2234: How To Deliver Christmas Presents

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How To Deliver Christmas Presents
Building codes in hurricane zones rely on studies of how easily flying debris can break residential windows. If you're looking for a science fair project idea and you hate your neighbors, I'm sure they could always use more data!
Title text: Building codes in hurricane zones rely on studies of how easily flying debris can break residential windows. If you're looking for a science fair project idea and you hate your neighbors, I'm sure they could always use more data!


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This comic is yet another fun way to promote Randall's new book, How To, released on September 3, 2019, reminding people to buy it as a Christmas present. Randall's book is used an example of a Christmas present that could be given to a friend or family member. Giving Christmas presents is a traditional way to celebrate the holiday of Christmas, which in the US happens usually on December 25 of each year.

The entire comic links to https://xkcd.com/how-to/, a description of his book and ways to order it. As always the entire picture is a link, even though he has made the URL blue as if it was a clickable link. Of course it will also work if you actually click on the URL. At least in this comic he does state that you can click anywhere on the comic, and if that doesn't work he also gives the URL. Many people would probably still click on the blue link-like line, having not read his text. But the objective of getting them to the xkcd page about How To would have been obtained.

The rest of the comic discusses how to "deliver" this Christmas present. As mentioned in the comic, the "traditional" way that parents teach their kids about Christmas and Christmas gift giving is with the story of Santa Claus, a man who lives on the North Pole, who delivers gifts each Christmas Eve by riding a sleigh pulled by reindeer. He is usually depicted entering a house to deliver gifts by going down the home's chimney. Every year, the North American Aerospace Defense Command (NORAD) tracks Santa as he delivers gifts around the world. Although we take that story for granted, it is no less ridiculous than the alternatives this comic explores, and in fact considerably more so.

As mentioned in the comic, fireplaces (and chimneys) are becoming less common in the United States, so Randall (drawn as Cueball) proposes 3 options for how to deliver his new book as a present:

Option 1: Vaporize the gift (and blow it into their house). This would allow the particles of the book to enter the air vents of the house. However, this book would be unreadable, which defeats the purpose of purchasing the book for someone. As noted by Randall using information from a Journal of the Air & Waste Management Association study, dust particles can remain inside a house for months (with vacuuming) and decades without vacuuming. This inspires Cueball to vacuum his house.

Option 2: Throw the book through their window. Based on research by FEMA, Randall states the speed needed to throw a book-sized object through a window to be 25 mph (~40 km/h). Breaking a window is probably not an ideal way to deliver a gift, as the recipient likely would not be pleased with a hole in their window. If a house has a broken window, perhaps from a previous gift delivery, they might cover up the window with a piece of plywood. Randall notes the speed to throw a book-sized object through a piece of plywood to be 250 mph (~400 km/h), faster than a human can reasonably throw.

If the book weighs about 400g, 25 mph would be enough. But the formula in the comic is wrong (inverted), see the trivia section below.

The title text mentions that building codes in hurricane-prone areas, like the southern United States, rely on information on how easily flying debris can break windows, presumably to improve reinforcement of such windows. Randall proposes a science fair project contributing to these studies (by throwing books at windows).

Option 3: Intercept a different package. This option is to intercept an order of a different book, and replace the pages of the book with Randall's book (which Black Hat is shown doing). As the recipient, Cueball, remarks, this is similar to content spoofing / content injection, where information passed over the Internet is replaced before being delivered to the user. In this "real-life" case, the book's content has been "injected" and replaced with a different book. An off-screen person mentions HTTPS, or Hypertext Transfer Protocol Secure, an extension of the regular HTTP protocol, used for secure communication. Cueball and this person believe that "paper" needs HTTPS, so that Cueball's original book can be "securely delivered" without being intercepted by third parties such as Black Hat.

This could also relate to code injection, where malicious code is injected into a program. An example of code injection is with the famous comic, 327: Exploits of a Mom, where Mrs. Roberts deletes the school's database tables.

The house is very detailed and in the windows are both a cat (typical click bait) and a disheveled looking Pikachu, the most famous Pokémon. Maybe it looks like that because it is about to get a book thrown at it through the window.


[The comic is divided into three sections. The top section contains one low panel stretching across the entire comic. It has a header (same as the title of the comic) with a sub-header beneath. Then below that is a picture of Randall’s new book How To. The black book is shown standing. The blue title is readable but the white text beneath it as well as blue and white text below the image is unreadable. On the cover is a white drawing of Cueball putting in a light-bulb with a quad-copter under each foot. White Hat is watching as Megan walks in with a ladder. Next to the book is a segment of text with a blue link at the end. Beneath this is a text from where a curved arrow goes to the book.]
How To Deliver Christmas Presents
In a future without chimneys
How To
For more questionable ideas for using science to solve problems, check out my new book, How To! Click on this comic or go to xkcd.com/how-to
Good Christmas gift!
[The second section has three normal sized panels on the same row. In the first panel, Randall, drawn as Cueball, is presenting the problem of the comic, while holding one hand out palm up.]
Randall: The traditional way to get Christmas presents into a house is to have a large reindeer-herding man slither down the chimney with them.
Randall: Unfortunately, chimneys are becoming less common in the United States.
[The middle panel shows a line graph with one black and four gray lines. The X-axis is a time scale, with small ticks for each year and larger labeled ticks for every fifth year. The Y-axis is a percentage range with small ticks for every 5% and larger labeled ticks for every 10%. Each of the gray lines are swinging up and down quite a lot, but all but one of them clearly falls down as times passes. The black line has a clear downwards falling tendency. Each line has a label written on segments of the lines, where the lines are thus disrupted. For the gray lines the text is also gray. Above the lines are the following text:]
Disappearing chimneys
Percentage of new homes with fireplaces
Source: Census Bureau Survey of Construction
X-Axis: 1990  1995  2000  2005  2010  2015
Y-Axis: 40%  50%  60%  70%  80%
[In the third and last panel of this segment Randall, holding his arms out, explains that there are other ways to solve the problem.]
Randall: But that's OK; there are other ways to get a gift into a house
Randall: Here are a few options!
[The last segment has a large panel taking up the bottom half of the comic. At the bottom of this panel there are even two smaller comics which lie over this panel and break the bottom border of the panel. They relate to the information in the large panel. In the middle of this panel is a detailed drawing of a house. The tiles of the roof are all individually drawn (8 rows with about 23 tiles each for a total about 180 tiles). To the right on the roof top is a chimney indicated with a dotted line, showing where it is not present. The front of the house has two small windows to the left, a door with door knob, in the middle of the house, with a two steps stair in front of it and a large window with three segments to the right. All three windows have curtains visible and are divided in two, a top and a bottom part On the top of the middle segment there is a handle for opening the windows, all five segments of them. In the window to the left sits a cat and in the central segment of the large window to the right sits Pikachu. The foundation of the house is drawn as 4 rows of bricks to the left (about 12 in each row) and three to the right (about 16 in each row, for 48 on both sides for a total of about 96). ]
[To the left on the side of the house is a line indicating a ventilation shaft. Three arrows end there. They are coming from a bunch of particles of a disintegrating black book with part of a title still readable. Other text is visible, but not readable. Only the first word of the title can be read, but even here the last letter is already partly dissolved. The book is hanging above the grass on the ground below it to the left of the house. Above the book is a section of text marked with a large white number 1 inside a black circle. Beneath the book this text continues. Bordering this text is a one panel comic belonging to this text segment.]
1 Even without chimneys, houses aren't airtight. If you vaporize the gift, parts of it will enter the house through the intake vents...
Book: How
...And it will stay there.
According to a 2008 study from Clarkson University, particles of your gift that settle in their house will remain there for an average of several months if they vacuum, and seven decades if they don’t
Source: DOI 10.3155/1047-3289.58.4.502
[The one panel comic is on top of the large panel beneath the door to the house, but about three times as wide. In the panel, Megan and Cueball are reacting to statement 1. Cueball is walking away from her to the right.]
Megan: Seven decades?!
Cueball: BRB, I need to go vacuum.
Megan: Houses are disgusting
[To the right of the house a gift wrapped present is flying towards the large window, with five lines indicating its speed and direction. Beneath the book is a line indicating the ground away from the house. There is a large segment of text surrounding the book on the three sides away from the house. Above the present next to the dotted-lined chimney is a large white number 2 inside a black circle. Then follows text which goes out to the edge of the panel, and this text continues down to the level of the book where it then only continues to the right of the speed lines. And then finally two lines of text are beneath the book above the ground next to the house.]
2 The critical momentum necessary for a projectile to break glass is around 4 kg*m/s. (40 for ½" plywood.)
Source: fema.gov/previous-missile-impact-test-wood-sheathing
This means you can deliver a book-sized gift by hurling it at a window at 25+ mph
Speed = book mass/ 4 kg*m/s = 25 mph
But if they’ve put up plywood shutters, you’ll need 250mph+ delivery speeds.
[Finally beneath the house and text segment 2, there is a large white number 3 inside a black circle adjacent to the top right of the segment 1 panel comic. Next to this is the final text segment in this panel. Beneath this text is yet another comic, this time in five panels referring to the text, where the panels also break the lower border of the large panel.]
3 Wait until they order a different book, then intercept the package, open the binding, and replace the pages with the ones from yours.
[The five panel comic is on top of the large panel but beneath the text segment 3. ]
[Black Hat opening a box with one hand while having his own book under the other arm.]
[The book cover is open, the pages from the original book have been removed and are interchanged with those from Black Hat’s book, two arrows indicating the switch.]
[Black Hat carrying a closed box.]
[Cueball going down to retrieving the package from the bottom of a three step stairs.]
[Cueball is standing next to the open box reading the book.]
Cueball: ...Ugh, real-life content injection.
Off-screen voice: We need HTTPS for paper.


  • The equation in the comic is incorrect, although the approximate result is correct
    • Speed = book mass/ 4 kg*m/s = 25 mph
      • The units of this formula is not m/s but s/m.
    • It should be 4 kg*m/s /book mass
      • Assuming the book weighs about 0.8lbs (360 g) this would give a speed of 11.1 m/s = 40 km/hour = 24.86 mph ≈ 25 mph.

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Is the equation in the comic wrong? It should be (4 kg*m/s) / (book mass), right? 19:34, 27 November 2019 (UTC)

Yes, that's correct. The equation in part 2 should be (speed) = (momentum) / (mass), given (momentum) = (speed) x (mass). Though the answer seems to be correct, assuming a book mass of approximately 0.8lbs (0.36kg). --shabegger -- Shabegger (talk) (please sign your comments with ~~~~)
Have added this to a trivia section. Maybe Randall will later update the comic, although it is probably cumbersome... But if he does, then that should go in the trivia and the mention of this that I made in the comic, should be changed to, there was an error... Feel free to improve my formulas. --Kynde (talk) 21:35, 27 November 2019 (UTC)

Is that a "Baby Yoda" in the right window? 20:06, 27 November 2019 (UTC)

Houseplant -boB (talk) 20:33, 27 November 2019 (UTC)
Nope that is Pikachu, I'm certain. --Kynde (talk) 21:10, 27 November 2019 (UTC)
I also thought it looked like Yoda. In the 2x version, it looks most like a baby elephant, but careful examination suggests it's probably Pikachu in a really weird perspective (the thing that looks like Yoda's second ear is actually Pikachu's tail, and his actual second ear is probably behind his head). -- 22:47, 27 November 2019 (UTC)
I agree that it is rather difficult to see, but with Randall's use of Pikachu in the past, and the fact that I play Pokémon Go and instantly saw it as Pikachu, I'm quite convinced this is what it should be. Also Yoda do not exist on Earht, but everyone knows Pikachu does :p But can see the baby elephant likeness and the other options as well. By the way, not everyone knows about the 2x version, so here is the link for that.
Close up of Pikachu in window --Kynde (talk) 11:22, 28 November 2019 (UTC)
I may not play Pokémon Go, but I know what a Pikachu looks like, and I don't see it. I'm not even sure which ear the other IP is talking about, or where its eyes and snout are. -- 20:33, 28 November 2019 (UTC)
It’s a gremlin, I’m certain of it. Looks like one, and Gremlins is a Christmas film.
Houseplant -boB (talk) 16:54, 2 December 2019 (UTC)
Definitely Baby Yoda. Pikachu's ears stand up more and therefore you would see both in addition to his tail. Since we don't see both ears and a tail I am certain it is Baby Yoda. 17:28, 3 December 2019 (UTC)
I think the timing of the comic being after the recent reveal of the yoda character in Mandalorian lends credibility to that possibility. It being a Christmas comic lends credibility to the possibility of it being a gremlin, because Gremlins is a well known Christmas movie. Having precedent for Pikachu in XKCD and the slight imbalance of one "ear" being perhaps being more square like Pikachu's tail, lends credibility to that conjecture - I think all three deserve mention in the explanation. -- Brettpeirce (talk) 18:54, 22 January 2020 (UTC)

Why the uptick in fireplaces around 2012/2013? 02:00, 28 November 2019 (UTC)

It snowed that year, maybe that's why? Mikemk (talk) 09:53, 28 November 2019 (UTC)
There was definitely a particularly strong "Polar Vortex" in the Northeast in Late 2012 / Early 2013. I was stuck in it when I went home for New Years. 21:35, 3 December 2019 (UTC)

This comic was posted the day before Thanksgiving, a major American holiday. Can't be a coincidence can it? Mikemk (talk) 09:53, 28 November 2019 (UTC)

Also 2 days before black Friday, a even more major American holiday, and typical ocasion to get christmas gifts. --Lupo (talk) 10:00, 28 November 2019 (UTC)
Yes also think it is Black Friday related. It is now people should think of buying it, as many buy their gifts tomorrow. I buy the way had just ordered the book 10 hours before this comic came came out. But had all along decided that I could wait for x-mas. So someone will give it to me... :-p So although i look forward to reading it, I could wait ;-) --Kynde (talk) 11:14, 28 November 2019 (UTC)

I think it might be notable how, in number 3, the gift explicitly becomes a book. There's no inherent reason--you could just put any gift in the same package as the other and get the same joke. Trlkly (talk) 11:31, 28 November 2019 (UTC)

Of course it's notable, it's the point of this comic. Mikemk (talk) 16:30, 29 November 2019 (UTC)
not just any item has a cover incorporated into the product itself, however, like a book does (?) -- Brettpeirce (talk) 18:54, 22 January 2020 (UTC)

". . . the holiday of Christmas, which in the US happens usually on December 25 of each year." Usually? No, I think Christmas in the US is always on December 25th, by law. 12:37, 28 November 2019 (UTC)

The beginning of the sentence is "Giving Christmas presents is a traditional way to celebrate ..." - so it referrs to the giving of presents, which usually happens on the 25th. There is no law defining the day you give christmas gifts.--Lupo (talk) 12:45, 28 November 2019 (UTC) Good rewrite . . . . 12:01, 29 November 2019 (UTC)

I attempted to add an Original research? template reference, but that template doesn't seem to exist, so I added Citation needed instead. If someone cares to such a template, I'm guessing it would best link to 265: Choices: Part 2. In any case, that's the template I feel would best apply to the NORAD tracking conclusion. Thisisnotatest (talk) 05:12, 30 November 2019 (UTC)

Technically the number of new houses with chimneys alone does not tell anything about disappearing chimneys. If more houses are built than wrecked, the total number of houses with chimneys may rise. This graph is not giving sufficient information about that. Even with a stable number of total houses, the share of chimney-houses may rise, if for some reason (e.g. lower value of the house, lower brick-to-wood rate, etc.) more non-chimney houses are wrecked, than chimney-houses. --Lupo (talk) 08:07, 6 December 2019 (UTC)