Steuard

I don't mean this unkindly, but I am always so baffled when I see how common this take is. I mean, sure, say this about string theory (the field I was trained in): fine. I don't agree, but I see the point.

But dark matter? You think we wanted this "weird particle or something very like it that we persistently can't find" situation? No! The reason that the overwhelming majority of cosmologists and astrophysicists pretty solidly believe that dark matter exists (after a whole lot of skepticism when it was first proposed) is that there is very strong evidence for it from at least three radically different sets of experimental data. [Patterns in how galaxies rotate (the original), gravitational lensing to locate and quantify mass in galaxy clusters (including cluster collisions like the "Bullet Cluster"), and the overall history of cosmological evolution.] And not only do all three lines of evidence indicate "dark matter exists", but as I understand it, they all independently indicate a consistent amount of dark matter (relative to the observable ordinary matter).

People have tried to come up with modified theories that eliminate the need for dark matter for years and years (once they gave up suggesting the observations themselves might be faulty): it would be so much more satisfying, especially in light of our continued failure to find any sort of "stuff" that the dark matter might be made of. But as I understand it, every modification of basic theory that's so far been proposed to give a different explanation of one of those pieces of evidence has had nothing at all to say about the other two. And while maybe you could come up with a different theory modification to account for each line of evidence separately, at that point the coincidence starts to seem far less plausible even than "particle we can't find". ("Our otherwise solidly established theories are wrong in three very specific but unrelated ways, each tuned to match the effects we'd see from the exact same amount of dark matter.")

And yet somehow, the notion has taken root among a whole bunch of non-experts that this is all somehow a conspiracy or a group delusion or a stubborn self-interested refusal to consider other answers. I'll never pretend that science is perfect or immune to groupthink! But for goodness sake, aim that skepticism in some direction where the observational evidence is less overwhelming. (And before you just pick another field to go after, maybe first think carefully about what factors led you to disagree with the experts on this one where it really, really wasn't justified.)

A friend of mine worked for a while as part of the team building http://unglue.it, which IIRC is a pretty close match to what you're envisioning.

Oh, yikes: when did the + stop working for Apple support? That's going to bite me at some point. (And in general, yeah: I've had multiple cases over the years where the "+" only caused problems after signup. One of several reasons that I eventually stopped using those forms.)

And just to put it out there: "+" addresses aren't specifically a Gmail thing, they've been supported by most(?) mail servers for a very long time.

Ha! Cool! I wasn't the only one!

But honestly, I eventually concluded that with the resolution available on my CGA monitor, the (slightly) higher-resolution black and white version was probably a better choice (and it gave the game a bit of a noir air).

Sometimes it is exactly what they're doing. 15 years ago, shortly after surgery to remove a tumor from my femur, I ran into a physical therapy assistant whom I'd been working with when my doctors thought my leg pain was a soft tissue problem. He said he'd heard about my surgery and was glad I was doing well, and then as we parted ways he cheerfully commented offhand that when I'd been working with him and his supervisor, "I thought you were making it all up!" (I still feel angry about that occasionally, all these years later.)

Are we revealing our age through exploits now? How about "using gopher on a university library terminal to access a site that launched a telnet session so you can check your out-of-state college email over the summer"?

Oh, man, the Lurker's Guide was just such a fantastically good site. Organized, comprehensive, solidly good look: great stuff!

I feel like it's often harder to find high-quality focuses resources like this at this point. I'm not sure whether that's because people have stopped making them, or whether they're just competing for clicks with exponentially more common (and more SEOified) junky fan-wiki sites, or what. (I still get a steady trickle of traffic to my Tolkien Meta-FAQ (http://tolkien.slimy.com/), but I gather that Google tends to de-prioritize sites that aren't being constantly updated.)

This feels very dark to me: I think it would make it enormously harder to actually process the grief. (The thought "You could make one to mimic your ex" passed through my head just long enough for me to recoil in absolute horror.)

This is a very nicely designed site, but I have to grumble a little: bivectors aren't a concept unique to geometric algebra! They've been used elsewhere in physics for ages: well before geometric algebra in its current form was developed. (I first encountered them in the Petrov classification of spacetime structures.) So it's a bit awkward to see "bivector.net" as a label for geometric algebra resources. (And they're not alone: the Wikipedia article on bivectors reads as if geometric algebra is the only context where bivectors are meaningful, too.)

In fact, I've recently written a paper[] about teaching rotational physics using the language of bivectors instead of cross products: deep down, bivectors are the right* language for rotations. (The cross product/pseudovector form is an accident of three dimensions, with awkward transformation properties under reflections or when extended to relativity.) There's absolutely no geometric algebra necessary, though more than one proponent of GA has told me they think this approach could be a nice first step toward teaching that formalism.

[*] I haven't had time to upload the accepted version of the paper yet (with improvements after peer review at AJP), but the original version is here: https://arxiv.org/abs/2207.03560

That sounds like a cool use case, but... how can you bring yourself to trust anything at all that it tells you? This feels like it's just begging to contaminate your understanding with sparse, unpredictable errors, and personally I find the thought of that unexpectedly dismaying.

Wow. Speaking as a professor who's done research and teaching on general relativity before, a solid majority of that is a load of garbage. (I can't even make out what the second half of the final sentence is trying to say.)

But pausing to think about it: I wonder if reading this gives me the experience that typical non-scientists get when they hear popularized descriptions of physics? Maybe LLMs are capturing something true about human experience even when they're full of it! [Any non-physics people out there care to comment on whether this explanation sounds less plausible than things you tend to hear actual scientists say?]

Reading this is really weird for me. Worthwhile and eye-opening, but also baffling: I am literally the chair of the faculty committee at my small college that voted a couple of years ago to go test-optional (provisionally but with an eye toward making it permanent). I won't claim to be an great expert on the issues involved, beyond generally trying to keep up with the broad conversation about research outcomes: we're too small for any of us to specialize enough to get into the weeds of specific studies and methodologies outside of our fields (I'm in physics).

From all I've read in the past, though, standardized test outcomes are very strongly correlated with family wealth. The kids who have great SAT vocabularies are overwhelmingly the kids who grew up with parents with plenty of free time to read to them every day. High scoring kids are overwhelmingly the ones whose families could provide lots of educational support (either through direct help from available parents or through private tutoring). They're so very often the ones who spent weeks of their lives getting dedicated training in the otherwise-useless skill of "how to take a standardized test". And the correlation between SAT score and college success (by whatever metric) is IIRC quite low once you control for family background. So by and large, the faculty members that I know have come to see standardized testing as precisely a tool to give preference to kids from wealthy, privileged backgrounds.

Obviously the author of this article had a very different experience! And clearly there are kids out there who can use standardized tests to demonstrate amazing competence beyond what their grades show. (That's why we went "test optional" rather than "no tests allowed", for what it's worth.) And I'm not at all surprised that admissions essays correlate even more strongly with wealth than do SAT scores. (We don't rely entirely on essays, either.) Maybe we really did get it wrong, and the research we considered really was misleading, and universal testing would raise up more underprivileged students than it threw down. But I promise you, I absolutely 100% promise you, that no person in that room where we made the test-optional decision believed that the outcome of our decision would be fewer students with challenging backgrounds being admitted.

So is the claim here that the college decision makers adopting these policies are also dupes of "the chattering class"? (Aren't we supposedly a part of that class?) Or maybe it's just that I, personally, was the dupe of my faculty colleagues, who were conniving behind my back to get less competent students in their classes? I don't get it.

The only conclusion I can draw, in general, is that it is really hard to disentangle an individual student's intrinsic potential and preparedness from the influence of family wealth and resources. I agree with this author that there really are enormous systemic biases that encourage class segregation, and those biases are viciously wide-ranging and flexible and are embedded across all axes of achievement and opportunity. So I'm not particularly happy about the way that this essay very explicitly assumes bad faith on the part of those of us struggling to find a way to make things better.

[I'm posting this late enough that it'll probably never be seen, but given my connection to the subject I still feel compelled to chime in.]

This isn't meant to trivialize what you're saying here, or to deny that a lot of parts of life can be pretty miserable for people who are poor. But what you're describing here sounds only partly like "I'm poor and life is hard": a lot of it also sounds like some pretty significant mental health challenges. Not that I'm in any way a professional! But if a friend of mine were talking this way, I'd encourage them as strongly as I could to find an expert to work with to help them find more positive ways of engaging with life.

Being poor does genuinely suck, and a lot of modern society seems to deliberately lean in to that. But I know quite a few poorer folks who still find joy in life, each in their own way. Human beings have always been resilient in difficult circumstances: I don't think we would have lasted through generations of evolution if a difficult life routinely led to despair.

The "ants" got fixed sometime in the past few months, I believe, and thank goodness: it really did make GIMP almost impossible to use for anything complicated enough to need GIMP. (But they've been working on my M1 Mac for a while now.)

We lost the Mars Climate Orbiter in 1999 because Lockheed Martin supplied a part that output results in pound-seconds and then that number was fed in to a NASA part that interpreted it as Newton-seconds.[1] Having US engineers speak a different language than all of the other engineers in the world imposes real, non-negligible costs for data checking and risks of failure for any project that might interact with non-US-centered expectations.

[1] https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_...

I can't find the solution post that you seem to be referring to here. The closest I've found is a link to Reddit where someone said "Turn off Sync Library and all that data will come back". But the original user responded saying that while the majority of songs came back, a few hundred were gone for good, and that Apple Support told them "sometimes that happens".

Is there a different, better solution that I haven't spotted yet? Or, what was the misunderstanding?

Okay, but you're now moving away from "How could people not know to make backups???" to "This problem could in principle be avoided by people who use specific types of backup software and maintain complete snapshots going back at least five years". Still a good idea, certainly, but it feels like we've moved well out of "holy shit" territory. (Also, isn't Apple's own built-in Time Machine exactly the sort of backup that you're talking about here?)

As for carefully monitoring your backup software to keep track of when files change, 1) I think we're getting even farther into the "not reasonable to expect of ordinary users" range here, and 2) if I did somehow happen to notice that a bunch of music files had changed, I'd be a lot more likely to assume that Apple Music had updated their ID3 tags than that it had completely rewritten the music!

In case it matters to you, the "GPT-2 Output Detector" rates this text as "99.68% Fake". (https://huggingface.co/openai-detector/) For comparison, the top three comments as of this writing got scores of 87%, 99.91%, and 99.98% Real.

I wouldn't be surprised if, within a few months or years, we all develop a reasonably solid ability to recognize AI generated text (in much the same way that the special effects that looked great in movies 30 years ago look pretty goofy today). But it seems that even before we reach that point, AI is already pretty good at recognizing its own.

I'm not an expert (I'm a physics prof who once took a seminar on nuclear arms control back in college), but what they're trying to do here is much, much harder than making an atomic bomb. If you want nuclear weapons, this work on carefully controlled and contained fusion is close to the opposite of what you'd need to do. (Fusion power is in general much cleaner than fission, at least where lasting radioactivity and waste are concerned.)

To be clear, the article title isn't inappropriate in a scientific context, but it does feel like clickbait to post it here: I can't see anything about this paper that would make it exciting to non-specialists.

I'll admit in advance that this physics failure came up in a particularly silly prompt. Here's an excerpt from the response:

[...] Carrie: Okay, so what's the equation?

Samantha: It's pretty simple. It's just F = q * v * B * sinθ, where F is the magnetic force, q is the charge, v is the velocity, B is the magnetic field, and θ is the angle between the velocity and the magnetic field.

Charlotte: Okay, that makes sense. So we just plug in the values for the charge, velocity, and magnetic field, and we get the magnetic force.

Miranda: Right. And we can use the right-hand rule to determine the direction of the magnetic force.

Samantha: Exactly. The right-hand rule is a simple way to remember the direction of the magnetic force. You just point your thumb in the direction of the velocity, and your fingers in the direction of the magnetic field. Then, the magnetic force will be in the direction of your middle finger.

Carrie: Okay, I think I understand. So if we have a point charge moving in the positive x-direction, and a magnetic field pointing in the positive z-direction, the magnetic force will be in the positive y-direction.

Charlotte: That's right. And if we have a point charge moving in the positive y-direction, and a magnetic field pointing in the negative x-direction, the magnetic force will be in the positive z-direction.

Miranda: And if we have a point charge moving in the negative z-direction, and a magnetic field pointing in the positive y-direction, the magnetic force will be in the negative x-direction. [...]

[Samantha has absolutely no idea how to describe the Right Hand Rule, and assuming it's a positive charge, only Charlotte gets the right answer.]

Your poem discussion example also illustrates why ChatGPT isn't a good source of answers and information, though!

Chocolate in Harry Potter is used to help people recover from the effects of Dementors. But I'm almost entirely certain that the books never mention anything called "the screechings" (whether cured with chocolate or not), and a variety of Google searches returning nothing backs me up on that. (Harry Potter fans usually have very thorough web resources that I'd expect to list things like this.) And Ron never sees Voldemort in Goblet of Fire.

The problem with this sort of tech is that there is absolutely no way to distinguish when it's retrieving solid, reliable information and when it's literally making up something that sounds plausible. I ran into the exact same thing earlier today when asking it to explain some physics concepts in entertaining ways. Everything was great for a while, and then suddenly there's some absolutely BS step that isn't remotely correct, and then it goes on with a pretty solid explanation. As a physics professor, I know which is which. But if I didn't already know the answer, I could very easily be badly misled.

It's an article about theoretical physics published in the 21st century, so it would be very surprising if it had not been posted on the arXiv before being published in a journal. And sure enough: https://arxiv.org/abs/2102.06824

Warning: lots of jargon ahead.

I really wish I understood this better, but the sense I've gotten is that intrinsic spin needs to couple to gravitation through torsion rather than through the usual curvature we study in GR. Most GR courses and textbooks barely mention torsion at all: IIRC Wald for example specifies "torsion free" as a condition on derivative operators and basically doesn't ever explore the alternative (I think there's a homework problem on it). The torsion free condition is what guarantees that Christoffel symbols are symmetric in their lower indices. Once upon a time while trying to understand all this back in grad school, I wrote up a set of notes extending Wald's calculations of curvature to include the possibility of torsion. I never tried to publish them anywhere, since of course it's nothing new or groundbreaking, but they're on my website here: http://www.slimy.com/~steuard/teaching/tutorials/GRtorsion.p...

Those notes do not discuss the connection to spin, because I was only halfway aware of it at the time and because I didn't have the time to delve into it enough to figure it out. (I also didn't know at the time that this is often called "Einstein-Cartan theory".) One notable thing about torsion is that it's a non-propagating field: as I recall, it's only non-zero inside the material with spin. I'm not entirely sure what the effects of all that might be. This 1976 review article has been lurking at the back of my to-read pile for ages: https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.48....

I have no idea whatsoever whether any of that is useful for making warp drives or for metric engineering. But I figured I'd share, since it seemed relevant.

It's interesting that in both of the examples people have shared here, the image produced was quite good but entirely missed the "flowing out of the building" part of the prompt (which I think is a fairly significant aspect of the scene).

The big difference that makes causality work is that there is only one timelike dimension (but three spacelike ones).

A purely spacelike curve can wrap back around and close on itself like a circle. But a purely timelike curve just can't turn around: it's like a person on a tightrope who's not allowed to slow down. So it's stuck going to later and later times forever (or to earlier and earlier ones, depending on orientation). (Yes, changes in reference frame broaden that 1D tightrope to a whole "future light cone", but that only allows limited changes of "heading": the time coordinate is guaranteed to be increasing no matter what.) And, roughly speaking, it would cost infinite energy to change from a timelike path to a spacelike one.

Speaking as a physics professor, you can listen to me talk about awesome physics all you want, and maybe feel like you're getting something out of it. But if you actually want to learn math or physics at any level beyond "I've heard those words before and they sounded cool", you absolutely must be doing it: solving problems as practice, struggling with how to apply subtle concepts to new situations, and just absorbing the details for a while.

Are you genuinely envisioning this math/physics beach vacation as "mostly homework"? Because if it's not going to be a completely surface-level experience, it's going to be "mostly homework". :)

It's genuinely good to hear that it's been appreciated (let alone so much). I owe the milkmaid example to my Calc 3 professor, many years ago, though I later realized that I'd probably altered it a little from his version.

I appreciate the kind words! And yeah, that could have even been MS Paint: it's been a long time, and I was still using Windows a lot back then. (I made the first version of this page for my wife when the topic came up in one of her graduate math courses: I'd had a much better exposure to Lagrange multipliers in my Calc 3 class than she'd had, and since she was studying in another state at the time I wrote it up in HTML instead of on paper.) I've occasionally thought about going back and redrawing those first few images in some better form, but hey: they still get the idea across perfectly well.

I have every intention of keeping it online indefinitely, as long as my friends doing the hosting don't get sick of me mooching off their web space.

Well, hey. I don't see my site show up here that often. If anyone's got comments, questions, or suggestions, I'll try to stop by and respond at some point.