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I have heard that when something passes the event-horizon of a black hole nothing can stop it from getting pulled in. Is that true for objects partially past the event-horizon? Would it be possible to attach a camera to a stick or rope, put it inside the event-horizon, take a picture, and pull it back up and look at the picture?

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    $\begingroup$ No - it would require infinite energy to apply sufficient acceleration to the camera to get it to return. $\endgroup$ – adrianmcmenamin Aug 24 '17 at 20:30
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According to the observer holding the rope, the camera would never make it past the event horizon. It would appear to slow down to a standstill just above the horizon (though would effectively disappear because of redshift). At some point the rope would snap, but the camera would still not appear to cross the horizon.

According to an observer with the camera, they would cross the horizon. But if they were lowered slowly, the rope would snap before they got there, since infinite force is needed to "hover" just above the event horizon.

They would then find themselves inexorably falling inwards in the same way that you and I are inexorably drawn into the future and can't revisit the past.

That different observers in different frames have different versions of events is not unusual in relativity.

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  • $\begingroup$ I guess the observer with the rope is burning a lot of fuel to hover just above the EH, they wouldn't have much time if they were in freefall, and they're too close to be in a circular orbit. $\endgroup$ – PM 2Ring Aug 24 '17 at 22:55
  • $\begingroup$ @PM2Ring Nothing is in free fall here. The observer with rope needs to be a long way from the BH. $\endgroup$ – Rob Jeffries Aug 24 '17 at 23:23

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