Wikipedia:Reference desk/Archives/Science/2014 August 22

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August 22

MO diagrams and term symbols

Regarding multiplicity, does the orbital momentum of unpaired electrons in non-degenerate orbitals cancel? For instance, in the hypothetical d⁸ excited complex, does the orbital momentum of the lone electron in the e_g orbital cancel that of the electron in the t_2g (is it a singlet or a triplet)?

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Plasmic Physics (talk) 12:12, 22 August 2014 (UTC)

Multiplicity (chemistry) is solely about the number of unpaired electrons, not about their energy levels. The change (or lack of change) in total spin is one of the selection rules for electronic transitions. See Fluorescence#Physical principles for more discussion. DMacks (talk) 20:15, 22 August 2014 (UTC)

So, singlet then? Plasmic Physics (talk) 21:17, 22 August 2014 (UTC)

It's analogous to the example given in Intersystem crossing, yes. DMacks (talk) 03:03, 24 August 2014 (UTC)

Ho do I find the term symbol for a triatomic molecular MO diagram? Plasmic Physics (talk) 22:36, 23 August 2014 (UTC)

Molecular term symbol is the main article on the topic. It's horribly over-specific for a single simple type of molecule. Term symbol, although it's focused on single atoms, does talk through the basic analysis that's relevant in all cases (which orbitals to consider, what symmetry terms, etc.). DMacks (talk) 03:53, 24 August 2014 (UTC)

Thanks, I had a look at it. I don't understand it though. What makes a particular electron configuration symmetric or not. For instance, why is...

σ_s-p  ↑    ↑  

σ_s-p     ↑↓

n_s        ↑↓

...antisymmetric, whereas...

σ_s-p  ↑↓      

σ_s-p     ↑↓

n_s        ↑↓

... is symmetric (both states have C_2v symmetry)? Plasmic Physics (talk) 02:55, 25 August 2014 (UTC)

Solid state flight

Is it possible to propel a vehicle that flies in normal Earth atmosphere by some means that does not involve macroscopically moving parts?

• There is a very crude device the Crookes radiometer that does so weakly in a thin atmosphere, but I am thinking there ought to be some way to greatly improve its power. I understand you can't have a Maxwell's demon, but could you have a flat sheet of metal that somehow acts on air molecules that bump up against it so that those moving straight out bounce elastically, those that bounce to the left are greatly accelerated, and those that bounce to the right lose most of their energy, using only a catalytic amount of energy equivalent to not much more than those air molecules will generate when they eventually smack into others and reach equilibrium?

• How about an electrostatic system that charges tiny regions of air along a flat plate, then pushes on them with carefully patterned charge on the plate that responds adaptively to the measured external charge and pressure patterns?

• Or a gel that holds large amounts of dissolved air, releasing it on one side and absorbing it on the other to provide lift?

Etcetera. Could anything like this work? (But please let's exclude space-based solutions like photon drives, magnetic sails, etc., and any ordinary sort of hot air balloon) Wnt (talk) 12:41, 22 August 2014 (UTC)

Ramjets and solid fuel rockets have no moving parts - at least, on paper. In practice, real aircraft and rockets have electric pumps, hydraulic valves, starter devices, control surfaces and all sorts of peripheral moving parts. Nimur (talk) 14:15, 22 August 2014 (UTC)

Those without an irrational aversion to nuclear-powered aircraft may wish to consider nuclear ramjets such as Project Pluto. -- ToE 14:31, 22 August 2014 (UTC)

That prototype looks suspiciously like the rocket used in Flesh Gordon. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:30, 22 August 2014 (UTC)

Well, you need an upward force to counteract gravity...so what exerts a force?

• Bouyancy - so you have to displace the air with something lighter - which basically means balloons. Hot air, hydrogen, helium, methane...a vacuum (which is tougher than you'd think!).
• Action/Reaction - Newton's third law lets us push something downwards and have our aircraft go upwards as a result. The 'something' can be the air - or something that's ejected from the aircraft itself.
  • If it's the air itself, then you're thinking about jets and wings. But to use a wing, you need forward speed - which means either needing a rotor (like a helicopter or a hovercraft) - which fails the "no moving parts" rule - or something that uses a wing, needing a horizontal thrust instead. Generating horizontal thrust without moving parts is more or less the same problem as generating it vertically...although a glider operates without an onboard power source. Jets are definitely possible. RamJets...or pulse jets...or scramjets. The only moving parts are the fuel itself.
  • If it's something carried aboard the aircraft, then you have a rocket - or something very like one (eg that crazy spacecraft that drops atom bombs behind itself and then explodes them!) Firework rockets have no moving parts...so that could work...so do water rockets and such like. Of course if you count movement of the fuel as a "moving part" - then rockets are out of the question.
  • You could imagine an aircraft with a massive laser beam aiming downwards that would gain lift by photon pressure! (Well, you could *imagine* it...I don't think you could actually make it work!)
• Electric/magnetic forces - So we can think of a linear-induction motor powering a levitating train. Those can certainly be built with no moving parts. Trouble is that the magnetic force decreases as the square of the distance - so flying more than a few inches above the ground will be difficult!
• Forces exerted by something fired up from the ground, rather than down from the aircraft. So you could imagine a ground vehicle or some kind of a track or chamber which is generating an enormous column of upward moving air on which the craft balances. Those "indoor sky-diving" facilities use an enormous fan to blow air upwards and turn people into unpowered "aircraft"...if you're prepared to not count the thing that remains on the ground as a part of the aircraft - then there are all manner of ways to think of doing this. In a sense, a long distance glider that uses thermals and slope lift to get where it's going is using power generated elsewhere to do the work. You could imagine a large array of cannons on the ground, firing heavy weights upwards to impact the underside of a heavily armored plate that could be kept in the air that way. Basically, any mass, propelled upwards from the ground, could support the craft...if you allow the moving parts on the ground-based component to not count in the "no moving parts" rule.

I'm sure there are other possibilities.

SteveBaker (talk) 15:55, 22 August 2014 (UTC)

Ionocraft Jim.henderson (talk) 16:06, 22 August 2014 (UTC)

This is the general idea I was picturing: airflow would presumably be right to left. No idea if this could work.

The ionocraft is indeed an interesting lead! [1] I was reaching toward something similar in the second point above, but what surprises me about the hobbyist ionocrafts is that they rely on having single, fixed positive and negative electrodes. I would think that you could pattern the charge on a flight surface so that you would first use a very strong positive and negative voltage and intentional discharge to create little puffs of positive and negative air along its length, then continuously charge ever-changing strips of the surface to be intensely negative just behind the positive puff and vice versa so that they would always be pulling the surface forward relative to the puffs in the air, but without an actual discharge that would cancel the puff out. Wnt (talk) 17:10, 22 August 2014 (UTC)

If you're willing to put in a very large amount of energy, you can do nearly anything! The trick is to make this technology competitive with the costs, safety, and reliability, that can be delivered by more conventional propulsion schemes. Nimur (talk) 17:26, 22 August 2014 (UTC)

Well, the ionocraft article claims the method is very efficient, but doesn't scale. I don't know what would happen if it could scale, and I'm not sure this would really be a way to get there, but I feel as if there ought to be a way... Wnt (talk) 17:52, 22 August 2014 (UTC)

So far all the discussion has been on moving parts involved in lift or thrust or control surfaces. Note that there are many moving parts on aircraft unrelated to these. Wheels and landing gear is one category. Those could be replaced with fixed pontoons, if water landing is an option, or fixed skis, if snow landing is. You could possible land on skis on land, if it was prepared properly, such as spreading snow on it or a suitable substitute. However, I'd guess you need shock absorbers (with moving parts) to go with either skis or pontoons. For small enough unmanned planes, you can also catch them in a net.

If people are to be on the plane, then you need doors, unless the plane flies slow enough and low enough that the wind, noise, and low air pressure and temp aren't a problem. And rigid seats would be painful, but any soft surfaces will move a bit as you sit on them. Seat belts have moving parts, too, as do bathrooms and climate control systems. And, while you could use all touch screens for pilot controls, I doubt if those are as reliable as moving knobs, dials, buttons, etc.

Aside from aircraft, there's also projectiles fired from electromagnetic cannons. And there was an experiment where a metal object was spun up, then launched vertically using powerful ground lasers to push it upward. StuRat (talk) 21:59, 22 August 2014 (UTC)

Hmmm, the "rules" may be a distraction, but to be clear, subtle shifts in control surfaces are acceptable, special features on takeoff and landing are acceptable, ramjet fuel pumps are at best borderline, not firing things at the plane. The image I started with was a parallel-reality dream; I was in a bar with a fellow who was ticked off at a football referee so he tossed something called an "immerfliegende Bar-Dart", I think, which looked up navigational info for the name spoken, navigated its way out the window and a few blocks to the stadium, and proceeded to hone in on the ref's rump. :) Wnt (talk) 05:00, 23 August 2014 (UTC)

It wouldn't necessarily be static but I always wondered if Langmuir probes in a magnetized plasma could be biased electrically to generate a mechanical force. The concept of neutral current when the mass of electrons and ions is orders of magnitude differences seems like it could be exploited. Not sure what non-moving parts you want but any type of wing is motion of air over a asymmetric solid. Another thing that might be more "solid state" would be a wing with different temperatures driven by thermocouple principles. Basically a glider that creates it's own thermals using thermoelectric/thermocouple/heatpipe principles. Not sure on how difficult or practical. . --DHeyward (talk) 03:44, 25 August 2014 (UTC)

The glider would seem to spend a lot of energy making thermals it would immediately leave, so I'm not so sure. I can think of a few other variations: alternately heat a balloon and allow it to cool and extract some forward momentum with a properly set wing; or set up a little chimney ("electric ramjet?") and let the hot air push forward the vehicle by reaction. But they seem awfully inefficient because they allow the energy to be lost straight to heat, then try to salvage back part of it by some inefficient power generation process. Really, we'd want the stored energy to go directly to some sort of mechanical work on the air, just not on a macroscopic scale.

The Langmuir probe, well, I won't claim to understand it fully, and in any case, I'm looking for something in air. But the principles involved (Debye sheath / Bohm sheath?) might be relevant to the idea above. I can think of one case where I think most of us have felt electric charge give rise to wind: a Van de Graaf generator. Because that has a moving belt inside I was never totally sure the small air motions were due to the charge, but I would think so, since you have ions fleeing the central charge. Now the Van de Graaf is round and pushes wind all directions, and the ions get out of the area on the shortest possible route, so I'd think a different design would be more efficient, and the ionoflyer is proof of that much. But the other interesting thing about the Van de Graaf generators is that they can produce little "ball lightnings" which somehow, by magnetic effects I suppose, manage to take up macroscopic amounts of air. I'm thinking the problem with just propelling ions back along the wing is that if they merely move through the other air, without hitting it much, then they cannot deliver much thrust. You want to somehow "gum up" the air and make it have some decent reaction mass, and I wonder if some sheath, ball lightning, or other magnetically based mechanism could do that. I'll add (without any confidence) that there are claims that "Haunebu" had Van de Graaf generators aboard; usually those claims go on to follow a whole long track of crazy, but thinking about it from this perspective I have to wonder if there could be some misunderstood bit of truth in there somewhere. Wnt (talk) 15:48, 25 August 2014 (UTC)

Valveless ramjets are the clear winner there though. Your objection to a moving-parts fuel pump is easily countered by propelling them from a pressurized gas cylinder or a gravity-fed liquid fuel tank. Check out this (no-moving-parts) ramjet powering a go kart at alarming speeds: https://www.youtube.com/watch?v=5U-grFuXZ9U - all you need is a gas cylinder and an appropriately shaped U-shaped tube.

SteveBaker (talk) 15:37, 26 August 2014 (UTC)

That's a valveless pulse jet, apparently; I wouldn't expect a ramjet to take off from a standing start. I'll grant it has no moving parts, though that noisy monstrosity doesn't have the look and feel of what I'd be hoping for. Wnt (talk) 18:38, 26 August 2014 (UTC)

I guess you needed to make your question MUCH more specific if noise and 'look and feel' and all of those other issues are a factor in getting you a good answer. If you're simply using your question as a way to showcase some of your own weird ideas about propulsion and arbitrarily dismissing all of the relatively mundane (but entirely workable) answers that you get - then this is the wrong place to ask it. The fact is that there are any number of practical, no-moving-parts flight systems available that don't require any fanciful technology whatever. SteveBaker (talk) 18:45, 27 August 2014 (UTC)

Using brute force n' ignorance, you might use a stationary, ground-based laser to heat a rocket engine with a cryogenic or liquid propellant - reflect the laser 90 degrees up under the rocket engine... the requirement not to have any macroscopic moving parts could be met simply by making the rocket motor such that the liquid reaction mass would flow by force of gravity down into the rocket nozzle/expansion chamber when a solid valve opened by shape memory effect (say, a martensitic phase transition in a steel "cork" at the top of the expansion chamber causing it to move upward from the chamber and let the reaction mass flow into the chamber when the engine was heated to the right temperature by the laser).

The advantage, of course, is that the laser device itself could be as large as needed, and powered by whatever it needed to be - CoIL, its own dedicated nuclear reactor, MHD plasma chamber... because IT wouldn't be going anywhere. And the cryogenic could be liquid nitrogen, liquid air, LOX, LH2, water... whatever was practical. No moving parts, except those which "moved" by thermal expansion out of the way of the reaction mass. loupgarous (talk) 08:31, 27 August 2014 (UTC)

Prototype lightcraft fly through Earth's atmosphere, using air as reaction mass. The photos I've seen show a single rigid body machined out of an aluminum block -- no moving parts. I don't know if the ground-based laser has any moving parts or not. I'm surprised it hasn't been mentioned already. --DavidCary (talk) 19:04, 27 August 2014 (UTC)

What's wrong with a typical black powder firework rocket? Any solid-fuel rocket works without any moving parts without needing to mess around with lasers and mirrors, shape-memory corks and who-knows-what other complications? SteveBaker (talk) 18:45, 27 August 2014 (UTC)

The history of black powder as a propellant for vehicles (which I took to mean "capable of carrying someone") isn't good. There was (as I recall) ONE attempt to put a man into flight with a black-powder rocket, which ended dismally in the Dardanelles Straits as its sponsor, the daughter of the reigning Grand Caliph, looked on (it was supposed to be a birthday present for her, not so much for the poor sap actually riding the winged rocket).

To more fully answer your question "What's wrong with a typical black powder firework rocket?", black powder combines a low specific thrust with a disconcerting tendency for the entire powder charge allotted as "propellant" to detonate all at once, becoming a "warhead," instead. So, you don't get enough thrust to really push your vehicle along if its payload consists of anything but a bit more black powder confined in a cardboard tube (that "firework rocket" you talk about).

By contrast, the ground-based laser places the energetic part of the vehicle on the ground, saving weight for the part of the vehicle that actually has to fly - which reduces thrust to that required to put the propellant, rocket engine, and payload into the air.

To answer the implied question "I don't know if the ground-based laser has any moving parts or not," lasers are the epitome of solid-state devices. You pump power into a substance which has a crystalline or gaseous structure with electrons that can be excited to high levels, then release light when they snap back to their base levels - this light all being one frequency (because of the work function of the electrons being excited in that substance into which you pump the energy) and capable of being directed in one direction with half-silvered mirrors and other reflective surfaces containing the substance which takes the energy and re-releases it as monochromatic laser light, and you get a "laser beam." (The same trick can be used with different materials to give you a beam of microwave or other radio frequency photons, or a beam of X-rays or gamma radiation.)

The reason you use a laser at all is that it can be "tuned" by the choice of the material into which you pump the energy to transfer energy very efficiently from the laser device itself to a distant object - in my example, a rocket engine in which the part of the engine that lets the working fluid into the engine to expand and push the vehicle upward can be a piece of metal that changes from a "plug" keeping the working fluid in the propellant tanks to an "orifice" letting the working fluid inside the rocket engine to be vaporized by the laser when it's heated enough.

None of this requires an actual moving part, but if you really wanted to remove all possible sources of failure, what you do is fill the propellant tank just before takeoff and have NOTHING keeping the working fluid out of the rocket engine - just turn the laser on and have it heat the working fluid as it's pouring through the rocket engine. If the working fluid is water and the laser's tuned to, say, the resonant frequency of hydrogen (making it a "maser," rather than a "laser", but the principle's the same) then the water vaporizes to steam, occupying 1600 times its former volume as a liquid and pushing the rocket up at a very fast rate. This gives you a vehicle with no moving parts and capable of moving large payloads very fast. THAT'S why I chose the laser to provide energy to the "no moving parts" vehicle.

One could do the same thing without actually using a working fluid other than air - a small enough laser to fly inside the vehicle, presumably powered by batteries of some sort so that nothing needs to move - could be directed inside a tube, heating air so that it rushes out of the rear of the tube, pushing the vehicle forward (you size the front and rear openings of the tube to assure more air comes out of the back than the front). I wish the poster who mentioned the "prototype lightcraft" had linked to a page describing it more fully, but that seems to be how such a craft would work.

The drawback to a vehicle made out of a solid block of aluminum metal transferring enough energy to any air which enters it to make it fly is that you pretty much wind up heating the whole craft hot enough to make air push it along, so that anyone riding in it gets to sit in a very hot machined block of metal - so the "vehicle" is necessarily an unmanned one whose payload has to tolerate a lot of heat. loupgarous (talk) 23:32, 27 August 2014 (UTC)

@Vfrickey: I looked up the story you mentioned and came up with Lagâri Hasan Çelebi, but though it seems set in about the right place and describes about the same kind of rocket that story does not end as badly as you suggest. Wnt (talk) 18:21, 28 August 2014 (UTC)

The OP asked "Is it possible to propel a vehicle that flies in normal Earth atmosphere by some means that does not involve macroscopically moving parts?" - no mention of the need to carry people, or the need for any specific duration or trajectory of flight. A black powder rocket is clear and simple proof that the answer to the OP's question is "Yes, it's definitely possible". We're done here - we don't need a bunch of crazy complications and things that have never been tried and may or may not work in practice. Black powder rockets most certainly do fly without any moving parts...the answer to the question is demonstrably "Yes" - we're done here. SteveBaker (talk) 15:15, 28 August 2014 (UTC)

Erm, kind of, but I was fishing for crazy things that have rarely been tried. Ionolifters, lightcraft, ramjets, pulse jets, these things are just fun to know about, and that was the point. But with black powder rockets and jets, the fuel does move, which isn't quite the special effect I'd hoped for, and of course why try to think of a straightforward way to do something when you can look for something totally off the wall? :) Wnt (talk) 18:08, 28 August 2014 (UTC)

• note: I recently ran across something like the charge idea above at [2]. Wnt (talk) 16:28, 9 May 2015 (UTC)

What do you think the cushion is made of?

Thx. Ben-Natan (talk) 13:11, 22 August 2014 (UTC)

Waffle fabric? --Jayron32 13:46, 22 August 2014 (UTC)

I ask myself if there is any Leather in it?, Or how high are the chances it's filled with feathers or wool? Ben-Natan (talk) 14:00, 22 August 2014 (UTC)

This is really into speculation territory, but seems harmless. I assume you can't physically examine the object, or then you probably wouldn't need to ask. Anyway, I see no indication of leather. It is possible some old rattan and wicker work might use leather for lashing, but it is not common in my experience, and leather is much more expensive and less durable than other options (synthetics, integral woven wicker, etc.) I suspect the odds of wool or down stuffing to be very low. Cushion indicates a variety of stuffings, but most stuff made in the past ~40 years will have synthetic stuffing or perhaps cotton batting. The simple reason is that synthetics are much cheaper, and last longer, even if they don't feel quite as nice. Wool and feathers can both be allergenic, which is another reason to avoid them. I'd only expect to see wool or feathers in rather expensive furniture, which this does not seem to be (I do like the chair, it just doesn't seem like an expensive model to me :) SemanticMantis (talk) 17:21, 22 August 2014 (UTC)

As long as we're speculating, my first thought, given the cushion's thinness and lack of lumpiness, was foam rubber. Deor (talk) 20:02, 22 August 2014 (UTC)

What is a phone number?

A person can move elsewhere in the same town and take his or her landline phone number along instead of changing it, or even change it to a cell phone number. Or if that person is being harassed, he or she can change landline phone numbers. Or different people in the same house can have different landline phone numbers. I thought I had the answer to this question when I discovered the concept of IP address. But several branches of the same library system and several hotels in the same resort community have the same IP address when I try to edit Wikipedia without signing in. Plus AOL has dynamic IP addresses. And apparently unlike me, most people get their Internet service through the cable company. So there must be something comparable to an IP address that the phone company uses to identify you.— Vchimpanzee • talk • contributions • 18:10, 22 August 2014 (UTC)

Well, this question becomes a lot simpler if you consider common phone systems from e.g. 1980 or so. The reason being, Telephony services and IP phones now underlie even basic "land line" services in many areas, so in some cases there aren't that many distinctions between phone service and internet service. This is especially true for things like businesses, universities, hotels, etc., as it is now often less expensive to use the internet for calls in situations where you want a lot of phones in a relative small spaces. For the historical perspective, see Telephone_exchange, Public_switched_telephone_network, Telephone_numbering_plan, and even Telephone number. So, today the line between "phone number" and internet services is very blurry, but in the past, the phone systems basically worked via phone companies assigning numbers to customers, and using manual or digital switch devices to route calls. The key distinction is that the old phone networks had fixed cables, and calls had to travel down certain paths to be connected. With modern Packet switching (e.g. the TCP/IP that supports the internet), any given packet might take a different path between host and client. (I think I got most of the basics here right, but of course welcome clarification or correction if necessary) SemanticMantis (talk) 19:35, 22 August 2014 (UTC)

I guess what I'm trying to accomplish is something like what cops do in movies or TV shows. Thanks for trying.— Vchimpanzee • talk • contributions • 20:31, 22 August 2014 (UTC)

You mean like a call tracing or Telephone tapping or something? Cops do lots of things on tv, not sure what you might be thinking of. If you're interested in the kinds of shenanigans people can get up to with phones, you might be interested in phreaking. Again, it was a lot different in the past, I don't think whistling into the phone will get you free calls these days :) SemanticMantis (talk) 20:42, 22 August 2014 (UTC)

• For cell phones, each phone has a unique identification key entered on its SIM card, which the phone company uses to identify that phone and look up its subscriber information (including phone number) in a database. For landline phones I don't think there is any such universal system -- each phone company is allowed to implement the mapping from phone number to physical signal route in any way it wants to. Looie496 (talk) 21:12, 22 August 2014 (UTC)

As mentioned below, for landline phones, the mapping is all in the wiring. The copper wire is the physical signal route. Robert McClenon (talk) 21:42, 22 August 2014 (UTC)

To quibble for the sake of it, the IMEI is stored on the phone itself. The unique number on the SIM is the IMSI. Tevildo (talk) 21:22, 22 August 2014 (UTC)

No, there doesn't have to be anything unique in your landline phone for the phone company to identify it or you. (Some of the above answers were unique to cell phones.) Your landline phone or phones are the only phones that are at your end of a wire connection. You have a dedicated wire connection between the telephone exchange and your house. If you move from one location within the area served by a particular exchange to another location in the same exchange, the wire to your new location is connected to the switch connection for that number. ("Exchange", in 'telephone North America', is the NNN part of the 1-NPA-NNN-XXXX that is your telephone number.) That is also why you can use multiple handsets in your house without involving the phone company (assuming that you don't put too many handsets on, and so exceed the ringing impedance). There is nothing in a landline phone that identifies it to the phone company. It is the wiring that is unique. Robert McClenon (talk) 21:39, 22 August 2014 (UTC)

As former Bell employee from a family of Bell employees who manually wrote orders in code providing service, changing and moving numbers, and switching them between companies, I can confirm McClenon's answer is correct for land lines. μηδείς (talk) 01:45, 23 August 2014 (UTC)

By the way, what is shown on police procedural TV shows, getting a list of calls to and from the victim, is done using telephone metadata, consisting of records of calls. There is one metadata record written for every call that is attempted (whether or not it was completed), showing, among other things, the calling number, the called number, the status of the call (no answer, busy, completed), the length of the call, et cetera. The phone company collects the metadata for various purposes of its own, such as long distance billing, capacity planning, maintenance. It is also secondarily used by the police and for other purposes (e.g., formerly, by NSA acting as the secret police). The metadata is essentially the same for landline phones and for cell phones. Robert McClenon (talk) 21:39, 22 August 2014 (UTC)

Telephone numbers started off as Plain Old Telephone service or POTS. Literally the number eventually desc a pair of wires (a 110 punch down is very old). As computer and electronics progressed, only the last mile remained unchanged. Terms like T1 were based on the number of twisted pairs (24 for T1 if I recall and a T3 was 3 T1 bundles). Gradually, the phone system migrated from the physical layer description to different levels of abstraction but as long as it ended at a single pair, it worked. TCP/IP I believe is about 7 levels of abstraction from the physical wire. A telephone number today is simply a backward compatible description of a what was a much more physical model of switches and exchanges that described exactly where a pair of wires went. Note that two-wire POTS still works though it will be converted at the exchange to a more modern form. Old modems and Fax machines still have the POTs Data access arrangement and Tip and ring functionality and wire designation. There is a limit of phones that can exist on the tip/Ring pair and phones came with a Ring equivalency number. Equipment for phones was (and is regulated to allow tracing and pen registers. It certainly is possible to put equipment on the subscriber side, it's much more discrete to monitor at the switch. Also, with digital landline equiment, intercepting at the switch level gives much more information about the call. Cell phones only use their hard-coded network ID to request temporary ones which makes it more difficult. In the U.S., I believe latest implementations encrypt the temporary key so it requires the assignment log at the tower switch to know the assignment so it's not available as a simple radio intercept (and even before encryption the requests for new temps are infrequent). There are specific law enforcement tools that can be used in close proximity to the physical phone (i.e. cell tower range) to access and monitor calls under certain conditions. This is a requirement mandated under the spectrum leasing by the FCC. There are other tools that are available for longer term/wider area access. All of these requests, I believe, are funneled through a single federal LE agency to the carriers or other providers. --DHeyward (talk) 04:59, 25 August 2014 (UTC)

I think that, a phone number always is a (mathematically) combination of electronically binary numbers which set can be electromagnetically or electronically. Are you interested in the logic of a phone number?--Alex Sazonov (talk) 11:52, 29 August 2014 (UTC)

Using nukes to create graphene

Say you take a cylinder of carbon. Put two shaped nuclear charges on both ends of the cylinder and detonate them. Would this create graphene? Malamockq (talk) 23:51, 22 August 2014 (UTC)

If it did, it would also spread it over a wide area, making the experiment rather pointless. And which form of carbon are you proposing to start with? AndyTheGrump (talk) 00:16, 23 August 2014 (UTC)

What do you mean spread it over a wide area? I don't know what form of carbon. Whatever might produce graphene I suppose. Malamockq (talk) 01:21, 23 August 2014 (UTC)

Is the point to ignite wildefires, then collect the graphene from the soot? μηδείς (talk) 01:39, 23 August 2014 (UTC)

I was thinking it would be more prudent to detonate it underground. Malamockq (talk) 03:42, 23 August 2014 (UTC)

I don't believe high pressures are needed to produce graphene. It's basically just a very thin sheet of graphite. At least according to Superman comics, what you describe might end up producing diamond. Rojomoke (talk) 05:07, 23 August 2014 (UTC)

♦ 84.209.89.214 (talk) 12:05, 23 August 2014 (UTC)

Right, this would probably produce diamonds. You don't even need nuclear bombs to do it. It can be done with conventional explosives. If you have a piece of graphite, all you need to make graphene is some adhesive tape. Mr.Z-man 13:38, 25 August 2014 (UTC)

No, you cannot, like putting a grenade in a wax block doesnst produce Honeycombs. Graphen is being grown on structured layers, the bees are rather tiny ones compared ;) Serten (talk) 17:40, 26 August 2014 (UTC) You get soot or Impactites - but no diamonds. A diamond needs a longer time of high pressure to grow. Serten (talk) 17:46, 26 August 2014 (UTC)

At least follow the links. Nanodiamonds are still diamonds. Andre Geim and Konstantin Novoselov got the Nobel prize for getting graphene using sellotape.. Dmcq (talk) 17:51, 26 August 2014 (UTC)

The only actual experimental experience with graphite in the vicinity of nuclear detonations was coating steel spheres suspended from cables near a nuclear device with graphite. The result (after the nuclear detonation) was that instead of steel vaporizing from the body of the spheres, the graphite vaporized instead. No changes in the structure of the graphite itself were reported. This experiment led to the idea of coating the "pusher plate" on the Project Orion nuclear detonation-propelled spacecraft with oil or graphite between nuclear propellant pulses, so that ablation of the plate itself would be prevented or reduced. loupgarous (talk) 07:05, 27 August 2014 (UTC)

Your graphite would simply evaporate from the heat. No graphene results. --Kharon (talk) 00:50, 28 August 2014 (UTC)