explain xkcd - User contributions [en]

2818: Circuit Symbols

2023-08-22T11:10:30Z

172.70.91.161: /* Explanation */ No map *symbol* (e.g. "bridge" symbol to show where embankment becomes different-grade crossing point of another track). But highly dependent upon mapping convention (could be minor-road crossroads/single-track exits of dual-carriageway)

{{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==
{{incomplete|Do NOT delete this tag too soon.}}
{| class="wikitable"
! Symbol !! Randall's Description !! Explanation
|-
| Switch
| Drawbridge
| The symbol represents a physical on/off switch in a circuit, but also resembles a medieval drawbridge.
|-
| Capacitor
| Overpass
| A capacitor is a component that can be used to hold electric charge, but also looks a bit like a map depiction for a highway {{w|overpass}} of a main road passing over a more minor track. This may actually be refered to more as an {{w|Tunnel#Underpass|underpass}}, from the perspective of the lesser route, being not usually as obvious a feature when using the upper highway.
|-
| Ground
| Pogo Stick
| This symbol represents a connection to "ground" (aka earth for folks in the UK). If you squint, it also looks like a pogo stick.
|-
| Resistor (ANSI)
| Earthquake
| A resistor is a component that reduces current flow in a circuit. If also looks like the signs an earthquake makes on a seismogram and/or the 'rucks' of the ground (especially asphalt roads) that might result from underlying techtonic movements.

|-
| Inductor
| Sheep
| Inductors are essentially the opposite of capacitors and generally consist of a coil of wire. The symbol can also look like fluffy curls of wool.
|-
| Transformer
| Two sheep in love, trapped on opposite side of a fence.
| The input and output coils on a transformer are represented as curly loops, which Randal claims resemble sheep, and the straight line (which represents the core) is a fence.
|-
| Battery
| Battery
| Not a joke, that's the symbol for a battery.
|-
| Battery (sorted)
| Baertty
| Randall seems to be mapping "tt" to the first short line and 'er' to the second long line in the symbol, having had 'ba' and 'y' assisnged to the long and short 'T' shape, and asserting that if you sort them long-long-short-short, you need to put "er" in front of "tt".
|-
| Battery, with far too many short lines
| Battttttttttttery
| Or, you know, you could just throw in six "tt"s.
|-
| Photodiode
| Check out this really cool diode
| A photodiode generates current in response to light (the arrows pointing at it.) Randall is instead pretending that the arrows are pointing at it to draw attention to it because it's really cool.
|-
| Oscillator
| Wave Pool
| An oscillator generates signals at a given frequencies. A wave pool, it could be argued, is in fact a type of oscillator, just with water instead of electricity.
|-
| Transistor
| Trolley Problem
| A transistor will switch on a current flow depending on the input from a input signal. Thus, it switches electricity in the same way that the trolley problem switches the trolley. The symbol also somewhat resembles the usual pictorial depiction of the problem.
|-
| Circle with an A in it (Title text)
| Committed a sin and marked as punishment
| Circles with letters are usually some special component. In this case the "A" stands for ammeter, a device used to measure current. In Nathaniel Hawthorne's novel ''The Scarlet Letter'', the heroine must wear an ''A'' to mark her as an adulteress.
|}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
picture of drawbridge:drawbridge

{{comic discussion}}
[[Category:Engineering]]
[[Category:Charts]]

Talk:2816: Types of Solar Eclipse

2023-08-17T06:35:57Z

172.70.91.161:

Is the annular eclipse actually possible? [[Special:Contributions/162.158.78.118|162.158.78.118]] 21:24, 16 August 2023 (UTC)

Yes. https://solarsystem.nasa.gov/eclipses/2023/oct-14-annular/where-when/ [[Special:Contributions/172.69.33.7|172.69.33.7]] 21:34, 16 August 2023 (UTC)

I interpret the Hug Eclipse as the sun wrapping around the moon giving it a hug, rather than the moon being pinched in on the sides. [[Special:Contributions/172.70.211.62|172.70.211.62]] 21:38, 16 August 2023 (UTC)
:I amended that (twice, first time got blitzed in an Edit Conflict situation), when I thought of a better way (two slightly different better ways! ...might not even have used the better one, in instance #2) to describe it. But I rushed a bit anyway... I can see typos. (Not including the likes of "centre", which is not a typo but me defaulting to British English by default; though no doubt that 'needs' changing too.)
:I'm still wondering if just "label" and "description" columns are needed (image details can be recycled into Transcript, per label). Or if it could be ";header" and ":...description" without the table, but I think it looks no worse than I had feared, as the current table form. Of course, others have added more prosaic explanation paragraphs, so I'll let it sit a while. Almost certainly the other active editors here are going to have ideas about how to merge/expunge my efforts, and I'll let them copyedit my errors/'errors' as well. But at least there's a framework answer (or several) now. [[Special:Contributions/172.70.162.179|172.70.162.179]] 22:20, 16 August 2023 (UTC)

That must be a VERY scary dragonite. [[Special:Contributions/172.71.26.153|172.71.26.153]] 02:20, 17 August 2023 (UTC)

I love this community, which will explain how a solar panel works and why the moon cannot give the sun a hug with the same level of rigor and detail. [[Special:Contributions/172.69.247.40|172.69.247.40]] 04:26, 17 August 2023 (UTC)

I have always wondered about solar eclipses... does anybody else think it's really weird that the Earth is not just the only planet with exactly the right ratios of star/satellite size/distance to make eclipses happen, but is also the only planet (so far as we know) where there's an evolved intelligence that can appreciate such a phenomenon? After all, a similar effect viewable only from Mars or Venus would be totally wasted... [[Special:Contributions/172.70.91.161|172.70.91.161]] 06:35, 17 August 2023 (UTC)

Talk:2812: Solar Panel Placement

2023-08-08T15:36:45Z

172.70.91.161:

Can someone smarter than me do the math on running power lines to a panel on the sun? How long until it would pay for itself?[[Special:Contributions/172.70.214.125|172.70.214.125]] 05:08, 8 August 2023 (UTC)
:$22 million / $0.20 per kWH = 110 million kWH, divide by hours in a year and you get about 12549 kW. Google says the sun is 150 million KM away. IDK the exact details, but a calculator I found online suggests a copper cable with a cross-sectional area of 10m^2 can handle that amount of power transported 150 million KM. The density of copper's about 9 cm/g^3. 150 million km * 10 m^2 * 9 g/cm^3 = 1.35 * 10^16 kg. The cost to get one kilogram to Low-Earth Orbit according to google is >$10,000, let's just use that. Total cost to get to LEO: $1.35 * 10^20. Divide by profit per year => 6.1 trillion years. [[User:Tiln|Tiln]] ([[User talk:Tiln|talk]]) 07:10, 8 August 2023 (UTC)
::"The cost to get one kilogram to Low-Earth Orbit [...], let's just use that." Ummm... It's actually easier to ''leave'' the solar system than to rendezvous with Mercury (never mind attain even closer stability to the Sun's surface).
::I supose you could always go to an orbit a very long way away (near solar-escape) and add a little extra reverse delta-V to zero your orbital movement and then fall down. But you must not miss the pinprick Sun, or you're in a highly elliptic comet-like trajectory (with even higher demands needed to circularise at perihelion), so you need to be very precise about stopping and dodging through the gravity wells of any planets you plunge past. Not that ''not'' missing is going to do you much good, either.
::...hmmm, hang on, maybe that's what the cables back to Earth are for. Spooled in/out just at the right rate (perhaps some bungee-chord included), it's how you stop ''just above'' the Sun's surface (at the limit of the conductive cable, then cut the retarding bungee just as you're stable enough at the bottom of the bounce!) and stay there. Ok, not a problem. It'll work after all{{Actual citation needed}} and I withdraw all my petty objections! [[Special:Contributions/172.71.242.82|172.71.242.82]] 10:43, 8 August 2023 (UTC)
::: And then you'll have to deal with the end of the bungee cord retracting under it's own tension... and since it's no longer tethered to the craft it would probably whip back towards Earth. As an afterthought, have you ever been whipped by a released rubber band? Imagine that... but at a cosmic scale. I'd probably take my chances with the cables. [[User:Xkcdjerry|Xkcdjerry]] ([[User talk:Xkcdjerry|talk]]) 14:39, 8 August 2023 (UTC)

Congrats, you've just made the universe's smallest Dyson sphere component! [[Special:Contributions/162.158.2.38|162.158.2.38]] 07:33, 8 August 2023 (UTC)

I'd just like to point out an error in Randall's math:
The light incident on the panel would only be from the portion of the surface with line-of-sight to the panel. This fraction is called the "view factor", and has its own Wikipedia page, which I'm too lazy to link since I'm editing this on my phone. Carry on! [[Special:Contributions/172.70.126.217|172.70.126.217]] 13:26, 8 August 2023 (UTC)
:I thought Sun luminosity (total outgoing light, in all directions from all points of itsvsurface) divided by Sun area (total luminescing surface area) multiplied by the 1m² (the actual 'capturable' parts normalised to the effectively-in-contact portion of the Sun exactly in the way you're defining the view factor.
:Further out, distance from the Sun factors in as an inverse square relationship, but it'll be negligable when you're practically at the Surface and close to the full 2pi steradian of incident light from a significantly greater area of emitting surface than the unit-area of receiving surface. Once you're at Earth-orbit distance, it's a tad below 70 nanosteradian of "panel view" and almost none of the light even from the directly facing square metre of Sun even comes close to the even smaller solid angle subtending the outwards spread of light.
:Set your panel at the height of various solar-surface features, you might not intercept much of the light (hence division by Sun's area) yet what you'll capture will be significant. Probably well beyond any long-(/medium-, perhaps even short-)term survivability of a lump of plastic, silicon and metals normally stuck on a house roof. [[Special:Contributions/172.70.91.161|172.70.91.161]] 15:36, 8 August 2023 (UTC)

I was briefly confused because HVAC usually stands for heating, ventilation, and air conditioning, but is here used to mean high-voltage alternating current. [[Special:Contributions/172.69.247.50|172.69.247.50]] 13:31, 8 August 2023 (UTC)
:I often have the ''opposite'' confusion... ;) [[Special:Contributions/172.70.91.161|172.70.91.161]] 15:36, 8 August 2023 (UTC)

I ran some calculations on using rechargeable batteries to get power from the Sun to Earth, full markdown file is [https://github.com/xkcdjerry/markdown-pages/blob/main/explainxkcd-2812-talk-calcuations.md here] is anyone to check it out.

TL;DR: it's ''way'' better than running powerlines to Earth but falls slightly shy of putting a panel on Earth, though that may be remedied by more precise data. [[User:Xkcdjerry|Xkcdjerry]] ([[User talk:Xkcdjerry|talk]]) 15:09, 8 August 2023 (UTC)

2785: Marble Run

2023-06-07T13:46:42Z

172.70.91.161: /* Explanation */

{{comic
| number = 2785
| date = June 5, 2023
| title = Marble Run
| image = marble_run_2x.png
| imagesize = 438x512px
| noexpand = true
| titletext = I have so many plans. It would incorporate a Galton board, a Ranque-Hilsch marble vortex tube, and a compartment lined with pinball bouncers with a camera-and-servo Maxwell's Demon that separated the balls into fast and slow sides.
}}

==Explanation==
{{incomplete|Created by MAXWELL'S DEMON - Please change this comment when editing this page. Do NOT roll away this tag too soon.}}
A {{w|Rube Goldberg machine}} is a fancifully complex system (either real or imagined), which makes use of an overly elaborate chain of actions. The name comes from an American cartoonist who was one of those who became famous for depicting convoluted and outlandish processes for accomplishing simple tasks.

There's a long history of people building actual contraptions along these lines. Such devices are almost never intended for practical purposes, but exist entirely for entertainment, and as an exercise in building complex and carefully planned systems. This has become particularly common in the internet age, as videos of particularly interesting examples can gain popularity online. The most common category of these systems is probably the marble run (also known as a {{w|rolling ball sculpture}}), in which the goal of the system is to move one or more balls or marbles from the beginning of the arrangement to the end in interesting ways. This contrasts to the {{w|Domino toppling|domino run}} where motions are transferred by many intermediate pieces painstakingly arranged, although both aspects are commonly combined in such contrivances.

When [[Megan]] tries to show [[Cueball]] an example of such a video, he refuses, not because he lacks interest, but because of how he predicts it will impact him. Cueball (likely as a stand-in for [[Randall]]), has sufficiently strong interest in things like designing, building and engineering complexity that he's certain he will eventually adopt building such systems as a hobby, and that it will dominate his time and attention. Accordingly, he appears to be deliberately delaying his exposure to them so that he can continue to pursue other hobbies, with the assumption that he will eventually succumb to this one.

Megan responds that he knows where he's going, but is taking "a really interesting and circuitous path" to get there. This draws a parallel between the type of systems he's avoiding and his approach to life more generally.

The title text mentions specific ideas Cueball plans to incorporate into such a device.

A {{w|Galton board}} is a device that distributes falling balls into a {{w|normal distribution}}. Its design is similar to those used in {{w|pachinko}}-style games.

A Ranque-Hilsch {{w|Vortex tube}} is a device for separating compressed gas into hot and cold streams. While such a device isn't directly applicable to marbles, one can imagine using the principle to separate a stream of marbles based on speed.

Pinball bouncers are properly supposed to be the {{w|Pinball#Bumpers|Bumpers}} in {{w|Pinball}} machines. In Randall's marble run there will be a compartment where the walls are lined with these bumpers. Supposedly there will be many marbles on the floor of this segment of the run, which will hit these bumpers and get a kick so they will move fast and randomly around the compartment, which is where the Demon comes in.

{{w|Maxwell's Demon}} is a thought experiment by James Clerk Maxwell which would violate the Second Law of Thermodynamics. Maxwell proposed that, if a container of air was separated by a divider, with a door that allowed only one molecule through at a time, and a theoretical "demon" were to control the door to sort high-energy atoms into one side and low energy atoms into the other, the two sides would develop a temperature difference with no energy input. The problems are many: first of all, how would the door open and close without using energy; and how would the demon gain knowledge of the speed and position of all the molecules, particularly at the same time, in violation of Heisenberg's {{w|uncertainty principle}}?

Randall's version of this apparently involves a large number of marbles bouncing around inside the bouncer-lined compartment, with an automated system to divert the fastest moving marbles into one side, and the slowest moving into the other. As these are macroscopic scales this would not be impossible, just really difficult. It would be interesting to see the result, but if it was possible to construct the device, soon one segment would have slow moving balls and the other lots of fast moving balls. Randall foresees the amount of time he might use if he first began trying to construct his ideas into a marble run.

Knowing Randall and his fans, some might design something using his ideas from this comic.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[Megan is walking towards Cueball and showing her phone. Cueball holds a hand to his face and looks away.]
:Megan: Check out this cool video of a Rube Goldberg marble run.
:Cueball: No! Not yet.

:[Megan has lowered her phone. Cueball has his hand in a fist.]
:Cueball: I've always known I'm doomed to eventually become one of those people who builds elaborate marble runs in their garage.
:Cueball: I can feel the pull.
:Cueball: So satisfying.

:[Close-up on Cueball.]
:Cueball: I just want to do as many other things as I can before I give in and disappear into that world.

:[Megan and Cueball are walking.]
:Megan: So you know where you're going to end up, but you're trying to take a really interesting and circuitous path to get there.
:Cueball: Exactly. Bounce around, maybe go off a few jumps.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Physics]]
[[Category:Statistics]]

2785: Marble Run

2023-06-07T13:46:27Z

172.70.91.161: /* Explanation */

{{comic
| number = 2785
| date = June 5, 2023
| title = Marble Run
| image = marble_run_2x.png
| imagesize = 438x512px
| noexpand = true
| titletext = I have so many plans. It would incorporate a Galton board, a Ranque-Hilsch marble vortex tube, and a compartment lined with pinball bouncers with a camera-and-servo Maxwell's Demon that separated the balls into fast and slow sides.
}}

==Explanation==
{{incomplete|Created by MAXWELL'S DEMON - Please change this comment when editing this page. Do NOT roll away this tag too soon.}}
A {{w|Rube Goldberg machine}} is a fancifully complex system (either real or imagined), which makes use of an overly elaborate chain of actions. The name comes from an American cartoonist who was one of those who became famous for depicting convoluted and outlandish processes for accomplishing simple tasks.

There's a long history of people building actual contraptions along these lines. Such devices are almost never intended for practical purposes, but exist entirely for entertainment, and as an exercise in building complex and carefully planned systems. This has become particularly common in the internet age, as videos of particularly interesting examples can gain popularity online. The most common category of these systems is probably the marble run (also known as a {{w|rolling ball sculpture}}), in which the goal of the system is to move one or more balls or marbles from the beginning of the arrangement to the end in interesting ways. This contrasts to the {{w|Domino toppling|domino run}} where motions are transferred by many intermediate pieces painstakingly arranged, although both aspects are commonly combined in such contrivances.

When [[Megan]] tries to show [[Cueball]] an example of such a video, he refuses, not because he lacks interest, but because of how he predicts it will impact him. Cueball (likely as a stand-in for [[Randall]]), has sufficiently strong interest in things like designing, building and engineering complexity that he's certain he will eventually adopt building such systems as a hobby, and that it will dominate his time and attention. Accordingly, he appears to be deliberately delaying his exposure to them so that he can continue to pursue other hobbies, with the assumption that he will eventually succumb to this one.

Megan responds that he knows where he's going, but is taking "a really interesting and circuitous path" to get there. This draws a parallel between the type of systems he's avoiding and his approach to lif emore generally.

The title text mentions specific ideas Cueball plans to incorporate into such a device.

A {{w|Galton board}} is a device that distributes falling balls into a {{w|normal distribution}}. Its design is similar to those used in {{w|pachinko}}-style games.

A Ranque-Hilsch {{w|Vortex tube}} is a device for separating compressed gas into hot and cold streams. While such a device isn't directly applicable to marbles, one can imagine using the principle to separate a stream of marbles based on speed.

Pinball bouncers are properly supposed to be the {{w|Pinball#Bumpers|Bumpers}} in {{w|Pinball}} machines. In Randall's marble run there will be a compartment where the walls are lined with these bumpers. Supposedly there will be many marbles on the floor of this segment of the run, which will hit these bumpers and get a kick so they will move fast and randomly around the compartment, which is where the Demon comes in.

{{w|Maxwell's Demon}} is a thought experiment by James Clerk Maxwell which would violate the Second Law of Thermodynamics. Maxwell proposed that, if a container of air was separated by a divider, with a door that allowed only one molecule through at a time, and a theoretical "demon" were to control the door to sort high-energy atoms into one side and low energy atoms into the other, the two sides would develop a temperature difference with no energy input. The problems are many: first of all, how would the door open and close without using energy; and how would the demon gain knowledge of the speed and position of all the molecules, particularly at the same time, in violation of Heisenberg's {{w|uncertainty principle}}?

Randall's version of this apparently involves a large number of marbles bouncing around inside the bouncer-lined compartment, with an automated system to divert the fastest moving marbles into one side, and the slowest moving into the other. As these are macroscopic scales this would not be impossible, just really difficult. It would be interesting to see the result, but if it was possible to construct the device, soon one segment would have slow moving balls and the other lots of fast moving balls. Randall foresees the amount of time he might use if he first began trying to construct his ideas into a marble run.

Knowing Randall and his fans, some might design something using his ideas from this comic.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[Megan is walking towards Cueball and showing her phone. Cueball holds a hand to his face and looks away.]
:Megan: Check out this cool video of a Rube Goldberg marble run.
:Cueball: No! Not yet.

:[Megan has lowered her phone. Cueball has his hand in a fist.]
:Cueball: I've always known I'm doomed to eventually become one of those people who builds elaborate marble runs in their garage.
:Cueball: I can feel the pull.
:Cueball: So satisfying.

:[Close-up on Cueball.]
:Cueball: I just want to do as many other things as I can before I give in and disappear into that world.

:[Megan and Cueball are walking.]
:Megan: So you know where you're going to end up, but you're trying to take a really interesting and circuitous path to get there.
:Cueball: Exactly. Bounce around, maybe go off a few jumps.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Physics]]
[[Category:Statistics]]