Black holes are mysterious objects. Predicted by Einstein's theory of relativity, their gravity is so strong that nothing, not even light, can escape them. The book by the astrophysicist Luciano Rezzolla is dedicated to this irresistible attraction of gravity. In general, black holes can arise when massive objects collapse under the influence of their own gravity - an insight that we owe to a work by Roger Penrose from 1965, who won the Nobel Prize in Physics 55 years later. We now know that our universe is populated by numerous black holes, with masses either in the range of three to a few dozen solar masses (stellar black holes) or in the range of millions and billions of solar masses (supermassive black holes).The latter lurk in the center of almost all galaxies, including our own Milky Way.
The author, who has been a professor at the Goethe University in Frankfurt since 2013, is involved in researching black holes himself. In particular, he is a member of the Event Horizon Telescope (EHT) project, a joint project of international institutions that aims to depict the “shadow” of a black hole that is created when radiation is swallowed by the object or when it is bizarre is distracted. In fact, this is radio radiation that is observed by eight radio telescopes distributed around the earth in order to achieve the highest possible angular resolution. The first image of its kind - the shadow of the black hole at the center of the elliptical galaxy Messier 87 (M87) - was released in April 2019 and has achieved cult status on social media.The financial support from the European Research Council, which Rezzolla was able to win together with his colleagues Heino Falcke (Nijmegen) and Michael Kramer (Bonn) in 2013, was decisive for the project.
Whoever rushes in can no longer escape
The author of a non-fiction book on such subjects is usually faced with a dilemma. If it is too easy to read, there is a risk that the content will be more about banal anecdotes around the researchers involved than about the actual science. If he insists too much on precision and completeness, there is a risk of getting tangled up in the technical jargon. Fortunately for the reader, Rezzolla has succeeded in striking a balance between these extremes. He has written a book that is easy to read, but also does not shy away from mathematical formulas, where they really help. The author not only provides a competent introduction to the fundamentals of the field, but also provides a feeling for how scientific work on these highly complex topics is carried out in practice.
According to Einstein's theory, gravity is nothing more than the geometry of a four-dimensional space-time.
Hardly anywhere is this as clear as with a black hole.
This corresponds to a matter-free area of space-time, which is causally decoupled from the areas in which external observers are.
If such an observer is daring enough to plunge into a black hole, there is no more escape, for the simple reason that inside space behaves like time and a reversal in time is simply impossible.
The peculiar properties of space and time are hidden behind the irresistible attraction of gravity.