scientific american - 1993 10 - is los angeles winning the war on smog
scientific american - 1993 10 - is los angeles winning the war on smog
... chest discom-fort, 100 million person-days of head-ache, 120 million person-days of cough-ing, 180 million person-days of sorethroats and 190 million person-days ofeye irritation.These terrible ... found thatin almost one Þfth of all the vehicles on the road, the emissions-control equip-ment was either removed by the own-er or damaged by the use of leaded fu-els. The latter problem has ... altruism in the natural world. The standard paradigm for analyzing the evolution of cooperation is a co-nundrum called the Prisoner’s Dilemma. This problem considers two sus-pects, imprisoned...
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scientific american - 1994 10 - special issue - life in the universe
... results consis-tent with some of these conditions, weusually Þnd that the results violate the other conditions. It seems that any rel-ativistic quantum theory that satisÞesall these conditions ... can tell, the onlymathematically consistent relativisticquantum theories that satisfy these con-ditions at all energies and that involvegravitation are string theories. Further, the student ... 0.50DENSITY0 .10. 01RELATIVE ABUNDANCE1.01.0 10 -2 10 -4 10 -6 10 -8 10 -1 0HELIUMHELIUM 3LITHIUMDEUTERIUMCopyright 1994 Scientific American, Inc.would still be detectable in the existinguniverse.Despite...
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scientific american - 1993 01 - the turbulent birth of the milky way
... even longer. If the for-mal version contains N lines, the arith-metized one will contain K times Nraised to the power of one plus epsilon.K is very large, and the various math-ematicians disagree ... temperature. The disturbance alsocaused a nearly complete interruptionin the long-term accumulation of calci-um carbonate on the reefs of the region. The fact that healthy reefs ßourishedin the eastern ... disrupted the oldest disk clus-ters, leaving behind only younger ones.Determining the relative ages of the halo and disk reveals much about the sequence of the formation of the gal-axy. On the other...
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scientific american - 1993 02 - beating resistance in superconductors
... protects the sample from the heat, to the surface of the superconduc-tor. There they decorate the regions where the magnet-ic-flux lines pass through the surface. The iron parti-cles “stick” to the ... American, Inc.50 SCIENTIFIC AMERICAN February 1993 the theory that provided the microscop-ic explanation for superconductivity.According to the so-called BCS theory, the conduction electrons ... superconductor. The Þrst ofthese is the spatial separation of the electrons in a Cooper pair. This dis-tance is referred to as the coherencelength. It is the smallest length in a superconductor...
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scientific american - 1993 03 - black holes and the centrifugal force paradox
... particular rep-resentation may minimize the aberra-tion of some features while distortingothers beyond recognition. The choice SCIENTIFIC AMERICAN March 1993 79ùCopyright 1993 Scientific American, ... the tension in the spring. The tension, in turn, equals the sum of the two forces acting on the weight: the gravitational force and the centrifugal force.To measure either one of these forc-es ... ArthurStanley Eddington conÞrmed this pre-diction by measuring the minute deßec-tion of rays passing close to the sun. The gravitational Þeld of the sun willbend a light ray less than one thou-sandth...
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scientific american - 1993 04 - controlling the quantum jitters of atoms
... fund-raising. He current-ly counts 230 individual contributors,including one person whose donation is contingent on the condition that Gehr-els not tell the donorÕs wife where the money is ... nonstationary onesÑaddition of the nonstationary states correspondsto the in-phase oscillation mode of the two-pendulum model, and subtrac-tion of the states corresponds to the SCIENTIFIC AMERICAN ... one, the atom is excited, but there is nophoton in the cavity (left and right). In the other, the atom is de-excited, and the cavity contains a photon (center). The atomand the cavity continually...
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scientific american - 1993 05 - building soft machines from smart gels
... that the pion is responsible only for conveying the nuclear force overlong distances. And no one has figured out what is happen-ing over the short range.To be sure, a vast distance in this context ... context is, by any con-ventional scale, close to nothing. Because the diameter of aproton is only one fermi—that is, a millionth of a billionthof a meter—nuclear physicists consider a distance ... presenttime, the eÝect is greatest on the sur-face, and decreases with depth. Directuse of the high-speed electrons from the betatron may be even more valu-able than the use of the X-rays. Most ofthe...
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scientific american - 1993 06 - tuning in the radio signals of ancient galaxies
... demon-strated in the laboratory. The EPR phenomenon is the linchpin of quantum teleportation. Alice takesone of the EPR photons and gives the other to Bob. Bob then moves to an-other location ... polarization—of one photon is up fixes the polarization of the other photon into the opposite direction, or down. The effect, which is instantaneous no matter what the distance between the photons, emerges ... chro-mosome in SCID.They decided to test the hypothesis that defects in the gam-ma-chain gene were causing the im-munodeficiency. With the further assis-tance of Howard M. Rosenblatt of the Baylor...
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scientific american - 1993 07 - telling resonable risks from fools' chances
... 01111 1101 0000 100 0 0100 1100 0 010 0 110 1 110 1 010 0001 100 1 0101 1101 0011 01111111 101 1a b c dCopyright 1993 Scientific American, Inc. the population would change radically: the expansive force of mutation ... wereconfused and that their opinions shouldbe discounted.Since then, social scientists have con-ducted extensive studies of public riskperception and discovered that the sit-uation is considerably ... hold onlyabout 10 108of them. Hence, an array of 10 6,000diÝering RNA sequences is be-yond comprehension.Fortunately, it is not beyond the ana-lytic reach of mathematics. We can con-struct...
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scientific american - 1993 08 - can particles move faster than light
... tortoises: one that is reßect-ed back toward the start and one thatcrosses the barrier. These two partialtortoises together represent the prob-ability distribution of a single photon.When the ... photon is detected at one po-sition, its other partial tortoise instant-ly disappears. The reßected tortoise is bigger than the tunneling tortoise sim-ply because the chances of reßection aregreater ... Eachrepresents the probability distribution of the position of a pho-ton. The peak is where a photon is most likely to be detected. The tortoises start together (left). Tortoise 2 encounters a bar-rier...
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