explain xkcd - User contributions [en]

2816: Types of Solar Eclipse

2023-08-16T22:38:10Z

172.71.147.59:

{{comic
| number = 2816
| date = August 16, 2023
| title = Types of Solar Eclipse
| image = types_of_solar_eclipse_2x.png
| imagesize = 501x572px
| noexpand = true
| titletext = The best place to be for a hug eclipse is a scenic natural area with good views and few clouds. The worst place to be is the lunar surface.
}}

==Explanation==
{{incomplete|Created by a DARK SHADOW OF A DRAGONITE THAT PERIODICALLY EATS THE SUN - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

There are various different types of {{w|solar eclipse}}. The comic purports to show and names a number of them, initially quite real and accurate before heading into traditional xkcd fantasticality.

The punchline is where he likens an eclipse to a 'hug' of the Moon by the Sun. This is of course, not practically possible.{{citation needed}} The Sun is 93 million miles or 150 million kilometers away from the Moon. Even if it was somehow moved towards touching distance by advanced sci-fi tech or a terrible disaster, the Moon would vaporize on contact with the Sun's plasma, thus not allowing for any sort of hug. In fact, we would not live very long if this happened, as the Earth would be baked by the Sun's light, then swallowed by its intense gravity.

In the title text, the hug eclipse is mentioned again, this time in regards to where the best location to be would be. First, normal advice is given about how the best way to view the eclipse would be in a scenic and natural area with few clouds. Then he mentions that the lunar surface would be the worst place to go in a solar hug - as it would be blasted with thousands of degrees of heat from the sun.

{| class="wikitable"
!Label
!Image
!Description
|-
|Partial
|Sun partly obscured by an offset occlusion
|Whenever the Moon does not totally line up with the Sun (for any or all observers), the 'shadow' will not cross the centre of the Sun. The parts of a full eclipse before second contact and and after third contact are also described as partial phases of the eclipsing event.
|-
|Total
|Sun entirely obscured by a slightly larger concentric occlusion
|When the Moon is close to perigee (or assisted by the Earth being at aphelion) during an eclipse, the Moon's apparent size is slightly larger than that of the Sun and will cover the whole solar disc. This is an astronomically useful effect, as well as aesthetically interesting to look at, as observers can study solar prominsnces and the atmosphere of the Sun while not being blinded by the glare of the bright 'surface' of the star.
|-
|Annular
|Sun partly obscured by a slightly smaller concentric occlusion
|With the Moon nearer its apogee (and/or the Earth at perihelion), the Sun instead has a larger angular size than the Moon and will not be totally covered even by the most central alignment of each body.
An eclipse can also be called "hybrid" (not illustrated in the diagram), by being seen as both Total and Annular by different observers. Those viewing at more extreme latitudes or more westerly/easterly (the eclipse being closer to dawn and dusk, local time) are viewing both Moon and Sun from slightly further away around the curve of the planet and so make the nearer Moon decreases in angular size proportionately greater than the much more distant Sun and so see annularity for the same eclipse for which others see totallity.
|-
|Oblate
|Oval Sun obscured by a concentric circle, except for at the edges of its major axis
|If the Sun were a grossly exagerated oblate (or prolate) spheroid, for any reason, the equatorial (or polar) bulge might extend significantly beyond the original limits of totality, or the narrower radii fall beneath the limits of the annular occlusion.
|-
|Interior
|Sun obscured at its edge by a thick ring, leaving its centre visible
|When an occluding object visibly larger than the Sun has a significant hole in the middle, only the rim of the Sun is blocked in the manner of an inverted annular eclipse.
|-
|Cuboid
|Sun obscured by a square cross-section
|In this example, the 'Moon' appears to be a cube, thus unable to "square the circle" of the solar disk. It must be perpendicularly orientated, as other twists of a true cubic (or cuboid) object might cause a rectangular or even hexagonal 'shadow'.
|-
|Transverse
|Obscuring circle drawn as a perpendicular plane intersecting the Sun on a centre-line
|This depicts the solar disc as two dimensional (and at annobkique angle) and the 'shadow' disc as a second 2d object somehow passing through the same space.
|-
|Saturnian
|Obscuring circle is given an oblique (shadow) ring system
|While it is theoretically possible that Saturn (and its rings) could eventually find itself in a position to cause a solar eclipse on Earth (and/or that Earth moves beyond Saturn, or that the Moon gains significant debris rings in its own right), this scenario isn't something we could see happening any time soon.
There are Saturnian moons that naturally travel behind their parent planet, but none that would ever see a near-Sun-sized Saturn doing so like this, and no human is yet in a position to directly see such an effect by any currently available means. However, probes sent to saturn have captured images[https://solarsystem.nasa.gov/news/13101/spectacular-eclipses-in-the-saturn-system/] of this type of eclipse
|-
|Hug
|Obscuring shape is pinched over at both sides by the respective overlapping edges of the Sun
|In this imagez it appears the Sun has extended its 'limbs' to affectionately hold the Moon, which might be problematic in several different ways.
|}

In all these images, the solar disc does not actually have a solid Moon in front of it, but a semi-transparent shadow, more typical of the representation of the Earth's solar shadow as it passes across the face of the Moon in a {{w|lunar eclipse}}. This may be an additional part of the humour.

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

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Astronomy]]

2746: Launch Window

2023-03-07T11:04:18Z

172.71.147.59: /* Explanation */

{{comic
| number = 2746
| date = March 6, 2023
| title = Launch Window
| image = launch_window_2x.png
| imagesize = 501x256px
| noexpand = true
| titletext = "Confirmed, we have to scrub." "Ugh, okay. I'll get the bucket and sponge."
}}

==Explanation==
{{incomplete|Created by a WINDEX-SCRUBBED LAUNCH WINDOW - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
A {{w|Launch window}} is a brief period of time in which a spacecraft can be launched from Earth's surface such that the spacecraft can reach its destination with the minimal amount (or an amount lower than a threshhold of acceptance) of energy expenditure.

This comic takes the concept of a "launch window" in a more literal direction, implying that they have an actual physical window that is only open at certain times. One character suggests moving the rocket outside in order to avoid issues that arise from dealing with the window, but gets pushback because moving the rocket outside would cause them to have to deal with more (again, literal) bugs.

The title text is a play on the two meanings of ''scrub'': 1. to rub with a (usually wet) sponge or brush to clean 2. to cancel (here: the launch of the rocket)

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

[First panel: Ponytail and Hairy can be seen sitting behind a console]

Ponytail: The launch window will only be open for another 90 minutes. We may have to scrub.

[Second panel: Slightly zoomed out, left from Ponytail and Hairy, Cueball can be seen behind a console as well]

Cueball: You know, given all our issues with the launch window,

[Third panel: Cueball turns around, facing the others]

Cueball: Have we thought abot moving the rocket outside?

Ponytail: Ugh, no. It's so sunny out.

Hairy: And there are bugs.

{{comic discussion}}
[[Category:Space]]
[[Category: Comics featuring Ponytail]]
[[Category: Comics featuring Cueball]]
[[Category: Comics featuring Hairy]]

Talk:2738: Omniknot

2023-02-18T03:37:50Z

172.71.147.59:

Down the middle, that's Granny, Reef, ...(k)not sure.., ?bow line and two half hitches? and something of a plaited-knot that the name escapes me entirely right now (but an extension of the other one I can't identify). I'm sure there's a handy online catalogue of knots, to reference, though, before I try to stumble over the side-knots too. [[Special:Contributions/172.71.242.172|172.71.242.172]] 16:05, 15 February 2023 (UTC)

Binding security maximized but unbinding security minimized. RIP, tethered sailor beneath a capsized boat. [[Special:Contributions/172.70.114.78|172.70.114.78]] 16:20, 15 February 2023 (UTC)

This comic is dead on for a facetious rock climbing saying: "If you can't tie a knot, then tie a lot." Based on the tactic some climbing newcomers use, of tying tons of knots all over the place because they aren't confident that any one knot will hold. This tactic is strongly frowned upon - you should learn the right knot, use it, and don't add any extraneous ones.

Somebody on twitter posted an image with the two strings in different colours, which helps to visualize the knots:
https://twitter.com/hollowgrin/status/1625902852387352576
[[User:Rps|Rps]] ([[User talk:Rps|talk]]) 17:08, 15 February 2023 (UTC)

Damn, I traced it myself and I am pretty sure the picture on twitter is better (I will not look, I will only get depressed...) I'd put that coloured picture under "transcript" ;-)[[Special:Contributions/172.68.51.140|172.68.51.140]] 18:05, 15 February 2023 (UTC)

I don't suppose any of you knot-loreheads would care to add an explanation/link to explain "Connecting them with a hitch" from the title text? [[Special:Contributions/172.70.254.231|172.70.254.231]] 21:58, 15 February 2023 (UTC)

A "bend" is a knot that connects two ropes or lines. A "hitch" is a knot that connects a rope (a.k.a. line) to something like a post, loop, or shackle.

Is there a mistake in the title text then, since he says to use a random hitch to connect something from the top (presumably rope in the form of a knot) to something in the bottom (presumably more rope)? [[Special:Contributions/172.70.82.186|172.70.82.186]] 22:06, 15 February 2023 (UTC)

I tied it in real life. Once everything was tightened, the main taut portion was the Carrick bend with the other four knots slacking below, and it held pretty well. I imagine if the slack was on the other side, putting stress on the granny knot, it would be a different story. I would upload the picture but I messed up the reef knot and that pulled straight out. --[[User:Jacky720|Jack]] ([[User talk:Jacky720|t]]|[[Special:Contributions/Jacky720|c]]) 22:15, 15 February 2023 (UTC)

Sailor here. The "granny knot" is what a sailor would call a "thief's knot", and it used to be used in place of a reef knot, in some parts of the world, when stores were suspected to be going missing; the thief, after taking some of the stores, would re-lash the remainder using a proper reef knot (through force of habit) and the change of knot would give away that the stores are being taken from that pile.

Additionally, the two bends at the sides look more like sheet bends than bowlines, to me. It just looks like a rope is passed through a bite and then holds the bite together with a half-hitch. (Maybe I just can't get my head around the orientation, though?)

Lastly - is it maybe worth adding that the reason for the figure-of-eights at the tail of the rope is to act as a "stopper" knot, to prevent the tail working it's way back through the half-hitch, which would enable the bite to come apart and the whole thing to come loose? [[Special:Contributions/172.70.86.147|172.70.86.147]] 10:01, 16 February 2023 (UTC)
:A note that a Granny knot is ''not'' the Thief knot. A Granny is (often!) a mis-tied Reef, half re-handed to create a less flat version of the binding, whilst a Thief is a variation of the Reef, which has the opposite track to one of the cords to look the same at first glance (enough to catch the unwary/rushed, as you say, who might then fail to restore it as originally left).
:In fact, a knot that has been given the variations of both '''Gr'''anny and Th'''ief''' is called a "Grief", rather than be back to the original Reef (or a functionally identical reflection/rotation). [[Special:Contributions/172.71.178.64|172.71.178.64]] 12:26, 16 February 2023 (UTC)

Both bowlines are the "correctly" tied sailor's bowline. There is an alternative "left-handed" version in which the end goes the other direction, coming out to the side rather than the interior of the knot. Also called the cowboy bowline, ABOK 1034.5 It is unclear which version is better. One could probably do a PhD dissertation on bowline knots. [[Special:Contributions/172.71.30.97|172.71.30.97]] 14:35, 16 February 2023 (UTC)

Scoutmaster here. I recommend the "Animated Knots by Grog" website as a knot reference. The Wikipedia entries on granny and grief knots are surprisingly useful references for how those knots differ from each other and the reef knot.<br />
The knot on top is definitely a <s>granny knot and not a grief knot.</s> I was wrong. :P Since the ends that terminate the knot exit on opposite sides instead of the same side, calling it a grief knot is not wrong.<br />
Left and right knots are bowlines because they have three working ends and one dead end. The sheet bend has two live ends and two dead ends. The center knot is indeterminate; if you cover up the ends it could be either a sheet bend or a bowline, as they have the same form. Since it appears to have four live ends it would be fair to call it "neither" as well. PhD thesis topic, indeed.<br />
I'd also like to point out that the capsizing nature of the reef knot is considered a feature - it affords easy untying even after being used under heavy load, such as holding a rolled up sail hanging from a yard arm. Being able to unfurl the sail by pulling a single rope is useful. As already noted on the page: if you don't want that feature, pick a different knot. [[Special:Contributions/172.71.146.36|172.71.146.36]] 14:56, 16 February 2023 (UTC)
:You can't really tell a difference between Granny and Grief (and Reef and Thief) in the above as there's not really a 'loose end' from any of those. Following all cords, the visible ends ending with the stoppers ''or'' the off-screen ends (possibly coming back on-screen from the other side, in a large loop, but we can't know that) always goes through multiple other knotted segments. Although I'd say Granny (and Reef) as default is certainly the simplest interpretation.
:And an uncollapsed Reef tends to jam itself, to not simply undo. You need to force it (or rely upon it rotating, through (improper?) use) to make it into a "cow hitch around a straight rope" form and thus an easier untie. Which you can only do if you have sufficient slack on one 'end'.
:(Not sure you could guarantee it capsizing, deliberately or incidentaly, in the omniknot situation once the whole mass gets strained. And there's no way ''that'' Reef segment can undo itsef, without plenty of other knot-failures happening, even if it does re-wrap...) [[Special:Contributions/172.70.91.100|172.70.91.100]] 18:36, 16 February 2023 (UTC)
::Yes, forcing a reef knot to capsize requires abusing the knot; i.e. applying a load onto one of the formerly loose ends. It takes less force than you may think. Try it sometime! I have occasion for this most often with kids' shoestrings.[[Special:Contributions/172.71.147.59|172.71.147.59]] 03:37, 18 February 2023 (UTC)

According to at least one interpretation I've heard, the origin of the Gordian knot story is the use of a complex knot as a sort of tamper evident seal. It won't stop a determined intruder, but it will let the the owner know someone has violated the seal (because the rope is either loose or tied back differently), and let the would-be violator know that the violation they might be considering won't go unnoticed. [[Special:Contributions/172.71.30.143|172.71.30.143]] 16:27, 16 February 2023 (UTC)

"it is knot recommended to use overly complex knots ..." -- is this meant as a joke? the wrong not is used before recommended

Talk:2736: Only Serifs

2023-02-11T16:30:52Z

172.71.147.59: seul serif

first two letters are "A" and "R" I think [[Special:Contributions/172.71.167.10|172.71.167.10]] 04:35, 11 February 2023 (UTC)Bumpf

It's AaBbCcDd. Most likely in Caslon, based on the uppercase A. [[Special:Contributions/172.68.174.149|172.68.174.149]] 04:54, 11 February 2023 (UTC)

So much for a hidden message. [[Special:Contributions/172.68.238.22|172.68.238.22]] 05:05, 11 February 2023 (UTC)

If we've come to this page for an explanation, we probably don't know what a "solum-serif font" is. update the transcript with something more widely known? [[Special:Contributions/172.69.65.224|172.69.65.224]] 05:42, 11 February 2023 (UTC)
:Agreed, enthusiastically! Someone trying to show off, Google doesn't even know what it means, it found ONE result, which is a font of curved corners someone made (when I put "solum-serif" in quotes, to not allow Google to just search one or the other). But while I was Googling someone fixed it before I could, LOL! Which is weird as it's past midnight here in the Eastern time zone. :) [[User:NiceGuy1|NiceGuy1]] ([[User talk:NiceGuy1|talk]]) 05:56, 11 February 2023 (UTC)
:: Perhaps you haven't realised that nighttime for Americans is daytime for, um, somewhere around 80-90% of the world's population? [[User:Paddles|Paddles]] ([[User talk:Paddles|talk]]) 14:54, 11 February 2023 (UTC)

There was a whole thing on Wikipedia about formatting the f symbol for an arbitrary function. One camp held that f is just f, it always is and always was and if you italicize f in a san-serif font, you get an oblique ''f'' but if you italicize f in a serif font, you get a proper italic version, which I'm not sure how to display here. The italic f resembles ƒ, a character called the "hooked f," which is technically an oblique f with a descender ("hook"). That symbol has been used for florins, but sometimes it is also used to imitate the italic f to represent functions, because it has the descender in all environments. But Wikipedia uses a san-serif script, while most mathematical literature uses a serif script. However, it renders expressions in LaTeX with serif fonts and therefore these equations get an f with a descender. So some people were arguing that given this environment, the ƒ character was practically superior, even if it was conceptually wrong, because it most closely resembled the formatted LaTeX expressions. And on and on with the back and forth. I'm glad they eventually settled on just using f for f, like they use g for g and h for h, but still, it was amusingly nitpicky. [[Special:Contributions/172.70.100.50|172.70.100.50]] 07:58, 11 February 2023 (UTC)
:What you listed as resembling italic f looks on my system like ⨍. There are lots of fun variations (some unrelated, just similar looking): ∫⨎ʄ∮∬∰⨏ƒʆᶘᔑ [[User:Fabian42|Fabian42]] ([[User talk:Fabian42|talk]]) 08:48, 11 February 2023 (UTC)

The title text teases the idea of a font made by adding the Times New Roman serifs to Comic Sans, and now I actually want to see such a cursed font. [[Special:Contributions/108.162.241.237|108.162.241.237]] 11:03, 11 February 2023 (UTC)

I think Caslon is correct:
[https://ibb.co/J2WhP1g Caslon] [https://ibb.co/MG77JMX Overlay] [https://ibb.co/3yQtqbN Low Opacity Overlay]
via [http://www.identifont.com/identify?58+.+5J+1JU+3YB+3RZ+35YX+94+JIA+58C+97+22X+8R8+1JY+2Z3A+6ZR+3Q+5BU+9J+1L0+76P+8Z+1QN+7UF+DG+5QE+J+JPK+8C+99+PAE+2AA6+2ZI+8X+8W+8J+1KS+JI6+2Z36+79+8E+53K+2E+1KI+8N+7VS+7S+2C6+1U6+8A+8R0+8F+3WO+2ZGL+1LA+7G+1QY+8B+A0 questions] in Identifont. If someone can add these to the wiki, please do. [[User:DragonDave|DragonDave]] ([[User talk:DragonDave|talk]]) 12:55 11 February 2023 (UTC)

I wonder if this is related to the US State Department dropping Times Roman in favor of Calibri, under the argument that the latter is easier to read. --[[Special:Contributions/172.70.114.198|172.70.114.198]] 13:47, 11 February 2023 (UTC)

I call these fonts seul serif, keeping with the theme of using French terminology. [[Special:Contributions/172.71.147.59|172.71.147.59]] 16:30, 11 February 2023 (UTC)