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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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Cosmic Power Producers
21 March 2000 6:00 pm
Never say that cosmologists are impractical. Two have invented a scheme for making the most efficient engine yet envisioned--a black hole engine.
Black holes, which are collapsed stars, qualify as engines because they convert matter into energy: Matter speeds up and radiates high-energy light as gravity causes it to plunge from a spinning disk into the hole. In 1974, physicist Kip Thorne of the California Institute of Technology showed that about 31% of the infalling mass is converted to usable energy. The rest is lost, as it goes into increasing the size of the hole.
For years, physicists were unable to figure how black holes could burn energy more efficiently than Thorne's calculations suggested. Now Princeton physicist Bohdan Paczynski and student Li-Xin Li have come up with a better model: A black hole that is, in effect, a two-cycle engine.
First, says Paczynski, you let matter fall into the black hole as Thorne did in his calculations. But then, as the infalling matter causes the black hole to spin faster, you stop feeding in the matter. The hole's magnetic field then increases the speed of the whirling disk, extracting another dollop of energy. "By magnetic coupling [of the hole] to the nearby disk, energy extraction from the spinning black hole can be made even more efficient," says Paczynski, who notes that the efficiency is now a whopping 43%.
The duo have posted a paper describing their improved black hole at Los Alamos National Laboratory's preprint server. But don't expect to get a car running on more miles per matter anytime soon. "There are no specific applications," says Paczynski. "It's just a mental exercise."