
Okay not quite a thousand, this article says "950." GabrielVelasquez (talk) 21:02, 2 October 2010 (UTC)
"They have the capacity to have a vocabulary of over 2000 words." - GabrielVelasquez (talk) 21:05, 2 October 2010 (UTC)
...isn't there some way TVs could be adapted for dogs and cats? GabrielVelasquez (talk) 23:02, 2 October 2010 (UTC)

See animal language. The level of abstraction displayed by even a kindergardener's language usage is probably utterly unobtainable by any other animal. I remember reading somewhere the insightful comment that the difference between having a specific signal for "watch out: there's a snake" and being able to talk about snakes ("thank goodness there's no snake here", or "remember that snake?", or "do you suppose snakes are as dangerous as tigers?") is huge. Human language and learning are both all about abstraction. The African Grey parrot is really smart as animals go, but language is not just about accumulating a bunch of definitions. Paul (Stansifer) 04:39, 3 October 2010 (UTC)

Albert Einstein[edit]

I wonder who is Albert Einstein's notable student? —Preceding unsigned comment added by (talk) 20:59, 2 October 2010 (UTC)

Give up! Who is he?--Aspro (talk) 21:37, 2 October 2010 (UTC)
I don't know? That's why i'm asking. ANYONE knows? Albert Einstein doesn't have any student? (talk) 21:48, 2 October 2010 (UTC)
Perhaps Leó Szilárd - I'm not sure that Einstein had many students in the normal understanding of the term. Mikenorton (talk) 21:55, 2 October 2010 (UTC)

Vintage sperm doesn't produce vintage offspring?[edit]

My understanding is that somatic cells accumulate many mutations over our lifetime, contributing to ageing. If this is the case, then shouldn't germ cells also accumulate the same mutations? They're not more protected from chemical and electromagnetic mutagens than any other cells, surely? Are there special restorative process active in these cells that aren't active in somatic cells? If the germ cells accumulated mutations at the same rate as somatic cells, successive generations would be expected to leave begin increasingly aged offspring. I don't get it. -- (talk) 21:34, 2 October 2010 (UTC)

I'm not sure so I'll speculate, and anyone else can feel free to shoot down the idea. Whilst meitotic cells aren't any more protected against damage than mitotic cells, wouldn't the fitter, less damaged cells be more likely to reach the ovum than damaged ones? In any case, sperm are constantly made in the testes, so it's not like these cells have to cope with prolonged exposure to radiation or chemicals. Also, 'aged' cells are damaged physically but often the DNA may remain mostly in it's original form. As long as the genes for mechanisms of DNA repair remain unaffected and crucial genes of function aren't damaged, why would aging accumulate in successive generations? Regards, --—Cyclonenim | Chat  21:40, 2 October 2010 (UTC)
Aging is a little more complicated than somatic cells acquiring mutations. That is probably part of it, but there are also a number of other biological components, including telomere shortening and senescence of somatic stem cells. The fact is that new mutations happen in EVERY germ cell -- we all have a thousands of new mutations (see mutation rate). Of course, most of those mutations have absolutely no repercussions, but every so often a mutation happens in a critical gene and causes a disorder. That being said, see paternal age effect for discussion of fertility, pregnancy/birth complications, and some medical conditions associated with advanced paternal age. --- Medical geneticist (talk) 22:46, 2 October 2010 (UTC)
We don't seem to have an article on germ-cell segregation, which happens in the embryo and means that the cells that go on to produce your offspring will reproduce themselves far less regularly than the cells that keep your body alive. Physchim62 (talk) 23:21, 2 October 2010 (UTC)
I agree with Medical geneticist, and would add another consideration: the accumulation of mutations in the germ line is called "evolution". Sure, some will be deleterious, and if sufficiently so may affect reproduction (and thus will be lost by the population). Others will contribute to population diversification, which provides distinct individuals that will have various levels of fitness under various selective forces. -- Scray (talk) 03:49, 3 October 2010 (UTC)
See [3] for a discussion of age and mutation rate. Bear in mind that sperm has its own private, very strong process of natural selection on the way to the egg, which probably weeds out a good variety of harmful mutations (and probably misses quite a few as well). The way to weed out the mutations that get through, ultimately, is by death and the natural selection of new offspring; which suggests that if humanity succeeds in extending its lifespan, eventually nature will push back indeed by mutating the offspring beyond the capacity of natural selection to remove. Of course, natural selection has already been taking some time off of late, which should create the same type of pressure anyway. But if you learn all the SNPs in the human genome, and can recognize any new mutation, and can fix it, all that becomes moot. Wnt (talk) 00:14, 4 October 2010 (UTC)

Gliese 581 g comparisons that are fair[edit]

Consensus is the RD isn't the right place for asking for help with article disputes Nil Einne (talk) 02:08, 3 October 2010 (UTC)
The following discussion has been closed. Please do not modify it.

I've been told the equilibrium temperature of Mars is 218 K (-55°C) and
that the equilibrium temperature of Gliese 581 g is 224 K (-49°C), and
at the same time told that it isn't fair to compare them
even though one is next to the Earth and the other is not next to the Earth.
Considering the primary source authors, AKA the discovery team
went as far as to compare temperatures of this planet with that of Earth which is not tidally locked either,
is this a fair comparison or fair reason to not make the comparison with Mars??
GabrielVelasquez (talk) 21:36, 2 October 2010 (UTC)

Like Earth's moon, Gliese 581 g is tidally locked, one side is always facing the star Gliese 581 and one is always facing away. One side of the planet will be considerably hotter than the other. That's why temperature comparisons are invalid. --- cymru lass (hit me up)(background check) 21:49, 2 October 2010 (UTC)
It's not really appropriate to use the Reference Desks to canvas for support for controversial additions to an article. APL (talk) 23:58, 2 October 2010 (UTC)
  • It's already done, I'm not looking for support, I'm looking for a better defense from vandals, different perspectives. I'm surprised at you, that's the attitude of a POV pusher, seeking a balance of perspectives is encyclopedic. shame, shame. GabrielVelasquez (talk) 00:03, 3 October 2010 (UTC)
Please ignore GabrielVelasquez and close this thread. He has been using sockpuppets onGliese 581 g and harassing users with personal attacks and edit warring. This is the same behavior that led to his previous blocking and retirement and is about to end for good. Viriditas (talk) 00:07, 3 October 2010 (UTC)
There are places on Wikipedia that you can go with disputes and POV concerns. The Reference Desk is not one of them. APL (talk) 01:35, 3 October 2010 (UTC)

Black holes?[edit]

After reading the article Black hole, I'm still a little mystified. Are there any actual confirmed black holes, or are they all candidates? If the latter is true, then I'm guessing List of black hole candidates and List of black holes need to be merged... --- cymru lass (hit me up)(background check) 21:44, 2 October 2010 (UTC)

There are confirmed candidates, i.e. matching the criteria we assume to relate to a black hole (see here. I'm not a physicist, so I can't explain why this evidence doesn't prove they exist 100%, but apparently it doesn't. I'll let someone else cover that. With respect to merging, probably still a good idea. Regards, --—Cyclonenim | Chat  22:24, 2 October 2010 (UTC)
Okie doke. Thanks!
"...why the evidence doesn't prove why they exist 100%..." Science requires that when additional (valid) data contradicts a theory (rather a theory's predictions) that the theory be abandoned or modified (or reinterpreted). In Science, unlike religion, there can be no 100% proof, by definition (at least until all possible experiments have been done).
There are several reasons why we can not confirm the existence of black holes. We can not directly observe them (they give off no radiation). (a claim was made in September 2010 that Hawking Radiation has been observed - but HR is black body radiation and is characteristic of any mass at a specific temperature and not exclusive to bhs). They are invariably obscured by a halo of surrounding (orbiting) material and material in between us and the central object. At astronomical distances their observed effects are principally due to gravity, again not unique to bhs. Finally, there are significant inadequacies in applying general relativity to quantum physics and the collapse of matter/space into a bh is inherently quantum in nature. While they are the most likely explanation for our observations, until we have developed a better theoretical framework that can explain the progression from normal matter to bh singularities (for instance states of matter consisting of degenerate neutrons or quarks are posited to exist but are not well understood - see Strange matter in wikipedia) we should not be mataphysically certain that what we are "observing" is fully collapsed space-time. (although many scientists are sure it does exist and we are observing it, more conservative scientists will only admit that what we observed is consistent with what (little) we understand about bhs and quantum relativity) (talk) 18:08, 3 October 2010 (UTC)
I edited your comment, to make it visible. Putting a space in front of a comment turns it into a boxed comment. --Chemicalinterest (talk) 18:24, 3 October 2010 (UTC)


Hello, I recently went on a mushroom hunting expedition and found several mushrooms that I don't know the names of. Can someone please help me identify them? Thanks, --The High Fin Sperm Whale 22:20, 2 October 2010 (UTC)

Number 2 is Geastraceae, also known as an earthstar mushroom. Looie496 (talk) 23:08, 2 October 2010 (UTC)

Geastrum saccatum perhaps? --The High Fin Sperm Whale 23:45, 2 October 2010 (UTC)
And I think that the first three are Lepiota rachodes. --The High Fin Sperm Whale 00:48, 3 October 2010 (UTC)
We just had a featured article on an earthstar, so now I recognize #2 as something from Geastraceae. But I won't pretend to know which. Wnt (talk) 17:10, 5 October 2010 (UTC)

Phonophore - communication device[edit]

Just reading Baden-Powell's report on the Siege of Mafeking, and in it he refers to devices called phonophores. They are in his Communications section, under the sub-heading of Signalling. The sentence reads in full "Phonophores were also made and used on the armoured train, attached to ordinary telephone lines". Now, Chambers 20th Century Dictionary, 1983 edition, page 962, says of phonophore "a sound-conducting apparatus, of various kinds: a device for telephoning and telegraphing simultaneously by the same wire". Which is all very well, but does anyone know anything more about them (how they work etc), or even better about the ones B-P had made? DuncanHill (talk) 22:56, 2 October 2010 (UTC)

Assuming this is the communication device on railway trains, it looks like one of those very old telephones - a wooden box with a ceramic funnel for talking into and listening. I have seen them on tours of old trains, but they weren't called "phonophores". They were called "phones". Perhaps phonophore is the proper name for them. They were needed for immediate communication between the caboose and the engine. -- kainaw 23:18, 2 October 2010 (UTC)
(ec) Also known as a 'condenser telephone' apparently, which was invented by Edison, and so perhaps this is just a portable telephone apparatus attached to a telegraph line to allow voice communication, see [4]? Mikenorton (talk) 23:21, 2 October 2010 (UTC)
Thanks, the portable apparatus sounds likely in the context. DuncanHill (talk) 23:39, 2 October 2010 (UTC)
The first edition of the Oxford English Dictionary gives this definition for "phonopore": "Name of an apparatus by means of which electrical impulses produced by induction, as in a telephone, may be used to transmit messages along a telegraph wire, without interfering with the current by which ordinary messages are transmitted."
I don't know how they made them, but the physical principle is quite simple: telegraph messages were sent in Morse code, that is at a rate of no more than a few hertz; speech signals, which have a higher frequency, can be sent along the same line without interference, and the electronic circuitry to sort out one message from the other is very simple, high-school level in most countries. Physchim62 (talk) 00:14, 3 October 2010 (UTC)
Do you have an exact reference to Baden-Powell's discussion of phonophore? Why did he need to signal between two nearby telegraph systems lacking a direct connection? [5] indicates a "phonohore" was similar to Thomas Edison's "grasshopper" earlier telegraph of the 1880's which used a high frequency inductively (or capacitively) coupled signal to connect a transmitting circuit to a receiving circuit without a direct metallic connection, in other words, wireless telegraphy. The regular telegraph was pure DC. The phonophore in the reference, invented by Mr. C. Langdon-Davies of London, was a tuned high frequency (though perhaps audible and lower than radio frequency) AC telegraph transmission. It could transmit speech [6] like the pre-radio system of Nathan Stubblefield, but such a usage would have to remove the tuned transmit and receive frequencies and use simple baseband audio. Short range and inefficient compared to radio. Edison (talk) 00:28, 4 October 2010 (UTC)
I found [7]]. Why were the opponents of Powell too lazy to cut the telegraph wires at multiple points, so that his wireless inductive/capacitive connection to them would have been rendered useless? Why was he too lazy to stop and connect a telegraph key to the telegraph line? How could he travel about in an "armored train" when ten minutes work would have made the tracks unusable?Why didn't the opponents just pull a couple of spikes and disconnect the rails? Was everyone in that war daft? A great mystery. Edison (talk) 00:39, 4 October 2010 (UTC)
It wasn't a siege in the sense of a castle surrounded on all sides by the enemy. The force available to the Boers wasn't sufficient to completely invest the town, and B-P had mobile forces both in the town and to the north able to sally forth and engage with any Boers who had left their prepared positions. I don't think he was "too lazy to stop and connect a telegraph key" (lazy is one word you'll never hear directed at B-P), if a phonophore gave him a ready voice link to the soldiers on the armoured train he'd have leapt at the idea. DuncanHill (talk) 09:21, 4 October 2010 (UTC)
The sentence I quoted is from the Report of the Siege of Mafeking, by Major-General Baden-Powell, October 1899 - May 1900, submitted to Lord Roberts (Commanding-in-Chief), and reprinted in The Siege Collection, Uncovered Editions, The Stationery Office, London, 2001, ISBN 0117024643. It appears on page 241 of this edition. DuncanHill (talk) 09:31, 4 October 2010 (UTC)
Re Edison's question about the vulnerablity of Armoured trains; they were much used in the Second Boer War[8], where the only way to cover the huge distances involved was on horseback or by rail. Apparently it is not easy for a man on a horse to destroy a rail track. They were invented in the American Civil War and last used in World War II[9][10]. We Brits had a very small armoured train that ran on the Romney, Hythe and Dymchurch Railway in 1940[11]. Alansplodge (talk) 18:52, 4 October 2010 (UTC)
A simple Google search gives "Phonophore (jō'nó-fōr), is a device of Langdon Davies of London, England, for transmitting electric signals through circuits which are not closed. Messages have been sent over wires open at both ends, in circumstances which would render ordinary telegraphing impossible. The same wire has been used at once for ordinary telegraphing and for the transmission of phonophore signals. When, the resistance having been greatly increased, the ordinary signals ceased, those of the phonophore continued as distinct as before. The transmitter is fitted with a vibrating reed at one end and the receiver with a stretched steel band at the other, which can be tuned to the same note."
If one length of telegraph wire were cut, at each end of a section, no signal could have propagated beyond the cut section. It was not magic. It was just an audio signal coupled to a telegraph circuit. A party of men on horseback carrying very basic tools like prybars could have pulled the spikes and lifted a section of rail in 10 minutes, as evidenced from the American Civil War or 150 years of railroad history, or from my personal experience working on a railroad. If they had any explosives, it would have been far quicker to prevent the travel of the "armored train." The whole history makes no sense. Did the Boers and the British lack the ability to climb telegraph poles? Did the Boers lack the physical strength to pull a few spikes or to chop down telegraph poles and cut wires? Did their commanders lack knowledge of how railroads and telegraphy worked? Edison (talk) 02:06, 5 October 2010 (UTC)
You see the enemy riding out towards your telegraph or railway line and so you send someone out to intercept or harass them. Someone pulls out a spike? You hammer it back in. Neither side at Mafeking had great numbers of men, the lines were permeable, both had spies amongst the native population, and the country provided little cover. Do read the report if you get the chance, it's fascinating stuff. DuncanHill (talk) 00:34, 7 October 2010 (UTC)
A little more searching found which gives a picture of an armoured train and says "Armoured trains were officially recognised as moving telegraph offices, and equipped with field sounders, vibrators, phonophores and telephones; and whenever trains stopped away from a regular office, which they did nearly every night, they were never out of communication with the neighbouring stations and blockhouses. When several trains patrolled one section, it was found advisable especially at night, that they should all halt at fixed intervals and connect up with the telegraph wires to receive instructions and news."
This Google search finds seven enteries for Langdon Davies' phonophone: Where do I send my bill? (talk) 20:50, 4 October 2010 (UTC)
Many thanks, unfortunately we are not allowed to let anyone know where Wikipedia is based, so you won't be able to send a bill. DuncanHill (talk) 23:46, 4 October 2010 (UTC)