explain xkcd - User contributions [en]

3097: Bridge Types

2025-06-03T15:21:00Z

108.162.216.159: /* Explanation */

{{comic
| number = 3097
| date = June 2, 2025
| title = Bridge Types
| image = bridge_types_2x.png
| imagesize = 740x581px
| noexpand = true
| titletext = Pontoon bridges are just linear open-sided waterbeds.
}}

==Explanation==
{{incomplete|This page was recently created by a TESSERACT BRIDGE ABUTMENT. Don't remove this notice too soon.}}
This comic shows, in a four-by-four grid of images, a series of bridge types. The first two rows of images are of authentic bridge types, whereas those in the last two rows are progressively more absurd, although real-life examples of some of them exist, as shown in the table below. The joke lies in the progression of bridge types from the simple and straightforward to the complex and ridiculous.

{| class="wikitable"
!Label
!style="width:7em;"|Status
!Type
!Notes
|-
|Plank
|Real
|{{w|Beam bridge}}
|A straightforward piece of solid material (in this case, made of solid wood, but there are {{w|Clapper bridge|other materials}}) is the most basic form of bridge, and generally the easiest to construct, but also the weakest. Consequently, such bridges are only suitable for small spans and light weights (such as a footbridge over a stream).
|-
|Rope
|Real
|{{w|Simple suspension bridge}}
|Rope bridges consist of several lengths of rope anchored on both sides of the span. Typically, one or more ropes will be intended to support the crossing load (possibly with boards or some other walkway between them), and additional ropes will act as handrails, reducing the risk of falling. These are typically only intended for foot traffic, due to their light construction and lack of rigidity. Because of the simple materials and relative ease of construction, they're often used as improvised bridges.
|-
|Truss
|Real
|{{w|Truss bridge}}
|A truss is a common type of framework consisting of supports connected in a series of triangles which provide support for a load. This design provides significant strength and rigidity with minimal material and weight. A truss bridge can either have the truss above the bridge platform (as in the drawing) or underneath it (also known as a deck truss). This is the first bridge type on this list which is commonly used for vehicle traffic.
|-
|Trestle
|Real
|{{w|Trestle bridge}}
|A trestle bridge is held up by supports reaching all the way to the ground beneath. Typically at least some of the supports will slope outward to give a larger base of support. Once common for railroads, these are less popular nowadays, but are still seen in certain areas and applications.
|-
|Arch
|Real
|{{w|Arch bridge}}
|Arches are one of the oldest kinds of bridges for carrying significant loads. They can be made out of rock or metal. Each span consists of an arch resting on supports. Simple arch bridges rest on both sides of a river or other gap, but longer bridges (as in the drawing) will have intermediate pillars to support multiple arches. The arches distribute the load, allowing a relatively small number of pillar to support weight across the entire deck of the bridge.
|-
|Suspended Arch
|Real
|{{w|Tied-arch bridge}}
|Tied arch bridges use a similar concept as arch bridges, but the arch is instead positioned overhead, with the deck supported by suspended cables. Such bridges may use a single arch (as in the drawing) or multiple arches in succession.
|-
|Draw
|Real
|{{w|Drawbridge}}
|Drawbridges are used to allow ships to pass through obstacles like bridges. They use a cable to pull up one or both sides of the bridge to create enough height clearance for vessels to pass through.
|-
|Suspension
|Real
|{{w|Suspension bridge}}
|A suspension bridge suspends its deck with cables or rods from a cable linked to a pillar and a point a certain distance from each pillar
|-
|Filler
|Real method of maintaining {{w|Grade (slope)|grade}}, not really a 'bridge'
|{{w|Embankment (earthworks)|Embankment}}, {{w|Causeway}} or even a {{w|Dam}}
|Serves the purpose of allowing travel across the gap, but by removing (or {{w|Culvert|mostly removing}}) passage through the gap itself. By filling the gap with hard, irregular material (most commonly rocks), support can be provided, while still allowing water to flow through the gaps. Due to the generally small size of the gaps, generally only slow-flowing water can reliably get through.
|-
|Budget Overrun
|Real<br/>(with an absurd name)
|{{w|Cable-stayed bridge}}
|Specifically, the pictured bridge is a {{w|cantilever spar cable-stayed bridge}}, similar in appearance to the {{w|Samuel Beckett Bridge}} in Dublin. Many bridges in this category suffer severe cost overruns.<br/>Randall may be drawing upon his local knowledge of the {{w|Leonard P. Zakim Bunker Hill Memorial Bridge|Zakim Bridge}} in downtown Boston's {{w|Big Dig}}, also strongly associated with cost overruns.
|-
|Jump
|Not real
|N/A
|A "bridge" that looks like it belongs in a skatepark. Iconically featured in {{w|The Dukes of Hazzard}} TV show.
|-
|Halfhearted
|Real
|[https://www.archdaily.com/184921/moses-bridge-road-architecten Moses bridge]
|The diagram shows that there was barely any attempt to bridge the gap in the landscape at all, just take the 'deck' down into it and back up out again. The concept may have been inspired, in part, by [https://www.fastcompany.com/90186315/the-strange-art-of-the-melting-bridges-of-google-earth an artifact in Google Earth software].
Bridge exist, at the {{w|Fort de Roovere}} in Halsteren, Netherlands and elsewhere, that resemble this 'solution', though these would have involved much thought and commitment in their building, possibly more 'hearted', even, than any more conventional bridge design, especially in the provision of stairs to allow easier ingress/egress (at least for foot traffic) than in the comic's version.
|-
|Waterbed
|Not a bridge
|{{w|Waterbed}}
|Rather than a bridge, it is more like another version of a causeway (see 'Filler') using trapped water to maintain the upper surface.
Named for a 'mattress' type, which is usually a raised surface ''on top of'' a piece of bedframe, with an unusual approach to padding and comfort.
|-
|L'Engle
|Not real
|[https://www.refinery29.com/en-us/2018/03/192728/tesseract-definition-wrinkle-in-time-space-dimension Tesseract AWIT]<br>not {{w|Tesseract|Tesseract (geometry)}}
|References {{w|A Wrinkle In Time}} by Madeleine L'Engle. Characters cross great distances by "tessering", moving via a tesseract through a higher dimension which essentially brings the two ends of the journey together from the perspective of the traveler.<br/>The image shows the two ends of the gap being brought together, with the gap apparently crumpled in between them.
|-
|Fun
|Not real
|
|It is a loop-de-loop, possible allusion to [[2935: Ocean Loop]].
|-
|Repurposed Elevator
|Real, but not as displayed
|Horizontal elevator / {{w|People mover|People mover}}
|There are various implementations of such designs, the best-known one is probably the {{w|Schmid Peoplemover|Schmid Peoplemover}}.
However, unlike a regular people mover, where the door stays upright, the image shows a regular elevator that has been rotated 90 degrees.
|-
|''(Title text)''
|Real
|{{w|Pontoon bridge}}
|Pontoon bridges are described as a series of fictitious "waterbed bridges", as shown above, but constructed without sides. This would mean that that the 'bed'-supporting water flows in one side and out the other, if there is any passage or tidal flow of water. It may technically mean that you cannot cross {{w|The Same River Twice|the same bridge twice}}.
Pontoons rely upon buoyancy, either of the whole deck or distinct floating elements, whereas an enclosed "waterbed" bridge would rely upon the strength of the membrane to keep the mass of water within it, and thus the deck above that mass.
|}

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

:[A 4x4 matrix of 16 ways to cross the same rectangular hole in the ground]

:Plank [shows a plank laid over the hole]

:Rope [shows a rope bridge with rope guardrail]

:Truss [shows a truss bridge with a triangular truss above the bridge deck]

:Trestle [shows a trestle bridge]

:Arch [shows stone arches supporting a straight deck]

:Suspended Arch [shows a single arch, with the bridge deck suspended from it]

:Draw [shows a truss bridge, with one half opened like an unrealistic draw bridge]

:Suspension [shows the bridge deck suspended from a cable strung between two pillars and the shores]

:Filler [shows the hole filled with dirt and stones]

:Budget Overrun [shows a bridge deck suspended by cables from an artistically shaped pillar]

:Jump [shows two ramps at the edges of the hole, and a skateboarder jumping across the hole]

:Halfhearted [shows a ramp at each side of the hole that leads down to the bottom]

:Waterbed [shows the hole filled with water, two fish and an octopus, a wobbly covering, and two stick figures crossing]

:L'Engle [shows the hole warped such that the opposite shores meet]

:Fun [shows a loop-de-loop rollercoaster bridging the hole, and a skateboarder using it to get across]

:Repurposed Elevator [shows an elevator tower, rotated sideways as a whole, laid across the hole. 2 stick figures using the elevator are also rotated.]

{{comic discussion}}<noinclude>

[[Category:Engineering]]
[[Category:Comics featuring Cueball]]
[[Category:Multiple Cueballs]]
[[Category:Animals]]

Talk:2740: Square Packing

2023-02-21T23:33:54Z

108.162.216.159:

I suspect Randall saw the same social media post that I did (or maybe a repost of the same social media post, who knows or cares). I don't really want to make an explanation, but anyone who does, here's a link to a bunch of square packing findings... of course, no hydraulic press allowed for these packings. https://erich-friedman.github.io/packing/squinsqu/ [[User:Tsumikiminiwa|Tsumikiminiwa]] ([[User talk:Tsumikiminiwa|talk]]) 22:07, 20 February 2023 (UTC)

:Yeah, this was on r/mathmemes the other day. [[Special:Contributions/172.64.238.48|172.64.238.48]] 00:03, 21 February 2023 (UTC)

Welcome to the Hydraulic Press Channel. Today we have a set of squares that are usually used in packing problems. You are supposed to fit them into other squares by arranging them. But I think we can get them to fit easier if we put them on the press, and just try to make them smaller. We are going to start with one square, and see how much smaller we can make this. And here we go.

:Needs to include a mention of the "Square Packer Five Meeellion"... [[Special:Contributions/172.68.51.141|172.68.51.141]] 16:48, 21 February 2023 (UTC)

The post where I saw this said: “God is dead, and what killed him was learning [the similarly inelegant-appearing n=17 solution].” [[Special:Contributions/172.70.254.216|172.70.254.216]] 13:08, 21 February 2023 (UTC)

[[Special:Contributions/172.70.54.77|172.70.54.77]] 19:26, 21 February 2023 (UTC)
Welcome to the Hydraulic Press channel

What does "s<" mean? [[User:Kev|Kev]] ([[User talk:Kev|talk]]) 22:54, 21 February 2023 (UTC)
:"S" (the size of the square, within which lie the N small squares) is less than the following number. i.e. that any S of that amount or greater is more than enough space to contain N unit squares. But it isn't fully established what the ''smallest'' value of S is, just that it will not be bigger than (or equal to) that provisional limit.
:(Do we need a wikilink to inequality notation in the explanation, then? Maybe you can tell us, Kev.) [[Special:Contributions/172.71.242.191|172.71.242.191]] 23:17, 21 February 2023 (UTC)

I think I saw this new solution in a paper authored by USPS et al. [[Special:Contributions/108.162.216.159|108.162.216.159]] 23:33, 21 February 2023 (UTC)

Talk:2622: Angular Diameter Turnaround

2022-05-20T23:23:38Z

108.162.216.159:

Slightly creepy, NGL[[Special:Contributions/172.69.34.10|172.69.34.10]]
: Warning, horrible content: The universe was created by the severed bloody hands of google employees convincing phone manufacturers to ditch the previous phone backends and explode the google play store throughout reality in a mess of intergalactic gore. Our planet developed from an angrybirds download, nourished by the decaying corpse of the owner who played it all their life. [[Special:Contributions/172.70.110.209|172.70.110.209]] 20:37, 20 May 2022 (UTC)

So apparently this is a real thing, which I never knew [[wikipedia:Angular_diameter_distance#Turnover_Point]] [[Special:Contributions/108.162.221.81|108.162.221.81]] 20:46, 20 May 2022 (UTC)

Could be related to comic 1422, what with both containing expanding phones analogous to some cosmic structure. [[Special:Contributions/172.70.130.105|172.70.130.105]] 21:46, 20 May 2022 (UTC)
:[[1422]] has been crapped. [[Special:Contributions/172.70.126.221|172.70.126.221]] 21:50, 20 May 2022 (UTC)

So confusing…I thought that 13 billion years ago they had flip phones. [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 22:32, 20 May 2022 (UTC)

Before this explanation is marked “complete” it had better mention that “sinking into dilute blood” is a terrible (one could even say ignorant or stupid) description of red shift, completely missing the fundamental cause and completely distorting the effect. [[Special:Contributions/108.162.216.159|108.162.216.159]] 23:23, 20 May 2022 (UTC)

== Hooray! ==

Something good is happening!!!!!! [[Special:Contributions/172.70.126.215|172.70.126.215]] 21:22, 20 May 2022 (UTC)

2621: Mainly Known For

2022-05-19T05:26:31Z

108.162.216.159: /* Explanation */ "Starman" was not even a top 40 hit in the U.S.

{{comic
| number = 2621
| date = May 18, 2022
| title = Mainly Known For
| image = mainly_known_for.png
| titletext = Oh sure, I know Keira Knightly, from the first movie in that series by The Land Before Time producer. You know, the franchise with the guy from Jurassic Park and Ghostwriter, and script work by Billie Lourd's mom?
}}

==Explanation==
{{incomplete|Created by that guy from NASA, what was his name? Something Munroe - Do NOT delete this tag too soon.}}

Megan points out an uncanny resemblance between her friend's dad and {{w|Steve Jobs}}. However, she has trouble remembering Jobs's name. Frequently, when people can't remember a celebrity's name, they will point out other works they are known for in hopes someone else will recognize them from that and remind them of the name{{citation needed}}. While these associations are often prone to the {{w|Mandela effect}}, Megan's information about the celebrities is, in fact correct, but apparently not what those people are best known for.

Megan refers to Jobs as "the Pixar guy". Jobs is mainly known for (hence the comic's title) being the co-founder and twice CEO of {{w|Apple Inc.|Apple Computer}}, but in the late 1980s and early 1990s (between his stints at Apple), he was the chairman of Pixar Animation Studios, which is what Megan knows him for.

Cueball points out that Megan's tendency to avoid the "main" association and instead go with a much more secondary one is weird, which confuses her. To demonstrate how weird her associations are, Cueball asks her, "Who is {{w|John Lennon}}?" Lennon is a famous songwriter who played and wrote for {{w|The Beatles}} before they broke up, and later continued on a solo music career. Megan recognizes Lennon as a musical artist, but is unable to remember the name of The Beatles. She instead asks about the band he was in with {{w|Ringo Starr}}. Ringo, however, is not mainly memorable to her for his role in The Beatles, but rather as Mr. Conductor from the first season of the 1989 children's television show {{w|Shining Time Station}}. The Beatles' fame seems to have escaped Megan, which vexes Cueball.

Hoping to show that she really does know Lennon and that her associations aren't weird, she points out that she remembers {{w|Fame (David Bowie song)|Fame}}, a 1975 song that he co-wrote with {{w|David Bowie}} and performed backing vocals and guitar on. She is, however, again unable to remember Bowie's name, recognizing him for his acting roles in ''Labyrinth'' and ''Zoolander,'' rather than his more famous musical career (such as his smash hits {{w|Space Oddity}} or {{w|Let's Dance (David Bowie song)|Let's Dance}}).

Sensing Cueball's annoyance, she attempts to excuse herself by saying ''Zoolander'' came out a long time ago, during the {{w|Presidency of George W. Bush}}. ''Zoolander'' was indeed released in 2001. Apparently unable, again, to remember the president's name, she identifies him as "{{w|Jenna Bush}}'s dad". Jenna Bush is a TV personality and much less widely known than her father{{citation needed}}.

The title text refers to the PBS children's series ''Ghostwriter'', previously featured in [[130: Julia Stiles]], which described a scene from the show as "the best thing ever to appear on TV".

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

:Megan: ...And her dad looks ''exactly'' like the Pixar guy. Steve what's-his-name? Jobs?
:Cueball: "Pixar guy"?
:Cueball: You always know famous people for such weird reasons.

:Megan: What do you mean?
:Cueball: Who is John Lennon?
:Megan: Wasn't he in a band? With Ringo from ''Shining Time Station''.
:Cueball: How is ''that'' your main association?

:Megan: I also know he once did a song with the guy from Labyrinth!
:Cueball: You mean David Bowie? I think he's famous for some other stuff, too.

:Megan: Oh yeah, he was also in Zoolander!
:Megan: I forgot that movie, it came out back when Jenna Bush's dad was president.
:[Cueball facepalms]
:Cueball: ''*SIGH*''

{{comic discussion}}