Karl Ernst Ludwig Marx Planck, better known as Max Planck[2] (April 23, 1858 – October 4, 1947) was a German physicist. He is considered to be the founder of quantum theory, and one of the most important physicists of the twentieth century. Planck came from a traditional, intellectual family. His paternal great-grandfather and grandfather were both theology professors in Göttingen, his father was a law professor in Kiel and Munich, and his paternal uncle was a judge.