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I've been breaking my head open lately over special relativity and its conception of spacetime's dynamical as well as kinematical features. One thing that has stuck in my head is that of whether the concept of relative/absolute simultaneity in a relationist spacetime is different from a substantivalist spacetime? What I mean by relationism and substantivalism is the anti-realist vs. realist distinction between whether spacetime is, generally as i've understood it, reducible or irreducible (has to be taken as a real primitive thing).

Given the assumption that we know spacetime is a real thing, then the concept of relative simultaneity in special relativity or absolute simultaneity in Lorentzian relativity takes on a similar philosophical flavor to presentations of the theory i've seen in other places. What if, however, we treat relativistic spacetime in a relationist guise? Do the concepts of absolute/relative simultaneity change and how? Further, in what ways do these two presentations of simultaneity in different ontological frameworks differ or remain the same?

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I've been breaking my head open lately over special relativity and its conception of spacetime's dynamical as well as kinematical features.

Given that you've also written

then the concept of relative simultaneity in special relativity or absolute simultaneity in Lorentzian relativity takes on a similar philosophical flavor to presentations of the theory i've seen in other places.

Perhaps you need to clarify for yourself as to your understanding of the physics here at stake. It's absolute simultaneity in Newtonian spacetime, and relative simultaniety in Lorentzian spacetime, which is merely special relativity generalised to other spatial dimensions.

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  • Not necessarily, as is presented here, en.wikipedia.org/wiki/Lorentz_ether_theory. I'm not talking about lorentzian spacetime in that paragraph i'm talking about a rival interpretation of special relativity that goes by lorentzian relativity. Loot it up i'm not abusing the terminology its already been misused. Lorentzian relativity merely adds an extra preferred frame of reference in a still definitely existant spacetime.
    – The victorious truther
    Mar 1, 2020 at 20:53
  • I know its confusing that Minkowski spacetime is sometimes called Lorentzian spacetime and there is a rival interpretation of special relativity that goes by Lorentz-ether theory or sometimes just Lorentzian special relativity.
    – The victorious truther
    Mar 1, 2020 at 20:59
  • @JustinOrosz: Whats confusing is the way you have phrased your question. Given that you know that there is such a thing as Lorentzian spacetime, I find it odd that you might not think that when referring to Lorentzian relativity people might not suppose ordinary special relativity generalised to Lorentizian spacetimes.
    – Mozibur Ullah
    Mar 2, 2020 at 17:30
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    I assumed most people knew about Lorentz vs Einstein relativistic interpretations. Further when others refer directly to the actual spacetime structure of special relativity they usually preface it by saying its Minkowski spacetime.
    – The victorious truther
    Mar 2, 2020 at 22:13
  • @Thevictorioustruther: And besides, the Wikipedia article you linked to calls it "The Lorentz Ether Theory", presumably to avoid confusion with relativity per se.
    – Mozibur Ullah
    Aug 20, 2022 at 16:09
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As I learn from the comments to your question you compare two rival theories to explain the Michelson-Morley experiment (MM), which does not show any movement against a hypothetical ether:

• Lorentz Ether Theory (LET) due to Lorentz. (In your question „relationist(?)=substantivalist(?)“) LET explains the negative answer of the MM-experiment by the Lorentz contraction with the factor gamma=1/sqrt(1-(v/c)**2.

• Special Relativity (SR) due to Einstein. (In your question „relativist(?)“). SR dismisses the whole ether concept as obsolete. SR is based on the Lorentz transformation, which represents the symmetry group of Maxwell’s electrodynamics, and on the hypothesis of the observer independent constant speed of light.

History has shown that the more radical SR introduces more powerful concepts than LET, hence SR has more explanatory value. The basic ideas of the two approaches are completely different. Hence I cannot recognize the benefit when treating „relativistic spacetime in a relationist guise“.

Don’t you think it could be like filling new wine into old skins?

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