cianfa72's latest activity
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cianfa72 replied to the thread I Follow-up Einstein Definition of Simultaneity for Langevin Observers.Ah ok. So starting from one single 1D spacelike line Minkowski orthogonal to the Langevin worldlines on the cylinder of given radius... -
cianfa72 replied to the thread 3-terminal device external modeling.Right, but it isn't my point. Consider a three terminal electronic device, whatever. What is the number of equations that the 3 current...
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cianfa72 replied to the thread 3-terminal device external modeling.Yes, the three terminal device can be modeled as an unbalanced two port black box with the terminal picked as reference ground...
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cianfa72 posted the thread I Follow-up Einstein Definition of Simultaneity for Langevin Observers in Special and General Relativity.Reading again this old thread Einstein Definition of Simultaneity for Langevin Observers, I'd like to ask about the following. Consider...
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Very basic question. Consider a 3-terminal device with terminals say A,B,C. Kirchhoff Current Law (KCL) and Kirchhoff Voltage Law (KVL)...
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cianfa72 replied to the thread I Follow-up on the Expanding Universe Insight article.Ah ok, basically for "small" ##x## the term involving ##x^2## in $$\tau \simeq t + \frac{1}{2}H_0 a_0^2 x^2 = t + \frac{1}{2} a’^2_0...
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cianfa72 posted the thread I Follow-up on the Expanding Universe Insight article in Special and General Relativity.Hi, reading this Insight raised a doubt regarding the section "Comoving observers in a local Minkowski frame". Robertson-Walker (RW)...
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cianfa72 reacted to Ibix's post in the thread B Flatlander analogy of spherical surface as observable universe with
Like.
It isn't. Curved spacetime is often visualised using a 2d sheet embedded in a 3d space, true, but the higher dimensional embedding space... -
cianfa72 replied to the thread A 1-Way Speed of Light.It is worth noting that in some specific cases the two family of "slanted" grid lines drawn in the diagram may result as orthogonal...
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cianfa72 reacted to jbergman's post in the thread I Spacetime coordinate smoothness requirement with Like.
Polar coordinates are not a valid chart for an open set ##U## containing the origin since the transition function with the identity...
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They will see stars if they look in the tangential direction (along the photon sphere), including multiple images of stars (including...
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cianfa72 reacted to PeterDonis's post in the thread B How to compare the proper times of two spatially distant mass points? with Like.
You can always compare the proper times of two objects if you have already determined which pair of events on each worldline you will...
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cianfa72 reacted to PeterDonis's post in the thread I A question about geodesics and notion of parallelism with Like.
In a curved manifold, vectors are not spacetime objects, they are objects in the tangent space at a point. So are tensors such as the...
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cianfa72 reacted to PeterDonis's post in the thread I Determining a stationary point of reference to base all absolute motion with
Agree.
All velocity is relative in relativity. It's just that, for timelike objects (objects like us and rocket ships), their velocity relative... -
cianfa72 replied to the thread A 1-Way Speed of Light.As @Ibix showed, the orthogonal grey grid lines in the diagram actually correspond/represent straight lines orthogonal in spacetime...