As scientists look farther and more clearly into space than ever before, this book reveals the greater relevance of general relativity, showing us where it started, where it has led, and where it can still take us.
Oxford Astrophysics Professor and Cosmologist Pedro Ferreira’s new book is a “Biography of the General Relativity Theory”. He has covered Einstein’s conception of the theory, its birth and especially the role of mathematics and the help Einstein got from Marcel Grossman and David Hilbert. This is a Centenary Story as the theory completed a century, Einstein having published it in 1915. Eddington provided the experimental affirmation in 1919 of the theory’s distinctive prediction about deflection of light by the sun.
Hubble’s theory of an expanding universe showed the way forward. Ferreira lucidly explains how the theory has developed. The steps were: black holes, singularity theorems, cosmology and steady state models, the CMB, and the now standard model, with dark matter and dark energy, relation to quantum theory, gravitational waves. A variety of different related topics are covered, the emphasis being on history. General Relativity theory, according to Ferreira, is a highly testable scientific theory.
The mathematical aesthetic of relativity has been underscored by the beautiful demonstrations of its veracity as described by Ferreira. The book tells us what other people did with Einstein’s general theory of relativity after he developed it. The book competently portrays the colourful personalities and exciting discoveries unearthed by general relativity.
It is interesting to note that Arthur Eddington was Einstein’s heir, thoroughly learning the theory and grasping its implications for stellar structure. Ironically he did not dare to take these implications to their logical conclusion. That task was left to a young Indian astrophysicist named Subrahmanyan Chandrasekhar who paved the way toward the discovery of black holes by considering what happens when stars run out of fuel and collapse under gravitational contraction. Unfortunately Eddington rebuked Chandrasekhar’s findings and revealed himself to be much like Einstein, a revolutionary in young age and a reactionary in old age.
The story of black holes is one important thread that the book follows. Chandrasekhar’s ideas were further developed by Lev Landau, Fritz Zwicky and Robert Oppenheimer in the 30s. Oppenheimer’s story is especially interesting since he was the one who theoretically discovered black holes but later showed no interest in general relativity until the end of his life.
Princeton University physicist John Wheeler picked up where Oppenheimer had left off. Wheeler is really the father of modern relativity. In Britain the field was fathered by Dennis Sciama, whose students Roger Penrose and Stephen Hawking led the way in understanding singularities and the Big Bang. Hawking especially forged a very important link between information, relativity, thermodynamics and quantum mechanics through his exploration of what we now call the “black hole information paradox”.
Hawking’s work on singularities leads us to the second major thread of the book – involving the applications of general relativity to the entire universe. Edwin Hubble in 1929 observed the redshifting of galaxies and inaugurated one of the great eras in the exploration of the cosmos. This era culminated in the discovery of dark matter and dark energy and the transformation of cosmology into a precision science, all of which has opened up frontiers undreamt of by Einstein.
Ferreira emphasizes how the grounding of relativity in the real world through the discoveries of quasars, pulsars, neutron stars and black holes helped in lending respectability to the theory. The last part of the book concerns the quest over the last four decades to combine general relativity with quantum mechanics, an effort that was started by Wheeler and his student Bryce DeWitt in the 60s.
The book also highlights the several ways how scientists fell victim to all sorts of biases and narrow-minded preoccupations that prevented them from seeing things as they really are. In some cases, researchers got very attached to the ideas of objects they knew they couldn’t prove existed — or rejected objects suggested by the math when they didn’t fit neatly into certain scientific preconceptions.
Ferreira’s clear explanations offer a wonderful look into a world of those who tackle the hard math that is “the key to understanding the history of the universe, the origin of time, and the evolution of… the cosmos book “the biography of General Relativity”.
P.P. Ramachandran
