Submitted 2 days ago by xkcdbot@lemmy.world [bot] to xkcd@lemmy.world
https://imgs.xkcd.com/comics/sail_physics.png
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: xkcd.com/3090/
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.
Well that doesn’t look right but I’m not a boat physicist so I’ll just accept it at face value.
dammit the bot was faster than even the explainxkcd page creation bot, not to even speak of mastodon.xyz/@xkcd :o
wait what
is this true? why is it weird?
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
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.
simple as
Explain like I’m Calvin.
Explain like you’re Calvin
who@feddit.org 2 days ago
Any chance of getting the bot to use the source page as the post link, rather than burying it within the body? That would make it easier to view the whole comic, complete with hover text.
Deebster@infosec.pub 3 minutes ago
Bot author here - I thought that the current implementation was a big improvement because it meant you didn’t have to load up an external website but I should have known that not everyone would be happy!
Looking at the votes for the comments for and against this idea, it looks like if it went to a vote the current setup would win, but I’ll think about how it can be improved.
AlDente@sh.itjust.works 2 days ago
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 2 days ago
The thing is, with xkcd, the image alone is not the full comic. Part of the comic is the hover text, which you don’t get with the image alone.
AlDente@sh.itjust.works 2 days 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.