The Adelphi editions are currently publishing my book entitled General relativity. It is not a popular book intended for the general public, it is a textbook that comes from my notes for the university course of introduction to theory, which I taught for many years, first in the United States and then in France. The course has evolved over time, changing every year as I learned better how to teach, but also as my understanding of Einstein’s amazing theory slowly improved. The book is an introductory, synthetic handbook, it does not want to compete with the excellent powerful textbooks that cover all aspects of theory. Instead, it tries to present in a profound but simple way its conceptual, philosophical, physical and mathematical bases, and to summarize its structure and the most important results: gravitational waves, expansion of the universe, black holes … the extraordinary phenomena foreseen by the theory, whose verification in recent years it has showered Nobel prizes on the research community of “relativists”. I am grateful to Adelphi for the decision to step out of his (albeit vast) familiar territory, and publish a book of this kind. The quality and elegance of Adelphi books is hard to match, and seeing my lessons in this beautiful guise thrills me.
For me, general relativity was a great love. One of those great loves that always accompany us. In the first chapter of my booklet Seven short physics lessons I recounted the moment when, as a university student, I began to understand it, studying it in Calabria on the beach of Condofuri, on a book gnawed by mice. In Condofuri I remained bound by affection and friendship. But the effort to “understand” it was a long journey that never really ended. How to understand a great love, on the other hand. Not because I consider myself a particularly blockhead in these things. But because the theory is a tremendous leap forward in our understanding of the world, one that takes time to fully digest. Einstein, after completing its equations in 1917, returned many times to the meaning of his theory, repeatedly changing his mind about how to understand it. In my opinion, the best version he gives is in a late writing, from the 1950s, in an appendix added to his popular book. Even after his death, discussions on understanding the theory continued. Whether the theory really predicted gravitational waves or not was still a matter of debate in the conferences of the 1960s, and the precise understanding of that amazing prediction that black holes are is even later.
Today we no longer discuss what the theory preaches. The ambiguities have been raised. But there is still discussion on how best to think about it. In summary, general relativity is the discovery that two entities that we believed to be different are actually the same. One is the gravitational field, the little brother of the electric field, which transmits the force of gravity as the electric field transmits the electric force. The other is the space in which we are immersed. Indeed, to be more precise, “spacetime”, which is a bit like the house in which reality lives. When it turns out that two things are actually the same, one can be eliminated. For example, if they introduce us to a gentleman named Antonio de Curtis, and then we discover that it is Totò, we can say: «Ah! But then Antonio de Curtis is in reality nothing but Totò ». But we can also say «ah! But then Totò is none other than Antonio de Curtis ». The same thing happened with general relativity. Many, including Einstein at the beginning, exclaimed «ah! But then the gravitational field is actually spacetime (which curves) ». Someone else, however, prefers to look at it from the opposite point of view: «Ah! But then spacetime, the house in which things happen, is nothing but the gravitational field! ». Among these is Einstein in his more mature reflections. In my opinion this second perspective, perhaps less common, is more far-sighted. Not because the two points of view lead to different predictions. After all, it’s just about names. Whether we call him Antonio de Curtis, or Totò, it’s always about him; that we call it “spacetime” or “gravitational field”, it is however the same entity, which follows the equations we know. But names are associated with powerful intuitive images, names naturally tie in with other ideas, and orient our thinking in one way or another. The great American physicist Richard Feynman wrote that a good scientist keeps in mind equivalent ways to understand the same phenomena, because one among the others will prove to be more effective. My life’s work is to try to extend Einstein’s theory to include the quantum aspects of gravity as well. To do this, it is necessary to take the theory from the right direction. This booklet tries to present the theory faithfully, seen from the verse I ask is the most effective. The last chapter of the book mentions these quantum gravitational phenomena, and some basic ideas to try to understand them.
I hope the book will help students who venture to study this theory amazing, giving them an extra tool to broaden and deepen their conceptual baggage. Perhaps it will also intrigue someone who is not a student, but he feels the fascination of what the Russian physicist Lev Landau has called “the most beautiful of theories”.
Out July 1st. The book and the new series
The new book by Carlo Rovelli, General relativity, is published by Adelphi (pages 163, e 24) and will be in bookstores starting Thursday 1 July. The text was translated by Pietropaolo Frisoni, this is because the lessons of Carlo Rovelli are born as academic texts for an international audience. This volume by Rovelli, with its very elegant new graphic design, will also be the first title of Adelphi’s newly created series, “Science Lessons”, which will have the characteristic of welcoming more rigorous texts in the form of lectures, intended in a particular way. to students and specialists and less informative than the Scientific Library.
June 28, 2021 (change June 28, 2021 | 21:40)
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