To conclude this piece I come to my third and last heresy. My third heresy says that the United States has less than a century left of its turn as top nation. Since the modern nation-state was invented around the year 1500, a succession of countries have taken turns at being top nation, first Spain, then France, Britain, America. Each turn lasted about 150 years. Ours began in 1920, so it should end about 2070. The reason why each top nation’s turn comes to an end is that the top nation becomes over-extended, militarily, economically and politically. Greater and greater efforts are required to maintain the number one position. Finally the over-extension becomes so extreme that the structure collapses. Already we can see in the American posture today some clear symptoms of over-extension. Who will be the next top nation? China is the obvious candidate. After that it might be India or Brazil. We should be asking ourselves, not how to live in an America-dominated world, but how to prepare for a world that is not America-dominated. That may be the most important problem for the next generation of Americans to solve. How does a people that thinks of itself as number one yield gracefully to become number two? --Freeman Dyson, HERETICAL THOUGHTS ABOUT SCIENCE AND SOCIETY