Recent content by robphy

Here's a 2025 interview with Abhay Ashtekar (Penn State), split into parts. (I was especially interested in his stories with Robert Geroch [his advisor at UT-Austin and UChicago] and Chandrasekhar. I had taken courses with Geroch at UChicago and with Ashtekar at SyracuseU, and both were very...

And so, a model (motivated by physically observed phenomena) and a set of tools to analyze the model lead to testable predictions, which (within its range of application) agrees with many experiments. Many other candidate models (possibly promising when formulated), however, do not agree with...

The Michelson-Morley apparatus is essentially a [typical] transverse light-clock (whose light-signal is perpendicular to the direction of relative motion with respect to the lab frame) and a longitudinal light-clock (whose light-signal is parallel...). From a flash at the origin-event O, its...

In special relativity, there is no such reference frame (that is equivalent to that of a typical ["timelike"] observer) where light is at rest [since a light-signal has a worldline whose tangent is "lightlike" or "null"]. The second postulate is that light travels with the same speed according...

In geometry and Riemannian geometry, one uses tangents to curves and normals to curves. So, in the Minkowskian spacetime geometry of special-relativity and the Lorentz-signauture pseudoriemannian geometry of general-relativity, one also uses tangents to worldlines and spacetime-normals to those...

Is it just Tungsten, or are there other metals available (in the same size)? These could be useful for measurements of mass and volume and thus density. e.g., https://www.google.com/search?q=density+set (suggestions of size) In addition, it (among other metals) could be useful for calorimetry...

(Maybe this discussion of how to teach "relativity of simultaneity" can be split off and given an appropriate title, but linked from this thread.) (Maybe this should be converted to an Insight.) From my recent consecutive posts...

Here are some slides from Vokos' talk at https://www.aapt.org/doorway/TGRU/ https://www.aapt.org/doorway/tgrutalks/vokos/Vokos_AAPT_TGRU.pdf Sadly, there are no spacetime diagrams above. (I maintain my position.... standard-textbook presentations and event-diagrams are not good enough.)...

Here is the arxiv version Student understanding of time in special relativity: simultaneity and reference frames Rachel E. Scherr, Peter S. Shaffer, Stamatis Vokos https://arxiv.org/abs/physics/0207109 https://doi.org/10.1119/1.1371254 Am. J. Phys. 69, S24–S35 (2001) AN INVESTIGATION OF...

https://en.wikipedia.org/wiki/Psycho_Killer (1977) https://en.wikipedia.org/wiki/Talking_Heads Talking Heads - Psycho Killer (Earliest Live Video, Live at CBGB's,1975) - "Psycho Killer (1974 Demo)" The Artistics (1974, from "Tentative Decisions: Demos & Live" LP) -...

Concerning high-school physics clubs, here are more ideas from other platforms: www.reddit.com/r/AskPhysics/comments/fgqeid/high_school_physics_club/ https://www.quora.com/How-do-I-start-a-high-school-physics-club...

This is an enlightening video: “The Future of Veritasium”

Since this resource hasn't already been mentioned... https://www.feynmanlectures.caltech.edu/ in particular, there's "Feynman's Tips on Physics" https://www.feynmanlectures.caltech.edu/TIPS_toc.html and https://www.feynmanlectures.caltech.edu/info/exercises.html...

I have used Hewitt for the past four years for a college conceptual-physics course (focusing on mechanics and waves). It is a really good book, although there are some sections that could be revised. A comparable book that I have used for another conceptual-physics class at another institution...

First, I acknowledge what you say about spacetime diagrams being confusing. So, some of my efforts have tried to develop additional geometric intuition, not found in typical references. Second, I do wish to point out that a "PHY-101 position-vs-time graph" is also a diagram with a non-euclidean...