What Happens at the Event Horizon? | Space Time | PBS Digital Studios
Why Hacker News recommends it
Commenters call it a short, clean, visual explanation of the infalling-particle question and of Penrose diagrams.
What it is
PBS Space Time explains what happens as you approach and cross a black hole's event horizon, using Penrose diagrams and light cones as the tool for understanding spacetime there.
Recommended by 3 HN commenters across 3 different months, 2019 to 2025.
What Hacker News said
Strong rec speakeron · 2019-01 · on “Strangeness of Black Holes”
The particle goes through the event horizon in finite time according to its own clock (and will then hit the singularity in finite term however it tries to travel). Think of the view of it by an external observer as being 'frozen' at the event horizon as kind of optical illusion caused by the extreme warping of spacetime. For a non-evaporating black hole (as described by general relativity), the 'last' photon coming off it will indeed be at infinity (or with infinite redshift). If (when) the black hole evaporates, the external observer will see that and of course there will be no more photons from the infalling particle. These two different views are hard to reconcile from our human perspect
Recommends me_me_me · 2020-10 · on “The Nobel Prize in Physics 2020”
[this video] I hope it helps. I think this is the cleanest explanation with actual visual representation. Edit: Sorry this one is even better. How Time Becomes Space Inside a Black Hole | Space Time [LINK]
Recommends neom · 2021-05 · on “Physicists identify the engine powering black hole energy beams”
PBS Space Time to the rescue: What Happens at the Event Horizon? - [this video] What’s On The Other Side Of A Black Hole? - [LINK] How Time Becomes Space Inside a Black Hole - [LINK] The Black Hole Information Paradox - [LINK]
Cites willis936 · 2025-05 · on “Universe expected to decay in 10⁷⁸ years, much sooner than previously thought”
A fun tool to think around such things are Penrose diagrams. Personally I'm a little dubious of strong claims of what will happen in the distant future since we have such incomplete models of physics today. It takes GUTs to predict the future. [this video]