Global potential for wind-generated electricity Xi Lua, Michael B. McElroya,b,1, and Juha Kiviluomac aSchool of Engineering and Applied Science, Cruft Lab 211, and bDepartment of Earth and Planetary Sciences, Harvard University, 100E Peirce Hall, 29 Oxford Street, Cambridge, MA 02138; and cVTT Technical Research Centre of Finland, P. O. Box 1000, 02044 VTT, Finland Communicated by James G. Anderson, Harvard University, Cambridge, MA, April 29, 2009 (received for review November 6, 2008) The potential of wind power as a global source of electricity is assessed by using winds derived through assimilation of data from a variety of meteorological sources. The analysis indicates that a network of land-based 2.5-megawatt (MW) turbines restricted to nonforested, ice-free, nonurban areas operating at as little as20%of their rated capacity could supply >40 times current worldwide consumption of electricity, >5 times total global use of energy in all forms. Resources in the contiguous United States, specifically in the central plain states, could accommodate as much as 16 times total current demand for electricity in the United States. Estimates are given also for quantities of electricity that could be obtained by using a network of 3.6-MW turbines deployed in ocean waters with depths <200 m within 50 nautical miles (92.6 km) of closest coastlines.

We have discovered distinctive red/gray chips in all the samples we have studied of the dust produced by the destruction of the World Trade Center. Examination of four of these samples, collected from separate sites, is reported in this paper. These red/gray chips show marked similarities in all four samples. One sample was collected by a Manhattan resident about ten minutes after the collapse of the second WTC Tower, two the next day, and a fourth about a week later. The properties of these chips were analyzed using optical microscopy, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (XEDS), and differential scanning calorimetry (DSC). The red material contains grains approximately 100 nm across which are largely iron oxide, while aluminum is contained in tiny plate-like structures. Separation of components using methyl ethyl ketone demonstrated that elemental aluminum is present. The iron oxide and aluminum are intimately mixed in the red material. When ignited in a DSC device the chips exhibit large but narrow exotherms occurring at approximately 430 °C, far below the normal ignition temperature for conventional thermite. Numerous iron-rich spheres are clearly observed in the residue following the ignition of these peculiar red/gray chips. The red portion of these chips is found to be an unreacted thermitic material and highly energetic.

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* How can a boat sail upwind? * How can boats sail faster than the wind? * Why are eighteen foot skiffs always sailing upwind? We introduce the physics of sailing to answer these and some other questions.

Fast Track Communications (FTCs) are defined as outstanding short papers reporting new and timely developments in mathematical and theoretical physics. These high-quality articles will be of importance to readers of Journal of Physics A: Mathematical and Theoretical but are not expected to meet any criterion of `general interest'. Conjectural articles are welcomed. FTCs will be processed quickly and are available free to readers in the electronic journal.

Reports by FEMA and NIST lay out the official account of the destruction of the World Trade Center on 9/11/2001. In this Letter, we wish to set a foundation for productive discussion and understanding by focusing on those areas where we find common ground with FEMA and NIST, while at the same time countering several popular myths about the WTC collapses.