Scientific American September 2004(95s).pdf: eKnigu

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Scientific American September 2004(95s).pdf

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Date Nov 14, 2004

Humans began to live long and prosper only about 30,000 years ago, researchers report. A recent survey of hominid dental remains reveals that the number of people surviving to old age increased fourfold during the Upper Paleolithic period. This newfound longevity may have given anatomically modern humans an advantage over other hominids....

T H E SCIENCE OF POLITICS Regarding “Bush-League Lysenkoism”
[SA Perspectives], the Bush administration is doing exactly what President Bill Clinton did during his term—but most of
S E P T E M B E R 2004...

GET THE BEAT Per Enge’s article [“Retooling the Global
Positioning System”] states that two audible tones in air would produce a beat note. This is not true—if it were, music would be a cacophony with all the beat notes produced. Beat notes occur only in nonlinear media such as an electronic mixer....

T H E ACTION OF WORMS—“Beneath the city of Berlin, in Prussia, there is a deep bog of black peat. Professor Ehrenberg, a gentleman whose explorations into the mysteries of microscopic life S E P T E M BE R 1904 have attained for him a high poT H I N K I N G HORSE—“Hardly a sition among the scientiﬁc men day passes but the newspapers of the age, says that this peat, at have something to say of the the depth of ﬁfty feet, swarms wonderful mental performances with infusorial life; that countof ‘clever Hans,’ ‘der kluge Hans,’ less myriads of microscopic anias Herr Von Osten’s stallion is mals live there and wriggle and called. An investigation conductdie. The perpetual motion of ed by scientists, however, would these little animals causes the seem to indicate that the horse is whole mass of peaty matter to be T H E NEW OCEAN LINER compared to Trinity Church, 1904 really what his owner claims him in a state of constant though gento be, an intelligent four-footed erally imperceptible movement. animal, capable of making simple arith- T H E NEW CUNARDERS—“Among the nau- In Berlin, the houses are wont to crack metical calculations. Dr. Heinroth, of the tical exhibits at the St. Louis Exposition, and yawn sometimes, in an exceedingly Berlin Zoological Garden, has questioned the model that attracts the most attention curious manner, even though built on apthe horse in his stall in the absence of its is that of the new 25-knot, 40,000-ton parently stable foundations; and Profesowner, and he has received answers as turbine steamers of the Cunard Steamship sor Ehrenberg believes this to be owing clear-cut and as precise as those given in Company. If the new liner were placed in to the combined efforts of inﬁnite million the presence of Von Osten.” [Editors’ the churchyard alongside Trinity Church of tiny forms.”...

N U T S - A N D - B O L T S TRIALS of missile defense, such as the tracking of this Minuteman III...

Richard Matlock, named the MDA’s ﬁrst director of modeling and simulation after the science board report was released, says current models “do a very good job at predicting the performance of system components.” But the report did conﬁrm the need to enhance those models as missile defense evolves, he remarks. According to the MDA, an aggressive evaluation program will occur over the next few years as the test bed is upgraded. “We will constantly improve our capabilities through operationally realistic testing,” an MDA spokesman comments. “We can’t operationally test the system until we put it into place.” That will happen shortly before voters decide between Bush and presidential candidate Senator John Kerry of Massachusetts, who says missile defense research is important but believes the Bush approach has not been sufﬁciently tested. The Pentagon asserts that the timing of the deployment is a coincidence, but opponents are skeptical. “I believe that’s a big part of the push for deployment this year,” Coyle says. Daniel G. Dupont edits InsideDefense.com, an online news service. He wrote about the threat of high-altitude nuclear explosions in the June issue....

sity proﬁle matching those of real galaxies. That inﬂation, dark energy and dark matter can all be laid at the doorstep of scalar ﬁelds suggests that they might be connected. Israel Quiros of UCLV argued at the workshop that the same ﬁeld could account for both inﬂation and dark energy. Other physicists have worked on linking the two dark entities. “As my senior colleagues used to say, ‘You only get to invoke the tooth fairy once,’” says Robert Scherrer of Vanderbilt University. “Right now we have to invoke the tooth fairy twice: we need to postulate a yet to be discovered particle as dark matter and an unknown source for dark energy. My model manages to explain both with a single ﬁeld.” But all these models suffer from a nagging problem. Because the wave-...

Before selecting your executive MBA provider we thought you might like to , see a photo of our campus....

PUMP IT IN
Crude oil imports and exports in 2003, in millions of barrels per day: Leading Importers U.S. Japan Germany China Leading Exporters Persian Gulf states Russia Norway Venezuela 18.7 5.5 3.3 2.2 11.2 5.5 2.5 2.0...

that should make a Fermi condensate more likely to form. But they needed to use two isotopes of lithium to do the cooling, and each one required its own set of lasers. Jin ﬁgured she could use one type of atom—the fermion potassium 40—and put it in two spin states. (An atom’s spin relates to its behavior in magnetic ﬁelds.) If they had different spins, fermions could collide and exchange energy, and Jin could shoo away the higher-energy ones until only very cool fermions remained. “She was the ﬁrst to work on potassium, and that turned out to be a shortcut,” Ketterle says. Jin’s technique required fewer lasers and a simpler setup. “It was really technologically much easier,” Jin conﬁdes....

mitted in 1901—an unexceptional work on the kinetic theory of gases. Einstein had all but discarded the idea of undergoing what he called the “comedy” of getting his advanced degree. But he decided to try again in 1905. According to his sister, Maja, he ﬁrst submitted his paper on special relativity, but the university found it a “little uncanny.” He then picked “A New Determination of Molecular Dimensions,” which he ﬁnished on April 30 and which was accepted in July. It was reportedly inspired by a conversation over tea with his best friend, Michele Besso, in which Einstein mused about relating the viscosity of the liquid to the size of the dissolved sugar molecules. By considering a collection of such molecules, Einstein derived a mathematical term that measured the speed of diffusion. It was then possible to elicit the size of the sugar molecules by contemplating the diffusion coefﬁcient and the viscosity of the solution. A few days after completing this article, Einstein ﬁnished a related paper that was also intended to provide a guarantee of “the existence of atoms of deﬁnite size”—atoms were a still controversial idea in some circles. “On the Motion of Small Particles Suspended in Liquids at Rest Required by the Molecular-Kinetic Theory of Heat,” published in July in Annalen, supplied a prediction of the number and mass of molecules in a given volume of liquid—and how these molecules would ﬂit around. The erratic movements were known as Brownian motion, after the observation by Robert Brown in the early 19th century of the irregular zigs and zags of particles inside pollen grains in water. Einstein suggested that the movements of the water molecules would be so great that they would jostle suspended particles, a dance that could be...