Catch a Falling Star

A hundred thousand years from now, it was discovered that a star was approaching the world on a collision course. Its discoverer, Creohan, figured there might be time to save the world if he could arouse everyone to the danger.
But the Earth had become a strange and kaleidoscopic place in that distant era. Too many empires had risen and fallen, too many cultures had spread their shattered fragments across a planet whose very maps had long since been forgotten. People were too busy with their own private dreams to pay attention to one more new alarm.
The story Creohan's effort to Catch a Falling Star is one of John Brunner's most colourful science-fiction concepts.