Black of holes: the end of the universe? by John Taylor was the first book I bought with my hard-earned money from a low-paid newspaper run. It was 1974, I was 11 years old. It was the subtitle that caught my attention, because I had never heard of black holes. At the time, these mysterious cosmic objects were only a theoretical possibility, but half a century later we have ample evidence that they actually exist. After writing bestsellers on quantum mechanics, time and the nature of reality, Italian physicist Carlo Rovelli brings all three together in his latest book, taking us on a journey deep inside a black hole. An accomplished storyteller, Rovelli begins this mind-boggling adventure by explaining how they are formed.
Sooner or later, stars run out of fuel and stop shining. At this point, their own gravity causes them to compress. Our Sun will eventually become what is called a white dwarf, reducing its mass to the size of Earth. However, some stars are so massive, with such strong gravity, that collapse continues until they are compressed to a point called the singularity. This is where the known laws of physics break down. A black hole is a singularity surrounded by its event horizon, a one-way boundary protecting it from the rest of the universe. Anything that gets too close will not be able to escape and will be pulled into the hole and crushed. This is the conventional view, which Rovelli challenges in his short, utterly engaging and dense narrative that you may need to read more than once.
According to Einstein’s theory of general relativity, the interior of a black hole is shaped like a funnel that becomes longer and narrower over time. At the bottom is the remains of the star that gave birth to the black hole. Rovelli argues that the collapsing star has not reached the bottom but continues to fall due to the effect of gravity on time. And as space and time dissolve into a cloud of quantum probabilities, a black hole becomes a white hole, with time reversed. White holes, Rovelli explains, are how a black hole would appear if we could film it and run the video backwards.
Confused? Well, that’s hard enough to explain in a book, let alone in a review. Even some professionals struggle to fully grasp these incredibly counterintuitive concepts. And even though Rovelli avoids the technical jargon of the physicist’s profession, he gives the reader the right to skip a few paragraphs or pages here and there. Fortunately, Einstein himself leaves us alone, at least a little: “Imagination is more important than knowledge,” he once wrote. None of this is to say that you finish White Holes any less knowledgeable than you started it – and Rovelli certainly does an excellent job of conveying the wonder and strangeness of the universe. In the end, however, you may feel justified in pouring yourself a drink and savoring the feeling of getting your mind back on track.