Word: thorium
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...Cancún on the east coast of Mexico's Yucatan peninsula. (The fossils had been exposed during the construction of a new seaside resort.) Working with his co-authors at Germany's Leibniz Institute of Marine Science, Blanchon calculated the age of the samples by measuring isotopes of thorium in the fossils, a process similar to carbon-dating. The patterns of the fossils indicated points where the coral died when the seas rose too fast for the organisms to adapt; each time the seas stabilized, the corals grew back, but at higher elevations and further inland, a process geologists...
...help the nation kick its foreign oil habit. Opponents point out that almost all uranium mining in the United States occurs in arid, sparsely populated places out west that are geologically unlike anything in Virginia. In the water-rich Old Dominion, they argue, radioactive materials from uranium such as thorium-230, radium-226 and radon-222 could shake loose and leach into the groundwater. Meanwhile, the large piles of mining debris known as "tailings" could blow in the wind and contaminate the air. "It's going to rain down dust like lint," predicts 57-year-old cattle farmer and mine...
...into his head in high school to build a nuclear reactor in his mom's potting shed, and damn if he didn't come close. In The Radioactive Boy Scout (Random House; 209 pages), Ken Silverstein describes how Hahn extracted radioactive elements from household objects--americium from smoke detectors, thorium from Coleman lanterns, deadly radium from the glow-in-the-dark paint used on the hands of vintage clocks. For sheer improvisational ingenuity, Hahn makes MacGyver look like Jessica Simpson. When public-health officials finally caught on to what Hahn was up to, the potting shed...
...between 8 billion and 12 billion years. But other experts insisted they knew of stars that were at least 14 billion years old--obviously a problem, since stars can't be older than the cosmos. Using the VLT, though, observers have measured minute traces of radioactive uranium and thorium in the oldest stars--a technique akin to radiocarbon dating--and proved that they're more like 12 billion years old (the age of the universe, meanwhile, is now estimated at 14 billion years...
...Uranium-thorium has another advantage besides accuracy: it can be used to date objects up to 500,000 years old, while carbon 14 is good for only a few tens of thousands of years at best. The one drawback of the uranium-thorium technique is that it is useful mostly for marine animals and plants; uranium is more common in seawater than on the surface of the land. Scientists will no doubt continue to use all possible dating methods in the quest to construct an ever more accurate chronology of the earth's history...