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.

Living material contains about twenty different sorts of atom combined into a set of relatively simple molecules. Astrobiologists tend to believe that abiotic mater­ ial will give rise to life in any place where these molecules exist in appreciable abundances and where physical conditions approximate to those occurring here on Earth. We think this popular view is wrong, for it is not the existence of the building blocks of life that is crucial but the exceedingly complicated structures in which they are arranged in living forms. The probability of arriving at biologically significant arrangements is so very small that only by calling on the resources of the whole universe does there seem to be any possibility of life originating, a conclusion that requires life on the Earth to be a minute component of a universal system. Some think that the hugely improbable transition from non-living to living mat­ ter can be achieved by dividing the transition into many small steps, calling on a so-called 'evolutionary' process to bridge the small steps one by one. This claim turns on semantic arguments which seek to replace the probability for the whole chain by the sum of the individual probabilities of the many steps, instead of by their product. This is an error well known to those bookies who are accustomed to taking bets on the stacking of horse races. But we did not begin our investigation from this point of view.

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.

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.

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.

Living material contains about twenty different sorts of atom combined into a set of relatively simple molecules. Astrobiologists tend to believe that abiotic mater­ ial will give rise to life in any place where these molecules exist in appreciable abundances and where physical conditions approximate to those occurring here on Earth. We think this popular view is wrong, for it is not the existence of the building blocks of life that is crucial but the exceedingly complicated structures in which they are arranged in living forms. The probability of arriving at biologically significant arrangements is so very small that only by calling on the resources of the whole universe does there seem to be any possibility of life originating, a conclusion that requires life on the Earth to be a minute component of a universal system. Some think that the hugely improbable transition from non-living to living mat­ ter can be achieved by dividing the transition into many small steps, calling on a so-called 'evolutionary' process to bridge the small steps one by one. This claim turns on semantic arguments which seek to replace the probability for the whole chain by the sum of the individual probabilities of the many steps, instead of by their product. This is an error well known to those bookies who are accustomed to taking bets on the stacking of horse races. But we did not begin our investigation from this point of view.

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.

Living material contains about twenty different sorts of atom combined into a set of relatively simple molecules. Astrobiologists tend to believe that abiotic mater­ ial will give rise to life in any place where these molecules exist in appreciable abundances and where physical conditions approximate to those occurring here on Earth. We think this popular view is wrong, for it is not the existence of the building blocks of life that is crucial but the exceedingly complicated structures in which they are arranged in living forms. The probability of arriving at biologically significant arrangements is so very small that only by calling on the resources of the whole universe does there seem to be any possibility of life originating, a conclusion that requires life on the Earth to be a minute component of a universal system. Some think that the hugely improbable transition from non-living to living mat­ ter can be achieved by dividing the transition into many small steps, calling on a so-called ''evolutionary'' process to bridge the small steps one by one. This claim turns on semantic arguments which seek to replace the probability for the whole chain by the sum of the individual probabilities of the many steps, instead of by their product. This is an error well known to those bookies who are accustomed to taking bets on the stacking of horse races. But we did not begin our investigation from this point of view.