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Building New Materials With Light 27

ckwu writes "Since the 1970s, physicists have used laser beams to trap and study small objects, from cells down to individual atoms. Now, electrical engineers at the University of Southern California have developed a simple optical system that assembles hundreds of nanoparticles into two-dimensional structures using a single laser beam and a silicon photonic crystal. This compact optical trap fits on a small chip and could eventually help researchers make materials for new types of sensors, optical devices, and chemical filters."

NASA's Fermi Spacecraft Dodged a Defunct Russian Satellite 47

g01d4 writes "On March 29, 2012, NASA scientists learned that the space agency's Fermi Gamma-ray Space Telescope was headed for a potential conjunction (close approach) with Cosmos 1805, a defunct Russian satellite from the Cold War era. The team knew that the only way to move Fermi would be to fire thrusters designed to move the spacecraft out of orbit at the end of its operating life. On April 3rd, shortly after noon EDT, the space agency fired all thrusters for one second. When it was over, everyone involved 'just sighed with relief that it all went well.' By 1 p.m., the spacecraft had returned to its mission."

Physicists Attempting To Test 'Time Crystals' 231

ceview writes "This story at Wired seems to have lots of people a bit confused: 'In February 2012, the Nobel Prize-winning physicist Frank Wilczek decided to go public with a strange and, he worried, somewhat embarrassing idea. Impossible as it seemed, Wilczek had developed an apparent proof of "time crystals" — physical structures that move in a repeating pattern, like minute hands rounding clocks, without expending energy or ever winding down. ... [A] Berkeley-led team will attempt to build a time crystal by injecting 100 calcium ions into a small chamber surrounded by electrodes. The electric field generated by the electrodes will corral the ions in a "trap" 100 microns wide, or roughly the width of a human hair. The scientists must precisely calibrate the electrodes to smooth out the field. Because like charges repel, the ions will space themselves evenly around the outer edge of the trap, forming a crystalline ring.' The experimental set up is incredibly delicate (Bose Einstein Condensate), so it implies this perpetual motion effect can't really be used to extract energy. What is your take on it? It's unlike to upend anything, as the article suggests, because at a quantum level things behave weirdly at the best of times. The heavy details are available at the arXiv."

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