explain xkcd - User contributions [en]

3093: Drafting

2025-05-23T19:05:27Z

162.158.216.175: /* Explanation */

{{comic
| number = 3093
| date = May 23, 2025
| title = Drafting
| image = drafting_2x.png
| imagesize = 317x518px
| noexpand = true
| titletext = A 5% efficiency gain at the cost of a 99% efficiency loss
}}

==Explanation==
{{incomplete|This page was created by a bot that should not have tried this. Don't remove this notice too soon.}}
This is another one of [[Randall|Randall's]] [[:Category: Tips|Tips]], this time an Aerospace tip.

{{w|Drafting (aerodynamics)|Drafting}} is an aerodynamic technique where one moving object follows another one closely to reduce drag by using the first objects {{w|slipstream}}. It is used in various sports, most prominently {{w|cycling}}.

The comic explores the idea of using drafting for rockets and states that while it theoretically works, it isn't really recommended.

The title text gives more details on this, claiming that there is an efficiency gain of 5% through drafting via the general mechanism, it also comes with a 99% loss, likely because a drafting rocket would almost certainly be annihilated by the leading rocket.

Generally, this could be understood because land transportation is based on traction (pulling yourself along a surface via friction). At higher speeds (above 60km/h), the dominant force becomes wind drag. {{w|Energy-efficient driving}} at these higher speeds can be improved by drafting behind another vehicle. This doesn't apply to rockets because they do not move themselves via friction but rather via Newton's third law (throwing stuff backwards). This means that the front rocket would just push the back rocket against its own thrust (among other bad effects).

==Transcript==
:[A rocket with two boosters is launching going towards the top right corner. It has a two-stage core, and two boosters and they produces three flames from their exhaust and beneath these flames is a large exhaust plume fanning out behind the rocket most of the way towards the bottom of the panel. A smaller rocket is following the first rocket. It is very close to the first rocket, so most of the smaller rocket is inside the exhaust plume from the larger rocket. The smaller rocket does not have boosters, but still produces three smaller flames from its exhaust. Beneath these flames the smaller rocket also leaves a large but slimmer exhaust plume that exits the panel at the bottom left corner.]

:[Caption below the panel:]
:Aerospace tip: Although the technique reduces atmospheric drag for many types of vehicles, you should '''''never''''' try to improve rocket launch efficiency through drafting.

{{comic discussion}}<noinclude>

[[Category:Tips]]
[[Category:Rockets]]

Talk:3089: Modern

2025-05-14T22:01:51Z

162.158.216.175:

Hate to be that guy, but wow, it’s empty [[User:Broseph|Broseph]] ([[User talk:Broseph|talk]]) 19:04, 14 May 2025 (UTC)

This strip reminded me of the comments in [[3063]]. Historians / historiographers typically define (early) "modernity" to begin around 1500. {{w|early modernity}} [[Special:Contributions/172.71.182.126|172.71.182.126]] 19:12, 14 May 2025 (UTC)

A similar problem exists, where a recent version of the Bible is known as the New Revised Standard Version. It will be a bit awkward when it is not new, revised, or standard. [[User:BobcatInABox|BobcatInABox]] ([[User talk:BobcatInABox|talk]]) 19:38, 14 May 2025 (UTC)
:The US Military has a similar problem: naming a system "Next-Gen [X]" but then the "Next Gen" item eventually becomes the current generation, and is eventually moving towards being obsolete and you need a successor (next-next gen?).[[Special:Contributions/172.69.6.111|172.69.6.111]] 20:05, 14 May 2025 (UTC)
::I guess the phone companies got it right with the 3G, 4G, 5G naming. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 20:23, 14 May 2025 (UTC)
::: Except for that {{w|10G}} glitch. And Dilbert predicted people copyrighting "8G" years before that. [[Special:Contributions/104.23.172.75|104.23.172.75]] 20:34, 14 May 2025 (UTC)
Wasn't there an earlier strip describing a similar problem on Wikipedia edits, maybe tied to the {{w|recency bias}}? There's the idea that every more recent slice needs a new, relevant name. It also seems to work going backwards, where humanity's genus, tribe, subfamily, and family are "homo", "hominini", "homininae", and "hominidae" respectively. We seem to crave a name for every arbitrary slice that is relevant for a particular researcher. And now I'm thinking of Futurama's "New New York". I'm surprised there's not already a New New York somewhere. [[Special:Contributions/162.158.233.117|162.158.233.117]] 20:31, 14 May 2025 (UTC)
:Eventually, there'll be a [https://tardis.fandom.com/wiki/New_New_York New New New New New New New New New New New New New New New York]...
:Anyway, I actually live not far from a(nother) {{w|New York#United Kingdom|New York}}, and am also a regular visitor to (old) York. So I may not have been to New York, New York, on my travels, but I've got it covered on both sides. (I ''have'' been to both new Boston ''and' the old one, but only been to the old Washington, both the original Richmond and its first copycat (but none of the US copycopyⁿcats), etc.) [[Special:Contributions/162.158.216.175|162.158.216.175]] 22:01, 14 May 2025 (UTC)

2818: Circuit Symbols

2025-03-25T08:49:19Z

162.158.216.175: Undo revision 370200 by 172.71.215.193 (talk)

{{comic
| number = 2818
| date = August 21, 2023
| title = Circuit Symbols
| image = circuit_symbols_2x.png
| imagesize = 438x362px
| noexpand = true
| titletext = A circle with an A in it means that the circuit has committed a sin and has been marked as punishment.
}}

==Explanation==
This comic contains several symbols used in circuit diagrams. Each is labeled with a larger object that the symbol looks like a drawing of, rather than the electrical component it actually represents. Randall has previously depicted distorted uses, depictions, and labeling of the standard US-form {{w|electronic symbol}}s in comics such as [[730: Circuit Diagram]].

{| class="wikitable"
! Symbol !! Randall's Description !! Explanation
|-
| {{w|Switch}}
| {{w|Drawbridge}}
| The symbol represents a physical on/off {{w|switch}} in a circuit, but also resembles a {{w|drawbridge}}. A switch functions the exact same as a drawbridge, impeding electrons' flow when it is open. The purpose of a drawbridge is to allow people to cross who are impeded when the bridge is raised.
|-
| {{w|Capacitor}}
| {{w|Overpass}}
| A {{w|capacitor}} is a component that can be used to hold electric charge, but the symbol for it looks a bit like a depiction of a highway {{w|overpass}}, where one road or track passes over another, allowing the paths to cross without intersecting. The distinction between an overpass and {{w|Tunnel#Underpass|underpass}} is largely one of perspective, as when one road (or footpath, or animal migration route) goes over, the other is going under. Because a capacitor does not indicate a place of intersection of separate electrical circuits, any interpretation of a meaningful connection between an overpass and a capacitor is tenuous at best. A capacitor is an electrical component that alternating current can get across, but direct current can't. This could be like how heavy trucks are not allowed on overpasses. However, this still only involves one electrical pathway.
|-
| {{w|Ground (electricity)|Ground}}
| {{w|Pogo Stick}}
| This symbol represents a connection to "{{w|Ground (electricity)|ground}}" or "earth", the common baseline voltage ''or'' safe current sink for various circuits (e.g., against which an aerial signal can be compared). If the horizontal lines are taken as motion lines or a spring, it might look like a stylized {{w|pogo stick}}.
|-
| {{w|Resistor}} (ANSI)
| {{w|Earthquake}}
| A {{w|resistor}} is a component that reduces current flow in a circuit. There are two main symbols used: an IEC-style 'box' or, like here, the ANSI zig-zagged line. In this case, it also looks somewhat like the marks an earthquake makes on a seismograph and/or the 'rucks' of the ground (especially asphalt roads) that might result from underlying tectonic movements.
|-
| {{w|Inductor}}
| {{w|Sheep}}
| {{w|Inductor}}s create a magnetic field when current passes through them, and generally consist of a coil of wire, which the symbol reflects. The symbol seems in this case to be interpreted like the fluffy wool of a sheep.
|-
| {{w|Transformer}}
| Two sheep in love, trapped on opposite side of a fence.
| A {{w|transformer}} consists of two (or more) induction coils, for input and output(s), and a common core to mediate the transfer of power across the gap. The curly loop symbols of the symbol have already been claimed to resemble sheep, and the straight line (which is the core) now represents a fence separating two sheep who nonetheless wish to be together.
|-
| {{w|Electric battery|Battery}}
| Battery
| Not a joke, this is a typical symbol for a {{w|Electric battery|battery}} (which provides voltage to a circuit),{{citation needed}} or other form of {{w|voltaic pile}}. Its inclusion here is simply as the set-up for the following joke symbols.
|-
| Battery (sorted)
| Baertty
| Randall may have mapped the characters "tt" to the first short line and "er" to the following long line in the original symbol, having had "ba" and "y" assigned to the long and short "T" shapes that form the connections to the rest of the circuit. Rearranging the symbolic verticals as long-long-short-short, as he has done in this (fictional) symbol, thus puts "er" in front of "tt". Another sorting paradigm is that, after the initial 'B', the remaining letters are arranged in alphabetical order, left to right. Similarly, after the first horizontal line in the symbol, the other line segments are arranged by decreasing vertical height (left to right).
|-
| Battery, with far too many short lines
| Battttttttttttery
| The only other fictional symbol. Which, by the same established naming rules, means that the name is spelled with six "tt"s instead of just the single pair.
|-
| {{w|Photodiode}}
| Check out this really cool diode
| A {{w|photodiode}} generates, or allows to pass, a current in response to light. The symbol is related to the standard {{w|diode}} with the arrows pointing at it representing the light which activates its behavior. In this case, Randall instead pretends that the arrows are pointing at it to draw attention to it because it's "really cool" ({{w|Photodiode#Applications|it is!}}).
|-
| {{w|Electronic oscillator|Oscillator}}
| {{w|Wave Pool}}
| An {{w|Electronic oscillator|oscillator}} generates signals that oscillate at a given frequencies, for use in other circuitry, and one symbol used for one (in reality, built from a number of components in their own right) is this symbol. Waves in water are a type of oscillation that may be more familiar to most people than waves of electricity. A {{w|wave pool}} is in fact the ''result'' of a type of (mechanical) oscillator, and rarely has electricity running through it.{{Citation needed}}
|-
| {{w|Transistor}}
| Trolley Problem
| A {{w|transistor}} will switch on current flow across one of a pair of connections, depending upon the input from an input one. Randall likens this to the ability to use points to switch the destination of a trolley from one track to another, as protagonists are invited to do in the various versions of the {{w|trolley problem}}. The symbol also somewhat resembles the usual pictorial depiction of the problem. However, single transistors are not generally used to resolve ethical dilemmas.{{Citation needed}}
|-
| {{w|Ammeter|A circle with an A}} [In the title text]
| The circuit has committed a sin and has been marked as punishment
| Circles with letters are usually some special components, as also with the oscillator's glyph. In this case the "A" stands for ammeter, a device used to measure {{w|electric current}} (an "{{w|ampere}} meter"). This is conflated with the practice of branding the 'guilty', or requiring them to display their crime for a period of penance. For example, in ''{{w|The Scarlet Letter}}'', a historical novel by {{w|Nathaniel Hawthorne}}, the protagonist must wear an ''A'' to mark her as an adulteress.
|}

==Transcript==
:[A chart of various circuit symbols and their (mostly) fictitious meanings based off of their drawings, captioned:] Circuit Symbols
:[Symbol for a switch, labelled:] Drawbridge
:[Symbol for a capacitor, labelled:] Overpass
:[Symbol for a connection to ground, labelled:] Pogo Stick
:[Symbol for a resistor, labelled:] Earthquake
:[Symbol for an inductor, labelled:] Sheep
:[Symbol for a transformer, labelled:] Two Sheep in Love, Trapped on Opposite Sides of a Fence
:[Symbol for a battery, labelled:] Battery
:[Symbol for a battery, sorted, labelled:] Baertty
:[Symbol for a battery, with far too many short lines, labelled:] Battttttttttttery
:[Symbol for a photodiode, labelled:] Check Out This Really Cool Diode
:[Symbol for an oscillator, labelled:] Wave Pool
:[Symbol for a transistor, labelled:] Trolley Problem

{{comic discussion}}

[[Category:Engineering]]
[[Category:Charts]]
[[Category:Animals]]