What would an outside observer see when a clock falls into an event horizon?

[KevinOT]

I’ve been trying to wrap my head around the concept of gravitational time dilation near a black hole’s event horizon. If an observer in a stable orbit just outside it could somehow watch a clock falling in, would the clock’s signal just redshift into undetectability before it actually crosses, or would it appear to freeze completely? I’m struggling to visualize the practical limits of observation from that perspective.

[JeffreyL]

From memory you never actually see the clock cross the edge if you are in a nearby stable orbit. The ticks slow down a lot and the light gets redder and fainter until it vanishes from view.

[Scott90]

I tried to picture it as a thought experiment and the gravitational time dilation would make each tick take longer for you to see and the signal shifts to lower energy.

[Scarlett71]

A rough mental calc says that as the clock nears the horizon the redshift grows without bound so the observed tick interval becomes huge and the light arrives more sparsely.

[Jerry_W]

The snag is you cannot have a stable orbit immediately near the edge around a non rotating black hole. The last stable orbit sits at six times the mass in geometric units.

[Lily.T]

I once played with a toy model where the emitted tick rate stays fixed in the clock frame but the observer records longer gaps. It felt right at first but I kept tripping over Doppler shifts from the orbital motion.

[Ella43]

Would you say the core issue is detection limits more than what the clock is actually doing, like could you even notice it with real instruments before it fades away?