this post was submitted on 16 May 2025
193 points (98.5% liked)

xkcd

10883 readers
39 users here now

A community for a webcomic of romance, sarcasm, math, and language.

founded 2 years ago
MODERATORS
 

Title text:

Turning in other directions can be accomplished by using a magnetized centerboard and ocean currents, since a current flowing through a magnetic field induces a Laplace force.

Transcript:

Transcript will show once it’s been added to explainxkcd.com

Source: https://xkcd.com/3090/

explainxkcd for #3090

all 26 comments
sorted by: hot top controversial new old
[–] isaaclyman@lemmy.world 7 points 22 hours ago

Yes, it’s possible (and common) for a boat to sail against the wind by the power of its sail alone. Sailors have known this for hundreds of years but if it sounds impossible, no worries, I thought so too at first.

Here’s how it works, simplified so I can get in trouble with pedants:

The boat, first of all, has a keel (the blade-like bottom of the hull) which “locks” it into movement along a single axis: forward and backward. The wind is not going to blow the boat sideways, at least not very effectively.

Second, sails are curved, not flat, and can rotate (when seen from above). The force created when the wind deflects off the sail matches the curve of the sail, more or less.

So if the wind is blowing directly south ⬇️ and you want to travel north ⬆️ you angle the boat northeast ↗️ so it can only move northeast or southwest. Then you point the sail east ➡️ so the wind gets deflected west ↩️. Newton’s third law does the rest. When the wind hits, the boat will move northeast ↗️ because the keel prevents it from going straight east.

Then after a while you turn the boat (“tack”) northwest ↖️, point the sail west ⬅️, and continue.

[–] JasSmith@sh.itjust.works 11 points 1 day ago

Well that doesn’t look right but I’m not a boat physicist so I’ll just accept it at face value.

[–] who@feddit.org 22 points 2 days ago* (last edited 1 day ago) (2 children)

Dear bot maintainer,

Any chance of getting the bot to use the source page as the post link, rather than linking to the image alone and burying source link within the body?

That would make it easier to view the whole comic, complete with hover text, in one place.

Edit: Linking to the mobile site would also work, and perhaps better accommodate both mobile and desktop users. Like this: https://m.xkcd.com/3090/

[–] AlDente@sh.itjust.works 46 points 2 days ago (1 children)

I actually like it better this way because the full comic can be viewed and zoomed in on in app (Voyager in my case). I've seen these posted with the source page as the post link and I can't click on the image to zoom in without being pulled out of app with a wait for the web page to load. Also, when entering the post to see the comments, the thumbnail is so small when the source page is linked, making the comic unreadable. With an image alone, the full comic is viewable beside the comments. Is it different for you?

[–] who@feddit.org 12 points 2 days ago* (last edited 2 days ago) (2 children)

The thing is, with xkcd, the image is not the full comic. Part of the comic is the hover text, which you don't get with the image alone.

The way things are now, I click the title and it takes me to a bare image, so I then have to go back, and then read through the post body to find the link to the whole comic, and then click that. It's a hassle.

(And since you mentioned viewing comments alongside the image, you should be aware that Lemmy's default interface shows only a thumbnail fragment of the image on the same page as the comic. I guess you might be using a mobile app.)

[–] Wxfisch@lemmy.world 19 points 2 days ago (2 children)

The bot adds the alt text to the post, so no need to head to the site to see the entire comic.

[–] aeharding@vger.social 5 points 1 day ago (1 children)

Are you the bot author? If so have you considered using Lemmys alt text field directly? This would display the text with the image is some clients like voyager. It would also federate to Mastodon (post body doesn’t federate). You could also keep the text in the post body and do it both places :)

[–] Wxfisch@lemmy.world 5 points 1 day ago* (last edited 1 day ago)

I am not, that appears to be @deebster@programming.dev

[–] who@feddit.org -1 points 2 days ago* (last edited 2 days ago) (3 children)

That splits the comic between two separate screens, and requires multiple steps (and page loads) to read it.

It's not as good as linking to the whole comic, intact, in one place.

[–] Wxfisch@lemmy.world 12 points 2 days ago

As has been pointed out though on non-web clients it's much more disruptive to link to the webpage instead of how the bot works now. I'm not sure what the split is between web and mobile users but I'd hazard a guess there's appreciably more mobile client users.

I'm also not sure why it would require more loads on web, if you open a post (as you have to do regardless) does it not show the image with text below it anyways?

[–] AlDente@sh.itjust.works 4 points 2 days ago (1 children)

I guess this is going to come down to desktop vs mobile preference. On mobile this shows everything on one page with no additional loading. Alternatively, using the source page requires multiple steps and page loads for mobile users, who may also need to amend the link to see the hover text.

[–] who@feddit.org 0 points 1 day ago* (last edited 1 day ago) (1 children)

I guess this is going to come down to desktop vs mobile preference.

In that case, perhaps linking to the mobile site would make sense, since it ought to work for both mobile and desktop:

https://m.xkcd.com/3090/

[–] arudesalad@sh.itjust.works 3 points 2 days ago (1 children)

If you are on the standard lemmy ui:

  • Click on the post, not the image source
  • Expand the image by clicking on it
  • You can now see the comic and alt text in one place
[–] who@feddit.org 1 points 1 day ago

Still not equivalent, since it still requires multiple steps, and doesn't work with privacy settings that forbid off-site images.

[–] AlDente@sh.itjust.works 4 points 2 days ago* (last edited 2 days ago) (1 children)

Ah, thanks for clarifying. I never knew about the hover text. I just viewed the source page on my desktop browser and now I see it. However, is this text even viewable on mobile, when you don't have a cursor to hover?

E: Now that I've read the hover text on my desktop, I've noticed that it's the same as the text added to the post by the bot. I really like this implementation with the image linked alone. When the post is viewed on mobile, all text is viewable and the full comic is shown legibly.

[–] who@feddit.org 5 points 2 days ago (1 children)

The mobile browsers I've used let you long-press the image to see the hover text.

If yours doesn't, you can always prepend m. to the domain name, like this: https://m.xkcd.com/3090/

[–] AlDente@sh.itjust.works 2 points 2 days ago

Thanks for the tip!

[–] AlDente@sh.itjust.works 2 points 1 day ago

Regarding the edit:

The mobile link might be better than the usual link, but I'd still prefer the one-stop-shop of this current method. Comic, hover text, and comments are all viewable in one place without the additional wait of switching to a browser app and loading the page. I wish the desktop experience mimicked this.

[–] schnurrito@discuss.tchncs.de 16 points 2 days ago

dammit the bot was faster than even the explainxkcd page creation bot, not to even speak of https://mastodon.xyz/@xkcd :o

[–] umbrella@lemmy.ml 6 points 1 day ago (2 children)

wait what

is this true? why is it weird?

[–] Anomalocaris@lemm.ee 3 points 19 hours ago

even if it's true, the effect would likely be unmeasurably tiny. way bellow negligible.

but I'm curious if it is also sort of true.

[–] LSNLDN@slrpnk.net 22 points 1 day ago

Haha no I’m no physicist but they’re using other explanations that are completely inappropriate to come to the same conclusion, it looks like

[–] not_woody_shaw@lemmy.world 3 points 1 day ago (1 children)
[–] otter@lemmy.dbzer0.com 1 points 1 day ago* (last edited 1 day ago)

Explain Like You're Calvin

[–] sbv@sh.itjust.works 5 points 2 days ago