Black hole singularity is a surface not a point
General relativity predicts that the “singularity” inside a black hole is not a literal point in space but a spacelike surface in time that every infalling path must end on, more like an unavoidable future moment than a physical location. Commenters unpack how misleading popular explanations can be—especially claims that space and time “swap” at the event horizon—and stress that many paradoxes arise from particular coordinate choices rather than physical effects. The conversation also touches on rotating (Kerr) black holes, quantum gravity, and why singularities signal the limits of our current theories rather than well-understood physical objects.
Scope of the Paper and How Novel It Is
- Several commenters stress the paper is mostly a clarification of standard GR, not a new breakthrough.
- Others argue it still adds value by emphasizing rarely-highlighted viewpoints on singularities.
- There is debate over how “well-defined” singularities are in GR; some say textbook theory is clear, others point to references stating definitions are incomplete.
Singularity as Surface in Time vs Point in Space
- Many comments emphasize that, in the Schwarzschild solution, the singularity is spacelike: more like a “moment in time” you inevitably hit, not a location you can navigate around.
- Inside the horizon, moving “toward the singularity” is likened to moving toward the future: you can’t choose not to.
- Some push back on loose phrases like “space and time swap,” calling them coordinate artifacts and misleading shorthand.
Coordinates, Event Horizons, and Diagrams
- Multiple posts highlight that weird behaviors at the event horizon in Schwarzschild coordinates are just coordinate singularities.
- Alternatives like Kruskal–Szekeres and Eddington–Finkelstein coordinates, plus Penrose diagrams, are cited as better for visualizing causal structure and seeing that nothing special happens physically at the horizon.
- There is confusion and correction around whether the singularity’s “being in your future” is a real invariant property or just coordinate-dependent; one side strongly insists it is invariant.
Quantum Gravity, Unitarity, and Alternatives
- Singularity presence is often taken as a sign GR is incomplete; quantum gravity is expected to resolve it, but no confirmed theory exists.
- Black hole singularities create problems like breaking unitarity in quantum mechanics.
- Some mention alternative pictures (e.g., fuzzballs, “no interior,” naked singularities), but all are presented as speculative or problematic.
Misconceptions, Intuition, and Popular Explanations
- Common pop-sci narratives (pointlike singularities, “swapping” of space and time) are criticized as oversimplified or wrong.
- Several commenters argue everyday intuition and “common sense” are unreliable for black holes and quantum phenomena.
- Various analogies (road trips, balloons, one-way doors) are suggested to convey “region from which not even light escapes” without heavy math.