Homer speaks of lightning bolts after which 'a grim reek of sulphur bursts forth' and the air was '?lled with reeking brimstone'. (Homer 3000 BC). The odour was not actually the smell of sulphur dioxide associated with burning sulphur, but rather was the ?rst recorded detection of the presence of another strong odour, that of ozone (O ) in Earth's atmosphere. These molecules were formed by the passage of 3 lightning through the air, created by splitting the abundant molecular oxygen (O ) 2 molecules into two, followed by the addition of each of the free O atoms to another O to form the triatomic product. In fact, most of the ozone molecules present 2 in the atmosphere at any time have been made by this same two-step splitti- plus-combination process, although the initiating cause usually begins with very energetic solar ultraviolet (UV) radiation rather than lightning. Many thousands of years later, the modern history of ozone began with its synthesis in the laboratory of H. F. Schonbein in 1840 (Nolte 1999), although the positive con?rmation of its three-oxygen atom chemical formula came along sometime later. Scienti?c interest in high-altitude stratospheric ozone dates back to 1881 when Hartley measured the spectrum of ozone in the laboratory and found that its ability to absorb UV light extended only to 293nm at the long wavelength end (Hartley 1881a).

This book provides an in-depth coverage of modern research on dynamical systems. The first part discusses stellar dynamics, integrable systems, the transition to chaos and instabilities in stellar dynamics as well as the dynamics of spiral galaxies. Models are given and compared with observations. The second part is devoted to the direct method of N-body simulations, to gas dynamics simulations and to galaxy formation.
Special care is taken to give to a pedagogical presentation of the material which makes this a unique text well suited for graduate courses in astrophysics.

The three years since the Brighton General Assembly have been the most active period in the history of the Union. 33 IAU Symposia and Colloquia, the first Regional Meeting under the Auspices of the IAU, several co-sponsored Meetings and many other special projects. All this culminating with two General Assemblies in two opposite parts of the Earth, Australia and Poland. At the same time the membership of the Union rose to 3200, the number of Commissions to 40, the number of adhering countries to 47. The present Volume gives a general picture of the Union's recent activity. It contains the report of the Executive Committee, the report of the General Assembly, including the Commissions, Meetings, a short report on the Extraordinary General Assembly and an Appendix with the Members and Commissions of the IAU and the approved names of Lunar and Martian features. I take this opportunity to thank all our collaborators, members of the Executive Committee, Presidents of Commissions, Chairmen of Specific Projects, IAU Secrt;taries and all the Members of the IA U for their contribution to keep our Union a living body of active scientists and a big inter national family. G. CoNTOPOULOS General Secretary CONTENTS Page No."

The idea of the organization of a Symposium on Spiral Structure came at a special meeting of Commission 33 on Spiral Structure during the 12th General Assembly of the IAU in Prague, 1967. So much interest was shown during this meeting that one of us proposed a special Symposium on the 'Spiral Structure of Our Galaxy' for 1969. The response was immediate and it was finally agreed upon holding the Symposium in Basel, a center of galactic research in the center of Europe. During the next months a special 'List of Problems', related to this Symposium, was sent to many prospective participants by the president of Commission 33. This stimulated an increase of interest in problems of galactic spiral structure and a con centrated effort on some problems. The organizing Committee of the Symposium was composed of Drs. L. Woltjer (president), W. Becker, A. Blaauw, B. J. Bok, G. Contopoulos, F. J. Kerr, C. C. Lin, S. W. McCuskey and S. B. Pikel'ner. Most of the work for the organization of the Symposium was carried by Dr. L. W oltjer. The Local Committee, composed of Drs. W. Becker, U. W. Steinlin, R. P. Fenkart, and G. A. Tammann, made every effort to secure the success of the Symposium. Most of the credit goes to Dr. Steinlin. The Symposium was supported financially by the IAU and by the Swiss National Science Foundation. The meetings took place at the University of Basel, which provided also secretarial help and many other facilities."

The year 1973 marked the highest peak of IAU activity up to now. Besides the Gen eral Assembly in Sydney, and the Extraordinary General Assembly in Poland, there were held eleven IAU Symposia and one Colloquium. Several IAU Publications cover this activity. The Proceedings of the Symposia are published in separate Volumes, while the Transactions of the General Assembly and of the Extraordinary General Assembly contain short reports of the Commission meetings, the administrative sessions, and the opening ceremonies. The present Volume covers some of the scientific Highlights of the General As sembly and of the Extraordinary General Assembly. It contains five Invited Dis courses given in Sydney and Poland, some selected papers, and the Joint Discussions at the General Assembly of Sydney. Of course, there were many more papers of special interest presented in Sydney that could not be included in this Volume. Their titles can be seen in the reports of the various Commissions. It is regrettable that the Invited Discourses of C. H. Townes (Interstellar Molecules) and F. J. Low (Infrared Astronomy) were not submitted for publication. Also only five papers or abstracts of the Joint Discussion on the 'Origins of the Moon and Satellites' have been available. Despite these minor shortcomings, I believe that the present Volume is faithful to its title: it gives a substantial part of the Highlights of Astronomy in 1973.

The conference Chaos in Astronomy was held in Athens from 17 to 20 September 2007 and was dedicated to the memory of Nikos Voglis, who was directoroftheResearchCenterforAstronomyoftheAcademyofAthensuntil his death on 9 February 2007. It was attended by 73 registered participants coming from 18 di?erent countries. A total of 40 oral papers were delivered including a conference summary. Furthermore 16 posters were presented. The conference was the main event in a series of talks, public lectures and d- cussion meetings about "Chaos in Astronomy" that have taken place at the Research Center for Astronomy. We underline three special talks that have been given by D. Kazanas (NASA-Goddard Space Flight Center), D. Lynden- Bell (Cambridge, UK) and C. Tsallis (Brazilian Academy of Science). The main sponsor of the conference was the "Alexander S. Onassis" Fo- dation. In addition the conference has been supported by the General S- retariat for Research and Technology, the National Observatory of Athens, and the Hellenic Ministry of Culture. We are grateful to all sponsors for their generosity. We also express our gratitude to the Academy of Athens and to the - rectorship of the Biomedical Research Foundation, where the conference took place.

Homer speaks of lightning bolts after which 'a grim reek of sulphur bursts forth' and the air was '?lled with reeking brimstone'. (Homer 3000 BC). The odour was not actually the smell of sulphur dioxide associated with burning sulphur, but rather was the ?rst recorded detection of the presence of another strong odour, that of ozone (O ) in Earth's atmosphere. These molecules were formed by the passage of 3 lightning through the air, created by splitting the abundant molecular oxygen (O ) 2 molecules into two, followed by the addition of each of the free O atoms to another O to form the triatomic product. In fact, most of the ozone molecules present 2 in the atmosphere at any time have been made by this same two-step splitti- plus-combination process, although the initiating cause usually begins with very energetic solar ultraviolet (UV) radiation rather than lightning. Many thousands of years later, the modern history of ozone began with its synthesis in the laboratory of H. F. Schonbein in 1840 (Nolte 1999), although the positive con?rmation of its three-oxygen atom chemical formula came along sometime later. Scienti?c interest in high-altitude stratospheric ozone dates back to 1881 when Hartley measured the spectrum of ozone in the laboratory and found that its ability to absorb UV light extended only to 293nm at the long wavelength end (Hartley 1881a).

The three years since the Brighton General Assembly have been the most active period in the history of the Union. 33 IAU Symposia and Colloquia, the first Regional Meeting under the Auspices of the IAU, several co-sponsored Meetings and many other special projects. All this culminating with two General Assemblies in two opposite parts of the Earth, Australia and Poland. At the same time the membership of the Union rose to 3200, the number of Commissions to 40, the number of adhering countries to 47. The present Volume gives a general picture of the Union's recent activity. It contains the report of the Executive Committee, the report of the General Assembly, including the Commissions, Meetings, a short report on the Extraordinary General Assembly and an Appendix with the Members and Commissions of the IAU and the approved names of Lunar and Martian features. I take this opportunity to thank all our collaborators, members of the Executive Committee, Presidents of Commissions, Chairmen of Specific Projects, IAU Secrt;taries and all the Members of the IA U for their contribution to keep our Union a living body of active scientists and a big inter national family. G. CoNTOPOULOS General Secretary CONTENTS Page No."

The conference Chaos in Astronomy was held in Athens from 17 to 20 September 2007 and was dedicated to the memory of Nikos Voglis, who was directoroftheResearchCenterforAstronomyoftheAcademyofAthensuntil his death on 9 February 2007. It was attended by 73 registered participants coming from 18 di?erent countries. A total of 40 oral papers were delivered including a conference summary. Furthermore 16 posters were presented. The conference was the main event in a series of talks, public lectures and d- cussion meetings about "Chaos in Astronomy" that have taken place at the Research Center for Astronomy. We underline three special talks that have been given by D. Kazanas (NASA-Goddard Space Flight Center), D. Lynden- Bell (Cambridge, UK) and C. Tsallis (Brazilian Academy of Science). The main sponsor of the conference was the "Alexander S. Onassis" Fo- dation. In addition the conference has been supported by the General S- retariat for Research and Technology, the National Observatory of Athens, and the Hellenic Ministry of Culture. We are grateful to all sponsors for their generosity. We also express our gratitude to the Academy of Athens and to the - rectorship of the Biomedical Research Foundation, where the conference took place.