5 HN users recommended this explainer3 months2016–2021score 3.5
Years with an HN recommendation, 2007–2026
HN commenters recommend it as an accessible but deep explanation of black holes that corrects popular misconceptions.
A PBS Space Time episode asking what black holes really are and whether events can happen inside them. It covers event horizons, time dilation and common misconceptions about black holes.
“This is mind blowing...shatters my misconception of blackholes” (HN, 2018)
There is a fascinating PBS Space Time video[1] about black holes that questions the very existence of whatever is "inside" a black hole. They point out that as you approach a black hole, your proper time is advancing slower and slower when compared to an observer located far away from the black hole (like us, on Earth). That means that from the point of view of this far observer, nothing happens inside a black hole until an infinite amount of time. In other words, what is inside a black hole is separated from us not by a space-like frontier, but a time-like one. Events behind the event horizon are postponed to "the end of times". Does it even make sense to say that those events exist, then? Are they any more real than fairy tales or mathematical equations? If not, we can make any speculation we want, including the existence of alien civilizations. 1. [this video]
Questions whether events inside black holes exist at all
A better way of thinking about the event horizon is that it is the boundary beyond which events happening cannot be assigned a 'when' in our universe - i.e. the object falling 'in' to the black hole is never seen to pass this horizon, but to the object it seems that they do, however those events happen to it after an infinite time in our universe, i.e. never, due to time dilation. The contents of a black hole are the events that occur outside/after our universe relative to that boundary. I found these explanations on an awesome PBS youtube video [0] about black holes and space-time. 0. [this video]
PBS Spacetime is a great series, and delves deep enough for interested layman as well as practitioners to be interested. I find the videos really good. Here is a link to one of many on black holes. [this video]
Accessible yet deep black hole physics from PBS Space Time
You talk about "the singularity" as if it exists. For all we know, that could be a mathematical fiction due to our limited understanding. The Event Horizon as we currently understand it might as well be the demarcation to a separate universe. We have no access to any information from the events beyond it. [this video]
I don’t fully understand it, but I believe the way to think about it is that: we never “see” something fall into a black hole. But the photons from the “last moment we see” get so redshifted they’re essentially invisible. Therefore from a reasonable distance it “looks” like the object disappeared and the event horizon grew in size. Here’s a video, he talks about the redshift around the 8 minute mark. [this video]
Explains redshift of infalling objects near the horizon
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