Word: cesium
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Dates: during 1990-1999
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...reactors full of nuclear fuel, sank accidentally. The most dangerous, the world was reminded last week, may be the Komsomolets, which caught fire in April 1989 and went down in more than 4,500 ft. of water 310 miles off the coast of Norway. The wreck is already leaking cesium-137, a carcinogenic isotope. So far the leakage is considered too small to affect marine life or human health...
...principle behind all this precision comes from quantum physics. When an atom is bombarded with electromagnetic radiation -- in this case microwaves -- it shifts into a new energy state. Each type of atom responds most readily to a particular frequency. For the cesium-133 atoms in most atomic clocks, the frequency is 9,192,631,770 vibrations per second. When a microwave beam inside the clock is set to that frequency, the maximum number of atoms will undergo the energy switch, signaling the clock's internal computer that the device is correctly tuned. The vibrating microwaves keep time; the atoms just...
Theoretically, an atomic clock could keep perfect time; the actual performance, though, depends on the electronics and such engineering details as how the microwaves hit the cesium atoms. Hewlett-Packard will doubtless come up with other refinements, but for now losing a second every 1 1/2 million years will have...
They are the best thing to happen to pure carbon since the diamond: 60-atom molecules that are neither pyramid shape (like diamonds) nor hexagonal (like graphite) but spherical, like soccer balls. Captured for the first time in 1991 in computer-generated "snapshots" (seen here with cesium-based handles -- the rabbit ears on top), these namesakes of Buckminster Fuller might someday be fashioned into tiny ball bearings, featherweight batteries or even superconducting wires that are just one molecule thick...
...properties. Certainly, cold atoms can be trapped and manipulated in a variety of cunning ways. The fountains created by Chu, for example, are enabling scientists to observe atoms in free fall and thus measure gravitational force with unprecedented accuracy. Fountains are also helping scientists measure the oscillations of cesium atoms more precisely than ever before, and cesium atoms are to atomic clocks -- the world's most precise timepieces -- what quartz crystals are to wristwatches...