explain xkcd - User contributions [en]

283: Projection

2021-11-25T20:52:57Z

172.69.71.177: Added incomplete tag

{{comic
| number = 283
| date = June 29, 2007
| title = Projection
| image = projection.png
| titletext = Out in a field, not another car for miles, silence but for the rain drumming on the sunroof, warm thick folds of the blanket hiding wordless fingertip games...
}}

==Explanation==
{{incomplete|Created by a PROJECTOR DISGUISED AS A MONITOR. Please add an explanation for the title-text. Do NOT delete this tag too soon.}}

[[Cueball]] and [[Megan]] are watching a movie on a couch. During the movie, a scene features a character's face with legible text projected by the monitor. Though commonly depicted for dramatic effect, this phenomenon does not actually occur with conventional monitor technology. Megan is annoyed and agitated by the inaccuracy of the effect. Cueball agrees and delves more into the optical underpinnings of projected images, but in the process segues into a romantic memory of the two of them in a parked car in the rain.

At that point, the two lose interest in the movie and begin making preparations to drive to the nearest rainstorm for another romantic evening experience.

This was the second time in four months that [[Randall]] mentions [[:Category:Pet Peeves|Pet Peeves]]. The first was [[238: Pet Peeve 114]]. The next, [[1138: Heatmap]], did not appear until more than five years later.

==Transcript==
:[Cueball and Megan are seated on a couch, watching TV.]
:Megan: Argh, movie pet peeve- Someone sitting at a computer in the dark with the screen projected on their face. Monitors don't work like that!

:[Cueball and Megan face each other on the couch.]
:Cueball: Right - that only happens if you're in the way of a projected image. Like when we're sitting together in a parked car in the rain and the mottled light through the raindrops on the windshield makes shifting shadows on your skin...

:[Beat panel.]

:[Megan stands up, Cueball uses a laptop on table behind the couch.]
:Megan: ...I wasn't really into the movie anyway.
:Cueball: The nearest rainstorm's about 60 miles away.
:Megan: We'll drive fast.
:Cueball: I'll grab some snacks.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Romance]]
[[Category:Pet Peeves]]

Talk:2527: New Nobel Prizes

2021-10-13T13:25:07Z

172.69.71.177:

I can't understand the title text --[[User:GcGYSF(asterisk)P(vertical line)e|GcGYSF(asterisk)P(vertical line)e]] ([[User talk:GcGYSF(asterisk)P(vertical line)e|talk]]) 02:33, 12 October 2021 (UTC)
:I think it's implying that they're so desperate to stop Dr. Adams that they're offering a Nobel Prize to whoever gets her to stop. [[Special:Contributions/162.158.63.21|162.158.63.21]] 03:09, 12 October 2021 (UTC)
I think the comic is riffing on the gender imbalance. We're led to expect the dialogue to say all this year's Nobel prizes went to men (which in 2021 they did - which was newsworthy). ---- {{unsigned|141.101.107.229 who didn't use tildes}}
: Indeed, because there is no Nobel Prize for Mathematics laureate to tell them that the odds of this happening are 1/64, which isn't *that* surprising, especially given that the gender imbalance, (for whatever reason(s), good or bad) mean that the odds are actually higher because it's not an even 50/50 chance to pick a specific gender per 'coin flip.' For instance if the split were 75:25 in favor of women, then the odds of an all-female prize winning year would be ~18%, which means that at least every 6th year random chance should deliver a all-female-winner year if genders really do have no role in awarding winners. Ergo, it's only newsworthy if you have a political angle.[[Special:Contributions/172.69.68.235|172.69.68.235]] 16:40, 12 October 2021 (UTC)

I think it's more like discovering new particles, than elements, with some sort of Enhanced Standard Model of Nobel Prizes probably being added to by the likes of supersymmetric partners, Higgses, etc. (But might be worth a mention that (pure) Mathematicians conspicuously miss out Nobel glory due to a deliberate oversight/snub? Not that I have skin in that game, but it's a known fact.) [[Special:Contributions/162.158.159.53|162.158.159.53]] 08:29, 12 October 2021 (UTC)

This is probably also a jab at the "Nobel prize for Economics", which was awarded yesterday. That prize exists since the 1970s, but is often not regarded as a "real" Nobel prize because it was not specified in Alfred Nobel's will, but is rather the result of an outside donation. One could say it is a unrelated prize that is just cleverly marketed by smuggling Alfred Nobel's name into it and by awarding it one day after the "real" Nobel prizes. In that way, one could thoretically create a near infinite number of new "Nobel prizes" for irrelevant stuff, as the comic suggests. -[[Special:Contributions/162.158.91.90|162.158.91.90]] 09:05, 12 October 2021 (UTC)

Could this be a riff on the AAAI Squirrel AI award given recently, which people are calling a "new Nobel"? https://pratt.duke.edu/about/news/rudin-squirrel-award --[[User:Sophira|Sophira]] ([[User talk:Sophira|talk]]) 10:49, 12 October 2021 (UTC)
:It's pretty cmomon for the most prestigious award in some other field of study to be figuratively called the "Nobel of X". For instance, the Turing Award could be considered the Nobel Prize of computing. So I doubt this is a riff on any particular industry award, especially since it was published just after all the Nobel Awards were announced. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 18:13, 12 October 2021 (UTC)

Swede here, on a little minor issue. As far as I know, Alfred Nobel was never knighted, so he should not be called Sir, which he currently is in the text.

I added an explanation for the title text as there was none previously. I feel like someone else could've explained it much better that I could, however.[[User:MrYellow04|MrYellow04]] ([[User talk:MrYellow04|talk]]) 17:33, 12 October 2021 (UTC)

Today is the 42nd anniversary of Douglas Adams's ''The Hitchhiker's Guide to the Galaxy'', so it is possible Randall is referencing him with the name of Dr. Adams. [[Special:Contributions/172.70.114.3|172.70.114.3]] 18:48, 12 October 2021 (UTC)

It may be worth noting that Dr. Adams [[1954: Impostor Syndrome|is a social psychologist and the world's top expert on impostor syndrome]]. [[Special:Random|Kpalion]] 10:59, 13 October 2021 (UTC)
: Oh man, you're right. [[Category:Doctor_Ponytail|And she's also frequently depicted wearing a lab coat in the role of a medical doctor.]] I know there's a lot of precedent in this wiki for calling her Ponytail, but I'm wondering if "Dr. Adams" could theoretically be used ''whenever'' she appears, as we do with Megan. --mezimm [[Special:Contributions/172.69.71.177|172.69.71.177]] 13:25, 13 October 2021 (UTC)

2526: TSP vs TBSP

2021-10-08T18:00:11Z

172.69.71.177:

{{comic
| number = 2526
| date = October 8, 2021
| title = Tsp vs Tbsp
| image = tsp_vs_tbsp.png
| titletext = It's like one teraspoon / when all you need is a kilonife
}}

==Explanation==
{{incomplete|Created by ALANIS TURINGETTE - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This comic plays a joke on the common liquid measurements of {{w|teaspoon}}s (tsp) and {{w|tablespoon}}s (tbsp), which are commonly confused. A teaspoon is defined as 5 mL (0.18 imp fl oz; 0.17 US fl oz) while a tablespoon is defined as 14.8 ml (0.50 US fl oz) in the US.

It also plays a joke on metric measurements (which use powers of 10) versus computer measurements (which use powers of 2), which also cause confusion. See also [[394: Kilobyte]].

The title text is a play on a lyric from the Alanis Morissette song "{{w|Ironic (song)|Ironic}}": It's like ten thousand spoons when all you need is a knife. Randall changes the line to "teraspoon" and "kilonife".

If "spoon" is understood as teaspoon, then one teraspoon will be 5000 cubic meters and a binary teraspoon will be 5497,6 cubic meters. If the tablespoon is taken as base unit, a teraspoon will be 14800 cubic meters and a binary teraspoon 16272,8 cubic meters. Both volumes are much too large to fit inside a typical residential kitchen.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:Cooking tips: tsp vs tbsp

:[left column:]
:<big>Tsp</big>
:Teraspoon
:1,000,000,000,000
:(1012) spoons

:[right column:]
:<big>Tbsp</big>
:Binary tsp
:1,099,511,627,776
:(10244) spoons

{{comic discussion}}
[[Category:Programming]]
[[Category:Tips]]

Talk:2522: Two-Factor Security Key

2021-09-30T04:41:56Z

172.69.71.177:

There are 2FA USB keys (WebAuthn, FIDO2, U2F) such as
https://shop.nitrokey.com/shop/product/nk-fi2-nitrokey-fido2-55 with a hole to attach a keychain - and the item in the last panel looks a bit like such one [[User:Bmwiedemann|Bmwiedemann]] ([[User talk:Bmwiedemann|talk]]) 03:48, 30 September 2021 (UTC)
:: First thing that comes to mind when someone mentions a 2FA security key. 100% most certainly what they are talking about. yubikey/fido2 being the ones that popularized it iirc [[Special:Contributions/172.69.71.177|172.69.71.177]] 04:41, 30 September 2021 (UTC)

Talk:2509: Useful Geometry Formulas

2021-08-31T12:46:55Z

172.69.71.177:

Area formulas are for 2D object as seen instead of surface of a projected 3D object. Sebastian --[[Special:Contributions/162.158.89.200|162.158.89.200]] 02:36, 31 August 2021 (UTC)

The "decorative stripes and dotted lines" are the parts of the diagrams that are intended to indicate the third dimension. The conceit of the comic is that these are superfluous. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 02:56, 31 August 2021 (UTC)

Ca someone explain how the last one works? [[User:GcGYSF(asterisk)P(vertical line)e|GcGYSF(asterisk)P(vertical line)e]] ([[User talk:GcGYSF(asterisk)P(vertical line)e|talk]]) 04:28, 31 August 2021 (UTC)

: ''bh'' is the area of the front face. The top face is a parallelogram with sides ''d'' and ''b'', with an angle of ''θ'' between them, so its area is ''d b sin(θ)''. The right face is a parallelogram with sides ''d'' and ''h'', with an angle of ''90º - θ'' between them, so its area is ''h d sin(90º - θ) = h d cos(θ)''. So the area of the whole picture is ''bh + d b sin(θ) + d h cos(θ)''.
: --[[Special:Contributions/172.68.24.165|172.68.24.165]] 04:46, 31 August 2021 (UTC)

:: In case you don't know the area of a parallelogram by heart, you can read d b sin(θ) as b * d sin(θ), where d sin(θ) is the height of the parallelogram; if you cut the right corner of the parallelogram off and add it on the left, you get a rectangle where the bottom side is b and the height is that d sin(θ), so it works out. The other parallelogram's area is h * d cos(θ), with the same reasoning. [[Special:Contributions/162.158.90.241|162.158.90.241]] 05:00, 31 August 2021 (UTC)

Funnily enough, both this comic and [[2506]] are about projection. [[User:CRLF|CRLF]] ([[User talk:CRLF|talk]]) 05:11, 31 August 2021 (UTC)

: I had considered working that into the explanation, but that needs to account for the fact that the indicated measurements (e.g. the angle θ) have to be read in 2D, not in 3D and projected. But it would be correct to say that the 2D shapes are projections of simple 3D objects. [[Special:Contributions/162.158.90.149|162.158.90.149]] 05:23, 31 August 2021 (UTC)

;Does the bottom-left formula have a mistake?</s>
It seems like the bottom-left formula should be ''A''=''d''(''πr''+''h'') rather than ''A''=''d''(''πr''/2+''h''), because there are two half-ellipses that add up to a complete ellipse. Am I missing something? (This doesn't ''seem'' like an extra joke, does it?) [[Special:Contributions/162.158.106.179|162.158.106.179]] 05:28, 31 August 2021 (UTC)
: No, it's correct. ''d'' is all of the major axis, not just half, so we have to divide that by ''2''. [[Special:Contributions/162.158.92.83|162.158.92.83]] 05:51, 31 August 2021 (UTC)
:: Oh, right; good call! [[Special:Contributions/162.158.106.179|162.158.106.179]] 06:49, 31 August 2021 (UTC)

;Does the top-right formula have a mistake?
I think it should be in brackets, the top triangle area needs the ''1/2'' also, so it should be: ''A''=''1/2(πab + bh)''
:No, it's correct. The bottom is a half ellipse, with area ''1/2 π a b'', and the top is a triangle with base ''2 b'' and height ''h'', so its area is ''1/2 2b h = bh''. The total area is ''1/2 π a b + b h''.
--[[Special:Contributions/172.68.25.144|172.68.25.144]] 06:49, 31 August 2021 (UTC)

;3D formulae for reference:
''4πr^2''

''πb(a+√(b^2+h^2))'' if a=b

''πr(2r+h)''

''2(bd+bh+dh)''

[[Special:Contributions/162.158.107.80|162.158.107.80]] 09:54, 31 August 2021 (UTC)
:It would be clarifying to add these to the comic, but of course they are flagrantly wrong. [[User:Baffo32|Baffo32]] ([[User talk:Baffo32|talk]]) 09:57, 31 August 2021 (UTC)
::Surely ripe for a table, in place of much of the longhand paragraph spiel (which could be kept, but simpler for just the narrative but otherwise non-technical details)... "Shape (2D)", "Area", "Pretended Shape (3D)", "Surface Area", "Volume", ¿"Notes"? (Not sure about specific Notes, some things could/should be said below the formulae/descriptions in the relevent cell to which that matters, in special cases where necessary, which might be better than a Notes either empty or jammed up with all the combined row-specific corollaries, etc, that I can imagine.) Anyway, an idea. [[Special:Contributions/141.101.76.11|141.101.76.11]] 11:56, 31 August 2021 (UTC)
:::I think the formulas are correct. Those given should be from the text book, not for those with ellipse bases. Someone has put a lot of work into giving these complicated formulas for the cone and cylinder. But I think that is overkill. I have added to the explanation the simple versions before, and would suggest deleting the complicated, which was never the intention of either text book or Randall! ;-)--[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 12:36, 31 August 2021 (UTC)

add an extra edited image that is the comic without dotted lines to make it easier to see the 2d shapes? [[Special:Contributions/172.69.71.177|172.69.71.177]] 12:46, 31 August 2021 (UTC)Bampf