Ask Astro: If time stops for an object falling into a black hole, how can LIGO see black holes colliding?

I’ve always understood that, according to general relativity, a distant observer of someone who falls into a black hole would see them slow down, then come to a virtual stop at the event horizon and become “smeared.” So how is it that LIGO can record two black holes combining in milliseconds?

Kevin Hooper

Calgary, Alberta

Let’s consider GW150914, the first binary black hole merger detected via gravitational waves. The final black hole formed during the merger is