“Castles in the Air” left the false impression that high-rise buildings are inherently “green” and essential to making cities more sustainable. Compared with lower-rise construction, they require more energy, and their wind tunnels and long shadows diminish livability. Whereas cities do need minimum corridor and neighborhood densities to support their pedestrian and transit-based economies, an occasional high-rise barely makes a dent. Lacking definitive research on the optimal scale of a sustainable city, I’ve nonetheless made informal surveys of expert colleagues that suggest that four to 30 stories is the optimal range for buildings in a sustainable city.
Doug Farr
President, Farr Associates
Chicago
SIMPLE SECURITY
David Pogue is correct in “Password Prevented” [TechnoFiles] that our current method of making passwords is the worst of all possible worlds; it creates passwords that are nearly impossible for a human to remember but still relatively easy for a computer to guess.
The true secret to security is the reverse: a password scheme that is easy for users to remember (so they don’t write it down) but close to impossible for a computer to guess. The method of picking a string of letters and numbers gives a result that could be beaten in about three days of determined effort and is pretty much impossible to remember. A phrase of four random words, however, can be easy to remember but can require more than 500 years to guess.
Andrew Bennett
Belmont, Mass.
POVERTY PRIORITY
Edward Glaeser’s point that education matters more to the health of a city than construction and transportation projects in “Brains over Buildings” is valid but superficial. For a poor, urban community of color to prosper—or, nowadays, survive—good education that’s free and relevant is essential. But people need to eat, too.
The trouble with urban development is that the contractors and workers almost never come from the community being developed. And the article doesn’t mention the barriers erected in the past few years to accessing the two things it touts: education and entrepreneurship. Even San Francisco City College is too expensive for most people in the city’s neighborhood of Hunter’s Point, and cutbacks to faculty and classes make it futile for many. We’re all for entrepreneurship, but what about redlining, which has gotten worse and is augmented by predatory loans that are nothing but landgrabs? And try running a business without money.
Further, a metric Glaeser ignores is the rich, who have education and entrepreneurship in abundance, pushing the poor out of the cities altogether.
If the poor see that education will get them somewhere and help them feed their families, they and their kids will go for it. Otherwise, what’s the point?
Mary Ratcliff
Editor, San Francisco Bay View
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Add CommentFinally, with the publication of Luke Bisby's letter, Scientific American has dared to touch (however obliquely) the scientific question of what happened to cause three steel superstructure buildings to collapse on September 11th of 2001. The official pronouncements from our government are that somehow three steel frame buildings of two different construction designs collapsed completely and symmetrically due to fires on that day. They were--supposedly--the first three steel superstructure buildings ever to completely collapse due to fire.
Reply | Report Abuse | Link to thisWith the collapses of the twin towers we are asked to believe that buildings damaged high up in the structure could burn for an hour to an hour and a half and then collapse completely to the ground at or near free fall speed. This would mean that each of the 47 huge steel columns in the center of the building for all those lower floors--undamaged by either the airplane crash or the fire--snapped on each floor in anticipation of the falling debris, otherwise the resistance from these central columns would certainly have slowed (and probably stopped) the collapses. And, they all had to snap simultaneously on each floor because otherwise the collapse would have been asymmetrical.
Of course, Building 7--the third building that fell that day--also collapsed absolutely symmetrically and for at least eight floors fell at free fall speed. Supposedly, this building also fell because of the effects of fire on a single column. However, the government's report stops short of saying how a collapse of a single column could lead to the instantaneous collapse of all the columns on eight floors of the building.
After over a decade of silence on this issue--to disastrous effect to our political and economic environments--Scientific American should bring this issue into the light. Mr. Bisby is absolutely correct in saying architects and engineers should face up to this issue. What Mr. Bisby and Scientific American fail to mention is that over 1,600 architects and engineers have indicated that there is no way that fires brought down these buildings. This magazine should be at the forefront in demanding a scientific investigation into the causes of these collapses, not bringing up the rear. It's just like Galileo all over again, Scientific American can either side with science or with the dictates of the political authorities of our time. It's way past time that the magazine spoke up for science.
What is absurd is the belief that the three WTC buildings collapsed due to fire. So far, I have seen no evidence to support this outlandish claim, but have seen over a thousand architects and engineers sign a petition sighting the obvious flaws in such an account and demanding a new explanation.
Reply | Report Abuse | Link to thisChief among the multitude of attributes of the collapses that point to explosive demolition is the free-fall, symmetrical collapse of WTC 7. Fire cannot achieve this, but I would expect Un-Scientific American to recognize this simple fact.
Additionally, fires have occurred that burned longer and hotter in a myriad of other steel framed skyscrapers (including, ironically, the WTC) none of which resulted in sudden, progressive collapses.
Well, I can't top the comments left by Andy Swamp and Uncle Joe, but I thought I'd offer them my support. One day, the real truth about what really happened on 9/11 WILL come out, and people like Luke Bisby and organizations like Scientific American will one day be regarded much the same way as we now regard the people who opposed Galileo. First, the fires were not "uncontrolled" nor were the buildings a raging inferno. Most of the jet fuel was gone in the initial fireball, and the fires were mostly smoke (indicating a cool oxygen-starved fire). Burning furniture, office equipment, etc. is not going to cause a skyscraper to completely explode.
Reply | Report Abuse | Link to this9/11 is a wake up call to just how the govt can deceive the people and tightly control the media, even in a supposedly "free" society with an "open press."
Matt, Scientific American and Popular Mechanics - along with the world's media which shamefully self-censors this story - already look bad because they fail to grasp Newtonian physics our grade-school physics students can grasp.
Reply | Report Abuse | Link to thisThe Laws of Conservation mean that the Towers could not have totally dismembered in 11 seconds without any resistance - absent an extra energy force.
The Towers - with dozens of massive cold steel columns in the bottom two-thirds of the structure - were shredded and pulverised in the time it takes to clap your hands 11 times.
Then you have Building Seven, not hit by a plane, imitating a text-book implosion in the time it takes for your phone to ring three times. If random, asymetrically burning fires on a limited number of floors can sink a building symmetrically into its own footprint, then why has the world wasted time on expensive demolition companies for decades? Set the office furniture on fire, wait a couple of hours and voila! Global, vertical, rapid implosion. All Demolition Companies out of business forthwith.
The problem for America and Scientific American is that many rational people in the rest of the world, those with basic science and physics under their belts, are shaking their heads in astonishment and sadness at the ignorance and naivete on display. Wondering when Mickey Mouse and Daffy Duck are going to grow up and apply their minds to the scientific method.
The United States Department of Commerce NIST report is a political - not scientific - document.
Read "The Mysterious Collapse of Building Seven: Why the Official Report is Unscientific and Fraudulent" by Dr David Ray Griffin. The physics teacher at our kids' school has read it, digested it and is using the WTC building implosions as a successful teaching tool for the Newton module.
There have been thousands of fires in highrises all over the world, turning many of them into raging infernos, but only three steel-framed highrises have totally collapsed - all at the WTC.
Reply | Report Abuse | Link to thisWhatever the precise cause of the total destruction of the third skyscraper, WTC 7, its demise would amount to probably the most perfect controlled demolition in human history.
Many controlled demolitions have failed, as all columns throughout a couple of floors need to be destroyed within a fraction of a second. As a result of mistimed or partially failing explosions, some buildings have only descended a couple of floors until the intact structures have arrested the descent, and some buildings have fallen to one side. Reducing a highrise to a rubble pile is a highly challenging, skill-demanding task.
However, fire alone accomplished this for WTC 7, a modern, 47-storey highrise.
In light of this, it is utterly amazing that, according to NIST, all the research material was destroyed without investigation: "No metallography could be carried out because no steel was recovered from WTC 7."
Jim Hoffman, who contributed to Scientific American in the past, writes on wtc7.net:
"Being the only such building in history in which fire is blamed for total collapse, Building 7's remains warranted the most painstaking examination, documentation, and analysis. Building 7's rubble pile was at least as important as any archeological dig. It contained all the clues to one of the largest structural failures in history."
We know that over the years, NIST came up with different "interim hypotheses" about the cause of the destruction. Why weren't they allowed to examine the steel debris to determine why and how the skyscraper was destroyed?
After publishing their draft for final report in 2008, NIST lead WTC investigator Shyam Sunder said that WTC 7 could not have collapsed at free fall acceleration, as crushing structures necessarily takes time and slows down the descent. However, after a physics teacher demonstrated that WTC 7 did in fact descend at free fall acceleration for over 2 seconds, NIST concluded in their final report that "a freefall descent over approximately eight stories at gravitational acceleration" took place, without explaining how this could happen.
Following Luke Bisby's advice, it is indeed high time to take a real scientific look into the total destruction of WTC 7 and the Twin Towers. Over 1,600 architects and engineers, among others, have already paved the way for this - google "Architects and Engineers for 9/11 Truth".
Scientific American has dared to touch (however obliquely) the scientific question of what happened to cause three steel superstructure buildings to collapse on September 11th of 2001.
Reply | Report Abuse | Link to thisAccording basic structural damage analysis no structure of any kind can be crushed by gravity by its top! See http://heiwaco.tripod.com/tower.htm .
The writer is well established engineer and offers €1M to anybody showing that ge is wrong! See http://heiwaco.tripod.com/chall.htm .
We know what happened to the Twin Towers, buildings 1&2, and building 7, what of buildings 3,4,5 & 6 of the same complex?
Reply | Report Abuse | Link to thishttp://www.ae911truth.org/en/news-section/41-articles/440-1000-words.html
Nanothermite cannot be made in a cave, nor did the alleged perpetrators have access to the buildings in order to place it.
http://www.benthamscience.com/open/tocpj/articles/V002/7TOCPJ.htm
Please see if you can detect deception in this 2 min. video, and if so take appropriate action for yourself, your family, your nation and the future of our shared world. Thank you.
http://www.youtube.com/watch?v=fs_ogSbQFbM&feature=plcp&context=C35e3dd5UDOEgsToPDskJAL535I0VvdpNgP7DbvS0d
perhaps better longer version- 6 min
http://www.youtube.com/watch?v=3SLIzSCt_cg