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Steuard

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Understanding Motion and Relativity with Spacetime Diagrams

steuard.github.io
7 points·by Steuard·10 miesięcy temu·1 comments

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Steuard
·14 dni temu·discuss
I can't say what the reality looks like today, but when I was in college 25 years ago (Harvey Mudd), closed-book take-home exams were pretty common (often with a specific time limit: maybe 3/5/8 hours), and I would have been shocked and aghast at the thought of anyone cheating. We took our Honor Code deeply seriously. (I've given my own students take-home open-book exams with "no outside resources" rules regularly in the past, but I've pretty much concluded that isn't viable anymore. But then, we don't have a formal Honor Code here.)

One particularly striking example was a timed, closed-book math exam where the exam paper just listed four problem numbers from the book. We were expected to open the book, copy down those problems without looking at anything else, and then put the book away. Honestly, that one felt like just asking for trouble and now that I'm a professor myself I think that the prof was unreasonably lazy, but it certainly captured the spirit of the thing. (Technically, that wasn't a Harvey Mudd professor but rather a professor at the adjacent graduate university. Maybe that had something to do with it.)
Steuard
·21 dni temu·discuss
Do you by chance have references to those conceptually cleaner bivector publications? I've spent a good bit of time looking for other people working in that space, and haven't found much other than an article by Jancewicz from 1980. (I like to imagine that my articles these past few years have been "conceptually clean", but they certainly aren't "previous" to much GA work.)
Steuard
·2 miesiące temu·discuss
[Possible obscure spoiler]

A friend once showed me a post on rec.games.roguelike.nethack where someone was finally begging for a hint because they'd gone deep in the dungeon and couldn't figure out anything to do next. They couldn't find any staircases down, though they had found a weird vibrating square, and none of the many weird items they'd collected seemed to do anything to help.
Steuard
·4 miesiące temu·discuss
If you come up with a process to do that efficiently, the helium will be a lovely bonus but not remotely the most important result. :D
Steuard
·4 miesiące temu·discuss
In principle, flagrant abuse of the pardon power is blocked by Congress's ability to impeach and remove a President who engages in such abuse.

In practice, that has always been an ineffective threat against Presidents who are within days of leaving office anyway. And more importantly, the framers of the Constitution seemed to have entirely failed to imagine a party like today's Republicans who value strict personal loyalty to the President over every other principle of government.
Steuard
·5 miesięcy temu·discuss
All I have to say is that if one of my students turned in those curves as "best fits" to that data, I'd hand the paper back for a re-do. Those are garbage fits. To my eye, none of the very noisy data sets shown in the graph show clear enough trends to support one model over any other: are any of those hyperbolic curves convincingly better than even a linear fit? (No.) The "copilot code share" data can't possibly be described by a hyperbolic curve, because by definition it can't ever go over 100%. (A sigmoidal model might be plausible.) And even if you want to insist on a model that diverges at finite time, why fit 1/(t0-t) rather than 1/(t0-t)^2, or tan(t-t0), or anything else?

The author does in fact note that only the arXiv data fits this curve better than a line, and yeah: that's the one dataset that genuinely looks a little curved. But 1) it's a very noisy sort of curved, and 2) I'll bet it would fit a quadratic or an exponential or, heck, a sine function just as well. Introducing their process of doing the hyperbolic fit, they say, "The procedure is straightforward, which should concern you." And yeah, it does concern me: why does the author think that their standard-but-oversimplified attempt to fit a hand-chosen function to this mess is worth talking about? (And why put all of that analysis in the article, complete with fancy animated graph, when they knew that even their most determined attempt to find a signal failed to produce even a marginally supportive result 80% of the time?)

In short: none of the mathematical arguments used here to lead in to the article's discussion of "The Singularity" are worth listening to at all. They're pseudo-technical window dressing, meant to lend an undeserved air of rigor to whatever follows. So why should we pay attention to any of it?
Steuard
·6 miesięcy temu·discuss
How old are you? Because I promise you, that description was pretty much spot-on for most shows through most of the history of TV prior to the late 1990s. My memory is that the main exception was daytime soap operas, which did expect viewers to watch pretty much daily. (I recall a conversation explaining Babylon 5's ongoing plot arc to my parents, and one of them said, "You mean, sort of like a soap opera?") Those "Previously on ___" intro segments were quite rare (and usually a sign that you were in the middle of some Very Special 2-part story, as described in the previous comment).

Go back and watch any two episodes (maybe not the season finale) from the same season of Star Trek TOS or TNG, or Cheers, or MASH, or Friends, or any other prime time show at all prior to 1990. You won't be able to tell which came first, certainly not in any obvious way. (Networks didn't really even have the concept of specific episode orders in that era. Again looking back to Babylon 5 which was a pioneer in the "ongoing plot arc" space, the network deliberately shuffled around the order of a number of first-season episodes because they wanted to put stronger stories earlier to hook viewers, even though doing so left some character development a bit nonsensical. You can find websites today where fans debate whether it's best to watch the show in release order or production order or something else.)

By and large, we all just understood that "nothing ever happens" with long-term impact on a show, except maybe from season to season. (I think I even remember the standard "end of episode reset" being referenced in a comedy show as a breaking-the-fourth-wall joke.) Yes, you'd get character development in a particular episode, but it was more about the audience understanding the character better than about immediate, noticeable changes to their life and behavior. At best, the character beats from one season would add up to a meaningful change in the next season. At least that's my memory of how it tended to go. Maybe there were exceptions! But this really was the norm.
Steuard
·9 miesięcy temu·discuss
The article feels like LLM output, too. (And they don't actually credit an author in the byline.) Is there another source out there that this was based on? Can we read that instead, and skip the extra layer of interpretation/distortion?
Steuard
·10 miesięcy temu·discuss
I'm a physics professor who regularly teaches about special relativity in my Modern Physics course. I've made a web app for drawing spacetime diagrams (technically, two-observer Minkowski diagrams), which are one of the best ways I know for building intuition about how relativity works. The link points to an introduction to the diagrams, including a brief explanation of some key relativity concepts based on diagram illustrations. (It's meant to be at least halfway understandable to people who haven't studied physics before, though it'll be clearer the more you already know.)

Read through the linked page if you want the basics, or if you're eager to just jump straight in, follow the links to use the main app and play with that. (It has multiple predefined scenarios that you can load, each with a brief explanation, but you can design your own scenarios as well.)

[Aside: I feel really good about the UI I've got for this so far, but my last significant JavaScript work before this project was back in 2005 or so. I've had to learn a LOT.]
Steuard
·11 lat temu·discuss
A friend of mine created the board game Robot Turtles ("programming for preschoolers"), which has a bit of that goal. It's a parent-child(ren) thing rather than a solo activity, mind you.

http://www.robotturtles.com/