T + 4.6 s: chaos → disc
the far side of the disc, bent over the top
the photon ring: light that went round
the shadow: nothing comes back
the same points that were the attractor
inner grains run faster: Kepler’s third law
light can orbit at 1.5 horizon radii; what goes round once or twice, then out, makes the thin ring at the shadow’s edge
the shadow is 2.6 times the horizon: light aimed any closer than that is bent in, and falls
Kepler, 1619: T² grows as r³. the disc’s outer edge is 4× its inner one, so its grains take 8× as long to go round

AION

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