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zhermes

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**Time dilation and black-hole--black-hole mergers, and ringdown gravitational waves**

An observer far away from an event horizon never sees a particle cross the event horizon. How does this effect the apparent merger of two black holes?

Also, I've seen that the gravitational waves during the ringdown phase (post-merger) are still periodic. How can this be so, when the trajectory of each BH must be radially inward once it passes the event horizon?