Geometric Structure
The way to determine distance, volumes and transformations in spacetime.
- Presumed
- Newton: time and space are absolute, no t/R rotations (boosts).
- Special relativity: Only inertial observers.
- Background chosen
Maxwell: Could be any metric, you choose.
- Background-Free
GR: Solve field equations for the metric.
Any theory for gravity must be background-free.
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