Invariant mass

See? The result will always flawlessly subtract back down to exactly one.

The energy went up, the momentum appeared out of nowhere to offset it, but the structural difference of their squares, the actual invariant mass never shifted a millimeter.

The geometry mathematically protects the mass from relativity.

Which carries a profound philosophical implication for how we actually view reality.

Because we have spent this entire deep dive treating C squared and R squared as fundamentally different domains, right?

Right.

We contrasted gravity's spreading out over an expanding sphere with space-time's rigid measuring of invariant mass.

Exactly.