Bartosz Milewski on Nostr: Assume that they are both falling one after another along the same straight line ...

Assume that they are both falling one after another along the same straight line towards the singularity (they maneuvered themselves into this trajectory when still at some distance from the black hole). Bob sees Alice always directly in front of him. So unless he bumps into her crossing the horizon, his perception of where the horizon is must be different from hers.