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5 December 2013 11:26 am ,
Vol. 342 ,
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...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
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,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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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."