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PeterDonis's latest activity
PeterDonis
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PAllen's post
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Euclidean geometry and gravity
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I will make a self correction which implies we were both right/wrong in a sense. Again, I think the correct analog to a well understood...
Oct 21, 2025
PeterDonis
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PAllen's post
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In my view, this is not a sensible approach. What you have is a collection of independent rockets, not a body. In a body, in any normal...
Oct 21, 2025
PeterDonis
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Relativity of simultaneity in actuality
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No, that's not correct. What is correct is that the lightning strike events have a particular relationship in spacetime, and in any...
Oct 20, 2025
PeterDonis
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Relativity of simultaneity in actuality
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All of our experiments done to date over more than a century indicate that reality is accurately described by special relativity on a...
Oct 20, 2025
PeterDonis
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Ibix's post
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Relativity of simultaneity in actuality
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Note that the figures you've reproduced show two different experiments. In figure 2-1 the strikes are simultaneous in S, and if that...
Oct 20, 2025
PeterDonis
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Euclidean geometry and gravity
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In a generic curved spacetime, yes, because the two types of rigid motions allowed by the H-N theorem each depend on the spacetime...
Oct 20, 2025
PeterDonis
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Euclidean geometry and gravity
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Yes, agreed. But... They're not orthogonal to the static congruence (the Killing congruence), yes. They are orthogonal to the...
Oct 20, 2025
PeterDonis
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Euclidean geometry and gravity
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I'll see if I can find any references in the previous threads we had here. At least one of them, IIRC, dealt with a scenario in...
Oct 20, 2025
PeterDonis
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Euclidean geometry and gravity
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Note that this implies a comparison with the corresponding accelerated object in flat spacetime--in the case under discussion in this...
Oct 20, 2025
PeterDonis
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Euclidean geometry and gravity
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The only such stresses on a rigid object, whatever its history, are those of tidal gravity.
Oct 20, 2025
PeterDonis
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Euclidean geometry and gravity
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Of course not. We're not disputing that treating the object as a test object as far as determining the spacetime geometry is concerned...
Oct 20, 2025
PeterDonis
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I
Euclidean geometry and gravity
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We're not talking about having the object affect the spacetime geometry; we're assuming the spacetime geometry is fixed. We're talking...
Oct 20, 2025
PeterDonis
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I
Euclidean geometry and gravity
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I'm wondering why you said this:
Oct 19, 2025
PeterDonis
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Euclidean geometry and gravity
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Are you claiming that this statement is true?
Oct 19, 2025
PeterDonis
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Euclidean geometry and gravity
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A spacelike geodesic in the Flamm paraboloid. Note that such a curve is not one that either an ordinary object or a light ray will...
Oct 19, 2025
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