explain xkcd - User contributions [en]

3087: Pascal's Law

2025-05-09T22:09:17Z

104.23.187.224: /* Explanation */ Add Ruina montium wikipedia link

{{comic
| number = 3087
| date = May 9, 2025
| title = Pascal's Law
| image = pascals_law_2x.png
| imagesize = 400x459px
| noexpand = true
| titletext = Reductio ad absurdum fails when reality is absurd.
}}

==Explanation==
{{incomplete|This page was created by PASCAL’S HYDRAULIC PRESS. Don't remove this notice too soon.}}

{{w|Pascal's law}} is a principle of fluid mechanics that states that when a change in pressure occurs in confined incompressible fluid, it is transmitted throughout the fluid and the same change occurs everywhere. It was discovered by mathematician {{w|Blaise Pascal}} in 1653 and published a decade later.

{{w|Ruina montium}} was an ancient roman mining technique.

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}

No, that can't be right.

If hydrostatic pressure worked that way, then you could use it to make machines that exert near-infinite force.

And ancient people could have demolished entire mountains just by drilling small tunnels and filling them with water.

When I first learned about Pascal's law, I tried to disprove it by showing that it would lead to absurd consequences, but it turns out hydraulic presses and ruina montium are both real things.

{{comic discussion}}<noinclude>

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Talk:3084: Unstoppable Force and Immovable Object

2025-05-04T16:42:17Z

104.23.187.224: Another result - bomb.

lol, i remember this explanation from a minutephysics video. however, the version of the problem i heard, which is actually paradoxical, is "what happens when an immovable object meets an '''irresistible''' force?" [[User:Not without text|Not without text]] ([[User talk:Not without text|talk]]) 00:03, 3 May 2025 (UTC)
:That was also literally my first thought. [[169]], anyone? --[[User:Coconut Galaxy|Coconut Galaxy]] ([[User talk:Coconut Galaxy|talk]]) 05:37, 3 May 2025 (UTC)
:The MinutePhysics video: [https://nebula.tv/videos/minute-physics-immovable-object-vs-unstoppable-force-which-wins/ on Nebula] or [https://youtu.be/9eKc5kgPVrA on YouTube] --[[User:NeatNit|NeatNit]] ([[User talk:NeatNit|talk]]) 09:55, 3 May 2025 (UTC)

Come on, it's just an arrow made of W- bosons, right? [[User:TheTrainsKid|TheTrainsKid]] ([[User talk:TheTrainsKid|talk]]) 03:22, 3 May 2025 (UTC)
Is there no joke here? Is it just the solution? [[User:Broseph|Broseph]] ([[User talk:Broseph|talk]]) 06:52, 3 May 2025 (UTC)

I remember an explanation by Isaac Asimov in one of his books which was like "by definition, an immovable object will not move at all under any force in the universe, and an unstoppable force will move all of the objects in this way" and then explained how the definitions conflicted each other and as such prevented both from being able to register for the hypothetical at the same time [[Special:Contributions/172.64.236.161|172.64.236.161]] 06:55, 3 May 2025 (UTC)

In the first MMO games, collision was a big problem. A player could block a doorway, and nobody else could go through. It was even worse if the player had "follower" characters or pets.
One solution was to have characters automatically "push" stationary characters out of the way, but that caused other problems. Modern MMO's such as World of Warcraft simply allow characters to pass through each other, as depicted in this xkcd comic. Our eyes fool us into "seeing" that two characters somehow slid past each other. [[Special:Contributions/172.68.228.132|172.68.228.132]] 07:29, 3 May 2025 (UTC)
:Our eyes, or the programmers? I don't have that much experience with MMO's but they probably do render it in specific way to make that effect. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 02:59, 4 May 2025 (UTC)

When the two things pass through each other, at the instant where they both occupy exactly the same space, is there one object or two? [[Special:Contributions/162.158.216.159|162.158.216.159]] 08:02, 3 May 2025 (UTC)
:Given that force is not an object, one. Just like there was when they weren't colocated. [[Special:Contributions/172.69.43.220|172.69.43.220]] 08:29, 3 May 2025 (UTC)
::OK, but what about the 'unstoppable force carrying particles' in the title text? [[Special:Contributions/172.69.194.204|172.69.194.204]] 19:00, 3 May 2025 (UTC)
:::I understand it as if a particle interacting with the object counts as 'stopping', in which case an unstoppable force-carrying particle wont have any effect. --[[Special:Contributions/162.158.120.157|162.158.120.157]] 20:40, 3 May 2025 (UTC)

The force could simply go around the object. The object hasn't moved, and the force wasn't stopped. [[User:Rtanenbaum|Rtanenbaum]] ([[User talk:Rtanenbaum|talk]]) 11:17, 3 May 2025 (UTC)

: Redirecting would imply the force could be redirected, allowing us to trap it inside a closed loop, effectively stopping it. [[Special:Contributions/172.70.57.132|172.70.57.132]] 15:38, 3 May 2025 (UTC)

This is like the Chinese saying the spear and the shield. Using this comic, I guess spear wins [[User:Aprilfoolsupdate!|Aprilfoolsupdate!]] ([[User talk:Aprilfoolsupdate!|talk]]) 14:02, 3 May 2025 (UTC)

Gonna be honest, I think this is my least favorite comic of the last 500 or so. It's a solution already given by minutephysics, except with all the perspective about reference frames, and what people actually mean with these terms replaced by a caption with a superiority complex. I suppose it gets pretty hard 3000 comics in, but c'mon.
[[Special:Contributions/172.68.35.83|172.68.35.83]] 19:18, 3 May 2025 (UTC)

:: Ok, as we're giving personal opinions, I can't let it stand. Some might not exactly be total belly-laughs, but I think they each still have something to them and I prefer a mix of tones (and a wider spatter of focuses and treatments) to them all being exactly the same aspect of 'high-humour'. Not that I'd care to rank them, anyway, but I'm nowhere near ready to go off and make disparaging comments as if this site was bitchaboutxkcd.com, or whatever.
:: I won't try to tell you what to think, yourself, though maybe you should just roll with it. If you really don't like a comic, there'll be another along in two or three days. That might be even 'worse', as well as 'better', but then you can be even more unchill about ''that''. [[Special:Contributions/141.101.98.82|141.101.98.82]] 22:45, 3 May 2025 (UTC)

All forces are irresistable. No objects are immovable. If any force acts on any object, the object moves (or deforms). [[Special:Contributions/172.68.84.145|172.68.84.145]] 22:22, 3 May 2025 (UTC)
:Can we not say that Dark Matter, if that's what we imagine it might be, entirely resists the electromagnetic force? (It's one of my possible interpretations of the comic, though without enough hint that it was intended to have me annotate the Explanation accordingly.)
:That said, it's ''unstoppable'' force (and there's are no Cavorite-like forceproof barriers), and it's rather that ''immovable'' objects are awkward to imagine under Relativity and there being no actual preferable frame of reference in the first place. [[Special:Contributions/172.69.195.113|172.69.195.113]] 22:50, 3 May 2025 (UTC)

I would say that, since a force is mass*acceleration, the force cannot yet be stated while passing through the immovable object, because the object have to accelerate to calculate the force. Therefore, the "force" is only potential or kinetic energy at this point.[[Special:Contributions/162.158.127.25|162.158.127.25]] 12:54, 4 May 2025 (UTC)

I would say that nothing happens. If you think of Pressure and immoveable object: An infinite force would acting on an immoveable (think infinite mass) object would lead to no movement at all.
Well, actually a black hole would be created, swallowing up the object and the force. Since the object's further behavior now cannot be seen from outside mass could be reduced anf the black hole could simply evaporate.
Result: Force and objects actual mass would simply be converted into energy, representing a bomb. [[Special:Contributions/104.23.187.224|104.23.187.224]] 16:42, 4 May 2025 (UTC)

3075: Anachronym Challenge

2025-04-13T21:02:51Z

104.23.187.224: /* Explanation */ You can still commonly get 9 irons made of iron and 3 woods made of wood

{{comic
| number = 3075
| date = April 11, 2025
| title = Anachronym Challenge
| image = anachronym_challenge_2x.png
| imagesize = 265x404px
| noexpand = true
| titletext = I have to pay with paper money.
}}

==Explanation==
{{incomplete|The table is incomplete.}}

[[Cueball]] is reading from a shopping list while shopping for groceries. The items on the list are all [https://en.wiktionary.org/wiki/anachronym anachronyms]. The names of the items indicate their material, but they are no longer made from that material.

{| class="wikitable sortable" style="margin-left:0px"
|-
! Item !! Original material !! Original still generally available?!! Actually made with !! Explanation
|-
| {{w|Aluminium foil|Tin foil}} || {{w|Tin}} || {{Yes|[https://www.thermofisher.com/order/catalog/product/044154.RG Yes]}}|| Aluminum || Formerly "tin foil" was made of the metal tin, but aluminum supplanted tin in the early-to-mid 20th century, as aluminum is cheaper and more durable.
|-
| {{w|Sponge (tool)|Sponges}}|| {{w|Sponge|Sea sponges}}, i.e., marine invertebrates in the phylum Porifera ||{{Yes|Yes}}|| Polyester, polyurethane, cellulose || An item commonly used in the kitchen to soak up water. Or bathrooms to wash yourself.
|-
| {{w|Silverware}} || {{w|Silver}} ||{{Yes|Yes, though at greater expense than silverplated or silver-like}}|| Stainless steel || Covers eating utensils, plates and dishes, candlesticks and trophies, which may all these days be electroplated, cupro-nickel alloys or stainless steel.
Possibly intended to only refer to knives, forks and spoons, which are marginally more likely everyday household purchases than the other candidates, though still less so than more disposable versions made of plastic or wood which cannot even be casually mistaken for silver.
|-
| {{w|Linens}} || {{w|Flax}} ||{{Yes|Yes}} || Cotton, hemp, polyester || Commonly in the form of sheets and blankets.
|-
| {{w|Clothes iron|Clothes iron}} || {{w|Iron}} ||{{No|No}}|| Aluminum, stainless steel & plastics || Used as a tool to remove wrinkles in clothing by heating it up. Modern irons are powered, but traditional irons needed to be heated.
|-
| {{w|Ironing board|Ironing board}} || Wooden board ||{{Yes|Yes}}|| Metal, fabric cover || Flat surface for ironing clothes. It could also refer to how ironing board is not made from iron.
|-
| {{w|Corrective_lens#Reading_glasses|Reading glasses}} || {{w|Glass}} ||{{Yes|Yes}}|| Optical plastics || Used to assist farsighted people with focusing on things up close. Also traditionally made with glass, but nowadays made with CR-39 plastic due to glass's danger of shattering and higher weight.
|-
| {{w|Iron (golf)#Short irons|9 iron}} || Iron ||{{Yes|Yes}}|| Cast {{w|stainless steel}}, {{w|carbon steel}} || A type of golf club.
|-
| {{w|Wood (golf)|3 wood}}|| Wood ||{{Yes|Yes}}|| Titanium, carbon fiber || A type of golf club.
|-
| {{w|Sidewalk chalk|Sidewalk chalk}}|| {{w|Calcite}} chalk ||{{No|No}}|| Calcium sulfate ({{w|gypsum}}) || Used for making marks on pavement or rocks. (e.g., for entertainment, for temporary signs or indicators).
|-
| {{w|Rubber duck|Rubber duck}} || {{w|Rubber}} || {{No|No}} || Vinyl plastics || A children's bath toy. Also used in {{w|Friendly Floatees spill| science}} and {{w|Rubber duck debugging| programming}}.
|-
| {{w|Paper money|Paper money}} (title text) || Paper ||{{Yes|Yes, but usually {{w|cotton paper}}}}|| Cotton, linen fibers (U.S. note), polypropylene. ||
|}

Many of the objects listed on Cueball's shopping list can still be made with the materials that they are named after. Silverware can be made of sterling silver, especially in the cutlery of high-end establishments{{acn}}, but, unlike steel, traditional pure silver requires continued polishing to retain its finish. Cleaning sponges made of sea sponges are expensive, but can be [https://tofinosoapcompany.com/products/natural-sea-sponge-sustainably-harvested purchased]. Linens made from flax are still common some people even consider [https://www.roughlinen.com/en-ca/blogs/newsletters/linen-vs-flax whether flax is the better material]. Some wood clubs are still made from wood, specifically {{w|persimmon}}. {{w|Banknotes of the Japanese yen}} are [https://www.npb.go.jp/en/products/intro/tokutyou.html still made] from wood fiber from ''E. chrysantha'' and abaca pulp. Most of the traditional items can be found in antique sales at least occasionally, and some people still use them such as in communities that have separated from modern industry.

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

:[Cueball is looking at a phone, or perhaps a piece of paper, in his hand while holding his other hand on the handle of a shopping cart. Above the shopping cart, an underlined header and a bullet list are shown:]
:<u>Shopping List</u>
:* Tin Foil
:* Sponges
:* Silverware
:* Linens
:* Iron & Ironing Board
:* Reading Glasses
:* 9 Iron & 3 Wood
:* Sidewalk Chalk
:* Rubber Duck

:[Caption below the panel:]
:I'm trying to do a shopping trip where I only buy stuff that's no longer made from the material it's named after.

{{comic discussion}}

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