At the University of Pennsylvania, Vijay Kumar studies the control and coordination of multi-robot formations. With his team he has built flying quadrotors, small, agile robots that swarm, sense each other, and form ad hoc teams — for construction, surveying disasters and far more.
2012 is a leap year, and it will also have a leap second. A leap second is a one-second adjustment to the Coordinated Universal Time (UTC). It’s an extra second added in to our official timekeeping, with the most recent one being December 31, 2008. The next leap second will be added to the clock on June 30, 2012. At the same time, the International Telecommunications Union (ITU), a United Nations body that governs some global issues related to time, has been contemplating the controversial idea of a leap second. They considered abolishing the practice, but in late January 2012 – with delegates from more than 150 nations meeting in Geneva – the ITU decided to defer a proposal to dump the leap second until their 2015 meeting.
Like the ancients who insisted that all motion in the heavens must be perfect, uniform and unvarying, many of us today assume that the Earth’s rotation – its spin on its axis – is perfectly steady. We learned, correctly, that the sun, moon, stars and planets parade across our sky because the Earth turns. So it is easy to understand why we assume that the Earth’s rotation is precise and unwavering. Yet Earth’s rotation does not stay perfectly steady.