Every age has characteristic inventions that change the world. In the 19th century it was the steam engine and the train. For the 20th, electric and gasoline power, aircraft, nuclear weapons, even ventures into space. Today, the planet is awash with electronic business, chatter and virtual-reality entertainment so brilliant that the division between real and simulated is hard to discern. But one new idea from the 19th century has failed, so far, to enter reality—time travel, using machines to turn the time dimension into a two-way highway. Will it...
Every age has characteristic inventions that change the world. In the 19th century it was the steam engine and the train. For the 20
