While he did conduct some experiments, his most significant contributions were in the realm of theoretical physics, where he developed groundbreaking theories that changed our understanding of the universe.

Here are some of his major contributions:

* Special Relativity: This theory revolutionized our understanding of space, time, and gravity. It laid the foundation for the development of nuclear weapons and other technologies.

* General Relativity: This theory extended special relativity to encompass gravity, explaining the bending of light around massive objects and the expansion of the universe.

* Photoelectric Effect: This theory explained how light interacts with matter, earning him the Nobel Prize in Physics in 1921.

* Brownian Motion: This theory explained the random movement of particles suspended in a fluid.

While Einstein's work had practical applications, his primary focus was on developing theories that explained the fundamental workings of the universe. He was a master of abstract thought and mathematical modeling, which allowed him to make profound contributions to our understanding of the physical world.