331 karma · joined November 4, 2021
I also like trying to figure out where the photo was taken, even if that isn't strictly part of the game. So I'm glad that the photo caption is there.
Edit: I had seen the photo in the subway before, or something very similar. It's an interesting decision to use photos from big events that people might recognize. (Not inherently bad IMO, just not what I would have intuitively chosen)
We also have both streetcars and trolleybuses, and some strange junctions like the one at 5th and Jackson: https://maps.app.goo.gl/4TuLXmRLY5yK6HGJ6
There are some nice blog posts from a Seattle bus driver that go over some of the nerdy details of our system: https://www.nathanvass.com/blog/i-dont-know-what-a-trolley-i... https://www.nathanvass.com/blog/i-dont-know-what-a-trolley-i...
The word "digital" is doing a lot of work here: here in the US, the Pennsylvania Railroad had in-cab signaling back in the 20s. Here's an article about it [pdf] https://www.jonroma.net/media/signaling/railway-signaling/19...
With the recent mandate of Positive Train Control on all mainline trains in the US, some steam locomotives have been retrofitted with PTC, notably UP 4014 and CPKC 2816 (which seems to the be basically the US version of what the brits are doing here).
But regardless of pedantry, it's neat to see the reassurance that they'll be able to operate on modern mainlines safely.
https://fridgepoem.com/#x=-4636&y=-8233
I don't have a lot to add to the conversation, except that this is a neat project, and pulls off the exact feeling of fridge poems very well. I guess everyone gets the same fridge, like the old /r/place experiment on reddit?
In lesson 9, you say "The CEO of the Perplexity.ai search platform argues that AI has made blue links obsolete.
"But without sources you are driving blind."
Isn't the entire point of perplexity that it gives you the sources?
No, I know what you mean. There's a balance between using the right lingo to communicate clearly with subject matter experts (SMEs if you will) and communicating clearly with those who only have a passing interest. A buddy of mine from college had a 2JZ FC RX7, but he could have also just said it was a japanese sportscar with an engine swap. Depends on the target audience. I guess on the internet, you're often talking with both kinds of people which makes it tricky.
The "something about the geometry" is called caster, and is the same effect that makes the front casters on a shopping cart go straight: the point where the steering axis intersects the ground is ahead of the contact patch of the tire. On a bike, this is mostly determined by the angle of your head tube when looking at the bike from the side (if the fork is "bent" from the side view, this would also contribute to the caster effect).
But I've now googled, and found a paper that says that a bike can be stable without gyroscopic or caster effects [1]. It seems like the specific mass distribution of the steerable mass (front wheel, fork, handlebars, etc) vs the rest of the frame matters, and of course all of these variables interact in complex ways. They do agree that caster plays an important role though.
Vehicle dynamics is notoriously tricky stuff. I can say with experience that it doesn't get easier when you go to four wheels.
[1]: https://www.researchgate.net/publication/51051995_A_Bicycle_...