ISSN:0031-9228    

DOI:10.1063/1.2805891

出版商:AIP    

年代:1998

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.882428

出版商:AIP    

年代:1998

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.882432

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The concept of six degrees of separation, as studied over three decades ago by the social psychologist Stanley Milgram, grew from an experiment in which two target persons were identified in the Boston area, and then individuals in Kansas and Nebraska were each sent a letter describing some parameters of the two targets. Each individual was given a folder with the rule for reaching the target: If the individual didn't know the target, he was asked to send the folder to a friend he knew on a first‐name basis who was likely to know the target person. Mil‐gram's surprising result was that the number of links needed to reach the target person had a median value of six. This concept is also known as the small‐world phenomenon.

ISSN:0031-9228    

DOI:10.1063/1.882433

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The quantization of electric charge is very well tested: The proton and electron charges±eare equal and opposite to better than a part in1021,and the neutrality of the neutron, photon and neutrino have been experimentally affirmed with comparable precision. And all attempts to find naked fractionally charged quarks have failed thus far, as the theory of quark confinement tells us they must.

ISSN:0031-9228    

DOI:10.1063/1.882434

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The “rubbing and scrubbing department” was how David Tabor's friction, lubrication and wear laboratory was described by certain uncharitable colleagues at the Cavendish Laboratory in Cambridge, England, some 40 years ago. The tables have turned. Tribology, as Tabor named his discipline (from the Greektribos, meaning “rubbing”), has become respectable—even positively modish—in physics departments worldwide. And Tabor, having become the revered elder statesman of this flourishing field, is often accorded a place in reference of even the most hardcore tribo‐physics papers.

ISSN:0031-9228    

DOI:10.1063/1.882435

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The hoax perpetrated by New York University theorical physicist Alan Sokal in 1996 on the editors of the journalSocial Textquickly became widely known and hotly debated. (SeePHYSICS TODAYJanuary 1997, page 61, and March 1997, page 73.) “Transgressing the Boundaries—Toward a Transformative Her‐meneutics of Quantum Gravity,” was the title of the parody he slipped past the unsuspecting editors. (See figure 1.)

ISSN:0031-9228    

DOI:10.1063/1.882436

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

If you were to tell a child playing with a horseshoe magnet and pieces of iron that his uncle has a much bigger magnet that can lift everything and everybody, the child would probably believe you and might even ask for a ride on the magnet. If a physicist were present at such a conversation, he or she—armed with knowledge and experience—would probably smile condescendingly. The physicist would know well that only a very few materials—such as iron or nickel—are strongly magnetic, while the rest of the world's materials are not; to be precise, the rest of the world is a billion(109)times less magnetic. This number seems obviously too large to allow common substances (water, for example) to be lifted even by the most powerful magnets; a billionfold increase in magnetic fields can be found only on neutron stars. In this case, however, knowledge and experience would mislead the physicist: In fact, all materials can be lifted by using magnetic fields that are rather standard these days. In principle, even a child can be levitated by a magnet, as we shall see below.

ISSN:0031-9228    

DOI:10.1063/1.882437

出版商:AIP    

年代:1998

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.882463

出版商:AIP    

年代:1998

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.882438

出版商:AIP    

年代:1998

数据来源: AIP