Final answer:
Werner Heisenberg was a German physicist known for his uncertainty principle in quantum mechanics. His theory fits in the early 20th-century timeline of physics.
Step-by-step explanation:
Werner Heisenberg, a German physicist, was one of the pioneers in the development of early quantum mechanics. He is best known for his uncertainty principle, which states that it is impossible to measure both the position and momentum of a particle simultaneously with perfect accuracy. His work changed our understanding of the availability of knowledge and the limitations of our observations in the quantum world.
Heisenberg's theory fits into the timeline of history as a significant development in the early 20th century. His uncertainty principle was introduced in 1929 and had a profound impact on the field of quantum mechanics, challenging classical ideas about the determinacy of particles. Heisenberg's contributions earned him the Nobel Prize in Physics in 1932.