explain xkcd - User contributions [en]

2812: Solar Panel Placement

2023-08-08T02:01:40Z

Noahhallows: /* Explanation */

{{comic
| number = 2812
| date = August 7, 2023
| title = Solar Panel Placement
| image = solar_panel_placement_2x.png
| imagesize = 506x364px
| noexpand = true
| titletext = Getting the utility people to run transmission lines to Earth is expensive, but it will pay for itself in no time.
}}

==Explanation==
{{incomplete|Created by an underpaid solar panel installer - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This comic proposes a solution to the issue of solar panels not generating enough power due. Solar panels on Earth have multiple things reducing their efficacy such as their distance from the sun reducing the intensity of light hitting them and the fact that for half of the time they can't generate any power because the Earth is blocking the sun. Putting your solar panels in a close orbit above the sun would eliminate most if not all these issues and science fiction authors have suggested this in the form of Dyson Sphere. However putting solar panels in this position introduces many new problems that can negativity impact their energy generating capacity such as transmission losses and the sun.

{{w|Solar panels|Solar panels}} are a relatively common method of powering large objects on Earth, such as homes, businesses, and generators. They work by gathering solar energy reaching the Earth from the sun and converting it to electricity. More specifically, they absorb vast amounts of photons from the solar rays and use them to knock electrons free. Those electrons produce the electric current which is used for powering Earth devices.

Solar panels are notoriously inefficient[https://www.energy.gov/eere/solar/solar-performance-and-efficiency] and often cost more than they are worth to install and maintain, not to mention the extreme challenges of disposing of them when they break. [https://cen.acs.org/environment/recycling/Solar-panels-face-recycling-challenge-photovoltaic-waste/100/i18] This is demonstrated in the comic, where a solar panel of 1m^2 is estimated to return around $58/year, and estimates only a 20% efficiency of converting sunlight to electricity. Considering the potential cost of $10,000 - $30,000 to install, it becomes clear why this might not be the best option.

To solve this, Randall here proposes a rather more straightforward solution: place the solar panels ''downwards'', towards the sun, rather than ''upwards'', from the gravity of the Earth. This would allow for substantially more light to get through and would thus produce massive amounts of energy for the owner.

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

{{comic discussion}}

1144: Tags

2022-10-02T23:12:51Z

Noahhallows: Thsi explanation is long so I wanted to comment about that some web devs were anoyed enough to write this/* Explanation */

{{comic
| number = 1144
| date = December 7, 2012
| title = Tags
| image = tags.png
| titletext = <A>: Like </a>this.&nbsp;
}}

==Explanation==
First of all this comic clearly annoyed enough web developers to get them to write this long explanation about this comic.

{{w|HTML}} is a markup language used in web development, and is the subject of this comic. The comic employs multiple poor HTML practices while asking the rhetorical question of how best to annoy web developers, effectively answering the question that it poses.

In HTML, all elements (except self-closing elements like <code><img></code>) should consist of an open and close tag of the same type <code><div>Like this</div></code>.

HTML (except in its formulation as an XML language—XHTML) has never been case-sensitive, but the practice of using uppercase tags for readability is long outmoded, and the mixing of cases in this example would definitely annoy a developer.

Another basic idea of HTML is that all elements should be properly nested. That is, any element whose open tag occurs inside a div must be closed before the div is closed.

NB: In practice, web browsers will error-correct nearly all these problems.

{| class="wikitable" |
! Correct
! Incorrect
|-
|
<div>
<ol>
<li>Correctly nested</li>
</ol>
</div>
|
<div>
<ol>
<li>Incorrectly nested</li>
</div>
</ol>
|-
|}
The rules of proper nesting also put restrictions on which tags can be placed where — "block" elements, such as <code><div></code> cannot be placed inside "inline" elements, such as <code><span></code>, and inline elements must be placed inside a block element of some kind. Thus, <code><span><div></code> is forbidden, even if the tags are closed in the proper order.

Further, web developers make a distinction between ''semantic'' and ''structural'' elements. Semantic elements contain a clue in their name as to what kind of an element they are — for example, an <code><article></code> tag contains an article, such as a blog post or news article, while an <code><ol></code> tag contains an '''o'''rdered '''l'''ist. (It's wise to note that this is not an absolute rule; it's ''possible'' to put non-article content in an <code><article></code>, it's just not recommended.) Semantic tags do not, however, indicate how their contents are to be displayed; your browser might display an <code><article></code> in the default font, layout, and placement, while mine, a {{w|screen reader}}, might ignore everything on the page except <code><article></code>s, and read <code><article></code>s in a [[462|soothing voice]].

Structural tags, on the other hand, give no clues as to what they contain; they just indicate how a web page is to be laid out. <code><span></code> and <code><div></code> are structural tags; they can contain anything. Their definitions in HTML simply indicate that <code><div></code> is a block tag (it can affect both what the text looks like and where it is on the page; by default, it is displayed in a separate block from the rest of the text in the page, and has at least one line break before and after its display) and <code><span></code> is an inline tag: it affects what its text looks like, but not where it is on the page. Without additional attributes, it's impossible for a browser to tell what's supposed to be inside a <code><div></code> or a <code><span></code>, which means that my screen reader can't just pluck out the blog posts and read those.

Currently, the standard of usage is shifting toward using semantic tags over structural tags, since they provide more information to browsers and people reading the source code of web pages. HTML5, the most recent version of the standard web development markup language, is introducing many semantically meaningful tags that can be styled using {{w|Cascading Style Sheets|CSS}} to follow the same behavior as a div or span, but that are easier to understand when reading the markup or parsing it with a non-standard browser. For example, <span style="background: #eeeeee;">this is in a span</span> and <div style="background: #eeeeee;">this is in a div.</div>

The title text makes reference to <code>&nbsp;</code>, which is the {{w|HTML#Character and entity references|HTML escape code}} for {{w|non-breaking space}} which is a type of space that will keep two words together, and will not allow word wrapping to separate them. If the words come at the end of a displayed line, how this is handled depends on the browser and on the element's styling; some browsers and styles will force the connected words onto a new line, while others will "overflow" the edge of the container to accommodate the linked words. This is useful, for example, for keeping units with a number so it is easy to spot 100 km instead of needing to hunt for 100<br/>km. Using a non-breaking space at the end of a line, without another word on its trailing end, is only useful in extremely rare and limited circumstances, and does not generally have a purpose.

The title text also uses an <code><A></code> tag, seemingly to indicate an answer. In fact, <code><A></code> is an anchor tag, which creates {{w|hyperlink}}s. It is not an answer tag. This tag is generally used with either the <code>href=</code> (which creates a link to another URL) or <code>name=</code> (which creates a named anchor on the page that can be linked to with <code>href=#</code>) attribute (but not generally both at once). In addition, the placement of <code><A></code> and <code></a></code> (the capitalization here is also irritating to a web developer who values consistency) indicates that ": Like " should be a link or named anchor, but "this." should not. Whether or not to include punctuation in an anchor is a matter of some debate among developers, but including excessive whitespace is generally frowned upon, and the anchor ''should'' include all of the relevant text.

==Transcript==
:<code><div>Q: How do you annoy a web developer?</span></code>

{{comic discussion}}

2203: Prescience

2022-08-29T23:37:06Z

Noahhallows: /* Explanation */ Psychohistory was not mentioned.

{{comic
| number = 2203
| date = September 16, 2019
| title = Prescience
| image = prescience.png
| titletext = Lots of people called their ships unsinkable before the Titanic. Voicing your hubris doesn't make failure more likely, just more memorable.
}}

==Explanation==

In this comic, [[Cueball]] states that it's been a long time since there's been a really big {{w|Impact event|meteor impact}}. Due to the {{w|Gambler's Fallacy}}, this is taken to be Cueball implying that a big meteor impact is coming soon. The off-panel voice is annoyed about his statement, but whether from fear of it happening or because he does this all the time is unclear, see more below. The joke is that Cueball does this often, also with other types of major random events, just in case they do actually happen soon. For instance, if there does happen to be an impact soon after he made the statement, it makes him look incredibly {{w|prescient}}, whereas if there isn't one, no one really cares or remembers.

It is also unclear how big an impact he refers to. It has been 60 million years since the {{w|Cretaceous–Paleogene extinction event|impact that killed the dinosaurs}}, but that if that is the type of event he refers to, then maybe no one will be there to remember what he said. So it is likely much smaller impacts he is talking about.

''Prescience'' means to predict the future. It is clear from this comic that [[Randall]] makes fun of both of those that claim to have prescience and of those that have a superstition against talking about something happening that could cause it to happen.

Although only one method is scientifically recognized, there are at least three possible sources of prescience recognized by people.

The first of the two main ways of predicting the future involves a mix of common sense and historical knowledge. By understanding the past, the direction of the future can be guessed at with varying levels of accuracy. This type of prescience is also known sometimes as future modeling, statistical prediction, psychohistory, and even wisdom to name a few.

The second way to predict the future is not scientifically recognized but remains popular in culture and fiction. It can involve magic, psychic power, higher powers (gods), and other such methods. Collectively, they are labeled supernatural; any method to predict the future using this class of method cannot be easily measured by science.

Although not technically a way to predict the future, the third way to predict the future is through superstition. The method involved in this comic effectively boils down to "speak the name of evil, and you will summon it." This superstition can have surprising power in people's lives, however. A woman planning her outdoor wedding may feel the urge to hit her friend if they say "Gosh, I hope it doesn't rain on that day." A doctor working in the Emergency Room may feel the need to kick anyone who says "Wow, it's really quiet around here." Such thoughts spoken aloud do not have the power to control the weather or cause people to seriously injure themselves. Yet people often react emotionally as if not speaking the name of 'evil' will keep it away.

This comic may reflect that emotional reaction when the off-screen character yells at Cueball: "Will you stop that?!". Alternatively, it is one, like [[Megan]], who knows Cueball well enough to know that which is stated in the caption, that he only does this to look good if said thing happens. And the person is so tired of it! Maybe Cueball does it at least once a week, and obviously from the caption, it is not only about meteor impact, but any major random event, that he could then be remembered as having predicted.

The title, Prescience, has a double meaning. The first meaning is about the prescience that would appear if one actually predicts a natural disaster this way. The second meaning involves the fact that it is spelled pre-science - since there are many more scientific ways to predict meteor impacts, even though they aren't entirely accurate.

The title text refers to the {{w|RMS Titanic|RMS ''Titanic''}}, a ship which was claimed to be unsinkable by those promoting its maiden voyage. But then it struck an iceberg in an unfortunate way so more compartments would be filled with water that it could survive; and, therefore, it could and eventually ''would'' sink. But with all the news stories that had just been published hailing this unsinkable ship as a modern wonder of the world, this shipwreck was particularly ironic. The story of the sinking of the ''Titanic'' has been memorialized in popular culture, most memorably in the 1997 film {{w|Titanic (1997 film)|Titanic}}.

In the title text, Randall thus suggests that lots of ships had been called unsinkable before Titanic. But saying such {{w|hubris}} out loud doesn't make any ship more likely to sink. But when such a ship, like Titanic, then sinks it does, however, increase the value of the story ensuring it will be remembered.

It should be noted that few among the ship's builders or crew boasted the ''Titanic'' to be unsinkable. Most of the boasting came from the owners that used the news media of the day to create hype and promote their ship, just when the ship was finished and dedicated (the ship's builders did, however, boast that the ship exceeded all safety standards of the time). In addition, the hubris was only one small part of the fame of the sinking of the ''Titanic''; the ''Titanic'''s status as a world record setter for most massive ship ever built, the incredible wealth of most of its passengers, and the fact it sank on its maiden voyage all contributed to the fame and hype behind the great maritime tragedy.

Ironically part of what caused this disaster was hubris, since those that were interested in promoting the ship also wished it to make a speed record, by reaching New York a day before expected. Thus the captain, even though he would have realised that the ship could sink, took the fateful decisions of running at full speed through waters known to contain icebergs during a still night with very calm waters. Spotting icebergs in such conditions is known to be difficult, especially as there will be no notably foaming waves around the icebergs' bases and patchy mists will inconveniently diffuse the horizons and any useful starlight.

==Transcript==
:[Cueball is sitting in an armchair holding a book. He seems to be looking off as he talks to an off-panel person behind him. This person replies.]
:Cueball: You know, it's been a while since there's been a really big meteor impact.
:Off-panel voice: '''''Will you stop that?!'''''

:[Caption below the panel:]
:I say this kind of thing every so often, because I don't believe it affects the outcome and it has a slim chance of looking ''incredibly'' prescient.

==Trivia==
*This comic has a clear resemblance to the [[:Category:My Hobby|My Hobby]] series. This would also make it clear the Cueball in this comic is actually [[Randall]].
*The entire setup and punch line of this comic is very similar to this old comic: [[525: I Know You're Listening]].
*Also [[628: Psychic]] and [[858: Milk]] use the idea of guessing something that will make you look special.

{{comic discussion}}

[[Category:Comics featuring Cueball]]

735: Floor

2022-07-14T23:38:21Z

Noahhallows: /* Explanation */

{{comic
| number = 735
| date = May 3, 2010
| title = Floor
| image = floor.png
| titletext = We once got grounded when we convinced the FAA to block flights through our county because of ash clouds.
}}

==Explanation==
{{w|Hot lava (game)|The floor is lava}} is a game many kids play where they pretend the floor is {{w|lava}}, meaning that they can't step on it or else they'll get 'burned'. In this comic, the three kids are taking this game too seriously, causing great damage to the house with what appears to be a garden hose and some dynamite.

Stopping a lava flow by diverting it into an artificial trench or cooling the flow with (sea)water are both tactics that have been used in the past [http://hvo.wr.usgs.gov/volcanowatch/archive/2007/07_12_06.html with varying success].

The title text refers to events like the 2010 eruptions at {{w|Eyjafjallajökull}}, the ash clouds of which caused the shutdown of most of Europe's {{w|IFR}} airspace. The first joke there is that grounding a child often means to consign him/her to his/her bedroom for a set period of hours (as a punishment), whereas grounding a plane means to disallow any use of that plane for an extended period of time. The most notable example of this is {{w|Concorde}}, which has been indefinitely grounded. The second joke is that causing panic and diverting a large number of flights would cause lots of financial damage, and would normally be subject to more punishment than simply giving the kids a time-out.

==Transcript==
:[Three Cueball-like kids are in a living room. Furniture and other things are knocked over, broken, or tilted. The first kid is holding a handle of a plunger with cables going offscreen.]
:First Kid: I've dynamited a trench through the kitchen to divert flow!
:'''BOOM'''

:[The second kid is aiming a hose at the floor.]
:Second Kid: More hoses! We need to cool and solidify the surface layer!
:''FWOOSH''

:[The third kid is standing on a chair, using a cell phone or radio.]
:Third Kid: Where are the damn helicopters?

:[Caption beneath the panel:]
:Like many kids, we sometimes pretended the floor was lava.

{{comic discussion}}

[[Category:Volcanoes]]