Special relativity gave us invariant spacetime in the absence of gravity. General relativity goes further: freely falling bodies follow the geometry of spacetime, and tidal effects reveal that the geometry is curved. This lab builds that idea one piece at a time.
Send a horizontal light pulse across an elevator that accelerates upward. In the elevator frame, the floor rises while the light is in flight, so the light appears to bend downward. This is the local intuition behind the equivalence principle.
Two nearby freely falling objects can accelerate relative to one another. In the weak-field limit around a spherical mass, radial separation is stretched while transverse separation is squeezed. General relativity encodes this relative acceleration in spacetime curvature.
For a static clock outside a non-rotating spherical mass, the exterior Schwarzschild solution gives a simple clock-rate factor. Move two clocks to different radii and compare how much proper time each accumulates relative to Schwarzschild coordinate time at infinity.
A Schwarzschild black hole has a hierarchy of radii that has no Newtonian equivalent: the event horizon, the photon sphere, and the innermost stable circular orbit. Move a test radius and see which circular motions are possible.
Relativity tells us how spacetime behaves. The next layer will turn to fields and particles: how a field stores energy and momentum, how classical electromagnetic fields evolve, and how quantum theory changes what we mean by a “particle.”