pervect's latest activity
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Ppervect replied to the thread Graduate What Exactly Is The Physical Content Of Maxwell's Equations?.The thing I found most interesting was how that if you postulate magnetic monopoles, the duality between the homogeneous and...
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Ppervect replied to the thread Graduate Feynman's bug (hot plate) in generality.I'm familiar with Einstein writing about the hot plate, but not about Feynmann doing so. My take on the problem is that locally, the...
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Ppervect replied to the thread Graduate About the definition of Born rigidity.I suggest thinking of a "standard ruler" as a pair of worldlines, one for each end. On a space-time diagram, a "standard ruler" is a...
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Ppervect replied to the thread Undergrad Euclidean geometry and gravity.Good luck with your studies and your journey of exploration of physics.
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Ppervect replied to the thread Undergrad Euclidean geometry and gravity.One of the early steps, though perhaps not the very first, would be to pick a textbook appropriate to your background. It's...
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Ppervect posted the thread Graduate Orbits of a photon that can't quite cross the photon sphere of a BH in Special and General Relativity.First, some background. Sorry, it's a bit long. I've been considering the orbits of photons around a black hole. First some...
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Ppervect replied to the thread Graduate About the definition of Born rigidity.I had to look this up. My source is not the best, but it says the indices in h_ab do run from 0..3. I'm not sure if I actually said...
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Ppervect replied to the thread Graduate About the definition of Born rigidity.The two formal defintions of born rigidity I'm aware of apply to timelike congruence which I will denote as ##u^a##. I believe the...
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Ppervect replied to the thread High School Rotating disc: tidal relativity across surface of disc.I don't understand the reference to "trying to turn into a torus", but I did find references (and also had vague recollections that I...
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Ppervect replied to the thread High School Rotating disc: tidal relativity across surface of disc.Do you have a reference? I was unable to confirm, though I did run into some interesting reading about bar mode instabilities for a...
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Ppervect replied to the thread High School Rotating disc: tidal relativity across surface of disc.To understand the rotating disk in special relativity, I believe you need some background material that is not high school level. The...
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Ppervect replied to the thread Undergrad How many sorts of time are there in physics?.That's a good comment, it might be worth mentioning a list of commonly used coordinate time standards besides cosmological time. The...
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Ppervect posted the thread Undergrad How many sorts of time are there in physics? in Special and General Relativity.Some recent threads inspired me to want to make a list of the different notions of time we need in physics (As I write this, I am...
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Ppervect replied to the thread Undergrad Gravitational analog of electromagnetic force.The organizational structure in MTW actually illustrates why there are 20 degrees of freedom and 21 unique (up to sign) nonzero...
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Ppervect replied to the thread Undergrad Gravitational analog of electromagnetic force.I was doing some more reading, and apparently the "modern" approach to the topic involves decomposing the Weyl tensor rather than the...