N.C. Wickramasinghe – författare

Light scattering and absorption by small homogeneous particles can be worked-out exactly for spheres and infinite cylinders. Homogeneous particles of irregular shapes, when averaged with respect to rotation, have effects that can in general be well-approximated by reference to results for these two idealised cases. Likewise, small inhomogeneous particles have effects similar to homogeneous particles of the same average refractive index. Thus most problems can be solved to a satisfactory approximation by reference to the exact solutions for spheres and cylinders, which are fully stated here in the early part of the book. The sum of scattering and absorption, the extinction, is too large to be explained by inorganic materials, provided element abundances in the interstellar medium are not appreciably greater than solar, H 0 and NH3 being essentially excluded in the 2 general medium, otherwise very strong absorptions near 3p,m would be observed which they are not. A well-marked extinction maximum in the ultraviolet near 2200A has also not been explained satisfactorily by inorganic materials. Accurately formed graphite spheres with radii close to O.02p,m could conceivably provide an explanation of this ultraviolet feature but no convincing laboratory preparation of such spheres has ever been achieved.

Two of the pioneers of the modern version of panspermia - the theory that comets disperse microbial life throughout the cosmos - trace the development of their ideas through a sequence of key papers. A logical progression of thought is shown to lead up to the currently accepted viewpoint that at least the biochemical building blocks of life must have derived from comets. The authors go further, however, to argue that not just the chemicals of life, but fully-fledged microbial cells have an origin that is external to the Earth. Such a theory of cosmic life, once established, would have profound scientific as well as sociological implications.

This volume contains papers presented at an international conference to celebrate Fred Hoyle's contributions to astronomy, astrophysics and astrobiology and - more generally - to humanity and culture. The contributed articles highlight the important aspects of his scientific life and show how much of an example and inspiration he has been for over three generations in the 20th century. There are few people of whom it could be said they changed the way we perceive the world. Galileo Galilei, Nicholas Copernicus and Isaac Newton were amongst these. The inclusion of Fred Hoyle in this elite group may be contentious at the moment for the reason that in challenging the most cherished of Holy Grails in science he unwittingly offended many. But once the dust has settled over the many disputes that were raised and in the fullness of time there can be little doubt that Fred Hoyle will be ranked alongside these figures of history. Hoyle perceived science with an indomitable passion and an obsessive desire to find the truth wherever it lay.His singleness of purpose in this great mission and his deep suspicion of orthodoxy, his powerful intellect and imagination set him apart from most of his contemporaries in the last century. This volume includes papers presented at a commemorative conference held in Cardiff in June 2002. The material divides naturally into several sections: "Personal Reminiscences", "Stellar Structure" and "Evolution", "Cosmology", "Interstellar Matter", "Comets" and finally "Panspermia". Each article pays its own tribute to Fred Hoyle for his inspiration and guidance that led to major breakthroughs in astrophysics and space science throughout the 20th century.

This volume contains papers presented at an international conference to celebrate Fred Hoyle's monumental contributions to astronomy, astrophysics and astrobiology and more generally to humanity and culture. The contributed articles highlight the important aspects of his scientific life and show how much of an example and inspiration he has been for over three generations in the 20th century.

Over the past decade the study of the formation and properties of interstellar grains has assumed a growing importance, going much beyond what might have been guessed only a few years ago. It has come to be understood that grains playa role in processes other than the simple absorption and scattering of starlight, which was all that the astronomers of a generation aga considered to be their relevance. Grains indeed playa critical role in controlling the temperature, composition, and states of aggregation of the whole interstellar medium. Among the still mysterious problems is the origin of the vast clouds of obscuring material that is observed in radiogalaxies like NGC 5128 and M 82, which may weIl be associated with the explosions of very massive objects. It is safe to say that from this growing field of study much still remains to be dis­ covered. The topics discussed in this volume will make clear to the reader the range and versatility of the subjects. F. HOYLE FOREWORD by THE PRINCIPAL The Symposium on Solid State Astrophysics held in July 1974 brought to University College Cardiff a large and very distinguished gathering of astronomers. It was the first time that such a collection of scholars, absorbed with the problem of the systems of outer space, had collected together in Wales, and so provided a splendid spring­ board for the researches of the newly founded group of astronomers in the Department of Applied Mathematics and Astronomy at University College.

Light scattering and absorption by small homogeneous particles can be worked-out exactly for spheres and infinite cylinders. Homogeneous particles of irregular shapes, when averaged with respect to rotation, have effects that can in general be well-approximated by reference to results for these two idealised cases. Likewise, small inhomogeneous particles have effects similar to homogeneous particles of the same average refractive index. Thus most problems can be solved to a satisfactory approximation by reference to the exact solutions for spheres and cylinders, which are fully stated here in the early part of the book. The sum of scattering and absorption, the extinction, is too large to be explained by inorganic materials, provided element abundances in the interstellar medium are not appreciably greater than solar, H 0 and NH3 being essentially excluded in the 2 general medium, otherwise very strong absorptions near 3p,m would be observed which they are not. A well-marked extinction maximum in the ultraviolet near 2200A has also not been explained satisfactorily by inorganic materials. Accurately formed graphite spheres with radii close to O.02p,m could conceivably provide an explanation of this ultraviolet feature but no convincing laboratory preparation of such spheres has ever been achieved.