PAllen's latest activity

If you make the distant light source a flash bulb (at rest in screen frame), the fixes simultaneity. Then, you will definitely see a...

A number of teachers have been interested in collecting the black and white films that were part of the PSSC program in the 1960s. Many...

Possibly useful: www.reddit.com/r/Physics/comments/162yl28/all_the_classic_pssc_physics_films_i_have_found/ and the last URL in that...

Happy holidays folks. So I spent some time over the Thanksgiving holidays and developed a program that renders electric field lines of...

Regarding post #21, the formula given for area minimizing ##\theta## simplifies to ##\tan\theta=c/d##. The minimum area just becomes...

Ok, if we're bringing this back, I'll share my results. In reference to the diagram in the original post, let c be the segment labeled...

So, FW transport along any curve will preserve all of these properties. Parallel transport will only preserve them along a geodesic. For...

But that operation is typically called the exponential map (and is a completely rigorous construct)...

That is an exceedingly narrow statement of the equivalence principle. The most commonly accepted meaning of strong equivalence principle...

That's not an update. It shares exactly one author, and the topic is not the same. Obviously, there is some relationship, but that's...

I wondered if anyone had ever treated voids using numerical relativity rather than more indirect approximations. I came across the...

While the FLRW metric, when used for a realistic universe, is purely an emergent approximation at large scales, there is one aspect of...

Yeah, but if you are talking about galaxies, you are outside the FLRW idealized model - that has only perfect fluid with different...

As far as I know, the common models of quintessence still use the FLRW equation metric, just with particular forms of ##a(t)##. In...

One thought that occurs to me is that virtually all learning is self-learning. If you enroll in a course and listen to the lectures but...