摘要:

It is shown in this review that the concept of auroral arcs forming one or more complete rings encircling the polar cap was very well accepted in the 18th century. This idea was elaborated further throughout the 19th century but then disappeared from the scientific scene for almost 80 years owing to the promotion of the auroral zone as a better frame of reference in auroral research. It is pointed out that the auroral zone was a dead end more influenced by the prevailing ideas of the last century than a product of profound physical reasoning. Finally, the importance of historical reviews in the field of science is stressed to learn to appreciate the often well‐developed ideas of our predecessors and thereby avoid long periods of wandering in darkness, as had happened in the auroral zon

ISSN:0002-8606    

DOI:10.1029/EO065i038p00705

年代:1984

数据来源: WILEY

摘要:

“Dynamics!” she said, as she buried her head deep in a book on tectonics. “Must be the key to explain what we see the ignorance of which seems to be chronic.”Convection below, then density flow and phase changes are not withstanding; Thermal gradient change and compositional range are things our minds should be com

ISSN:0002-8606    

DOI:10.1029/EO065i038p00706

年代:1984

数据来源: WILEY

摘要:

At last count, there were more than 160 satellites in geostationary orbits, circling the earth at an altitude of 37,000 km, and according to a research review published recently by the Rand Corporation, that's already too crowded. The risk of physical collisions among satellites is small, say authors Alvin L. Hiebert and William Sollfrey, but there is an emerging problem with what they call “spectral and orbital congestion,” the result of too many satellites and ground stations sending out too many electromagnetic signals that can interfere with one another.The report comes at a time when the Federal Communications Commission is planning to reduce the spacing between satellites along the U.S. segment of the orbital arc so that 37 additional satellites can be squeezed into the high orbit favored for telecommunications. “As more satellites are launched and others are shifted to avoid collisions, interference problems will get more complicated,” say the authors of the

ISSN:0002-8606    

DOI:10.1029/EO065i038p00707-01

年代:1984

数据来源: WILEY

摘要:

This book is similar in format toPrecambrian Iron‐Formations of the World, published in 1973 as a special issue ofEconomic Geology(vol. 68, no. 7). Both have 16 papers and begin with descriptions of iron formations or iron districts followed by topical papers on various aspects o f the iron formation problem. New basic data on Precambrian iron bearing and associated rocks has continued to accumulate since 1973, and the present volume admirably fills the need to compile this widespread information and to reexamine these enigmatic rocks in the light of new discoverie

ISSN:0002-8606    

DOI:10.1029/EO065i038p00708-01

年代:1984

数据来源: WILEY

摘要:

This monograph “chronicles the use of television cameras and other visual imaging systems by NASA on unmanned outer space probes and in the exploration of the Solar System's planetary bodies.”The book is technically well organized and a nicely printed volume with the unfortunate exception of the 32 illustrative plates that are of nothing less than abysmal quality. Included in the selection of pictures are a number of classic Voyager color photographs, but the high contrast black and white renditions in this volume convey little of their original beauty or information cont

ISSN:0002-8606    

DOI:10.1029/EO065i038p00709-01

年代:1984

数据来源: WILEY