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5 December 2013 11:26 am ,
Vol. 342 ,
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Atom Waves Could Detect Oil Pools
29 July 1998 7:30 pm
Gravity may be the law of the land, but the force it applies varies slightly depending on the rocks beneath our feet. In the 3 August Physical Review Letters, researchers report that they have devised a sensitive new scheme for mapping these variations that relies on the quantum mechanical nature of atoms. The device could eventually be useful for searching out new oil and gas deposits, which can be revealed by tiny gravity anomalies.
The scheme builds on the bizarre dual nature of matter, which behaves--so says quantum mechanics--as solid particles at some times while resembling light waves at others. Instruments called interferometers split light waves, allow them to travel separately for a distance, and then recombine them. The result is a shadowy interference pattern, created because waves that converge in phase create light patches and those that cancel each other out form dark areas. In 1991, physicists showed that "matter waves" of atoms can produce the same effect. Typical atom interferometers work by dropping a collection of ultracold cesium atoms down a vacuum tube while pushing them apart and then back together with laser pulses. Gravity, by acting on the cesium atoms, affects the interference between the moving "atom waves."
In the new experiment, Yale University physicist Mark Kasevich and his colleagues stacked one atom interferometer atop another in order to measure the difference in gravity's pull between them. Using two interferometers allowed the researchers to pick out and throw away distorting effects, such as vibrations, that affected both devices equally. By comparing the results between the two interferometers, the researchers were able to gauge changes in the pull of gravity as small as one part in 10,000,000, a number they have since honed to 30 parts in a billion.
The new work is "a beautiful experiment," says Daniel Kleppner, an atomic physicist at the Massachusetts Institute of Technology. For now the new interferometer-based gradiometers are still not as accurate as the mechanical gradiometers used to look for oil and gas deposits, among other things. Part of the trouble, says Yale team member Jeff McGuirk, is that some vibrations can cause the laser pulses to travel a different path through one interferometer than the other, adding background noise to the experiment. But McGuirk adds that the group has already tested a scheme for compensating for the vibrations, which should improve the sensitivity by another factor of 100 to 1000, good enough to beat the competition.