archive: SETI Physics News Update.248

SETI Physics News Update.248

Larry Klaes ( lklaes@bbn.com )
Fri, 14 May 1999 17:02:00 -0400

>Date: Fri, 14 May 1999 11:03:47 -0400 (EDT)
>From: AIP listserver <physnews@aip.org>
>To: physnews-mailing@aip.org
>Subject: update.248
>
>PHYSICS NEWS UPDATE
>The American Institute of Physics Bulletin of Physics News
>Number 428 May 14, 1999 by Phillip F. Schewe and Ben Stein
>
>PI AND RANDOM NUMBERS. Pi is a "quark" of mathematics: it
>is one of the basic building blocks out of which various
>geometrical and algebraic relations are built. Normally thought of
>as the ratio of a circle's circumference to its diameter, pi keeps
>turning up in odd places. For example, Georges Leclerc, Count de
>Buffon, was the first to show a connection between pi and the
>occurrence of random events. In 1777 he performed an experiment
>in which needles are randomly dropped onto a surface covered
>with ruled lines spaced apart by an amount equal to the size of the
>needle; the fraction of times the needle comes down astride a line
>is related to pi. Mathematicians have exploited this relation to
>make random number generators. Sylvan Bloch (813-961-0778), of
>the University of South Florida does the converse of this. He and
>Robert Dressler developed software (for the classroom) for using
>random numbers to generate a statistical estimation of pi. By the
>way, in warped spacetime pi is not necessarily equal to the ratio of
>a circle's circumference to its diameter. As an appendix to his
>article in the April issue of the American Journal of Physics, Bloch
>shows how "pi" varies as space becomes increasingly curved. (As
>usual science journalists can obtain copies of articles from AIP
>public information. For pi lore, see
>http://forum.swarthmore.edu/dr.math/faq/faq.pi.html.)
>
>ATOMIC STEERING COMMITTEE. Even the smoothest-
>looking coatings are very rough on the atomic scale, with islands
>of atoms peppered abundantly across the microscopic landscape.
>Depositing copper atoms on a Cu surface, researchers (Sebastiaan
>van Dijken, University of Twente, the Netherlands,
>s.vandijken@tn.utwente.nl) have identified a largely ignored
>mechanism which contributes to introducing roughness in films of
>atoms being deposited onto surfaces. Known as steering, it arises
>when surface atoms, including already deposited ones, exert
>chemical forces on incoming atoms and cause them to veer towards
>the surface. This is reminiscent of how static electricity can cause
>some of the milk poured from a glass to drip down the sides rather
>than fall freely from the glass. Steering causes incoming atoms,
>especially those approaching the surface at grazing angles, to arrive
>preferentially on the top of protruding islands of atoms. Therefore,
>steering can make already rough surfaces even rougher. Besides
>providing insights into the causes of roughness, understanding this
>effect may help researchers to prepare arrays of surface ridges,
>which could serve as templates for making magnetic nanowires
>and other customized materials. (S. van Dijken et al., Physical
>Review Letters, 17 May 1999; figures at
>www.aip.org/physnews/graphics)
>
>KING EDWARD III of England (1312-1377) has, back to the time
>of Charlemagne, about 1000 perches on his family tree. Of course
>in the relatively closed world of medieval royalty, many names on
>that tree appear more than once; indeed the repetition of ancestors
>conforms to a predictable pattern. A new study of the statistical
>properties of genealogical trees, using Edward III's pedigree as a
>case history, concludes that by going about 30 generations into
>your past, you and all your contemporaries will be related to
>everyone who lived then, at least to those who had offspring and
>who lived within that particular geographical or cultural realm.
>Bernard Derrida of the Ecole Normale Superieure in Paris
>(bernard.derrida@lps.ens.fr), Susanna Manrubia of the Max Planck
>Institute in Berlin, and Damian Zanette (Barlioche, Argentina),
>have discovered that the factors shaping the patterns of repetitions
>of individuals in family trees have traits in common with the forces
>that govern the behavior of granular materials and can,
>furthermore, be understood using the mathematical tools applied to
>a variety of phase transitions in physics. They expect their work to
>have applications in the study of population genetics and
>evolutionary biology. (Physical Review Letters, 1 March 1999;
>view Edward's family tree at
>http://uts.cc.utexas.edu/~churchh/edw3chrt.html; see figure at
>www.aip.org/physnews/graphics )
>