explain xkcd - User contributions [en]

3097: Bridge Types

2025-06-03T14:30:53Z

162.158.41.44:

{{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. At first glance, the joke lies in the progression of bridge types from simple to realistically complex to totally bogus.

{| 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 (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}}. Many bridges in this category suffer severe cost overruns. 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]
|Such a bridge exists at the {{w|Fort de Roovere}} in Halsteren, Netherlands. The bridge in the comic might still require stairs. 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].
|-
|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]
|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. 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]]

User:FaviFake

2025-02-24T17:14:22Z

162.158.41.44:

<big>{{TOC}}</big>'''Hey everyone! I got in touch with [[Randall Munroe]] himself!! Here's what you need to know.'''

I emailed him to ask for the official release date of [[36: Scientists]] (see [[36: Scientists#Trivia|the trivia for more info]]). Surprisingly, he got back to me! You can read the conversation, with a summary of his messages, below. I'll keep you posted if I receive more messages! You can [https://www.explainxkcd.com/wiki/index.php?title=User:FaviFake&action=watch add this page to your watchlist] to keep track of it. I haven't received his explicit permission to feature his messages in full, so it seemed ethical to hide his messages. My emails have not been altered, but in the copy-pasting, links have been removed. These emails were all hyperlinked, I now added back only a few links. The reason I waited a few days before publishing them is because I was very busy.

In his last email, Randall expressed willingness to answer a few more questions, particularly simpler, administrative questions (like the one he answered already), but kindly explained he prefers to avoid too much meta-commentary. Because I didn't want to come up with every question and I wanted to hear everyone, I'll try to send him some that you want, if he agrees to receiving more! You can [[#Your suggestions! What should I ask?|add your suggestions here!]].

===Email thread===
{| class="wikitable"
|'''Question from the Explain xkcd wiki regarding one of your comics'''
Email thread - 4 messages —
Here's a [https://imgur.com/a/2StTkvJ screenshot of one of the emails], if you need some sort of proof.
|}

{| class="wikitable"
|'''FaviFake''' <[email redacted]@gmail.com>
|14 February 2025 at 19:16 CET
|-
| colspan="2" |To: Randall Munroe <[Randall's email redacted]@gmail.com>
|-
| colspan="2" |

Hi,
I'm an editor at explainxkcd.com, which you probably know is the wiki that explains all your comics and provides as much info as possible on them.
{| class="wikitable"
|''[In the copy-pasting, links have been removed. These emails were all hyperlinked, I now added back only a few links.]''
|}
In pursuit of that goal, we have always had an unsolved mystery only you can solve. Comic [[36: Scientists]] was originally posted as a duplicate of comic [[10: Pi Equals]]. You corrected this sometime between April 23, 2006 and July 5, 2006 , when the current version showed up in the web archive (see the two links). The comic looks like one of your old drawings.

So, explain xkcd thinks that when you realized your mistake (over three months after it was originally posted), you probably found an old unused drawing and posted it, to not make it stand out compared to the other comics from that time. This all means we have no date for this comic, since it could've been posted anytime between the two dates mentioned above. You can read more about this here. (If you're interested, we have a more comprehensive history of your webcomic here.)

Could you kindly help us figure this out by checking when you released comic #[[36]], so we can add an official date to it? This is one of the only official comics which we don't know the date of.

Kind regards,

FaviFake

editor @ explain xkcd
|}
{| class="wikitable"
|'''Randall Munroe''' [Randall's email redacted]
|14 February 2025 at 22:20 CET
|-
| colspan="2" |To: FaviFake <[email redacted]@gmail.com>
|-
| colspan="2" |FaviFake,
{| class="wikitable"
|''[Randall replies, giving the official date when [[36: Scientists]] was swapped: April 28th.]''
''[He ends with:]''
|}
Thank you for your tireless documentation effort :)
{| class="wikitable"
|''[He signs]''
|}
[Quoted text hidden]
|}
{| class="wikitable"
|'''FaviFake''' <[email redacted]@gmail.com>
|15 February 2025 at 17:39 CET
|-
| colspan="2" |To: Randall Munroe <[Randall's email redacted]@gmail.com>
|-
| colspan="2" |Hello Randall,

Thank you so much for your response!! I'm certain the rest of the community will be thrilled to have an official answer.

Unfortunately, this is by far not the only "unsolved mystery" we have encountered in our research of your comic. Because we don't get to talk to you very often, I'd like to ask you if you can answer more of our many questions, if you're up for it. Of course, I do not want to annoy you or waste your time, so please let me know if this is something you'd enjoy! I will try to keep the questions entertaining for you.

Kind regards,

FaviFake

[Quoted text hidden]
|}
{| class="wikitable"
|'''Randall Munroe''' <[Randall's email redacted]@gmail.com>
|17 February 2025 at 19:02 CET
|-
| colspan="2" |To: FaviFake <[email redacted]@gmail.com>
|-
| colspan="2" |FaviFake,
{| class="wikitable"
|''[He expresses willingness to answer some additional questions, particularly simpler, administrative questions (like the one he answered), but kindly explains he prefers to avoid too much meta-commentary]''
''[He ends with:]''
|}
And seriously, my heartfelt thanks to you and everyone there. It's such a privilege to make something that people think is worth so much effort to explain <3

—Randall

[Quoted text hidden]
|}

{| class="wikitable"
|'''FaviFake''' <[email redacted]@gmail.com>
|20 February 2025 at 18:07
|-
| colspan="2" |To: Randall Munroe <[Randall's email redacted]@gmail.com>
|-
| colspan="2" |Randall,

Thank you for the kind words!! I really appreciate the offer. Next time, I'm thinking of asking the community for other simple and administrative questions, because I'm sure I don't represent everyone.
{| class="wikitable"
|''I also asked for his permission to feature this conversation here:''
|}
(Also, would it be okay to feature your responses on our wiki?)

I had drafted the paragraphs below in advance and I'm not sure if they fall outside the boundaries you mentioned, but I figured I’d ask anyway since this is a topic the other editors are very curious about. Of course, no worries if you’d rather not get into the details! We have plenty of simpler questions we can't answer ourselves. Here you go:

On June 17, 2009, you released [[Conservation]] (along with IBM's accompanying blog post), the first comic created with IBM for their "A Smarter Planet" blog. You used the filename conservation.png, as usual. On August 11, 2009, the second comic of the series, [[Prescriptions]], was released (with its blog post), but this time you used an unusual filename: ibm_hc_1.png.

We initially believed these were the only comics you created, mainly because they were the only ones featured on your page xkcd.com/asmarterplanet, but a little over a month ago we discovered two additional never-before-seen comics by experimenting with the image URLs for [[ibm_hc_2]].png and [[ibm_hc_3]].png. We believe you created these two comics as part of the IBM partnership, but for some reason they were never released publicly and were only accessible from imgs.xkcd.com. (Interestingly enough, they are still available!)

Any additional info you can give us would help a ton! For example: their titles, when they were drawn or supposed to be released, or why they were never officially published. Thank you!

—FaviFake
|}
===What I think I should reply back===
*I first asked for permission to make the conversation public, so you all can read what he said. I wasn't told not to make it public, I just think I should ask for permission first. I'm not even sure if this was the right thing. If you have thoughts, [[User talk:FaviFake#Contacting Randall Munroe|please send them to me on my talk page]]!
*I didn't think it was fair to do everything myself, so I wanted to also hear what you wanted to ask! Randall asked for simpler, administrative questions (like the one he answered), and not ones that required too much explaining. Please add your suggestions to the section below!
*I think in the first message we should send some of the easiest questions to answer, quick ones like "when was this released", and then we can start to ask slightly more complex (but still administrative) questions.

===Your suggestions! What should I ask?===
{{notice2|Remember, he said only simple questions. I'm assuming he'd like questions similar to the one he replied to(short, sweet, no explaining needed), or questions that shouldn't require him to explain his comic more than he has already done.

'''What's something relatively important that we don't know and that only Randall can answer in a few words?'''}}
{{notice|

Format your suggestions like this:

<nowiki>SUMMARY OF SUGGESTION --~~~~ </nowiki>
<nowiki>:Explain in more detail your suggestion.</nowiki> <nowiki>::Discuss it and vote --~~~~</nowiki>
Add new suggestions below the other ones.}}

{{Done}}'''[[ibm_hc_2]] and [[ibm_hc_3]] (newly-discovered comics) and comic [[36: Scientists]]''' --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 16:34, 21 February 2025 (UTC)
:I asked this one already, because I assume it's the most important one right now. You can [[#Email thread|see my question above]].

'''Why was what if? article ''[https://web.archive.org/web/20161205191559/http://what-if.xkcd.com/153 Peptides] deleted?'' --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 16:34, 21 February 2025 (UTC)'''
:[[what if? (blog)]] is a blog written by [[Randall]] with entries posted occasionally. On December 5, 2016, the article ''[https://web.archive.org/web/20161205191559/http://what-if.xkcd.com/153 Peptides]'' was published as number {{what if|153|153}}. However, it was [https://web.archive.org/web/20161206171630/http://what-if.xkcd.com/153/ removed the following day] and was replaced by a notice: "''Whoops. This article is still in progress. An early draft was unintentionally posted here thanks to Randall's [http://xkcd.com/1597/ troubled approach to git], and it took a little bit to get everything sorted out and rolled back. Sorry for the mixup!"''. No finished version of the article was ever published, and the URL was later reused for ''{{what if|153|Hide the Atmosphere}}''.
::I this this one is very interesting, but it might not be as administrative and short as Randall wants. He'd need to explain the reason why it wasn't published and why it looks like a complete article, not a "draft". Anyone agree? --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 16:34, 21 February 2025 (UTC)
:::Copy paste from my reply below which I wrote first: "I'm not quite sure he likes questions about things he actually wished to delete... I mean seriously he tried to hide it but we got hold of it anyway?" --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 17:26, 23 February 2025 (UTC)

'''What happened to [[Five-Minute Comics: Part 4]]? --[[User:CalibansCreations|'''Caliban''']] ([[User talk:CalibansCreations|talk]]) 17:49, 22 February 2025 (UTC)'''
:A lost xkcd comic. He accidentally posted this instead of [[940]], and then erased all evidence of its existence by redirecting the direct image URL to a notice claiming it was a minor glitch in the universe. I'd get deleting the image outright, but just replacing it with what is essentially a sign to stop looking for it? Kinda weird. Also, how many more of these 5MCs has he made that are potentially lost media?
::I like this one, but I'm not sure if it's as simple as he'd like. He'd need to explain why he created the comic, which he almost never does. But there might be a way to ask it in a way that allows him to reply without revealing too much info. Btw, you seem very active on this wiki, do you have anything else in mind? --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 20:11, 22 February 2025 (UTC)
:::I'm not quite sure he likes questions about things he actually wished to delete... I mean seriously he tried to hide it but we got hold of it anyway? Also we know why he drew these, it was a game he played with family. He just did not mean to post the fourth one. There might be more, but he only posted the three because he could not cope with the cancer of his wife and did not whish to give up his schedule. So as he could not draw three comics fast enough for that week he used these instead. Asking into this would also remind him of his wife's cancer. I vote no to this as an e-mail to Randall! [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 17:24, 23 February 2025 (UTC)

'''Why were the first comics uploaded seemingly randomly? --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 21:51, 22 February 2025 (UTC)
:Initially, randall posted his comics to LiveJournal ([[LiveJournal|learn more here]]). The new xkcd website opened on January 1, 2006, and the backlog of 41 comics from LiveJournal from [[1: Barrel - Part 1]] to [[44: Love]] was transferred on the same day, but in a completely different order. The only comic that has the same number on both sites is [[3: Island (sketch)]], while all the other comics were uploaded seemingly at random. Also, only eleven of the original comic titles were reused of the new site, and even among the last eleven comics posted on both sites, only six used the same title.

'''When was [[Blue Eyes]] released? --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 11:01, 23 February 2025 (UTC)'''
:[[xkcd]]'s [[Blue Eyes]] puzzle is a logic puzzle posted around the same time as comic [[169: Words that End in GRY]]. [[Randall]] calls it "The Hardest Logic Puzzle in the World" on its page, but whether it really is the hardest is up to speculation. This is incorrect, as the comic was available long before October 11, 2006. The earliest date we have is [https://web.archive.org/web/20041024201125/http://68.57.186.221:8080/ October 24th, 2004] (see fourth link on the page), and the earliest version of the comic is from [https://web.archive.org/web/20041109034300/http://68.57.186.221:8080/blue_eyes.html November 4th, 2004]. Additionally, both the puzzle [https://xkcd.com/solution.html and the solution] (here's an [https://web.archive.org/web/20061102070433/https://xkcd.com/solution.html earlier version of the solution])were modified and updated several times since its release.

'''Why are some of the april fools' comics late? - [[Special:Contributions/172.71.146.108|172.71.146.108]] 18:55, 22 February 2025 (UTC)'''
:I'm fairly sure we've had this answered already ("things just weren't quite ready/more testing was needed") for some of the more technical ones, in some other place. Whether we can get more detail and for ''every'' not-on-time might be a matter of him having to remember the precise circumstances. And I also would feel uncomfortable if this turned into "why was <random non-April Fool comic> late?". Or early. (When doing Rightpondian book-tours, sometimes surprisingly early, but every now and then it seems he manages to release them from his native Leftpondia even early here in the Rightpondian day.) But this is far too much detail (and far too much expectation), of no importance so long as he continues to average out at three regular comics a week and ''if he wants to'', and ''when he can'', anything a bit more special.
:Consider this a downvote on bothering him with this question, but that's of course only my opinion, in leiu of anything more constructive to add ("What's your favourite cheese..?") [[Special:Contributions/172.69.79.190|172.69.79.190]] 19:42, 22 February 2025 (UTC)

::I agree with the second IP on this one! Unless there's a particular comic for which the delay was very important (do you have any in mind?), I don't think this is going to be of much interest to him. --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 20:11, 22 February 2025 (UTC)

'''Will we get more 5-part sagas? --[[User:CalibansCreations|'''Caliban''']] ([[User talk:CalibansCreations|talk]]) 11:44, 23 February 2025 (UTC)'''
:Like [[Choices]], [[The Race]], etc.

'''What happened to the transcripts in the JSON interface'''
:On the [https://xkcd.com/about/ about] page of xkcd there is a description of where:
Is there an interface for automated systems to access comics and metadata?
:Read more here [[Transcript]]. And on this page there is a [[Transcript#End%20of%20transcripts|description]] about how the json info got messed up after [[1608: Hoverboard]] and how they completely ended after [[1677: Contrails]] which had the transcript of [[1674: Adult]].
:I would like to know if he noticed the messed up order of the transcript and if that was why he choose to end it completely? --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 17:38, 23 February 2025 (UTC)

'''Just wanted to note that some geography comics might be worth asking about '''
:I remember browsing pages on this wiki about 6 months ago and noticing that there were many explainations of maps or map like things where editors weren't sure which small islands or small countries since comic drawing is obviously not perfect. I don't remember which comics exactly and don't have time today to investigate, but I figured this observation is worth noting. [[User:XKCD Teaches Science|XKCD Teaches Science]] ([[User talk:XKCD Teaches Science|talk]]) 03:27, 24 February 2025 (UTC)

''' Machine details '''
:Is {{https://xkcd.com/2917|Machine}} going to have a finalized state? If so, when? -- [[User:HyperBirbN3rd|HyperBirbN3rd]]

'''Why was No One Was Hurt replaced?'''
:No One Was Hurt was a comic that was replaced by Comic 2642: https://www.explainxkcd.com/wiki/index.php/No_One_Was_Hurt, and while it's reasonable to assume that it's probably in response to some...unfortunate irl events, for documentation it would be nice to have an official, confirmed answer [[Special:Contributions/172.68.71.112|172.68.71.112]] 15:44, 24 February 2025 (UTC)

why has there not been any new what if since comet ice
.
::Discuss it and vote --[[Special:Contributions/162.158.41.44|162.158.41.44]] 17:14, 24 February 2025 (UTC)