Book Reviewed - Black Holes: The Key to Understanding the Universe by Brian Cox and Jeff Forshaw

The cosmos where the laws of physics breakdown A black hole is a region in spacetime where gravity is so strong that nothing, not even light, can escape from it. Black holes form when massive stars collapse under their own gravity at the end of their life cycle, and supermassive black holes are also formed at the center of a galaxy. The boundary surrounding a black hole is called the event horizon beyond which no information or matter can escape. This book offers a brief introduction to the physics of a black hole; the entropy and black holes, Hawking radiation formed at the event horizon that has only temperature but no information about the matter that fell into the black hole resulting in the black hole information paradox. The black hole is described as a hologram where the information about the three-dimensional black hole is represented by the two-dimensional surface. The entanglement entropy and the Page curve are concepts that arise from the quantum information theory in the context of black hole physics and the holographic principle. Initially, the black hole has low entropy, but as it absorbs more matter and radiation, its entropy increases. According to the Page curve, the entanglement entropy of the Hawking radiation (the particles emitted by the black hole due to quantum effects near the event horizon) starts low, then increases as more particles are emitted, and eventually decreases as the black hole evaporates completely. The Page curve illustrates this evolution of entanglement entropy over time and provides insights into the information paradox and the fate of information that falls into a black hole. Another interesting feature of the black hole is the principle of complementarity that reconciles two descriptions of a spaceship near the event horizon by suggesting that they are valid from different perspectives. From an observer on Earth, the classical description of a black hole as an object with an event horizon holds true. This observer sees the black hole as a region of spacetime with specific properties described by general relativity. But from an infalling astronaut’s perspective, quantum effects become significant near the event horizon. This observer would experience the effects of Hawking radiation and might not perceive the event horizon as a sharp boundary but rather as a gradual transition. The author expresses two misconceptions suggesting that the gravitational wave detection helps understand the worm holes. This is a misunderstanding because it does not directly illustrate the existence of wormholes. Gravitational waves are mere ripples in the fabric of spacetime that propagate outward from the source, typically caused by the acceleration of massive objects such as merging black holes or neutron stars. Wormholes are hypothetical features of spacetime that are predicted by certain solutions of Einstein's field equations in general relativity. They are essentially shortcuts through spacetime that could potentially connect two distant points of our universe. The author expresses the hope that quantum computers may help understand the physics of black holes. This is an overestimate since, the quantum computers only help in simulating the behavior of black holes which are complex to study with classical computers due to their extreme gravitational effects and the necessity of quantum mechanical descriptions at certain scales. The author could have discussed the philosophical implications of black hole physics and information paradox. The Vedanta philosophy of Hinduism shares intriguing parallel with theoretical physics in their exploration of unity, multiplicity, illusion, and the nature of reality. They offer insights into profound questions about the nature of existence.