explain xkcd - User contributions [en]

1892: USB Cables

2024-11-27T13:10:38Z

PleaseConsiderReCaptchaV3ForRegistration: /* Explanation */ Updated the URL to the Micro USB's specifications to the archived one as the original URL was dead

{{comic
| number = 1892
| date = September 20, 2017
| title = USB Cables
| image = usb_cables.png
| titletext = Tag yourself, I'm "frayed."
}}

==Explanation==
In this comic, [[Randall]] states the 'Law of {{w|USB}} cables': You will never have more than one which has no problems, no matter how many you get. Now that most devices charge off USB, having a cable (specifically, USB-A (the big end) to Micro-B or USB-C (the small end)) is essential. However, most USB cables are cheaply made, and carrying them around quickly damages them. This comic lists some common (and not so common) problems with USB cables.

* '''Carry power but not data''' - USB cables have separate data and power lines. To save money (and sometimes for security reasons), the data lines can be omitted. This means it can be used for charging, but not data transfer. Two cables are shown with this problem.
* '''Carries data but not power''' - Not typically done, but it could happen if the wires or pins get damaged. While such a cable is theoretically possible, if used with standards-compliant devices, it would appear [https://electronics.stackexchange.com/questions/313955/does-usb-host-always-supply-power-on-vbus completely broken].
* '''Too short''' - Another money saving wheeze, some devices ship with pathetically short cables.
* '''Charges phone slowly''' - More likely a problem with the charger than the cable, but may happen if the wires are damaged. Refers to some chargers not delivering more than half an ampere. Could also be caused by thin or very long wires which lead to a significant voltage drop, thereby reducing charging speed. This is also a typical user experience for cables that carry power but not data, as charging current/voltage negotiation typically happens over the data lines.
* '''Won't auto-activate portable charger''' - Most portable chargers (basically big batteries) should activate when the device is plugged in. Something about the cable (possibly the way the data lines are shorted) is interfering with this mechanism.
* '''Has annoying ferrite lumps''' - {{w|Ferrite bead}}s are used to filter out interference from the cable. High-performance applications need these, but on a phone charger you're just adding unnecessary weight and bulk. Two cables are shown with this problem.
* '''Heavy and not very flexible''' - Either a heavy-duty USB cable, with thicker insulation, or a shielded one with a metal sheath inside to keep out interference.
* '''Frayed''' - Cables with improper strain relief experience a lot of bending force at the ends, near the connectors, and these can easily burst the insulation as shown here. Two cables are shown with this problem.
* '''Plug doesn't fit through case''' - Manufacturers don't always follow the standard for what the plastic housing around the USB connector should look like, and sometimes these are molded so they don't quite fit in the phone socket or through the charging port of an external case.
* '''Needs to be twisted to keep working''' - The wires inside are damaged, and only connect when held in just the right way. One step away from total breakage.
* '''Weird shape''' - A normal USB cable but [https://web.archive.org/web/20201112023959/http://read.pudn.com/downloads114/doc/comm/476505/usb_20_040908/usb_20/Micro-USB_final/Micro-USB_1_01.pdf the connector is molded with a 90 degree turn (which is actually specified in the MicroUSB Specification, see pages 28-31)] for no apparent reason and might be not convenient in some situations.
* '''The good one''' - This is the one that really works out of the 15 shown, with 11 different problems. The funny thing is that it looks more or less exactly like at least 6 of the other 14. So it will take some time to find this cable.

The title text refers to the popular meme "[http://knowyourmeme.com/memes/tag-yourself Tag yourself, I'm...]" which is used with pictures containing lots of strange objects, phrases or other elements. The phrase prompts people to identify individual elements from the image that they personally feels matches their own identity, usually self-deprecatingly. (The meme stems from Facebook, where people can place tags identifying themselves in photos, but has spread to other websites without an actual tagging system.) Here, Randall suggests that, like a USB cable, he's frayed. "I'm frayed" is also a pun on the sentence "I'm afraid" that is commonly added to the end of a comment which the speaker believes may leave a negative impression on the listener.

==Transcript==
:[15 USB cables are shown lying in a column. They are mostly very similar, with small differences. To the right of the cables there are 12 labels, as three of the labels belongs to three sets of two cables.]
:[2 cables] Carry power but not data
:Carries data but not power
:Too short
:Charges phone slowly
:Won't auto-activate portable charger
:[2 cables] Has annoying ferrite lumps
:Heavy and not very flexible
:[2 cables] Frayed
:Plug doesn't fit through case
:Needs to be twisted to keep working
:Weird shape
:The good one

:[Caption below the panel:]
:The law of USB cables: No matter how many you get, you only ever have one good one.

{{comic discussion}}

2501: Average Familiarity

2024-08-17T20:23:04Z

PleaseConsiderReCaptchaV3ForRegistration: Fix the misquoted "without hitting one" to "without throwing one"

{{comic
| number = 2501
| date = August 11, 2021
| title = Average Familiarity
| image = average familiarity.png
| titletext = "How could anyone consider themselves a well-rounded adult without a basic understanding of silicate geochemistry? Silicates are everywhere! It's hard to throw a rock without throwing one!"
}}

==Explanation==
This comic claims that experts vastly overestimate how familiar other people are with their own field of study. As an example, [[Randall]] shows a conversation between [[Ponytail]] and [[Cueball]] as two {{w|geochemistry|geochemists}} specializing in {{w|silicate}} chemistry. Although the two scientists understand that the layman does not know all that they know about silicates, they are still under the impression that other people at least know the chemical makeup of {{w|olivine}} and some {{w|feldspar}}s. Cueball also mentions {{w|quartz}}, an even simpler mineral taken for granted by Ponytail.

In truth, the average person can't be expected to know the chemical makeup of ''any'' arbitrarily-chosen substance reliably (or any material at all), if that average person's job and hobby do not involve chemistry — aside from the few that made their way into {{w|common knowledge}}, like NaCl for salt (sodium chloride or {{w|halite}} in mineral form), H2O for water (facetiously known as dihydrogen monoxide, {{w|ice}} in mineral form), or CO2 for carbon dioxide (while most people are more familiar with its gaseous form, it is also used in mineral form as {{w|dry ice}}), and may not even know the definition of "feldspar" beyond "a mineral", if at all.

It even goes so far as to initially gloss over the 'everyday' knowledge of quartz... until prompted by the slightly-less-overestimating partner in the conversation. Perhaps like a gardener forgetting to mention the lawn he maintains (along with the 'actual' plants in the borders or vegetable patches), there seemed no need to include such a common mineral as a subject of silicate chemistry. Quartz is a basic silicon oxide (SiO2) that many non-chemists ''have'' heard of because it is common and has a variety of uses, though they would not know its chemical structure. Quartz ''can'' be found as distinct large-scale crystals (probably obvious to the layman, as an ice-cube is in a drink) but also features as a hard-wearing micro-constituent of many rocks. Quartz is a major component of most sand (except for coral sands, which are calcium carbonates). Quartz crystals are sometimes made into jewelry and other decorative objects. Most modern clocks use {{w|Crystal oscillator|the resonance frequency of quartz}} to keep time.

Minerals like feldspars and olivine generally exist as a continuum of varying chemical formulas, represented as a mixture of "endmembers" that have some pure composition. Feldspars are a category of aluminum-containing silicate minerals that account for the most of the rock in the earth's crust by mass. They are composed of a silicon-aluminum-oxygen lattice filled with sodium, potassium, or calcium ions. The major varieties are CaAl2Si2O8 (anorthite), NaAlSi3O8 (albite), and KAlSi3O8 (potassium feldspar). Olivine is most notable as being the primary constituent of the upper mantle and commonly found in stony meteorites, and has the formula X2+2SiO4, where X is any iron or magnesium ion. The ends of the spectrum are Mg2SiO4 ({{w|forsterite}}) and Fe2SiO4 ({{w|fayalite}}).

In the title text the two geologists express belief that the average person ''should'' be more familiar with silicates because of how ubiquitous they are. Their somewhat-exasperated statement plays on the phrase "you can't throw a rock without throwing one," a standard hyperbole about how common something is. Indeed, {{w|Silicate mineral|silicate}} rocks are extremely common on Earth — not only would a rock thrown in a random direction stand a decent chance of striking a silicate mineral rock, but the rock being ''thrown'' also has a very high chance of being a silicate mineral rock. With the exception of a few carbonate deposits, rocks found in large deposits on Earth's surface nearly all have silica in them, even extraterrestrial rocks. The Earth's crust is about 60% silica by weight.<ref>"Constraining crustal silica on ancient Earth" C. Brenhin Keller, T. Mark Harrison. ''Proceedings of the National Academy of Sciences'' Sep 2020, 117 (35) 21101-21107; DOI: 10.1073/pnas.2009431117</ref>

==Transcript==
:[Ponytail and Cueball are talking. Ponytail has her hand raised, palm up, towards Cueball.]
:Ponytail: Silicate chemistry is second nature to us geochemists, so it's easy to forget that the average person probably only knows the formulas for olivine and one or two feldspars.
:Cueball: And quartz, of course.
:Ponytail: Of course.

:[Caption below the panel]
:Even when they're trying to compensate for it, experts in anything wildly overestimate the average person's familiarity with their field.

== References ==
<references />

{{comic discussion}}

[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Cueball]]
[[Category:Geology]]
[[Category:Science]]