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Power

Home Wind-Power Turbines Make Headway 163

Pickens writes "Wind turbines, once used primarily for farms and rural houses far from electrical service, are becoming more common in heavily populated residential areas as homeowners are attracted to ease of use, financial incentives and low environmental effects. Experts on renewable energy say a convergence of factors, political, technical and ecological, is causing a surge in the use of residential wind turbines, especially in the Northeast and California. "Back in the early days, off-grid electrical generation was pursued mostly by hippies and rednecks, usually in isolated, rural areas," said Joe Schwartz, editor of Home Power magazine. "Now, it's a lot more mainstream." Some of the new "plug and play" systems can be plugged directly into a circuit in the home electrical panel and homeowners can use energy from the wind turbine or the power company without taking action. Schwartz says that even with the economic benefits, it can take 20 years to pay back the installation cost. "This isn't about people putting turbines in to lower their electric bills as much as it is about people voting with their dollars to help the environment in some small way," he said."
Math

Submission + - Wolfram awards $25,000 for flawed proof

An anonymous reader writes: Slashdot readers will have seen an announcement by Stephen Wolfram offering a $25,000 prize for a proof or a disproof that a certain 2-state, 3-color Turing machine is universal. The prize was awarded on October 24th, 2007 to Alex Smith of Birmingham, UK.

However, according to discussion in the Foundation of Mathematics e-mail list, archives of which are available here, the members of the prize committee were "informed but not polled" as to the validity of the proof. The prize committee members were Lenore Blum, Greg Chaitin, Martin Davis, Ron Graham, Yuri Matiyasevich, Marvin Minsky, Dana Scott and Stephen Wolfram. On October 26, Martin Davis wrote to the FOM list that "The determination that Smith's proof is correct seems to have been made entirely by the Wolfram organization. My understanding is that the I/O involves complex encodings."

On October 29th, Stanford computer scientist Vaughan Pratt wrote to the Foundations of Mathematics list that the universality proof of the (2,3) Turing machine was flawed, asking "How did an argument containing such an elementary fallacy get through the filter?" Pratt points out that the fallacy of the proof could be used to "prove" the erroneous statement that a linear bounded automaton is universal. The text of Pratt's email is available here.

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