Space and the exiled Aether
RSI traces how physics discarded the Aether, then found that empty space bends, and Einstein conceded that space has physical qualities.
In the early twentieth century, experiments failed to detect the luminiferous Aether, a proposed medium for light. To keep the speed of light invariant, physics redefined space as a geometric stage: a coordinate system with no physical properties of its own.
Scarcely a decade later, general relativity showed that this same emptiness could curve, ripple, stretch, and compress. Space was no longer passive. In his 1920 Leiden lecture, Einstein acknowledged that "space without aether is unthinkable." He distinguished this idea from the mechanical ether of the nineteenth century, but his point was clear: empty space could not be physically empty.
RSI reads this history as a transformation, not an elimination. The medium returned under new names, such as metric field, spacetime manifold, or quantum vacuum, introduced through mathematics rather than ontology. Einstein himself regarded relativity as incomplete, because it left the structure of matter unexplained.
From the paper: Chapter I, The tension begins with space itself. Read the full section
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