Editing Talk:2566: Decorative Constants

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I don't have any idea what to put in the actual description, but whoever does should probably note that r(in) - r(out) equals zero, not one. And multiplying by a constant 0 absolutely changes the value! [[User:GreatWyrmGold|GreatWyrmGold]] ([[User talk:GreatWyrmGold|talk]]) 21:59, 10 January 2022 (UTC)
: r<sub>out</sub> and r<sub>in</sub> are different values. The subscripts represent different instances of the same variable at different point. In the same way, you might calculate something happening over a time interval t<sub>end</sub> - t<sub>start</sub> . [[Special:Contributions/172.69.71.77|172.69.71.77]] 23:02, 10 January 2022 (UTC)
::Yes for sure they are two different values. On the other hand if μ is not 1 then the it is not just decorative! D on the other hand is just a proportionality constant, which may have a value other than 1. I have tried to put something in the explanation here. Quite a bit. Do not really now anything about Drag, so just took it from the wiki page. Also I hope someone can explain the formula in the image, as I'm sure it is just something about the flow, that would relate it to a drag equation. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 23:41, 10 January 2022 (UTC)

Note that the title text is pretty much word-for-word a repeat from Randall's book *How To*. In Chapter 11: *How to Play Football*, he misuses the drag equation, and mentions this fact in more depth, in a footnote. Bit of trivia! --[[Special:Contributions/162.158.134.79|162.158.134.79]] 23:13, 10 January 2022 (UTC)
:Nice, I will have to check up on that. Thanks. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 23:41, 10 January 2022 (UTC)
:Can confirm this, the book mentions that the "traditional tribute to Euler and Bernoulli" comes from Frank White's ''Fluid Mechanics'' textbook. [[User:Clam|Clam]] ([[User talk:Clam|talk]]) 01:08, 11 January 2022 (UTC)
:: There it is, page 266 in the 1986 2nd edition: "They both have a factor ½ as a traditional tribute to Bernoulli and Euler, and both are based on the projected area..." https://books.google.com/books?id=wGweAQAAIAAJ&q=traditional -- [[Special:Contributions/172.70.162.5|172.70.162.5]] 02:13, 11 January 2022 (UTC)
:::Great thanks have included both references in the explanation. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:32, 11 January 2022 (UTC)
:Wait, wouldn't the values be twice as big (rather than half as big) if you left off the 1/2? [[Special:Contributions/141.101.69.154|141.101.69.154]] 12:43, 11 January 2022 (UTC)
::No. If 1/2Cd = Constant, then the new constant would be half as big as Cd since Cd=2x constant. You would just put in the 1/2 in the new version of Cd, so the new Cd is half as big as the old, and the final result the same.--[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 10:44, 12 January 2022 (UTC)

Of course, the c^2 im e=mc^2 is just as decorative, when using natural units where c=1.... [[Special:Contributions/172.68.50.171|172.68.50.171]] 00:29, 11 January 2022 (UTC)
: And the resulting equation is then just e=m - or m=e which is beautiful and profound.  "Mass is Energy".  Without the complications, you stop thinking of it as a PROCESS for converting one into the other and get the more profound point that Mass and Energy are the exact same thing.  [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 03:33, 11 January 2022 (UTC)
: I respectfully disagree. The c² isn't decorative; mc² is a measure of energy and m is not. e=mc², like f=ma, still works even if you change the size of any of the basic units (of length, time, mass) from which the units of energy and force are derived. As I see it, an equation that ties you to any definition of unit size is less profound, not more. [[User:Tom239|Tom239]] ([[User talk:Tom239|talk]]) 17:21, 12 January 2022 (UTC)
:: To the sort of person who (thoughtfully) uses c=1, this feels a bit like saying that the "f" is profound in dist=sqrt[x^2+y^2+(z/f)^2], where of course I've measured xy-distances in miles and z-distances in feet, so f=5280ft/mi. Yes, it's entirely possible to choose different units for different coordinates, and if you're very accustomed to that then the conversion factors can be deeply important for your understanding of the system (and provide extra flexibility in your choice of units: you can easily use "f=1760yd/mi" if you'd prefer). But there's still a very well-defined sense in which sqrt[x^2+y^2+z^2] is the more fundamental equation, and the "f" is an unnecessary complication (however convenient it may be). Whether I'd call it "decorative"... I'm not sure. But I don't see this "f" as profound. [[User:Steuard|Steuard]] ([[User talk:Steuard|talk]]) 17:59, 29 May 2022 (UTC)

I think the 1/2 in the drag equation is intuitive. I understand that it is technically superfluous, but F=Pd*A and Pd=1/2*rho*u^2 so the 1/2 carries over intuitively. {{unsigned ip|172.70.98.15}}
:Agrees I had this written down in an early version of the explanation but that was edited out. Maybe I will put it in again.--[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 10:44, 12 January 2022 (UTC)

Drag coefficients could just as easily be half as big. This is true but how is their being unitless relevant? It's more about how defining constants is partially arbitrary.  [[User:Lev|Lev]] ([[User talk:Lev|talk]]) 08:07, 12 January 2022 (UTC)
:If Cd had a unit, say it was an energy which represented some relevant value for a given material, then it would not be correct to say that it was half as much, just because 1/2 came into the equation. But if it has no units, then it is just a constant saying something about the material, and then the 1/2 could in principle be absorbed without changing anything. But as stated above 1/2 actually has physical meaning in the way it enters the equation. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 10:44, 12 January 2022 (UTC)

:It doesn't make any difference. For instance, Coulomb's law works fine whether we write it F = -q<sub>1</sub>q<sub>2</sub>/(4πε<sub>0</sub>r<sup>2</sup>) or F = -kq<sub>1</sub>q<sub>2</sub>/r<sup>2</sup>. Similarly, if we had a factor of 2 in the gas law for some reason, that would just change the values of the gas constants.

I've seen the double-struck capital "D" used commonly as a symbol for the Domain of a function (While the double-struck "R" was used for the range in that context) [[Special:Contributions/162.158.63.243|162.158.63.243]] 21:16, 17 January 2022 (UTC)
:Any use of double-struck or bold capital R to mean something besides the set of real numbers can be considered nonstandard, like using + to represent a non-commutative function or using a fraktur lowercase c to represent anything other than the cardinality of the continuum. It happens of course, but it's not any kind of standard. [[User:EebstertheGreat|EebstertheGreat]] ([[User talk:EebstertheGreat|talk]]) 03:18, 20 August 2023 (UTC)

Does anybody know enough math to figure out what that equation is supposed to do? I really want to delete that tag.[[User:New editor|New editor]] ([[User talk:New editor|talk]]) 19:13, 25 January 2022 (UTC)

:The r terms are used in describing things like water treatment plants or dialysis machines, where you're trying to use fluid flow to regulate some solute.  If fluid balance is large, it means the "tank" is going to empty or dry out.  I guess T is the rate at which this happens.  Not really a math thing, more of an engineering thing, seems to me.

==Count down clock==
;Keep discussion of comic above this, and further discussion of countdown here below!!!
Any idea what's going on with the clock that's counting downwards in the banner?   Currently counting down from 20 days 16 hours? [[Special:Contributions/172.70.214.95|172.70.214.95]] 22:08, 10 January 2022 (UTC)
:(Simultaneous edit) What is the days-hours-minutes in the box above the comic referring to? The image itself is dated yesterday, as you can see by saving it. Worst-case-scenario, is this a countdown to the end of XKCD? [[Special:Contributions/108.162.245.223|108.162.245.223]] 22:11, 10 January 2022 (UTC)
:: It's going to hit zero at around midnight on Jan 31st 2022 CST? [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 22:16, 10 January 2022 (UTC)
:::'''Posted [[Talk:2565:_Latency#Countdown|this]] on the previous comics discussion. But lets take it here where there will be more traffic:''' --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 22:44, 10 January 2022 (UTC) -- Copy paste from previous comics discussion:
::::Damn you beat me to it ;-). But I have made a [[2565:_Latency#Trivia|Trivia]] here on this comics page and links to more detail on the [[xkcd Header text]] page. I believe you are a day of, but someone will likely correct me if I'm wrong. As I can see it will be January 31st, 9:59 in Randall's home town Boston.--[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:06, 10 January 2022 (UTC)
:::::But damned if I can wait. Sure millions will watch the page when it goes to zero! At least it is no April 1st. :-D --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:10, 10 January 2022 (UTC)
::::Yeah - you're right - I messed up.   So as I type this, it's Jan 10th 2022 at 4pm - 1600 hrs Mountain time - which is 1800 hours EST. At this moment, the countdown reads  20d 16h 0m - so Jan 30th + (18+16) hours = which is Jan 30th + 34 hours - which is Jan 31st + 10am in Boston (EST). [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 23:05, 10 January 2022 (UTC)
:::::Hey great, can see they agree in the link to reddit below. So happy I got it right both in UTC and Boston. It will be 15:59 here in DK. Not 16:00. ;-) --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 23:44, 10 January 2022 (UTC)

Counting down to Backwards Day? --[[Special:Contributions/162.158.91.88|162.158.91.88]] 23:28, 10 January 2022 (UTC)
:There's a reddit thread discussing it: https://www.reddit.com/r/xkcd/comments/s0oynl/xkcd_countdown_timer_20d_21h_49m_remaining_until/ I think the most likely guess is that Randall has a new book coming out. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 23:40, 10 January 2022 (UTC)
::Would still seem strange if it came out that day with only promotion before being a count down. But then again, he will have the xkcd communities boiling if he gives no other hint. So every one will see if he promotes a book. Also as they wrote at the time I looked at reddit I do not think it is the end of xkcd, or Webb related. Although Webb was the first I thought about. But I mean even if it came to L2 at that day, it is not going to any specific point but just in orbit. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 23:47, 10 January 2022 (UTC)

::The date fits the idea of it being Backwards Day (https://nationaldaycalendar.com/backward-day-january-31) but what about the choice of time? [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 03:38, 11 January 2022 (UTC)
:::Backwards day... Never head of it until now. Is it big in the US. I mean when looking after dates so obscure they are not mentioned on wikipedia then there are probably lots of things happening on that day? But maybe it is a think in the US? --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:48, 11 January 2022 (UTC)
:::: I haven't heard of it until now either, so it is probably one of the bajillions of holidays no one actually cares about, and is unrelated to the countdown. [[Special:Contributions/108.162.221.163|108.162.221.163]] 13:22, 11 January 2022 (UTC)Bumpf

Someone has noticed the image is changing with pixels added at the bottom left corner and is keeping track of it here: https://munvoseli.github.io/xkcd-countdown/ [[Special:Contributions/198.41.238.107|198.41.238.107]] 05:49, 11 January 2022 (UTC)
:Looks like an image is "moving" into the frame because at the moment you can see some white pixel in the lower left, i.e. the black part might end up as a line as part of some comic. [[Special:Contributions/162.158.89.8|162.158.89.8]] 08:31, 11 January 2022 (UTC)
::Thanks used that to pinpoint the start of the countdown. Have added this info to the header text page, and the original trivia. Also just added a line of trivia to this explanation with the link. This was when this comic came out most people noticed the count down. But it did came out while [[Latency]] was up. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:43, 11 January 2022 (UTC)
:::Speculating on what it could be, the only thing that makes sense at that angle is a character's arm. 04:47, 12 January 2022 (UTC)

The header changes page says that it's forcing "Friday" to move down to the next line. Not for me. Did he fix it, or is it browser-specific? [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 14:58, 11 January 2022 (UTC)

This is much more likely a count down related to the James Webb Space Telescope. At approximately the day the count down indicates the telescope will be orbiting the L2 gravitational spot.Perhaps most of the mirrors will be approximate place to allow for months of fine tuning. An example of a slightly similar idea is https://www.space.com/nasa-james-webb-space-telescope-next-steps
[[User:Punchcard|Punchcard]] ([[User talk:Punchcard|talk]]) 15:35, 11 January 2022 (UTC)

I think the Countdown should get its own entry. What do we think? [[User:Sure|Sure]] ([[User talk:Sure|talk]]) 16:25, 11 January 2022 (UTC)
: I think it should! What with the count itself, the speculation about what it could mean, and now the slowly arriving image (?) this seems like something beyond either of the two comics since it started! [[Special:Contributions/108.162.219.49|108.162.219.49]] 18:00, 11 January 2022 (UTC)
: I'm surprised it doesn't have one already. This is one of the more unique situations in a long while, more speculation could happen. [[User:Thisfox|Thisfox]] ([[User talk:Thisfox|talk]]) 22:26, 11 January 2022 (UTC)

If you take a look at this [[https://xkcd.com/count-wimRikmef/state|link]] it displays this: '''{"img":"72cb154b23f959f908f5dc8eb03069c6df3f0f54aae896a0e7ed27befb2ee639.png","start":"2022-01-10T17:00:00Z","target":"2022-01-31T15:00:00Z","until":"2022-01-11T20:55:38.205303701Z"}''' [[User:Hoodiesandboba|Hoodiesandboba]] ([[User talk:Hoodiesandboba|talk]]) 20:58, 11 January 2022 (UTC)
:To correct your link:
:"...If you take a look at this [https://xkcd.com/count-wimRikmef/state link] it displays..."
:As to where the "72cb154b23f959f908f5dc8eb03069c6df3f0f54aae896a0e7ed27befb2ee639.png" is rooted, I haven't dug into that (or what transforms might be being applied), but it looks like a manipulation of browser states might be able to prematurely reveal it. (I'm on mobile at the moment, and it's significantly more fiddly to poke into the page-scripting and markup than I can be bothered with this moment, but I know what I'd do with a good acreage of screen, mouse control and a proper keyboard to rattle away at. And the combined minds here surely can do even better than myself.) [[Special:Contributions/172.70.91.116|172.70.91.116]] 22:38, 11 January 2022 (UTC)

I think it counts down to Lunar New Year (the Year of the Tiger), as measured in Korea (the earliest timezone where that is celebrated). Actually, it reaches 0 one minute before the New Year, so maybe it will switch to seconds for the last minute. [[Special:Contributions/172.70.98.75|172.70.98.75]] 05:10, 12 January 2022 (UTC)