ISSN:0031-9228    

DOI:10.1063/1.2409941

出版商:AIP    

年代:1903

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.1554120

出版商:AIP    

年代:1903

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.1554121

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Two collatorations at CERN have been pursuing a long‐term goal: to make precision tests of how an atom of antimatter might differ from its ordinary‐matter counterpart. An antihydrogen atom (consisting of a positron bound to an antiproton) might, for example, fall at a slightly different rate than a hydrogen atom. Or the lowest‐lying states of the positron might have slightly different energies than those of the electron in hydrogen. If a precision test indicated that either hypothesis were true, it would shatter a very basic tenet of physics. Different rates of fall would challenge predictions of general relativity, and different energy levels would violate the invariance of physics under the simultaneous operations of charge conjugation, time reversal, and parity inversion.

ISSN:0031-9228    

DOI:10.1063/1.1554124

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Some form of the long jump was featured in the ancient Olympics after it was introduced in 708 BC as part of the pentathlon. But as vase paintings such as the one shown in the top photograph attest, there was an intriguing difference between the way ancient athletes performed their jumps and the way modern ones do: Ancient Olympians took off holding halteres, or jumping weights. The weights, made of stone or lead, improved the jumpers’ performance.

ISSN:0031-9228    

DOI:10.1063/1.1554125

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

A complicated interplay of processes occurred 4.6 billion years ago in the early stages of the Solar System as material from the initial solar nebula condensed and collided to form aggregates, planetesimals, and eventually planets. And on Earth as well as the other terrestrial planets and the larger asteroids, heat from accretion and from the decay of short‐lived isotopes such as aluminum‐26 was sufficient to melt—at least partially—the assembled material, which led to the segregation of the iron‐rich core and the silicate mantle.

ISSN:0031-9228    

DOI:10.1063/1.1554126

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

NASA has no business in ground‐based astronomy. That sentiment, repeated often by Edward Weiler, the agency's associate administrator for space science, is nothing new. But it's getting stronger, say some US planetary astronomers, and despite the first budget hike in a decade, they fear for the future of their field.

ISSN:0031-9228    

DOI:10.1063/1.1554127

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Stunned by two recent high‐profile cases of scientific misconduct by physicists, the American Physical Society council has adopted “updated and expanded” ethics guidelines that clarify the responsibilities of coauthors of scientific papers, urge a stronger emphasis on ethics education, and call for all research institutions to follow the Federal Policy on Research Misconduct. The new guidelines, developed by the ethics subcommittee of the APS panel on public affairs, are much more direct than the previous 1991 guidelines in addressing the issues of scientific misconduct and fraudulent research.

ISSN:0031-9228    

DOI:10.1063/1.1554128

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Ian Halliday suddenly has money to play with. The UK's Particle Physics and Astronomy Research Council (PPARC), which Halliday heads, has had a tight budget for years. But now the UK can become a real player in planning the next big particle accelerator, he says. “And we'll most likely join LIGO”—the Laser Interferometer Gravitational Wave Observatory in the US.

ISSN:0031-9228    

DOI:10.1063/1.1554130

出版商:AIP    

年代:1903

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2409942

出版商:AIP    

年代:1903

数据来源: AIP