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MIT Students Show How the Inca Leapt Canyons

PCOL writes "When Conquistadors came to Peru from Spain in 1532, they were astonished to see Inca suspension bridges achieve clear spans of at least 150 feet at a time when the longest Roman bridge in Spain had a maximum span of 95 feet. The bridges swayed under the weight of traffic terrifying the Spanish and their horses, even though, as one Spaniard observed, they were almost as "sturdy as the street of Seville." To build the bridges, thick cables were pulled across a river with small ropes and attached to stone abutments on each side. Three of the big cables served as the floor of the bridge, two others served as handrails and pieces of wood were tied to the cable floor before the floor was strewn with branches to give firm footing for beasts of burden. Earlier this year students at MIT built a 70-foot fiber bridge in the style of the Incan Empire. The project used sisal twine from the Yucatan Peninsula and anchored it by wrapping it around massive concrete blocks. The weekend's burst of activity was preceded by 360 hours of rope-twisting as the 50 miles of sisal twine was turned into rope. Working together as a group was part of the exercise. "A third of the time was spent learning to work together," one of the students said. "But after a while, we were banging those cables out.""

21 of 185 comments (clear)

  1. w00t by Zackbass · · Score: 5, Interesting

    Haha, talk about a late story at a completely random time. I was one of the leaders on the project, lots of late nights twisting twine together. If anyone has any questions feel free to ask.

    --
    You gotta find first gear in your giant robot car
    1. Re:w00t by Nimey · · Score: 4, Funny

      If anyone has any questions feel free to ask. Why is a mouse when it spins?
      --
      Hail Eris, full of mischief...

      E pluribus sanguinem
    2. Re:w00t by Zackbass · · Score: 4, Informative

      Oh man, it wasn't pretty. My hands are pretty worn in from working on cars and in machine shops a lot of the time but they were always sore and red after a night of twisting. Sometimes I wore my mechanix gloves, but they don't give the feel really needed to work it fast.

      --
      You gotta find first gear in your giant robot car
    3. Re:w00t by evilviper · · Score: 4, Informative

      Why is a mouse when it spins?


      Because the higher, the fewer.
      --
      Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
    4. Re:w00t by hejish · · Score: 4, Interesting

      How do you get the cable across the wide expanse? arrow + thin rope pulls thicker rope? Did someone have to start on the other side somehow - like from a long trek? These questions went unaddressed.

    5. Re:w00t by russ1337 · · Score: 4, Funny

      Exactly. When I read the title, I thought they'd be delving into how the first guy 'leaped' across the 150ft canyons.... I was thinking they flung a midget inca over the crevase by trebuchet or something... the article did not tell me, so I'm moving forward believing it was midget Inca's and trebuchets.

    6. Re:w00t by Riktov · · Score: 4, Insightful

      Forget shooting rope-laden arrows across wide windy gaps. Just have another person down in the canyon to tie the ends thrown down by both sides.

  2. Science! by proudfoot · · Score: 5, Informative

    People here seem to be missing the point - it isn't that this stuff isn't trivial compared to todays engineering, it is. But it's more revealing about the fact that non-western civilizations had an advanced grasp of the physics/science behind this stuff. They knew how to take advantage of rope tension. A bridge like this isn't so impressive today. It's easy to build. But to come up with the design is the hard part.

    1. Re:Science! by Jarjarthejedi · · Score: 4, Insightful

      Precisely. History has always been extremely biased (the winner writes the books) and tended to show ancient people as stupid compared to us, especially the ancient non-European people (here in the US at least, I'd guess that other countries have similar slants). Yet again we're shown that ancient people had a grasp of the world that is surprisingly advanced, and that non-European cultures were just as advanced even if they didn't use gunpowder or some of the other things the Europeans had.

      Good article, I always enjoy learning about these sorts of things where someone tries to recreate an ancient feat, using authentic technology. They're almost always informative and teach us that we're not so far advanced beyond older cultures, and no one group has ever known the sum knowledge of the world, one group always seems to know more about one thing, and other groups about other things.

      --
      There are two kinds of fool One says 'This is old therefore good' Another says 'This is new therefore better'- Dean Ing
    2. Re:Science! by Volante3192 · · Score: 5, Interesting

      Actually, the engineering of the pyramids is still surprising us; not only was the construction of the pyramid incredible, but the actual quarrying and shaping of the stones is still unsurpassed. Sheets of paper won't fit through the gaps between blocks, and there's no mortar.

      Attempting to build a duplicate pyramid today would still be a massive undertaking that would take years; hardly a trivial task.

    3. Re:Science! by camperdave · · Score: 4, Insightful

      I'm not sure how building a bridge displays knowledge of the science... Trial and error will suffice...

      Um... Trial and error *IS* science.

      --
      When our name is on the back of your car, we're behind you all the way!
    4. Re:Science! by kklein · · Score: 5, Insightful

      Okay, a lot of people are already saying this, but they're not being modded up, and I don't have mod points, so I'll just join in:

      But it's more revealing about the fact that non-western civilizations had an advanced grasp of the physics/science behind this stuff.

      There is absolutely no reason to think the Incas knew anything of the sort, any more than "nature" knows how to fly, because there are birds. It's evolutionary. Ideas that work stick around and propagate. Ideas that don't result in smashed Incas at the bottom of a ravine. Those ideas don't stick around.

      Most good cooks can't tell you the complex series of chemical reactions that result in deliciousness; they just learned via trial, error, and someone showing them what to do.

      How's your understanding of English grammar? Do you know how to diagram sentences down to the morphological level? Do you know how the tense/aspect system works in English? Do you know about semantic features, etc? I do, but I had to go to grad school to learn it. I have, however, been successfully speaking English for at least 31 years!

      Success at any task is not necessarily indication of an understanding of the theory behind it.

      I get so tired of people praising stone-age cultures as though they were so much more advanced than we like to think just because they could pile some damn rocks really high or, given several millennia of sky-watching, could notice patterns in the night sky. None of this is special and none of it is indicative of the kind of detailed, theoretical knowledge that the modern, largely Western, world has developed and is continuing to develop. If these filthy savages had been so great, they would have colonized us and our stupid hunter-gatherer lifestyles would have been destroyed (which, of course, did happen, when the Roman Empire came all the way up to the hellhole that was the British Isles, from whence my family originally hails).

      It's just simple evolution. Useful ideas that strengthen communities survive, others do not. That doesn't mean that the willful genocide of various primitive peoples the Europeans ran into was the "right" thing to do, but the destruction of their cultures and the re-appropriation of their resources was inevitable. I have no "white guilt," and I'm not sorry that I grew up on land my ancestors stole from people who had no written language, lived in animal-skin huts, and hadn't even developed farming. I don't feel any need to pretend any of these cultures were anything more than Paleo- to Neolithic cultures lost in time while the rest of the world (i.e. the cultures of Eurasia, each leading during different epochs) went on without them.

      Is the ability to build such bridges cool? Hell, yes! But it is not particularly special.

  3. Re:w00t-A close team. by Zackbass · · Score: 5, Informative

    Not on purpose as far as I remember, but when the rope reached a certain size it couldn't just be reeled up by hand anymore and we had to have two people act as a reel, twisting the rope around themselves as they walked down the hall. Eventually they'd be tied right up against each other with something like 70lb of rope around them.

    --
    You gotta find first gear in your giant robot car
  4. Re:Wise beyound years. by ozmanjusri · · Score: 5, Funny
    ancient men weren't idiots

    According to Mayan glyphs found carved in stones near one of the bridges, Bolontiku, Ixzaluoh and Ac Yanto were in fact idiots. Ixzaluoh in particular, was believed to have had difficulty finding his ass, despite using both hands.

    --
    "I've got more toys than Teruhisa Kitahara."
  5. my thoughts when i saw it by wrigglywrollypolary · · Score: 4, Interesting

    I was walking around campus one day and saw the cement pillars going up. They were BIG concrete boxes, about 4 stacked up taller than me and about 2-3 feet on a side. I'm not sure what happened to that concrete but it seemed wasteful to make _just_ rectangular prisms. No offense, especially since I'm a 'utility-focused' engineer, myself, but I did think-- wow, these are harsh. It might have been fun to paint, or sculpt them (before being set, or with plaster afterwards), with Incan designs or information about the construction process.

    The rope bridge itself looked fun to walk on, but it had a sign saying no trespass. That sign was up the whole time the bridge was there, though it is possible people might have walked around the bridge for fun and jumped around to see how it swayed and bubbled. At that point the bridge might have been up a while and losing tension and so the sides of the shallow creek interfered with the hanging bridge aspect.

    It's great to see thought provoking structures go up around campus. Rock on.

    1. Re:my thoughts when i saw it by Zackbass · · Score: 4, Informative

      The deal with the concrete blocks was that they were provided to us quite cheaply by one of the companies doing construction at Sloan. They brought them in, put them where we told them to, and took them back when we were done so we couldn't do much to them. Without them stacked up like that it would have been horribly difficult to get the normal force required on the brick surrounding the Stata center (which of course we couldn't even think about touching).

      About the sign, we assumed it would be wholly ignored. We needed it to satisfy the safety office I think (I wasn't involved with that end of the planning much).

      --
      You gotta find first gear in your giant robot car
  6. The traditional bridge builders still do this by psychgeek · · Score: 5, Informative

    The descendants of the original bridge builders still do this each year at one of the original sites, using techniques handed down by previous generations. Photos here:
    http://en.wikipedia.org/wiki/Inca_rope_bridge#Renewing_the_last_bridge

  7. Re:w00t-A close team. by mollymoo · · Score: 4, Funny

    Not on purpose as far as I remember, but when the rope reached a certain size it couldn't just be reeled up by hand anymore and we had to have two people act as a reel, twisting the rope around themselves as they walked down the hall. Eventually they'd be tied right up against each other with something like 70lb of rope around them.

    In the light of that, I have three questions:
    Are you doing it again?
    Do you need volunteers?
    Are the rest of the volunteers likely to be hot, naked chicks?

    I have to admit that if the answer to the third one is "no" I may not be very interested.

    --
    Chernobyl 'not a wildlife haven' - BBC News
  8. Re:Disppointed and not what I expected by value_added · · Score: 4, Informative

    Maybe describing it in a context that any Slashdotter would understand might help.

    Aztecs:

    I, for one, welcome our Mesoamerican, Cortez-hating, Virgin of Guadalupe-worshiping, human-sacrificing, maize-and-bean-growing, empire-building Mexica overlords.

    Incas:

    I, for one, welcome our pre-Columbian, sun-loving-with-bare-titicas, Conquistador-fighting, Machu-Picchu coca leaf-chewing, Andean-whistling and bridge-building overlords.

  9. Scoffing at the Ancients by handy_vandal · · Score: 4, Funny

    So the moral of the lesson is that ancient men weren't idiots.

    "We tend to scoff at the beliefs of the ancients. But we can't scoff at them personally, to their faces, and this is what annoys me." - Jack Handey

    -kgj

    --
    -kgj
  10. Re:Disppointed and not what I expected by bogjobber · · Score: 4, Informative

    The Maya hadn't died out. Quite the contrary, there were (and are) huge populations of Mayan people in Yucatan and Guatemala. They just weren't the dominant civilization at the time the Spanish arrived. There were probably about a million "Mayans" (exact numbers being impossible to come by for many reasons) while Central Mexico may have had as many as 25 million people (most estimates put it in the 10-15 million range).