Time marches on, but Earth is falling behind. The solution again this year is to add a "leap second" as 2005 ticks away, so Earth can catch up with the atomic clocks that have defined time since their unerring accuracy trumped the heavens three decades ago. This will be the first leap second in seven years, and its arrival will be closely watched by physicists and astronomers enmeshed in a prolonged debate over the future of time in a world increasingly dominated by technology. Some experts think the leap second should be abolished because the periodic, but random, adjustment of...