robphy's latest activity
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robphy reacted to martinbn's post in the thread A The Causal Bootstrap Paradox in General Relativity with
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I think you have a misunderstanding of what an equation is. The equation doesn't say that ##T## determines or causes ##G##. It says that... -
robphy reacted to PeroK's post in the thread A The Causal Bootstrap Paradox in General Relativity with Like.
This "paradox" applies to many equations: Newton's second law, Maxwell's equations etc. It describes a mutual interdependence at the...
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robphy reacted to Herman Trivilino's post in the thread At what age is special relativity taught? with Like.
Also with an emphasis on events. The notion that an event occurs at a particular time but lasts for no time at all. This is needed so...
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robphy replied to the thread At what age is special relativity taught?.I think kinematics in PHY 101 should be taught with more position vs time graphs, with a structural comparison to Euclidean geometry. I...
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robphy replied to the thread I Dirac's 1972 Boston talk on Projective geometry in quantum mechanics.The use of the colon in the originally-given url is odd: https://repository.lib.fsu.edu/islandora/object/fsu:195 Try...
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robphy reacted to TSny's post in the thread I Dirac's 1972 Boston talk on Projective geometry in quantum mechanics with Like.
I think these are the notes. They look sketchy, but there are a few diagrams.
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robphy replied to the thread Music Cover songs versus the original track, which ones are better?.War Pigs & Mr Crowley (last performances by Ozzy Osbourne and Black Sabbath... and covers in honor of this) (July 5, 2025) Black...
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robphy reacted to pinball1970's post in the thread Music Cover songs versus the original track, which ones are better? with Like.
Original Cover 1 Cover 2 seven years later.
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robphy reacted to Owe Kristiansen's post in the thread I A "continous" gravitational field formula r=0 to infinity with Like.
Thanks for visualizing my formula and letting me know about desmos.
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robphy replied to the thread Prove that the integral is equal to ##\pi^2/8##.This must be a popular question. https://artofproblemsolving.com/community/c7h3603912_prove_that_the_following_integral_equals_pi28...
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robphy replied to the thread At what age is special relativity taught?.ISTEP-Program-and-Book-of-Abstracts I'll be there in Perth from Thu Jul 10 to Sun Jul 13. My talk ( "Spacetime Trigonometry: a unified...
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robphy posted the thread AAPT 2025 Summer Meeting Washington DC (August 2025) - are you going? in STEM Educators and Teaching.2025 AAPT Summer Meeting in Washington DC (Aug 2-6) https://www.aapt.org/Conferences/SM2025/ (Online Program) I'll be there Sun Aug 3...
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robphy replied to the thread I A "continous" gravitational field formula r=0 to infinity.Some suggestions: ##g(r) = \frac {4 \pi G d r^3}{3 r^2}## for ##r < R## ##g(r) = \frac{4 \pi G d R^3}{3r^2}## for ##r \ge R## (use \ge...
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robphy replied to the thread Prove that the integral is equal to ##\pi^2/8##.Possibly useful: https://www.doubtnut.com/qna/121560332 https://www.doubtnut.com/qna/642670805 $$\int_{0}^{1}\frac{\arcsin...
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robphy reacted to fresh_42's post in the thread Prove that the integral is equal to ##\pi^2/8## with Like.
Yes, that's basically my formula for ##f(\alpha)f(-\alpha).## It reveals the symmetry of the curve. If we ignore the inverse sine, then...