# Einleitung von Prof. Sedlmayr

# Einleitung durch Prof. Dr. Erwin Sedlmayr, Technische Universität Berlin

Professor Hawking,

Magnifizenz,

Ladies and Gentlemen,

After the warm welcome by Professor Lenzen, president of the Freie Universität Berlin, I am honored and privileged to introduce to you Professor Stephen Hawking, who will deliver today's "Einstein lecture" on the occasion of the centennial celebration of the annus mirabilis of physics 1905. It is no exaggeration to state that Stephen Hawking is one of the most well-known living scientist - if not the best known - famous not only in the scientific community, but also among the broader public around the world, which is fascinated by Stephen Hawking's unique contribution to the popularization and dissemination of fundamental ideas about the origin and structure of the universe. He has established new theoretical concepts and descriptions, which derive from unusual, new perspectives and provide a deeper insight into the basic physical structures of the universe and its objects, both by trailblazing interpretations of the physical facts and through surprising discoveries. Beyond the scientific community he has been willing to share his exciting scientific findings and visions with the public at large, thus stimulating the public interest and even enhancing the understanding of science.

Probably everyone in this audience is aware of what a singular event the book A Brief History of Time was: For a long time after its appearance in 1988, it topped every nonfiction bestseller list; the German translation of this book is still in print, now in its twenty-fifth edition. Through his inspiring suggestions and explanations Stephen Hawking has not only fascinated millions of readers in all cultures and languages; he has stimulated the astronomy and physics community with extremely fruitful physical concepts and mathematical descriptions, so that his eminent scientific achievements - like those of Albert Einstein - form a glorious cornerstone of contemporary scientific theory and imagination. But more than that, due to his human motives, his visionary will, and his struggles, Stephen Hawking's outstanding scientific achievements have entered into the common body of culture shared by all human beings.

Stephen Hawking's ability to be deeply involved in studies of gravity, cosmology, and fundamental high-energy physics is extraordinary. Throughout his scientific life he has strived for a deeper understanding of cosmic physics with great courage and unique gifts; he is a genuine pioneer at the forefront of the great theories of physics: General Relativity (doubtless the platform of his forty years of work), Quantum Theory (including its most advanced extensions, for example, in attempts to unify supergravity and string theories to obtain a supersymmetric description, as is expected to result from the eleven-dimensional M-theory), and last but not least Thermodynamics. His pioneering work has led him to reveal unexpected fundamental laws of nature (like the formulation of a Black Hole Thermodynamics) and to discover spectacular physical phenomena (like Black Hole evaporation through the Thermal Radiation of Black Holes [1975], now known to every student as Hawking Radiation). These findings have clear and far-reaching consequences for a more profound understanding of the applied theories and the investigated objects, fundamentally altering the established perception and interpretation of pivotal aspects of the physical universe. A closer look at Professor Hawking's main scientific interests over the years discerns four different major phases of his technical work, here roughly summarized:

- General Relativity applied to Cosmology: Topological characterization and exact properties of solutions of Einstein's field equations; perturbation solutions; the singularity theorems, in particular the Hawking-Penrose theorem (1970)
- General Relativity applied to Black Holes: Black Hole uniqueness; Black Hole Thermodynamics and the famous corresponding fundamental thermodynamical theorems, recall the Area Theorem of 1970
- Quantum fields in a Curved Space-Time: Black Hole particle creation (Hawking radiation), Black Hole evaporation, Black Hole temperature; Black hole horizon and quantum information puzzles, for example, the existence of "naked singularities"

Hawking's discovery of Black Hole radiation is one of the most striking in gravitation physics because it reveals a profound interconnection between Quantum Theory, General Relativity, and Thermodynamics in the physics of Black Hole processes, causing Black Holes to be seen as Black Bodies that obey the known laws of equilibrium thermodynamics. - Semiclassical Gravity and Quantum Gravity:

These aspects concern, for example:

- the wave function of the universe and the corresponding quantum state (Wheeler-deWitt equation),
- the revolutionary no-boundary idea of the universe (together with Jim Hartle),
- the subtle discussion of the cosmic inflation scenario,
- most spectacular, the innovative application of a path-integral description of the cosmic prephase evolution by introducing an imaginary "time"-coordinate,
- and, last but not least, his evaluation of, and comments on, the Anthropic Principle.

Today, at the beginning of the new millenium, these findings are considered to be necessary steps toward a more profound and reliable physical understanding of our universe and its existence, thus making Stephen Hawking's eminent ideas and contributions necessary major building blocks of a future cosmic architecture, anticipated by the call of some enthusiastic cosmologists for an ultimate Weltformel.

Professor Hawking's achievements have been acknowledged by many highly prestigious appointments, prizes, and awards:

First his outstanding position:

After his appointment in 1977 as a fellow of Gonville and Caius College, University of Cambridge, Stephen Hawking was named in 1979 to the Lucasian Professorship of Mathematics at the University of Cambridge, perhaps the most prestigious chair available in physics, with such eminent predecessors as Sir Isaac Newton and Paul Dirac.

- 1966: Adams Prize
- 1975: Eddington Medal of the Royal Astronomical Society
- 1978: Albert Einstein Award
- 1985: Gold Medal of the Royal Astronomical Society
- 1988: Wolf Prize in Physics
- 1999: Julius Edgar Lilienfeld Prize of the American Physical Society

Besides prizes and awards, he has received honorary doctorates from many top-rank universities. In 1981 Queen Elizabeth honored Professor Hawking by appointing him "Commander of the British Empire", and in 1989 she awarded him the prestigious title "Companion of Honour".

When Stephen Hawking, who was born in Oxford in 1942, entered the fields of Black Holes and Cosmology in the early nineteen-sixties, neither Black Holes nor Cosmology were considered part of the contemporary astrophysical mainstream, in stark contrast to the situation today. To be sure, there is now no doubt that Black Holes exist in reality, but back then they were widely considered to be mere exotic theoretical solutions relating to equally exotic astronomical mass distributions, without any dramatic astrophysical relevance. Big Bang Cosmology was also a long way from being proved as a hard quantitative science; even in the nineteen-seventies it was regarded, according to Carl Friedrich von Weizsäcker, as basically a kind of myth expressing the current notion scientists have of the beginning of the universe, rather than as a real physical event to be reliably investigated within the competence and validity regime of physical theories.

Things have changed dramatically in the last forty years - in the meantime Black Holes have turned out to be numerous astronomical objects, well observed even in our own galaxy, and also Cosmology seems to be on the verge of developing into a quantitative hard science, at least with regard to its observational status. Nevertheless, there still remains the eternal quest for a convincing scientific answer to the age-old question of the nature of the universe and its coming into being. Thanks to the devoted work of eminent scientists - from Isaac Newton to Albert Einstein and, today, Stephen Hawking - for the first time in history, supported by qualified observations, we mortal beings are in a position to argue reasonably, on the basis of contemporary theoretical concepts, about the existence of the universe and its local and global structure. Hence it is a great pleasure to ask Professor Hawking to give his talk on "The Origin of the Universe".