Archived Pages from 20th Century!!
In the April issue of Physics Today the authors Heinrich Jaeger, Sidney Nagel, and Robert Behringer explain: Consider sand contained in a tall cylinder. The pressure in the cylinder does not increase indefinitely with depth, as it does in ordinary fluids. Rather, the pressure does not exceed a certain maximum value because the contact forces between grains and friction between grains and the walls cause part of the weight of the overlaying material to be imparted to the walls. Another property which sets granular materials apart from other fluids is the tendency (in a vibrated tank containing particles of differing sizes) for the larger objects to float to the top regardless of their density. Part of the reason for this is that the smaller particles fall into the voids between the larger particles, making it difficult for the larger ones to move downwards (especially along the walls) as part of a convective flow.
The properties of granular media in technological issues is clear, as in packaging, mixing, sifting, mining, and erosion processes, but the universe itself may exhibit a sort of granular arrangement. One simulation of granular gases involving a large sample of inelastically interacting hard disks resulted in the "inelastic collapse" of the system into a foam of chainlike structures roughly resembling the distribution of galaxies in the cosmos. The Physics Today authors speculate that the role of gravity in shepherding galaxies may be analogous to the role played by container walls in shaping granular fluids into clusters. At the cosmological level, the "grains" would be stars and galaxies.
From the Editor: Easter Egg Surprise!
Armchair Scientist: a Proposal
This new e-magazine has two goals: to present scientific results and achievements in an attractive and unimposing way and, at the same time, to stimulate the quest for a new way to do science in spite of the deluge of information going on in our society.
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for Next Issue ARMCHAIR-SCIENCE
mirror at Video On Line versione italiana
The first direct image of the surface of a star
Deepest-ever view of the Universe
Tether physics explained
Scanning Tunneling Microscopy: Quantum Corrals
Angry debate on Nanotechnology: Ralph Merkle vs. SciAm
Preliminary data from Galileo probe
and more: The earth slowed down by Galileo probe! - Cyberaddicts - The Visible Woman on the Web - Cold Fusion in Italian Court - Did neutrinos kill the dynosaurs? - 10000 tons of interplanetary dust particles -
Personal Area Networks (intra-body communications)
Earth-To-Orbit Transportation (28 methods!)
Advanced Photo System (revolution in photography)
Don't catch that plane! (danger from software chaos)
and more: Micromachined ultrasonic transducers - Planar display expands viewing area - Revolutionary X-Ray instrument - DVDs, next generation of laser disks - White House plans for HDTV - Computer companies against digital TV standard
Revolutionary advancements in particle physics research:
Tabletop laser accelerators - Crystal beam deflectors for 900 GeV particles - The first X-Ray hologram with atomic resolution
Zoom in on atoms and molecules:
Sensing technique sheds light on atomic motion - Single molecule biosensors
Why water shrinks when warmed?
In this issue a very clearly written article, "Beyond Einstein" by
David de Hilster, will introduce you to Autodynamics.
e-magazine: New Scientist - Planet Science
mail-list: Popper - Philosophy of Science
mail-list: Debono - Lateral Thinking
mail-list: Inventors - Ideas Development and Patenting
resources: My Virtual Encyclopedia - Virtual Facts
resources: Fractal Zoom, Eloisa-Virtual Personality, Virtual Geomorphology
conference: Space Time Information
conference: Intelligent User Interfaces
seminar: Human Science Research