摘要:

One problem arising in teaching special relativity is the confusion in many texts of the thought experiments, used in developing the theory, with other simple laboratory operations. As an example we consider here the observation of length. The existence of the Lorentz-Fitzgerald contraction has led educators to conclude that oneseesa contraction of a rapidly moving body. However, the act ofseeinginvolves a single observer, while the observation of the Lorentz-Fitzgerald contraction requires at least two observers. It is shown here that the length seen by a single observer is not the usual contraction, and indeed, under certain circumstances, one sees a body considerably lengthened rather than contracted.

ISSN:0002-9505    

DOI:10.1119/1.1935916

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1935917

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

A symposium on space science was held in connection with the Annual Meeting of the American Association of Physics Teachers at New York, on January 29, 1960. Part of the remarks made by the chairman in introducing the participants, Hannes Alfvén, Herbert Friedman, and Ernst J. Öpik are reproduced in this introduction.

ISSN:0002-9505    

DOI:10.1119/1.1935918

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

A review is given of the development in the field of cosmical electrodynamics. It is mentioned that the great interest in thermonuclear research has produced a considerable progress in plasma physics. This is of astrophysical interest because it is now possible to check the theories of a plasma by experiment.As an example, a recent experiment in a “homopolar” machine is discussed, and its importance to the theory of the origin of the solar system is emphasized. Conclusions about the origin of the solar system are drawn. In particular, the mechanism by which Saturn's ring has been produced is discussed. It is further pointed out that the moon probably was born as a planet later captured by the earth.

ISSN:0002-9505    

DOI:10.1119/1.1935919

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

From a critical study of the available evidence, the author has prepared a review, chiefly of the more controversial problems relating to the surface structure of our nearest neighbors in space—the moon, Mars, and Venus. The task is similar to that of solving a crossword puzzle; the answer must agree with, or at least not contradict, all the existing data. In many respects the conclusions differ from those conventionally accepted and quoted in standard textbooks.

ISSN:0002-9505    

DOI:10.1119/1.1935920

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

Rocket astronomy has mapped the spectrum of the sun from the ground level cutoff at 3000 A down to x-ray wavelengths as short as 0.1 A. The x-ray emissions are strongly dependent onsolar activity with greatly enhanced intensities accompanying solar flares. Photographs from rockets have revealed the disk distribution of ultraviolet emission. The first measurements ofultraviolet light of the night sky have discovered the existence of extended ultraviolet nebulosities surrounding hot stars and a bright diffuse glow of Lyman-α radiation scattered fromneutral hydrogen in space.

ISSN:0002-9505    

DOI:10.1119/1.1935921

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

Einstein's early work on relativity theory is found to be related to his other work at that time (e.g., in subject matter and style). In addition to this element of internal continuity one finds also—as a key to a new evaluation of the significance of Einstein's contribution—an external continuity with the classic, Newtonian tradition governing restrictions on permissible hypotheses. On the other hand, Einstein's work is shown to have been, in important respects, more independent of other contemporary work in this field than has recently been proposed.These continuities and discontinuities are set forth to make the point that philosophical studies of scientific work should proceed on historically valid ground. Some guiding principles are indicated for dealing with conflicting source materials for such studies.

ISSN:0002-9505    

DOI:10.1119/1.1935922

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

It is pointed out that oversimplified pictures of ferromagnetic transformers are not satisfactory from the viewpoint of Maxwell's equations. A simple one-dimensional solution for the electromagnetic field of an ideal ferromagnetic core consistent with the field equations is presented. The author suggests that only such fields be used in introductory courses.

ISSN:0002-9505    

DOI:10.1119/1.1935923

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

The classical theory of the electron, as proposed by Abraham and Lorentz, is usually presented as beset by the difficulty that the momentum and velocity of its Coulomb field are incorrectly related kinematically:p = 43msv, wheremsis the electromagnetic mass defined by the electromagnetic self-energy. This problem also persists in the relativistic theory. It is shown here that the difficulty is eliminated from the relativistic theory by treating the integrals over the electromagnetic field in a relativistic fashion, i.e., taking note of their dependence on the motion of the electron. The surface dependence of the integrals representing the electromagnetic momentum and energy of the particle is essential and occurs whenever the matter tensor is not introduced. The nonrelativistic limit of this formulation then also leads to the correct relationshipp = msv. The corrected Abraham-Lorentz theory still contains the stability problem, but this problem is no longer related to the transformation properties. It can be removed by renormalization.

ISSN:0002-9505    

DOI:10.1119/1.1935924

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

Use of the rubber membrane model as a teaching aid is discussed, both for elementary lecture demonstrations and for intermediate laboratory experiments. The model can be used to demonstrate directly and vividly by analogy two-dimensional potential fields, and trajectories of particles moving in these fields.

ISSN:0002-9505    

DOI:10.1119/1.1935925

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP