explain xkcd - User contributions [en]

Talk:2562: Formatting Meeting

2022-01-05T15:04:06Z

141.101.104.8:

I downloaded and ran theusaf's bot from its website to make this page. Not sure how to give page creation permission to [[User:Baffo32RunningTheusafBOT]]. When you run the bot you notice that Theusaf's username is "the usa f". [[Special:Contributions/172.70.110.45|172.70.110.45]] 16:02, 31 December 2021 (UTC)
:The bot should be back up. The hosting service has some maintenance, which turned it off. [[User:Theusaf|theusaf]] ([[User talk:Theusaf|talk]]) 01:25, 2 January 2022 (UTC)

shouldn't it be ISO, not iso? actually, the whole title text is lowercase-d when I feel like it shouldn't be [[Special:Contributions/172.70.35.70|172.70.35.70]] 16:59, 31 December 2021 (UTC)Bumpf
: you're probably right. as a geek, one uses lowercase 'iso' all the time in computer date code where it is usually lowercase. e.g. i type `date --iso=seconds` every day into my linux terminal; it outputs 8601 format. [[Special:Contributions/172.70.114.167|172.70.114.167]] 19:23, 31 December 2021 (UTC)

Speaking as a European, we'd often read 2/3/22 as "2nd March 2022" (same order as the numbers), not "March 2, 2022", though obviously we'd understand both expressions. Also, the suggestion that the thousands/decimal punctuation is reversed in the EU is wrong, as this does not apply to all countries of the EU. For example, Ireland uses the same as the US (and the same as the UK, though that is no longer part of the EU and might eventually give up decimalisation altogether on account of fractions being more wholesome...) [[User:Rotan|Rotan]] ([[User talk:Rotan|talk]]) 18:47, 31 December 2021 (UTC)
:You mean the 12-times-tables, that I was thoroughly taught when I was young, might (literally) gain currency once more? That'll be interesting! [[Special:Contributions/172.70.85.73|172.70.85.73]] 16:42, 1 January 2022 (UTC)

Another comic which references ISO-8601 is: https://xkcd.com/1179/ [[User:Rps|Rps]] ([[User talk:Rps|talk]]) 21:27, 31 December 2021 (UTC)

It's been more than 20 years since in 'casual' date writing I started prefering "D/Mmm/YYYY" format (today is 31/Dec/2021, for me right now, tomorrow is 1/Jan/2022) when I had a totally free hand. A combination of indicating to US colleagues in my multinational company of that time that I wasn't writing trying to write Jan/1/2022 (not that it would matter in that particular case!) and doing my bit to support the upcoming Y2K-compatability issues that other people were gradually getting to know about. Though for coded dates, YYYYMMDD[.hh[mm[ss[...]]]] always worked best for me. It numerically sorts (it will even when YYYY eventually becomes YYYYY!) and can be given arbitrary sub-day specification - at least until float-rounding errors start to creep in. [[Special:Contributions/172.70.90.43|172.70.90.43]] 22:25, 31 December 2021 (UTC)
: Elements of Style already recommended the Notation D Mmm YYYY already in 1923. It is the only sensical solution to the problem other than the technical ISO 8601. --[[Special:Contributions/172.68.110.121|172.68.110.121]] 09:07, 3 January 2022 (UTC)

Around year 2000 there was short time when people were writing the years properly. Afterwards, the laziness won again and people started using just two digits again ... sigh ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 01:19, 1 January 2022 (UTC)

Is localization spelled localisation in countries that use English? [[User:Boatster|Boatster]] ([[User talk:Boatster|talk]]) 01:59, 1 January 2022 (UTC)
:It is. Obviously that excludes the US and any other past colonials who picked up the wrong habit along the way. ;) [[Special:Contributions/172.70.86.22|172.70.86.22]] 02:18, 1 January 2022 (UTC)

:Actually, the -ise/-ize distinction only came in in UK English quite recently and some UK publishers still use -ize endings. I was told both endings were OK at school in the UK in the sixties.[[Special:Contributions/172.70.86.68|172.70.86.68]] 09:46, 1 January 2022 (UTC)

::I treat the Oxford Spelling with the respect I give the Oxford Comma. None. (My own '70s education drummed that into me, and it's not going to change easily.) [[Special:Contributions/172.70.90.71|172.70.90.71]] 11:56, 1 January 2022 (UTC)

Anyone who doesn't use ISO-8601 dates should be shot on sight. [[User:SDSpivey|SDSpivey]] ([[User talk:SDSpivey|talk]]) 10:24, 1 January 2022 (UTC)
:Must include yourself, look at your signature!!! :-D --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 13:49, 2022-01-03 (UTC)

I got the impression that slashes as separators mark us-notation and dashes EU notation. [[Special:Contributions/162.158.88.139|162.158.88.139]] 11:36, 1 January 2022 (UTC)
:The UK complicated this notation (don't we always!). We typically use 'European' ordering (or maybe they use ours?) but also slashes (whichever side of the Atlantic that started). This makes it not so easy to just assume dd-mm-yyyy and mm/dd/yyyy differentiate by separator used. Not sure how to rewrite "In Europe, the usual order is day/month/year - although the slash is rarely used as the separator" in light of this. Are we 'rare' in Europe, or no longer to be considered that at all and therefore not even discussed? [[Special:Contributions/172.70.85.73|172.70.85.73]] 16:38, 1 January 2022 (UTC)
::We use the same notations as you in France (and it's very rare when our two countries do the same thing), so I'm not sure the "rarely used as a separator" is correct. [[User:Cochonou|Cochonou]] ([[User talk:Cochonou|talk]]) 17:32, 1 January 2022 (UTC)
:In France we mainly use slashes, with DD/MM/(YY)YY, so yeah not at all and we're always really confused with USian dates, even more because it's not reflected in our language (January the 2nd of 2022 => 2 janvier 2022). [[Special:Contributions/108.162.229.233|108.162.229.233]] 19:16, 1 January 2022 (UTC)
::Don’t you mean 13 Nivôse CCXXX --[[Special:Contributions/172.70.131.70|172.70.131.70]] 06:26, 5 January 2022 (UTC)
::In Denmark we usually write 2/3 2022 for March 2nd. I would of course prefer 2022-03-02. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 13:48, 3 January 2022 (UTC)
:::In Germany we use dots as separators: 2022-03-02 => 02.03.2022 or 02. März 2022. --[[Special:Contributions/141.101.104.8|141.101.104.8]] 15:04, 5 January 2022 (UTC)

The discussion of currency seems way too much for something that isn't actually part of the comic. I believe it would be better in trivia, if part of the article at all. [[User:Nitpicking|Nitpicking]] ([[User talk:Nitpicking|talk]]) 13:36, 1 January 2022 (UTC)
-- concur with that. Its also annoying as on the east of the atlantic, I'd be writing 10^5 as 100,000 not 100.000

In Sweden we use ISO-8601 (YYYY-MM-DD, 2022-03-02), but it is also common to use YY-MM-DD (22-03-02) or YYMMDD (220302). And the bastard D/M-YY (3/2-22). [[Special:Contributions/141.101.104.14|141.101.104.14]] 22:17, 2 January 2022 (UTC)

Isn't the joke really that there was originally only one localization working group, but they were inept at localization? The group set a date for its next meeting, but did not consider that people in different regions would interpret the date differently. Now, in order to cover up their incompetence, the group is pretending they meant to have two separate meetings based on the two interpretations of the date. At least, I thought that was funnier... {{unsigned ip|172.70.114.253}}

Since everyone is adding the common formats from their European country here is the traditional German one: dd.mm.(yy)yy - so the 2nd of March this year would be 2.3.22 (or 2.3.2022 - or even to show that there is something omitted: 2.3.'22) Haven't seen a slash or dash being used in date formatting by a German who is writing in German. But working in an international setting of course brings forward all kinds of hybrids, when Germans write in English, etc. --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 08:17, 5 January 2022 (UTC)
::With a leading null (if necessary) for dd.mm.yy is vastly more common: 02.03.09 is 2009-03-02. --[[Special:Contributions/141.101.104.8|141.101.104.8]] 15:04, 5 January 2022 (UTC)

Talk:162: Angular Momentum

2015-12-06T22:13:13Z

141.101.104.8:

The issue date is not given, as i don't have a clue about it. Could someone fix this? [[User:Rikthoff|Rikthoff]] ([[User talk:Rikthoff|talk]]) 19:30, 3 August 2012 (EDT)

:When the page was updated to the new comic template by [[User:Bpothier]] he fixed the date. [[User:Lcarsos|lcarsos]] ([[User talk:Lcarsos|talk]]) 20:48, 28 August 2012 (UTC)

That actually is a neat physics puzzle, which has probably (i.e. certainly) been addressed somewhere on the net. I may incorporate that some day. --[[User:Quicksilver|Quicksilver]] ([[User talk:Quicksilver|talk]]) 05:58, 24 August 2013 (UTC)

I tried to calculate the change in Earth's period, assuming that she was standing in the north pole (latitude = 90º N), where her spinning would have more effect. I either did something wrong, or my TI-84 Plus is not capable of detecting the very small effect her spinning would have on the Earth's rotation. I assumed the Earth had a period of exactly 24 hours, and got the same value to the second, even if she was spinning at 1000 turns per second, which seems like a lot.

Here's the formula:

L_Earth_i = L_Earth_f + L_spinner <=>

I_Earth * (2*PI)/T_Earth_i = I_Earth * (2*PI)/T_Earth_f + I_spinner* (2*PI) * f_spinner <=>

(1/T_Earth_f) = (1/T_Earth_i) - (I_spinner/I_Earth)*f_spinner <=>

T_Earth_f = 1/((1/T_Earth_i) - (I_spinner/I_Earth)*f_spinner)

Where the variables have names in the format:

[variable name]_[object it refers to]_[situation (i or f stand for initial and final)]

L = Angular Moment

I = Moment of Inertia

T = Period of rotation about one's axis

f = frequency

I used as values:

T_Earth_i = 86400 seconds (24 hours exactly)

I_spinner = 62,04 Kg.m^2 (Found on Wolfram|Alpha, for a 62Kg adult human being)

I_Earth = 8,03e+37 Kg.m^2 (http://scienceworld.wolfram.com/physics/MomentofInertiaEarth.html)

f_spinner = the frequency of the woman's spinning in complete turns per second. {{unsigned ip|2.82.142.28}}

:Taking that a bit further, the relative decrease is:

(T_Earth_f - T_Earth_i)/T_Earth_i = 1 / (I_Earth/(I_spinner*T_Earth_i*f_spinner) - 1)
= 1 / ( 1.5 e+28 - 1) ~= 67 e-30

:Fwiw, the absolute value is 5.767 yocto-seconds. If the ''entire'' world population would spin at that 1000 turns per second (and at favourable locations as in your assumptions), the effect will still be a measly 0.041 pico-seconds. So T_Earth_f = 86 399.999 999 999 999 958 ... But the TI-84 only has about 14 digits precision, i believe, so even that won't show up. -- [[Special:Contributions/173.245.51.210|173.245.51.210]] 22:46, 30 October 2013 (UTC)

Is it possible for someone to write an equation that factors in latitude (and, if relevant, longitude) that we could plug our locations into and get a value from? That would be awesome. Thanks. [[Special:Contributions/108.162.250.208|108.162.250.208]] 02:48, 23 February 2014 (UTC)

The visual style and theme of this comic is clearly referencing the 'Spinning Ballerina Optical Illusion' (evidenced by the grey-to-white gradient 'glow', as well as her arm and leg positions).
[[Special:Contributions/108.162.249.231|108.162.249.231]] 03:03, 30 September 2014 (UTC)

The 'Spinning Ballerina' optical illusion does not apply here, Megan clearly stated that she was spinning 'counterclockwise' and due to the fact that she is drawn with hair (not a silhouette) lets you know where she is facing. Therefore the bent leg on the right of the image is her left leg. Plus there aren't many ways to draw a stick figure 'spinning'. Now if it were Cueball doing the spinning THEN I would agree with you because there would not be a reference point to make any type of judgement and therefore a point could be made that could be a reference Randall was trying to make.
[[User:Nexxuz|Nexxuz]] ([[User talk:Nexxuz|talk]])

The momentum of Megan is in fact one order of magnitude smaller than what appeared in above calculation, so the dilation effect is still smaller.

http://www.wolframalpha.com/input/?i=moment+of+inertia+of+solid+cylinder+for+a%3D0.25m%2Cmass%3D62kg {{unsigned ip|173.245.50.90}}

After reading this comics, I got one question. I thought one cant change the total momentum of a closed system of bodies. I mean, from the point of view outside of Earth, she would be spinning, but the momentum which Megan, or whatever her name is, gained in counter-clock-wise direction would also show in Earth clock-wise direction (positively). Basically I am referring to a situation of a man walking on a boat. (the boat moves, the man moves, but the position man-lake is still the same). So I figured it should be in this way. She spins, yeah, but the Earth now spins in opposite direction a little more, so in the end it is still the same.
Now, she could totally delay time by approaching light speed as she spins, which would be weird though as her head (closer to rotational axis) would have smaller velocity than her hands (and thus faster time flow) resulting in, hmm, her body parts getting lost in time? {{unsigned ip|141.101.97.220}}

:The total angular momentum cannot be altered from inside the closed system, but it can be distributed differently among the different bodies. This means that the angular speed of the Earth will be actually reduced, but only of a fixed value (proportional to Megan's angular speed) and only as long as Megan spins. It will revert to its original value when Megan stops spinning.

Wouldn't she have to be spinning at the Geographic North Pole to have any effect? As it is she's spinning with her axis of rotation at some angle (depending on latitude ) to the Earth's axis of rotation so she's not having much of any effect at all. [[Special:Contributions/173.245.54.190|173.245.54.190]] 10:15, 2 April 2015 (UTC)

Is she spinning counter clockwise when viewed from below or above? (Up spin or down spin?) [[Special:Contributions/108.162.219.188|108.162.219.188]] 06:35, 24 June 2015 (UTC)

Talk:162: Angular Momentum

2015-12-06T21:58:06Z

141.101.104.8:

The issue date is not given, as i don't have a clue about it. Could someone fix this? [[User:Rikthoff|Rikthoff]] ([[User talk:Rikthoff|talk]]) 19:30, 3 August 2012 (EDT)

:When the page was updated to the new comic template by [[User:Bpothier]] he fixed the date. [[User:Lcarsos|lcarsos]] ([[User talk:Lcarsos|talk]]) 20:48, 28 August 2012 (UTC)

That actually is a neat physics puzzle, which has probably (i.e. certainly) been addressed somewhere on the net. I may incorporate that some day. --[[User:Quicksilver|Quicksilver]] ([[User talk:Quicksilver|talk]]) 05:58, 24 August 2013 (UTC)

I tried to calculate the change in Earth's period, assuming that she was standing in the north pole (latitude = 90º N), where her spinning would have more effect. I either did something wrong, or my TI-84 Plus is not capable of detecting the very small effect her spinning would have on the Earth's rotation. I assumed the Earth had a period of exactly 24 hours, and got the same value to the second, even if she was spinning at 1000 turns per second, which seems like a lot.

Here's the formula:

L_Earth_i = L_Earth_f + L_spinner <=>

I_Earth * (2*PI)/T_Earth_i = I_Earth * (2*PI)/T_Earth_f + I_spinner* (2*PI) * f_spinner <=>

(1/T_Earth_f) = (1/T_Earth_i) - (I_spinner/I_Earth)*f_spinner <=>

T_Earth_f = 1/((1/T_Earth_i) - (I_spinner/I_Earth)*f_spinner)

Where the variables have names in the format:

[variable name]_[object it refers to]_[situation (i or f stand for initial and final)]

L = Angular Moment

I = Moment of Inertia

T = Period of rotation about one's axis

f = frequency

I used as values:

T_Earth_i = 86400 seconds (24 hours exactly)

I_spinner = 62,04 Kg.m^2 (Found on Wolfram|Alpha, for a 62Kg adult human being)

I_Earth = 8,03e+37 Kg.m^2 (http://scienceworld.wolfram.com/physics/MomentofInertiaEarth.html)

f_spinner = the frequency of the woman's spinning in complete turns per second. {{unsigned ip|2.82.142.28}}

:Taking that a bit further, the relative decrease is:

(T_Earth_f - T_Earth_i)/T_Earth_i = 1 / (I_Earth/(I_spinner*T_Earth_i*f_spinner) - 1)
= 1 / ( 1.5 e+28 - 1) ~= 67 e-30

:Fwiw, the absolute value is 5.767 yocto-seconds. If the ''entire'' world population would spin at that 1000 turns per second (and at favourable locations as in your assumptions), the effect will still be a measly 0.041 pico-seconds. So T_Earth_f = 86 399.999 999 999 999 958 ... But the TI-84 only has about 14 digits precision, i believe, so even that won't show up. -- [[Special:Contributions/173.245.51.210|173.245.51.210]] 22:46, 30 October 2013 (UTC)

Is it possible for someone to write an equation that factors in latitude (and, if relevant, longitude) that we could plug our locations into and get a value from? That would be awesome. Thanks. [[Special:Contributions/108.162.250.208|108.162.250.208]] 02:48, 23 February 2014 (UTC)

The visual style and theme of this comic is clearly referencing the 'Spinning Ballerina Optical Illusion' (evidenced by the grey-to-white gradient 'glow', as well as her arm and leg positions).
[[Special:Contributions/108.162.249.231|108.162.249.231]] 03:03, 30 September 2014 (UTC)

The 'Spinning Ballerina' optical illusion does not apply here, Megan clearly stated that she was spinning 'counterclockwise' and due to the fact that she is drawn with hair (not a silhouette) lets you know where she is facing. Therefore the bent leg on the right of the image is her left leg. Plus there aren't many ways to draw a stick figure 'spinning'. Now if it were Cueball doing the spinning THEN I would agree with you because there would not be a reference point to make any type of judgement and therefore a point could be made that could be a reference Randall was trying to make.
[[User:Nexxuz|Nexxuz]] ([[User talk:Nexxuz|talk]])

The momentum of Megan is in fact one order of magnitude smaller than what appeared in above calculation, so the dilation effect is still smaller.

http://www.wolframalpha.com/input/?i=moment+of+inertia+of+solid+cylinder+for+a%3D0.25m%2Cmass%3D62kg {{unsigned ip|173.245.50.90}}

After reading this comics, I got one question. I thought one cant change the total momentum of a closed system of bodies. I mean, from the point of view outside of Earth, she would be spinning, but the momentum which Megan, or whatever her name is, gained in counter-clock-wise direction would also show in Earth clock-wise direction (positively). Basically I am referring to a situation of a man walking on a boat. (the boat moves, the man moves, but the position man-lake is still the same). So I figured it should be in this way. She spins, yeah, but the Earth now spins in opposite direction a little more, so in the end it is still the same.
Now, she could totally delay time by approaching light speed as she spins, which would be weird though as her head (closer to rotational axis) would have smaller velocity than her hands (and thus faster time flow) resulting in, hmm, her body parts getting lost in time? {{unsigned ip|141.101.97.220}}

:The total angular momentum cannot be altered from inside the closed system, but it can be distributed differently among the different bodies. This means that the angular momentum of the Earth will be reduced as long as Megan spins, and it will revert to its original value when Megan stops spinning.

Wouldn't she have to be spinning at the Geographic North Pole to have any effect? As it is she's spinning with her axis of rotation at some angle (depending on latitude ) to the Earth's axis of rotation so she's not having much of any effect at all. [[Special:Contributions/173.245.54.190|173.245.54.190]] 10:15, 2 April 2015 (UTC)

Is she spinning counter clockwise when viewed from below or above? (Up spin or down spin?) [[Special:Contributions/108.162.219.188|108.162.219.188]] 06:35, 24 June 2015 (UTC)