Robert Silverberg 
Stepsons of Terra 

It had been five hundred years since the distant Terran Colony of Corwin had communicated with Earth. But now Corwin was threatened by the indomitable warriors of Klodni and the peaceful planet desperately needed help. Baird Ewing was the ambassador chosen by his people to find that help and save Corwin from destruction.But Earth had changed . . .Ewing found a decadent world of worthless pleasure-seekers devoid of hope and incapable of help. The only remaining vestige of the old world on Earth was to be found in the College of Abstract Science. It was Ewing’s last hope. If he failed it was the end of the line for him, Corwin – and the galaxy.First published in 1958.