M.J. Valtonen – författare

th Coinciding with the 300 anniversary of the publication of Newton's Principia The International Astronomical Union organized the colloquium No. 96 "The Few Body Problem" in Turku, Finland, June 14.-19.1987. It provided an opportunity to review the progress in the very field which caused Newton a headache, as Victor Szebehely reminded the audience in his introductory remarks. It is a measure of the difficulty and complication of the few body problem that even after 300 years so many aspects of the problem are still unsolved. To quote Szebehely again, "Sir Isaac established the rules, Poincare presented the challenges". Many of these challenges are reviewed in the present proceedings. The gravitational few body problem cuts across the borders of established disciplines. The participants of the colloquium came from departments as different as Aerospace Engineering, Astronomy, Theoretical Physics, Physics, Mathematics, Applied Mathematics, Computer Science, Planetology, Geodesy, Celestial Mechanics and Space Science. The few body problem is a problem of practical significance in many fields and the main aim of the colloquium was to bring together people with research interests in this area, many of whom normally attend different conferences.

Planet Earth is part of our Galactic environment, not just the product of it, and it is still today influenced by phenomena related to Galactic forces. Specifically, our planet is affected by its near environment, in particular the small bodies in the Solar System. This book reviews the processes which cause the collisions of these small bodies with the Earth as well as the consequences of such collisions. The various articles take the reader through the Galaxy-Solar System connection to the orbital dynamics of the small bodies and to their number and distribution in near-Earth space. The hazards of the impacts of small bodies on Earth are evaluated, and the geophysical records of such impacts are discussed. The book takes the reader to the forefront of research on both impact cratering and the origin and evolution of small bodies in the Solar System. Thus it brings together two subjects, geophysics and astronomy, which are usually discussed in separate volumes but are closely knit together in this particular area of research.