Dale's latest activity
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Dale replied to the thread I Is using r as a coordinate in Birkhoff's theorem a limitation?.Agreed. Such manifolds are not excluded a priori. And since the result of the theorem does not contain such solutions, the conclusion is... -
Dale reacted to PeterDonis's post in the thread I Is using r as a coordinate in Birkhoff's theorem a limitation? with
Like.
No. The areal radius ##r## is an invariant. Picking it as one of the coordinates helps in making the proof of Birkhoff's Theorem look... -
Dale replied to the thread I Is using r as a coordinate in Birkhoff's theorem a limitation?.In principle, you should be able to have a manifold with two distinct ##r=0## loci. Consider a sphere, latitude lines are submanifolds...
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Dale replied to the thread I Is using r as a coordinate in Birkhoff's theorem a limitation?.I think it is proven by Birkhoff’s theorem. Birkhoff’s theorem shows that the spherical vacuum metric is unique. If the metric you...
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Dale replied to the thread I Is using r as a coordinate in Birkhoff's theorem a limitation?.I think you are correct that such a manifold is excluded from Birkhoff’s theorem. However, I think it is not a problem with the theorem...
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Dale reacted to Pencilvester's post in the thread I Is using r as a coordinate in Birkhoff's theorem a limitation? with Like.
Right, so doesn’t making ##r## a coordinate that ought to cover the spacetime restrict the number of possible spherically symmetric...
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Dale replied to the thread I Is using r as a coordinate in Birkhoff's theorem a limitation?.I agree. You would have to use at least two separate charts to cover that spacetime.
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Dale replied to the thread I Is using r as a coordinate in Birkhoff's theorem a limitation?.So you are thinking of manifolds where spacetime is foliated as a family of concentric spheres. But the size of those spheres, for...
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Dale reacted to Pencilvester's post in the thread I Is using r as a coordinate in Birkhoff's theorem a limitation? with Like.
In Birkhoff’s theorem, doesn’t assuming we can use r (defined as circumference divided by ## 2 \pi ## for any given sphere) as a...
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Dale replied to the thread I Question about special relativity and magnetism.Yes, that is the case. I think you misunderstood the videos, but you correctly understood the physics. The fact that the wire is...
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Well, you have claimed counterfactual things (e.g., that aberration does not apply) multiple times in this thread, so we do need to...
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Dale reacted to Herman Trivilino's post in the thread I The Einstein Clock aka Light Clock with Like.
What is the reason you are studying this paper? Are you trying to understand the physics? Or are you trying to understand the physics...
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Idealising the emission to a single event, that event is independent of the state of motion of the source (note that this is an...
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PS note that it is the speed of light that is independent of the motion of the source. Not the velocity of light, which is a vector and...
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Dale replied to the thread I The Einstein Clock aka Light Clock.Yes, there is a problem. The problem is here: That is false. The source of light is current and charge densities, as described by...