explain xkcd - User contributions [en]

Talk:2853: Redshift

2023-11-12T09:32:11Z

162.158.166.205: /* Calculation */ slightly neater

Does it make any sense to try and relate the two Z values to a more "normal" time? [[User:MAP|MAP]] ([[User talk:MAP|talk]]) 21:08, 10 November 2023 (UTC)

I have added exactly that, using `astropy.cosmology` for the calculations [[User:Juandesant|Juandesant]] ([[User talk:Juandesant|talk]]) 21:16, 10 November 2023 (UTC)

There is a big error in the current explanation, saying it means they were interested in this since the early universe, but that would only be true if the z value was much closer to 1. I'm not exactly sure as I haven't done the math, but with that many decimal places of zero's it is probably near enough history to be during their lifetime. So the joke isn't being interested in the early universe since the early universe, but rather so interested in it that they talk about other things with the same terminology.--[[Special:Contributions/172.70.126.142|172.70.126.142]] 21:18, 10 November 2023 (UTC)

Why aren't these values expressed in scientific notation? Separately, do they make sense logarithmically? [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 07:12, 11 November 2023 (UTC)
:Part of the joke is that the values are unwieldy to use compared to everyday language and units. The scientific notation would have lessened this. However they are given in a universal standard time instead of some solar system or human related units, so they generally should be clearly preferred. Sebastian --[[Special:Contributions/172.68.110.188|172.68.110.188]] 15:37, 11 November 2023 (UTC)

I feel like the Earth's gravitational field would affect the answer as z goes to zero? [[Special:Contributions/172.69.22.210|172.69.22.210]] 06:57, 12 November 2023 (UTC)

== Calculation ==

Thanks to ChatGPT-4 and the [https://code.google.com/archive/p/cosmonom/downloads Fortran-90 code] from [https://arxiv.org/abs/1303.5961 arxiv:1303.5961], here's how to get the look-back time from redshift in Python:

<tt><pre><nowiki>
from scipy.integrate import quad
from numpy import format_float_positional

# Cosmological parameters from the Fortran params.f90 header
H0 = 67.15 # Hubble constant in km/s/Mpc
OL = 0.683 # Density parameter for dark energy
Om = 0.317 # Density parameter for matter

# Define the integrand function
def agef(z, OL, Om):
return 1 / ((1 + z) * ((OL + Om * (1 + z)**3)**0.5))

# Function to calculate the age of the universe at redshift z in Gyr
def age_z(z, H0, OL, Om):
integral, _ = quad(agef, z, 1000, args=(OL, Om))
return integral * 977.8 / H0

# Current age of the universe at redshift 0 in Gyr
age0 = age_z(0, H0, OL, Om)

# Function to calculate the look-back time at redshift z in Gyr
def zt(z, H0, OL, Om, age0):
return age0 - age_z(z, H0, OL, Om)

# For z = 0.00000000038
z1 = 0.00000000038
look_back_time_years_z1 = zt(z1, H0, OL, Om, age0) * 1e9 # from Gyr to years
print("Look-back time for z =",
f"{format_float_positional(z1)}: {look_back_time_years_z1:.1f} years")

# For z = -0.000000000000045
z2 = -0.000000000000045
look_back_time_hours_z2 = zt(z2, H0, OL, Om, age0) * 1e9 * 365.25 * 24
print("Look-back time for z =",
f"{format_float_positional(z2)}: {look_back_time_hours_z2:.1f} hours")
</nowiki></pre></tt>

The output being:

<tt><pre><nowiki>
Look-back time for z = 0.00000000038: 5.5 years
Look-back time for z = -0.000000000000045: -5.7 hours
</nowiki></pre></tt>
[[Special:Contributions/172.69.22.12|172.69.22.12]] 08:50, 12 November 2023 (UTC)

2835: Factorial Numbers

2023-10-14T02:52:43Z

162.158.166.205: /* Explanation */

{{comic
| number = 2835
| date = September 29, 2023
| title = Factorial Numbers
| image = factorial_numbers_2x.png
| imagesize = 628x481px
| noexpand = true
| titletext = So what do we do when we get to base 10? Do we use A, B, C, etc? No: Numbers larger than about 3.6 million are simply illegal.
}}

==Explanation==
{{incomplete|Created by a VARIABLE-BASED BOT BEING ESCORTED OUT OF THE COMPUTER SCIENCE DEPARTMENT BY SECURITY - There is no explanation of the comic. There is a complex dive into the mathematics with no simplified explanation created to help understand the comic or its joke. Do NOT delete this tag too soon.}}

This comic is based on the {{w|factorial number system}}, which is a way of writing integers or real numbers using {{w|factorial|factorials}} instead of powers.

[[Cueball]] proposes this number system with his key point being that small value numbers are described only with the small value digits (1, 2, or 3) and saving the larger digits (8 and 9) for larger value numbers. His proposed solution is a complicated number system that some (probably including at least one person able to summon security personnel) might consider unnecessarily clunky to be actually useful.

A factorial is a product of positive integers. For instance, four factorial, written '4!', means 4×3×2×1 = 24. These can be used to write numbers in a strange way.

Normally, numbers are represented in a positional system with a constant base, especially base ten. This means that each digit in a number has a place value based on its position, and that value is a power of ten. For instance, the number 137 usually means 1×102 + 3×101 + 7×100, i.e. one hundred, three tens, and seven units. We say that the 1 is in the hundreds place, the 3 in the tens place, and the 7 in the ones place (or units). The same number could be written in base sixteen as 89, meaning 8×161 + 9×160, i.e. eight sixteens and nine units. The 8 is in the sixteens place, and the 9 is in the ones place.

In a "factorial base," instead of each place value being an escalating power of some constant base, each place value is an escalating factorial. The amount to multiply each place value by to get the next place value increases by 1 each time. So that same number (137 in base 10) could be written 10221, meaning 1×5! + 0×4! + 2×3! + 2×2! + 1×1!. We could say there is a 1 in the 120s place, a 0 in the 24s place, a 2 in the 6s place, another 2 in the 2s place, and a 1 in the ones place.

True factorial numbers also include a 0s place, representing the 0 factorial of 0! Continuing our example of 137 in base 10, the values 1×5! + 0×4! + 2×3! + 2×2! + 1×1! + 0x0! would write out to 102210, but [[Randall]]'s version truncates this rightmost 0 factorial since it is always a value of 0.

In normal base-n notation, n digits are used, running from 0 to n–1. For instance, in base ten, we use the ten digits {0,...,9}. In base sixteen, we need sixteen digits, so we use {0,...,9,A,...,F}. Any of these digits can be used in any position. But in factorial base, each position needs an increasing number of different digits to express all n-digit numbers. The comic labels each position with the equivalent base that would allow the same digits, e.g. the place value 3! is "base 4" because it uses the digits 0 to 3.

For instance, with just two digits, we can express some numbers with the digits 0, 1, and 2, like 21 = five. But we can't express 30 = six. As a result, Randall jokes that since we only have ten digits {0,...,9}, we can only express numbers with up to nine digits, making larger numbers "illegal." Randall believes that would make the largest "legal" factorial base number 987654321 = 9×9!+8×8!+7×7!+6×6!+5×5!+4×4!+3×3!+2×2!+1×1!, which in base ten is 3,628,799 (which he calls "about 3.6 million"). In fact, adding one to this number gives 1000000000, which still doesn't require any digits larger than 9, but he maybe wishes to stay away from the mere possibility of representing the digit that ''ought'' to use another symbol. The first number that actually cannot be represented with our usual ten symbols {0,...,9} comes right after 9987654321, which in decimal equals 36,287,999.

In the comic, the top example represents 3×720 + 5×120 + 3×24 + 0×6 + 1×2 + 1×1, after calculating each factorial accordingly, which gives the decimal value of 2835, [[2835|this comic's number]].

For completion of the examples shown in the panel, the numbers up to 200 in this variable base are:

1=1
2=10
3=11
4=20
5=21
6=100
7=101
8=110
9=111
10=120
11=121
12=200
13=201
14=210
15=211
16=220
17=221
18=300
19=301
20=310
21=311
22=320
23=321
24=1000
25=1001
26=1010
27=1011
28=1020
29=1021
30=1100
31=1101
32=1110
33=1111
34=1120
35=1121
36=1200
37=1201
38=1210
39=1211
40=1220
41=1221
42=1300
43=1301
44=1310
45=1311
46=1320
47=1321
48=2000
49=2001
50=2010
51=2011
52=2020
53=2021
54=2100
55=2101
56=2110
57=2111
58=2120
59=2121
60=2200
61=2201
62=2210
63=2211
64=2220
65=2221
66=2300
67=2301
68=2310
69=2311
70=2320
71=2321
72=3000
73=3001
74=3010
75=3011
76=3020
77=3021
78=3100
79=3101
80=3110
81=3111
82=3120
83=3121
84=3200
85=3201
86=3210
87=3211
88=3220
89=3221
90=3300
91=3301
92=3310
93=3311
94=3320
95=3321
96=4000
97=4001
98=4010
99=4011
100=4020
101=4021
102=4100
103=4101
104=4110
105=4111
106=4120
107=4121
108=4200
109=4201
110=4210
111=4211
112=4220
113=4221
114=4300
115=4301
116=4310
117=4311
118=4320
119=4321
120=10000
121=10001
122=10010
123=10011
124=10020
125=10021
126=10100
127=10101
128=10110
129=10111
130=10120
131=10121
132=10200
133=10201
134=10210
135=10211
136=10220
137=10221
138=10300
139=10301
140=10310
141=10311
142=10320
143=10321
144=11000
145=11001
146=11010
147=11011
148=11020
149=11021
150=11100
151=11101
152=11110
153=11111
154=11120
155=11121
156=11200
157=11201
158=11210
159=11211
160=11220
161=11221
162=11300
163=11301
164=11310
165=11311
166=11320
167=11321
168=12000
169=12001
170=12010
171=12011
172=12020
173=12021
174=12100
175=12101
176=12110
177=12111
178=12120
179=12121
180=12200
181=12201
182=12210
183=12211
184=12220
185=12221
186=12300
187=12301
188=12310
189=12311
190=12320
191=12321
192=13000
193=13001
194=13010
195=13011
196=13020
197=13021
198=13100
199=13101
200=13110

Note the apparent gap at 24 (4!) and 120 (5!) - apparent for those of us who are used to decimal numbers.

Factoradic™ numbers are actually less efficient than any other base. "Efficiency" for a base is normally defined by the radix economy. The actual definition is the size of the base (i.e. the number of possible digits) times the number of digits in a number, although it can be compared to {{w|binary-coded decimal|binary-coded decimals}}. Instead of using actual binary, a binary-coded decimal stores each decimal digit as a binary number. For example, 42 becomes (0100)(0010). This uses 8 bits, which is less efficient than the actual binary value of 101010, which is only 6 bits. It can vary which base is more efficient, like how from 9 to 15, quaternary is more efficient (base 4 * 2 digits = radix economy 8) than ternary (base 3 * 3 digits = radix economy 9). But as the number being represented goes up to infinity, the further you get from a hypothetical base e, the less efficient you become. As a quick example to demonstrate why large bases are less efficient, consider the number 3600. In base 60, it's only three digits, 1;0;0, but because each of those digits can have 60 possible values, its radix economy is 3*60=180. But even though the decimal representation uses a 4th digit, since there are only 10 possible values for each digit, the radix economy is only 4*10=40.

For a k-digit factoradic™ number, the 1st digit can have 2 values, the 2nd can have 3, the 3rd can have 4, up to the k-th digit having k+1 possible values, so the radix economy is effectively (k+1)(k+2)/2 - 1. Unfortunately, this is substantially more difficult to calculate, because it involved the inverse gamma function. But if you use ln n / ln ln n as an approximation of the asymptotic behavior of the inverse of Stirling's approximation, you can set up the limit ln n / ln^2 ln n, which diverges as n approaches infinity. Therefore, at least if you let factoradic™ numbers use other symbols for digits and increase past 10!, then no matter how large and inefficient of a base you're comparing it to, factoradic™ numbers will eventually be less efficient. Meanwhile, if you do stop at 10!-1, it's 9 digits, so its radix economy is 54. And if you solve 54 = b*floor(1+ln(10!-1)/ln(b)) for b, you find that b is approximately 6.75. So factoradic™ is more efficient than base 7 and up, but less efficient than binary, ternary, quaternary, quinary, and senary.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon. - Still needs a lot of deconstruction/reconstruction work on the [Poster:] to make it properly Transcripted (no tables, ideally!), but have improved the surrounding markup/descriptions}}
:[Cueball is standing in front of a large poster. There are two uniformed officers (a Ponytail and a further Cueball, wearing badged hats) approaching Cueball.]
:[Poster:]

:Variable-base Factoradic™ numbers
:{|
|Base 7||Base 6||Base 5||Base 4||Base 3||Base 2
|-
|3||5||3||0||1||1
|}

:Left side

:{| class="wikitable"
|Base 10||Factoradic
|-
|1||1
|-
|2||10
|-
|3||11
|-
|4||20
|-
|5||21
|-
|6||100
|-
|7||101
|-
|
|-
|21||311
|-
|22||320
|-
|23||321
|}

:Right side

:{| class="wikitable"
|Base 10||Factoradic
|-
|24||1,000
|-
|25||1,001
|-
|
|-
|5,038||654,320
|-
|5,039||654,321
|-
|5,040||1,000,000
|-
|
|-
|999,998||266,251,210
|-
|999,999||266,251,211
|-
|1,000,000||266,251,220
|-
|1,000,001||266,251,221
|}

:Cueball: Small numbers like seven or nineteen shouldn't use big numerals like "7" or "9".
:Cueball: I mean, "9" is the biggest numeral we have! It should be reserved for '''''big''''' numbers.
:Cueball: Small numbers should be written with small numerals like "1" or "2".
:Cueball: That's why my variable-base system uses...Hey! No, listen!
:[Caption under the comic:] Factorial numbers are the number system that sounds most like a prank by someone who's about to be escorted out of the math department by security.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Characters with hats]]
[[Category:Math]]
[[Category:Self-reference]] 
[[Category:Comics featuring Ponytail]] 
[[Category:Multiple Cueballs]]

2839: Language Acquisition

2023-10-14T02:50:47Z

162.158.166.205: /* Explanation */

{{comic
| number = 2839
| date = October 9, 2023
| title = Language Acquisition
| image = language_acquisition_2x.png
| imagesize = 193x239px
| noexpand = true
| titletext = My first words were 'These were my first words; what were yours?'
}}

==Explanation==
{{incomplete|Created by MY FIRST WORDS - This should be a bit longer. Do NOT delete this tag too soon.}}
{{w|Language acquisition}} is the process by which humans, generally infants, learn a language.

There are many theories as to how this process works, but Randall takes this phrase literally, saying that infants learn languages one new word at a time. This may be true when learning a second language, but is typically not true for infants learning their native language (mother tongue). It is a common milestone to celebrate a child's "[https://www.parents.com/baby/development/talking/baby-talk-a-month-by-month-timeline1/ first word]", but typically these would be simple words, such as "mama" or "dada".

The child's sentence is twelve words, all unique. This implies these are the only words known so far, which would be a very unusual set of words to be the first ones learned. Furthermore, the child appears to have learned some fairly advanced grammatical concepts in order to construct this fairly complex sentence. Learning grammar typically takes much longer, and only occurs once a child has learned sufficient vocabulary to recognise patterns in how the words are used.

Interestingly if this sentence is true, the child has learned the word for 12 before learning the words for any other numbers, and so could not have given a quantitative update on previous days. However, this would also imply that their counting is not yet as advanced as their language acquisition, which may mean that they are simply wrong about the number of words they have learned.

Two letter blocks on the ground next to the child show capitals 'A' and 'B', and a third has an upside-down lowercase 'e'. The block with the 'e' may be placed upside-down, but it may also be a block with the phonetic symbol {{w|schwa}} on it. This would suggest the parents are teaching their child advanced linguistics concepts before they've fully learned to speak a first language, which might explain why the child's language acquisition is so unusual.

The title text makes a self-referential joke about the concept of "first words", where a supposed child discusses one's own first words in a complete sentence. There are seven unique words in the title text, most of which do not appear in the comic image, suggesting the title text and comic image referred to two different children.

[[2567: Language Development]] has had a similarly obscure take on language acquisition.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[A child, drawn as a smaller Hairy. He stands amongst three blocks with letters on them, showing faces with A, B and an upside-down lowercase e. Megan and Cueball stand to the right of him.]
:Child: Vocabulary update: I learned another word today, bringing my total to twelve.

{{comic discussion}}
[[Category:Language]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics with babies]]

2840: Earth Layers

2023-10-14T02:49:26Z

162.158.166.205: /* Explanation */

{{comic
| number = 2840
| date = October 11, 2023
| title = Earth Layers
| image = earth_layers_2x.png
| imagesize = 585x627px
| noexpand = true
| titletext = The Earth's magnetic field is primarily generated by currents in the liquid outer core, though some geophysicists argue that an unexplained mismatch with models suggests that the Kinder toy contains a magnet.
}}

==Explanation==
{{incomplete|Created by A CONSPIRED CORE - Please change this comment when editing this page. Like this? Do NOT delete this tag too soon.}}

This comic reimagines the internal structure of the earth, mixing the real geological layers of the planet with fictional ones. Some of the fictional layers are appropriated from the layers of other objects that have cross-sectional diagrams, such as the layers of a piece of fruit, an eyeball, an item of confectionary or a building.

{| class="wikitable"
! Layer
! scope="col"| Explanation
|-
! scope="row"| Lithosphere/Crust (50/50 Blend)
| The {{w|lithosphere}} is any outermost rocky layer of a planet. On Earth it consists of the {{w|Earth's crust|crust}} and any parts of the upper mantle (see below) that do not convect. To say they are two distinct layers that could be blended together is rather nonsensical.
The upper limit of a planet's lithosphere is usually taken as where it meets the hydrosphere/atmosphere (wherever either may be present, otherwise the vacuum of space) but may or may not include the rock-derived {{w|pedosphere}} (for Earth, especially) or distinct overburden of loose {{w|regolith}}. All of these overlaid layers would typically be far too thin to be reliably distinct in the depiction of this Earth-like planet, and the diagram depicts the surface details only as a 'painted on' blue/greens/browns/etc to distinguish ocean areas and land heights with vertical depths/elevations that are already effectively insignificant at the scale of this diagram, before even considering the such relatively narrow layers of interface material.
|-
! scope="row"| {{w|Upper mantle}}
| An actual layer of the earth's structure.
|-
! scope="row"| Deep mantle
| A pseudo-correct layer of the earth's structure. There is a layer called the {{w|lower mantle}}, which could be what Randall refers to.
|-
! scope="row"| Filler
| This suggests there is space in the earth that was empty, so the creator(s) added some filler to fill up the extra space.
|-
! scope="row"| Vitreous humor
|Vitreous humor ({{w|vitreous body}}) is the transparent gel inside the eye, located between the lens and the retina. It is nonsensical to suggest it could be put inside the earth.
|-
! scope="row"| Mechanical/HVAC layer
| {{w|HVAC}} is an abbreviation for 'Heating, Ventilation and Air Conditioning' - the system used to heat or cool a building. Tall buildings may have a dedicated "HVAC floor" or "{{w|mechanical floor}}" between regular floors, like an extra layer. However, the Earth most definitely should not {{citation needed}}.
|-
! scope="row"| Guacamole
| {{w|Guacamole}} is a dip or sauce made from avocados. [https://www.britannica.com/topic/guacamole Originating from ancient Mexico], it often includes onions, tomatoes and spices. Notably, guacamole is a major component of seven layer dip, and is shown here to be the seventh layer (from the surface).
|-
! scope="row"| Cytoplasm
|{{w|Cytoplasm}} is the "flesh" of both eukaryotic and prokaryotic cells; a jelly-like substance that fills all the otherwise empty space within the cell.
|-
! scope="row"| Cork
|Due to the proximity of the cork layer and the insulation layer, this may possibly be referencing {{w|Cork (material)|cork}}-lined walls, which are used today mostly for high quality soundproofing, but have [https://www.jstor.org/stable/27135713 a considerable history]. Another potential reference could be the fact that baseballs (another spherical shape) have a layer of cork in them (though it is usually in the center). Finally, the cork is a real layer of tissue in many woody plants, part of the bark. This comic was posted the day after Birkenstock Holding plc was listed on the New York Stock Exchange; Birkenstock sandals include a layer of cork.
|-
! scope="row"| Insulation
|Possibly a reference to the {{w|building insulation}} installed in the walls and ceilings of buildings. Technical fabrics used to make clothing also often include an insulation layer, combined with, for example, a waterproof/water-resistant membrane and an inner contact later.
|-
! scope="row"| Seeds
|Part of a fruit which often appear in a distinct layer within, or sometimes on the surface of, the flesh. They are used for reproduction in {{w|angiosperms}} and many are a major source of food for some animals.
|-
! scope="row"| {{w|Pith}}
|Part of a tree trunk or the thick spongy layer of the skin of a citrus fruit. Notably, this layer is below Seeds, which implies the seeds are outside of the pith. Although rare, some fruits do, in fact, have their seeds on the outside of their skin, such as {{w|Cashews}}. However, this is not present in any well-known citrus plants, or, if there are citrus plants like this, they are not discovered yet, let alone well-documented.
|-
! scope="row"| Nougat
|{{w|Nougat}} is a family of confections made with sugar or honey, roasted nuts, whipped egg whites and, sometimes, chopped candied fruit. It often appears as layers within confectionary items (such as Snickers, Double Decker and Mars) and, notably in relation to the comic, it constitutes the second-innermost layer of {{w|Mozartkugel}}n, a spherical confection.
Geography teachers sometimes hand confectionery like this to their students to give them an idea what "concentrically layered structure" means. Most of the time it turns out that this is their least concern, while at the same time a general consensus emerges that this is one of the best ideas said teacher has had in a long time. This layer is possibly an allusion to that practice.
|-
! scope="row"| {{w|Outer core}}
| An actual layer of the earth's structure.
|-
! scope="row"| {{w|Inner core}}
| An actual layer of the earth's structure.
|-
! scope="row"| Secret core
| Likely references secret compartments that may be hidden in the hardest to find recesses of other objects or structures, for the purposes of concealing precious items or closely-guarded secrets. Could also be interpreted as a section of the core that only certain people, such as Randall, are aware of. In the context of "inner core, outer core, secret core" may also be a riff on Leonard Cohen's ''Hallelujah'', a la [[2583: Chorded Keyboard]].
|-
! scope="row"| Kinder toy capsule
| A {{w|Kinder (brand)|Kinder}} toy is a reference to a chocolate egg-shaped confection by the Kinder brand, the {{w|Kinder Surprise}}, a chocolate shell with a plastic 'yolk' capsule in the center. Though that is loose within a void, unlike this 'Earth model', it closely matches this philosophy despite (or because of) being a {{w|Kinder_Surprise#United_States|banned food item}} in the United States, due to a 1938 FDA rule prohibiting a "non-nutritive object" (the plastic egg 'yolk' containing the toy) to be encased inside of an edible item (the outer chocolate layer) unless it has a specific function related to the edible part. It is widely believed that this is because the 'yolk' can be a choking hazard, despite the fact that you'd have to be swallowing a chicken egg-sized confectionery in a single mouthful for that to happen accidentally, or deliberately try to consume the plastic capsule whole. The toys within, however, may contain small pieces that can pose a choking hazard, especially in the toys that are packed as components, requiring some assembly, in order to fit into the capsule. Rules about small components (in toys for young children) and the inclusion of non-food contents within food-items have been used to prohibit this product within the US. To specifically overcome the latter regulations, the {{w|Kinder Joy}} was developed; an egg-shaped packaging containing the chocolate treat in one half and the toy separately within the other.

Randall's punchline of the comic is that there may indeed be a hidden toy at the center of the Earth. The title text explains that due to the {{w|Earth's magnetic field|geomagnetic field}} not behaving as scientific models suggest it should, some geophysicists argue that the hidden toy is – or at least contains – some additional form of magnet which impacts the accepted {{w|Magnetohydrodynamics|magnetohydrodynamic}} effect. A more plausible explanation is that their model is wrong because they've based it on Randall's diagram full of spurious layers!
|}

Since the radius of the earth is 6371 km, if the diagram is to scale then measurement of it gives the Kinder Toy Capsule a radius of about 900 km. This gives the Kinder Toy Capsule a volume of just over 3 billion km3. Assuming a real Kinder Egg has a volume of 60 cm3, and a packing density of 63.5%, the Kinder Toy Capsule could contain 5x1022 (50 sextillion) actual Kinder Eggs. Current mathematical models of the magnetohydrodynamics of the Earth's core do not include the potentially significant contribution of 50 sextillion Kinder Toy Capsules,{{citation needed}} a glaring oversight in a well developed field.

==Transcript==
:[Header/Title]
:The layers of the Earth

:[Cutaway diagram of the Earth, a sphere with abstract sea/land/elevation surface, except for a slice removed (quarter-arc in three axes) to make visible a number of roughly equally-sized 'strata'/shells, all the way down to the intact smallest sphere. From surface downwards, these are:]
:Lithosphere/crust (50/50 blend)
:Upper mantle
:Deep mantle
:Filler
:Vitreous humor
:Mechanical/HVAC layer
:Guacamole
:Cytoplasm
:Cork
:Insulation
:Seeds
:Pith
:Nougat
:Outer core
:Inner core
:Secret core
:[The central sphere:]
:Kinder toy capsule

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Geology]]
[[Category:Food]]

2813: What To Do

2023-08-09T23:33:13Z

162.158.166.205: /* Transcript */

{{comic
| number = 2813
| date = August 9, 2023
| title = What To Do
| image = what_to_do_2x.png
| imagesize = 740x723px
| noexpand = true
| titletext = FYI: The 'drop, cover, and hold on' advice only applies to earthquakes. If you encounter a mountain lion, you should absolutely not drop to the ground, crawl under it, and hold on to one of its legs.
}}

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

Similar to [[1890: What to Bring]], this comic takes four unrelated dangerous situations, and tries to mix-and-match the solutions. Predictably,{{citation needed}} mixing up good advice leads to fairly nonsensical behavior, so only the original four matches are marked green as acceptable.

{| class="wikitable"
! (problem) vs (solution)
! scope="col"| stand up straight, speak firmly, and slowly back away
! scope="col"| run toward a building or hard-topped vehicle
! scope="col"| calmly exit the building
! scope="col"| apply firm pressure
|-
! scope="row"| {{w|mountain lion}}
| Yes. This is a common recommendation when encountering a mountain lion (puma, cougar, etc) out in nature.
| No. Running away may cause the animal to chase you, and it may consider you as prey. However, if you safely make it into the building or vehicle, you may be able to hide or drive away from the animal and may be safer than being outdoors with it.
| No. Exiting a building and approaching the animal is less recommended.
| No. Applying "firm pressure" to the (wild) animal is a terrible idea and may result in injury. Applying light pressure to a domesticated cat may make it less likely to attack, but wild cats do not respond positively to it.
|-
! scope="row"| lightning
| No. Yelling at lightning is ineffective. {{citation needed}}
| Yes. This is the recommended solution when encountering lightning - to go indoors or inside of a hard-topped vehicle to avoid being struck, or to be ''inside'' some form of faraday cage if lightning does strike your location. Staying inside of a metal vehicle may cause other problems, but it's generally better than being directly struck.
| No. Exiting a building is a poor idea, as the risk of getting struck by lightning is increased.
| No. There is no safe way to "apply firm pressure" to lightning.
|-
! scope="row"| fire alarm
| No. Yelling at a fire alarm is ineffective. {{citation needed}}
| No. When a fire alarm is sounding, it is terrible advice to run ''towards'' the sound of the alarm, unless you are a trained member of the fire department.
| Yes. This is the recommended advice when hearing a fire alarm - to calmly exit the building, and move to a safe location.
| No. Applying firm pressure to a fire alarm will not result in stopping the alarm, unless you are able to manage to suppress the sound, or the fire alarm sensors. Regardless, this will not stop an active fire.
|-
! scope="row"| bleeding
| No. Yelling at a bleeding person, or at the bleeding itself, is ineffective. {{citation needed}}
| Probably not. Running toward a building or vehicle is not a typical solution if someone is bleeding. However, there could be medical supplies inside the building or vehicle, so this idea is not completely incorrect.
| No. Exiting a building is not helpful if someone is bleeding, if either the exiting one is the injured one, or the non-injured one. Although, if someone/something in the building is the cause of the bleeding, this could be a good idea so that the bleeding or injury does not get worse.
| Yes. This is the recommended solution to stop bleeding - apply firm pressure to stop the bleeding.
|}

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

:[The comic is laid out like a grid, with situations down the left-hand side (mountain lion / lightning / fire alarm / bleeding) and the solutions across the top (stand up straight, speak firmly, and slowly back away / run toward a building or hard-topped vehicle / calmly exit the building / apply firm pressure ). The grid illustrates the "match-ups", with a green square denoting a "correct" match-up and a red square denoting a bad idea.]

:[From the top left corner, going from left to right, top to bottom, with each first item being on its own line in the grid, the squares are as follows:]

:[Green square, a mountain lion (drawn as a large cat) sits on the left, on a perch. Cueball and Megan have their arms raised and are speaking to it. Lines in front of them indicate they are backing up.]
:Cueball: ''HEY. STOP.''
:Megan: ''SHOO.''
:*'''stand up straight, speak firmly, and slowly back away''' -> '''mountain lion'''

:[Red square, Cueball and Megan are being chased by a mountain lion, and are running towards a building to their right.]
:*'''run toward a building or hard-topped vehicle''' -> '''mountain lion'''

:[Red square, Cueball and Megan exit a building and approach a mountain lion.]
:Megan: ''Hello.''
:*'''calmly exit the building''' -> '''mountain lion'''

:[Red square, Cueball is putting his hands firmly on a mountain lion.]
:*'''apply firm pressure''' -> '''mountain lion'''

:[Red square, lightning strikes a tree. Cueball is standing outside, with his arms raised, yelling at the lightning. Lines in front of him indicate he is backing up.]
:''BOOM''
:Cueball: ''NO!''
:*'''stand up straight, speak firmly, and slowly back away''' -> '''lightning'''

:[Green square, lightning strikes a tree. Cueball and Megan run toward a building to their right.]
:''BOOM''
:*'''run toward a building or hard-topped vehicle''' -> '''lightning'''

:[Red square, lightning strikes a tree. Cueball and Megan exit a building and approach the lightning-struck tree.]
:''BOOM''
:*''' calmly exit the building''' -> '''lightning'''

:[Red square, lightning strikes a tree. Cueball pushes on the lightning-struck tree.]
:''BOOM''
:*'''apply firm pressure''' -> '''lightning'''

:[Red square, a fire alarm is beeping. Cueball yells at the alarm, with his arms raised. Lines in front of him indicates he is backing up.]
:''BEEP BEEP BEEP''
:Cueball: ''HEY.''
:*'''stand up straight, speak firmly, and slowly back away ''' -> '''fire alarm'''

:[Red square, a fire alarm is beeping next to a building with flames on its roof. Cueball and Megan run toward the burning building.]
:''BEEP BEEP BEEP''
:*'''run toward a building or hard-topped vehicle''' -> '''fire alarm'''

:[Green square, a fire alarm is beeping next to a house with flames on its roof. Cueball and Megan are exiting the burning building.]
:''BEEP BEEP BEEP''
:*'''calmly exit the building''' -> '''fire alarm'''

:[Red square, a fire alarm is beeping, and Cueball is trying to "suppress" the beeping sound. Behind him are flames.]
:''BEEP BEEP BE-eep eep eep''
:*'''apply firm pressure''' -> '''fire alarm'''

:[Red square, Cueball is bleeding from his right arm, and holds it. Megan to his right yells at him with her arms raised. Lines in front of her indicates she is backing up.]
:Megan: ''HEY!''
:Megan: ''STOP IT!''
:*'''stand up straight, speak firmly, and slowly back away''' -> '''bleeding'''

:[Red square, Megan, holding a first aid kit in one hand and a bandage in the other, runs with a bleeding Cueball towards a building to their right.]
:*'''run toward a building or hard-topped vehicle''' -> '''bleeding'''

:[Red square, Megan holds a bandage, and to the ground in front of her is a first aid kit. Cueball is walking to the right of the panel, with an injured and bloody left arm raised.]
:Cueball: Bye!
:*'''calmly exit the building''' -> '''bleeding'''

:[Green square, Cueball sits in a chair and Megan is treating him by putting her hands on his injured limb. Behind her on the ground is a first aid kit.]
:*'''apply firm pressure''' -> '''bleeding'''

{{comic discussion}}
[[Category:Animals]]
[[Category:Charts]]
[[Category:Comics with color]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Weather]]

150: Grownups

2023-07-30T21:34:40Z

162.158.166.205: /* Explanation */

{{comic
| number = 150
| date = August 30, 2006
| title = Grownups
| image = grownups.png
| titletext = I've looked into this, and I can't figure out a way to do it cheaply. And I guess it wouldn't be sanitary.
}}

==Explanation==
[[Randall]] is again playing with the child/grownup mental setup. During childhood, adults ("grownups") make most of the decisions and put constraints on what their children do. As children age and eventually become grownups, there are some things that they do not do anymore, as they see them as childish.

[[Megan]] has taken these thoughts seriously, and realizes that with her newfound freedom as a grownup, she gets to define what her adulthood means. Free from constraints, she goes ahead and creates a {{w|ball pit}} in her apartment of colored plastic balls. [[Cueball]] admires this spirit and enters the ball pit. It is difficult to decipher Randall's true intent behind this somewhat cryptic comic, but it seems from the heart that the two are engaging in sexual activity in the pit.

The trend with adults participating in children's activities is continued in [[219: Blanket Fort]], and with adults who feel like children while doing adult things as in [[616: Lease]], which references this comic in the title text.

The title text reveals that [[Randall]] also would like to make his own ball pit, but he finds it [http://playpenballs.com/index.php?route=product/category&path=60 expensive to buy] and also [http://www.reddit.com/r/mildlyinteresting/comments/1q6bru/this_is_how_they_clean_the_plastic_balls_from_the/ hard to keep clean]. Both of these are true - see links. Most public ball pits can easily become very dirty, as many children and toddlers play in them. But Randall really did make his own ball pit at home, as seen [https://blog.xkcd.com/2007/11/19/growing-up/ in his blog].

==Transcript==
:[Cueball is talking to Megan who is behind a waist-high screen across a doorway with colorful playpen balls behind her.]
:Cueball: Hey, I was wondering if you had plans for-- holy crap, what happened to your apartment?
:Megan: I filled it with playpen balls!
:Cueball: I... what? Why?

:[Megan is seen from the front through the door with the colored balls behind her.]
:Megan: Because we're grown-ups now, and it's our turn to decide what that means.

:[Cueball is seen from the side standing next to the open door. Megan cannot be seen, except her hands on the screen, but some of the colored balls can be seen through the door. A beat panel.]

:[Same view but both have entered into the apartment, with colored balls spilling out into the corridor so the screen is no longer shown. A big pink love heart drifts out the door.]

==Trivia==
* This is one of the six [[Footer comics|footer comics]] featured in the bottom segment of [https://xkcd.com xkcd.com].
* Randall actually built a ball pit in his apartment, which he talks about and shows pictures of in [http://blog.xkcd.com/2007/11/19/growing-up/ these] [http://blog.xkcd.com/2008/02/27/ballpit-phase-ii/ two] posts on his blog.
* Inspired by this comic, the website [http://www.chiliahedron.com/ballroom/ chiliahedron.com] provides a calculator for how much it would cost to make your own ball pit.
* This comic used to be available as a signed print in the [https://store.xkcd.com/products/signed-prints xkcd store], before it was shut down.

{{comic discussion}}

[[Category:Footer comics]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics with color]]
[[Category:Romance]]
[[Category:Sex]]
[[Category:Playpen balls]]
[[Category:Comics with xkcd store products]]

Talk:2781: The Six Platonic Solids

2023-07-11T23:01:09Z

162.158.166.205:

Does he know about Homestar Runner? [[Special:Contributions/172.70.131.137|172.70.131.137]] 06:02, 27 May 2023 (UTC)
:Yes. http://www.hrwiki.org/wiki/Webcomic_Sightings#xkcd [[User:Trogdor147|Trogdor147]] ([[User talk:Trogdor147|talk]]) 01:07, 29 May 2023 (UTC)

Why Jorb? Only thing I can find is [https://en.wiktionary.org/wiki/jorb Jorb on wikitionary] just meaning spelling of bad pronunciation of Job. And yes the episode of Homestar Runner [https://homestarrunner.com/toons/a-jorb-well-done A Jorb Well Done] comes up. Also this episode that is the top meaning of jorb on [https://www.urbandictionary.com/define.php?term=Jorb Urban dictionary]. Would really like there to a better idea than that Plato did a great Jorb making a sixth solid to rule the mathematicians. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 07:18, 27 May 2023 (UTC)

: I agree. We should ask for our money back. -- [[User:Dtgriscom|Dtgriscom]] ([[User talk:Dtgriscom|talk]]) 17:19, 27 May 2023 (UTC)

What if there're much more of them, like a [https://xkcd.com/2657 Ď̩̰odec̭ähedron], but our minds can't properly comprehend their shape?
: There are a bunch of other regular polyhedra besides the Platonic solids. Most notable are the triangular, square, and hexagonal tilings (which are planar and infinite) and the four Kepler-Poinsot polyedra (which are nonconvex). And there are dozens more if you don't require faces to be planar. [[Special:Contributions/172.70.178.234|172.70.178.234]] 09:44, 27 May 2023 (UTC)
::See https://youtu.be/_hjRvZYkAgA for an overview of every regular polyhedron in Euclidean 3-space. [[Special:Contributions/162.158.146.40|162.158.146.40]] 09:59, 27 May 2023 (UTC)
:::I had never seen this channel before, and I'd very much like to thank you for introducing it to me. [[Special:Contributions/162.158.167.8|162.158.167.8]] 21:39, 29 May 2023 (UTC)
: Some of the proofs of the theorem that there are exactly five platonic solids do not require our minds to "comprehend their shape", because they only rely on their algebrical properties. In fact, the Group theory proof works in any dimension (≥3), despite our minds being very bad at picturing what stuff looks like in higher dimensions. In fact, it's a bit of the opposite: lower dimensions (2 and 3) are "special cases", because all other dimensions have exactly 6 such platonic solids. [[User:Jthulhu|Jthulhu]] ([[User talk:Jthulhu|talk]]) 15:41, 27 May 2023 (UTC)

I think this is a reference to how the Utah Teapot is nicknamed “the sixth Platonic solid” due to its presence beside real Platonic solids in demonstrations of 33D rendering. [[Special:Contributions/172.68.118.133|172.68.118.133]] 08:52, 27 May 2023 (UTC)
:...yeah, but you need to render that 33D shape on a proper 32D monitor, ideally, because even on a 31D monitor the two different forced perspectives/projections you need to collapse the extra dimensions down tend to look confusing. [[Special:Contributions/172.70.162.229|172.70.162.229]] 10:46, 27 May 2023 (UTC) *insert winky-face as necessary*
:: Thanks, that predates my claim in https://arxiv.org/abs/2103.00090, so I won’t claim priority:
::: ‘By this conception, the claim that there is a Russell Set is simply wishful thinking, analogous to wanting the phrase “sixth Platonic solid” to have a referent, while not actually intuiting which shape this might be.’
:: — [[User:FlashSheridan|FlashSheridan]] ([[User talk:FlashSheridan|talk]]) 12:33, 31 May 2023 (UTC)

Should we think about Jorb, perhaps, as "J orb," which might lead us to think about (''i'',''j'') coordinates, i.e. notational systems where ''j'' is the square root of minus 1? (blah blah engineering vs. mathematics, what does ''i'' mean, &c., &c., &c.) Maybe not! [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 10:41, 27 May 2023 (UTC)

When I naively imagine further platonic solids, my approach to cheating is usually to imagine arbitrarily non-euclidean space. It’s somewhat pleasant that the jorb looks a little like that —- it’s only platonic if the coordinate system it’s in bends and stretches to make it so. I imagine the name and depiction are simply to be intentionslkynvague or confusing about what it actually is. It’s a lot harder to do real innovation nowadays and tasks like inventing a jorb can readily crop up to nerds (the nerd snipe kind) who are looking for sufficiently hard and harmless puzzles. A sixth platonic solid seems to mostly happen outside the norms of what people usually consider in a pretty significant way. [[Special:Contributions/162.158.155.99|162.158.155.99]] 02:30, 28 May 2023 (UTC)

I asked GPT-4, "Why could Sauron control the Nazgûl when not in possession of the One Ring?" The response:

:''Sauron was able to control the Nazgûl even when he didn't possess the One Ring because of the nature of the rings they received and the relationship these rings had with the One Ring.''
:''Sauron, disguised as Annatar, the "Lord of Gifts," helped the Elven smiths of Eregion, led by Celebrimbor, forge the Rings of Power. Unknown to the Elves, Sauron had instructed them to forge the rings in such a way that they could be controlled by one master ring - the One Ring. He secretly forged the One Ring in the fires of Mount Doom, uttering the famous verse: "One ring to rule them all, one ring to find them, one ring to bring them all and in the darkness bind them."''
:''When he gave the nine rings to Men, these rings corrupted them over time and turned them into the Nazgûl, also known as the Ringwraiths. Because these nine rings were still under the influence of the One Ring, Sauron was able to control the Nazgûl even when he did not possess the One Ring himself. The One Ring's power was inherent and didn't need physical proximity to exert control. The Nazgûl were bound to the will of Sauron as their wills were dominated by their rings, which were in turn dominated by the One Ring.''
:''The link and dominance were so strong that even when the One Ring was lost, the Nazgûl remained under Sauron's control. It's also worth noting that Sauron held the Nine Rings the Nazgûl originally received, which could also contribute to his ability to control them.''
:''It's a complex network of influence and control established by Sauron, making him a powerful Dark Lord even in the absence of his master ring.''

Well. I'm glad <s>someone</s> something understands that. Lol. [[Special:Contributions/172.69.22.145|172.69.22.145]] 06:11, 28 May 2023 (UTC)

Looks suspiciously like a bicycle saddle to me. And as anyone who's parked their backside on one for any distance or time, it is DEFINITELY a solid. [[User:RAGBRAIvet|RAGBRAIvet]] ([[User talk:RAGBRAIvet|talk]]) 07:25, 28 May 2023 (UTC)
:(Well, there's all kinds of saddles, and the [https://www.brooksengland.com/en_uk/swallow.html golden era of leather saddles] were actually not that bad (that link states a 10 year guarantee for the current output, but I personally know of a couple used regularly for 60+years and were still doing well), though with the advent of more synthesised materials they've had to go creative with the texture/covering to give it back the 'give'. Which no doubt makes more an 'impression' on the more modern saddle purchaser, in more ways than one.)
:Reminds me of one of the more abstract 'elemental' {{w|Henry Moore}} pieces, or possibly one of his contemporaries/'inspired-by's. And you could certainly find painters and other art-form creators who have gone into 'abstract blob' shapes, either to represent something real in a novel way or to deliberately represent nothing real at all, and I suspect that's Randall's aim... (Like "xkcd" made to not look enough like anything else, or so intended). It certainly shows no sign of ''any'' symmetry at all. [[Special:Contributions/172.70.86.32|172.70.86.32]] 12:29, 28 May 2023 (UTC)

Based on the shape, ribbing, and a different definition of "platonic" I think this could be referring to the Roman artefact that was recently re-classified as a dildo. Platonic solid? [[Special:Contributions/172.70.111.111|172.70.111.111]] 16:06, 28 May 2023 (UTC)

Not gonna lie, this feels like a Cow Tools comic to me. Sometimes mathematicians discover new things, wouldn't it be weird if they discovered something impossible? End of joke. Everything else regarding the shape and name is an inkblot test (until the title text which is actually a LOTR reference of course). [[Special:Contributions/172.70.82.59|172.70.82.59]] 17:04, 28 May 2023 (UTC)

Is it worth mentioning that the dodecahedron and isocahedron have their names switched? [[User:C.h.ninnymuggins|C.h.ninnymuggins]] ([[User talk:C.h.ninnymuggins|talk]]) 21:00, 28 May 2023 (UTC)
:It would be if they were (a common error), but... they aren't. (See {{w|Platonic solid|here}}.) [[Special:Contributions/172.69.79.196|172.69.79.196]] 21:33, 28 May 2023 (UTC)

Ok whoever added that jan misali link that's super cool of you nice [[Special:Contributions/172.71.82.147|172.71.82.147]] 03:50, 29 May 2023 (UTC)Bumpf

I feel that there's a joke missing here, especially with the LOTR connection made in the alt-text. After all, Plato might have gifted the solids to the mathematicians, but thanks to Gary Gygax, it was the gamers who found a use for them....
[[Special:Contributions/172.70.86.7|172.70.86.7]] 06:37, 29 May 2023 (UTC)

Plato did a a great jorb ruling the mathematicians by forging the impossible... plato got a gold star at his job review... was that really it?--[[User:4til7|4til7]] ([[User talk:4til7|talk]]) 20:33, 29 May 2023 (UTC)

I kind of feel sorry for the platonic solids. Condemned to the friend zone for eternity; or at least until the end of this universe. [[User:These Are Not The Comments You Are Looking For|These Are Not The Comments You Are Looking For]] ([[User talk:These Are Not The Comments You Are Looking For|talk]]) 22:54, 29 May 2023 (UTC)

You've all been nerd sniped. [[Special:Contributions/172.70.42.43|172.70.42.43]]

Also the Gömböc comes to mind from the name, the shape and the novelty of Jorb.
[[Special:Contributions/162.158.182.115|162.158.182.115]] 18:51, 2 June 2023 (UTC)
: Added link to "{{w|Gömböc}}", as that is immediately what I thought of when seeing this comic. Randall's Jorb looks designed to have Gomboc-like properties: if starting on the long thin facet seen on the top edge, it would be gently pulled down by the large round egg-like "end" and then presumably roll onto one side or the other i.e. rotating around its long axis until reaching the position shown. If the Jorb were indeed a mono-monostatic shape, then like the known Gömböc design it would be a "polyhedron" with one (albeit curved) "facet", and like the Platonic solids it can rest on any one of its facets, trivially true as there is only one facet. [[User:Mrob27|Mrob27]] ([[User talk:Mrob27|talk]]) 05:50, 12 June 2023 (UTC)

So, I think this explanation is under-focused on the actual joke. The core humor here is the idea that "Platonic Solid" means "Solids Plato made" and not regular polyhedra at all. "Mathmetitions long believed there were five platonic solids, all regular polyhedra" So the jorb is explicitly a platonic solid that is not a regular polyhedra. Our explanation should point out then, things like the fact that the platonic solids predate Plato.

:I'd like the answer to two questions:
:# What is CG even talking about?
:# What is the person who keeps removing CG's comment even complaining about? (Something about Cultural Misappropriation, but ''which'' culture(s)?)
:...maybe the answer to one will answer the other, but I've a feeling they're entirely unconnected. Perhaps one (or both?) just trolling. Yet, unless 7/7 is International Dungeons&Dragons™ Day, or something, neither even close to what I'm imagining it's about. [[Special:Contributions/172.71.242.96|172.71.242.96]] 10:50, 9 July 2023 (UTC)
::That post first appeared in June. [[Special:Contributions/172.71.154.17|172.71.154.17]] 23:45, 9 July 2023 (UTC)
'''Stop your games'''. And they clearly ''are'' games, as we already know about the historic link between the [https://www.explainxkcd.com/wiki/index.php?title=Talk:2781:_The_Six_Platonic_Solids&diff=next&oldid=317682 .XXX and CG-styled accounts], which you (singular/plural, I don't care) have now used to 'edit war between yoursel(f/ves)'. I don't generally care if the comment is there (whatever it even refers to, but with no obvious 'illegality') or not, but useless reverts/de-reverts/re-reveets/etc should not be tolerated. [[Special:Contributions/172.70.91.53|172.70.91.53]] 08:06, 11 July 2023 (UTC)
Ha, CG started to fight against himself! Hee-Ha! Hung-Huh-Ha-Hey! [[Special:Contributions/162.158.166.205|162.158.166.205]] 23:01, 11 July 2023 (UTC)

I wonder if this is relevant: http://www.hrwiki.org/wiki/A_Jorb_Well_Done {{unsigned ip|162.158.62.141|3:47, 2 July 2023}}