Recent content by robphy

It looks like Danny Sapko (the BEHS-player) is alleging Mohini Dey (and other musicians named in Sapko's Nov 30 video) supports AI music (SUNO), and there's been a back and forth on YouTube. 🍿 (Sapko Feb 26, 2026) The allegations against Mohini Dey (Dey Dec 13, 2025) Mohini Dey Responds to...

links to this Facebook post by the University of Manchester featuring a video of their re-enactment in English (navigate to 3m45s) This blog post https://telescoper.blog/2025/09/12/einsteins-first-lecture-in-britain/ had an image of the printed article...

On an AAPT mailing list, I was alerted to https://www.change.org/p/honor-emmy-noether-with-the-unit-for-momentum

more covers at #1,911 The Hellion/Electric Eye more =1050205&o=date']Hagane on PF

Another good tool is "Tracker" https://opensourcephysics.github.io/tracker-website/ which does video analysis. It can be trained to track a ball (e.g. a bright object that contrasts well from its background). Ideally, use a tripod, avoid parallax and other optical distortions, and have a...

possibly useful set of links https://physics.tcnj.edu/online-teaching-resources-for-physics-instructors/ I second @kuruman 's suggestion of phyphox . I had my students ride an elevator and watch a digital scale with a 100g mass sitting on top of it. As they rode the elevator, i told them to...

Here's a different approach by Fred Hehl: (1999) Classical Electrodynamics: A Tutorial on its Foundations Friedrich W. Hehl, Yuri N. Obukhov†, Guillermo F. Rubilar https://arxiv.org/pdf/physics/9907046 (2000) "A gentle introduction to the foundations of classical electrodynamics: The meaning...

In my websearch for conventions in Geometric Algebra, I stumbled upon two vocal critics of GA (listed below). Since I am just learning about GA, I can't vouch for the correctness of anything these folks say. ... but it might be worth a look The Case Against Geometric Algebra...

From an old thread of yours on Geometric Algebra https://www.physicsforums.com/threads/sr-ga-multivector-vs-tensor-notation-maxwells-equations.1078087/ I said... There's needs to be a table of sign conventions [and other conventions (like notation)] to help translate between the works of GA...

Yes. So, one can conclude (again) the various expressions obtained are equal.

"Raising" and "lowering" are just notational shortcuts that hide the [invertible] metric. How would you evaluate ##g_{\mu \nu} \left( g^{\nu \rho} - g^{\rho \nu} \right) ## ?

(2026) audrey123talks - #Slayer - War Ensemble cover guitar and lefty bass +#スレイヤー [You can hear the bass more clearly in the Mar 2025 version .] They have many versions of audrey123talks playing War Ensemble, starting with them playing Rocksmith. (more Kate and Audrey...

(2026) Maya Neelakantan (12 years old) - War Ensemble — Slayer | Guitar Riffs + Jeff Hanneman Solo Tribute see also Maya Neelakantan - #18 in Talent Worthy of Wider Recognition

https://en.wikipedia.org/wiki/You%27re_No_Good NEW * You're No Good - Linda Ronstadt {Stereo} 1974 Van Halen You're No Good live from Rochester, NY - May 18, 1979

Although this has some overlap with causal structure and relativity, your specific questions are more about the mathematics rather than physics. So, I think a continued discussion on these specific questions is better suited for a mathematics forum, not here on this relativity forum. (The...