The funnel is
not the gravity
This is Flamm's paraboloid: a slice of space around a mass, bent into a third dimension so the stretched distances become visible. The dip is not a hill things roll down. It is a statement that a ruler laid near the mass measures more length than you would expect.
lawz(r) = 2√(rₛ(r − rₛ)) for the Schwarzschild exterior, with rₛ = 2GM/c². Clocks there run slow by √(1 − rₛ/r).
tryDrag the probe ring in toward the shaded circle.
noticeThe surface turns vertical at the horizon: radial distance diverges and the time factor falls to zero. Beyond it the embedding stops existing — which is the diagram's honest limit, not a rendering gap.
in lifeGPS satellites gain about 38 microseconds a day from this; uncorrected, positions drift kilometres.
found bySchwarzschild solved Einstein's equations in 1916 while serving at the front; Flamm drew the embedding that same year.