First of all, the technological changes and updates would become more frequent and the use of the internet, cell phone and computers would become widespread.
Fifth, People would learn more about the outer space as the experiment and scientific research on outer space are going on more steadily than ever.
Sixth, the nuclear power would replace the traditional power sources and at the same time many countries would possess the nuclear power and that would always be a threat to the world.
Many people will have chips and mini computers inserted in their heads to hold a huge amount of information and have a quick access to it.
But what will be the most amazing thing in the 21st century is the flights to the outer space and Mars that will be available to all people.