Thought Experiments and a Pencil

Albert Einstein was born on March 14, 1879, in Ulm, Germany. In 1905, while working as a patent clerk, he published four papers that restructured physics. One proved light behaves as particles. Another confirmed atoms exist. The third introduced special relativity. The fourth gave us E=mc2, linking mass and energy. His tools were thought, mathematics, and intuition for how the universe should behave.

Special relativity emerged from a question he had asked since sixteen: what would you see riding alongside a beam of light? Einstein concluded that time and space are relative. E=mc2 was a byproduct. If mass and energy are equivalent, matter is highly concentrated energy. The equation was theoretical when written. It became practical when physicists realized it described what happens inside atomic nuclei.

illustration of spacetime curvature, as predicted by einstein's general theory of relativity. source: wikimedia commons

He spent the next decade developing general relativity. Massive objects curve spacetime, and gravity is the result. A planet orbits a star because the star warps space. General relativity predicted light bending around massive objects, the expansion of the universe, and black holes. All confirmed. He did not like quantum mechanics, famously saying God does not play dice. He was wrong.

Einstein became a public figure in 1919 when a solar eclipse confirmed his predictions. He used fame to advocate for pacifism and civil rights. When the Nazis took power, he left Germany and settled in Princeton, searching for a unified theory he never found. His legacy is not just equations but method. He trusted intuition and symmetry, willing to follow reasoning even when it led somewhere absurd. That willingness separates transformative work from incremental refinement.