Tuesday, December 9, 2025

Maybe we can create spacetime

Suppose a substantivalist view of spacetime on which points of spacetime really exist.

Suppose I had taken a different path to my office today. Then the curvature of spacetime would have been slightly different according to General Relativity.

Question: Would spacetime have had the same points, but with different metric relations, or would spacetime have had different points with different metric relations?

If we go for the same points option, then we have to say that the distance between two points is not an essential property of the two points. Moreover it then turns out that spacetime has degrees of freedom that are completely unaccounted for in General Relativity, degrees of freedom that specify ``where’’ (with respect to the metric) our world’s points of spacetime would be in counterfactual situations. This makes for a much more complicated theory.

If we go for the different points option, then we have the cool capability of creating points of spacetime by waving our arms. While this is a little counterintuitive, it seems to me to be the best answer. Perhaps the best story here is that points of spacetime are individuated by the limiting metric properties of the patches of spacetime near them and by their causal history.

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