JOHN TIERNEY: Why not perpetual progress? “Yes, there are physical limits to what can done with computer chips. But for a century now, each time computer engineers ran into previous physical limits — with the original electro-mechanical machines, with vacuum tubes, with transistors — they jumped to a new technology, and they’re already working on successors to today’s chips. It may seem naive to expect continuing leaps forward, but I think it’s naive to ignore the trend of the past century — or the past 10,000 years.”