explain xkcd - User contributions [en]

2803: Geohydrotypography

2023-07-18T14:24:42Z

Markjreed: Correct a small typo, add precision around size of a point.

{{comic
| number = 2803
| date = July 17, 2023
| title = Geohydrotypography
| image = geohydrotypography_2x.png
| imagesize = 339x389px
| noexpand = true
| titletext = The Atlantic is expanding at about 10 ppm (points per month).
}}

==Explanation==
{{incomplete|Created by a Geohydrotypographologist - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This comic is another entry in the "[[:Category:My_Hobby|My Hobby]]" series of comics.

{{w|Plate tectonics}} is the understanding that the Earth's lithosphere is divided up into separate 'plates', which carry the continents and (in the case of the Atlantic) are slowly moving apart under geological action that mostly drives the respective coastlines away from the deep centre of the ocean. Here, Randall explains that if the surface of the Atlantic Ocean were covered in a certain size of printed text (as if its surface were a giant sheet of printed paper, which it is not{{citation needed}}), the shifting of the continents would increase the amount of text by about 100 words per second.

[[Randall]] says that his hobby is geohydrotypography, which is a portmanteau of {{w|geology}}, {{w|hydrology}}, and {{w|typography}}. Basically, it means that his hobby is typing on rocks and ocean.

The title text reports the rate of the ocean's expansion, about 40 millimeters per year, in points per month. A point in typography is 1/72 of an inch, or 127/360 =~ 0.3528 millimeters. The expansion sideways would steadily allow more characters on the first line (and thus intermittently more words, 'unwrapping' the first word seen on the next line) and cascading this effect onto every subsequent line spread out vertically along the roughly 13,000km (depending upon your choice of limits) North/South 'height' of the writing medium.

The exact calculation needs various assumptions. Font families of a given well-defined vertical size/separation can each exhibit varying general widths of character, and be subject to various possible degrees of [[1015: Kerning]] depending upon what precise choice of text is made (unless using a strictly a fixed-width font). Similarly, the word that does (or does not) have to be wrapped at the first line-break can effect which groups of words may (or may not) need to wrap on subsequent lines, in a cascading effect that can create almost chaotic changes from just a single reassessment. The exact extent of the Atlantic Ocean can also be differently interpreted: where it meets the Southern and Arctic oceans, whether to include bordering 'seas', what to do where the 'text' may have to cross/break-across islands (e.g. the Bahamas, Azores, etc, some of these being treated as Atlantic boundaries with the comic's relatively much larger size of "ocean text"), possibly even whether to track the precise tidal inundations at the coastlines at any particular moment (though they should even out, on their twice daily cycle, and high-/low-water marks could be chosen as the standard). All these factors, and more, make it difficult to precisely define the total characters (and thus words) that would 'fit', though the approximate annual increase in the approximate area of the ocean could allow us to assume some approximately greater number of characters (based upon an approximation of their average page-area requirements) which could be divided by the approximate number needed for a general corpus of words (and its spacing) to determine the approximate additional text that could now be added for any given span of time. Knowing Randall, he has used the best approximations that he could find and determined that the possible cumulative errors were not unacceptable.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[A depiction primarily of the Atlantic Ocean and the surrounding land-masses. The land is black, leaving the oceans and seas white except for the following words written in sixteen lines of text (from just below the tip of Greenland/Arctic Ocean down to slightly above the Falkland Islands/Southern Ocean) that are, for the most part, wrapped between the Atlantic coastline 'margins' (as defined by the Americas on the left and Europe/Africa on the right, or significant island groups:]

:If you covered the surface of the Atlantic Ocean with twelve-point printed text, with the lines wrapping at the coasts, the expansion of the ocean basin due to plate tectonics would increase your word count by about 100 words per second.

:[Caption below the panel:]
:My hobby: Geohydrotypography

{{comic discussion}}

[[Category:My Hobby]]
[[Category:Maps]]

Talk:2428: Mars Landing Video

2021-02-23T14:22:49Z

Markjreed: Add comment to discussion.

When I saw "full speed landing" I thought it meant failed landing, as in a 2000-mph rover landing. --[[User:Char Latte49|Char Latte49]] ([[User talk:Char Latte49|talk]]) 19:53, 22 February 2021 (UTC)
: I thought that too. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 07:55, 23 February 2021 (UTC)

Why the specification that the video is full-speed? Did we already have slow motion video of a Mars landing? [[User:Bischoff|Bischoff]] ([[User talk:Bischoff|talk]]) 09:35, 23 February 2021 (UTC)
:full-speed in the context of video usually means 24 to 30 frames per second(FPS) (or 60 fields if interlaced) and slow motion is anything 60fps or faster, but it is the ratio of recording speed to playback speed that matters. Record at 120fps and play back at 30 and you get smooth 1/4 speed slow motion; record at 24fps and play back at 6 and you get a jerky almost stroboscopic effect. The NASA press briefing included a “1/3 speed” video, which implies 75 to 90fps, but for all I could tell they might have simply slowed down the playback of the “full speed” feed. I suspect that prior landings had at best a handful of images that would constitute a playback frame rate of less than 1 per second, and thus would best be described as time lapse.[[Special:Contributions/108.162.219.56|108.162.219.56]] 12:13, 23 February 2021 (UTC)
:I've not been keeping track of what was released when, but it was essentially "a series of stills" (i.e time-lapse, when compiled into a short video) for most(/all?) recent missions. Sometimes at the speed of capture (low-FPS playback), sometimes at a better speed of comprehension (sped up), sometimes possibly a mix (the comet impact/sampling video, I think had notes about it actually being five seconds of contact, but only usable pictures were edjted into the 'flickerbook' view).
:The problem these days is probably more the bandwidth to send captured data back. Hardware and storage are probably capable, these days, as long as all vital science/navigation information can also be bit-shifted alongside the interest-raising videos more tuned to publicity. But once settled down, and while everything mission-critical is now being assessed back home it can probably trickle some HD video back (ready to re-use the memory space, shortly) to let them entertain the masses. ;) [[Special:Contributions/162.158.155.204|162.158.155.204]] 13:07, 23 February 2021 (UTC)
:Maybe some of this information about the "full-speed"ness of the video belongs in the main explanation body? --[[User:Markjreed|Markjreed]] ([[User talk:Markjreed|talk]]) 14:22, 23 February 2021 (UTC)

2428: Mars Landing Video

2021-02-23T14:20:56Z

Markjreed: note that the 11-minute figure is the one-way light speed delay, not round-trip

{{comic
| number = 2428
| date = February 22, 2021
| title = Mars Landing Video
| image = mars_landing_video.png
| titletext = The best part of crashing a Mars briefing is you can get in a full 11 minutes of questions before they can start to respond.
}}

==Explanation==
{{incomplete|Created by THE WORST SKYCRANE. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
This comic plays on the fact that if there is only one of something in a set, that one thing is the most/least in that set by lack of comparison. As there is only one full speed video of a Mars landing, that makes the video the worst one. [[Randall]], who has been [[:Category:Banned from conferences|banned from NASA's conferences]], has decided to crash the conference (literally, see below) solely to ask this question, flouting his ban and embarrassing NASA. He follows up with the question if NASA is planning to make a worse Mars landing video, which is silly because people generally don't intend to make something worse. However, because this video is the worst full-speed video of a Martian landing by virtue of being the only full-speed video of a Martian landing, it is likely that if enough full-speed videos of Martian landings are made in the future, this video will not be the worst forever.

Judging by the sound effects, Randall has chosen to literally crash his way through the conference room roof, using a "skycrane" — a general term for aerial vehicles, similar to standard cranes, that can lower or raise objects.

This comic was published shortly before a [https://www.youtube.com/watch?v=gYQwuYZbA6o NASA press conference] that showed, as mentioned in the comic, the first ever full-speed video of a Mars landing. On Earth one would likely use the {{w|Sikorsky S-64 Skycrane}} helicopter, while NASA used a custom-built skycrane delivery system for the ''Perseverance'' rover. Randall deems using a skycrane to crash a conference about a skycrane very ironic.

The title text refers to the 11-minute (one-way; 23 minutes round-trip) communications delay between Mars and Earth, due to the speed of light and the distance between the planets at the time of the rover's landing. Perseverance mission control must wait this long before they can even begin to respond to anything that happens to the rover, which Randall here twists into an 11-minute delay before they can begin to answer his questions.

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

:[Hairbun is standing on a circular stage in front of a lectern. There is a "Crash" on the top right of the panel, with a voice coming from there.]
:Hairbun: We're excited to share the first ever full-speed video of a Mars landing.

:Off-screen character: ''Crash''
:Off-screen character: Doesn't that mean it's also the ''worst'' ever full-speed video of a mars landing?
:Off-screen character: Do you expect that record to stand forever, or is NASA working on a worse one?

:[Caption below the comic]:
:NASA tried to ban me from their press briefings, but ironically their security was totally unprepared to deal with a skycrane.

{{comic discussion}}
[[Category:Banned from conferences]]
[[Category:Mars rovers]]
[[Category:Comics featuring Hairbun]]