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| 11/22 |
| 2005/10/10-11 [Science/GlobalWarming] UID:40036 Activity:high |
10/10 Last week's Economist had an article on using man-made, controlled
tornados for power. I just thought it was interesting after our
discussion on using hurricanes for power. Unfortunatly, the
economist link doesn't seem to work, but I got this on google:
<DEAD>www.gi.alaska.edu/ScienceForum/ASF1/105.html<DEAD>
\_ http://www.economist.com/science/displayStory.cfm?story_id=4455446
\_ How long will it take Michael Crichton to write a book saying
how this will destroy the world?
\_ Probably right after the bird flu novel. Has he written the
global warming novel yet?
\_ You mean you missed it? He wrote a whole book about how
global warming was an environmentalist plot to take over
the world or something. And I don't think he was kidding.
\_ Crichton wrote a book on how global warming was overhyped,
and that the real danger to the world was crazed
environmentalists. I think he was called to testify in front
of a congressional committee about global warming recently?
He's got a medical degree but I still think it was lame. - danh
\_ I've never read a Crichton book. Sounds like I should
start though.
\_ The good and bad thing about Crichton books is that they
read *exactly* like movies. I find that after I've read
a Chrichton book, I literally can't remember whether I
saw the movie or read the book. Great for a plane, and
worthless for anything else.
\- [thread branch] In re: the motd thread about
the anthropic principle some time ago, there is
an article in the latest e'ist about a new proposal
in m-theory to explain the "3 dimension bias":
http://csua.org/u/don
it is co-authored by lisa randall who is fmr
lbl and whose sister some of you may know from
ucb cs. |
| 11/22 |
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| www.economist.com/science/displayStory.cfm?story_id=4455446 Science & Technology Alternative energy The power of spin Sep 29th 2005 From The Economist print edition Harnessing artificial tornadoes as an energy source WEATHER systems, as the world has recently been reminded, have awesome po wer. The energy released by a large hurricane can exceed the energy cons umption of the human race for a whole year, and even an average tornado has a power similar to that of a large power station. If only mankind co uld harness that energy, rather than being at its mercy. Louis Michaud, a Canadian engineer who works at a large oil company, believes he has de vised a way to do just that, by generating artificial whirlwinds that ca n be controlled and harnessed. His idea works on a similar principle to a solar chimney, which consists of a tall, hollow cylinder surrounded by a large greenhouse. The sun hea ts the air in the greenhouse, and the hot air rises. A turbine at the base of the chimney generate s electricity as the air rushes by. A small solar chimney was operated s uccessfully in Spain in the 1980s, and EnviroMission, an Australian firm , is planning to build a 1,000-metre-high example in New South Wales. Bu t the efficiency of such a system is proportional to the height of the c himney, notes Mr Michaud, which is limited by practical considerations. His scheme replaces the chimney with a tornado-like vortex of spinning a ir, which could extend several kilometres into the atmosphere. This vortex would be produced inside a large cylindrical wall, 200 metres in diameter and 100 metres tall. Warm air at ground level enters via ta ngential inlets around the base of the wall. Once established, the heat content of the air at ground level is enough to keep the vortex going. As the air rises, it ex pands and cools, and water vapour condenses, releasing even more heat. T his is, in fact, what powers a hurricane, which can be thought of as a h eat engine that takes in warm, humid air at its base, releases cold, wat ery air at the top of the troposphere, about 12 kilometres up, and liber ates a vast amount of energy in the process. The intensity of the vortex would be controlled by closing the inlets around the base, or by opening anoth er set of inlets to inject air in the opposite direction and so slow the vortex's rotation. And, of course, there would be a set of turbines at the base of the vortex that would allow its energy to be harnessed as ai r rushed through the inlets. Mr Michaud estimates that an atmospheric vo rtex engine with a diameter of 200 metres would produce around 200 megaw atts of power. And if it did, could the resulting vorte x really be controlled? Mr Michaud admits that the word tornado tends to worry people. This summer, 30 years after he had the original idea, a nd having failed to convince his employer or any other energy firm to ta ke it on, he began tests at a site in Utah, with a cylindrical wall 10 m etres in diameter. His initial aim is to demonstrate that artificial vor tices can indeed be created and controlled. The next phase, he says, wou ld be to modify a cooling tower at an existing power station so that it uses a spinning vortex rather than the usual large fans to generate the necessary airflow within. The final step would be to add turbines to ext ract energy from the vortex. Besides the engineering challenges involved, Mr Michaud must navigate the cultural divide between atmospheric scientists and the weather-modifica tion community. The scientists regard the weather-modification crowd as cranks. They, in turn, cannot understand why the scientists are not taki ng a more hands-on, experimental approach to understanding the weather, rather than simply observing and modelling it. Mr Michaud has published nine papers in atmospheric-science and meteorology journals, and says hi s invention relies on principles that are consistent with scientists' cu rrent understanding of how natural weather systems work. |
| csua.org/u/don -> www.economist.com/science/displayStory.cfm?story_id=4484326 Science & Technology Cosmology A braney theory Oct 6th 2005 From The Economist print edition An explanation for the anthropic principle comes a little closer DID God have a choice? Or, to put the matter less theologically, does the universe have to be the way that it is? The answer to this question, po sed by Einstein among others, remains elusive. But it is important, not least because a universe with laws only slightly different from those ac tually observed would be one in which lifeand therefore human lifecoul d never have come into existence. That observation, known as the anthropic principle, disturbs many physici sts because they cannot see any fundamental reason why things could not be different. In particular, they cannot see why space has to have three dimensions. But a paper due to be published this month in Physical Revi ew Letters by Andreas Karch of the University of Washington and Lisa Ran dall of Harvard University suggests that the laws of physics may, indeed , be biased towards three-dimensions. Curiously, though, they have a sim ilar bias towards seven-dimensions. The idea that there may be more dimensions than the familiar ones of leng th, breadth and height (and also, to be strictly accurate, the fourth di mension of time) is a consequence of attempts to solve an old problem in physics. Ever since Einstein developed his theories of space, time and gravity, physicists have sought a theory of everything that would unit e those theories with quantum mechanicsthe part of physics that describ es electromagnetism and the forces that hold atomic nuclei together. Suc h a theory would, it is hoped, describe how the universe developed from the Big Bang. It would explain why there appears to be more matter than anti-matter. It would even indicate the nature of the dark energy and da rk matter that lurk at the edge of perception. To date, the best candidates for a theory of everything are various versi ons of a branch of mathematics called string theory. Unfortunately for c ommon sense, these theories require the universe to have ten or even 11 dimensions rather than the familiar three of space and one of time. To g et round this anomaly, some physicists propose that the familiar dimensi ons are unfurled, while the other six or seven are rolled up so tightl y that they cannot be seen, even with the most powerful instruments avai lable. Only under a magnifying glass are t he other two dimensions perceptible. A second interpretation of multidimensionality, however, is that the extr a dimensions are not always rolled up, but that even when they are not h umans cannot readily observe them because they are not free to move in t hem. In this version, the space inhabited by humans is a three-dimension al surface embedded in a higher dimensional landscape. The particles o f which people are composed, and the non-gravitational forces acting on them, are strictly confined to this surfacecalled a brane (short for me mbrane)and, as such, have no direct knowledge of the higher dimensional space around them. Only gravity is free to pervade all parts of the uni verse, which is one of the reasons why it obeys a different set of rules from the other forces. It is this second interpretation that is invoked by Dr Karch and Dr Randa ll. They assume that, initially, the universe was filled with equal numb ers of branes and anti-branes (the antimatter equivalent of a brane). Th ese branes and anti-branes could take any number of up to ten different dimensions. Dr Karch and Dr Randall then demonstrated, mathematically, t hat a universe filled with equal numbers of branes and anti-branes will naturally come to be dominated by 3-branes and 7-branes because these ar e the least likely to run into their anti-brane counterparts and thus be annihilated. It is the first piece of work to show that branes alone can explain the existence of hidden dimension s They do not have to be rolled up to be inaccessible. It is also the f irst to suggest an underlying preference in the laws of physics for cert ain sorts of universe, and thus perhaps provide a solution to the anthro pic principle. Other realities, whether three- or seven-dimensional, could be hidden elsewhere in the landscape. And life in seven-dimensional space would look very different from life on Earthif, indeed, it existed at all. That is because the force of gr avity would diminish far more quickly with distance than it does in this world. As a result, seven-dimensional space could not have planets in s table orbits around stars. Like dark matter and dark energy, therefore, the anthropic principle is still grinning from the sidelines, taunting p hysicists to explain it. |