Beer Question #1: What Actually Feeds Spacetime Curvature?
Aphyr’s old professor had a standing rule: if a question was too hairy for class, it became a “beer question”—something to settle over pints at the pub. In that spirit, Aphyr is offering unlimited drinks to anyone who can crack a genuinely deep one from general relativity.
The puzzle starts with the stress-energy tensor T, whose components are basically four-momentum density and flux—what we casually call “energy” and “momentum.” Photons count, and so do other particles carrying four-momentum. But the real question is:
What else contributes to T? Do electrostatics matter? What about the vector potential or the strong nuclear force? In other words—what makes something contribute to spacetime curvature at all?
The bet stands: buy the explainer as many beers as it takes.
