: Past, Present & Future.
The way science has evolved, especially since Newton and then the present scenario.
The rate at which we are going, Moore's Law says our laptops will start calculating at the speed of an average human brain by 2025. Which means laptop can do anything a human can do, the birth of AI.
In the field of space exploration, the future is the Solar System, starting with Mars.
Medicine: All the research being done on genetic modifications to increase the life span of human beings, making 100 the new 60 (search for Peter Diamandis for more info on this).
Then the topics mentioned by other answers.
This would cover the body of the speech.
For the conclusion, end by saying that the future is bright as always. With the way we are going, I am positive that the day is not far when life, the way we see it, will b