What's the most significant advancement made in Physics over that past 100 years?

There is not one invention but many inventions made in Physics in the past 100 years that can be said to be significant.

1. The Big bang model proposed by Georges Lemaitre in 1927. He proposed that all universe came from the explosion of a mass densely concentrated at a single point. Recent discoveries strongly support this model and it is universally accepted now.

2. Discovery of nuclear fission by Otto Hahn in 1938. This process is now used for the generation of nuclear power in nuclear reactors. An atom bomb also works on the same principle.

3. Research in the field of quantum electrodynamics by Richard Feynman.1948.

4.Theory of cosmic inflation of the universe.1981.

5. The accelerated expansion of the universe was discovered in 1998. It showed that a galaxy is receding from a distant observer with a velocity that is increasing with time.

6. Gravitational waves proposed by Albert Einstein in his theory of general relativity were confirmed by the LIGO. It opened up a new field of physics called gravitational wave astronomy.