A MORE sober look at the future comes from Michio Kaku, who teaches theoretical physics at the City College of New York. Setting out to chart the direction technological progress will take in the 21st century, Mr Kaku is aware that history is replete with unfulfilled prophecies. To avoid his joining their ranks, he adopts a cautious three-pronged strategy.

First, he rejects any ideas that are at odds with what is currently understood about the fundamental laws of physics. No teleportation, wormholes or flitting between dimensions, then, at least until 2100, when Mr Kaku's story ends.

Second, he dismisses innovations which, though possible in theory, go against the grain of human nature. Psychologically, man has changed precious little from the savannah-roaming brute...