The Sciences Castles in the Air The attacks of 9/11 supposedly ended the age of the skyscraper. A decade on we're building more than ever By Mark Lamster THIS IS A PREVIEW. Buy this digital issue or subscribe to access the full article. Already a subscriber or purchased this issue? Sign In IWAN BAAN On that cool blue morning 10 years ago when everything changed, Les Robertson was half a world away, hosting a dinner at a Hong Kong restaurant. The rattling of cell phones left on the table—“a detestable habit”—was the first indication that something had struck one of the Twin Towers. Robertson, the revered engineer responsible for their structural design, was at first unconcerned. “I just assumed that a helicopter had run into the Trade Center,” he said recently, speaking from his 47th-floor office, which looks out over Ground Zero. Such an event, unfortunate as it might have been, was well within the tolerances for which the towers were designed. A few minutes later, however, when those cell phones started buzzing once more with news of a second crash, he realized it was “quite another thing again” and excused himself to watch the unfolding events from a hotel room. THIS IS A PREVIEW. Buy this digital issue or subscribe to access the full article. Already a subscriber or purchased this issue? Sign In Buy Digital Issue $7.99 Add To Cart Print + DigitalAll Access $99.99 Subscribe ADVERTISEMENT Scientific American is a trademark of Scientific American, Inc., used with permission © 2015 Scientific American, a Division of Nature America, Inc. All Rights Reserved.