How sad that Stephen Hawking struggles at interviews, has a flippant comment about women (‘a complete mystery’) widely reported, and lacks consistency in expressing belief or not in time travel via Black Holes/wormholes.
Stephen Hawking’s problem is being no physicist while his mathematics of BHs (black holes) has shaky foundations. In 1970 with Roger Penrose, he constructed an elegant topological argument on the premise of a trapped surface taken from the 1939 solution of Oppenheimer and Snyder. Unfortunately this trapped surface arises from an erroneous fit of inner and outer solutions by O&S and is not a property of the Einstein field equation. Going for topological arguments also overlooked the warning of O&S that it’s impossible for a singularity to develop in a finite time – the slowing of local time in high gravity means a Black Hole never forms.
The Black Hole idea led Hawking to the ‘information loss paradox’ and evaporation of mini-BHs, but never did he address the shaky basis. His predicted ‘Hawking’ radiation depends moreover on uncertain quantum uncertainty. Criticisms and alternative approaches to the Einstein equations are growing in cogency, since Abhas Mitra (1999), Logunov et al. (2006), Marshall (2007), Mitra (2010) and Marshall (2011), with the latter finding an explicit solution for zero-pressure spherical collapse ever more slowly towards a shell of matter.
Though Hawking has spoke of winning the Nobel prize, the contradictions between causal physics and his maths look insuperable.