Carlo Rovelli

When commenting on author Rovelli's ultra-popular-level 2016 book _Seven Brief Lessons on Physics_, I drew attention to his contention, based on the theory of loop quantum gravity, that "a black hole is a rebounding star seen in extreme slow motion". This latest little gem of a volume expands on that claim. It pictures the interior of a stellar black hole as a long and narrow funnel that keeps lengthening and narrowing until it becomes a singular line. At that point of maximum compression, the black hole is a "Planck star" and is capable of undergoing a "quantum leap" (tunneling) into a white hole. In the interior of the white hole, the singular line becomes a funnel that keeps shortening and widening until there is no more hole. The length of time between initial collapse and final dissipation: mere instants from an interior perspective but billions of years from a distantly exterior perspective. Thermodynamic effects such as Hawking radiation imply that the emergent final "body" is not star-sized but sub-microscopically small. Some readers will be charmed by the book's recurring quotations from Dante Alighieri's works. Many will like its capitalization-free musings such as "we have access only to perspectives. reality is perhaps nothing other than perspectives. there is no absolute. ..." (p 30)… (more)