ISSN:0031-9228    

DOI:10.1063/1.2807750

出版商:AIP    

年代:1996

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2807751

出版商:AIP    

年代:1996

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2807752

出版商:AIP    

年代:1996

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2807753

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The phrase “geologic time” conjures images of continents moving at centimeters per year, or of mountains forming and eroding over hundreds of millions of years. Yet, some geologic processes evolve at a rate that allows significant changes to take place on the scale of a human lifetime. Earth's magnetic field changes on a time scale of decades—presumably mirroring changes in the planet's electrically conducting, fluid outer core, the motion of which is thought to generate and sustain the geomagnetic field. Last year, Gary Glatzmaier (Los Alamos National Laboratory) and Paul Roberts (University of California, Los Angeles) generated the most realistic model yet of this “geodynamo,” and predicted that the rotation rate of Earth's inner core evolves on a scale of centuries rather than eons. Moreover, in their simulation the magnetic field and the flow of the fluid outer core caused the solid inner core nearly always to spin more rapidly than the mantle and crust—the result of magnetic coupling between the inner core and a jet‐stream–like layer of rapidly rotating outer‐core fluid at the inner‐core boundary (SeePHYSICS TODAY, January, page 17).

ISSN:0031-9228    

DOI:10.1063/1.2807754

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Okay, never mind that what may have been humankind's first encounter with extraterrestrial life didn't have the drama ofThe War of the Worlds, independence Dayor evenMy Favorite Martian. Never mind that toy companies are now trying to figure out how to bid for the rights to and then market toys patterned after submicrometer‐long extraterrestrial bacteria. What is important is for us to understand the chain of scientific reasoning that has led to the claim that the Allan Hills (ALH) 84001 meteorite may contain fossil evidence of life from Mars.

ISSN:0031-9228    

DOI:10.1063/1.2807755

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Conventional metals have been very successfully described by the Fermi‐liquid theory, but researchers are now studying a variety of more exotic materials for which other approaches might be more appropriate. Among the alternatives is a model of interacting electrons in one dimension. The model is known as the Tomonaga‐Luttinger liquid theory, after Joaquin Luttinger, who formulated it in the 1960s, and Sin‐itiro Tbmonaga, who did influential one‐dimensional studies in the 1950s. It is frequently called simply a Luttinger liquid.

ISSN:0031-9228    

DOI:10.1063/1.2807756

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Shortly after noon on 9 July, an important new experimental regime of high‐energy physics was inaugurated with the first observation of aW+W−pair at CERN's Large Electron‐Positron (LEP) collider. The charged W's and their neutral cousin, theZ0,are the three spin‐1 bosons that mediate the weak interactions. Because they are almost 100 times heavier than the proton, these “intermediate vector bosons” present a particular challenge to accelerator builders and experimenters. Though their existence and their masses were predicted by the Glashow‐Salam‐Wemberg unification of the electromagnetic and weak forces in the late 1960s, they could not be observed until the 540‐GeV CERN proton‐antiproton collider was completed in the early 1980s. (SeePHYSICS TODAY, November 1983, page 17).

ISSN:0031-9228    

DOI:10.1063/1.2807757

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Galileo Galilei was almost seventy years old, his life nearly shattered by a trial for heresy before the Inquisition, when he retired in 1633 to his villa near Florence to construct theDialogues Concerning ‘Two New Sciences. His first science was the study of the forces that hold objects together and the conditions that cause them to fall apart—the dialogue taking place in a shipyard, triggered by observations of craftsmen building the Venetian fleet. His second science concerned local motions—laws governing the movement of projectiles.

ISSN:0031-9228    

DOI:10.1063/1.881515

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The extraordinary discovery of a number of planetary‐mass bodies orbiting nearby stars similar to the Sun has completely transformed the field of extrasolar planet detection. This sudden transformation has been brought about by a handful of dedicated observers, working quietly with modest‐sized telescopes, often for decades at a time. They include Michel Mayor and Didier Queloz at the Geneva Observatory, Geoffrey Marcy and R. Paul Butler at San Francisco State University and George Gatewood at the University of Pittsburgh. Many of the new objects have already been independently confirmed. The history of failure to confirm earlier claims for extrasolar planets mercifully has been forgotten at long last, as astronomers and planetary scientists rush to find even more planets.

ISSN:0031-9228    

DOI:10.1063/1.881516

出版商:AIP    

年代:1996

数据来源: AIP