Scalar-Tensor Hydrodynamics: Gravity as the Response of a Vacuum Medium. A Modified Gravity Framework for Vacuum Viscosity and Cyclic Vacuum Cosmology

A theoretical proposal built on one premise: there is no empty space. The vacuum is treated as a single continuous medium, the Ocean, with its own stress-energy, pressure and internal flow, and with no edges and no outside. What are conventionally called particles are treated as localized excitations of the medium, and gravity is proposed to be the medium's response to concentrated energy. The medium has one speed, at which every disturbance travels, and gravity is where that speed varies from place to place. No speed is fixed: the measured speed of light is the local carrying speed read by rulers and clocks made of the same medium. Einstein's equation is retained as the effective description of that response.

Two principles of the framework, that the medium stays in step and that nothing is counted twice, give General Relativity's geometry outside a non-spinning mass, including its point of no return and the observed size of the shadow of Sagittarius A*. Around a spinning mass, a pattern's surroundings are re-made as it travels and tilted by its travel; summed over the Earth's spinning parts they give the frame dragging measured by Gravity Probe B, LAGEOS, LARES and LARES-2, carried continuously by the re-made state.

Version 3.12 adds the rebuild and the law. The medium rebuilds every pattern continuously, and the rebuild has two sides: building, which makes matter and time, and reclaiming, which unmakes them and is antimatter. Time is made in the build, each place making its own, and gravity is the uneven making of time. Antimatter stays hidden because it runs into a past that was never a present; visible antimatter is a reclaiming with no build of its own. At the end of a beat the drive runs out and the reclaiming carries the medium, taking away time, structure and disorder and returning the energy. The law states what a build carries and the rule for each quantity, and sets the strength of gravity by a count of the kinds of wave the medium sustains: with fifteen built per family gravity attracts and the medium's smallest scale lies near the Planck length. It commits to one prediction, neutrinoless double-beta decay. The electron's 0.511 MeV is the lowest energy of its own kind of wave, set by a field the medium's flow sustains. A galaxy sits in an eddy of the medium's current, whose swirl turns its stars' travel inward, with a stated prediction for vertical motion near the disk. The open items are gathered in one section. Version 3.12.1 adds Appendix A, the rebuild of a spinning black hole: Sagittarius A* taken through the same steps as the Earth's rebuild, with a table comparing the two regimes; it is also issued as a standalone PDF. Every part of the paper carries a checksum token, and a reading manifest with a document digest (a764-2c56-a31a) lets any reader confirm a complete reading.

This is a proposal, not an established theory. The document states its own falsification conditions explicitly and carries an itemized research program, several items of which could terminate the framework.