On the Origin of Time

Chapter 1

A Paradox

Es könnte sich eine seltsame Analogie ergeben, dass das Okular auch des riesigsten Fernrohrs nicht grösser sein darf, als unser Auge.

A curious correlation may emerge in that the eyepiece of even the biggest telescope cannot be larger than the human eye.

Ludwig Wittgenstein, Vermischte Bemerkungen

The late 1990s were the culmination of a golden decade of discovery in cosmology. Long regarded as a realm of unrestrained speculation, cosmology the science that dares to study the origin, evolution, and fate of the universe as a whole was finally coming of age. Scientists all over the world were buzzing with excitement about spectacular observations from sophisticated satellites and Earth-based instruments that were transforming our picture of the universe beyond recognition. It was as if the universe was speaking to us. These developments posed quite a reality check for theoreticians, who were told to rein in their speculation and flesh out the predictions of their models.

In cosmology we discover the past. Cosmologists are time travelers, and telescopes their time machines. When we look into deep space we look back into deep time, because the light from distant stars and galaxies has traveled millions or even billions of years to reach us. Already in 1927 the Belgian priest-astronomer Georges Lemaître predicted that space, when considered over such long periods of time, expands. But it wasn t until the 1990s that advanced telescope technology made it possible to trace the universe s history of expansion.

This history held some surprises. For example, in 1998 astronomers discovered that the stretching of space had begun to speed up around five billion years ago, even though all known forms of matter attract and should therefore slow down the expansion. Since then, physicists have wondered whether this weird cosmic acceleration is driven by Einstein s cosmological constant, an invisible ether-like dark energy that causes

Thomas Hertog is an internationally renowned cosmologist who was for many years a close collaborator of the late Stephen Hawking. He received his doctorate from the University of Cambridge and is currently professor of theoretical physics at the University of Leuven, where he studies the quantum nature of the big bang. He lives with his wife and their four children in Bousval, Belgium.

[A] wonderful book about Stephen Hawking's Hawking s biggest legacy . Spectator

Truly mind-stretching . . . Immensely immensely rewarding. The Times

Why is our universe the way it is? How did everything begin? How might it end? Thomas Hertog probed these overwhelming questions in collaboration with Stephen Hawking, achieving a privileged perspective into how, struggling against daunting physical odds, Hawking s imprisoned mind yielded astonishing insights even in his later years. This superbly written book offers insight into an extraordinary individual, the creative process generally, and the scope and limits of our current understanding of the cosmos. Lord Martin Rees, Emeritus Professor of Cosmology and Astrophysics, University of Cambridge, and author of Just Six Numbers

Like his mentor and colleague Stephen Hawking, Thomas Hertog has never shied away from being ambitious in theorizing about the universe. This sweeping book provides an accessible overview of both what we know about cosmology and some audacious ideas for moving into the unknown. It is an introduction to Hawking s final theory, but also a glimpse into even grander theories yet to come. Sean Carroll, author of The Biggest Ideas in the Universe: Space, Time, and Motion

Stephen Hawking s final theory is lucidly explained in this splendidly accessible book. Author Thomas Hertog, one of Hawking s closest collaborators, gives us a vivid insight into Hawking as both a brilliant physicist and an astonishingly determined human being. Graham Farmelo, Churchill College, University of Cambridge, and author of The Strangest Man

A beautifully written, thought-provoking account of both the physics and the personalities involved in Hawking s visionary struggle to comprehend the cosmos. Thomas Hertog has provided a fascinating insider s view. Neil Turok, co-author of Endless Universe