PeterDonis's latest activity
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PeterDonis reacted to PAllen's post in the thread Undergrad Euclidean geometry and gravity with
Like.
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... -
PeterDonis reacted to PAllen's post in the thread Undergrad Euclidean geometry and gravity with Like.
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...
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PeterDonis replied to the thread Undergrad Relativity of simultaneity in actuality.No, that's not correct. What is correct is that the lightning strike events have a particular relationship in spacetime, and in any...
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PeterDonis reacted to Dale's post in the thread Undergrad Relativity of simultaneity in actuality with Like.
All of our experiments done to date over more than a century indicate that reality is accurately described by special relativity on a...
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PeterDonis reacted to Ibix's post in the thread Undergrad Relativity of simultaneity in actuality with Like.
Note that the figures you've reproduced show two different experiments. In figure 2-1 the strikes are simultaneous in S, and if that...
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PeterDonis replied to the thread Undergrad Euclidean geometry and gravity.In a generic curved spacetime, yes, because the two types of rigid motions allowed by the H-N theorem each depend on the spacetime...
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PeterDonis replied to the thread Undergrad Euclidean geometry and gravity.Yes, agreed. But... They're not orthogonal to the static congruence (the Killing congruence), yes. They are orthogonal to the...
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PeterDonis replied to the thread Undergrad Euclidean geometry and gravity.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...
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PeterDonis replied to the thread Undergrad Euclidean geometry and gravity.Note that this implies a comparison with the corresponding accelerated object in flat spacetime--in the case under discussion in this...
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PeterDonis reacted to PAllen's post in the thread Undergrad Euclidean geometry and gravity with Like.
The only such stresses on a rigid object, whatever its history, are those of tidal gravity.
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PeterDonis replied to the thread Undergrad Euclidean geometry and gravity.Of course not. We're not disputing that treating the object as a test object as far as determining the spacetime geometry is concerned...
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PeterDonis replied to the thread Undergrad Euclidean geometry and gravity.We're not talking about having the object affect the spacetime geometry; we're assuming the spacetime geometry is fixed. We're talking...
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PeterDonis replied to the thread Undergrad Euclidean geometry and gravity.I'm wondering why you said this:
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PeterDonis replied to the thread Undergrad Euclidean geometry and gravity.Are you claiming that this statement is true?
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PeterDonis replied to the thread Undergrad Euclidean geometry and gravity.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...