Wikipedia:Reference desk/Archives/Science/2017 November 1

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November 1

Gigantic Chinese finger trap

Gigantic Chinese finger trap known as a towing sock

It is a very clever way to grab the end of a cable to thread it through a tube or tunnel. It works like a Chinese finger trap. Is there a general name for this sort of weave or shape or something? The commons cat contains finger traps as well as a traction device using the same shape. It would be nice to have some sort of proper name. Anyone? Anna Frodesiak (talk) 02:06, 1 November 2017 (UTC)

Is it a type of hollow Rope#Braided rope? Anna Frodesiak (talk) 02:22, 1 November 2017 (UTC)

A small version of this tool has been called a rope trap, larger ones are called a wire rope puller or a towing sock. Naturally there is also an article about the original Chinese finger trap. Blooteuth (talk) 02:27, 1 November 2017 (UTC)

Thank you again, my friend. I have therefore just stubbed Towing sock. Now, I will attempt to find a non-spammy ref. Anna Frodesiak (talk) 03:00, 1 November 2017 (UTC)

A cable head is a different device with a similar capability. Nimur (talk) 03:28, 1 November 2017 (UTC)

Similar indeed, Nimur. I wonder how they affix the cable to it. I see pics on the net. I hope that's it. It looks like Captain Hook's arm end without the hook. Is that it? Anna Frodesiak (talk) 03:53, 1 November 2017 (UTC)

I'd like to add to the the article (Towing sock) the fact that there is a loopy thing on the end. It probably has a name but I don't know what it is. Anna Frodesiak (talk) 04:02, 1 November 2017 (UTC)

This is useless for professional application because cables meant for tubes and tunnels are either electric power cables or communication cables, either electrical or fiber. All these cables are absolutely not suited for tension so pulling them over longer distances will damage them because at some point, when you pull for example 100 meters, you have to pull the weight of a 100 meters long cable and the friction on top which accumulates to forces beyond the material capabilities. Its a smart idea as concept but in that application not thought thru to the end, because these cables are in fact surprisingly fragile. Because this is not used anywhere obviously it can not have a common name. --Kharon (talk) 04:25, 1 November 2017 (UTC)

Somehow the electricians here get long runs of cables fed through pre-buried conduit. They might use devices like this for pulling cables with 8000 lbs of force at 6 ft/minute, and associated lube to make it easier and a companion pusher to feed at a rate matched to the puller. They also might use a "pulling sock" for some cases, that sounds like the towing sock. This one (also 8000 lbs at 6 ft/minute...seems like a standard?) says it's for conduit pulls of up to "4 x 500mcm Copper Cables, 800 ft. w/(3) 90 deg. Bends, 3 x 1000mcm Copper Cables, 750 ft. w/(4) 90 deg. Bends, 4 x 750mcm Copper Cables, 1200 ft. w/(2) 90 deg. Bends". That's a lot of cable weight! DMacks (talk) 04:45, 1 November 2017 (UTC)

• And yet I've seen (I used to work for BT) such "finger traps" being used regularly to haul cables, and to haul ashore undersea cables. Large cables are designed to survive the tension of pulling them into place. It's the only way to install them. Andy Dingley (talk) 10:21, 1 November 2017 (UTC)

Hi Kharon. It most certainly is used. The one pictured was in use just last week. The cable in the photo is probably around 10cm in diameter, by the way, and didn't look fragile. Also, it does have a common name because companies sell them with that name. Best wishes and thanks for the input. Anna Frodesiak (talk) 13:11, 1 November 2017 (UTC)

Thinking about this problem I was wondering if sound could help as in the way one can use it to make things creep up a surface. I don't suppose it would help get a cable through a conduit never mind round a corner, but do you know if they have tried using vibrations to reduce the friction whilst pulling cables? Dmcq (talk) 13:23, 1 November 2017 (UTC)

@Anna Frodesiak: I dont doubt its used. Its just no professional tool - not even if you can buy it with a big lable "professional towing sock" on it. I also doubt the claim of Andy Dingley, that these are used on Submarine fiber cables since these are exeptional fragile and expensive. I once read the history of the crazy struggle to lay out the first transatlantic communication cables and today huge constructional efford is made to gently let the cable down from the ship to the seabed, making sure even the cables own weight is not carried by the cable itself, so additional "pulling" at one end seems out of question. --Kharon (talk) 17:25, 1 November 2017 (UTC)

Also from the Schlumberger website, here's an old article: Coiled Tubing Takes Center Stage (1994). Modern technology makes it possible to steer a cable through sharp angles, over miles of borehole. Some of the most sophisticated applications are in the petroleum and natural gas industry; but the same technologies can be used for electrical and data cables, undersea cables, and so on. The ostensibly simple task of threading a "wire" through a "hole" is confounded by the incredible technical challenges of complicated "wires" and complicated "holes." For perspective - a modern drillstring might be several miles long, may be carrying sophisticated scientific instruments like a gamma-ray spectrometer, may be mechanically coupled to a drill bit that can cut through solid rock, and may be subjected to heats and pressures of geological magnitude. Meanwhile, civil engineers and construction crews can thread high-voltage cables and high-capacity water and gas pipelines through boreholes drilled underneath roadways; and can repair and replace existing infrastructure and piplines; all without ever compromising the structural integrity or interfering with the road traffic or structures on the surface. Cables, pipes, and tubes are neat - they're a lot more high-tech than many people realize! Nimur (talk) 17:31, 1 November 2017 (UTC)

(edit conflict)Fibre is quite fragile and is normally blown with compressed air in terrestrial installations. This can't be done for long stretches under the sea, of course, so the conduit or other support has to take the strain. Dbfirs 17:37, 1 November 2017 (UTC)

Yes, you can see an example here from NZ [1]. Nil Einne (talk) 07:01, 2 November 2017 (UTC)

At Submarine communications cable it says about a one inch cable weighing about 2.5 tons a mile, since the Atlantic would be a couple of miles at least at some point going across and the water won't buoy up a cable much it must be able to withstand a number of tons weight pull. Especially if repairing means dragging up a piece to the surface. So delicate is probably rather a relative term. Dmcq (talk) 17:59, 1 November 2017 (UTC)

It's the stranded steel wire that takes the strain, of course, not the fibre. Dbfirs 18:04, 1 November 2017 (UTC)

• http://www.kis-orca.eu/subsea-cables/design#.WfoNEVu0NEY

20–70 tons tensile strength. Andy Dingley (talk) 18:07, 1 November 2017 (UTC)

Hey Mr. Cherrypicker, next time please present the hole cake:

"The heaviest form of armoured cable may have in excess of 70 tonnes breaking strength. While the cable may only break or part at high tensions, damage to the optical path or to the electrical insulation (the polyethylene) can occur at much lower tensions" --Kharon (talk) 23:21, 1 November 2017 (UTC)

There are two open threads on this RefDesk where you are spouting your own subjective opinion as fact, and in this case over an external source. I take your comments here, particularly the insinuation that I am lying, very much as a personal attack. Now cut it out. Andy Dingley (talk) 23:46, 1 November 2017 (UTC)

Kharon, a simple search for 'cable pulling tension' finds many, many, many, many, many results discussing maximum pulling tensions and related issues for cables, including methods to calculate pulling tensions for cables under various conditions and commercial software to help with plans, and while some look like they may be directed at smaller home runs, others at stuff like "paper mill and your client needs a 400A, 15kV feeder": [2], [3], [4] [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17] [18], [19], [20] (also look at the next page), [21], [22] (see also page 70, 58 and 59).

A number of these are from cable manufacturers themselves, and some reference a study by the Insulated Cable Engineers Association, or other studies or publications (e.g. from the IEEE or AEIC). At least some of these specifically mention or deal with a basketweave (or basket or mesh or wiremesh) grip which from Google Image search results (well also at least one of the above results) e.g. [23] [24] [25] [26], seems to be the same sort of thing we are dealing with here.

Others refer to a pulling eye which is different and only attaches to the real end of the cable [27] [28] [29] (some sources also suggest you can attach one to a basketweave grip although I'm a bit confused by this since most sources seem to show that the basket grip already has a buil in grip. Interesting, a pulling eye generally allows greater pulling tension but I don't think this is because of less damage to the cable, actually you still need to take care you don't exceed whatever it allowed for your cable. Instead I'm fairly sure it's just to do with what the equipment can survive, see the earlier results.

Note a pulling eye is different from a pulling grip, Corning Optical and others seems to use pulling grip to include what others call a basketweave or basket grip [30] [31] (which incidentally is of course another manufacturer who doesn't seem to think there's anything wrong with such devices in the right circumstances).

Anyway, so either all of these are super unprofessional as you suggest, or as others have suggested you don't know what you're talking about.

Nil Einne (talk) 13:18, 2 November 2017 (UTC)

Speaking of omitting context to misconstrue meaning, Kharon, you selectively included only part of the additional phrase. As such, you are using information about breakage by bending rather than tensile strength. DMacks (talk) 07:12, 2 November 2017 (UTC)

Thank you all for the very educational input.

Can anyone find a non-spammy ref for Towing sock? I'd hate to leave it unsourced. I tried searching .edu, .gov, and .org sites, but no luck. Anna Frodesiak (talk) 21:26, 1 November 2017 (UTC)

Hey, User:Anna Frodesiak, interesting find, and thanks for your work on this! I think some redirects are in order, and may also help you in your searches for sources: check out this commercial site [32] selling similar products as "Strain-relief grips." Sounds a bit more formal, but note the search term there is "chinese fingers"! Cable grip seems to be a general category, of which "chinese finger" is a type. See this google search [33], indicating that "pull[ing] sock" is also used [34]. Here's a "cable pulling grip" [35].

Certainly some of this commercial vendors can help in the the short term as RS that demonstrate this is a thing that has these names. Perhaps some of the names will help you find better RS. SemanticMantis (talk) 22:25, 1 November 2017 (UTC)

Hi SemanticMantis. Thank you for the thank you. I was happy to stub it. Now, you say Cable grip is the blanket term, but the lead at that article "...A cable grip is a device for propelling a vehicle by attaching to a wire cable..." makes me reluctant to add the term to the towing sock article. Should I though?

About redirects, would you be a dear and add a few that you think would be appropriate? I'm a bit out of my depth on this.

About refs, I'll keep looking, and if you bump into one, please let me know. One would think that NOAA or some US gov powergrid sort of site might mention the thing.

All the best, my friend.

Oh, and the Google link doesn't work for me because I'm in China. I'm stuck using Bing. (Stop laughing. I can feel you laughing. It's tragic, not funny.) Anna Frodesiak (talk) 08:50, 2 November 2017 (UTC)

This book [36] Electrical Power Cable Engineering, Third Edition published by CRC Press which I linked above mentions a woven basket grip but doesn't provide that many details. Another book I linked above Cables and Wiring published by Cengage Learning [37] (also look at the next page) calls it either a wire mesh grip or a basket grip (see page 66 and 70) also provides a limited amount of details but does include a diagram. I presume the links are useless to Anna, but maybe they will be useful for others. Nil Einne (talk) 13:18, 2 November 2017 (UTC)

Thank you Nil Einne and all. I've made the following redirects:

• Basket grip
• Pulling sock
• Strain-relief grip
• Wire mesh grip
• Woven basket grip

Anna Frodesiak (talk) 23:25, 2 November 2017 (UTC)

How do photons work to enable visual perception

I'm trying to get a better understanding of how photons work to enable visual perception.

I work at a location nearby an airport. During the day I may look up to the sky and see a plane up in the sky shortly after takeoff. My limited understanding is that photons coming from that plane in the sky and entering into my eye, allowing me to perceive a plane in the sky. If this is correct, I have a few questions to further my understanding:

How do the photons that entered my eye emanate from the plane? I'm assuming that the plane did not create the photons, and that most likely they originated from our Sun. So did they bounce off the earth in the direction of the plan and then bounce off of the plane and go into my eye? If so, how do photons bounce off of the earth? Do they bounce off of the earth the way a laser bounces off of a mirror or do they "scatter" off of earth in all directions? Likewise, with photons reflecting off of the plane - do they scatter in all directions or do they have a more predictable path of travel?

And finally what happens to the photon after it enters my eye? Does the photon pass through? Reflect or scatter back out in another direction? Get changed into an electrical signal and therefor (for lack of a better word) "die" as a photon?

I wouldn't be surprised if full and complete answers to my questions involved long and pronounced explanations. I welcome such, but if it makes it any easier, am really just looking for a general understanding of what is happening as I look up to the sky and perceive things.

128.229.4.2 (talk) 20:08, 1 November 2017 (UTC)

You could start with Visual system, which says that the photo receptor absorbs the photon. As to your questions about light sources, sunlight can "bounce off" things multiple times. Artificial light can do likewise. Also, a plane has built-in lights. So some of the light you see can be emanating from the plane's lights. But most of it is coming from the sun, either directly or by reflecting off something else. For example, a building with reflective glass windows, where you might see a reflection of the plane (or any object). ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:29, 1 November 2017 (UTC)

Something else to think about: At or near full moon, the moon is pretty bright. If you're someplace with minimal light pollution, you can see objects in the moonlight. The moon itself emanates no light. Moonlight is totally from reflection, nearly all of that coming from sunlight. So if you see an object in the moonlight, you're seeing it via sunlight bouncing off the moon and then bouncing again off the object and into your eyes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:35, 1 November 2017 (UTC)

Diffuse and specular reflection from a glossy surface.

This is more a question about Optics than about the human eye specifically, but it's a big question!

Briefly, you're mostly right. The light you see from a plane did not originate from the plane.(Excepting the light from light sources on the plane itself like landing lights.) It's either lit by the sun itself, or from light reflected off the earth. The Difference between photons reflecting like a mirror, or scattering in all directions is the difference between Specular reflections and Diffuse reflections. (The shinier an object is, the more specular reflection will happen.) And yes, the Photoreceptor_cells in your eye can absorb photons. And so can many other things. A black piece of cloth can absorb photons and convert them to heat.

I'm sure my little paragraph here isn't very informative on this huge subject, but the articles I linked are very in depth, and worth reading. ApLundell (talk) 21:26, 1 November 2017 (UTC)

Agreed. Note also that those articles sometimes talk about light as a wave; see also wave–particle duality for a lot more on that concept. Oh, and also note that some of the incoming light is scattered in the air, not from the Earth's surface. --69.159.60.147 (talk) 21:31, 1 November 2017 (UTC)

• Since no one has yet spoken to the biophysical, neurophysiological and cognitive mechanisms at work with regard to your latter set of questions (regarding what happens once the light enters the eye), and seeing as visual cognition is an area in which I have expertise, I will pick up the description from there. However, owing to time constraints, I may explain this process in small installments over the next couple of days, as this is a deeply complex set of topics--though I will try to keep discussion concentrated on the most top-level processes and try not get caught up in the weeds on the chemistry and neuroscience.

Photons enter the eye through the optic lens, which, in the human eye, is controlled by muscles which flex it in order to focus the light on different portions of the retina, which absorbs the photon. Amongst the matter absorbing these photons are photoreceptive cells, rods and cone cells. These cells are preferentially sensitive to light of varying wavelengths and intensity (see also Photometry (optics) and Luminance). The absorption of photonic energy catalyzes a reaction in a receptive protein molecule, of class known as opsins, creating a chain reaction of protein activity for the purposes of cell signaling. The degree and duration of this stimulus either excites or inhibits the cell, towards a threshold where the cell will be more or less inclined to fire, sending a bioelectrical signal to another kind of specialized nerve cell, as the first step of relaying the signal that carries information as to what has happened with that particular receptor into the optic nerve and ultimately into the brain, where the combined stimulus of all the receptors is amalgamated, filtered and processed to create visual perception and the subjective experience of vision; the higher-level neuroscience, cognitive psychology and metaphysics of the perception are where I will pick up tomorrow. Hope the first part helps for now! Snow ^{let's rap} 07:37, 2 November 2017 (UTC)

Then, do you know if, what appears to be red to 1 person, could be blue to another, what is blue to another, could be green to a 3rd? Etc. Thanks. 12.130.157.65 (talk) 12:08, 2 November 2017 (UTC).

That question overlaps two subquestions. An illustrative case is colour blindness, which was scientifically described first at the turn of the 18th century, but certainly existed long before. The first subquestion is whether the eyes of two different individuals have the same physiological response to stimuli - in which case, I cannot answer (beyond the case of colour blindness pathologies). The second is whether the perception of those stimuli is the same, regardless of the physiological response - in which case, there is an abundant literature on the subject in psychology and philosophy: one of the key words is qualia, but that article is a hard read; Color_vision#Subjectivity_of_color_perception may be an easier explanation of why that is even a question. Tigraan^{Click here to contact me} 12:23, 2 November 2017 (UTC)

Okay, so no part 2 Snow Rise? Anyways, they say when someone is red-green color-blind, they don't see both red and green as red, or both as green, but both as the same reddish-green. But how can we know that? 12.130.157.65 (talk) 11:30, 5 November 2017 (UTC).

Regarding the behavior of photons, there's a few key things to remember here: Light is light. It is a phenomenon that produces certain data based on the manner in which it is observed. When we ask what light is, the only response is "this phenomenon that produces this data from these observations and experiments". What we then ask is "how do we model light" the answer is "we model it as either a wave or a particle depending on what a particular situation needs". Which is to say "In some situations (i.e. the photoelectric effect), it makes sense to model light as a particle. In other situations (diffraction), it makes sense to model light as a wave". The ontological question (what is light REALLY?) is not something which is particularly relevent or useful in physics, it's a philosophical issue, not a scientific issue. The only thing science does really is create predictive models: a set of laws, theories, equations, etc. which when given a certain input, make accurate predictive outputs. The only reason I bring that up is the implicit problems with discussing quantum phenomena like light, where we're always dealing with switching our brains between thinking of light as a particle, and thinking of it as a wave. In the case of vision, both are really needed here:

• Concepts like scattering and diffraction and refraction and the like really make more sense to think about in terms of wave-like properties of light. So when asking "how does this light get to my brain to make an image", many of the phenomena between the object you are looking at, including the way the light is affected by the surfaces, materials, and substances involved simply model better as wave phenomena. Famously, even a single photon obeys the wave patterns, the famous Young's double slit experiment showed that a single particle can be made to split and interfer with itself.
• Concepts like how the light interacts with the rod cells and cone cells in the back of the eye to produce an electrochemical signal work better if light is modeled as a particle rather than a wave. That's because fundementally, it involves individual photons of light exciting individual electrons in photoreceptor proteins like rhodopsin in a very one-to-one particle-like manner which cannot adequately be explained by wave behavior.

The thing is, this stuff is really hard in the sense of it is NOT intuitive. Every physicist, chemist, etc. who studies or has to explain this stuff I've ever heard speak on the matter is never comfortable with issues of wave-particle duality because it just doesn't make sense in the "this is what my experience in the world tells me life is like" sense, even the people who do this as a vocation never really come to find it a natural way of thinking. The only reason we use it is because it works scientifically: it produces highly accurate, meaningful and predictive results in our laws, theories, and models, and more importantly alternative perspectives do NOT. So, there it is. --Jayron32 11:10, 2 November 2017 (UTC)

These are great responses to my questions -- thank you all so much for taking the time to share the information and references you provided! 128.229.4.2 (talk) 12:37, 2 November 2017 (UTC)