Letters from our readers.
As I was catching up on my reading at 11 kilometers up, this caught my eye: “one human step would light two 60-watt bulbs for only a second” (“Harvesting Pedestrian Power,” November/December 2007). After doing some scribbling in the margins of TR, I concluded that Thaddeus Jusczyk is boundlessly optimistic about the energy of crowds bounding through his “crowd farm.”
It seems that to get 120 watts per second per step from an “average” airplane passenger weighing 75 kilograms and walking on or near Earth in a gravitational field of 9.8 meters per second squared necessitates delivering 120 newton-meters per step. “Weighing” 735 newtons, the passenger would have to step up 120/735 = 0.163 meters and fall back the same amount with each step. And of course this would be increased by the inverse of the efficiency (let’s say optimistically 70 percent). It would be roughly equivalent to trekking on snowshoes through a foot of soft snow.
While it is encouraging that the mechanics of recovering energy from footfalls are within the state of the art, I doubt Mr. Jusczyk will find “crowds” willing to walk on such a heavily damped sidewalk for very long.
Doc Dougherty, SM ‘68Let
Playa del Rey, CA
The Researchers Respond
Naturally, calculations estimating the energy potential of a crowd’s footsteps would vary greatly depending on the efficiency of the energy capture, the person walking, the damping of the surface, the angle incline, and the nature of the site itself. Our estimates were calculated for a staircase, where a certain amount of damping might be possible, and where the height differential per step would be greater than on level ground.
We readily agree that current technologies have not achieved the efficiency that would make our project immediately feasible. In fact, the Crowd Farm is more a provocation than a promise. We aren’t inventing the technology but looking for new applications for it. We look forward to the continuing advance of energy harnessing and hope we’ve made people think about their physical interactions with their urban environments.
Thaddeus P. Jusczyk and James D. Graham
We were glad to see the photos from the first annual Zesiger Cardboard Boat Regatta (“Sink or Swim,” January/February 2008). Participating in the regatta was a great opportunity for us to apply the engineering knowledge we have gained in classes in a fun and hands-on event. For example, we did a simple buoyancy calculation and determined that if our boat held up structurally, it could support 900 pounds. Assuming that everyone in the boat weighed less than 150 pounds, this gave us a safety factor of at least two. Luckily for us, the calculations were correct, and our boat, Ship Happens, won.
Ellann Cohen ‘08, Rebecca Oman ‘08, and Chensi Ouyang ‘08
Seeking Dramashop Memorabilia
It was great to see the article highlighting the 80th anniversary of MIT’s Dramashop (“Dramatic Oversight,” January/February 2008). As the club’s current president, I was thrilled to meet Dramashop alumnus Louis Rosenblum ‘42, who regaled us with tales of his experiences in the 1930s and 1940s–and showed us his considerable collection of Dramashop memorabilia.
If any other alumni want to share or donate posters, programs, or photographs from Dramashop productions, the current members would love to hear from you. We want to have as complete an archive of our history as possible and can’t do it without you. Please write to us at email@example.com.
Susan Wilson ‘08
MIT’s New Logo
As an artist who is inspired by geometric patterns that appeared in Paleolithic cave paintings, I was delighted by MIT’s new logo from the moment I spotted it in Technology Review in September 2003. Although I had some qualms as to its exact proportions, I immediately noticed that it would fit perfectly among my abstract paintings, many of which are based on the four-by-six grid. To my own surprise, I recently painted it, too, and put it on the wall. As the photo testifies, MIT’s logo is now at home in my gallery.
Motovun, Istria, Croatia
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