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Variational principles in dynamics and quantum theory
Book reviews
some of
C)PIK's
British
meteor
original papem to be very brilliant but difficult reading. PORTER’s analysis of the data is discussed, and the very precise photographic measurements of velocities and radianta, made by WHIPPLJEand JACCEIA, are covered in considerable detail in the book. To date the photographic results are the most accurate available but they are few in number and The Super-Schmidts are expected to apply only to meteors brighter than zero magnitude. extend the observations to the third magnitude. The apex and anti-apex velocity experiments carried out at Jodrell Bank, and the similar Canadian observations, are thoroughly discussed. These radio methods have extended the range of observations to the eighth magnitude and also have included the daylight hours. The conclusions to be drawn from all the contemporary investigations, with the exception of OPIK’S work, is that very few sporadic meteors can be reaching us from interstellar space. In fact, at the time of writing this book there was no clearcut and positive evidence of the existence of any meteors with highly hyperbolic velocities, but the search will be continued and extended to fainter magnitudes. In the light of present information, it would be just as implausible to assert that we are receiving no visitors at all from outside the solar system as it would be to say that the majority are from interstellar space. The major meteor showers are each discussed fully, using data from all available sources. In the case of the daytime showers, of course, practically all of the information comes from the Jodrell Bank workers, who are unchallenged in this particular field. LOVELL discusses the number and mass distribution of the shower meteors, and enlarges on the cosmological relationships of meteors, indicating the probability that some streams have cometary associations and others have not. Both WHIPPLE and LOVELL have pointed out that many of the sporadic meteors have short-period direct orbits near the plane of the ecliptic and hence are more likely to be asteroidal in nature. There is further speculation on the origin and history of some of the showers, in view of current theories on the dispersive effects acting on the particles. The volume contains a large number of very useful tables and is copiously illustrated with line drawings, although the paucity of half-tone plates is to be regretted-this is presumably dictated by the publisher. It contains the essential background information needed not only by every scientific worker in the field but also by radar and communications engineers, who are beginning to realize that meteoric effects may be assets in some of their projects and liabilities in others; in either case the meteors cannot be ignored. D. W. R. MCKINLEY
WOLFCANC YOURGRAU and STANLEY MANDELSTAM; Variational Principles in Dynamics Quantum Theory, Sir Isaac Pitman & Sons, Ltd., London, 1955. ix + 155 pages. 25s.
and
The aim of this book is to review the historical development of variational principles in physics and to assess their epistemological significance. The authors do not delve very far below the surface, but they are clearly aware of the limited scope of their enquiry and they have the great The result is a clear, straightforward, reliable merit of going directly back to the sources. account of the subject, from the treatment of the reflection of light attributed to HERO of Alexandria to the ideas of DE BROQLIE and SCHR~DIN~ER, with due emphasis on the work of HAMILTON and JACOBI. The authors develop all calculations in great detail, writing out every step; a feature which will no doubt be welcomed by the student and may in fact be a valuable help to him, provided that he has sufficient self-discipline to try to do the job by himself first. The epistemological chapter must be commended for its sound common sense and its polite, but quite effective, exposure of the incredible childishness with which some very great men have approached the philosophical aspect of the problem. Altogether a neat, unpretentious piece of work, which will be read with interest by experienced physicists, but which above all will be profitably used by students as a first introduction into an important subject of great educative value. L. ROSENFELD
110
some of
C)PIK's
British
meteor
original papem to be very brilliant but difficult reading. PORTER’s analysis of the data is discussed, and the very precise photographic measurements of velocities and radianta, made by WHIPPLJEand JACCEIA, are covered in considerable detail in the book. To date the photographic results are the most accurate available but they are few in number and The Super-Schmidts are expected to apply only to meteors brighter than zero magnitude. extend the observations to the third magnitude. The apex and anti-apex velocity experiments carried out at Jodrell Bank, and the similar Canadian observations, are thoroughly discussed. These radio methods have extended the range of observations to the eighth magnitude and also have included the daylight hours. The conclusions to be drawn from all the contemporary investigations, with the exception of OPIK’S work, is that very few sporadic meteors can be reaching us from interstellar space. In fact, at the time of writing this book there was no clearcut and positive evidence of the existence of any meteors with highly hyperbolic velocities, but the search will be continued and extended to fainter magnitudes. In the light of present information, it would be just as implausible to assert that we are receiving no visitors at all from outside the solar system as it would be to say that the majority are from interstellar space. The major meteor showers are each discussed fully, using data from all available sources. In the case of the daytime showers, of course, practically all of the information comes from the Jodrell Bank workers, who are unchallenged in this particular field. LOVELL discusses the number and mass distribution of the shower meteors, and enlarges on the cosmological relationships of meteors, indicating the probability that some streams have cometary associations and others have not. Both WHIPPLE and LOVELL have pointed out that many of the sporadic meteors have short-period direct orbits near the plane of the ecliptic and hence are more likely to be asteroidal in nature. There is further speculation on the origin and history of some of the showers, in view of current theories on the dispersive effects acting on the particles. The volume contains a large number of very useful tables and is copiously illustrated with line drawings, although the paucity of half-tone plates is to be regretted-this is presumably dictated by the publisher. It contains the essential background information needed not only by every scientific worker in the field but also by radar and communications engineers, who are beginning to realize that meteoric effects may be assets in some of their projects and liabilities in others; in either case the meteors cannot be ignored. D. W. R. MCKINLEY
WOLFCANC YOURGRAU and STANLEY MANDELSTAM; Variational Principles in Dynamics Quantum Theory, Sir Isaac Pitman & Sons, Ltd., London, 1955. ix + 155 pages. 25s.
and
The aim of this book is to review the historical development of variational principles in physics and to assess their epistemological significance. The authors do not delve very far below the surface, but they are clearly aware of the limited scope of their enquiry and they have the great The result is a clear, straightforward, reliable merit of going directly back to the sources. account of the subject, from the treatment of the reflection of light attributed to HERO of Alexandria to the ideas of DE BROQLIE and SCHR~DIN~ER, with due emphasis on the work of HAMILTON and JACOBI. The authors develop all calculations in great detail, writing out every step; a feature which will no doubt be welcomed by the student and may in fact be a valuable help to him, provided that he has sufficient self-discipline to try to do the job by himself first. The epistemological chapter must be commended for its sound common sense and its polite, but quite effective, exposure of the incredible childishness with which some very great men have approached the philosophical aspect of the problem. Altogether a neat, unpretentious piece of work, which will be read with interest by experienced physicists, but which above all will be profitably used by students as a first introduction into an important subject of great educative value. L. ROSENFELD
110