Undoubtedly black holes are one of the most intriguing phenomena in our universe. The current interpretation of them, being a point mass that’s infinitely dense, is quite modern being only formalized some time back in the 1950s although the scientific roots can be traced back a bit further than that. Still they’re far from being a solved problem space as, like all things that use the word “infinite” in some capacity, their behaviour is a little strange especially when you try to explain them using different theories for how the universe works. To us laypeople we tend to be rooted in the general relativity explanation, however once you step into the world of quantum mechanics suddenly they start behaving differently creating quite the paradox.
In the world of general relativity passing across the event horizon, the point at which nothing (not even light) can escape, would be a somewhat peaceful affair. Since you would be in complete free fall at the time you wouldn’t experience a sudden jolt or anything that would indicate to you that this had happened (which makes black holes nightmare material for someone like me who has aspirations for space travel). After a while though you’d start to feel rather uncomfortable as the difference between the gravity at your head and feet became vastly different, eventually leading to a rather untimely demise at the hands of what has been dubbed spaghettification. However if you approach the same problem from the view of quantum mechanics you might not even get a chance to experience that as the world past the black hole’s event horizon is something vastly different.
The current hypothesis say that instead of the event horizon being a peaceful transition (although usually even getting to the event horizon would be quite nasty thanks to the accretion disks they usually sport) there instead exists a violent firewall of energy, ready to tear anything apart that crosses that horizon. Whilst the mechanics of this are well above my understanding it appears to be a quirk of Hawking Radiation, the process by which black holes “evaporate” over time. This evaporation occurs via entangled particles, one which leaves the black hole and another that falls back in. However this must mean that the entanglement is broken at some point which would release a lot of energy. This has led to a paradox which means that we have to either modify or abandon certain principles in physics, something which scientists don’t really like to do unless there’s a good reason to.
Hawking has recently weighed in on the topic through a paper on ArXiv which was then famously misinterpreted as him saying that there were no black holes at all. What he was actually saying was that there were no black holes in the traditional sense that there were distinct event horizons which, when passed, would not allow anything to escape. Instead Hawking has propose apparent horizons which are temporary artefacts, shifting around the black hole. This would then allow information to escape without necessitating the quantum firewall, preserving the more peaceful theory.
The new theory hasn’t been hit with resounding approval however as it raises almost as many questions as it answers. I’ll admit its quite intriguing, definitely worthy of further research, but with so many fundamental changes to the model of how black holes operate it’s hard to take it at face value. Still the mere fact that this has caused such ripples, even outside the scientific community, shows just how important this is to the wider world of physics.